Hydrothermal synthesis studies in portions of the system CaO-P<sub>2</sub>O<sub>5</sub>-H<sub>2</sub>O-CO<sub>2</sub>-F have produced apatites with composition variations. The lattice constants of the apatites have been determined using computer analyses of x-ray powder diffraction data. By this method compositional fluctuations of a phase within a mixture containing several phases can be monitored. Lattice characteristics of hydroxyapatite (molar CaO/P<sub>2</sub>O<sub>5</sub>=3.3) synthesized at pressures of 2000 bars and temperatures from 300° to 800°C from bulk compositions over the range 2.0 to 5.0 CaO/P<sub>2</sub>O<sub>5</sub> are discussed.
H. C. W. Skinner, "X-Ray Diffraction Analysis Techniques to Monitor Composition Fluctuations within the Mineral Group: Apatite," Appl. Spectrosc. 22, 412-414 (1968)