RANDOM BARRIER HEIGHT MODEL FOR PHASE-SHIFTED CONDUCTIVITY IN PEROVSKITES

A large dielectric permittivity peak which occurs at low frequency and high temperature in many perovskite crystals and ceramics, and an ass ociated difference in de and ac conductivity, is attributed to phase s hifted conductivity resulting From mobility barriers of different heig hts. A model is developed which has intrinsic barriers, and higher and more widely spaced extrinsic barriers, and special cases are examined . Model predictions show good agreement with experimental results of S tumpe, Wagner, and Bauerle for an SrTiO3 single crystal 1.02 mm thick. The additional peaks seen by them at higher temperature for a crystal 0.24 mm thick are qualitatively accounted for by adding a third set o f still higher barriers with spacing equal to the crystal thickness.