High-accuracy dual-mode optical thermometry based on up-conversion luminescence in Er3+/Ho3+-Yb3+ doped LaNbO4 phosphors

Due to the non-contact and high sensitivity, optical thermometry based on rare earth doped phosphors has been paid much attention to. Herein, dual-mode optical thermometers are designed using up-conversion luminescence of Er3+/Ho3+-Yb3+ doped LaNbO4 phosphors, which were synthesized for the first time by high-temperature solid-state reaction method. The LaNbO4:1Er3+:10Yb3+ and LaNbO4:1Ho3+:10Yb3+ phosphors exhibit reliable and excellent thermometric performance by combining fluorescence intensity ratio and decay lifetime for self-calibration. Specifically, the maximal relative sensitivities based on fluorescence lifetime were 0.27 %K−1 and 0.33 %K−1 for LaNbO4:1Er3+:10Yb3+ and LaNbO4:1Ho3+:10Yb3+ phosphors, respectively. The maximal relative sensitivity is 1.12 %K−1 when using intensity ratio between thermal coupling energy levels in LaNbO4:1Er3+:10Yb3+ as a detecting signal. Furthermore, the maximal relative sensitivity reaches as high as 0.98 %K−1 when taking advantage of special non-thermal coupling energy levels in LaNbO4:1Ho3+:10Yb3+. These results indicate that Er3+/Ho3+-Yb3+ doped LaNbO4 phosphors possess great potential in self-calibrated optical thermometric techniques.