Hydroxyapatite powder was prepared by sol-gel method using the calcium nitrate tetrahydrate and pentoxide as reactant. The effects of main processing parameters such as reagent, concentration, temperature etc on the synthesis of hydroxyapatite were investigated. The synthetic mechanism was also studied. The results showed that main optimized parameters were as follows: 2 M ethanol solution of P2O5 and 4 M ethanol solution Ca（NO3）2·4H2O, 12-24 h of aging time, 500 ℃ sintered temperature. X-ray diffraction and Fourier transform infrared spectra results showed that the mixtures were composed of amorphous hydroxyapatite, Ca（NO3）2, PO（OH） 3-x（OR）x, bellow 400 ℃. The pure hydroxyapatite powder were prepared at 500 ℃ for 30 min. The aging of the sol influenced the purity greatly. The CaO phase was observed from the powder without aging. This process with cheap reactants was simple and the advantages offered by this process made it possible to produce the uniform fine powder in large quantity.
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