Y4GeO8:Er3+,Yb3+ up-conversion phosphors for optical temperature sensor based on FIR technique

Herein, we reported novel Y4GeO8:Er3+,Yb3+ phosphors elaborated via conventional solid-state reaction, and we further explored their properties as optical thermometer by using fluorescence intensity ratio (FIR) method complemented by detailed analysis on crystal structure, up-conversion luminescence and energy transfer from Yb3+ to Er3+. Upon 980 nm laser excitation, Y4GeO8:Er3+,Yb3+ phosphors present 525, 547 and 659 nm emission bands assigned to the characteristic transitions of Er3+. Furthermore, Y4GeO8:Er3+,Yb3+ samples show outstanding temperature sensing performances. To be specific, the minimal temperature resolution is 0.03 K (303 K), and the relative sensitivity of FIR can be up to 1.152%/K (303 K). Hence, Y4GeO8:Er3+,Yb3+ phosphors can be possible candidates for thermometry devices.