Preparation and temperature sensing properties of Er3+/Yb3+ doped La2O3, La2O2S, and La2O2SO4 phosphors

In this study, three types of Er 3+ /Yb 3+ ion co-doped La 2 O 3 (LO), La 2 O 2 S (LOS), and La 2 O 2 SO 4 (LOSO) up-conversion phosphors with identical morphology and size were successfully synthesized using a homogeneous precipitation method combined with a sulfurization process. The research compares the up-conversion luminescence (UCL) properties of these three phosphors under 980 nm near-infrared excitation. It evaluates their optical temperature sensing performance based on the fluorescence intensity ratio (FIR), while also proposing their luminescence mechanisms. In addition, the phonon energy of the three matrices was determined using FT-IR and Raman spectroscopy, and the influence of the phonon energy on the sensitivity of the up-conversion (UC) non-contact thermometer was discussed. The results indicate that the UCL of the LOS system is the strongest among the three different matrix systems. Notably, when examining the thermosensitive behavior based on the thermally coupled levels (TCLs) ( 2 H 11/2 / 4 S 3/2 ), it was found that the maximum absolute sensitivity (S a-max ) of the three samples followed the trend: LOSO (0.00811 K -1 ) > LOS (0.00627 K -1 ) > LO (0.00607 K -1 ); this trend is consistent with the degree of matching (MD) between their phonon energies and energy gaps (ΔE). These findings provide valuable insights for selecting appropriate host materials with the desired thermometric capabilities and offer guidance for enhancing the thermometric performance of non-contact thermometers.