LAUSR

Ho3+/Yb3+-codoped ZnWO4 phosphors were synthesized using a solid state reaction method and their structures, upconversion (UC) luminescence, and temperature-sensing properties were investigated. The obtained ZnWO4:0.01Ho3+/xYb3+ phosphors crystallized in the monoclinic phase with space group P2/c. Under 980 nm excitation, bright green [(5F4, 5S2) → 5I8], weak red (5F5 → 5I8), and near-infrared emissions [(5F4, 5S2) → 5I7] were observed. The optimal Ho3+ and Yb3+ doping concentrations in ZnWO4 were 0.01 and 0.15, respectively. The near-infrared-green (I757/I540) and red-green (I641,665/I540,549) fluorescence intensity ratios (FIRs) were studied as a function of temperature at 83–503 K. The sensitivity of the ZnWO4:0.01Ho3+/0.15Yb3+ phosphors was also discussed and their potential application as thermal sensors in luminescence thermometry was analyzed using a four-level system and the intensity ratio of the red and green emissions. ZnWO4:0.01Ho3+/0.15Yb3+ phosphors could potentially be applied as optical temperature-sensing materials.