Electrostrictive Effect In Pb(Mgi_/3Nb_2/3)O₃-Type Materials

Lead magnesium niobate Pb(Mgi/3Nb2_/3)0₃ (PMN) is a relaxor ferroelectric with a disordered perovskite structure. A statistical inhomogeneity in the distribution of Mg²⁺ and Nb⁵⁺ ions in the B-sites of an AB0₃ perovskite lattice leads to a wide Curie temperature range in which the crystal exhibits an intimate mixture of paraelectric and ferroelectric mi-croregions. Relaxor-type ferroelectrics such as PMN show somewhat unusual electrostrictive phenomena. Although the polarization-related electrostrictive coefficients Q (defined as x — QP²) are one order of magnitude smaller than those of simple perovskite compounds, large electrostrictive strains can be obtained because of their huge dielectric constants. A quadratic relation between the induced elastic strain and the electric polarization holds even below the average Curie temperature. The electrostrictive properties of PMN and related materials are reviewed in this article. Re-laxor ferroelectrics are promising transducer materials for use as active elements in an adaptive optic system. Applications of electrostrictive transducers for optical mirror control, for the stabilization of laser beam intensity by means of optical bistability, and for pressure gauges are summarized.