Luminescence thermometry below room temperature via up-conversion emission of Y2O3:Yb3+,Er3+ nanophosphors

This study explores potential of Er3+-Yb3+ doped phosphors for up-conversion luminescence thermometry in the temperature range from 10 K to 300 K. Yttrium oxide nanopowder doped with trivalent ytterbium and erbium ions (Y1.97Yb0.02Er0.01O3) was prepared by hydrothermal synthesis as an example. The intensity ratios of up-conversion emissions from thermally coupled 2H11/2 and 4S3/2 levels of Er3+ show strong temperature dependence (in the range 150 K–300 K) with much higher relative sensitivity than those reported for thermometry above room temperature with Er3+-Yb3+ based up-conversion materials. The maximal value of relative sensitivity is 5.28%K−1 at 150 K, with temperature resolution ranging from 0.81 K to 0.06 K. In addition, the intensity ratios of emission from thermally non-coupled Er3+ levels (2H9/2 and 4F9/2) and from 4S3/2 also show temperature dependence that can be approximated with an exponential function. With these up-conversion emission ratios, it is possible measure temperature in the range of 10 K to 300 K with excellent sensitivity and resolution.