Precipitate Formation in the Strontium-Phosphate System

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Science  18 Mar 1966:
Vol. 151, Issue 3716, pp. 1386-1388
DOI: 10.1126/science.151.3716.1386


Study of the precipitation process in the aqueous Sr(OH)2-H3PO4 system, in order to elucidate the phase transformations and the nature of the final solid phases, shows that over much of the range of compositions studied the initial precipitate is poorly crystalline; the x-ray pattern resembles that of strontium hydroxyapatite but has a strontium: phosphorus molar ratio close to 1.3. Within 1 hour the initial precipitate changes to a stable crystalline phase (or phases), with corresponding change, either up or down, in the strontium: phosphorus ratio. At high ratios of Sr(OH)2 to H2PO4 the initial precipitate is Sr3(PO4)2-4H2O, which then converts to a phase having the x-ray diffraction pattern of strontium hydroxyapatite, but having a strontium: phosphorus ratio that depends somewhat on the initial ratio of Sr(OH)2 to H3PO4 used in the precipitation.