Optical Temperature Sensing Based on Linear Change of Luminescence Intensity Ratio in Y₂O₃: Tm³⁺, Eu³⁺ Phosphors

In this work, Y₂O₃: Tm³⁺, Eu³⁺ phosphors were made by homogeneous precipitation with urea as precipitator. The emission spectra varying with temperature of Y₂O₃: Tm³⁺, Eu³⁺ phosphors were measured and analyzed. Analysis show that the luminescence of Eu³⁺ represents a normal thermal quenching change, while that of Tm³⁺ exhibits slow thermal enhancement phenomenon. In the temperature range of 303-503 K, the luminescence of Tm³⁺ showed a trend of first strengthening and then weakening. The reason for this phenomenon of Tm³⁺ is that there is energy transfer from Eu³⁺ to Tm³⁺, and the energy transfer efficiency increases gradually with temperature. Meanwhile, the luminescence of Tm³⁺ also have thermal quenching effect. Under the combined influence of thermal quenching and energy transfer, the luminescence of Tm³⁺ first becomes stronger and then then becomes weaker. According to the calculation, the luminescence intensity ratio (LIR) of Tm³⁺ and Eu³⁺ conforms to the linear empirical formula with increasing temperature. The relative sensitivity of phosphors decreases with Eu³⁺ concentration increased, and the maximum S_r reaches 0.460% K^-1 (1% Tm³⁺, 0.3% Eu³⁺, at 303 K). Moreover, the temperature cycle test present that the LIR of phosphors has good repeatability.