COMPOSITIONAL STUDIES OF LANTHANUM-MODIFIED MORPHOTROPIC PHASE-BOUNDARY PB(MG1 3NB2/3)O-3-PBTIO3 CERAMICS/

Investigations have been performed on the La-modified (1 - x)Pb(Mg1/3N b2/3)O-3-(x)PbTiO3 crystalline solution for compositions close to the morphotropic phase boundary (MPB) using energy-dispersive X-ray spectr ometry(EDS). Studies were performed on specimens with La contents betw een 0 and 10 at.% for x = 0.35 which were fabricated by keeping the av erage Mg/Nb/Ti ratio in the bulk ceramic unchanged, In this series of samples, La3+ was compensated for by introducing B-site vacancies, Qua ntitative analysis by EDS revealed a change in the B-site cation conce ntrations with La substitution, It was observed that the Nb concentrat ion decreases and the Ti concentration increases with increasing La co ntent, indicating that local charge compensation in the perovskite pha se is taking place by an adjustment in B-site cation concentrations, P hase analysis demonstrated the presence of a second phase for La conte nts above 2 at.%, Scanning electron microscopy then revealed the prese nce of a secondary pyrochlore phase with an octahedral-like morphology , The composition of the pyrochlore phase was found to be rich in Nb a nd poor in Ti. The effects of changes in composition on dielectric pro perties, polarization, and electrically induced strain were then inves tigated.