Influence of vanadium substitution on sintering behaviour of Pb3(VO4)2(1-x)(PO4)2x ceramics

Intermediate-stage sintering has been investigated in lead orthophosphovanadates Pb-3(VO4)(2(1-x))(PO4)(2x). It was found that rich-vanadium compounds such as Pb-3(VO4)(2) and Pb-3(VO4)(1.6)(PO4)(0.4) densify rapidly with important grain growth. For these compounds grain growth is controlled by grain boundaries and densification occurs by a mixed mechanism with lattice and grain boundary diffusion. For Pb-3(PO4)(2). sintering mechanism supports a model of grain-boundary-controlled densification and grain growth is a surface diffusion-controlled pore drag mechanism. Moreover, the presence of phosphorus in compounds' formulae, tends to decrease the grain-boundary mobility, preventing pore-boundary separation. The kinetics analysis highlights the importance of vanadium substitution in modifying the diffusion coefficient of rate-limiting species. (C) 2000 Elsevier Science Ltd. All rights reserved.