Double perovskite ALaNbO:Mn,Eu (A = Ba, Ca) phosphors: potential applications in optical temperature sensing.

Recently, much attention has been paid to Mn-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 Mn-doped phosphors is their low thermal stability caused by the thermal quenching of Mn luminescence. Herein, a strategy of optical temperature sensing has been developed by specifically utilizing thermal quenching to explore the potential applications of Mn-doped phosphors in optical temperature sensing. In this work, we report two kinds of double perovskite type phosphors, BaLaNbO (BLN) and CaLaNbO (CLN), co-doped with Mn and Eu. Through the study of temperature-dependent spectra in a large temperature range of 298-498 K, Mn and Eu yield different trends where the fluorescence intensity of Mn ions decreases much more rapidly compared to that of Eu ions as the temperature increases. Accordingly, based on the fluorescence intensity ratio (FIR) of the luminescence of Mn and Eu, the optimal relative sensitivity of temperature sensing in the BLN and CLN matrices could reach 2.08% K and 1.51% K, respectively. Finally, the application potential of Mn-doped phosphors in temperature sensing is confirmed by analyzing different temperature sensing results in the two matrices.