Improved Properties of Doped BaTiO3 Piezoelectric Ceramics

(CazBa1 − z)(Ti1 − x − wCoxNbw)O3 − δ lead‐free piezoelectric ceramics are prepared using solid‐state reactions. The use of a Li2O sintering aid enables one to obtain dense ceramics at a temperature of 1100 °C instead of the 1350 °C used for BaTiO3 (BT) in conventional sintering. X‐ray diffraction (XRD) data indicate structural modifications, suggesting insertion of the doping elements into the tetragonal structure. The insertion of Li/Ca/Co/Nb improves piezoelectric properties: for micrograin‐size ceramics, a piezoelectric charge constant and an electromechanical coupling factor of d33 = 255 pC N−1 and kp = 43.5% are reached, respectively. Furthermore, a thermal annealing of the cobalt‐doped sample at 1080 °C under O2 atmosphere leads to d33 = 280 pC N−1 and kp = 44.6%. BaTiO3:Co ceramics present distorted ferroelectric cycles due to the occurrence of an internal bias field. The high mechanical quality factors (Qm > 1000) obtained for the doped BT ceramics afford stability against electrical stress of up to 500 VRMS mm−1, which makes these materials competitive with PZT4 for some applications. Dense barium titanate ceramics are obtained at a temperature of 1100 °C using Li2O as the sintering aid. By using Ca2+, Co2+/3+, and Nb5+ ions as dopants, a hard piezoelectric material is obtained with improved properties. The densification, microstructure, crystallographic structure, dielectric, piezoelectric, and electromechanical properties are studied in regard to the doping content.