NaGd9(SiO4)6O2:Yb3+-Er3+/Tm3+: Optical thermometric materials of high-sensitivity by using different strategies

Herein, a series of Er3+/Yb3+ and Tm3+/Yb3+ co-doped NaGd9(SiO4)(6)O-2 (abbreviated as NGS) phosphors were prepared by solid-state reaction method. The phase purity and optical properties were investigated systematically by XRD, luminescence spectra and decay curves. The temperature-dependent upconversion luminescence was studied by using the fluorescence intensity ratio (FIR) technique. For NGS:1%Er3+,20%Yb3+, the variation of FIR for 521 and 554 nm emissions with temperature was evaluated. For NGS:0.5%Tm3+,10%Yb3+, four emission peaks were utilized to characterize the optical temperature-sensing properties. High absolute and relative sensitivities were obtained. The above results indicated that the as-prepared phosphors could show potential applications in optical thermometer.