Electrostrictive behavior in lead magnesium niobate (PMN) actuators. I. Materials perspective

Abstract

Lead magnesium niobate (Pb(Mg_1/3Nb_2/3)O₃ or PMN) exhibits many attractive properties required by actuators for precision submicron control. At room temperature hysteresis is negligible, thermal expansion is less than 1 microstrain degrees C^-1, and the longitudinal strain sensitivity is 375 microstrain at 600 V mm^-1. There has been recent interest in using PMN actuators in applications near 0 degrees C, which is near the Curie temperature of the material. The purpose of this paper is to use the nonlinear constitutive relations describing the fundamental material behavior, along with supporting to test results, to establish a foundation for an engineering description of electrostrictive materials for the design of integrated actuator and structure systems. This paper presents an experimental characterization of PMN strain response, hysteresis and dielectric permittivity for temperatures between -50 degrees C and 100 degrees C. Measurements were made of the transverse strain of a thin PMN plate at bias fields of 0 and 400 V mm^-1 and for frequencies between 1 and 1000 Hz. Field dependent effects are discussed in terms of the nonlinear electrostrictive equations derived from a parametric elastic Gibbs free energy function. The temperature dependence of the permittivity and induced piezoelectric coefficient are modelled by a modified Curie-Weiss law.