High performance FIR thermometry on the basis of the redshift of CTB by dual-wavelength alternative excitation in Eu³⁺:YVO₄

Compared with the forbidden 4f transition of rare earth ions, the strong absorption of the charge transfer band (CTB) enabled fluorescence thermometry to have high luminescence efficiency. Based on the temperature induced redshift of CTB, a high performance fluorescence intensity ratio (FIR) thermometry performed by dual-wavelength alternative excitation was studied. By way of the rising and falling edges of CTB in Eu³⁺ doped YVO₄, monochrome sensitivity as a function of excitation wavelength was studied in the range of 303–783 K. The excitation wavelength with the highest positive monochrome sensitivity was determined, as well as that with the negative one. The optimum FIR temperature sensing strategy is proposed, and the theoretical highest relative sensitivity (S_r) is calculated to be 1.86% K^-1, with the lowest uncertainty (1T) of 0.1 K at 783 K.