Non-monotonic concentration dependence of electromechanical properties of piezoactive 2-2 composites

The paper reviews the experimental and theoretical non-monotonic dependences of electromechanical properties on the volume concentration of one of the components in two-component piezoactive 2-2 composites. Specific attention is focused on the evolution of piezoelectric coefficients eij * and dij * , their anisotropy and electromechanical coupling factors kij * , kp * and kt * . This evolution is analysed in terms of the ratios between some electromechanical constants of the components. Important results are concentrated in systems of analytical conditions for reaching max e 31 * >0 and max kt * . These systems are written in terms of introduced `basic' constants and other parameters depending on the electromechanical properties of the components, and the fulfillment of these conditions is analysed in connection with known experimental data of the components.