Phase transitions and dielectric properties of lead-free Bi0.5K0.5TiO3 - BaTiO3 piezoelectric ceramics

Lead free piezoelectric ceramics of (1-x)Bi_0.5K_0.5TiO₃-xBaTiO₃ (BKT-BT) were fabricated by the solid state reaction method with normal sintering. The influence of BT addition on the crystal structure, phase transition and dielectric properties was investigated. The crystal structure and ferroelectric phase transition were studied by X-ray diffraction (XRD) and dielectric measurements. The complete solid solution of BKT-BT was observed for all compositions. In XRD results, all compositions showed a single phase perovskite structure with tetragonal symmetry at room temperature. With increasing BT content, the separation between diffraction peaks corresponded to increasing tetragonality. The phase transition temperature of ferroelectric tetragonal - paraelectric cubic (T_C) decreased with increasing BT content. As the amount of BT concentration increased, the ceramic became denser, and almost no porosity was finally obtained.