Figure 7
Photoluminescence emission spectra of (a) pure HAp, HAp:Gd and the HAp:Gd/Yb/Tm powders under 370 nm excitation; photographs of the powders’ blue emission under excitation; (b) HAp:Gd/Eu powder under 394 nm excitation; (c) the time-integrated micro-photoluminescence of the HAp:Gd/Yb/Tm powder under 974 nm excitation and (d) Energy-level diagram of Yb3+ and Tm3+ transitions following 974 nm excitation.
