Crystal chemistry of the alkaline-earth apatites A(10)(PO4)(6)CuxOy(H)(z) (A = Ca, Sr and Ba).

The crystal chemistry of the cuprate apatites A(4)(I)A(6)(II)(PO4)(6)CuxOy(H)(z) (A = Ca, Sr and Ba) was investigated by powder X-ray (PXRD) and neutron diffraction (PND) and X-ray photoelectron spectroscopy (XPS). The refined crystal structures confirmed earlier X-ray diffraction studies that showed copper resides in the apatite channels and additionally, located hydrogen. For all materials copper is primarily divalent (Cu2+) but in the calcium and strontium analogues co-exists with minor Cu3+. This is in contrast with a previous work where Cu1+ and Cu2+ were reported. © 2009, Royal Society of Chemistr