Syntheses and superstructures of (Cd, M)5(PO4)3OH (M=Mn, Fe, Co, Ni, Cu, Hg)

Divalent ions of the first series transition elements and Hg were introduced into a cadmium hydroxyapatite Cd5(PO4)3OH by replacing a part of Cd2+, and the effects on the crystal growths and the structural changes were studied. Cd2+ can be exchanged with Mn2+ up to about 30 mol %, with Ni2+ or Hg2+ up to about 10 mol %, and with a little amount of Fe2+ or Cu2+. It was found that Cd5(PO4)3OH forms a superstructure when it contains a small amount of Mn2+, Fe2+, Co2+, Ni2+, Cu2+ or Hg2+ ion. Infrared spectra of Cd5(PO4)3OH containing these ions show some new bands in addition to those of Cd5(PO4)3OH. The average structures of the crystals containing a small amount of Hg2+ and Ni2+, and the superstructure of the crystal containing Mn2+ were refined with the full-matrix least-squares method, although the amounts and sites of the substituting ions could not be determined except for the crystals containing Hg2+. The superstructure belongs to P63 (a=16.1990(3), c=6.6485(1)Å and Z=6) and has more distorted PO4 tetrahedra than the structure of pure Cd5(PO4)3OH.