Bright upconversion luminescence performance of Yb3+/Tm3+/Gd3+/Er3+ doped AWO4 (A=Sr or Ca) phosphor for optical temperature sensor

A series of AWO 4 (A = Sr, Ca): Yb 3+ /Tm 3+ /Gd 3+ /Er 3+ phosphors are successfully prepared by solid-state method. In comparison with the samples without Gd 3+ ions, the UC emission intensity of CaWO 4 : 0.5 mol%Tm 3+ /1 mol%Yb 3+ /10 mol%Gd 3+ sample has increased by 104 times (∼475 nm), 71 times (∼655 nm) and 23 times (∼795 nm) due to the shrink of the host lattice with the Gd 3+ ions corporation. Based on the fluorescence intensity ratio (FIR) of non-thermal couple levels(non-TCLs), the temperature sensing characteristics are investigated for AWO 4 (A = Sr, Ca): Yb 3+ /Tm 3+ /Gd 3+ /Er 3+ phosphors. The maximum values of absolute sensitivity and relative sensitivity are 0.09356 K -1 and 1.499% K −1 for CaWO 4 : Yb 3+ /Tm 3+ /Gd 3+ /Er 3+ phosphor. It indicates that the AWO 4 (A = Sr, Ca): Yb 3+ /Tm 3+ /Gd 3+ /Er 3+ phosphors can be applied to develop optical thermometry.