Luminescence properties and temperature characteristics of Yb³⁺/Nd³⁺/Ho³⁺ triple doped BaGeTeO₆ up-conversion phosphors under 980 nm excitation

BaGeTeO₆: Nd³⁺/Yb³⁺/Ho³⁺ green up-conversion phosphors were synthesized using the high-temperature solid-state reaction method. The optimal doping concentrations for the three dopant ions Nd³⁺, Yb³⁺, and Ho³⁺ were determined to be 1 mol%, 6 mol%, and 0.8 mol%, respectively, through the method of controlling variables. By analyzing the dependence of the up-conversion luminescence intensity on the pump current of the 980 nm laser, it was found that the green and red up-conversion emissions of Ho³⁺ ions under 980 nm laser excitation were both two-photon processes. Furthermore, the influence of temperature on the up-conversion luminescent properties of BaGeTeO₆: Nd³⁺/Yb³⁺/Ho³⁺ green up-conversion phosphors under 980 nm laser excitation was investigated, and the temperature sensing properties of Ho³⁺ ions were discussed. The results indicated that, at room temperature and higher temperatures, both the red and green up-conversion emissions of the sample were two-photon processes. Within the range of excitation current used in the experiment, the ratio of red to green up-conversion luminescence intensity of Ho³⁺ ions was independent of the laser excitation current but correlated with the sample temperature. In the temperature range of 303–723 K, the ratio of red to green up-conversion luminescence intensity of Ho³⁺ ions exhibited a nonlinear relationship with temperature. Comparing the temperature sensing sensitivity of Ho³⁺ in different matrices, the results indicated that the sample possessed high temperature sensing sensitivity.