Synthesis,characterization and structural study of lead hydroxyapatite Pb10-xMx(PO4)6(OH)2 (M = Zn,Cu) [Synthèse,caractérisation et étude structurale des hydroxyapatites à base de plomb Pb10-xMx(PO4)6(OH)2 (M = Zn,Cu)]

Two sets of solid solutions of general formulae pb10-xmx(po4)6(oh)2(m = zn,cu) were prepared by hydrothermal way. these compounds have been characterized by x-ray powder diffraction,chemical analysis and infrared spectroscopy. structural refinement by the rietveld method shows that the limit of miscibility in atomic percentage is 5.2 copper and 9.6 zinc. the limits of these solid solutions were essentially correlated to the difference in size and polarizability of metal cations. introduction of copper or zinc ions,with dimensions smaller than that those lead in apatitic structure is at the origin of a decrease of crystalline parameters a and c. in addition the study of cationic distribution between the two crystallographic sites shows preferential occupancy of copper in s(1) sites and a statistical distribution for zinc. the results obtained are used for a comparative analysis on the factors leading to mutual substitution of ca,sr,and cd in the lead hydroxyapatite (pbhap).