Investigation on the up-conversion luminescence and temperature sensing properties based on non-thermally coupled levels of rare earth ions doped Ba2In2O5 phosphor

In general, we usually adopt the thermal coupling levels (TCLs) for measuring temperature, but the sensitivity of the temperature sensor is limited to the energy gap, which is a challenge for further improving the sensitivity. In this work, we synthesize the Ba2In2O5:Yb3+/Er3+ and Ba2In2O5:Yb3+/Ho3+ phosphors by a high temperature solid-state method. The high sensitivity of the temperature sensor is obtained, which bases on the non-thermal coupling levels (NTCLs) temperature measurement. The NTCLs exhibit temperature dependent luminescence from 303 to 573 K. The maximum sensitivities of the Ba2In2O5:Yb3+/Er3+ and Ba2In2O5:Yb3+/Ho3+ phosphors are 0.48 K-1 (303 K) and 0.034 K-1 (303 K), respectively. The results show that the Ba2In2O5:Er3+/Yb3+ and Ba2In2O5:Ho3+/Yb3+ phosphors may be ideal candidates for optical temperature sensors.