ELECTROSTRICTIVE PROPERTIES OF PBMG1 3NB2 /3O3 (PMN) BULK CERAMICS/

Loop hysteresis, dielectric and electrostrictive properties of bulk ce ramics (1 - x) PbMg1/3Nb2/3O3 - xPbTiO3 - yMgO for x = 0, 5, 10 % and y = 0, 6, 12 % have been investigated. An initial lead oxide magnesium excess stabilises the perovskite structure during its formation and l eads to an improvement of the electrical properties. These materials a re relaxor-type ferroelectrics with high permittivities in a large spa ce of temperature around - 12-degrees-C for x = 0 % to + 45-degrees-C for x = 10 %. They exhibit, at 25-degrees-C, large electrostrictive lo ngitudinal (x3 = DELTAe/e) and transversal (x1 = DELTAd/d) strains wit hout hysteresis, under an electric field of +/- 2 kV/mm and at low fre quency (F = 20 mHz): x3 = 3.5 x 10(-4) and x1 = 10(-4) for PMN-0.12 Mg O and x3 = 10(-3) and x1 = 2 x 10(-4) for 0.9 PMN-0.1 PT-0.12 MgO. Add itions of titanium improve the polarization of material which largely contribute to large strains whereas electrostrictive coefficients Q(ij ) (x(i) = Q(ij) . P(j)2), determined at 25-degrees-C, slightly increas e with PbTiO3 percent (for a constant magnesium excess).