Crystallographic study of lead-substituted hydroxyapatite synthesized by high-temperature mixing method under hydrothermal conditions

摘要

The solid solutions in the system of Ca and Pb hydroxyapatite, Ca10 chi Pb chi HA(chi = 0-10), were successfully synthesized by high-temperature mixing method (HTMM) at 200 degrees C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice parameters of the solid solutions prepared by both of the methods didn't vary linearly with Pb contents, and they have two turning points of 0.4 and 0.6 of Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M (2) site in the apatite structure. HTMM gives Ca-Pb HA solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb3O2(OH)(2) in the Pb(NO3)(2)center dot 4H(2)O solution before mixing with (NH4)(2)HPO4 solution at 200 degrees C, HTMM causes the decrease of crystallization of the samples with high Pb content.