Up-conversion luminescence and optical temperature sensing of Er³⁺, Yb³⁺ co-doped Gd₂O₃ phosphors with different F^-/Ln³⁺

In this work, the Er³⁺, Yb³⁺co-doped Gd₂O₃ phosphors have been prepared through a facile hydrothermal method. The optimum doping concentration of the Er³⁺, Yb³⁺ co-doped Gd₂O₃ phosphors are studied in detail. By studying the samples calcined at different temperatures, the process of grain forming self-assembled structure was revealed. The up-conversion luminescence intensity of the phosphors can be regulated by the ratio of NH₄F and lanthanoid nitrate (F^-/Ln³⁺) in the synthesis process. The enhancement of red and green emission intensities can reach 8.0 times, 6.7 times respectively than the sample with F^-/Ln³⁺ = 0.5. In addition, the florescence intensity ratio based on thermally coupled energy levels by the Stark sublevels is also investigated. The maximal absolute sensitivity of optical temperature sensing reaches 1.27% K⁻¹ at 574 K, which is 1.51 times higher than that based on traditional thermally coupled energy levels by Stark levels. Therefore, the results show that this is a useful method to improve the absolute sensitivity of optical temperature sensing and the Er³⁺, Yb³⁺ co-doped Gd₂O₃ phosphors have application potential in high sensitivity optical temperature sensing.