Paper SS-TuP8
Preparation and Characterization of Metal-doped Calcium Phosphate

Tuesday, October 31, 2017, 6:30 pm, Room Central Hall

Ti-doped Hydroxyapatite (TiHAp) partially substituted Ca²⁺ with Ti⁴⁺ exhibits excellent photocatalytic decomposition of organic compounds, as TiO₂ shows. Although the mechanisms of phtocatalytic activities of TiHAp are still unclear, Ti-doping and/or defects derived from Ti-doping are thought to be important in photocatalytic reactions. Here, we tried to fabricate beta-tricalcium phosphate (β-TCP), with substitution of Ca sites or PO₄ sites with M or MO₄ (M = Ge, Zr, Nb, Mo, Sn, W), respectively, and to study the effect on crystal structure and photocatalytic activity.

M-doped β-TCPs were prepared by solid-state or coprecipitation methods. By solid-state method, CaCO₃ and CaHPO₄・2H₂O with GeO₂, Nb₂O₅, or SnO₂ (Ca / (P + M) = 1.50, M / (P + M) = 0.01~0.03) were mixed with an alumina mortar. Samples were obtained after calcination at 1000°C for 10 h. By coprecipitation method, Ca(NO₃)₂・4H₂O and H₃PO₄ with ZrCl₂O・8H₂O, (NH₄)₆Mo₇O₂₄・4H₂O, or (NH₄)₁₀W₁₂ O ₄₁・5H₂O (Ca + M) / P or Ca / (P + M) = 1.50, M / (Ca or P + M) = 0.01~0.10) were dissolved in ion-exchanged water, and stirred for a while. After that, dil. NH₃ aq. was slowly added to the solution until pH became 9.5. The precipitation was filtered, dried at 100°C, and calcinated at 1000°C for 24 h. The obtained powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) measurements.

XRD measurements indicated that the samples were mainly β-TCP. In the case of Zr, Mo, and W doping, the obtained samples exhibited β-TCP single phase at low doping concentrations. Against doping of Ge, Nb, and Sn, β-TCP was obtained with other phases such as hydroxyapatite (HAp). In this presentation, structure, adsorption of organic/inorganic compounds, photocatalytic activity will be also discussed.