Herein, temperature dependencies of emission and emission decay of Zn₂SiO₄:Mn²⁺ powder in the range from room temperature to 300 °C is reported. These dependencies allow temperature sensing from luminescence measurements, since Mn²⁺ emission intensity, emission band spectral position, and emission decay are rapidly changing over the entire temperature range. For fluorescence intensity ratio method, measurement that relays on emission intensity changes with temperature, sensitivity of 12.2% is found. In the case of lifetime thermometry, method that relays on emission decay changes with temperature, sensitivity of 0.48% is determined. Both sensitivity values are among the highest ever recorded for inorganic materials.

The emission of Er³⁺ provides three combinations of emission bands suitable for ratiometric luminescence thermometry. Two combinations utilize ratios of visible emissions (²H_11/2→⁴I_15/2 at 523 nm/ ⁴S_3/2→⁴I_15/2 at 542 nm and ⁴F_7/2→⁴I_15/2 at 485 nm/ ⁴S_3/2→⁴I_15/2 at 545 nm), while emissions from the third combination are located in near-infrared, e.g., in the first biological window (²H_11/2→⁴I_13/2 at 793 nm/ ⁴S_3/2→⁴I_13/2 at 840 nm). Herein, we aimed to compare thermometric performances of these three different ratiometric readouts on account of their relative sensitivities, resolutions, and repeatability of measurements. For this aim, we prepared Yb³⁺,Er³⁺:YF₃ nanopowders by oxide fluorination. The structure of the materials was confirmed by X-ray diffraction analysis and particle morphology was evaluated from FE-SEM measurements. Upconversion emission spectra were measured over the 293–473 K range upon excitation by 980 nm radiation. The obtained relative sensitivities on temperature for 523/542, 485/542, and 793/840 emission intensity ratios were 1.06 ± 0.02, 2.03 ± 0.23, and 0.98 ± 0.10%K⁻¹ with temperature resolutions of 0.3, 0.7, and 1.8 K, respectively. The study showed that the higher relative temperature sensitivity does not necessarily lead to the more precise temperature measurement and better resolution, since it may be compromised by a larger uncertainty in measurement of low-intensity emission bands.

The samples, Lu2O3:Eu3+ (3at.% Eu) and Lu2O3:Sm3+ (1at.% Sm), were prepared via polymer complex solution method using polyethlylene-glyocol as the fuel and as nucleation agent for crystallization process. Knowing that lutetium oxide has high chemical stability and temperature resistance, in this paper we investigated possibility for its application in high-temperature phosphor thermometry. It is a non-contact technique that uses the thermal dependence of phosphor fluorescence to measure temperature remotely. The structural and morphological properties were performed through X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) investigations. The obtained results confirmed that this synthesis yields desired crystalline structure with particle size in the range from 30 to 50 nm. Photoluminescence emission measurements were recorded in the temperature range from room up to 873 K. The accomplished results demonstrate the performance of Eu3+ and Sm3+ doped Lu2O3 as high temperature thermographic phosphors of very good sensitivity.