Key properties of inorganic thermoelectric materials—tables (version 1)

• Weighted mobility, µ_w (cm² V⁻¹ s⁻¹)
• Hall mobility, μ_H (cm² V⁻¹ s⁻¹)
• Intrinsic mobility, µ_o (cm² V⁻¹ s⁻¹)
• Lattice thermal conductivity, κ_L (W m⁻¹ K⁻¹)
• Seebeck coefficient, S (µV K⁻¹)
• Electrical conductivity, σ (Ω⁻¹ cm⁻¹)
• Thermoelectric quality factor, zT
• Bandgap, E_g (eV)
• Effective mass, m_s* (m_e)
• Static dielectric constant/relative permittivity, _r
• Thermal conductivity, κ (W m⁻¹ K⁻¹)
• Carrier concentration, n (cm⁻³)

All the parameters contributing to zT (equation (1)), i.e. Seebeck coefficient, electrical resistivity and thermal conductivity vary significantly with charge carrier concentration in contrasting ways. Achieving high zT in a material typically requires optimization of the charge-carrier concentration. As the charge-carrier concentration can be controlled by intrinsic defects (such as vacancies and interstitials) as well as extrinsic dopants (impurities), then the search for (or comparison between) good thermoelectric materials is really a search for a material with the highest potential for high zT assuming it can be optimally doped. This potential high zT is determined by the thermoelectric quality factor B [5, 6], defined in equation (3), which at a particular temperature is directly proportional to zT [7]:

$$\begin{equation}B = \frac{8\pi {k_{\text{B}}}(2{m_{\text{e}}})^{3/2}}{3{eh}^3}({k_{\text{B}}}T)^{5/2}\frac{\mu_{\text{W}}}{\kappa_{\text{L}}}.\end{equation} \tag{ 3 }$$

Here k_B, m_e, e and h are the Boltzmann constant, electron rest mass, electron charge and Planck's constant respectively; thus except for temperature, the quality factor is proportional to μ_w/κ_L. This indicates the quality of a thermoelectric material can be divided into the quality of its electronic properties, given by the weighted mobility μ_w, and the quality of its thermal properties, given by the lattice thermal conductivity κ_L [8]. Hence, improvements in 'electronic properties' can be defined as a higher μ_w , while improved 'thermal properties' means a lower κ_L for all material changes other than doping.

Several types of mobility are reported in the literature, most commonly the Hall mobility, intrinsic mobility, and weighted mobility. The Hall mobility, μ_H, is directly obtained from measurements of the Hall coefficient and resistivity. The intrinsic mobility, μ_o, is usually calculated using a single parabolic band (SPB) model, and can be viewed as an estimate of μ_H at the limit of very low carrier concentration (i.e. intrinsic behavior). Thus, for a given material and temperature, μ_o > μ_H. Hall mobility (μ_H) is reported for over half the material families in the compilation and intrinsic mobility (μ_o) for most of the remainder; this reflects the available data in the source publications.

Finally, the weighted mobility, μ_W, is generally described as the drift mobility, μ, weighted by the density-of-states effective mass (${m_{\text{DOS}}^*}$). Equation (4) further relates μ_w to the effective valley degeneracy (N_V) and inertial effective mass, ${m_{\text{I}}^*}$ [9]:

$$\begin{equation}\mu_{\text{w}} = \mu \left(\frac{m_{\text{DOS}}^*}{m_{\text{e}}}\right)^{3/2}\ \sim\ \frac{N_{\text{V}}}{m_{\text{I}}^*}.\end{equation} \tag{ 4 }$$

High weighted mobility is achieved in materials with lighter inertial effective mass m_I (which is equal to the single band effective mass ${m_{\text{b}}^*}$ for an isotropic band) and/or higher effective valley degeneracy. The advantage of comparing weighted mobility values among various materials is that it does not require Hall measurements (and is therefore widely accessible) and it combines two different parameters (${m_{\text{DOS}}^*}$ and μ) that should be maximized to increase thermoelectric performance.

The weighted mobility has been calculated for all material families in this paper using equation (5), where S and ρ are the experimental values of Seebeck coefficient and electrical resistivity, respectively, at temperature T [7]:

$$\begin{equation} \mu_{\textrm{w}} = \frac{331}{\rho} \left(\frac{\textrm{T}}{300}\right)^{-3/2}\left[\frac{\exp\left[\frac{|S|}{\textrm{k}_\textrm{B}/\textrm{e}}-2\right]}{1+\exp\left[-5\left(\frac{|S|}{\textrm{k}_\textrm{B}/\textrm{e}}-1\right)\right]} + \frac{\frac{3}{\pi^2}\frac{|S|}{\textrm{k}_\textrm{B}/\textrm{e}}}{1+\exp\left[5+\left(\frac{|S|}{\textrm{k}_\textrm{B}/\textrm{e}}-1\right)\right]}\right]. \end{equation} \tag{ 5 }$$

Tanmoy Ghosh¹ and Kanishka Biswas^1,2,3

Metal tellurides are among the most extensively studied families of thermoelectric materials for near room temperature to mid-temperature thermoelectric power generation. Particularly, the IV–VI semiconductors like GeTe, SnTe, and PbTe and tetradymites Bi₂Te₃-based thermoelectric materials have attracted wide attention in the community. Many of the modern-day approaches of improving thermoelectric performance, based on either electronic structure modulation or phonon scattering manipulation strategies, were first demonstrated on these materials. These families of materials, such as (GeTe)_x (AgSbTe₂)_100−x -based TAGS-x and Bi₂Te₃-based materials are some of the most widely used thermoelectrics for commercial applications. Figure 2 exhibits the maximum thermoelectric figure of merit, zT for a range of current metal telluride thermoelectric materials. Here, we outline the status of these metal telluride-based thermoelectric materials, the challenges, and recent progress. Typical thermoelectric performance-related parameters and zT values for various Te-based thermoelectric materials are listed in table 1.

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Table 1. Tellurides thermoelectric properties.

