Temperature sensing behavior in Yb~(3+)-Tb~(3+) and Eu~(3+) doped Ca_2Gd_8(SiO_4)_6O_2 phosphors based on upconversion and downshifting luminescence

摘要

To develop new phosphor materials for optical temperature sensing application, a series of Yb_(3+)–Tb_(3+)and Eu_(3+)doped Ca~(2)Gd~(8)(SiO~(4))~(6)O~(2)(CGS) phosphors were designed by solid-state reaction method. Upon 980 nm excitation, the green emission of Tb_(3+)was observed in the CGS:0.8Yb_(3+), xTb_(3+)(0.08 ≤ x ≤ 1.2) phosphors, which could be mainly owing to the cooperative energy transfer from Yb_(3+)to Tb_(3+). 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 Tb_(3+)emission intensities of I~(5D4)and I~(5D3)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 Eu_(3+ 5)D~(0,1)–_(7)F~(J)transitions were found in the Eu_(3+)-activated CGS. The investigation on temperature-dependence reveals that with increasing temperature the intensities of_(5)D~(0)–_(7)F~(J)transitions decrease but those of_(5)D~(1)–_(7)F~(J)transitions increase gradually, owing to the thermally coupled_(5)D~(0)and_(5)D~(1)levels. The fluorescence lifetime based temperature sensing properties was studied in this sample.