Yb3+/Er3+ co-doped Gd2Te4O11 nanosheets with intrinsic polarity: One-step hydrothermal synthesis and upconverted optical temperature measuring ability

Abstract

The digadolinium tellurite phosphors of Gd2Te4O11(GTO):Yb3+/Er3+ have been successfully synthesized as upconversion luminescence (UCL) materials via one-step hydrothermal method. The crystal structure, morphology, and upconversion luminescence property were systematically characterize by XRD, SEM, and spectroscopy techniques. The Rietveld refinements of crystal structure were carried out on the XRD patterns and the feature of crystal structure was analyzed. Under the 980 nm NIR excitation, these materials showed very bright upconverted emissions. The concentrations of Yb3+ and Er3+ were optimized and the strongest upconverted emissions were achieved in the GTO:15%Yb3+/1%Er3+. The possible energy transfer mechanism of UCL was proposed based upon the analysis of power-dependent UCL and fluorescence kinetics. Furthermore, the fluorescence intensity ratio (FIR) derive from the two thermally coupled energy levels (2H11/2 and 4S3/2) of Er3+ was employed as indicator for temperature measurement. The maximum absolute sensitivity can be achieved to be 7.34 × 10−3 K−1 at 501 K. This material exhibited good reliability and repeatability in optical temperature measurement, which could be a novel promising candidate for noncontact temperature sensors.