Effect of molybdenum on upconversion emission and temperature sensing properties in Na0.5Bi0.5TiO3:Er/Yb ceramics

Na0.5Bi0.49-xEr0.005Yb0.005MoxTiO3 (i.e., NBT:0.5%Er/0.5%Yb/x%Mo) ceramics were synthesized by a conventional solid-sate reaction method. Under 980 nm excitation, all the samples exhibited strong green and red upconversion emissions. With moderate addition of Mo ions, the upconversion emission intensities were enhanced. Furthermore, the optical temperature sensing properties based on the green upconversion emission of NBT:0.5%Er/0.5%Yb/0.3%Mo ceramic were also investigated. Ultimately, the fluorescence intensity ratio of two thermally coupled levels (2H11/2, 4S3/2) was studied as a function of temperature in the range of 173–553 K. The maximum sensitivity was found to be about 0.0035 K−1 at 493 K and no significant decrease was observed with further increment of temperature.