Developing novel optical thermometry with ultrahigh relative sensitivity and temperature resolution has become a cutting-edge topic. For this purpose, under obeying Boltzmann distribution , a series of Li 2 Zn 0.9992-x A x Ge 3-y B y O 8 :0.08% Cr 3+ (B= Sc 3+ , In 3+ , A = Si 4+ ) phosphors were studied, which the luminescence intensity ratio between the transition of 4 T 2g → 4 A 2g emission and the R line based on thermally coupled energy levels constitutes a temperature sensing work with a relative sensitivity of 9.46% K −1 , 9.73% K −1 , and 10.38% K −1 , respectively. It is worth mentioning that the luminescence intensity of the R line (peak 1) increases significantly with the increase of temperature, while the transition of 4 T 2g → 4 A 2g (peak 2) with high intensity at low temperature gradually quenching, and this opposite trend is an important advantage for the design of excellent thermometers. Compared the best relative sensitivity of Li 2 Zn 0.9992-x A x Ge 3-y B y O 8 :0.08%Cr 3+ (B= Sc 3+ , In 3+ , A = Si 4+ ) with the crystal field Dq /B, it can be concluded that relative sensitivity increasing gradually with decreasing the intensity of crystal field. Finally, by testing the stability of the sample at 50 K, a thermal resolution of 0.082 K, 0.080 K and 0.077 K was obtained, respectively, which is one of the best thermal resolutions so far, while the repeatability of the sample stability at 50 K and 300 K cycles was higher than 99%. Our work is expected to provide guiding insights for optimizing the sensitivity of Cr 3+ -based luminescence intensity ratio thermometers.
In this study, La 2 (MoO 4 ) 3 doped with Eu 3+ was synthesized by the high-temperature solid-state method. The phase composition of the Eu 3+ -doped La 2 (MoO 4 ) 3 sample was confirmed by X-ray powder diffraction (XRD) analysis, and the microstructure was observed via the scanning electron microscopy (SEM). Under the excitation at 211 nm, the room temperature emission spectra of Eu 3+ in the samples with different doping levels were recorded. In addition, the prepared La 2 (MoO 4 ) 3 : x Eu 3+ ( x = 0–0.25) phosphors were color tunable. A non-contact optical thermometer with high sensitivity and high-temperature resolution was fabricated based on the different thermal quenching behaviors of the Mo–O group and Eu 3+ center. The fluorescence intensity ratio (FIR), temperature resolution (ΔT), maximum absolute and relative sensor sensitivity (Sa and Sr) of La 2 (MoO 4 ) 3 :Eu 3+ were calculated according to different thermal quenching effects between room temperature (298K) and 573K of Eu 3+ and Mo–O group. These results show that La 2 (MoO 4 ) 3 :Eu 3+ has excellent sensitivity and temperature resolution, good reversibility and reliability, as Sa = 0.0525 K -1 , Sr = 0.3724. % K −1 , ΔT = 0.0806 K and the FIR error was only 0.62%. Therefore, the Eu 3+ -doped La 2 (MoO 4 ) 3 is a promising candidate material for high performance non-contact optical thermometers.
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