Synthesis, Cu incorporation, and deposition behavior of apatite-type LaxCa10−x(PO4)6−x(SiO4)xCuyOz

Cu-containing, apatite-type phosphate–silicate solid solutions, LaxCa10−x(PO4)6−x(SiO4)xCuyOz (x = 3, 5, and 6), were synthesized by an impregnating method into the channels of apatite-type lattice by heat treatment after Cu loading. The unit cell volume of the apatite increased with increasing amount of Cu, y = 0–0.6 for x = 3 and 6, indicating successful incorporation of Cu into the channels of the apatite lattice. The result of Rietveld analysis of a La5Ca5(PO4)(SiO4)5CuyOz (x = 5) sample indicated that the distribution of La3+ and Ca2+ cations in both 4f and 6 h sites were maintained during Cu incorporation. X-ray photoelectron spectroscopy and thermogravimetric analyses revealed that oxidation and reduction of Cu species occurred during heating up to 1100 °C and cooling in air, respectively. In addition, high-temperature X-ray diffraction analysis of the La3Ca7(PO4)3(SiO4)3Cu0.6Oz (x = 3) sample in the temperature range from 500 to 1100 °C revealed that reversible incorporation/deposition of Cu occurred, accompanied by Cu oxidation/reduction.