DIELECTRIC-PROPERTIES AND PHASE-TRANSITIONS OF SRTIO3-KTAO3 SYSTEM

Dielectric spectra of epsilon' and epsilon '' (5-300 K, 100 Hz-10 MHz) of (SrTiO3)(x)(KTaO3)(1-x) are studied with the most successfully pre pared x = 0.85 composition. A wide epsilon'(T) maximum at 43 K (43 kHz ) is observed. Losses reveal the additional relaxations in the 4.6-9.8 K and 176-247 K regions. Of most importance is, that Curie-Weiss beha vior is replaced by relaxation below the temperature of epsilon'(T) ma ximum. That is the ergodic homogeneous ordering turns on a glass-like behavior below 43 K. The above can be understood as an antiferroelectr ic phase transition, but a glass-like order-disorder transition at 18 K looks more preferable. The cooperative hopping reorientation of elec tron and hole polarons originating due to charge transfer, as the caus e of dielectric relaxation, resulting in the polaronic reorientation f reezing and glass-like state at 18 K within SrTiO3, and an another pos sible one at 2 K within KTaO3 dominated regions are considered. This m odel is supported by dielectric and infra-red absorption with SrTiO3:T a crystals, where absorption at 2000 cm(-1) is suggested to be due to polarons.