Optical temperature sensing using upconversion luminescence in rare-earth ions doped Ca2Gd8(SiO4)6O2 phosphors.

Abstract A series of Yb3+-Er3+, Yb3+-Ho3+, and Yb3+-Tm3+ doped Ca 2 Gd 8 (SiO 4) 6 O 2 (CGS) phosphors were synthesized by solid-state reaction method, and their upconversion (UC) luminescence properties for temperature sensing were studied. Upon 980 nm excitation, the green and red emissions of Er3+ were observed, and the optimal Er3+ concentration was determined to be 3 mol%. For the CGS:10%Yb3+,yHo3+ phosphors, three emission peaks in the green, red and near-infrared region appear. It was found that the relative intensities of Ho3+ different emissions change with Ho3+ concentration, which has been explained by the cross-relaxation process. The strongest Tm3+ emission appeared at 790 nm, attributed to the 3H 4 -3H 6 transition. The optimal Tm3+ concentration was determined to be 0.5 mol%. The temperature sensing behavior was evaluated by employing the thermally-coupled or non-thermally coupled levels of Er3+, Ho3+ and Tm3+. The maximum sensitivities obtained are 3.71 × 10 − 3 and 1.12 K-1 for CGS:10%Yb3+,3%Er3+, 0.111 K-1 for CGS:10%Yb3+,3%Ho3+ and 3.3 × 10 − 4 K−1 for CGS:10%Yb3+,0.5%Tm3+, respectively. The high sensitivities indicate the present phosphors could have potential application in temperature sensing. Highlights • Different strategies for temperature sensing were introduced in the present phosphors. • The present phosphors show smooth particle surface that benefits the UC luminescence. • High sensor sensitivity has been obtained in the CGS:Yb3+-Er3+/Ho3+/Tm3+. • The present phosphors could have potential application in optical temperature sensors. [ABSTRACT FROM AUTHOR]