Study on optical temperature sensing properties of YVO4:Er3+, Yb3+ nanocrystals

The YVO4: Er3+, Yb3+ phosphors with various particle sizes were prepared by a precipitation method and the crystal structure and microscopic image were characterized by means of X-ray Diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The up-conversion luminescent spectra of Er3+, Yb3+ co-doped YVO4 nanocrystals with different particle sizes have been measured. It can be found that the red-green upconversion emission intensity ratio increases with the decrease of the particle size. Furthermore, the temperature sensing properties of YVO4: Er3+, Yb3+ phosphors with different particle sizes were studied based on the change of emission intensities from two thermally coupled 2H11/2 and 4S3/2 levels of Er3+. It shows that in a relatively wide range of sensing temperature (293-603 K), the temperature sensing sensitivity of nanosized materials is somewhat higher than that of bulk material. The sensing sensitivity of the sample increases with decreasing particle size, and a relative high sensitivity of 1.112×10−2 K−1 was obtained for the sample with a particle size of 20 nm, which is about 17.3% higher than the bulk sample. Finally, physical mechanism for the size-dependence of temperature sensing sensitivity was explained and predicted.