High temperature-sensing performance of Er- and Yb-codoped tungsten bronze oxides based on frequency up-conversion luminescence

Novel tungsten bronze Ba 4 Gd 0.65-x Er 0.02 Yb x Nb 10 O 30 (0   ≤   x   ≤   0.1) phosphors were synthesized. Their phase and structure were characterized and analyzed by X-ray diffraction (XRD) and Rietveld structural refinements. Under 980   nm excitation, bright frequency up-conversion (FUC) green and weak red emissions were observed. The concentration of Yb 3+ had an important influence on the FUC luminescence properties and a possible UC mechanism was proposed. Temperature sensing properties of the Ba 4 Gd 0.55 Er 0.02 Yb 0.1 Nb 10 O 30 phosphor in the range from 303 to 573   K were obtained by measuring the temperature dependent fluorescence intensity ratio (FIR) of the FUC green emissions at 531 and 554   nm originated from two thermally coupled 2 H 11/2 and 4 S 3/2 emitting energy levels. A temperature-sensing sensitivity of 0.013   K −1 at 573   K was obtained experimentally and the obtained energy difference ΔE was 971   cm −1 , indicating that this material can be utilized as a promising candidate for the future optical temperature sensors of high accuracy and resolution.