Microemulsion synthesis and optical temperature sensor properties in HA/β-TCP composite phosphors

Herein, a novel microemulsion (ME) method for the synthesis of rare earth-element-doped hydroxyapatite (HA)/beta-tricalcium phosphate (β-TCP) composite phosphors was performed and yielded phosphors with intense green upconversion (UC) emission and high temperature sensitivity. The effect of polyvinyl alcohol (PVA) content on the structure and luminescence properties of the phosphors was investigated in detail. X-ray diffraction and Raman spectra showed that the mixed phases included the main hexagonal HA phase and the secondary orthorhombic β-TCP phase. Under 975 nm excitation, the obtained phosphors exhibited strong green UC emission, and their intensity depended on PVA content. Notably, the fluorescence intensity ratio technique revealed that the phosphors had a high color purity of up to 94.77% and high temperature sensitivity of 0.93% K^-1 at 293 K. These results indicate that the phosphors are suitable for applications in thermal sensors and optoelectronic devices.