Effects of Er3+ and Yb3+ concentrations on upconversion luminescence and thermal sensing characteristics of Sc2O3:Er3+/Yb3+ phosphors

Sc2O3:Er3+(x mol%)/Yb3+(3 mol%) (x = 0.3, 0.5, 0.7) and Sc2O3:Er3+(0.5 mol%)/Yb3+(y mol%) (y = 1, 3, 5) phosphors were synthesized by CO2 laser zone-melting method. The upconversion luminescence (UCL) spectra of Sc2O3:Er3+/Yb3+ fluorescent materials, which were pumped by 980 nm, were measured and analyzed. The results show that the UCL intensity reaches maxima when doped with 0.5 mol% Er3+ and 3 mol% Yb3+, and the increase of Yb3+ concentration leads to reduce the ratio of green UCL to red UCL. The temperature-dependent UCL spectra of Sc2O3:Er3+/Yb3+ fluorescent materials with various Er3+ and Yb3+ concentrations were measured from 290 K to 1023 K, and the thermal sensing characteristics were revealed via the fluorescence intensity ratio (FIR) technique. The maximal relative sensitivity (SR) are almost independent of the Er3+ and Yb3+ concentration, while the maximal absolute sensitivity (SA) increases with Yb3+ concentration in the whole measurement range. Among the prepared samples, the maxima of SA and SR are achieved for the sample of Sc2O3:Er3+(0.5 mol%)/Yb3+(5 mol%),with the values of 5.34 × 10−3 K−1 (364.1 K) and 12.5 × 10−3 K−1 (290 K), respectively. Interestingly, for Sc2O3:Er3+ (0.5 mol%)/Yb3+ (3 mol%), having the highest UCL intensity, its maximum SA and SR are 4.90 × 10−3 K−1 (371.4 K) and 11.2 × 10−3 K−1 (290 K). The wide temperature sensing range and relatively high sensitivities of the fabricated materials provide excellent potential for temperature sensing.