Improving the up/down-conversion luminescence via cationic substitution and dual-functional temperature sensing properties of Er3+doped double perovskites

Er3+ doped phosphors are widely employed as dual-functional optical thermometers owing to their special up/ down-conversion luminescence and the thermally coupled energy states (2H11/2 and 4S3/2) of Er3+. Developing Er3+-activated optical thermometers with high performance has been an intriguing topic as well as a significant challenge. Herein, we illustrate the substitution route for alkaline earth ions to obtain the Er3+-activated ALa-LiTeO6 (A = Ba, Sr, Ca and Mg) green perovskite phosphors, exhibiting satisfactory temperature sensing prop-erties. Under 379 and 980 nm excitations, the phosphors yield emission peaks at 526, 547 and 660 nm, corresponding to the 2H11/2, 4S3/2 and 4F9/2 & RARR; 4I15/2 transitions of Er3+, respectively, among which the 4S3/2 & RARR; 4I15/2 transition is the strongest. When cationic substitutions of Ba2+, Sr2+, Ca2+ and Mg2+ are performed, the luminescent intensity is improved significantly and the inner mechanism is clearly revealed. The optical tem-perature sensing properties of the thermally coupled states are investigated based on the fluorescence intensity ratio principle. Under 379 nm light excitation, SrLaLiTeO6:0.06Er3+ possesses the maximum relative sensitivity of 0.0120 K-1, whereas BaLaLiTeO6:0.06Er3+ possesses the maximum relative sensitivity of 0.0124 K-1 under 980 nm light excitation. Therefore, these materials are the potential candidates for optical thermometer application.