Material	T (K)	µw (cm2 V−1 s−1)	κL (W m−1 K−1) a	S (µV K−1)	σ (Ω−1 cm−1)	zT	Eg (eV)	µ0 (cm2 V−1 s−1)	ms a (me)	r or (0)	References
Bix Sb2−x Te3	300	479.5	0.6	186	1242	1.2	—	—	—	—	[42]
Bix Sb2−x Te3	373	318.4	0.44	212	845	1.4	—	—	—	—	[42]
Bi0.5Sb1.5Te3	320	429.4	0.33	241	647	1.86	—	—	—	—	[45]
Bi0.3Sb1.625In0.075Te3	300	339.6	0.61	185	890	0.75	0.12	—	1.6	—	[69]
Bi0.3Sb1.625In0.075Te3	500	164.6	1.09 (kT)	220	618	1.4	—	—	—	—	[69]
Bi0.5Sb1.495Cu0.005Te3	300	363.5	0.34	154	1371	0.97	—	—	—	—	[70]
Bi0.5Sb1.495Cu0.005Te3	450	152.6	0.31	201	610	1.4	—	—	—	—	[70]
Bi0.5Sb1.5Te3	350	332.4	0.65	237	600	1.24	—	—	—	—	[71]
Zn0.015Bi0.46Sb1.54Te3.015	300	465.6	0.52	185	1220	1.14	—	—	1.03	—	[43]
Zn0.015Bi0.46Sb1.54Te3.015	373	305.7	0.5	208	850	1.4	—	—	—	—	[43]
Bi0.4Sb1.6Te3	323	458.7	1.03 (kT)	232	778	1.38	0.25	320	1.4	—	[72]
Bi2Te2.7Se0.3	300	389.5	0.7	−190	963	0.9	—	—	—	—	[73]
Bi2Te2.7Se0.3	398	221.2	1.14 (kT)	−209	670	1.04	—	—	—	—	[73]
Bi2Te2S	300	159.9	1.01 (kT)	−148	648	0.4	0.2	—	—	—	[74]
Bi2Te2S	573	52.8	0.93(kT)	−171	430	0.8	—	—	—	—	[74]
K0.06Bi2Te3.18	300	455.4	0.66	−180	1265	0.98	—	—	—	—	[48]
K0.06Bi2Te3.18	350	359.4	0.66	−197	1032	1.1	—	—	—	—	[48]
Bi2Te2.7Se0.3	300	182.7	0.44	−167	591	0.68	0.25	—	0.76	—	[47]
Bi2Te2.7Se0.3	480	105.3	0.36	−198	480	1.23	—	—	—	—	[47]
Bi1.8Sb0.2Te2.7Se0.3+15%Te	300	398.8	0.41	−171	1231	1	—	100	1.7	—	[46]
Bi1.8Sb0.2Te2.7Se0.3+15%Te	425	215.6	0.38	−198	819	1.4	—	—	—	—	[46]
GeTe	300	310.2	2.62	32	8069	0.03	0.2	—	1.43	—	[75]
GeTe	673	148.4	0.74	137	2307	0.93	—	—	—	—	[75]
Ge0.87Pb0.13Te	723	115.9	1.2 (kT)	196	1000	2.27	—	—	—	—	[76]
Ge0.87Pb0.13Te-5%Bi2Te3	373	155.5	1.05 (kT)	130	1087	0.66	—	75	—	—	[77]
Ge0.87Pb0.13Te-5%Bi2Te3	690	86.5	0.78 (kT)	243	403	2.1	—	—	—	—	[77]
(CoGe2)0.2(GeTe)17Sb2Te3	723	135.9	0.64	258	571	1.9	—	—	—	—	[78]
Ge0.9Sb0.1Te	300	222.2	1.42	107	1503	0.22	0.08	—	—	—	[75]
Ge0.9Sb0.1Te	725	179	1.15	256	773	1.85	—	—	—	—	[75]
Ge0.94Bi0.06Te	300	236.9	1.13	71	2680	0.14	0.08	—	—	—	[79]
Ge0.94Bi0.06Te	725	130.5	1.2	217	886	1.3	—	—	—	—	[79]
Ge0.85Bi0.05Sb0.1Te	300	159.7	0.48	130	805	0.47	0.08	—	2.44	—	[18]
Ge0.85Bi0.05Sb0.1Te	725	128.3	0.65	232	732	1.8	—	—	—	—	[18]
Ge0.9Sb0.1Te0.9Se0.05S0.05	300	172.5	0.96	148	699	0.29	—	—	—	—	[80]
Ge0.9Sb0.1Te0.9Se0.05S0.05	630	191	0.65	260	638	2.1	—	—	—	—	[80]
Ge0.9Cd0.05Bi0.05Te	300	205.6	1.06	105	1428	0.32	—	43	1.7	—	[21]
Ge0.9Cd0.05Bi0.05Te	650	149.7	0.48	232	725	2.23	—	—	—	—	[21]
Ge0.89Sb0.1In0.01Te	300	167.7	0.73	192	405	0.4	—	—	3.8	—	[32]
Ge0.89Sb0.1In0.01Te	780	99.9	0.52	245	547	2.3	—	—	6.2	—	[32]
Ge0.86Pb0.1Bi0.04Te	300	243.1	0.63	138	1111	0.55	—	69	1.94	—	[34]
Ge0.86Pb0.1Bi0.04Te	600	151.7	0.49	282	365	2.4	—	7	5.92	—	[34]
Ge0.86Sb0.1Zn0.04Te	300	183.5	0.74	157	668	0.46	—	24	2.8	—	[20]
Ge0.86Sb0.1Zn0.04Te	780	109.3	0.55	235	672	2.2	—	—	—	—	[20]
Ge0.93In0.01Bi0.06Te	300	233.8	0.46	87	2082	0.33	0.09	—	1.9	—	[29]
Ge0.93In0.01Bi0.06Te	723	212.5	0.72	246	1026	2.1	—	—	—	—	[29]
(GeTe)0.8(AgBiSe2)0.2	300	91.7	0.28	242	124	0.63	—	—	—	—	[36]
(GeTe)0.8(AgBiSe2)0.2	467	87.7	0.32	279	150	1.3	—	—	—	—	[36]
(Ge0.9Sb0.1Te)0.95(SnSe)0.025(SnS)0.025	300	129.4	0.27	86	1169	0.26	—	—	—	—	[81]
(Ge0.9Sb0.1Te)0.95(SnSe)0.025(SnS)0.025	710	97.1	0.32	206	726	1.9	—	—	—	—	[81]
Ge0.87Sn0.05Sb0.08Te	300	173.4	0.92	89	1501	0.25	—	62	1.57	—	[35]
Ge0.87Sn0.05Sb0.08Te	735	125.3	0.53	205	998	2.2	—	—	3.73	—	[35]
(GeTe)0.95(Sb2Te3)0.05	323	204.8	1.44 (kT)	115	1394	0.4	—	—	—	—	[10]
(GeTe)0.95(Sb2Te3)0.05	720	136.5	1.19 (kT)	217	917	2.7	—	—	—	—	[10]
(GeTe)0.5(AgBiSe1.995Br0.005)0.5	300	15.7	0.21	−149	63	0.15	0.36	—	—	—	[36]
(GeTe)0.5(AgBiSe1.995Br0.005)0.5	500	16.2	0.19	−167	113	0.6	—	—	—	—	[36]
SnTe	300	188.5	2.88	19	8261	—	—	—	—	—	[82]
SnTe	710	58.1	1.06	91	1779	0.29	—	—	—	—	[82]
Sn0.9975In0.0025Te	300	260.8	1.61	50	4300	0.09	0.18	—	—	—	[16]
Sn0.9975In0.0025Te	873	45	0.88	162	767	1.1	—	—	—	—	[16]
SnCd0.03Te-2%CdS	300	130.8	1.31	47	2300	0.06	—	—	—	—	[24]
SnCd0.03Te-2%CdS	873	40.6	0.63	205	419	1.3	—	—	—	—	[24]
Sn0.985In0.015Te0.85Se0.15	300	136.4	1.28	66	1674	0.09	—	—	—	—	[83]
Sn0.985In0.015Te0.85Se0.15	860	43.2	1.26	172	639	0.8	—	—	—	—	[83]
Sn0.94Mg0.09Te	300	131.6	2.72	35	3126	—	—	—	0.69	—	[23]
Sn0.94Mg0.09Te	860	70.6	0.79	174	1021	1.2	—	—	—	—	[23]
Sn0.98Bi0.02Te-3%HgTe	300	229.8	1.13	67	2774	0.13	—	—	—	—	[25]
Sn0.98Bi0.02Te-3%HgTe	910	59.1	0.66	182	847	1.35	—	—	—	—	[25]
Sn0.97In0.015Cd0.015Te-3%CdS	300	132.7	1.64	92	1101	0.13	—	—	—	—	[26]
Sn0.97In0.015Cd0.015Te-3%CdS	923	44	0.59	196	548	1.4	—	—	—	—	[26]
Sn0.94Ca0.09Te	325	257.6	1	44	5466	0.2	—	—	0.35	—	[84]
Sn0.94Ca0.09Te	873	56.9	0.79	185	740	1.35	—	—	—	—	[84]
Sn0.97Bi0.03Te-3%SrTe	300	289.4	1.56	82	2770	0.17	—	—	—	—	[85]
Sn0.97Bi0.03Te-3%SrTe	823	47.4	0.86	173	649	1.2	—	—	—	—	[85]
Sn0.85Sb0.15Te	300	150.9	0.67	33	3806	—	—	—	—	—	[82]
Sn0.85Sb0.15Te	800	56.2		151	956	1	—	—	—	—	[82]
SnAg0.025In0.025Te1.05	300	239	2.39	98	1825	0.08	—	—	—	—	[27]
SnAg0.025In0.025Te1.05	856	69.7	1.17	167	1087	1	—	—	—	—	[27]
Sn0.97Bi0.03Te-3%PbTe	300	157.1	1.15	27	4847	—	—	—	—	—	[86]
Sn0.97Bi0.03Te-3%PbTe	900	54.2	1.1	197	642	1.1	—	—	—	—	[86]
(Sn0.89Mn0.14Te)(Cu2Te)0.05	300	102.6	1.72	45	1886	0.06	—	—	—	—	[12]
(Sn0.89Mn0.14Te)(Cu2Te)0.05	920	34.4	0.51	200	407	1.6	—	—	—	—	[12]
Sn0.915Mn0.11In0.005Te	300	106.8	1.64	117	634	0.13	—	—	—	—	[87]
Sn0.915Mn0.11In0.005Te	823	47.6	0.92	237	310	1.15	—	—	—	—	[87]
(Sn0.91Mg0.12Te)(Cu2Te)0.05	300	138.9	1.23	28	4132	—	—	—	—	—	[88]
(Sn0.91Mg0.12Te)(Cu2Te)0.05	900	32.7	0.55	198	383	1.4	—	—	—	—	[88]
Sn0.57Sb0.13Ge0.3Te	300	166	0.48	67	2004	0.16	—	—	—	—	[13]
Sn0.57Sb0.13Ge0.3Te	721	77.8	0.3	174	864	1.6	—	—	—	—	[13]
Sn0.83Ag0.03Mn0.17Te	300	148	1.64	46	2669	0.05	—	—	—	—	[30]
Sn0.83Ag0.03Mn0.17Te	865	55	0.3	164	908	1.45	—	—	—	—	[30]
Sb2Te3(Sn0.996Re0.004Te)8	325	190.8	0.72	84	2000	0.2	—	—	—	—	[89]
Sb2Te3(Sn0.996Re0.004Te)8	773	77.1	0.48	183	855	1.4	—	—	—	—	[89]
Sn1.03Te0.85Se0.075S0.075-2%Ag-2%In	300	162.6	1.21	90	1387	0.16	—	—	—	—	[90]
Sn1.03Te0.85Se0.075S0.075-2%Ag-2%In	854	62	0.6	182	808	1.3	—	—	—	—	[90]
Na0.95Pb20SbTe22	300	190.6	0.74	94	1538	0.25				—	[91]
Na0.95Pb20SbTe22	650	126	0.55	330	196	1.7	—	—	—	—	[91]
Pb0.98Tl0.02Te	300	93.2	2.17 (kT)	137	431	0.1	—	—	0.93	—	[14]
Pb0.98Tl0.02Te	773	87.3	0.95 (kT)	332	172	1.5	—	—	—	—	[14]
PbTe-12%PbS-2%Na	315	136	1.61	69	1710	0.09	—	—	—	—	[92]
PbTe-12%PbS-2%Na	800	75.6	0.73	263	349	1.8	—	—	—	—	[92]
PbTe-1%Na2Te-6%CaTe	300	179.4	1.32	65	2239	0.09	0.26	—	—	—	[93]
PbTe-1%Na2Te-6%CaTe	765	66.6	0.48	259	301	1.5	—	—	—	—	[93]
PbTe0.85Se0.15-2%Na	300	147.2	1.41	50	2427	0.06	—	—	—	—	[15]
PbTe0.85Se0.15-2%Na	850	59.7	0.52	222	485	1.8	—	—	—	—	[15]
MgxPb1−x Te:Na(9E19) b	300	197.1	1.73	105	1369	0.19	—	—	—	—	[94]
MgxPb1−x Te:Na(9E19) b	725	92.1	0.64	269	342	1.7	—	—	—	—	[94]
PbTe:Na(9E19) b	300	216.2	2.05	62	2840	0.1	—	—	—	—	[95]
PbTe:Na(9E19) b	750	87.5	0.8	270	338	1.4	—	—	—	—	[95]
Pb0.96Mn0.04Te:Na	300	190.4	1.33	101	1396	0.2	0.38	—	—	—	[96]
Pb0.96Mn0.04Te:Na	700	86	0.64	263	325	1.6	—	—	—	—	[96]
PbTe-4%SrTe-2%Na	300	145.1	1.96	79	1452	0.09	—	—	—	—	[28]
PbTe-4%SrTe-2%Na	915	64.8	0.52	281	297	2.2	—	—	—	—	[28]
K0.02Pb0.98Te0.75Se0.25	300	98.4	1.49	53	1526	0.06	—	—	—	—	[97]
K0.02Pb0.98Te0.75Se0.25	773	78.5	0.8	312	195	1.6	—	—	—	—	[97]
PbTe-2%MgTe-2%Na2Te	300	197.9	2.05	67	2388	0.1	—	—	—	—	[98]
PbTe-2%MgTe-2%Na2Te	780	76.8	0.74	250	397	1.6	—	—	—	—	[98]
Pb0.98Na0.02Te-6%MgTe	300	175.3	1.73	110	1140	0.16	0.39	—	1.18	—	[99]
Pb0.98Na0.02Te-6%MgTe	823	74.6	0.53	295	248	2	—	—	—	—	[99]
PbTe0.7S0.3-2.5%K	300	127	0.64	70	1460	0.14	—	—	—	—	[100]
PbTe0.7S0.3-2.5%K	923	42.7	0.37	299	161	2.2	—	—	—	—	[100]
(PbTe)0.86(PbSe)0.07(PbS)0.07-2% Na	300	163.3		69	1908	0.1	0.28	—	—	—	[101]
(PbTe)0.86(PbSe)0.07(PbS)0.07-2% Na	823	82.7	0.61	265	389	2	—	—	—	—	[101]
Pb0.98Na0.02Te-8%SrTe	300	242.6	1.7	91	2041	0.18	0.34	—	1.37	—	[102]
Pb0.98Na0.02Te-8%SrTe	923	80.9	0.57	294	323	2.5		—	—	—	[102]
Pb0.953Na0.04Ge0.007Te	300	251.7	2.15	69	2941	0.1	0.4	—	0.8	—	[103]
Pb0.953Na0.04Ge0.007Te	805	89.5	0.67	263	417	1.9	—	—	—	—	[103]
Na0.03Eu0.03Sn0.02Pb0.92Te	300	88.2	0.87	104	621	0.14	—	—	1.6	—	[11]
Na0.03Eu0.03Sn0.02Pb0.92Te	850	62.9	0.42	273	283	2.57	—	—	—	—	[11]
PbTe-1%CdTe-0.055%PbI2	300	330.5	0.89	−88	2901	0.21	0.3		—	—	[104]
PbTe-1%CdTe-0.055%PbI2	720	52.6	0.5	−225	322	1.2	—	—	—	—	[104]
PbTe0.9988I0.0012	300	364.2	1.53	−83	3436	0.27	—	—	0.25	—	[105]
PbTe0.9988I0.0012	723	74.4	0.78	−206	571	1.4	—	—	—	—	[105]
PbTe:I(1.8E19) b	300	392.8	3.32 (kT)	−81	3816	0.22	—	1120	0.25	—	[106]
PbTe:I(1.8E19) b	725			−212		1.39	—	—	—	—	[106]
PbTe-4%InSb	323	78	2.25	−132	428	0.09	—	—	—	—	[40]
PbTe-4%InSb	773	56	0.25	−205	484	1.83	—	—	—	—	[40]
PbTe-4%MnTe	300	171	1.15	−88	1500	0.15	0.34	—	0.4	—	[39]
PbTe-4%MnTe	773	60	0.53	−238	353	1.6		—	—	—	[39]
Pb0.9965In0.0035Te0.996I0.004	300	301.5	1.33	−140	1345	0.4	—	—	0.4	—	[37]
Pb0.9965In0.0035Te0.996I0.004	773	56.9	0.7	−224	392	1.4	—	—	—	—	[37]
(Pb0.93Sn0.07)(Te0.93Se0.07)	300	152.8	1.35	−54	2324	0.08	—	—	0.31	—	[107]
(Pb0.93Sn0.07)(Te0.93Se0.07)	773	47.5	0.6	−199	437	1.4	—	—	—	—	[107]
Pb0.98Ga0.02Te-5%GeTe	300	330.2	1.13	−222	563	0.59	—	—	0.4	—	[38]
Pb0.98Ga0.02Te-5%GeTe	673	86.4	0.66	−287	233	1.47	—	—	—	—	[38]
AgSbTe2	300	137.4	0.5	279	121	0.55	—	—	—	—	[64]
AgSbTe2	573	58.5	0.5	328	77	0.89	—	—	—	—	[64]
AgSb0.96Zn0.04Te2	300	107.9	0.52	234	160	0.56	—	—	2.65	—	[108]
AgSb0.96Zn0.04Te2	585	96.5	0.35	289	206	1.9	—	—	—	—	[108]
AgSbTe1.85Se0.15	300	84.2	0.37	203	179	0.53	—	20	2.32	—	[109]
AgSbTe1.85Se0.15	573	92	0.29	309	151	2.1	—	4	3.38	—	[109]
AgSb0.94Cd0.06Te2	300	174.4	0.15	248	220	1.5	—	—	—	—	[64]
AgSb0.94Cd0.06Te2	573	92.6	0.17	265	253	2.6	—	—	—	—	[64]
MnTe	300	14.1	1.18	463	1.47	—	0.82		7	—	[110]
MnTe	900	17.7	0.67	302	62	0.67	—	—	—	—	[110]
Mn0.98Na0.02Te	300	51.8	0.82	192	125	0.15	—	—	7.7	—	[110]
Mn0.98Na0.02Te	900	19.7	0.58	270	100	0.89	—	—	—	—	[110]
MnTe+0.5%Na2S	300	79.4	1.56	185	208	0.1	—	—	—	—	[49]
MnTe+0.5%Na2S	873	25.9	0.56	267	130	1.09	—	—	—	—	[49]
MnTe+3%Li	923	20.5	0.9 (kT)	208	222	1	—	—	1.05	—	[51]
Mn1.06Te+2%SnTe	323	—	1.48	522	—	—	0.84	—	2.69	—	[50]
Mn1.06Te+2%SnTe	873	64.9	0.66	379	89	1.4	—	—	—	—	[50]
Ag2Te	300	213.1	0.25	−90	1818	0.45	0.04	—	<0.1	—	[55]
Ag2Te	550	32.2	0.23	−119	463	0.62	0.2	—	—	—	[55]
(Ag1.9996Te)0.9(PbTe)0.1	300	177.2	0.38	−101	1299	0.38		—	—	—	[55]
(Ag1.9996Te)0.9(PbTe)0.1	550	34.1	0.23	−178	241	1	0.28	—	—	—	[55]
Ag2Sb0.02Te0.98	300	99.2	0.36	−105	689	0.35	0.08	—	—	—	[56]
Ag2Sb0.02Te0.98	410	80.6	—	−106	883	1.4		—	—	—	[56]
Cu2Te	320	79.9	6.1 (kT)	15	4878	—	0.26	—	1.5	—	[53]
Cu2Te	1000	20.2	2.36 (kT)	93	1008	0.37	—	—	—	—	[53]
Cu1.98Ag0.2Te	300	128.3	1.98 (kT)	47	2256	0.08	—	—	—	—	[111]
Cu1.98Ag0.2Te	900	30.8	1.3 (kT)	158	575	1	—	—	—	—	[111]
Cu2S0.52Te0.48	300	20.2	0.49 (kT)	62	265	—	—	—	4.5	—	[54]
Cu2S0.52Te0.48	1000	15.5	0.38 (kT)	218	168	2.09	—	—	—	—	[54]
Cu1.9Sn0.1Te	320	109.6	1.22 (kT)	38	2638	0.1	0.25	—	2.56	—	[53]
Cu1.9Sn0.1Te	1000	27.7	0.97 (kT)	133	819	1.5	—	—	—	—	[53]
Cu2Te+50%Ag2Te	300	67.5	1.32 (kT)	54	1027	0.07	—	—	—	—	[112]
Cu2Te+50%Ag2Te	1000	20.1	0.64 (kT)	178	348	1.8	—	—	—	—	[112]
AgCuTe	300	39.3	0.35	31	1055	0.15	—	—	—	—	[52]
AgCuTe	660	29.9	0.23	228	155	1.3	—	—	—	—	[52]
AgCuTe0.9Se0.1	300	31.2	0.15	70	359	0.36	—	—	—	—	[52]
AgCuTe0.9Se0.1	670	38.4	0.25	223	216	1.6	—	—	—	—	[52]
AgCuTe0.9I0.1	300	39	0.21	143	168	0.35	—	—	1.21	—	[113]
AgCuTe0.9I0.1	463	33.8	0.17	287	52	0.9	—	—	—	—	[113]
AgGaTe2	300		1.42			—	1.06	—	—	—	[57]
AgGaTe2	750	16.5	0.33	414	12	0.48	—	—	—	—	[57]
Ag0.95GaTe2	300	26.2	1.26 (kT)	673	0.24		—	—	—	—	[114]
Ag0.95GaTe2	850	14.1	0.2 (kT)	382	18	0.77	—	—	—	—	[114]
AgGa0.93Te2	300	—	1.16 (kT)	—	—	—	—	—	—	—	[58]
AgGa0.93Te2	873	11.9	0.18 (kT)	396	13.4	1.02	—	—	—	—	[58]
AgInTe2	300		1.42			—	0.87	—	—	—	[57]
AgInTe2	750	14.2	0.33	570	1.7	0.18	—	—	—	—	[57]
CuGaTe2	300	76.9	6.7	380	21	—	1.2	—	—	—	[115]
CuGaTe2	950	30.5	0.51	244	227	1.4	—	—	—	—	[115]
CuGaTe2	300	117.6	6.7	395	27	—	1.18	—	—	—	[57]
CuGaTe2	875	38	0.95	281	163	1	—	—	—	—	[57]
CuGa0.36In0.64Te2	320	36.6	1.48	390	9.8	—	0.85	—	—	—	[116]
CuGa0.36In0.64Te2	701	39.2	0.56	285	115	0.91	—	—	—	—	[116]
Cu0.98GaSb0.02Te2	310	14.4	3.1	176	44	—	0.95	—	—	—	[117]
Cu0.98GaSb0.02Te2	721	40.6	0.48	262	162	1.07	—	—	—	—	[117]
Cu0.7Ag0.3Ga0.4In0.6Te2	300	252.7	—	588	6.2	—	—	—	—	—	[63]
Cu0.7Ag0.3Ga0.4In0.6Te2	873	32.9	0.25	406	33	1.64	—	—	—	—	[63]
CuInTe2	300	112.7	6 (kT)	247	144	—	1.02	—	0.52	—	[118]
CuInTe2	850	35.8	1.05 (kT)	270	167	1.18	—	—	—	—	[118]
CuInTe2	300	155	5.9	464	16	—	0.92	—	—	—	[57]
CuInTe2	875	28	0.81	290	108	0.9	—	—	—	—	[57]
Cu0.9InTe2	300	78.8	3 (kT)	170	246	0.11	—	—	0.6–0.8	—	[119]
Cu0.9InTe2	710	35.5	1.33 (kT)	214	242	0.54	—	—	—	—	[119]
Cu0.75Ag0.2InTe2	300	46.5	1.86 (kT)	234	69	0.07	—	—	—	—	[120]
Cu0.75Ag0.2InTe2	850	27.6	0.52(kT)	320	72	1.25	—	—	—	—	[120]
CuInTe1.99Sb0.01+1%ZnO	300	86.6	3.6	104	610	—	—	—	—	—	[61]
CuInTe1.99Sb0.01+1%ZnO	823	47.7	0.45	284	180	1.61	—	—	—	—	[61]
CuInTe2+6%ZnS	300	85.7	3.54	157	312		—	—	—	—	[60]
CuInTe2+6%ZnS	823	37.5	0.44	282	145	1.52	—	—	—	—	[60]
Cu0.89Ag0.2In0.91Te2	300	149.4	2.68 (kT)	446	19	—	0.9	—	—	—	[62]
Cu0.89Ag0.2In0.91Te2	850	31.8	0.47 (kT)	315	88	1.6	—	—	—	—	[62]
BiTe	300	149.3	0.72	−37	3352	0.05	0.1	—	—	—	[66]
BiTe	500	78.8	0.76	−61	2267	0.13	—	—	—	—	[66]
BiTe0.5Se0.5	300	170.6	1.8 (kT)	−49	2873	0.12	—	—	—	—	[66]
BiTe0.5Se0.5	500	93.5	2.1(kT)	−79	2014	0.32	—	—	—	—	[66]
BiCuOTe	300	62.7	0.68(kT)	173	189	0.4	0.21	—	—	—	[121]
BiCuOTe	673	24.2	0.73(kT)	183	218	0.66	—	—	—	—	[121]
BiCuO0.88Te	323	114.8	0.59	185	336	0.48	—	—	—	—	[67]
BiCuO0.88Te	673	29.6	0.33	207	202	1.06	—	—	—	—	[67]
La3−x Te4 (1.2E21) b	1275	9.3	0.5 (kT)	−300	56	1.13	—	—	—	—	[122]
La3−x Te4 (1.2E21) b	300	—	—	—	—	—	0.83		2.75	—	[122]
La2.6Yb0.4Te4 (3E20) b	1273	11.1	0.66 (kT)	−289	76	1.2	—	—	—	—	[68]
Pr2.74Te4	300	58.1	0.846	−48	1000	0.03	—	—	3.5	—	[65]
Pr2.74Te4	1200	18.1	0.427	−240	200	1.7	—	—	—	—	[65]

