The dependence of the piezoelectric properties on the differences of the A-site and B-site ions for (Bi1−xNax)TiO3-based ceramics

The effect of the differences of the ionic size R, atomic weight M, and electric negative X of the A-site and B-site ions of the ABO3 perovskite (Bi1−xNax)TiO3(BNT)-based solid solutions (where the complex of Bi and Na ions occupy the A-site and Ti ion is in the B-site) on the electromechanical coupling factors (k33, kp) of the piezoelectric ceramics was investigated. It was found that the coupling factors (k33, kp) of the ceramics have little dependence on the parameters of ∣M∣, ∣R∣ and ∣X∣, respectively. However, if a comprehensive weight factor F(w) is defined as F(w) = ∣M∣ + ∣R∣ + 100∣X∣, which is a dimentionless number containing M, R and X, and can be regarded as the comprehensive factor related to the spontaneous polarization of a unit cell in a given ceramic system, one can fined that F(w) has good correspondence with the coupling factors k33 and kp. With increasing of the value of F(w), the k33 and kp increase consequently. From this viewpoint, new BNT-solid solution with larger electromechanical coupling factors would be predicted, and a new system of (Bi1−xNax)TiO3-based solid solutions was invented in our group by using this method.