Photoluminescence properties of Er and Eu ions based on oxide host for optical temperature sensing with high sensitivity.

Motivated from increasing demands of non-contact optical temperature sensing, the Yb-Er and Eu doped NaYSiO (NYS) oxide phosphors were designed by high-temperature solid-state reaction method. The phase purity of the as-prepared samples was checked from XRD patterns. For the upconversion luminescence in NYS:Yb,Er, the optimal Er doping content was determined to be 1 mol%, and the characteristic emission peaks of Er were observed in the region of 500-700 nm. In Eu activated NYS phosphors, it has been found that the emissions originating in D and D levels demonstrate different change tendencies in intensity with Eu doping concentration. By studying the temperature-dependent luminescent spectra, it was indicated that the emissions intensities from different excited states of Er change differently with temperature. Two kinds of fluorescence intensity ratio (FIR) strategies were used in NYS:10%Yb,1%Er, containing thermally-coupled levels and non-thermally-coupled levels. In the NYS:3%Eu phosphor, it was found that the FIR for 577 and 536 nm emissions follows a linear relation with temperature. The high sensitivities in the present phosphors indicate the potential application in optical temperature sensing.