Temperature sensing properties and color tunability of 12CaO·7AlO:Tm/Ho/Yb polycrystals.

The ///127 polycrystal exhibiting white light emission has been successfully prepared by the high-temperature solid-state method. The temperature dependence of upconversion luminescence in , , and -doped C12A7 polycrystal was studied under 980 nm excitation. From 403 to 623 K, the ///127 polycrystal offers temperature-dependent color-tuning properties, and the color can be changed from white to green by simply tuning the temperature. Compared to the fluorescence intensity ratio (FIR) temperature measurement technology based on thermal coupling levels (TCLs) of rare-Earth ions, non-thermal coupling level (NTCL) FIR technology can greatly improve the temperature measurement sensitivity. The absolute sensitivity () value of the TCLs-FIR (/) was 2.51×10 of ///127 polycrystal. The NTCLs-FIR (/) had a value of 1.5×10, which achieved a significant increase in temperature sensitivity compared to the former. It provides a strategy to achieve accurate sensitivity of FIR technology. This research has implications for the study of optical temperature sensors and multi-color variable temperature display materials.