The dependence of the piezoelectric properties on the differences of the A-site and B-site ions for (Bi1-xNa x)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-xNa x)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 (k 33, k p) of the piezoelectric ceramics was investigated. It was found that the coupling factors (k 33, k p) of the ceramics have little dependence on the parameters of vertical bar M vertical bar , vertical bar R vertical bar and vertical bar X vertical bar , respectively. However, if a comprehensive weight factor F(w) is defined as F(w) = vertical bar M vertical bar + vertical bar R vertical bar + 100 vertical bar X vertical bar , 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 k 33 and k p. With increasing of the value of F(w), the k 33 and k p increase consequently. From this viewpoint, new BNT-solid solution with larger electromechanical coupling factors would be predicted, and a new system of (Bi1-xNa x)TiO3-based solid solutions was invented in our group by using this method