DIELECTRIC PERMITTIVITY AND PHASE-TRANSITIONS IN THE SRTIO3-KTAO3 SYSTEM

The dielectric permittivity and losses of the (SrTiO3)(0.85)(KTaO3)(0. 15) solid solution have revealed an unusual behavior at temperatures o f 5-300 K and frequencies ranging from 100 Hz to 1 MHz. The dielectric permittivity exhibits a broad maximum at approximate to 40 K, which o beys the Curie-Weiss law in the high-temperature wing, and the onset o f low-temperature relaxation contributions. Besides, while for T>40 K it is a fully ergodic, uniformly ordering system, the uniform polar or dering is replaced with decreasing temperature by two low-temperature phase transitions to a glass-like state. The proposed mechanism for th e dielectric relaxation and the observed phase transformations involve s reorientation and ordering in the system of electron and hole polaro ns, which form in the course of charge compensation of the heterovalen t ions Sr2+, K+ and Ti4+, Ta5+ distributed randomly in the sublattices . (C) 1997 American Institute of Physics.