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+ /Yb 3+ co-doped Y 2 O 3 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 ∼246 times improvement compared to TCLs-based S a . The ultrahigh S a indicated that the Er 3+ /Yb 3+ co-doped Y 2 O 3 phosphors have potential in temperature detection, and the results are of guiding significance to studying the sensitivity of Y 2 O 3 particle size-dependent temperature measurement. • Uniform monodisperse spherical Er 3+ /Yb 3+ co-doped Y 2 O 3 phosphors with four different sizes were synthesized. • A simple, accurate, low cost and large-scale production method was proposed. • Size-dependence of sensitivity by the FIR technique based on TCLs and novel non-TCLs were investigated in detail. • The ultrahigh absolute sensitivity ( S a ) about 108.4% K −1 under 303 K was obtained.