X-ray excited luminescent properties of apatitic compounds Ba5(PO4)3X (X: OH−, Cl−, Br−); structure and hydroxyl ion conductivity of barium hydroxylapatite

Ba5(PO4)3X (X: OH−, Cl−, Br−) have been synthesized by the solid-state reaction methods. The X-ray excited luminescent properties of these compounds were investigated, and chloride and bromide compounds showed broad emission band with the peak center at about 400 nm while no luminescence of Ba5(PO4)3OH had been observed. The structure of Ba5(PO4)3OH was redetermined by X-ray powder diffraction methods and the result of Rietveld refinement is P63/m, a = 10.1327(3) Å and c = 7.7526(3) Å. The ionic conductivity measurement of Ba5(PO4)3OH showed its ionic conductivity reached the maximum of 2.0 × 10−6 S/cm at 400 °C with an activation energy as low as 0.43 eV due to the activity of OH groups along the channels.