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 Pb3(VO4)2(1−x)(PO4)2x. It was found that rich-vanadium compounds such as Pb3(VO4)2 and Pb3(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 Pb3(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 compoundsʹ 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.