Structural features and dielectric response of barium-strontium titanate ceramics

In this work, we carried out a comparative study of the surface structure of barium-strontium titanate Ba1-xSrxTiO3 ceramics of various compositions (x = 0,1; 0,2; 0,25; 0,3; 0,4 and 0,5) and the dielectric characteristics of samples in a wide temperature range. It has been found that with increasing the strontium content, a decrease in the density of ceramic samples is observed. An increase in the strontium concentration in the composition of the ceramics under study leads to a reduction in the average grain size by an order of magnitude, and fine grains from 2 μm to 200 nm. For all ceramic samples of barium-strontium titanate, there is a deviation of the elemental composition from the stoichiometric at the nanoscale. The closest to the stoichiometric composition in terms of the molar content of elements is the composition of the Ba0,75Sr0,25TiO3 samples. It was found that the samples of this composition have the highest value of the permittivity at room temperature. Temperature studies of the dielectric permittivity showed the existence of two maxima: at a temperature of 130°C, corresponding to the Curie temperature of pure barium titanate ceramics, and at lower temperatures in the range from 10 to 100°C, the second depends on the strontium content. The low-temperature maximum for the  value corresponds to the diffuse transition of the solid solution Ba1-xSrxTiO3, whose relaxor properties are confirmed by deviation of the temperature dependence from the Curie–Weiss law. The samples of Ba0,75Sr0,25TiO3 composition have the most pronounced relaxor behavior.