High-sensitivity Temperature Sensing via Color Change: A Study on the Thermal Coupling and Non-thermal Coupling Energy Levels in YVO4:Tm3+/Er3.

In this study, a highly sensitive fluorescence temperature sensing strategy accompanied by color change, based on thermal population and non-radiative transition, has been developed. To enhance the temperature sensitivity in high-temperature regions and to observe significant color changes with the naked eye, the fluorescence spectrum based on thermal population and non-radiative transition has been discussed and designed. The co-doped YVO4:Tm3+/Er3+ luminescent material was prepared by the high-temperature solid-phase method. Utilizing the strong absorption of ultraviolet (UV) by the V-O charge transfer band, the material was excited with 310 nm UV light. A significant color change from blue to blue-green and finally to green was achieved in the luminescent material within the temperature range of 450 K. The two fluorescence intensity ratios (FIR) were analyzed. In the high-temperature region, the FIR from the non-thermal coupling levels 1G4 and 2H11/2 satisfy the Boltzmann distribution. The relative sensitivity (Sr) reached its maximum at 593 K, with a maximum value of 1.74% K- 1. Temperature uncertainty was analyzed, and CIE chromaticity coordinates were obtained for various temperatures. This strategy increased the sensitivity by 8.5 times at 593 K compared to the thermal coupling level temperature measurement strategy. A color transition recognizable by the naked eye was achieved within the 450 K range, demonstrating thermal anti-behavior, providing a reference for enhancing relative sensitivity in high-temperature regions.