Enhancement of green upconversion luminescence and temperature sensitivity of Zr2(WO4)(PO4)2:Er3+,Yb3+ phosphors by co-doping Li+ ions

Abstract

A serious of Zr2(WO4)(PO4)2 (ZWP):Er3+,Yb3+ phosphors by co-doping Li+ ions were prepared by solid state reaction method. Based on the X-ray diffraction (XRD) and scanning electron microscope (SEM), the lattice structure and morphology of prepared samples were performed. Meanwhile, the up-conversion luminescence (UCL) spectra were measured from room temperature to 693 K under 980 nm laser excitation. With the intervention of Li+ (0.04, 0.06, 0.08, 0.10), the green UCL intensities of ZWP:0.02Er3+, xYb3+ (x = 0.02, 0.04, 0.06, 0.08) phosphors was remarkably strengthened by 4.2, 2.6, 3.3, 5.5 times at room temperature, respectively, and the thermal enhancement of 2H11/2→4I15/2 transition UCL of Er3+ was observed due to the negative thermal expansion (NTE) of ZWP host. In Addition, the co-doping Li+ enhanced the absolute temperature sensitivities, and the maximum absolute sensitivity and relative sensitivity of ZWP:Er3+,Yb3+,Li+ phosphors were derived to be 0.01345 K−1 and 0.01198 K−1, respectively. The mechanism of the enhanced UCL intensity and temperature sensing by co-doping Li+ was discussed. The obtained results indicate that the NTE Er3+/Yb3+/Li+ tri-doped ZWP phosphors with a high temperature sensitivity can be applied as optical thermometer.