The synthesis of Ba0.7Sr0.3TiO3 ceramics prepared by sol–gel combustion method with urea as fuel

The preparation of barium strontium titanate (Ba0.7Sr0.3TiO3; BST) ceramics prepared by sol–gel combustion method using urea as fuel. The molar ratio of sol powder: fuel was 1:1. The samples were calcined at 450–950 °C for 2 h. X-ray diffraction (XRD) showed the pure perovskite phase at the calcination temperature of 750 °C. The synthesis BST was in the cubic structure which corresponding to JCPDS 34-0411. The particle size increased with the increasing of calcination temperature. The XRD patterns of the BST ceramics that sintered at the temperature of 950–1350 °C for 2 h showed the pure perovskite phase of BST ceramics in all of the samples. The microstructure of BST ceramics were analyzed by a scanning electron microscope (SEM). The grains were almost in spherical shape and the grain size increased with the increasing of sintering temperature. The average grain size was about 0.18–3.93 µm. The sample sintered at 1350 °C for 2 h had excellent dielectric constant (~4870).