^a kT—indicates total thermal conductivity. ^b (1.2E21)—numbers of this type after the material name indicates the carrier concentration (cm⁻³).

While both SnTe and PbTe crystallize in the cubic rocksalt structure at ambient conditions, GeTe has a rhombohedral crystal structure at room temperature. However, GeTe undergoes a rhombohedral to cubic phase transition at ∼720 K. All three are narrow band gap semiconductors with band gap in the range ∼0.18–0.32 eV. As a result of this favorable band gap, highly-symmetric crystal structure leading to degenerate electronic bands, easy tuneability of electronic structure via chemical doping and alloying, and heavy constituent elements, they are ideal for exploring high thermoelectric performance. At present, a thermoelectric figure of merit, zT as high as ∼2.7 at 720 and ∼2.57 at 850 K can be achieved in GeTe [10] and PbTe [11] based p-type thermoelectric materials, respectively. While SnTe is much less toxic than PbTe, the maximum zT obtained so far is only 1.6 at 720 K [12, 13].

PbTe is a very important thermoelectric material; both band convergence and resonant level formation strategies were first demonstrated in PbTe. Resonant level formation in PbTe upon Tl doping [14] and valence band convergence in PbTe_1−x Se_x :Na [15] resulted in maximum zT ∼ 1.5 and 1.8 in 2008 and 2011, respectively. Since then, these electronic structure modulation strategies have been followed up for numerous materials, and many 2nd (1 ⩽ zT ⩽ 2) and 3rd (zT > 2) generation thermoelectric materials have been achieved, including in GeTe and SnTe. For example, In doping has been very effective in inducing resonant levels in both SnTe [16] and GeTe [17], significantly improving their thermoelectric performance. Similarly, doping or alloying of Sb [18], Mn [19], Zn [20], Cd [21] in GeTe is also highly effective in inducing valence band convergence. While PbTe and SnTe have the same rocksalt crystal structure, the larger energy gap (∼0.35 eV) between the primary and secondary valence bands in SnTe results in low Seebeck coefficients and consequently poor thermoelectric performance. Doping and alloying of many elements like Mn [22], Mg [23], Cd [24], Hg [25] etc are highly effective in reducing the gap between the primary and secondary valence bands. It has also been demonstrated that synergistic effects of band convergence and resonant level can further improve the thermoelectric performance. This has been achieved in SnTe via co-doping of In and Cd [26], and In and Ag [27]. Another highly successful strategy, based on phonon scattering manipulation, namely, all-scale hierarchical architecture, was first demonstrated in PbTe, resulting in maximum zT ∼ 2.2 at 915 K [28]. Recently, lattice strain in Na–Eu–Sn doped PbTe has been shown to be very effective in reducing lattice thermal conductivity without compromising the carrier mobility; it resulted in zT ∼ 2.57 at 850 K [11]. Many synergistic effects of electronic structure modulation and thermal transport optimization have also been achieved via co-doping in GeTe and SnTe. For example, complementary effects of resonant state formation via In doping, and reduced thermal conductivity due to solid solution point defects with Bi doping, results in high thermoelectric performance with zT ∼ 2.1 at 723 K in In and Bi co-doped GeTe [29]. Similarly, synergistic effects have also been achieved in GeTe by co-doping Sb and Bi [18], and in SnTe via co-doping of Ag and Mn [30].

One major problem in SnTe and GeTe is their high p-type carrier concentration due to cation vacancies. Doping, such as Bi in GeTe [21, 31] and self-compensation in SnTe [30] have been effective in reducing the hole concentration. The rhombohedral to cubic phase transition in GeTe has been used as an added control parameter to achieve high thermoelectric performance. The high temperature cubic phase of GeTe possesses a four-fold degenerate light L band at higher energy and 12-fold degenerate heavy Σ band at lower energy. The polar distortion along the [1 1 1] crystallographic direction in the rhombohedral phase, however, splits the 4 L pockets into 3 L and 1 Z pockets, and the 12 Σ pockets into 6 Σ and 6 η pockets. Moreover, in the rhombohedral phase, the Σ band becomes the principal valance band with higher energy. This reduction of band degeneracy, and practical problems arising from the high-temperature phase transition, led to much effort on reducing the phase transition temperature and achieving higher thermoelectric performance in the cubic phase at lower temperature. For example, In and Sb co-doping [32], Bi and Mn co-doping [33] and MnTe alloying [19] have been successful. In recent years, however, it has been shown that precise control of the rhombohedral distortion can be used to achieve a higher degree of effective band degeneracy due to band orbital overlap and reduced lattice thermal conductivity using Bi doping [34]. This resulted in a maximum zT ∼ 2.4 at 600 K. Very recently, it was shown that Rashba spin splitting can be used to achieve effective band convergence in Sn doped GeTe [35].

As can be seen from figure 2, high thermoelectric performance has been achieved in these materials with p-type thermoelectric transport. In fact, because of intrinsic Sn and Ge vacancies, it is very difficult to achieve n-type thermoelectric transport. Only recently n-type thermoelectric transport has been reported in GeTe through AgBiSe₂ alloying [36]. However, the zT ∼ 0.6 at 500 K is much lower than that of the high zT of p-type, GeTe-based thermoelectric materials. Indeed, n-type thermoelectric transport is far more explored in PbTe. Still, the presence of a single conduction band at the L point, compared to the multivalley degenerate valence band structure at L and Σ points, makes it challenging to achieve high n-type thermoelectric transport in PbTe. Introduction of mid-gap states through In [37] and Ga [38] doping in PbTe was highly effective in enhancing the n-type thermoelectric performance. The n-type thermoelectric performance of PbTe has also benefited from enhanced effective mass by conduction band flattening through MnTe alloying [39]. In a recent study, introduction of energy filtering through multiphase nano-structuring in a PbTe–InSb composite greatly improved the n-type thermoelectric performance of PbTe, with zT of 1.83 at 773 K [40].

Bi₂Te₃ and its solid solution alloys with Sb₂Te₃ and Bi₂Se₃ have been used in practical applications since the 1950s [41], and today they are still the most widely used thermoelectric materials for near room temperature applications. These are layered materials and have hexagonal close packed arrangement of anions. The structure comprises quintuple atomic layers of Te(1)–Bi–Te(2)–Bi–Te(1) along the crystallographic c-direction and two successive quintuple layers are held together by weak van der Waals' (vdW) interactions between two Te(1) layers. Such a layered structure causes anisotropic electrical and thermal transport properties when measured parallel and perpendicular to the layered plane. The highly polarizable Bi–Te bonds, the presence of weak vdW bonds within the layered structure and the constituent heavy elements result in strong lattice anharmonicity and consequently a low lattice thermal conductivity. Bi₂Te₃ is an indirect narrow band gap semiconductor with E_g ∼ 0.15 eV. A low band effective mass and a highly degenerate electronic band structure also results in high Seebeck coefficient with high charge carrier mobility. Phonon scattering from point defects due to Bi and Sb disorder in Bi_0.5Sb_1.5Te₃ also markedly reduces lattice thermal conductivity. These combinations of low lattice thermal conductivity, favorable electronic band structure and high charge carrier mobility makes Bi₂Te₃ based materials good candidate thermoelectric materials. The thermoelectric properties of these materials have been greatly improved recently by microstructural engineering and nanostructuring, which result in lower lattice thermal conductivity while retaining relatively high carrier mobility with optimized μ/κ_L; p-type zT ∼ 1.4 at 373 K was obtained in Bi_x Sb_2−x Te₃ alloys by hot pressing ball-milled nanopowders [42]. Recently, nanostructuring with secondary phase nanoprecipitates has also been achieved in BiSbTe–Zn alloys [43]. Melt-centrifugation has been very effective in controlling the microstructure in (Bi,Sb)₂Te₃, with microscale dislocation arrays and a porous network, giving superior thermoelectric performance than zone-melted and hot pressed ingots [44]. While point defects scatter high frequency phonons, boundary scattering targets the low frequency phonons. Recently, liquid phase sintering was adopted to produce low energy grain boundaries with dense dislocation arrays which include scattering of mid-frequency phonons without simultaneously decreasing the charge carrier mobility. This resulted in a record high thermoelectric p-type figure of merit zT ∼ 1.86 at 320 K in (Bi,Sb)₂Te₃ alloy [45]. Such liquid phase sintering has also been applied in Sb doped Bi₂Te_2.7Se_0.3 to obtain a high zT n-type material and a large density of dislocation arrays has been observed in the sample. The consequent decrease of lattice thermal conductivity while retaining high charge carrier mobility resulted in n-type zT ∼ 1.4 at 425 K [46]. Bi₂Te_2.7Se_0.3 nanoplates have also been synthesized in a microwave-assisted synthesis route, which have zT ∼ 1.23 at 480 K [47]. While many studies have focused on microstructure engineering to optimize the thermal transport, recently K doping has been used to modulate the electrical transport in Bi₂Te₃; for n-type material, zT ∼ 1.1 was obtained at 350 K [48].

