Temperature sensing characteristics and first-principles simulation of Gd-doped NaY(WO4)2 phosphors

Up-conversion luminescence (UCL) materials have potential applications in many fields. In this work, NaY(WO4)2(NYW):1 mol%Ho3+/25 mol%Yb3+ up-conversion luminescent materials doped with different Gd3+ ion concentrations were synthesized by high-temperature solid-state method. X-ray diffraction and infrared absorption spectra show that the incorporation of Gd3+ ions increases the lattice parameters and changes the stretching vibration of O–W–O bonds. The properties of the obtained UCL materials were also studied under the excitation of a 980 nm laser. All the samples show strong green and red up-conversion emission peaks centered at 542 nm and 645 nm, which correspond to the Ho3+ ion 5F4/5S2→5I8 and 5F5→5I8 energy levels, respectively. The pumping power coefficient shows that the emission at 542 nm and 645 nm is a two-photon process. The temperature dependence of the red-green emission ratio under 980 nm excitation was studied in the range of 343 K–693 K. According to thermal quenching theory, the fluorescence intensity ratio (FIR) is a function of temperature, and the sensitivity of the obtained phosphor reaches its maximum value at 343 K. These results show that NYW:Ho/Yb/Gd UCL is worthy of further study due to its potential for applications in the fields of up-conversion lasers, bioluminescence labeling, and temperature sensing.