Energy transfer, tunable emission and optical thermometry in Tb3+/Eu3+ co-doped transparent NaCaPO4 glass ceramics

Tb3+/Eu3+ co-doped glass ceramics containing NaCaPO4 nanocrystals were successfully synthesized via traditional melt-quenching route with further heat-treatment and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence spectroscopy. The energy transfer process of Tb3+→Eu3+ was confirmed by excitation and emission spectra and luminescence decay curves, and the energy transfer efficiency was also estimated. The results indicated that the efficient emission of Eu3+ was sensitized by Tb3+ under the excitation of 378 nm, realizing tunable emission in the transparent bulk glass ceramics containing NaCaPO4 nanocrystals. Furthermore, optical thermometry was achieved by the fluorescence intensity ratio between Tb3+:5D4→7F5 (~542 nm) and Eu3+:5D0→7F2 (~612 nm). The maximum absolute sensitivity of 4.55% K−1 at 293 K and the maximal relative sensitivity of 0.66% K−1 at T=573 K for Tb3+/Eu3+ co-doped transparent NaCaPO4 glass ceramic are obtained. It is expected that the investigated transparent NaCaPO4 glass ceramics doped with Tb3+/Eu3+ have prospective applications in display technology and optical thermometry.