In this section, we discuss the TM based tellurides including MnTe, Ag₂Te, Cu₂Te and AgCuTe. MnTe crystallizes in a hexagonal structure and is an indirect band gap semiconductor with E_g ∼ 0.8 eV. While MnTe exhibits high Seebeck coefficient, its low carrier concentration (10¹⁸ cm⁻³) results in poor thermoelectric performance. Many dopants, such as Cu, Ag, Na have been introduced to improve the carrier concentration, which resulted in a maximum zT ∼ 1.09 at 873 K [49]. Recently, the incorporation of SnTe nanocrystals was very effective in improving zT ∼ 1.4 at 873 K [50]. Another novel concept based on paramagnon drag enhancement of the Seebeck coefficient has been used to improve thermoelectric performance [51]. This resulted in maximum zT ∼ 1 at 923 K in Li doped MnTe. On the other hand, Cu₂Te, Ag₂Te and AgCuTe are superionic conductors. At room temperature, they have a complex crystal structure: for example, the ambient structure of AgCuTe and Ag₂Te are hexagonal and monoclinic, respectively. However, at high temperature, these materials have a cubic structure and exhibit superionic conduction. In the superionic phase, the anions form a rigid framework which supports high electrical conduction while the cations become superionic and impede phonon propagation. Such a resemblance to the phonon-glass electron-crystal (PGEC) scenario drives thermoelectric interest in these materials. However, high hole concentrations due to cation vacancies causes metallic conduction and low Seebeck coefficients. Recently, Se alloying in AgCuTe was very effective in suppressing cation vacancies due to stronger Ag–Se/Cu–Se bonds compared to Ag–Te/CuTe bonds. Additionally, dynamic cation disorder decreases lattice thermal conductivity, and an impressive zT ∼ 1.6 at 670 K was obtained in Se doped AgCuTe [52]. Similarly, Sn doping has been used to tune the high hole concentration of Cu₂Te and zT ∼ 1.5 has been achieved at 1000 K [53]. A mosaic crystal of Cu₂(Te,S) has also been reported with zT ∼ 2.09 at 1000 K [54]. In contrast to p-type electronic transport of Cu₂Te and AgCuTe, Ag₂Te exhibits n-type conduction. In Ag₂Te, increased band conduction in PbTe alloyed Ag₂Te resulted in zT ∼ 1 at 550 K in the high temperature superionic phase [55]. In contrast, Sb doping has been shown to be effective in increasing the carrier concentration and electrical conductivity in the low temperature monoclinic phase of Ag₂Te and zT ∼ 1.4 has been achieved at 410 K [56].

The I–III–VI₂ (I = Ag, Cu; III = Ga, In; VI = Te) semiconductors, with unique electronic and thermal transport properties, are potential high performance thermoelectric materials. These materials have diamond like structures formed by the interconnected (I–VI)₄ and (III–VI)₄ tetrahedra. Compared to IV–VI semiconductors, these chalcopyrites are wide band gap semiconductors with E_g ∼ 0.8–1.2 eV. Despite having similar crystal structures, all the I–III–VI₂ (I = Ag, Cu; III = Ga, In; VI = Te) semiconductors have distinctly different electrical and thermal transport properties [57]. AgGaTe₂ and AgInTe₂ possess low thermal conductivity; however, their low electrical conductivity renders them unsuitable as high-performance thermoelectric materials. The presence of Ga vacancies in AgGaTe₂ greatly improves thermoelectric performance, with zT ∼ 1.02 at 873 K [58]. The related tellurides CuGaTe₂ and CuInTe₂ possess both high electrical conductivity and high thermal conductivity. Therefore, much effort has been devoted to lowering the lattice thermal conductivity of CuGaTe₂ and CuInTe₂ via a range of strategies based on inclusions and point defects. For example, the inclusion of nanophase Cu₂Se in CuGaTe₂ significantly reduces lattice thermal conductivity [59]. Similarly, ZnS nanoscale heterostructures [60] and In₂O₃ nanoinclusions [61] have been incorporated in CuInTe₂ to lower its lattice thermal conductivity. Solid solution alloying of Ag into CuInTe₂ lowers lattice thermal conductivity by forming weak Ag–Te bonds, which results in a high zT ∼ 1.6 at 850 K [62]. Multicomponent alloying of Ag and In in CuGaTe₂ has also been very successful in lowering the lattice thermal conductivity, yielding zT ∼ 1.64 at 873 K [63].

Many metal tellurides materials are used in practical applications because of their high thermoelectric performance. Recent advances in understanding of electronic structure, electrical and thermal transport properties, and sophisticated material processing techniques have led to important improvements in their thermoelectric performance in recent years. Furthermore, a range of novel strategies have been developed, including the precise control of the rhombohedral distortion [34] and Rashba spin splitting in GeTe [35], engineering ferroelectric instability in SnTe [13], and greatly improved material processing techniques for Bi₂Te₃ based materials [45] for microstructure and nanostructure engineering. Recently, a very high zT ∼ 2.6 at 573 K was achieved in I–IV–VI₂ compound AgSbTe₂ by inducing nanoscale ordering [64]. Similarly, the novel concept of paramagnon drag in MnTe was employed to improve thermoelectric performance [51]. In recent years, rare earth tellurides like Pr_3−x Te₄ have also been introduced with high zT ∼ 1.7 at 1200 K [65]. In addition to developing new high performance thermoelectric materials, unique strategies of electronic structure and phonon transport manipulation are necessary to achieve higher thermoelectric performance. Currently, the inferior performance of the counterpart n-type thermoelectric materials is major drawback, which needs to be addressed. Similarly, Te-based oxide thermoelectric materials, which have great potential in practical applications for high resistance against corrosion and thermal degradation, are worthy of attention.

Pengfei Qiu^1,4, Shun Wan^2,4 and Lidong Chen^1,3

Skutterudites (table 2) are among the best thermoelectric materials for applications in intermediate temperatures [123–125]. Binary skutterudites, with the chemical formula of MX₃ (M = Co, Rh, or Ir, X = P, As, or Sb), crystalize in a body-centered cubic structure (Im-3), with the structure shown in figure 3(a). There are two large icosahedral voids per unit (M₈X₂₄), which can be filled with guest atoms (e.g. alkalis, alkaline earths, rare earths, and others) forming filled skutterudites. The chemical formula of filled skutterudites can be written as G_yM₄ X₁₂, where G represents the fillers and y is the filling fraction. The fillers G are weakly bonded with the surrounding atoms with large atomic displacement parameters, which can strongly interrupt the normal transport of phonons by introducing additional localized vibrational modes and therefore significantly lower the lattice thermal conductivity (κ_L). By the combination of significantly reduced thermal conductivity and (maintaining) good electrical transport, the filled skutterudites well satisfy the PGEC concept proposed by Slack [126, 127].

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Table 2. Skutterudite thermoelectrics properties.

