Mechanism of the polarization response in the relaxor state of lead scandotantalate single crystals with different levels of ion ordering

The dielectric properties and optical transmission of stoichiometric lead scandotantalate (PST) single crystals in strong electric fields was studied above the temperature of the spontaneous ferroelectric phase transition (T_sp). It is shown that the mechanism of polarization response directly above T_sp is related to induced polarization effects and macrohysteretic behavior only in ac fields above 5 kV/cm. Ananalysis of reciprocal dielectric permittivity carried out over a broad temperature range far above the temperature at which the dielectric permittivity passes through a maximum revealed that specific features of the relaxor behavior manifest themselves up to 400°C even in highly ordered PST crystals.