Up-Conversion Luminescence and Temperature Sensing of Er³⁺/Yb³⁺ Codoped Y_2(1-Lu₂O₃ Solid Solution

In this paper, Er³⁺/Yb³⁺ codoped Y_2(1-Lu₂O₃ solid solution was prepared through the sol-gel method, and the substitution of Y³⁺ by Lu³⁺ ions in Y₂O₃ was confirmed by X-ray diffraction data. The up-conversion emissions of samples under 980 nm excitation and the relative up-conversion processes are investigated. The emission shapes do not vary with the change in doping concentration due to the unaltered cubic phase. The red-to-green ratio changes from 2.7 to 7.8 and then declines to 4.4 as the doping concentration of Lu³⁺ increases from 0 to 100. The emission lifetimes of green and red have similar variation: the emission lifetime decreases with doping concentration changing from 0 to 60 and rises as the doping concentration continues to increase. The reason why the emission ratio and lifetime change could be originated to the exacerbation of cross-relaxing process and the change of radiative transition probabilities. The temperature-dependent fluorescence intensity ratio (FIR) shows that all samples can be used in noncontact optical temperature sensing, and the method of local structure distortion can be used to improve sensitivity further. The max sensing sensitivities of FIR based on R _538/563 and R _red/green reach 0.011 K^-1 (483 K) and 0.21 K^-1 (300 K). The results display that Er³⁺/Yb³⁺ codoped Y_2(1-Lu₂O₃ solid solution can be potential candidates for optical temperature sensing in different temperature ranges.