Synthesis and photoluminescence properties of Eu3+-Doped calcium phosphates

Eu3+-doped (1-12 mol%) calcium hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) powders were synthesized by a precipitation method and their photoluminescence (PL) properties were investigated. Eu has a limited solubility in HA and Eu2O3 was detected by X-ray diffraction above 3% doping, whereas a nearly single beta-phase was obtained up to 6% doping in TCP but EuPO4 appeared in the 12% Eu-doped specimen. Electron spin resonance measurement confirmed that europium ions exist as Eu3+ in both samples. Eu3+-doped HA exhibited a strong emission at 575 nm with several minor peaks at 610-640 nm and Eu3+-doped TCP had an intense emission at 613 nm with secondary peaks at 590-600 nm, which were consistent with the earlier reports determined at low temperatures. In Eu-doped TCP, the PL intensity increased with increasing calcination temperature without phase transformation. The more the Eu added, the higher the PL intensity obtained in both cases.