Material/actual composition	µw (cm2 V−1 s−1)	κ (W m−1 K−1)	κL (W m−1 K−1)	S (µV K−1)	σ (Ω−1 cm−1)	zT	n or p (1020 cm−3)	Eg (eV)	µH (cm2 V−1 s−1)	ms * (me)	r or (0)	References
K0.09±0.01 Co4Sb12 (300 K)	339.5	7.0	6.6	−212	650	0.1	—	—	—	—	—	[128]
K0.09±0.01 Co4Sb12 (800 K)	39.4	4.4	3.8	−193	410	0.3	—	—	—	—	—	[128]
K0.22±0.01 Co4Sb12 (300 K)	286.9	6.7	5.7	−120	1640	0.1	—	—	—	—	—	[128]
K0.22±0.01 Co4Sb12 (800 K)	53.7	4.3	3.3	−180	650	0.4	—	—	—	—	—	[128]
K0.38±0.02 Co4Sb12 (300 K)	430.9	6.3	4.7	−114	2660	0.2	—	—	—	—	—	[128]
K0.38±0.02 Co4Sb12 (800 K)	125.8	3.9	2.0	−199	1220	1.0	—	—	—	—	—	[128]
K0.45±0.02 Co4Sb12 (300 K)	398.2	6.2	4.5	−106	2730	0.2	—	—	—	—	—	[128]
K0.45±0.02 Co4Sb12 (800 K)	113.7	4.1	1.9	−181	1360	0.9	—	—	—	—	—	[128]
CoSb3 (300 K)	164.3	8.5	8.1	145	690	0.1	—	—	—	—	—	[129]
CoSb3 (600 K, peak)	51.2	3.9	3.5	197	330	0.2	—	—	—	—	—	[129]
CoSb3 (850 K)	2.2	3.8	3.3	28	310		—	—	—	—	—	[129]
Na0.13 Co4Sb12 (300 K)	390.8	6.9	6.4	−200	860	0.2	0.8	—	69.7	2.4	—	[129]
Na0.13 Co4Sb12 (700 K, peak)	103.6	3.8	3.2	−259	410	0.5	0.8	—	33.2	1.7	—	[129]
Na0.13 Co4Sb12 (850 K)	37.2	3.3	2.6	−200	390	0.4	0.8	—	31.6	0.9	—	[129]
Na0.23 Co4Sb12 (300 K)	401.9	6.8	6.1	−169	1270	0.2	1.4	—	55.8	2.8	—	[129]
Na0.23 Co4Sb12 (700 K, peak)	119.5	3.7	2.8	−237	610	0.7	1.4	—	26.8	2.1	—	[129]
Na0.23 Co4Sb12 (850 K)	53.4	3.7	2.7	−200	560	0.5	1.4	—	24.6	1.3	—	[129]
Na0.36 Co4Sb12 (300 K)	415.9	6.1	4.7	−117	2470	0.2	4.0	—	38.7	3.3	—	[129]
Na0.36 Co4Sb12 (850 K)	99.2	3.8	1.8	−190	1170	1.0	4.0	—	18.4	2.4	—	[129]
Na0.48 Co4Sb12 (300 K)	431.6	5.4	3.8	−111	2770	0.2	5.9	—	29.5	4.0	—	[129]
Na0.48 Co4Sb12 (850 K)	119.4	3.4	1.3	−203	1210	1.3	5.9	—	12.9	1.4	—	[129]
Ba0.07 Co4Sb11.88 (300 K)	228.5	6.4	5.8	−139	1032	0.1	—	—	—	—	—	[130]
Ba0.07 Co4Sb11.88 (850 K)	49.2	4.4	3.5	−192	567	0.4	—	—	—	—	—	[130]
Ba0.16 Co4Sb11.85 (300 K)	434.6	5.9	4.6	−132	2138	0.2	—	—	—	—	—	[130]
Ba0.16 Co4Sb11.85 (850 K)	95.8	4.4	2.5	−190	1130	0.8	—	—	—	—	—	[130]
Ba0.24 Co4Sb11.87 (300 K)	368.4	5.4	3.4	−88	3234	0.1	—	—	—	—	—	[130]
Ba0.24 Co4Sb11.87 (850 K)	126	4.2	1.3	−178	1709	1.1	—	—	—	—	—	[130]
Ba0.38 Co4Sb11.74 (300 K)	342.6	4.8	2.4	−70	3939	0.1	—	—	—	—	—	[130]
Ba0.38 Co4Sb11.74 (850 K)	92.6	3.9	0.5	−137	2044	0.8	—	—	—	—	—	[130]
Ba0.44 Co4Sb11.90 (300 K)	537.2	6.6	2.8	−68	6378	0.1	—	—	—	—	—	[130]
Ba0.44 Co4Sb11.90 (850 K)	115.6	5.9	0.1	−114	3404	0.6	—	—	—	—	—	[130]
Sr0.12 Co4Sb12.46 (300 K)	195.3	5.6	5.1	−137	903.6	0.1	1.3	—	43.4	1.9	—	[131]
Sr0.12 Co4Sb12.46 (850 K)	47.2	3.8	2.7	−180	625	0.5	1.3	—	30	1.0	—	[131]
Sr0.17 Co4Sb12.88 (300 K)	265.4	5.4	4.6	−129	1355	0.1	1.6	—	52.9	2.1	—	[131]
Sr0.17 Co4Sb12.88 (850 K)	67.9	3.3	2.0	−195	755	0.7	1.6	—	29.5	1.3	—	[131]
Sr0.22 Co4Sb12.72 (300 K)	309.4	5.2	4.1	−119	1791	0.2	2.3	—	48.6	2.4	—	[131]
Sr0.22 Co4Sb12.72 (850 K)	73.9	3.3	1.7	−179	990	0.8	2.3	—	26.9	1.5	—	[131]
Sr0.28 Co4Sb12.88 (300 K)	417.8	5.1	3.4	−110	2717	0.2	3.8	—	44.6	3.0	—	[131]
Sr0.28 Co4Sb12.88 (850 K)	80	3.3	1.4	−176	1110	0.9	3.8	—	18.2	2.0	—	[131]
Sr0.40 Co4Sb12.54 (300 K)	266.6	5.4	2.9	−52	4220	0.1	6.7	—	39.3	2.0	—	[131]
Sr0.40 Co4Sb12.54 (850 K)	78.5	4.1	0.6	−123	2060	0.7	6.7	—	19.2	1.8	—	[131]
Ga0.03 Co4Sb11.985Ga0.015 (300 K)	137.7	3.5	3.5	−286.6	111	0.1	0.2	—	29.6	2.2	—	[132]
Ga0.03 Co4Sb11.985Ga0.015 (600 K)	78.2	2.4	2.3	−323	117	0.3	0.2	—	31.8	1.5	—	[132]
Ga0.03 Co4Sb11.985Ga0.015 (650 K)	37	2.6	2.4	−268	118	0.2	0.2	—	32	0.9	—	[132]
Ga0.06 Co4Sb11.97Ga0.03 (300 K)	249.9	3.4	3.3	−272.6	237	0.2	0.4	—	41.1	2.7	—	[132]
Ga0.06 Co4Sb11.97Ga0.03 (600 K)	114.6	2.4	2.2	−315	188	0.5	0.4	—	32.6	1.9	—	[132]
Ga0.06 Co4Sb11.97Ga0.03 (650 K)	77.2	2.6	2.3	−289	193	0.4	0.4	—	33.5	1.4	—	[132]
Ga0.10 Co4Sb11.95Ga0.05 (300 K)	281.2	3.4	3.2	−228.6	444	0.2	0.4	—	63	2.1	—	[132]
Ga0.10 Co4Sb11.95Ga0.05 (600 K)	158	2.6	2.1	−285	367	0.7	0.4	—	52.1	1.7	—	[132]
Ga0.10 Co4Sb11.95Ga0.05 (650 K)	127.2	2.7	2.2	−281	349	0.7	0.4	—	49.5	1.5	—	[132]
Ga0.15 Co4Sb11.925Ga0.075 (300 K)	241.3	3.2	3.0	−246.4	310	0.2	0.4	—	47.2	2.4	—	[132]
Ga0.15 Co4Sb11.925Ga0.075 (600 K)	117.7	2.4	2.1	−291	255	0.5	0.4	—	38.8	1.7	—	[132]
Ga0.15 Co4Sb11.925Ga0.075 (650 K)	94.7	2.5	2.2	−285	248	0.5	0.4	—	37.8	1.5	—	[132]
In0.075 Co4Sb11.975 (300 K)	307.1	3.7	3.5	−237	440	0.2	0.5	—	57.2	2.4	—	[133]
In0.075 Co4Sb11.975 (600 K, peak)	157.8	2.5	2.1	−289	350	0.7	0.5	—	45.5	1.9	—	[133]
In0.075 Co4Sb11.975 (800 K)	45.3	3.4	2.9	−221	340	0.4	0.5	—	44.2	0.8	—	[133]
In0.15 Co4Sb11.95 (300 K)	479	3.2	2.6	−202	1030	0.4	0.9	—	69.1	2.8	—	[133]
In0.15 Co4Sb11.95 (700 K, peak)	144.1	2.5	1.7	−259	570	1.1	0.9	—	38.3	1.9	—	[133]
In0.15 Co4Sb11.95 (800 K)	96.2	2.8	1.9	−243	560	1.0	0.9	—	37.6	1.5	—	[133]
In0.225 Co4Sb11.925 (300 K)	384.8	3.0	2.3	−173	1160	0.4	2.4	—	30.8	4.0	—	[133]
In0.225 Co4Sb11.925 (700 K, peak)	139.5	2.5	1.6	−241	680	1.1	2.4	—	18.1	3.1	—	[133]
In0.225 Co4Sb11.925 (800 K)	99.1	2.8	1.8	−234	640	1.0	2.4	—	17	2.6	—	[133]
In0.30 Co4Sb11.90 (300 K)	399.3	2.9	2.0	−162	1370	0.4	1.7	—	49.1	3.0	—	[133]
In0.30 Co4Sb11.90 (750 K, peak)	136.2	2.7	1.6	−236	780	1.2	1.7	—	28	2.3	—	[133]
In0.30 Co4Sb11.90 (800 K)	117.8	2.8	1.6	−233	770	1.2	1.7	—	27.6	2.1	—	[133]
p-type CoSb3 (300 K)-121OB22	66.2	—	—	280	57.6	—	—	From resistivity: 0.75 eV From Hall: 0.63 eV	2996.3	0.1	—	[134]
p-type CoSb3-121OB22	0.9	—	—	10 (890 K)	400 (930 K)	—	—		—	—	—	[134]
p-type CoSb3 (300 K)-10OB22	136.3	—	—	240	188.6	—	—		2675.6	0.1	—	[134]
p-type CoSb3-10OB22	0.9	—	—	10 (890 K)	400 (930 K)	—	—		—	—	—	[134]
p-type CoSb3 (300 K)-23NB12	222.9	—	—	179	626.6	—	—		2590.3	0.2	—	[134]
p-type CoSb3-23NB12		—	—		400 (930 K)	—	—		—	—	—	[134]
p-type CoSb3 (300 K)-2NB13	272.7	—	—	139	1231.5	—	—		1976.2	0.2	—	[134]
p-type CoSb3-2NB13	8.5	—	—	85 (890 K)	400 (930 K)	—	—		—	—	—	[134]
p-type CoSb3 (300 K)-2NB9	234.8	—	—	80	2314.8	—	0.1		1529	0.2	—	[134]
p-type CoSb3-2NB9	1.1	—	—	10 (890 K)	476 (850 K)	—	0.1		—	—	—	[134]
n-type CoSb3 (300 K)-1CS10-0.08 at.% Te	593.7	10.3	10.3	−452	70.42	0.04	0.05	0.55 eV	96.8	2.8	—	[134]
n-type CoSb3-1CS10-0.08 at.% Te	4.6	5.3 (760 K)	—	46 (800 K)	358 (800 K)	—	0.05		—	—	—	[134]
n-type CoSb3 (300 K)-1CS11-0.15 at.% Te	606	—	—	−373	179.53	—	0.1		87.1	3.0	—	[134]
n-type CoSb3-1CS11-0.15 at.% Te	4.1	—	—	44 (800 K)	334.45 (800 K)	—	0.1		—	—	—	[134]
n-type CoSb3 (300 K)-2CS9-0.12 at.%Te	507.7	—	—	−364	166.94	—	0.2		68.6	3.1	—	[134]
n-type CoSb3-2CS9-0.12 at.%Te	4.1	—	—	38 (800 K)	393.7 (800 K)	—	0.2		—	—	—	[134]
n-type CoSb3 (300 K)-4OB25-0.6 at.% Pd	302.4	9.5	9.3	−280	263.16	0.1	0.4		37.2	3.3	—	[134]
n-type CoSb3-4OB25-0.6 at.% Pd	11	4.9 (770 K)	—	−103 (780 K)	330 (800 K)	—	0.4		—	—	—	[134]
n-type CoSb3 (300 K)-OB26 ∼1 at.% Pd	327.3	6.1	5.6	−180	909.09	0.1	1.4		41.1	3.0	—	[134]
n-type CoSb3-OB26 ∼1 at.% Pd	69.6	4.1 (770 K)	—	−207 (770 K)	581 (800 K)	—	1.4		—	—	—	[134]
CoSb3 (300 K)	1064	8.3	8.3	−625	17	0.02	0.1	—	17.7	12.8	—	[135]
CoSb3 (600 K, peak)	31	4.2	4.0	205	182	0.1	0.1	—	189.3	0.2	—	[135]
CoSb3 (850 K)	4.1	4.7	4.2	56	284	0.02	0.1	—	295.5	0.0	—	[135]
Co4Sb11.95Te0.05 (300 K)	191.1	7.6	7.3	−194	451	0.1	0.9	—	30.9	2.6	—	[135]
Co4Sb11.95Te0.05 (600 K, peak)	159.3	4.0	3.7	−310	277	0.4	0.9	—	19	3.4	—	[135]
Co4Sb11.95Te0.05 (850 K)	26.1	5.0	4.6	−218	222	0.2	0.9	—	15.2	1.1	—	[135]
Co4Sb11.7Te0.3 (300 K)	129.1	5.1	4.8	−148	523	0.1	1.8	—	18	2.7	—	[135]
Co4Sb11.7Te0.3 (850 K)	45.1	3.9	3.3	−231	330	0.4	1.8	—	11.4	2.0	—	[135]
Co4Sb11.5Te0.5 (300 K)	182.5	3.9	3.3	−123	1004	0.1	5.7	—	11	4.5	—	[135]
Co4Sb11.5Te0.5 (850 K)	62.7	3.1	2.0	−200	658	0.7	5.7	—	7.2	3.3	—	[135]
Co0.98Ni0.02Sb3 (300 K)	184.8	—	—	−243	247	—	0.7	—	22	3.3	—	[136]
Co0.98Ni0.02Sb3 (800 K)	39.2	—	—	−203	363	—	0.7	—	32.4	0.9	—	[136]
Co0.97Ni0.03Sb3 (300 K)	176	—	—	−207	357	—	1.5	—	14.9	4.0	—	[136]
Co0.97Ni0.03Sb3 (800 K)	58.9	—	—	−217	463	—	1.5	—	19.3	1.6	—	[136]
Co0.955Ni0.045Sb3 (300 K)	122.6	—	—	−144	521	—	2.5	—	13	3.2	—	[136]
Co0.955Ni0.045Sb3 (800 K)	81.6	—	—	−225	585	—	2.5	—	14.6	2.5	—	[136]
Co0.94Ni0.06Sb3 (300 K)	137.5	—	—	−133	668	—	3.4	—	12.3	3.5	—	[136]
Co0.94Ni0.06Sb3 (800 K)	85.6	—	—	−210 (700 K)	730	—	3.4	—	13.4		—	[136]
Co0.925Ni0.075Sb3 (300 K)	135.8	—	—	−113	849	—	4.4	—	12	3.4	—	[136]
Co0.925Ni0.075Sb3 (800 K)	64.7	—	—	−180	783	—	4.4	—	11.1	2.4	—	[136]
Co0.91Ni0.09Sb3 (300 K)	135.6	—	—	−101	994	—	5.5	—	11.3	3.5	—	[136]
Co0.91Ni0.09Sb3 (800 K)	82.7	—	—	−180 (700 K)	1000	—	5.5	—	11.3		—	[136]
Co0.88Ni0.12Sb3 (300 K)	129.4	—	—	−88	1136	—	12.0	—	5.9	5.0	—	[136]
Co0.88Ni0.12Sb3 (800 K)	78.9	—	—	−167	1111	—	12.0	—	5.8	4.2	—	[136]
Co0.85Ni0.15Sb3 (300 K)	126.3	—	—	−74	1364	—	20.9	—	4.1	6.0	—	[136]
Co0.85Ni0.15Sb3 (800 K)	75.3	—	—	−151	1282	—	20.9	—	3.8	5.3	—	[136]
Yb0.066 Co4Sb12 (300 K)	185.3	5.1	4.8	−186	480	0.1	—	—	—	—	—	[137]
Yb0.066 Co4Sb12	148.1	—	—	−259 (600 K)	465 (700 K)	0.43 (600 K)	—	—	—	—	—	[137]
Yb0.19 Co4Sb12 (300 K)	372.1	4.1	2.9	−141	1640	0.3	—	—	—	—	—	[137]
Yb0.19 Co4Sb12 (640 K)	158	—	—	−216 (640 K)	900 (640 K)	1.2	—	—	—	—	—	[137]
Yb0.3 Co4Sb12 (300 K)	434.5	3.0	1.9	−138	1986	0.4	2.8	—	44.6	3.2	—	[138]
Yb0.3 Co4Sb12 (823 K)	109.7	3.3	1.7	−199	1110	1.1	2.8	—	24.9	2.1	—	[138]
Yb0.35 Co4Sb12 (300 K)	422.6	2.9	1.8	−130	2131	0.4	3.3	—	40.1	3.4	—	[138]
Yb0.35 Co4Sb12 (823 K)	118	3.3	1.4	−193	1280	1.2	3.3	—	24.1	2.2	—	[138]
Yb0.40 Co4Sb12 (300 K)	410.6	2.9	1.6	−120	2347	0.4	3.8	—	38.5	3.3	—	[138]
Yb0.40 Co4Sb12 (823 K)	115.7	3.5	1.4	−183	1410	1.1	3.8	—	23.1	2.2	—	[138]
Yb0.5 Co4Sb12 (300 K)	385.5	2.9	1.6	−109	2540	0.3	5.0	—	31.8	3.5	—	[138]
Yb0.5 Co4Sb12 (823 K)	106.4	3.7	1.4	−170	1510	1.0	5.0	—	18.9	2.4	—	[138]
Eu0.03 Co4Sb12 (300 K)	197.1	6.2	6.0	−235	289	0.1	—	—	—	—	—	[139]
Eu0.03 Co4Sb12 (850 K)	16.3	4.1	3.5	−146	323	0.1	—	—	—	—	—	[139]
Eu0.10 Co4Sb12 (300 K)	167.2	4.1	3.8	−171	516	0.1	1.4	—	23	2.8	—	[139]
Eu0.10 Co4Sb12 (850 K)	58	3.0	2.2	−217	500	0.7	1.4	—	22.3	1.5	—	[139]
Eu0.19 Co4Sb12 (300 K)	260.1	4.2	3.3	−118	1525	0.2	4.0	—	23.7	3.4	—	[139]
Eu0.19 Co4Sb12 (850 K)	76.6	3.4	1.9	−191	893	0.8	4.0	—	13.9	2.4	—	[139]
Eu0.27 Co4Sb12 (300 K)	347.7	4.2	2.3	−87	3096	0.2	10.1	—	19.1	4.4	—	[139]
Eu0.27 Co4Sb12 (850 K)	87.4	3.6	1.2	−163	1414	0.9	10.1	—	8.7	3.4	—	[139]
Eu0.34 Co4Sb12 (300 K)	367.8	4.5	2.0	−71	4162	0.1	16.7	—	15.6	4.9	—	[139]
Eu0.34 Co4Sb12 (850 K)	98.8	4.1	0.8	−148	1910	0.9	16.7	—	7.1	4.2	—	[139]
Ce0.14 Co4Sb12 (300 K)	384.5	3.7	2.4	−121	2170	0.3	3.3	—	41	3.1	—	[140]
Ce0.14 Co4Sb12 (850 K)	121.2	3.4	1.1	−196	1333	1.3	3.3	—	25.2	2.2	—	[140]
Ce0.14 Co4Sb12 (300 K)	386.3	3.5	2.2	−121	2180	0.3	4.8	—	28.3	3.9	—	[140]
Ce0.14 Co4Sb12 (850 K)	115.7	3.2	0.9	−192	1333	1.3	4.8	—	17.3	2.7	—	[140]
Ce0.16 Co4Sb12 (300 K)	334.3	3.4	2.2	−118	1960	0.2	4.2	—	29.1	3.5	—	[140]
Ce0.16 Co4Sb12 (850 K)	101.2	3.2	1.0	−184	1280	1.2	4.2	—	19	2.3	—	[140]
Ce0.15 Co4Sb12 (300 K)	261.7	3.3	2.4	−119	1515	0.2	4.6	—	20.5	3.7	—	[140]
Ce0.15 Co4Sb12 (850 K)	102.2	3.0	1.1	−194	1150	1.2	4.6	—	15.6	2.7	—	[140]
Yb0.20 Co4Sb12 (300 K)	330	3.0	2.1	−139	1490	0.3		—			—	[140]
Yb0.20 Co4Sb12 (850 K)	101.4	3.0	1.3	−208	970	1.2		—			—	[140]
Dy0.02 Co4Sb12 (300 K)	257.9	5.3	5.2	−268	258	0.1	0.2	—	70	1.9	—	[141]
Dy0.02 Co4Sb12 (550 K, peak)	136.6	3.7	3.4	−303	226	0.3	0.2	—	61.3	1.4	—	[141]
Dy0.02 Co4Sb12 (800 K)	14.9	4.4	3.9	−131	323	0.1	0.2	—	87.7	0.2	—	[141]
Tb0.03 Co4Sb12 (300 K)	270.7	4.8	4.6	−242	366	0.1	0.4	—	65.3	2.1	—	[141]
Tb0.03 Co4Sb12 (600 K, peak)	122.3	3.3	2.9	−280	301	0.4	0.4	—	53.7	1.4	—	[141]
Tb0.03 Co4Sb12 (800 K)	30.5	4.0	3.4	−176	387	0.2	0.4	—	69	0.4	—	[141]
Gd0.04 Co4Sb12 (300 K)	336.7	4.4	4.1	−226	548	0.2	0.6	—	57	2.6	—	[141]
Gd0.04 Co4Sb12 (650 K, peak)	133.5	3.3	2.7	−265	441	0.6	0.6	—	45.9	1.6	—	[141]
Gd0.04 Co4Sb12 (800 K)	62.2	3.8	3.1	−222	462	0.5	0.6	—	48.1	0.9	—	[141]
Nd0.15 Co4Sb12 (300 K)	334.2	3.0	2.1	−133	1624	0.3	3.8	—	26.5	3.8	—	[141]
Nd0.15 Co4Sb12 (800 K, peak)	109.3	2.9	1.1	−195	1110	1.2	3.8	—	18.1	2.5	—	[141]
Sm0.15 Co4Sb12 (300 K)	421.7	3.6	2.3	−131	2100	0.3	3.1	—	41.7	3.3	—	[141]
Sm0.15 Co4Sb12 (800 K, peak)	121.3	2.9	1.1	−204	1110	1.3	3.1	—	22.1	2.4	—	[141]
Ba0.03 Co4Sb12.05 (300 K)	228.7	5.4	5.1	−220	399	0.1	0.5	—	49.8	2.2	—	[142]
Ba0.03 Co4Sb12.05 (800 K)	24.5	3.8	3.3	−161	370	0.2	0.5	—	46.2	0.5	—	[142]
Ba0.15Yb0.01 Co4Sb12.08 (300 K)	333.4	4.3	3.0	−125	1789	0.2	2.8	—	39.9	2.9	—	[142]
Ba0.15Yb0.01 Co4Sb12.08 (800 K)	92.9	3.6	2.0	−190	1000	0.8	2.8	—	22.3	2.0	—	[142]
Ba0.11Yb0.03 Co4Sb12.07 (300 K)	293.3	3.2	1.9	−115	1787	0.2	3.7	—	30.1	3.1	—	[142]
Ba0.11Yb0.03 Co4Sb12.07 (800 K)	89.9	3.1	1.3	−179	1100	0.9	3.7	—	18.6	2.2	—	[142]
Yb0.12 Co4Sb12.11 (300 K)	184.3	2.7	2.2	−146	765	0.2	2.3	—	20.8	3.1	—	[142]
Yb0.12 Co4Sb12.11 (800 K)	89.5	2.7	1.6	−220	680	1.0	2.3	—	18.5	2.2	—	[142]
Ba0.05Yb0.09 Co4Sb12.13 (300 K)	313	2.8	2.0	−158	1126	0.3	2.9	—	24.2	4.0	—	[142]
Ba0.05Yb0.09 Co4Sb12.13 (800 K)	119.4	2.6	1.4	−233	780	1.3	2.9	—	16.8	2.9	—	[142]
Ba0.08Yb0.09 Co4Sb12.12 (300 K)	390.2	2.5	1.0	−126	2068	0.4	3.2	—	40.3	3.2	—	[142]
Ba0.08Yb0.09 Co4Sb12.12 (800 K)	107.7	2.5	0.6	−190	1160	1.4	3.2	—	22.6	2.2	—	[142]
Ba0.11Yb0.08 Co4Sb12.08 (300 K)	312.5	2.4	0.9	−107	2114	0.3	4.4	—	30	3.2	—	[142]
Ba0.11Yb0.08 Co4Sb12.08 (800 K)	89.4	2.3	0.5	−177	1120	1.2	4.4	—	15.9	2.4	—	[142]
Ba0.25 Co4Sb11.91 (300 K)	312.4	5.6	4.9	−145	1312	0.2	2.0	—	40.3	2.8	—	[143]
Ba0.25 Co4Sb11.91 (850 K)	67.3	4.5	3.2	−192	775	0.5	2.0	—	23.8	1.5	—	[143]
Ba0.21In0.04 Co4Sb11.93 (300 K)	408.2	3.4	2.5	−160	1434	0.3	1.7	—	51.7	2.9	—	[143]
Ba0.21In0.04 Co4Sb11.93 (850 K)	83.8	2.9	1.6	−209	792	1.0	1.7	—	28.6	1.6	—	[143]
Ba0.19In0.07 Co4Sb11.85 (300 K)	414.2	3.0	2.0	−151	1619	0.4	1.8	—	57.1	2.7	—	[143]
Ba0.19In0.07 Co4Sb11.85 (850 K)	88.1	2.8	1.2	−199	935	1.1	1.8	—	33	1.5	—	[143]
Ba0.16In0.12 Co4Sb11.85 (300 K)	400	2.8	1.8	−143	1721	0.4	2.2	—	50	2.9	—	[143]
Ba0.16In0.12 Co4Sb11.85 (850 K)	86.5	2.6	1.0	−194	973	1.2	2.2	—	28.2	1.6	—	[143]
Ba0.15In0.16 Co4Sb11.83 (300 K)	405	2.7	1.6	−139	1829	0.4	2.7	—	42.3	3.2	—	[143]
Ba0.15In0.16 Co4Sb11.83 (850 K)	94.2	2.5	0.9	−200	989	1.3	2.7	—	22.9	2.0	—	[143]
