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 Tb 3+ /Pr 3+ :NaGd(MoO 4 ) 2 micro‐octahedrons are directionally synthesized. Originated from the diverse thermal responses between Tb 3+ ‐Mo 6+ and Pr 3+ ‐Mo 6+ IVCT states, fluorescence intensity ratio of Pr 3+ to Tb 3+ 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 Tb 3+ /Pr 3+ codoped oxide crystals having d 0 electron configured transition metal ions (Ti 4+ , V 5+ , Mo 6+ , or W 6+ ), such as scheelite NaLu(MoO 4 ) 2 and NaLu(WO 4 ) 2 , and monazite LaVO 4 and perovskite La 2 Ti 3 O 9 , evidencing the universal validity of the proposed strategy. This work exploits an effective pathway for developing new optical temperature sensing materials with high performance.