yue Hao

Optical temperature sensing in β-NaLuF4:Yb3+/Er3+/Tm3+ based on thermal, quasi-thermal and non-thermal coupling levels

Three methods for optical temperature sensing are investigated in the NaLuF4:Yb3+/Er3+/Tm3+ phosphor, which is prepared by a hydrothermal method. The temperature-dependent luminescence is investigated under 980 nm excitation. Utilizing fluorescence intensity ratio (FIR) technique, the temperature sensing behaviors are studied in the range of 300–600 K based on thermal coupling levels (2H11/2 and 4S3/2 of Er3+), “quasi-thermal coupling levels” (4F7/2 of Er3+ and 3F2 of Tm3+) and non-thermal coupling levels (1D2 and 1G4 of Tm3+), respectively. The maximum sensitivity is 604 × 10−4 K−1 at 300 K, which is based on non-thermal coupling levels of Tm3+. Meanwhile, the temperature dependent emission colors are discussed, which are changed from bluish green to light blue with the temperature rising. These significant results, high sensitivity and the temperature dependent multicolor emissions, indicate that the NaLuF4:Yb3+/Er3+/Tm3+ phosphor is robust for optical temperature sensing.

Stark sublevels of Er3+–Yb3+ codoped Gd2(WO4)3 phosphor for enhancing the sensitivity of a luminescent thermometer

We report a strategy for enhancing the sensitivity of an optical thermometer by utilizing the Stark sublevels. Under 980 nm excitation, the upconversion emission originating from the Stark levels of Er3+ (4S3/2(2)/4S3/2(1) and 4F9/2/4F9/2(1)) is observed in a monoclinic phase Gd2(WO4)3:Er3+/Yb3+ phosphor, which is synthesized through the co-precipitation method. The temperature sensing behavior is studied over the range of 296–620 K based on thermal coupling levels 2H11/2/4S3/2(2), 2H11/2/4S3/2, 2H11/2/4S3/2(1), 4S3/2(2)/4S3/2(1) and 4F9/2(2)/4F9/2(1) using fluorescence intensity ratio (FIR) technology. The sensitivity based on Stark sublevels 2H11/2/4S3/2(2) or 2H11/2/4S3/2(1) is almost twice more than that based on the traditional 2H11/2/4S3/2 levels. The obtained maximum sensitivity of the optical thermometer is 16.5 × 10−3 K−1 at 395 K (2H11/2/4S3/2(2)). These results suggest that the use of Stark levels is a promising approach for enhancing the sensitivity of optical thermometers.

Enhanced green emissions of Er3+/Yb3+ co‐doped Gd2(MoO4)3 by co‐excited up‐conversion processes

Improving the emission from rare earth ions doped materials is of great importance to broaden their application in bio-imaging, photovoltaics and temperature sensing. The green emissions of Gd2 (MoO4 )3 :Er3+ /Yb3+ powder upon co-excitation with 980 and 808 nm lasers were investigated in this paper. Distinct enhancement of green emissions was observed compared with single laser excitation. Based on the energy level structure of Er3+ , the enhancement mechanism was discussed. Moreover, the result of temperature-dependent enhancement revealed that the enhancement factor reached its maximum (2.5) as the sample heated to 120°C, which is due to the competition of two major thermal effects acting in the co-excited up-conversion processes. In addition, the same enhancement of green emissions was also observed in Gd2 (MoO4 )3 :Er3+ powder and NaYF4 :Er3+ /Yb3+ powder.