Li+-induced triple optimization strategy for enhancing upconversion luminescence, anti-thermal quenching and optical thermometry performance in Yb2W3O12: Er3+ phosphors

Lanthanide (Ln3+)-doped A2M3O12-type negative thermal expansion (NTE) materials have received increasing attention as luminescent materials with thermal enhancement effects. However, it is highly desirable to develop effective methods to further improve their properties. Herein, the effects of Li+ co-doping on the structure, morphology, hygroscopicity, thermal expansion behavior, upconversion luminescence (UCL) property and optical thermometric performance of Yb2W3O12: Er3+ NTE materials are investigated in detail. X-ray diffraction (XRD) analysis reveals that the preferential occupancy of Li + ions in the void spaces of the Yb2W3O12 structure results in an expansion of host lattice and a slight change of the NTE behavior. Thermal analysis indicates that the presence of Li + ions reduces the intrinsic hygroscopicity of Yb2W3O12. Upon 980 nm excitation, enhancements in both the emission intensity and anti-thermal quenching capacity of Er3+ ions are achieved through the incorporation of 3 mol%Li+, which is mainly attributed to the improved structural rigidity and weakened cross-relaxation processes between Er3+ ions. When the temperature sensing is based on the intensity ratio of 2H11/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions (I527/I659), the absolute sensing sensitivity (Sa-max = 503 × 10−4 K−1) and relative sensitivity (Sr-max = 1.4 %K−1) of Yb2W3O12: 5 %Er3+, 3 %Li+ are higher than those of the sample without Li+ co-doping (Sa-max = 308 × 10−4 K−1, Sr-max = 1 %K−1). The present findings may shed light on optimizing the application performance of Ln3+ ions doped A2M3O12 phosphors.