Piezoelectric PMN-PT ceramics from mechanochemically activated precursors

Piezoelectric Pb(Mg1/3Nb2/3)O-3-PbTiO3 (PMN-PT) ceramics with 0.2 and 0.35 PT have been prepared from mechanochemically activated powders. Pressureless sintering in air and hot pressing were tested. PbZrO3 packing was necessary to limit lead oxide losses and to avoid the formation of second phases at the surface when temperatures above 1000 degreesC were used. Ceramics sintered at 1200 degreesC presented densities of 90% and a grain size of 4 mum. Hot pressed ceramics hardly showed porosity and had submicron (0.1-0.5 mum) grain size, which make the mechanoactivated powders very suitable for templated grain growth matrices. Electrical and electromechanical characterisation was accomplished. The 0.2 PT composition combined relaxor dielectric behaviour with piezoelectricity after poling. The 0.35 PT ceramics presented a first order ferroelectric-paraelectric transition at 171 degreesC and a complex transverse piezoelectric coefficient of -(181.8-i3.6) pC N-1 at room temperature. (C) 2003 Elsevier Ltd. All rights reserved.