Ba0.15In0.20 Co4Sb11.84 (300 K)	405.7	2.8	1.8	−140	1810	0.4	2.9	—	39.6	3.4	—	[143]
Ba0.15In0.20 Co4Sb11.84 (850 K)	90.9	2.8	1.1	−198	977	1.2	2.9	—	21.4	2.0	—	[143]
Ba0.14In0.23 Co4Sb11.84 (300 K)	376.1	2.6	1.5	−128	1944	0.4	4.8	—	25.2	4.2	—	[143]
Ba0.14In0.23 Co4Sb11.84 (850 K)	95	2.6	0.7	−190	1120	1.3	4.8	—	14.5	2.7	—	[143]
Ba0.06La0.05Yb0.06 Co4Sb12 (300 K)	400.8	3.0	1.9	−138	1832	0.4	2.4	—	47.8	2.9	—	[144]
Ba0.06La0.05Yb0.06 Co4Sb12 (850 K)	113.2	2.9	1.1	−211	1046	1.4	2.4	—	27.3	2.0	—	[144]
Ba0.08La0.05Yb0.08 Co4Sb12 (300 K)	452.5	2.7	1.3	−126	2398	0.4	3.7	—	40.9	3.5	—	[144]
Ba0.08La0.05Yb0.08 Co4Sb12 (850 K)	125.1	2.6	0.4	−198	1344	1.7	3.7	—	22.9	2.4	—	[144]
Ba0.10La0.05Yb0.10 Co4Sb12 (300 K)	443.5	3.1	1.3	−107	3000	0.3	5.0		37.8	3.4		[144]
Ba0.10La0.05Yb0.10 Co4Sb12 (850 K)	130.5	3.0	0.3	−185	1631	1.6	5.0	—	20.6	2.6	—	[144]
Ba0.10La0.05Yb0.15 Co4Sb12 (300 K)	434.3	3.0	1.2	−104	3058	0.3	5.5	—	34.6	3.6	—	[144]
Ba0.10La0.05Yb0.15 Co4Sb12 (850 K)	120.7	3.2	0.3	−174	1715	1.4	5.5	—	19.4	2.5	—	[144]
Ba0.10La0.05Yb0.20 Co4Sb12 (300 K)	411.6	3.0	1.0	−93	3367	0.3	7.6	—	27.5	3.9	—	[144]
Ba0.10La0.05Yb0.20 Co4Sb12 (850 K)	121.3	3.4	0.1	−164	1938	1.3	7.6	—	15.8	2.9	—	[144]
Co4Sb11.46Te0.43 (300 K)	293.9	4.9	3.9	−120	1680	0.2	5.6	—	18.5	4.3	—	[145]
Co4Sb11.46Te0.43 (850 K)	102.6	3.7	2.0	−203	1040	1.0	5.6	—	11.5	3.3	—	[145]
S0.26 Co4Sb11.11Te0.73 (300 K)	239.9	2.2	1.5	−137	1110	0.3	3.1	—	22.1	3.5	—	[145]
S0.26 Co4Sb11.11Te0.73 (850 K)	98.5	2.2	0.9	−221	810	1.5	3.1	—	16.3	2.6	—	[145]
Se0.17 Co4Sb11.31Te0.53 (300 K)	243.4	3.0	2.4	−142	1060	0.2	3.2	—	20.4	3.7	—	[145]
Se0.17 Co4Sb11.31Te0.53 (850 K)	91.3	2.5	1.3	−220	760	1.2	3.2	—	14.7	2.6	—	[145]
Br0.16 Co4Sb11.34Te0.52 (300 K)	288.2	4.2	3.4	−136	1350	0.2	3.7	—	22.5	3.8	—	[145]
Br0.16 Co4Sb11.34Te0.52 (850 K)	94	3.2	1.6	−207	910	1.1	3.7	—	15.2	2.6	—	[145]
S0.18 Co3.4Ni0.58Sb11.94 (300 K)	126.6	2.9	2.2	−90	1080	0.1	16.0	—	4.2	6.2	—	[145]
S0.18 Co3.4Ni0.58Sb11.94 (850 K)	67.3	3.4	1.7	−171	990	0.7	16.0	—	3.8	5.0	—	[145]
Se0.03 Co4Sb11.94Se0.06 (300 K)	305.5	5.3	5.2	−361	104	0.1	0.3	0.3	24.7	4.4	—	[146]
Se0.03 Co4Sb11.94Se0.06 (600 K, peak)	100.2	3.4	3.2	−334	132	0.3	0.3	—	31.3	1.8	—	[146]
Se0.03 Co4Sb11.94Se0.06 (800 K)	12.8	4.1	3.7	−152	215	0.1	0.3	—	51	0.3	—	[146]
Se0.05 Co4Sb11.9Se0.1 (300 K)	222.1	4.1	4.1	−354	82	0.1	0.4	0.4	14.1	5.1	—	[146]
Se0.05 Co4Sb11.9Se0.1 (600 K, peak)	115.9	2.9	2.8	−354	121	0.3	0.4	—	20.9	2.6	—	[146]
Se0.05 Co4Sb11.9Se0.1 (800 K)	16.5	3.5	3.1	−172	219	0.2	0.4	—	37.8	0.4	—	[146]
Se0.1 Co4Sb11.8Se0.2 (300 K)	128.7	3.3	3.2	−327	65	0.1	0.4	0.4	9.2	4.7	—	[146]
Se0.1 Co4Sb11.8Se0.2 (600 K, peak)	68	2.4	2.3	−328	96	0.3	0.4	—	13.6	2.4	—	[146]
Se0.1 Co4Sb11.8Se0.2 (800 K)	15.8	3.0	2.7	−175	202	0.2	0.4	—	28.7	0.5	—	[146]
Se0.15 Co4Sb11.7Se0.3 (300 K)	111.5	2.5	2.5	−300	77	0.1	0.7	0.7	7.1	5.1	—	[146]
Se0.15 Co4Sb11.7Se0.3 (600 K, peak)	82.1	2.0	1.9	−339	102	0.4	0.7	—	9.4	3.5	—	[146]
Se0.15 Co4Sb11.7Se0.3 (800 K)	24.9	2.6	2.2	−214	203	0.3	0.7	—	18.8	0.9	—	[146]
Se0.2 Co4Sb11.6Se0.4 (300 K)	87.7	2.2	2.1	−262	94	0.1	1.2	0.4	4.8	5.5	—	[146]
Se0.2 Co4Sb11.6Se0.4 (600 K, peak)	77.1	1.9	1.8	−324	114	0.4	1.2	—	5.8	4.6	—	[146]
Se0.2 Co4Sb11.6Se0.4 (800 K)	27.6	2.6	2.2	−218	215	0.3	1.2	—	11	1.4	—	[146]
Se0.3 Co4Sb11.4Se0.6 (300 K)	66.6	2.2	2.1	−213	126	0.1	1.6	0.3	4.8	4.5	—	[146]
Se0.3 Co4Sb11.4Se0.6 (750 K, peak)	36.1	2.3	1.9	−233	214	0.4	1.6	—	8.2	2.1	—	[146]
Se0.3 Co4Sb11.4Se0.6 (800 K)	30.7	2.5	2.1	−212	256	0.4	1.6	—	9.8	1.7	—	[146]
Pd0.20(±0.03) Co3.80Sb12.01(±0.07) (300 K)	435.2	5.6	4.9	−177	1252	0.2	2.1	0.3	38.1	3.8	—	[147]
Pd0.20(±0.03) Co3.80Sb12.01(±0.07) (700 K)	126.1	4.2	3.0	−217	812	0.6	2.1	—	24.7	2.3	—	[147]
Pd0.20(±0.03) Co3.80Sb12.01(±0.07) (850 K)	77	4.6	3.3	−203	781	0.6	2.1	—	23.8	1.7	—	[147]
S0.02(±0.01)Pd0.20(±0.02) Co3.80Sb12.06(±0.07) (300 K)	423.9	4.1	3.4	−186	1098	0.3	1.6	0.3	43.4	3.5	—	[147]
S0.02(±0.01)Pd0.20(±0.02) Co3.80Sb12.06(±0.07) (700 K)	133.9	3.5	2.5	−233	716	0.8	1.6	—	28.3	2.2	—	[147]
S0.02(±0.01)Pd0.20(±0.02) Co3.80Sb12.06(±0.07) (850 K)	78.9	4.0	2.8	−214	704	0.7	1.6	—	27.8	1.6	—	[147]
S0.04(±0.01)Pd0.20(±0.01) Co3.80Sb11.99(±0.08) (300 K)	341	3.7	3.2	−189	853	0.3	1.4	0.3	39.2	3.2	—	[147]
S0.04(±0.01)Pd0.20(±0.01) Co3.80Sb11.99(±0.08) (700 K)	123.2	3.3	2.4	−244	580	0.7	1.4	—	26.6	2.2	—	[147]
S0.04(±0.01)Pd0.20(±0.01) Co3.80Sb11.99(±0.08) (850 K)	67.6	3.8	2.8	−216	589	0.6	1.4	—	27	1.4	—	[147]
S0.08(±0.01)Pd0.20(±0.02) Co3.80Sb12.04(±0.11) (300 K)	310.3	3.3	2.9	−212	594	0.2	1.0	0.3	36.4	3.3	—	[147]
S0.08(±0.01)Pd0.20(±0.02) Co3.80Sb12.04(±0.11) (600 K)	144.8	2.9	2.4	−262	439	0.6	1.0	—	26.9	2.5	—	[147]
S0.08(±0.01)Pd0.20(±0.02) Co3.80Sb12.04(±0.11) (850 K)	52.7	3.6	2.8	−213	476	0.5	1.0	—	29.1	1.2	—	[147]
S0.05(±0.01)Pd0.15(±0.01) Co3.85Sb12.03(±0.14) (300 K)	356.4	3.7	3.4	−226	580	0.2	0.8	0.3	45.8	3.1	—	[147]
S0.05(±0.01)Pd0.15(±0.01) Co3.85Sb12.03(±0.14) (600 K)	162.5	3.1	2.6	−276	419	0.6	0.8	—	33.1	2.3	—	[147]
S0.05(±0.01)Pd0.15(±0.01) Co3.85Sb12.03(±0.14) (850 K)	44.5	3.9	3.1	−202	456	0.4	0.8	—	36	0.9	—	[147]
S0.04(±0.01)Pd0.21(±0.02) Co3.75Sb11.92(±0.09) (300 K)	405.3	3.4	2.8	−192	979	0.3	2.1	0.3	29.5	4.4	—	[147]
S0.04(±0.01)Pd0.21(±0.02) Co3.75Sb11.92(±0.09) (700 K)	139.5	3.1	2.3	−244	657	0.9	2.1		19.8	3.4	—	[147]
S0.04(±0.01)Pd0.21(±0.02) Co3.75Sb11.92(±0.09) (850 K)	76.1	3.7	2.6	−216	663	0.7	2.1		20	1.9	—	[147]
CeFe4As12	—	—	—	—	—	—	—	0.2	—	—	34.4 (static)	[159]
CeFe4Sb12	—	—	—	—	—	—	—	0.1	—	—	39.8 (static)	[159]
CoSb3	—	—	—	—	—	—	—	—	—	—	∞ = 31.67	[160]
TlFeCo3Sb12	—	—	—	—	—	—	—	—	—	—	∞ = 38.57	[160]
CoSb3	—	—	—	—	—	—	—	—	—	—	∞ = 25.6 (130 K), ∞ = 24.3 (623 K)	[161]
UFe4P12	—	—	—	—	—	—	—	—	—	—	∞ = 17	[162]
CeFe4P12	—	—	—	—	—	—	—	—	—	—	∞ = 31	[162]
LaFe3 CoSb12 (300 K)	87.6	1.6	1.3	103	625	0.1		—	—	—	—	[148]
LaFe3 CoSb12	55.3	1.6 (740 K)	1.0 (740 K)	203 (700 K)	455 (700 K)	0.9 (740 K)		—	—	—	—	[148]
CeFe3 CoSb12 (300 K)	74.9	—	—	87	667	—	—	—	—	—	—	[148]
CeFe3 CoSb12	37.6	—	—	150 (680 K)	508 (680 K)	0.7 (800 K)	—	—	—	—	—	[148]
CeFe2.5 Co1.5Sb12 (300 K)	51.8	—	—	105	360	—	—	0.43	—	—	—	[148]
CeFe2.5 Co1.5Sb12 (680 K)	25.7	—	—	161	304	—	—	—	—	—	—	[148]
La0.89Fe4Sb12.02 (300 K)	241.3	3.1	1.6	78.3	2440	0.2	13.8	—	11	4.8		[151]
La0.89Fe4Sb12.02 (800 K)	81.3	3.4	1.1	150	1400	0.8	13.8	—	6.3	4.0		[151]
Ce0.91Fe4Sb11.97 (300 K)	224.2	2.6	1.3	79.4	2230	0.2	38.6	—	3.6	9.7	—	[151]
Ce0.91Fe4Sb11.97 (800 K)	86.8	3.1	0.8	152	1460	0.9	38.6	—	2.4	8.0	—	[151]
Pr0.90Fe4Sb12.00 (300 K)	248.9	2.5	1.1	81.5	2400	0.2	71.9	—	2.1	15.1	—	[151]
Pr0.90Fe4Sb12.00 (800 K)	84.4	3.0	0.8	152	1420	0.9	71.9	—	1.2	12.2	—	[151]
Nd0.85Fe4Sb12.00 (300 K)	253.8	2.4	1.0	83.7	2370	0.2	46.6	—	3.2	11.6	—	[151]
Nd0.85Fe4Sb12.00 (800 K)	84.6	3.0	0.7	151	1440	0.9	46.6	—	1.9	9.0	—	[151]
Eu0.96Fe4Sb11.94 (300 K)	261.7	3.6	1.8	70.8	2970	0.1	34.3	—	5.4	7.9	—	[151]
Eu0.96Fe4Sb11.94 (800 K)	79	4.0	1.0	124	1870	0.6	34.3	—	3.4	5.6	—	[151]
Yb0.94Fe4Sb12.07 (300 K)	330.3	3.2	1.2	77.9	3360	0.2	25.4	—	8.3	7.2	—	[151]
Yb0.94Fe4Sb12.07 (800 K)	93.1	4.4	0.9	123	2230	0.6	25.4	—	5.5	4.6	—	[151]
Ca0.98Fe4Sb12.08 (300 K)	290.4	3.5	1.6	73.9	3140	0.2	13.4	—	14.6	4.4	—	[151]
Ca0.98Fe4Sb12.08 (800 K)	84.3	4.2	0.9	123	2020	0.6	13.4	—	9.4	3.0	—	[151]
Sr0.94Fe4Sb12.08 (300 K)	303.2	4.1	2.1	72.5	3350	0.1	33.6	—	6.2	8.0	—	[151]
Sr0.94Fe4Sb12.08 (800 K)	86.5	4.5	1.1	122	2100	0.6	33.6	—	3.9	5.4	—	[151]
Ba0.92Fe4Sb12.04 (300 K)	265.4	4.0	2.2	69.4	3080	0.1	16.1	—	11.9	4.7	—	[151]
Ba0.92Fe4Sb12.04 (800 K)	74.8	4.4	1.2	116	1960	0.5	16.1	—	7.6	3.1	—	[151]
Ce0.2FeCo3Sb12 (300 K)	80.2	2.0	1.7	106	550	0.1	1.3	—	26.4	1.4	—	[152]
Ce0.2FeCo3Sb12 (700 K, peak)	42	2.2	1.7	193	357	0.4	1.3	—	17.1	1.4	—	[152]
Ce0.2FeCo3Sb12 (800 K)	31.6	2.5	1.9	182	373	0.4	1.3	—	17.9	1.1	—	[152]
Ce0.5Fe2 Co2Sb12 (300 K)	105.1	1.8	1.4	102	760	0.1	8.0	—	5.9	4.5	—	[152]
Ce0.5Fe2 Co2Sb12 (700 K, peak)	64.8	2.0	1.3	190	571	0.7	8.0	—	4.5	4.5	—	[152]
Ce0.5Fe2 Co2Sb12 (800 K)	41.9	2.3	1.4	171	563	0.6	8.0	—	4.4	3.4	—	[152]
Ce0.9Fe3 CoSb12 (300 K)	161	1.9	1.3	112	1020	0.2	23.3	—	2.7	10.2	—	[152]
Ce0.9Fe3 CoSb12 (700 K, peak)	81.5	2.0	0.9	184	770	0.9	23.3	—	2.1	8.8	—	[152]
Ce0.9Fe3 CoSb12 (800 K)	64.7	2.4	1.2	185	738	0.9	23.3	—	2	7.8	—	[152]
CeFe4Sb12 (300 K)	222.9	2.6	1.3	79	2230	0.2		—			—	[152]
CeFe4Sb12 (775 K, peak)	86.9	3.1	0.8	147	1480	0.8		—			—	[152]
CeFe4Sb12 (800 K)	81.3	3.1	0.8	146	1470	0.8		—			—	[152]
Yb0.3FeCo3Sb12 (300 K)	78.9	2.2	1.7	80	778	0.1	1.4	—	34.7	1.1	—	[152]
Yb0.3FeCo3Sb12 (700 K, peak)	52.7	2.0	1.1	164	630	0.6	1.4	—	28.1	1.1	—	[152]
Yb0.3FeCo3Sb12 (800 K)	44	2.4	1.3	165	634	0.6	1.4	—	28.3	1.0	—	[152]
Yb0.5Fe1.5 Co2.5Sb12 (300 K)	130.3	2.0	1.4	103	930	0.2	2.9	—	20	2.3	—	[152]
Yb0.5Fe1.5 Co2.5Sb12 (700 K, peak)	67.3	1.9	0.9	171	740	0.8	2.9	—	15.9	2.0	—	[152]
Yb0.5Fe1.5 Co2.5Sb12 (800 K)	53.3	2.3	1.1	173	700	0.7	2.9	—	15.1	1.7	—	[152]
Yb0.7Fe2 Co2Sb12 (300 K)	152.1	1.9	1.2	102	1100	0.2	7.5	—	9.2	4.3	—	[152]
Yb0.7Fe2 Co2Sb12 (700 K, peak)	73.7	2.0	0.8	166	860	0.8	7.5	—	7.2	3.5	—	[152]
Yb0.7Fe2 Co2Sb12 (800 K)	60	2.3	1.0	168	835	0.8	7.5	—	6.9	3.1	—	[152]
Yb0.9Fe2.5 Co1.5Sb12 (300 K)	221	2.4	1.5	107	1495	0.2	9.2	—	10.1	5.2	—	[152]
Yb0.9Fe2.5 Co1.5Sb12 (700 K, peak)	88.3	2.5	1.0	162	1080	0.8	9.2	—	7.3	3.9	—	[152]
Yb0.9Fe2.5 Co1.5Sb12 (800 K)	71.6	3.0	1.4	166	1020	0.8	9.2	—	6.9	3.5	—	[152]
YbFe3 CoSb12 (300 K)	237.5	2.5	1.4	92	1970	0.2	16.4	—	7.5	6.4	—	[152]
YbFe3 CoSb12 (700 K, peak)	101.2	2.7	0.8	151	1410	0.8	16.4	—	5.4	5.1	—	[152]
YbFe3 CoSb12 (800 K)	80.6	3.1	0.9	153	1340	0.8	16.4	—	5.1	4.6	—	[152]
YbFe3.5 Co0.5Sb12 (300 K)	242.4	3.1	1.6	77	2500	0.2		—			—	[152]
YbFe3.5 Co0.5Sb12 (700 K, peak)	92	3.6	1.0	121	1850	0.5		—			—	[152]
YbFe3.5 Co0.5Sb12 (800 K)	71.8	4.0	1.3	123	1720	0.5		—			—	[152]
BaFe3 CoSb12 (300 K)	220.2	3.6	2.4	85.6	2000	0.1	17.8	—	7	6.3	—	[153]
BaFe3 CoSb12 (800 K)	76.7	3.3	1.3	154	1260	0.7	17.8	—	4.4	4.9	—	[153]
Ce0.9Fe3 CoSb12 (300 K)	172.5	2.0	1.4	111.5	1100	0.2	23.1	—	3	10.1	—	[153]
Ce0.9Fe3 CoSb12 (750 K, peak)	76.4	2.2	1.0	183	810	0.9	23.1	—	2.2	8.1	—	[153]
Ce0.9Fe3 CoSb12 (800 K)	68.3	2.4	1.2	184	788	0.9	23.1	—	2.1	7.6	—	[153]
YbFe3 CoSb12 (300 K)	235.5	2.5	1.3	91.4	1970	0.2	16.4	—	7.5	6.4	—	[153]
YbFe3 CoSb12 (700 K, peak)	99.5	2.7	0.7	149	1420	0.8	16.4	—	5.4	5.0	—	[153]
YbFe3 CoSb12 (800 K)	79.7	3.1	0.9	152	1340	0.8	16.4	—	5.1	4.5	—	[153]
Ba0.4Ce0.6Fe3 CoSb12 (300 K)	160.5	2.0	1.2	93.7	1300	0.2	13.9	—	5.8	5.9	—	[153]
Ba0.4Ce0.6Fe3 CoSb12 (750 K, peak)	63.9	2.2	0.8	160	888	0.8	13.9	—	4	4.7	—	[153]
Ba0.4Ce0.6Fe3 CoSb12 (800 K)	58.9	2.3	1.0	163	869	0.8	13.9	—	3.9	4.5	—	[153]
Ce0.45Nd0.45Fe3 CoSb12 (300 K)	191.7	1.8	1.1	108.6	1270	0.3	29.7	—	2.7	11.6	—	[153]
Ce0.45Nd0.45Fe3 CoSb12 (750 K, peak)	83.7	2.1	0.8	182	898	1.1	29.7	—	1.9	9.5	—	[153]
Ce0.45Nd0.45Fe3 CoSb12 (800 K)	72.2	2.3	0.8	178	894	1.0	29.7	—	1.9	8.6	—	[153]
Ce0.6Yb0.4Fe3 CoSb12 (300 K)	193.5	1.9	1.1	105.8	1330	0.2	20.8	—	4	8.9	—	[153]
Ce0.6Yb0.4Fe3 CoSb12 (750 K, peak)	79.7	2.1	0.7	173	950	1.0	20.8	—	2.9	6.9	—	[153]
Ce0.6Yb0.4Fe3 CoSb12 (800 K)	69.6	2.3	0.8	172	925	0.9	20.8	—	2.8	6.4	—	[153]
Ce0.4Yb0.6Fe3 CoSb12 (300 K)	192.3	1.8	1.0	103.1	1370	0.2	16.0	—	5.3	7.2	—	[153]
Ce0.4Yb0.6Fe3 CoSb12 (750 K, peak)	76.3	2.1	0.6	167	975	1.0	16.0	—	3.8	5.5	—	[153]
Ce0.4Yb0.6Fe3 CoSb12 (800 K)	66.3	2.3	0.8	165	956	0.9	16.0	—	3.7	5.0	—	[153]
DD0.86Fe4Sb12 (300 K)	301.4	2.2	0.5	85	2762	0.3	—	—			—	[154]
DD0.86Fe4Sb12 (800 K)	91.3	2.9	0.6	157	1447	1.1	—	—			—	[154]
DD0.78Fe3.2 Co0.8Sb12 (300 K)	300	2.0	0.3	83	2830	0.3	2.8	—	64	1.8	—	[154]
DD0.78Fe3.2 Co0.8Sb12	97.7	3.1 (675 K)	—	152 (800 K)	1643 (800 K)	—	—	—	—	—	—	[154]
DD0.44Fe2.1 Co1.9Sb12 (300 K)	185.1	1.9	1.2	103	1321	0.2	3.4	—	24.3	2.6	—	[154]
DD0.44Fe2.1 Co1.9Sb12	53.6	2.8 (725 K)	—	159 (800 K)	830 (800 K)	0.4 (800 K)	—	—			—	[154]
DD0.25Fe1.2 Co2.8Sb12 (300 K)	153.2	2.7	2.0	98	1170	0.1	1.7	—	43.5	1.5	—	[154]
DD0.25Fe1.2 Co2.8Sb12	65.2	3.4 (775 K)	—	198 (800 K)	640 (800 K)	0.4 (800 K)	—	—	—	—	—	[154]
DD0.12FeCo3Sb12 (300 K)	111.7	3.5	2.7	69	1305	0.1	1.5	—	52.9	1.0	—	[154]
DD0.12FeCo3Sb12	85.1	4.4 (675 K)	—	168 (800 K)	1076 (750 K)	0.5 (800 K)	—	—	—	—	—	[154]
DD0.08FeCo3Sb12 (300 K)	166.6	3.4	3.3	−228	265	0.1	1.0	—	16.5	3.7	—	[154]
DD0.08FeCo3Sb12	49.3	4.88 (775 K)	—	−230 (750 K)	303 (800 K)	0.3 (800 K)	—	—	—	—	—	[154]
DD0.68Fe3.2Ni0.8Sb12 (300 K)	304.9	2.3	1.4	132	1500	0.3	0.8	—	117	1.3	—	[154]
DD0.68Fe3.2Ni0.8Sb12 (800 K)	104.7	2.9	2.4	211	883	1.1	0.8	—	68.9	2.7	—	[154]
DD0.76Fe3.4Ni0.6Sb12 (300 K)	251.1	2.0	0.8	94	2026	0.3	1.4	—	89.7	1.3	—	[154]
DD0.76Fe3.4Ni0.6Sb12 (800 K)	81.6	2.8	2.0	155	1325	0.9	1.4	—	58.7	2.4	—	[154]
DD0.40Fe2.8Ni1.2Sb12 (300 K)	54.4	2.1	2.0	135	258	0.1	0.5	—	32.9	1.0	—	[154]
DD0.40Fe2.8Ni1.2Sb12 (800 K)	5.3	3.4	2.8	20	957	0.01	0.5	—	121.9	0.1	—	[154]
DD0.08Fe2Ni2Sb12 (300 K)	23.2	2.2	2.0	−70	267	0.02	0.7	—	23.5	0.6	—	[154]
DD0.08Fe2Ni2Sb12 (800 K)	108.4	4.3	0.6	−62	6200	0.4	0.7	—	545.1	0.5	—	[154]
Sr0.03Ba0.03Yb0.1 Co4Sb12 (300 K)	357.5	2.7	1.7	−138	1634	0.4	—	—	—	—	—	[149]
Sr0.03Ba0.03Yb0.1 Co4Sb12 (800 K)	121	2.8	1.3	−217	952	1.3	—	—	—	—	—	[149]
Sr0.07Ba0.07Yb0.07 Co4Sb12 (300 K)	376.8	2.3	1.3	−140	1681	0.4	—	—	—	—	—	[149]
Sr0.07Ba0.07Yb0.07 Co4Sb12 (800 K)	111.1	2.4	0.9	−208	970	1.4	—	—	—	—	—	[149]
Sr0.07Ba0.07Yb0.07 Co4Sb12 (300 K), HPT	260.7	1.6	0.9	−140	1163	0.4	—	—	—	—	—	[149]
Sr0.07Ba0.07Yb0.07 Co4Sb12 (800 K), HPT	103.8	1.8	0.4	−213	855	1.8	—	—	—	—	—	[149]
DD0.88Fe4Sb12 (300 K)	279.8	1.9	0.4	85	2564	0.3	—	—	—	—	—	[155]
DD0.88Fe4Sb12 (800 K)	105.4	3.2	0.6	160	1613	1.1	—	—	—	—	—	[155]
Mm0.68Fe4Sb12 (300 K)	202.4	1.4	0.6	110	1316	0.3	—	—	—	—	—	[155]
Mm0.68Fe4Sb12 (800 K)	81	2.1	0.7	188	893	1.2	—	—	—	—	—	[155]
DD0.60Fe3 CoSb12 (300 K)	187	1.8	1.1	106	1282	0.2	—	—	—	—	—	[155]
DD0.60Fe3 CoSb12 (800 K)	79.4	1.9	0.5	183	927	1.3	—	—	—	—	—	[155]
DD0.88Fe4Sb12 (300 K)	279.8	1.9	0.4	85	2564	0.3	—	—	—	—	—	[155]

