Low-temperature dielectric relaxations in Y-doped strontium titanate ceramics

Abstract

The structural and low-frequency dielectric properties of Y-doped strontium titanate ceramics prepared by the conventional mixed oxide method are investigated. The lattice parameter is found to decrease linearly in the Sr1-1.5xYxTiO3 system, confirming the incorporation of Y onto the Sr site of perovskite lattice of strontium titanate up to the solid solubility limit below x = 0.05. The real and imaginary parts of the dielectric permittivity of Sr1-1.5xYxTiO3 ceramics exhibit a relaxation between 100 Hz and 1 MHz in the temperature range 10-40 K, slightly shifting to higher temperatures with increasing Y content. Such dielectric behavior, yielding real part of the dielectric permittivity up to 35 000, is attributed to the relaxation of individual dipoles formed by off-center displacement of Y3+ ions on Sr sites in a highly polarizable lattice of strontium titanate. The other dielectric relaxation observed in Sr1-1.5xYxTiO3 from 125 to 300 K is attributed to the oxygen vacancy related mechanisms.