Ferroelectric, piezoelectric, and optical properties of SrTeO3 single crystals and phase-transition points in the solid-solution systems

Temperature dependences of dielectric, ferroelectric, elastic, piezoelectric, and optical properties of a new ferroelectric crystal, SrTeO₃, have been measured. Ferroelectricity in this crystal is confined to the temperature range between 312 and 485°C. All the measured constants exhibit abrupt changes at 312°C, which shows the phase transition at this temperature to be of the first order. The electromechanical coupling factors k₂₁ and k₂₂ at 312°C are 0.34 and 0.37, respectively, which are large in spite of the small value of the spontaneous polarization; 0.037 C/m². The temperature dependence of the piezoelectric constant d₂₂ is well explained by the dielectric constant and the spontaneous polarization, while that of d₂₁ seems to be peculiar; i.e., it monotonically decreases to nearly zero at the upper transition point. The elastic compliances $S_{11}^D$ and $S_{22}^D$ show no anomaly in the ferroelectric temperature range. The obtained value of 17.3 eV for the dispersion energy of the refractive index n_b indicates that this crystal may be built up by the tetrahedral framework. Phase‐transition temperatures in the solid‐solution systems Sr_1−xBa_xTeO₃ and Sr_1−xCa_xTeO₃ are studied on ceramic samples. The two transition points decrease with increasing x in both systems.