For simplicity, the carrier concentration values at high temperature are taken as the same values at room temperature to calculate the m* in this table.

Cobalt antimonide (CoSb₃) based filled skutterudites are reported to show excellent thermoelectric performance among the skutterudite family [128–149]. When rare earth, alkaline earths, or alkali metals are accommodated in the Sb-icosahedral voids without additional charge compensation, the resulting filled skutterudites G_y Co₄Sb₁₂ usually show n-type conductivity due to the extra electrons introduced into the [Co₄Sb₁₂] framework by the filler, while the fillers hardly modify the band structure near the conduction band minimum. The maximum filling fraction increases with the type of filler, roughly following the sequence of rare earths, alkaline earths, and alkali metals, although it is also affected by the electronegativity, radius, and valence of the filler ions. The optimal filling fraction for maximum power factors (PFs) roughly obeys a '0.5 electron per unit cell' rule, in which the carrier concentration reaches ∼10²⁰ cm⁻³ [150]. Binary CoSb₃ has an intrinsic high κ_L of about ∼10 Wm⁻¹K⁻¹ at 300 K. Introducing foreign elements into the Sb-icosahedral voids can greatly lower κ_L due to the filler-introduced resonant scattering of phonons. One important realization is that these resonant scattering centers are tuned to a particular spectrum of phonons. By filling the voids with different types of elements possessing different resonant frequencies, it enables phonons with a broad range of frequencies to be scattered, leading to a significant reduction of lattice thermal conductivity in the so-called multiple-filled skutterudites. With comprehensive strategies, combining the optimization of carrier concentration by optimizing the filling fraction, the reduction of κ_L through multiple-filling, as well as the introduction of magnetic nanocomposites, the maximum zT has been enhanced to a very high level, exceeding 1.7 in CoSb₃-based n-type filled skutterudites [144, 149].

