Double perovskite A2LaNbO6:Mn4+,Eu3+ (A = Ba, Ca) phosphors: potential applications in optical temperature sensing.

Recently, much attention has been paid to Mn4+-doped phosphors due to their strong deep-red emissions which are in demand in white light-emitting diodes. However, a key challenge for the commercialization of Mn4+-doped phosphors is their low thermal stability caused by the thermal quenching of Mn4+ luminescence. Herein, a strategy of optical temperature sensing has been developed by specifically utilizing thermal quenching to explore the potential applications of Mn4+-doped phosphors in optical temperature sensing. In this work, we report two kinds of double perovskite type phosphors, Ba2LaNbO6 (BLN) and Ca2LaNbO6 (CLN), co-doped with Mn4+ and Eu3+. Through the study of temperature-dependent spectra in a large temperature range of 298-498 K, Mn4+ and Eu3+ yield different trends where the fluorescence intensity of Mn4+ ions decreases much more rapidly compared to that of Eu3+ ions as the temperature increases. Accordingly, based on the fluorescence intensity ratio (FIR) of the luminescence of Mn4+ and Eu3+, the optimal relative sensitivity of temperature sensing in the BLN and CLN matrices could reach 2.08% K-1 and 1.51% K-1, respectively. Finally, the application potential of Mn4+-doped phosphors in temperature sensing is confirmed by analyzing different temperature sensing results in the two matrices.