Temperature sensing properties of upconverted-emission materials based on a fluoroindate glass matrix.

The optical temperature sensing properties of a low-phonon fluoroindate glass co-doped with different trivalent lanthanide ions (IFG:Ln3+/Yb3+, Ln = Er, Tm, and Tm-Ho) were assessed using the fluorescence intensity ratio (FIR) technique. The temperature-dependent upconverted luminescence was carried out in the temperature range between 300 and 583 K using the thermally-coupled energy levels, non-thermally coupled levels, and their additional combinations. The highest relative sensitivity was obtained in the IFG:Tm3+/Yb3+ sample at 355 K (1.4% K−1), from 3F 2 , 3H 4 → 3H 6 FIR evaluation, while the maximum absolute sensitivity was found in the IFG:Ho3+/Yb3+ system at 583 K (0.020 K−1), from Tm(1G 4 →3H 6 +3H 4 →3H 6)-Ho(3F 4 →5I 7) FIR assessment. Furthermore, the chromaticity diagram (CIE) evidenced an important change of color when the temperature increased in IFG:Er3+/Yb3+ sample, because this showed an evident transition from green to yellowish. Also, the heating effect caused by 980 nm excitation is negligible in most of the samples. Additionally, their amorphous nature was confirmed by X-ray diffraction and their thermal stability was evaluated using differential thermal analysis resulting in a great glass thermal stability up to 583 ± 2 K. Therefore, IFG:RE3+/Yb3+ glass systems are considered as excellent candidate for temperature sensing. [Display omitted] • The temperature induces changes in the emission color of Er3+, Tm3+, and Ho3+ ions. • The fluoroindate glass matrix promoted thermal excitation between energy levels. • Thermal excitation favors some negligible radiative transitions. • The assessment of non-TCLs overcomes energy gap limitations and enhances sensitivity. • The FIR repeatability indicates good viability in optical temperature applications. [ABSTRACT FROM AUTHOR]