NIR-II luminescence and temperature sensing properties based on double perovskite La2MgTiO6: Yb3+/Er3+/Ho3+ phosphor

The near-infrared-II (NIR-II) fluorescence thermometer based on rare earth-doped double perovskite is rarely. Herein, Er 3+ -Ho 3+ and Yb 3+ co-doped lead-free double perovskite La 2 MgTiO 6 (LMTO) phosphors were synthesized by a conventional high temperature solid phase method. The phase purity and morphology of the samples were analyzed using XRD and FE-SEM. The NIR-II luminescence properties of LMTO: Er 3+ -Ho 3+ -Yb 3+ phosphors were systematically investigated under laser irradiation at 980 nm. A NIR-II fluorescence thermometer was also designed based on non-thermal coupled energy levels originated from the 4 I 13/2 energy level of Er 3+ and the 5 I 6 energy level of Ho 3+ . The maximum value of relative sensitivity (S r ) was 0.54 % at 513 K. Compared to visible thermometers (LMTO: Er 3+ -Yb 3+ and LMTO: Ho 3+ -Yb 3+ ), the NIR-II thermometers offer better temperature measurement capability and penetration depth. All the experimental results show that the NIR-II thermometer with a wider range and higher sensitivity has been realized, which puts forward a new idea for the design and optimization of NIR-II thermometers.