Structural refinements of strontium substituted hydroxylapatites

The crystal structures of hydroxylapatites synthesized at different degree of strontium substitution for calcium (5, 20 and 60% Sr atoms) have been investigated by X-ray powder-pattern fitting. The strontium content, as obtained from the refinements, is in agreement with the chemical analysis data indicating that Rietveld refinement is a powerfull method in order to estimate quantitatively the inclusion of a foreign ion when the extent of the substitution determines a significant variation of the overall scattering power. The re fined occupancy factors of metal atoms show that the strontium preference for the sixfold M(2) site increases toghether with strontium molar fraction. No variation in the OH group position is observed.