Influence of Chelants and Catalyst on Luminescence of CaAl<sub>2</sub>O<sub>4</sub>:Eu<sup>2+</sup> Phosphors for Optical Temperature Sensing Applications

This study synthesized CaAl 2 O 4 :Eu 2+ blue phosphors using the sol-gel method. The effects of incorporating citric acid, poly (oxyethylene) (PEG), and HCl in the precursor on the luminescent properties of phosphors were investigated. No significant changes were observed in the photoluminescence (PL) spectra of the phosphors when different precursor solutions were used. However, the use of PEG and citric acid led to a noticeable decrease in the PL intensity. Notably, the use of HCl resulted in an increase in PL. In addition, upon heating the phosphors from room temperature to 110 °C, the PL spectrum remained unchanged, whereas the PL intensity decreased linearly with increasing temperature. This indicated the suitability of CaAl 2 O 4 :Eu 2+ for optical temperature-sensing applications.