Structure, Morphology and Upconversion Luminescence of Rare Earth Ions Doped LiY9(SiO4)6O2 for Temperature Sensing

To develop novel upconversion (UC) luminescence materials for optical temperature sensing applications, the rare earth (Yb3+, Er3+, Ho3+, and Tm3+) ions doped LiY9(SiO4)6O2 phosphors were developed. The single-phase samples were confirmed by XRD patterns. The morphology characteristics were studied via SEM and TEM techniques. When excited by 980 nm, the optimal doping concentrations for Er3+/Ho3+/Tm3+ were determined in the UC emission spectra and their characteristic emission peaks were attributed. The temperature-dependence of the UC spectra was investigated by using different strategies. The maximum absolute sensitivities were calculated to be 4.77 × 10–3 K–1 for I522/I548 (Er3+), 0.034 K–1 for I661/I522 (Er3+), 0.034 K–1 for I660/I548 (Ho3+), and 2.74 × 10–4 K–1 for I695/I789 (Tm3+), which show high sensitivity values. Among these activator ions, the Tm3+ activated sample demonstrates the largest relative sensitivity. Compared with some previous lanthanide ions activated temperature-sensing luminescence materials, the present phosphors exhibit improved sensitivities and could show potential applications for temperature sensors.