Dy3+-doped niobate phosphor based on charge transfer band red-shift effect: luminescence thermal stability and temperature sensing performance

Abstract

The thermal quenching behavior seriously limits the application prospect of phosphors, so it is urgent to improve the thermal quenching behavior of phosphors. It is expected that the red-shift of charge transfer band (CTB) caused by temperature can be used to improve the luminescent stability of phosphor. Therefore, we designed a family of LuNbO₄:x%Dy³⁺ (x = 0.25, 1, 2, 5) phosphors based on the characteristic of the red-shift of CTB edge, and investigated the relationship between the red-shift of the CTB edge and the luminescence thermal stability of the phosphor, further broadening the application of this phosphor in temperature sensing The effects of three different excitation positions, CTB (260 nm), CTB edge red-shift (288 nm) and Dy³⁺ 4f-4f transition (354 nm), on the luminescence thermal stability of phosphors were also investigated. It was found that only excitation in the red-shift range of CTB edge showed complete antithermal quenching behavior. The LuNbO₄:2%Dy³⁺ phosphor showed complete antithermal quenching under the excitation of CTB edge, and the comprehensive emission intensity at 573 K is 741% of that at 298 K. According to the above characteristics, a dual-mode optical thermometry based on fluorescence intensity ratio (FIR) and International Commission on Illumination (CIE) chromaticity coordinates is proposed, in which the maximum relative temperature sensitivity of LuNbO₄:x%Dy³⁺ is 5.04% K^-1 (298 K, FIR) and 3.14% K^-1 (573 K, CIE). Interestingly, when constructing CIE temperature measurement model, we found that LuNbO₄:0.25%Dy³⁺ phosphor at 260 nm excitation position has obvious color change at each temperature stage, showing temperature visualization characteristics. At 354 nm excitation position, it shows constant white light emission. The excellent optical temperature measurement performance and temperature visualization characteristics of the phosphor shows that it has excellent application potential in optical sensing.