Stabilization of calcium oxyapatites with lanthanum(III)-created anionic vacancies

Two series of samples of the system Ca10-xLax(PO4)(6)(OH)(y) (0 less than o r equal to x less than or equal to 2), have been synthesized by solid-state reaction at high temperature. In this composition range the apatite struct ure is maintained. Cationic distribution was analyzed by Rietveld refinemen t of the XRD data, showing a preferential substitution of La(III) ions in t he Ca(2) position. The introduction of the trivalent ion provokes the trans formation of OH- to O2- ions. Stable oxy- or oxyhydroxyapatites with numero us anionic vacancies have been synthesized as a function of the lanthanum c ontent or the synthesis conditions.