Effect of calcium addition on microstructure, structure, and electrical properties of SrTiO3-based materials synthesized by citrate and solid-state reaction method

Abstract

Materials with a general formula Sr1-xCaxTiO3 (where x = 0.0; 0.2; 0.4; 0.6; 0.8; 1.0) were obtained by two different synthesis routes: wet chemical method and conventional solid-state reaction. The effect of the synthesis method and the calcium content on the properties of the synthesized materials was evaluated. All materials were sintered at 1400 °C and tested for structural, microstructural, and electrical properties. X-ray diffraction analysis showed a decrease in the symmetry of the perovskite structure (cubic → tetragonal → orthorhombic) and a decrease in the cell volume of the perovskite structure phases with an increase in the Ca amount introduced into the system, regardless of the applied synthesis method. Also, the materials obtained by the citrate method had a smaller grain size compared to the materials synthesized by the solid-state method. However, for materials synthesized by both methods the increase of grain size with increasing calcium amount was observed. Moreover, the effect of calcium content on the porosity of the materials obtained by the citrate method was observed while for materials obtained by the solid-state reaction this parameter was generally not affected by Ca amount. The results of electrical properties measurements carried out in the air atmosphere indicate the ionic conductivity in Sr1-xCaxTiO3 materials irrespective of the applied synthesis method.