Inert atmosphere processing of hydroxyapatite in the presence of lithium iron phosphate

Abstract

The present study describes sintering behaviour of hydroxyapatite (HAp) upon addition of lithium iron phosphate (LFP) (1-10 wt.%) system in inert (Ar) atmosphere. The interaction between materials and melting of LFP influenced early and intermediate stages of HAp sintering, shifting the densification curves towards low-temperature side. Analysis of densification process indicated significant differences upon LFP addition. The reaction mechanism that assumes the initial interaction between phosphates from LFP and calcium from HAp was proposed, generating calcium vacancies and contributing to HAp densification. Cross-sections of sintered samples showed changes in microstructural properties, with uniform atomic distribution and presence of Li2Fe3O4 spherical inclusions (200 nm) located at grain boundaries of calcium phosphate matrix. The Rietveld refinement analysis indicated changes in structural and microstructural parameters like crystallite size, anisotropy and microstructural strain of HAp upon LFP addition. Mechanical characterisation indicated improvements in fracture behaviour upon LFP addition.