Self-calibrated optical thermometer LuNbO4:Pr3+/Tb3+ based on intervalence charge transfer transitions

A Pr3+/Tb3+ co-doped LuNbO4 phosphor was synthesized as a self-calibrated optical thermometer using a high-temperature solid-state method, and its structure and luminescent property were elaborately investigated. Under intervalence charge transfer (IVCT) excitation at 305 nm, the sample LuNbO4:Pr3+/Tb3+ exhibited several bands in the green and red regions, originating from characteristics transitions of Pr3+ and Tb3+ ions. Through monitoring thermo-responsive emission intensity ratios from the D-1(2) H-3(4) (Pr3+) and D-5(4) F-7(5) (Tb3+) transitions, sensitive thermometry with good signal discriminability was achieved in phosphor LuNbO4:Pr3+/Tb3+ owing to a significant difference in thermal activation energy between Pr3+ and Tb3+ under IVCT excitation. Moreover, the maximum absolute sensitivity and relative sensitivity reached about 0.024 K-1 at 493 K and 1.26% K-1 at 463 K, respectively, for the LuNbO4:Pr3+/Tb3+ sample, which implies that the present phosphor could be considered as a promising candidate for self-calibrated optical thermometers.