Synthesis and up-conversion of Er3+ and Yb3+ Co-doped LiY(MoO4)2@SiO2 for optical thermometry applications

Non-contact temperature sensors based on the fluorescence intensity ratio (FIR) have been widely investigated owing to their high sensitivity and reliable real-time monitoring. Herein, the SiO₂-coated LiY(MoO₄)₂@SiO₂:Er³⁺,Yb³⁺ phosphor was investigated as an optical thermometry material, which was synthesized using the conventional solid state reaction and coated by a facile wet chemical route. The effect of surface modification on FIR was systematically characterized by structural analyses and spectral measurements and the temperature-dependent up-conversion FIR was investigated from 303 to 603 K under a 980 nm laser excitation. The results showed that the FIR value was thermally stable and the SiO₂ coating led to a higher FIR sensitivity as well as a higher saturation threshold. This work would pave a way to design interesting optical thermometry materials in up-conversion phosphors with better properties.