Microstructure and electrical properties of antimony trioxide doped potassium sodium bismuth titanate ceramics

(1-x)[0.82Bi_0.5Na_0.5 TiO₃-0.18Bi_0.5K_0.5TiO₃]-x Sb₂O₃ (BNKT-xSb) ceramics were prepared by a conventional solid-state solution technique. The influence of Sb₂O₃ additive on the microstructure and electrical properties of the BNKT-xSb ceramics was investigated. The BNKT-xSb ceramics appeared a pure perovskite structure in the whole range of Sb₂O₃ (x<0.020). Sb₂O₃ might act as a "donor" or an "acceptor" in this piezoelectric ceramics due to its variable valences, which could change the electrical properties to "soft" or "hard". When x≤0.005, the piezoelectric coefficient (d₃₃) of BNKT-xSb increased with the increase of Sb₂O₃ content, which is a characteristic of the "soft" doping. On the contrary, a "hard" property was induced when x>0.005 at which d₃₃ decreased again. The ferroelectric and piezoelectric properties of BNKT-xSb ceramics changed when x≥0.010, which could be correlated to the formation of anti-ferroelectric micro-domains at room temperature.