Thermo-physical insights into a series of strontium substituted hydroxyapatite

Abstract

In this study, we investigated the effect of Sr substitution (2, 4, 8, 16 mol. %) on the thermo-physical properties of hydroxyapatite (HA). FTIR and Raman analysis revealed that Sr substitution incorporated CO32− and HPO42− into the HA lattice and consequently SrHA lost more mass according to the TG studies. The substitution of Sr reduced the dehydroxylation peak temperatures from 1266 °C to 1226 °C and decomposition peak temperatures from 1472 °C to 1432 °C. Heat treated HA, 2SrHA, 4SrHA and 8SrHA preserved dominant HA phase (>99%). However, 16SrHA decomposed to TCP (>23 wt %). Moreover, Sr substitution increased the “a” and “c” lattice constants and thus, enlarging the crystal volume of HA. Raman studies confirmed that Sr substituted HAs up to 8 mol % decomposed slightly to oxyhydroxyapatite (OHA). We employed a deconvolution process to the Raman peaks at ~960 cm−1 to calculate the degree of the OHA decomposition by Sr substitution.