Measurements of the dielectric constant $\kappa$, specific heat $c_p$, and pyroelectric coefficient $\frac{d{P}_s}{\mathrm{dT}}$ of LiTa${\mathrm{O}}_3$ have been made over the temperature range from 25 to 700°C. The experimental technique enabled all these measurements to be made simultaneously or consecutively on the same sample. In each of these measurements pronounced anomalies were observed at the ferroelectric Curie temperature $T_C=618\mathrm{}°$C, clearly indicating a transition of the second order. From the pyroelectric and specific-heat measurements, the temperature dependence of the spontaneous polarization has been obtained to within 5% accuracy. At temperatures $T$ where $\frac{T}{T_C}\gtrsim 0.9$ it was found that ${P_s}^2\propto (T-T_C)$ and $\frac{1}{\kappa }\propto (T-T_C)$, in accordance with thermodynamic theory, and the specific-heat data are entirely consistent with these measurements.

• Received 4 March 1968

DOI:https://doi.org/10.1103/PhysRev.172.564