Electromechanical Properties of Order-Disorder Type Ferroelectrics. I. Piezoelectric and Elastic Properties

Abstract

A phenomenological theory of the electromechanical properties of order-disorder type ferroelectrics is developed. The theory takes into account properly the role of an ionic polarization which interacts with a dipole system. Based on Onsager’s equation of motion, the complex electric susceptibility, piezoelectric and elastic compliance coefficiencts are derived. Some examples of numerical calculation are shown. The results can explain the anomalous static and dynamic properties of the piezoelectric constants of NaNO₂, AgNa(NO₂)₂, Ca₂Sr(C₂H₅CO₂)₆ etc., and also the anomalous temperature dependence of the elastic compliances measured at constant polarization in Ca₂Sr(C₂H₅CO₂)₆ and Ca₂Pb(C₂H₅CO₂)₆.