Size influence on optical thermometry of Er3+/Yb3+ Co-doped Y2O3 microspheres: From TCLs and Non-TCLs

Realization and optimization of enhanced/tunable optical luminescence properties is highly demanded for reliable and accurate temperature sensing. In this work, uniform monodisperse spherical Er-3(+)/Yb3+ co-doped Y2O3 microcrystals of four different sizes have been synthesized via homogeneous precipitation by changing the reaction time, and the tuning of luminescence intensity/color was achieved by the controllable particles size. On this basis, by studying the particle size dependence of temperature sensing performance, we found that the behavior of absolute sensitivity (S-a) and relative sensitivity (S-r) have highly size dependence. Interestingly, when different FIR strategies were used (thermally coupled levels (TCLs) and nonthermally coupled levels (non-TCLs)), the sensitivity exhibits the opposite behavior. Importantly, when using the non-TCLs strategy, the maximum S-a value for the smallest phosphors was 1.084 K-1, leading to similar to 246 times improvement compared to TCLs-based S-a. The ultrahigh S-a indicated that the Er3+/Yb3+ co-doped Y2O3 phosphors have potential in temperature detection, and the results are of guiding significance to studying the sensitivity of Y2O3 particle size-dependent temperature measurement.