Temperature sensing behavior in Yb3+–Tb3+ and Eu3+ doped Ca2Gd8(SiO4)6O2 phosphors based on upconversion and downshifting luminescence

Abstract

To develop new phosphor materials for optical temperature sensing application, a series of Yb3+–Tb3+ and Eu3+ doped Ca2Gd8(SiO4)6O2 (CGS) phosphors were designed by solid-state reaction method. Upon 980 nm excitation, the green emission of Tb3+ was observed in the CGS:0.8Yb3+, xTb3+ (0.08 ≤ x ≤ 1.2) phosphors, which could be mainly owing to the cooperative energy transfer from Yb3+ to Tb3+. The corresponding upconversion (UC) luminescence mechanism was studied by using the dependence of UC emission intensity on excitation powder. The temperature-dependence indicates that the ratio of the Tb3+ emission intensities of I5D4 and I5D3 changes with temperature, which shows a linear relationship. The high absolute sensitivity was achieved to be about 0.431 K−1. Upon 463 nm excitation, the Eu3+ 5D0,1–7FJ transitions were found in the Eu3+-activated CGS. The investigation on temperature-dependence reveals that with increasing temperature the intensities of 5D0–7FJ transitions decrease but those of 5D1–7FJ transitions increase gradually, owing to the thermally coupled 5D0 and 5D1 levels. The fluorescence lifetime based temperature sensing properties was studied in this sample.