Dielectric properties of Pb(Mg 1/3Nb 2/3)O 3 and (Pb 1− xLa x)(Mg (1+ x)/3 Nb (2− x)/3 )O 3 ceramics prepared by columbite route

Abstract

The role of the La-addition on the A-site of the perovskite Pb(Mg 1/3Nb 2/3)O 3 (PMN) on the phase formation, microstructure and dielectric properties was investigated. Ceramic samples were obtained from PMN and (Pb 1− x La x )(Mg 1+ x/3 Nb 2− x/3 )O 3 (PLMN) nanopowders synthesized by the columbite method using MgO and Mg-carbonate precursors. An influence on the degree of crystallinity and phase purity was found particularly in the PMN ceramics. Typical relaxor properties characterised by a diffuse phase transition with a maximum around 270 K and relaxation in the kHz range were observed. The incorporation of La induces the formation of a short range nanopolar ordered superstructure, thus modifying the dielectric relaxation properties, strongly depressing the permittivity. The observed behaviour is discussed in terms of microstructural characteristics induced by the Mg-precursor and of La-incorporation in the PMN perovskite unit cell.