Charge compensation improves energy transfer to realize anti-thermal-quenching and enhances the CaMoO₄: Sm³⁺ phosphors optical temperature measurement sensitivity base on the FIR model

Luminescent materials are the main focus of non-contact thermometers due to their high detection sensitivity, non-invasiveness, quick reaction, exceptional stability. It is still difficult to design high sensitivity optical temperature sensors using fluorescence intensity ratio technology. This article increases fluorescence intensity ratio value and obtains high sensitivity temperature sensitive phosphors by utilizing the anti-thermal-quenching effect of rare earth luminous centers. Sm³⁺ and alkali metal co-doped CaMoO₄ phosphors have been prepared by high-temperature solid-state method. Rietveld refinement results showed that the co-doping of Sm³⁺ and K⁺ can significantly improve the energy transfer from the host to Sm³⁺ and significantly increase the luminous intensity of Sm³⁺. We found that co-doping of Sm³⁺ and K⁺ not only effectively enhanced the luminescence intensity, but also regulated the lifetime of this phosphors. When K⁺ is introduced into the CaMoO₄: 0.02Sm³⁺, the τ value decreased from 4.12 to 3.54 ms, which proves to be effective in light-emitting diode. The optical temperature measurement of CaMoO₄: 0.001Sm³⁺, 0.001 K⁺ was studied using fluorescence intensity ratio technology. The maximum S_aMAX and S_rMAX values are 0.27 K⁻¹ at 483 K and 2.25 % K⁻¹ at 363 K, respectively. Moreover, the CaMoO₄: 0.02Sm³⁺, 0.02 K⁺ also has a certain absorption capacity in visible optical drive, which proved by ultraviolet visible diffused reflectance spectra. The electronic density of states of phosphors are drawn via first-principles to understand the effect of Sm³⁺ and alkali metals co-doped on luminescence. The above results demonstrate that the Sm³⁺ and K⁺ co-doping CaMoO₄ might be an attractive material for the application of temperature measurement and light-emitting diode.