Temperature Sensing Properties base on Up-Conversion Luminescence for NaYF4: Er3+, Yb3+ Phosphor

EDTA was used as chelating agent to synthesize Er3+, Yb3+ co-doped NaYF4 phosphor by hydrothermal process. The crystallographic structures were characterized by X-ray Diffraction (XRD). The morphologies were analyzed by field emission scanning electron microscopy (FE - SEM). It can be known that with the increase of the EDTA/Re3+, the crystalline phase of samples change from phase to the phase. The temperature-dependent up-conversion emission spectra of the samples have been tested by the 980nm laser excitation. Temperature sensing properties of samples were studied based on the fluorescence intensity ratio for two thermally coupled levels H-2(11/2) and S-4(3/2) of Er3+. The results show that the optical temperature sensing sensitivity increased gradually along with the EDTA/Re3+ increasing, no matter the samples are phase or phase. And the sensitivity maximum of phase samples is 0.00419K(-1) (at 486K, EDTA/Re3+=3), the sensitivity maximum of phase samples is 0.00466K(-1) (at 550K, EDTA/Re3+=8). But the relative sensitivity has nothing to do with the amount of EDTA, only related to the crystalline phase. The relative sensitivity maximum of phase samples is about 0.0105K(-1) (at 303 k), the maximum relative sensitivity of phase samples is about 0.0120K(-1) (at 303 k). So, temperature sensing properties of phase are better than that of phase.