Advanced Functional Materials, Vol.26, No.18, 3139-3145, 2016
A Novel Optical Thermometry Strategy Based on Diverse Thermal Response from Two Intervalence Charge Transfer States
In this work, a novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer (IVCT) states in oxide crystals is proposed, which provides a promising route to design self-referencing optical temperature sensing material with superior temperature sensitivity and signal discriminability. Following this strategy, uniform Tb3+/Pr3+:NaGd(MoO4)(2) micro-octahedrons are directionally synthesized. Originated from the diverse thermal responses between Tb3+-Mo6+ and Pr3+-Mo6+ IVCT states, fluorescence intensity ratio of Pr3+ to Tb3+ in this material displays excellent temperature sensing property in a temperature range from 303 to 483 K. The maximum absolute and relative sensitivity reaches as high as 0.097 K-1 and 2.05% K-1, respectively, being much higher than those of the previously reported optical thermometric materials. Excellent temperature sensing features are also demonstrated in the other Tb3+/Pr3+ codoped oxide crystals having d(0) electron configured transition metal ions (Ti4+, V5+, Mo6+, or W6+), such as scheelite NaLu(MoO4)(2) and NaLu(WO4)(2), and monazite LaVO4 and perovskite La2Ti3O9, evidencing the universal validity of the proposed strategy. This work exploits an effective pathway for developing new optical temperature sensing materials with high performance.