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Lattice parameters and cation distribution of solid solutions of calcium and lead hydroxyapatite

1981; Springer Science+Business Media; Volume: 33; Issue: 1 Linguagem: Inglês

10.1007/bf02409444

1432-0827

R. M. H. Verbeeck, C. J. Lassuyt, H. J. M. Heijligers, F.C.M. Driessens, J.W.G.A. Vrolijk,

Bone Tissue Engineering Materials

Solid solutions of calcium hydroxyapatite (CaOHA) and lead hydroxyapatite (PbOHA) of the formula Ca10-x Pbx (PO4)6 (OH)2 were prepared by coprecipitation followed by heating at 800 degrees C in a steam of CO2-free water vapor of 1 atm. The samples were apatitic in the range 0 less than x less than 6 and contained lead phosphates as a second phase at higher Pb/Ca ratios. Lattice parameters and cation distribution of the apatitic samples were determined by X-ray diffraction. The lattice parameters varied linearly with x in the range considered, whereas all Pb2+ were located in the six-fold position for cations. There was a miscibility gap in the apatite series of solid solutions in the range 1 less than x less than 4, whereas apatites in the range 6 less than x less than 10 were not stable under the conditions of preparation. It is concluded that apatites in the range 4 less than x less than 6 represent a minimum in the free energy of solid solutions between CaOHA and PbOHA.