Effects of Various Ions on the Synthesis of Barium Apatite obtained by Homogeneous Precipitation Method

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In this study, the barium apatite (Ba_5(OH) (PO_4)_3) was prepared at 98(±1)℃ by the homogeneous precipitation method from the mixed solution of Ba^<2+>, NaH_2PO_4 and urea. We investigated the effects of concentrations of Ba^<2+> and Cl^-, and pH of the reaction solution for the composition of the barium apatite. The barium hydrogenphosphate was obtained in the reaction solution at first. The barium hydrogenphosphate was transformed into the barium apatite by aging in the mother solution. The mixture of barium hydrogenphosphate and barium apatite was obtained in the starting reaction solution including 0.50 mol dm^<-3> urea and 0.06 mol dm^<-3> total phosphoric oxoacid ion (Ba^<2+>/P mole ratio=1.17∿1.50) after heating for 20 hours. The amount of barium apatite in the precipitate was increased by increasing the Ba^<2+>/P mole ratio. The barium apatite was obtained at the Ba^<2+>/P mole ratio=1.67. The barium hydrogenphosphate wasn't transformed into the barium apatite at all in the reaction solution without Cl^-, but it be into the barium apatite in a short time and the amount of Cl^- incorporated increased by an increase in the concentration of Cl^-. The amount of CO^<2->_3 incorporated in the barium apatite decreased with decreasing the concentration of urea and with increasing the concentration of Ba^<2+> when the Ba^<2+>/P mole ratio was 1.67.
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