The chalcogenide phosphate apatites Ca₁₀(PO₄)₆S, Sr₁₀(PO₄)₆S, Ba₁₀(PO₄)₆S and Ca₁₀(PO₄)₆Se

Abstract

Four new apatitic phases were prepared and their structures determined. The structure of Ca 10 (PO 4 ) 6 S was refined from single crystal X-ray data and the structures of Sr 10 (PO 4 ) 6 S, Ba 10 (PO 4 ) 6 S and Ca 10 (PO 4 ) 6 Se from powder X-ray data using the Rietveld method. The four apatites are isostructural and crystallize in the trigonal space group P-3 with the chalcogenide ion positioned at (0 0 ½). The sulfoapatites show no ability to absorb H 2 S in the way that oxyapatite absorbs H 2 O 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).