High sensitivity thermometry using Yb3+/Er3+ co-doped LuNbO4 nanoparticles over a wide temperature range

Abstract

Improving the sensitivity of thermometry systems is an important objective. In this study, the modified molten salt method was used to prepare Yb3+/Er3+ co-doped LuNbO4 nanoparticles with uniform size and morphology. By considering the 2H11/2 and 4S3/2 levels of Er3+ ions as the thermal coupling energy levels, an up-conversion thermometer based on LuNbO4:5 mol% Yb3+ and 1 mol% Er3+ nano-phosphor was implemented with the fluorescence intensity ratio read-out method. The experimental results indicated that the LuNbO4:5 mol% Yb3+, 1 mol% Er3+ nanoparticles exhibited excellent optical thermometric sensitivity. The maximum absolute sensitivity and relative sensitivity were 0.0084 K–1 (at 673 K) and 11.34 %K−1 (at 93 K), respectively. The high absolute sensitivity may be attributed to the relatively high phonon energy of LuNbO4 (−807 cm−1), and the relative sensitivity increased with the difference in the energy level between thermally coupled levels. The temperature measurements obtained using LuNbO4:5 mol% Yb3+, 1 mol% Er3+ nanoparticles exhibited excellent repeatability, and luminescence thermometry could be implemented over a wide temperature range of 93–673 K. Our experimental results indicate that LuNbO4:5 mol% Yb3+, 1 mol% Er3+ nanoparticles have potential applications in high-sensitivity optical thermometry over a wide temperature range, and they are also ideal candidates for use in thermometers.