Structural and luminescence properties of Ce3+-doped hydroxyapatite nanocrystalline powders

Ce3+-doped apatites have been synthesized by precipitation method in the range of the Ce/Ca atomic ratio in solutions from 0.05 to 5%. Obtained precipitates were studied with X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, EDX and luminescence spectroscopy. Cerium content in the synthesized apatites reaches 0.33 apfu (Ce/Ca = 3.9%). Relations between Ce content in the solution and precipitate have been established. It was revealed that during synthesis Ce-monazite starts to precipitate as a secondary phase at 1% Ce/Ca ratio in starting solution. Doping concentration effect on the luminescence intensity and lifetime of HAp:Ce3+ nanophosphors was studied in detail. Optimum doping concentration of Ce3+ ions in hydroxyapatite host was determined to be 0.3% of the Ce/Ca atomic ratio, which corresponds to 0.5% of the Ce/Ca ratio in the starting solution. The luminescence quenching occurs through energy transfer among the nearest neighbor Ce3+ ions.