Effect of Eu3+ Concentration on Luminescent Properties of Calcium Hydroxyapatite

Spectral and kinetic characteristics of calcium hydroxyapatite samples Ca10(PO4)6(OH)2 doped with Eu3+ ion (1, 5, and 10 mol %) were studied. The hydroxyapatite samples were presented in two forms: as-synthesized powders and heat-treated powders at 1300°C in air. Under 266 nm pulse laser excitation, they exhibited luminescence by the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions in the range of 550–750 nm. A study of luminescence decays at emission wavelengths of 574 nm (5D0 → 7F0 transition) and 590 nm (5D0 → 7F1 transition) showed a complex character of luminescence decay for as-synthesized samples and predominantly monoexponential luminescence decay for heat-treated samples. With the increase of Eu3+ concentration, the luminescence effective decay times for these transitions decreased for as-synthesized samples, whereas the luminescence lifetimes displayed almost the same values for the heat-treated samples.