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SrF 2 transparent ceramic is a promising upconversion material due to the low phonon energy. The effect of different sintering temperatures on Er:SrF 2 transparent ceramics was investigated. The suitable sintering temperature for Er:SrF 2 transparent ceramics was 900 °C by hot-pressed sintering in this study. High quality of Er:SrF 2 transparent ceramics with different doping concentrations were obtained. The upconversion luminescence spectra and decay behavior were compared between Er:SrF 2 and Er:CaF 2 transparent ceramics with different Er3+ doping concentration. The green emission of 5 at.% Er:SrF 2 ceramic was much stronger than that of 5 at.% Er:CaF 2 ceramic, while the red emission of Er:SrF 2 ceramic was almost the same as that of Er:CaF 2 ceramic. The upconversion luminescence lifetime of Er:SrF 2 transparent ceramics was longer than that of Er:CaF 2.All the results indicated Er:SrF 2 transparent ceramics was a candidate for green fluorescent upconversion materials. [ABSTRACT FROM AUTHOR]

CaF 2 -SrF 2 hosts with substitution disorder of Ca2+/Sr2+ sites in the lattice provide lower local symmetry for RE3+ ions compared with pure CaF 2 or SrF 2 hosts, thereby facilitating more efficient 4f → 4f transitions. Here we report a study of effects of Sr2+ content on microstructure and spectroscopic properties of Nd3+ doped Ca 1-x Sr x F 2 transparent ceramic. Phase and microstructure analyses show that when x is in the range of 0–0.25, Nd: Ca 1-x Sr x F 2 nanoparticles keep pure CaF 2 phase with their size, morphology and agglomeration degree mildly changed. Increasing x from 0 to 0.2 significantly improves the luminescence intensity, emission lifetime and emission cross-section of Nd: Ca 1-x Sr x F 2 , however, hardly affects the concentration quenching. The luminescence intensities and emission lifetimes of x = 0.2 and 0.25 samples are very close, probably indicating SrF 2 phase has already formed in x = 0.25 sample. Based on the spectroscopic properties, the optimal Sr2+ content is found to be x = 0.2. • Nd: Ca 1-x Sr x F 2 keeps pure CaF 2 phase with x in range of 0–0.25, further increasing x leads to the formation of SrF 2 phase. • Changing x (0–0.25) has little influence on size and morphology of Nd: Ca 1-x Sr x F 2 nanoparticles. • I max , τ em, and σ em of Nd: Ca 1-x Sr x F 2 are increased with increasing x from 0 to 0.2, whereas FWHM and β 11/2 are decreased. • The optimal Sr2+ content is found to be x = 0.2. [ABSTRACT FROM AUTHOR]