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

Abstract: Mn-doped β-tricalcium phosphate was prepared by solid state reaction at 1100°C. The crystal structure of Ca2.85Mn0.15(PO4)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)Å (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 Mn2+ ions occupy the hexacoordinated Ca(5) site solely. EPR spectroscopy reveals that manganese in solid solutions Ca3−x Mn x (PO4)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. [Copyright &y& Elsevier]