Influence of Doping and Excitation Powers on Optical Thermometry in Yb3+-Er3+ doped CaWO4

Optical thermometry has been widely studied to achieve an inaccessible temperature measurement in submicron scale and it has been reported that the temperature sensitivity depends mainly on host types. In this work, we propose a new method to improve the optical temperature sensitivity of Yb 3+ -Er 3+ co-doped CaWO 4 phosphors by doping with Li + , Sr 2+ , and Mg 2+ ions and by controlling excitation powers of 980 nm laser. It is found that the thermometric parameters such as upconversion emission intensity, intensity ratio of green-to-red emission, fluorescence color, emission intensity ratios of thermally coupled levels ( 2 H 11/2 / 4 S 3/2 ), and relative and absolute temperature sensitivity can be effectively controlled by doping with Li + , Sr 2+ , and Mg 2+ ions in the Yb 3+ -Er 3+ co-doped CaWO 4 system. Moreover, the relative sensitivity S R and the absolute sensitivity S A are proved to be dependent on the pump power of 980 nm laser. The sensitivities of S R and S A in Yb 3+ -Er 3+ co-doped CaWO 4 increase about 31.5% and 12%, respectively, by doping with 1 mol% Sr 2+ .