Investigation on Upconversion Luminescence and Optical Temperature Sensing Behavior for Ba2Gd2Si4O13:Yb3+-Er3+/Ho3+/Tm3+ Phosphors

To explore new phosphors for temperature sensing with high detection sensitivity, the Yb3+-Er3+/Ho3+/ Tm3+ doped Ba2Gd2Si4O13 (BGS) was designed. Different strategies were introduced based on the upconversion (UC) luminescence. For BGS:0.2Yb(3+),0.02Er(3+), the fluorescence intensity ratio (FIR) of two green emissions of Er3+ shows a gradual enhancement with increasing temperature due to the thermally coupled levels. The piecewise expression of sensitivity was proposed in the temperature range of 293- 553 K based on the Boltzmann distribution. For BGS:0.2Yb(3+),0.01Ho(3+), the FIR of the red to green emissions of Ho3+ changes with temperature, showing a linear relationship from 293 to 453 K. The absolute sensitivity was gained to be 0.0452 K-1 . For BGS:0.2Yb(3+) ,0.02Tm(3+) , the high absolute and relative sensitivities were both achieved by employing the thermally coupled (F-3(2),F-3(3)) and H-3(4) levels of Tm3+. The above study could have special reference to the development of new luminescent materials with high sensitivity.