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

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 (Y_1.97Yb_0.02Er_0.01O₃) was prepared by hydrothermal synthesis as an example. The intensity ratios of up-conversion emissions from thermally coupled ²H_11/2 and ⁴S_3/2 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 (²H_9/2 and ⁴F_9/2) and from ⁴S_3/2 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.