Syntheses and characterization of Uranium containing apatites

Synthetic apatites containing uranium were prepared from solution by precipitation. The hydroxy apatite obtained contained up to ca. 1% uranium homogeneously dispersed in the apatite matrix. Carbonate-fluoride apatites were prepared from calcium carbonate via a heterogeneous reaction. The uranium content in the latter apatites was to low to check for distribution by EPMA. However emission spectra and vibrational analysis proved that UO₂²⁺ was the species present in both apatites (HAP and CAP). XRD of pure and uranium containing apatites revealed no significant differences. When heated to 700°C most uranium-containing apatites, including natural Oron (Israel) apatite, lose the characteristic UO₂²⁺ emission and show an identical emission centered at ca. 18860 cm^-1, suggesting the transformation of UO₂²⁺ to another ion, possibly uranate.