Improvement in high-Tc phase formation in (thallium–antimony) doped bismuth-based superconducting materials
Introduction
Bi–Sr–Ca–Cu–O with an orthorhombic structure is an important member of the metal oxide high-Tc superconductor compound (HTSC) family. It can be regarded as a model system for investigation of the appearance of the superconducting state by doping with different elements. A lot of interest is focused on the Bi(2223) phase and substitution of several cations, such as Pb+2, Sb+3, Mg+2, Nb+3, Ga+3, Mo+3 Au+3 and V+5, Pb+2Sb+3, Pb+2Sn+4 and Nd+3Tb+3 at different sites has already been investigated [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15].
It has been reported that the addition of Pb in the Bi(2223) matrix greatly facilitates the formation of the high-Tc domain [1], eases the diffusion of elements to form the high-Tc phase [2] and promotes the stability and abundance of the transient partially melted phase [3]. Addition of antimony is reported to exert a stabilizing influence on the formation of the 2223 phase [4] and believed to play an important role in enhancing the kinetics of especially the decarbonation reaction, as well as the promotion of the high-Tc phase [5]. Increasing annealing time from 10 to 50 h (at 1103 K) of Au-doped Bi(2223) system results in increase in the values of the critical transition temperature, Tc(0) (from 100 to 106 K) and the transport critical current density [6], [7]. On the contrary, the addition of Nb, Ga and Mo results in lowering the zero resistivity critical temperature, Tc(0) of the material [8], [9], [10]. Substitution Mg in place of Ca decreases the critical current density [11]. Higher Tc(0) value of 103 K together with the first Tc(onset) = 102 for the high-Tc phase and second Tc(onset) = 78 K for low-Tc phase have been observed in the bismuth based system doped with vanadium [12]. Doping with a lead–tin combination is reported to be effective in promoting the 110 K phase as compared to doping with Pb and Sn separately [13], [14]. A value of Tc(0) of 108 K has been reported for Nd–Tb doped material, i.e. Bi1−(x+y)NdxTbyPbSr2Ca2Cu3O10 [15].
In the present study, an enhancement of 3 K in the value of the Tc(0) and a regular increase in the magnitude of high-Tc (Bi-2223) phase has been achieved as a result of the addition of a certain concentration range of binary mixture of antimony and thallium.
Section snippets
Experimental detail
The samples with the nominal composition Bi1.7Tl0.3−xSbxPb0.4Sr2Ca2Cu3Oy (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and 0.20) are prepared by the conventional solid-state reaction method [16]. The stoichiometric amounts of high purity Bi2O3 (99.9%) PbO (99.9%), Sb2O3 (99.9%) and SrCO3 (99.9%) supplied by Aldrich and CuO (>99%), CaCO3 (99.9%) and Tl2O3 (>99%) supplied by Fluka are used as starting materials. The required quantities of the materials are weighed, mixed and ground for 1 h in an
Results and discussion
Fig. 1 shows the room temperature X-ray diffraction patterns of bismuth based superconducting materials containing different Tl:Sb ratios, i.e. Bi1.7Tl0.3−xSbxPb0.4Sr2Ca2Cu3Oy (x = 0.00, 0.02, and 0.04, 0.0.6 0.08, 0.10 and 0.20). The intensity of characteristic reflection peak (1 1 5) at 2θ ∼ 27° corresponding to the low-Tc phase (2212) decreases regularly from 919.65 cps to 545.56 cps, 276.09 cps, 182.79 cps and 131.71 cps for x = 0.00, 0.02, 0.04, 0.06 and 0.08, respectively, and then increases to 651.18
Conclusions
Of all the synthesized materials, the sample with an Sb content of x = 0.06 exhibits the highest Tc(0) value (109 K), the highest percentage of Bi(2223) phase (82.45%) and the lowest ΔT value (5 K). However, the entire set of samples shows a constant value of Tc(onset) = 114 K. A gradual decrease in peak intensity corresponding to the low-Tc phase at 2θ between 27 and 28° and regular increase in peak intensity corresponding to the high-Tc phase at 2θ near to 29° with increasing Sb-content in a certain
Acknowledgement
This work has been supported by the Higher Education Commission Pakistan through indigenous scholarship scheme under the grant contact.
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Cited by (13)
The effect of TlF<inf>3</inf> substitution on the weak links behaviour and AC susceptibility of Bi<inf>1.8−x</inf>Tl<inf>x</inf>Pb<inf>0.35</inf>Sr<inf>2</inf>Ca<inf>2</inf>Cu<inf>3</inf>O<inf>y</inf>F<inf>3x</inf> superconductors
2018, CryogenicsCitation Excerpt :The real part of AC susceptibility, χ′, shows two transitions as the temperature is lowered below onset of diamagnetic transition. The first sharp fall at the transition temperature Tc is attributed to the intra-granular transition (Tg) of the high-Tc (Bi-2223) phase and the second drop is attributed to the inter-granular transition temperature TcJ, due to the weak coupling between the grains, or may be to a transition of secondary phase [20]. As clearly shown in the inset of Fig. 3, the diamagnetic onset temperature (Tc) of the intrinsic superconducting transition for the samples with x = 0, 0.05, 0.10 and 0.15 is about 114.6, 115.7, 116.1 and 114.4 K, respectively.
Improvement of superconducting properties of (Bi, Pb)-2223phase by TlF<inf>3</inf> doping
2016, Physica B: Condensed MatterCitation Excerpt :In this work, we have chosen the thallium fluoride (TlF3) compound by introducing it in the structure of the (Bi, Pb)-2223 phase. This idea came from the fact that the individual substitutions of Bi by Tl and O by F have a positive effect on the properties of this phase [11–14]. Also, it is well known that the thallium based superconductors have highest critical transition temperatures, critical current densities and irreversibility fields when compared to the other Bi-based cuprates [13,15,16].