The chalcogenide phosphate apatites Ca-10(PO4)(6)S, Sr-10(PO4)6S, Ba-10(PO4)(6)S and Ca-10(PO4)(6)Se

Four new apatitic phases were prepared and their structures determined. The structure of Ca-10(PO4)(6)S was refined from single crystal X-ray data and the structures of Sr-10(PO4)(6)S, Ba-10(PO4)(6)S and Ca-10(PO4)(6)Se from powder X-ray data using the Rietveld method. The four apatites are isostructural and crystallize in the trigonal space g roup P (3) over bar with the chalcogenide ion positioned at (00 1/2). The s ulfoapatites show no ability to absorb H2S in the way that oxyapatite absor bs H2O at elevated temperatures. This can be attributed to the position of the sulfide ion and the way it influences the crystal structure around the vacant chalcogenide position at (0 0 0).