Fabrication and spectroscopic properties of hot-pressed Tb:CaF2 transparent ceramics with different doping concentrations

High quality of x at.% Tb:CaF2 (x = 1, 3, 5, 7, 9) transparent ceramics prepared by hot-pressed sintering achieved an average transmittance at 1500 nm of 88%. The effect of Tb3+ concentrations on the phase composition, microstructure, emission spectra, and fluorescence decay dynamics of Tb:CaF2 transparent ceramics were investigated. XRD and FESEM results demonstrated that the incorporation of Tb3+ did not cause significant changes in the crystal structure of CaF2, and the grain size gradually decreased with increasing Tb3+ doping concentration. Under the excitation of 350 nm, the strongest emission peak was located at 542 nm, which was attributed to the 5D4→7F5 transition of Tb3+. The green emission intensity enhanced linearly with increasing Tb3+ concentration from 1 at.% to 9 at.%. The fluorescence lifetime of 5D4 level was also investigated, and the values were comparable to the corresponding single crystals. All the results suggest that Tb:CaF2 transparent ceramic is a kind of potential green luminescence material.