Temperature-field phase diagram and spontaneous polarization in Pb(Sc_1/2Ta_1/2)O₃single crystal

The temperature-field phase diagram and the temperature dependence of the spontaneous polarization in Pb(Sc1/2Ta1/2)O3 (PST) have been investigated by measuring the permittivity in the dc biasing field and observing the p-E hysteresis loop, respectively. X-ray diffraction studies to clarify the B-site cation ordering have also been performed. We have confirmed the PST single crystal used in our experiment to be a disordered PST. We have also determined that the ferroelectric critical endpoint (CEP) on the temperature-field phase diagram in the dc biasing field applied along the [111]c direction (in the cubic coordinate) was at 19.3 C and 4.85 kV cm-1. Our experimental results of the ferroelectric CEP and the spontaneous polarization in disordered PST are discussed in this paper on the basis of the Landau-type phenomenological theory.