Crystal structure and EPR study of Mn-doped β-tricalcium phosphate

Mn-doped {beta}-tricalcium phosphate was prepared by solid state reaction at 1100 deg. C. The crystal structure of Ca{sub 2.85}Mn{sub 0.15}(PO{sub 4}){sub 2}, was determined by single crystal X-ray diffraction and found to be rhombohedral, R3c. Unit cell parameters are: a = 10.3419(3); c = 37.025(3) A (hexagonal setting), Z = 21. Structure refinement data show that from the five Ca positions the Ca(4) site is only half filled and that the Mn{sup 2+} ions occupy the hexacoordinated Ca(5) site solely. EPR spectroscopy reveals that manganese in solid solutions Ca{sub 3-x}Mn{sub x}(PO{sub 4}){sub 2} (x = 0.1; 0.28; 0.6) is divalent and supports the structure refinement results that Mn occupies the Ca(5) site with a geometry very near to a regular octahedron.