Molecular and Crystal Structure Characterization of Calcium-Deficient Apatite

Calcium-deficient hydroxylapatite (CDHA) powders with Ca/P ratios from1.5 to 1.67 were synthesized by wet-chemical method. Rietveld structure refinement was performed on the X-ray diffraction data and Fourier transform infrared spectroscopy was used to characterize molecular and crystal structure of CDHA. With the decrease of Ca/P ratio, the crystallite size and crystallinity decreased, but the acid phosphate content and amount of vacancies in hydroxyapatite hexagonal structure increased. The disorder of CDHA structure increase indicated calcium-deficiency and HPO4 replacement resulted in disorder of crystal in apatite structure. The more calcium is deficient, the more disorder or imperfect in CDHA structure