Upconversion Luminescence and Optical Temperature-Sensing Properties of LaNbO4:Yb3+/Er3+ Phosphors

In recent years, upconversion (UC) luminescence has attracted considerable attention because of its potential application in temperature measurement. In this work, LaNbO4:Er3+/Yb3+ phosphors are synthesized using a solid-state method. The x-ray diffraction patterns show that the phosphors obtained exhibit a single monoclinic structure, and doping does not change the crystal structure. Intense green and red emissions are observed upon 980-nm excitation. The emission intensity varies with the doping concentration, and the best doping concentrations are 1 mol.% and 10 mol.% for Er3+ and Yb3+ ions, respectively. The possible luminescence mechanism is investigated based on the UC emission dependence on pump power. The temperature-sensing ability is also investigated based on the fluorescence intensity ratio between two thermally coupled levels 2H11/2 and 4S3/2. The maximum sensitivity achieved is 0.81% K−1 at around 430 K, suggesting that the phosphor is a potential candidate for temperature sensing applications.