It is easy to obtain p-type filled skutterudites by alloying Fe at the Co-site or Ge/Sn at the Sb-site in G_y Co₄Sb₁₂. G_y Co_4−x Fe_x Sb₁₂ (where x is the Fe doping content) represents one of the most promising p-type filled skutterudites [149, 151–157]. The x in G_y Co_4−x Fe_x Sb₁₂ is usually in the range of 1.5–4. The maximum filling fraction y in G_y Co_4−x Fe_x Sb₁₂ is usually less than x/n, where n is the valence state of fillers. In G_y Fe₄Sb₁₂, the electrical transport is sensitively dependent on the valence states of the fillers, while the lattice thermal resistivity W_L (=1/κ_L ) obeys the relationship of W_L ∼ (r_cage–r_ion)³, where r_cage and r_ion are the radii of Sb-icosahedron void and filler, respectively [151]. It should be noted that the Sb in p-type filled skutterudites is easier to volatilize at elevated temperature than in n-type filled skutterudites, thus the maximum measurement temperature for p-type filled skutterudites is usually around 800 K, about 50–100 K lower than that for n-type filled skutterudites. The maximum zT is around unity for p-type G_y Co_4−x Fe_x Sb₁₂, which is much lower than for n-type G_y Co₄Sb₁₂ (figure 3(b)) [151–153].

Figures 3(b)–(f) present the collected physical properties (electrical conductivity, thermal conductivity, Seebeck coefficient, and carrier mobility) and thermoelectric parameters (PF and zT) of p—and n-type skutterudites at 300 K [128–149, 151–157]. These parameters are plotted as the dependencies of electrical conductivity or carrier concentration. All these dependencies show similar trends even at high temperature. As shown in figure 3(b), at 300 K, the zTs of p-type skutterudites are smaller than those for n-type materials across the whole range of electrical conductivity (σ), although the optimal electrical conductivity for peak zT takes occurs in the same range, around 1500–2500 S cm⁻¹. The disparity between the optimal zT values of n- and p-type skutterudites is numerically determined by the different levels of PF as shown in figure 3(c). For example, the maximum PF for n-type skutterudites at 300 K is approximately 40 μW cm⁻¹K⁻², while that for p-type materials is only around 20 μW cm⁻¹K⁻².

Generally, the weighted mobility μ_w (=μ₀(m*/m₀)^3/2, where μ₀ is the drift mobility and m* is the density-of-state effective mass) is an important factor to discuss the PF. Since the m* varies with the variation of carrier concentration in skutterudites, it is difficult to achieve a satisfactory fit to all data by using fixed μ_w, but the general trend should be valuable and meaningful from the estimated μ_w [158]. In figure 3(c), the PF—σ lines for n- and p-type skutterudites are drawn using the estimated μ_w (335 cm²V⁻¹s⁻¹ and 225 cm²V⁻¹s⁻¹ for n- and p-type skutterudites, respectively, estimated from all collected data) and m* (5m_e and 12m_e, for n- and p-type, respectively, estimated from all collected data). As shown in figures 1(d) and (e), the much larger μ_H guarantees the larger PFs for n-type skutterudites although their m* values are smaller than in p-type ones. This scenario is consistent with analyses based on band structure. For n-type skutterudites, the conduction band edge is dominated by the Sb-dominated threefold degenerated bands. However, for p-type skutterudites, there is one Sb-dominated light band and one Fe-dominated heavy band in the valence band edge. Considering the heavily doped character of G_y Co_4−x Fe_x Sb₁₂, the Fermi level crosses the Fe-dominated heavy band. The localized nature of Fe 3d orbitals is responsible for the large m* but small μ₀ observed in p-type skutterudites. This implies that, efforts to optimize the band structure through exploring new alloy systems (if possible) to enhance the carrier mobility may be worthwhile for the development of p-type filled skutterudites with higher thermoelectric performance.

Figure 3(f) shows that the p-type (filled) skutterudites generally exhibit lower total thermal conductivity (κ) and κ_L than the n-type (filled) skutterudites under the comparable range of σ. This is reasonable since the p-type skutterudites usually possess higher filling fractions, which can lead to stronger scattering of phonons. In addition, the coexistence of Fe and Co at the same atomic site introduces extra point defects to scatter phonons, which are also responsible for the lower κ_L values observed in p-type skutterudites. However, in figure 3(f), it can be seen that many n-type samples exhibit comparable κ to the p-type samples in the optimal σ range. It is noted that these low κ values are obtained in the multiple-filled skutterudites. The combination of the low κ and reduced influence on electrical transport by multiple-filling guarantees the realization of high zT in n-type filled skutterudites.

Although skutterudites have been widely studied in the aspects of both material optimization and device development, there are still great challenges for skutterudite thermoelectrics. Firstly, the current TE performance of p-type skutterudites is behind that of the n-type skutterudites, which limits the development of high efficiency devices. Considering that the localized 3d orbitals of Fe is the main reason for the low carrier mobilities and poor zTs of existing p-type skutterudites, alternative doping elements should be explored to develop new p-type skutterudites. Secondly, the κ_L of n-type skutterudites below 700 K still has much scope for reduction. Novel approaches, such as nanostructure engineering, are to be encouraged to further strengthen phonon scattering, which is beneficial for enhancing the average zT of n-type skutterudites over the entire temperature range and therefore effectively improving the conversion efficiency of the devices. Furthermore, at high temperatures, skutterudites face severe oxidation and Sb volatilization issues, leading to relatively poor reliability during service. Developing effective protective coating or sealing technology against oxidation and volatilization is also important for their practical applications.