Effect of nonstoichiometry on the microstructure and dielectric properties of strontium titanate ceramics

Nonstoichiometric strontium titanate (ST) ceramics with precisely controlled Sr/Ti ratio of 0.997-1.02 were synthesised by solid state reaction. Structural properties and microstructure development was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric properties were evaluated as a function of the temperature and frequency in the radio frequency range. The grain size was found to decrease dramatically with increasing Sr/Ti ratio > 1. The variation of Sr/Ti ratio has only weak effect on the quantum paraelectric behaviour of ST without any dielectric anomaly observed. The TiO2 excess promotes the increase of the dielectric permittivity values with loss factor similar to stoichiometric ST. Sri(1.01)TiO(3.01) composition exhibits much lower loss, while the dielectric permittivity is somewhat below the values for stoichiometric ST ceramics. (c) 2005 Elsevier Ltd. All rights reserved.