Monoclinic hydroxyapatite was synthesized by a wet method followed by heati
ng in air at 1473 K for 1 h, The product is carbonate-free and has a Ca/P r
atio of 1.65, which is slightly lower than the theoretical value (1.67) of
hydroxyapatite. The crystal structure mas investigated by Rietveld refineme
nt using X-ray powder diffraction data. The structure has monoclinic symmet
ry with the space group P2(1)/b (No, 14), Z = 4, Dx = 3.14 g cm(-3), and th
e lattice constants are a = 9.426(3) Angstrom, b = 18.856(5) Angstrom, c =
6,887(1) Angstrom, and gamma = 119.97(1)degrees. The hydroxyl ions have an
ordered arrangement along the hydroxyl columns. The hydroxyapatite prepared
in the present study is 98% monoclinic. (C) 1999 Academic Press.