Low temperature reliability and high sensitivity of dual-channel up-conversion thermometry phosphor optimized by heterovalent ions

Abstract

Poor or absent sensitivity at low temperature, as a vital deficiency of up-conversion (UC) luminescence materials, has been restricting the optimization of temperature sensing performance. Herein, UC luminescence, low temperature sensitivity and reliability were optimized concurrently by first doping Nb5+ ions in CaWO4:Er3+/Yb3+ phosphor. The UC intensity was greatly improved by heterovalent ions (Li+/Nb5+) doping, which was mutually verified with the extended decay life. Simultaneously, near constant sensitivity 0.0070 K−1 was obtained based on the sublevels 2H11/2(3)/4S3/2(1). Moreover, a high absolute sensitivity 0.0104 K−1 and a high relative sensitivity 0.0243 K−1 based on the separated levels 2H11/2/4S3/2 were achieved. More importantly, regardless of the strategy, the temperature uncertainty δT at low temperatures was less than 0.5 K, and the new temperature sensor also had good repeatability (＜3%). The above results indicate that this material is an optical temperature sensor with good application prospect, especially in low temperature demand.