Tunable emission color and anti-thermal-quenching behaviors in niobates for high-sensitive optical thermometry

Non-contact remote optical thermometers as a significant technique have been extensively developed. However, it is still a challenge to design new Bismuth-doped phosphor materials with tunable spectra for high-sensitive optical temperature sensors. Herein, a novel YxLu1-xNbO4:Bi3+ (0 ≤ x ≤ 1.0) phosphor is constructed by the isomorphic end components LuNbO4 and YNbO4. Owing to the modification of crystal field strength around Bi3+ ions, the emission positions controllably shifted from 475 to 462 nm with the increase of Y3+ ions concentrations. Besides, systematic luminescence modifying from blue to red across the white light region could be achieved via the design of Bi3+→Eu3+ energy transfer (ET). Intriguingly, an anti-thermal-quenching behavior of Eu3+ ion originating from the ET is found in Y0.8Lu0.2NbO4:Bi3+, Eu3+ (YLNO:Bi3+, Eu3+) phosphors, while Bi3+ ion presents a great emission intensity loss with only retaining 46.8% at 383 K. Based on the disparate thermal responses, the fluorescence intensity ratio (FIR) of Eu3+ to Bi3+ demonstrates excellent thermometry properties from 303 to 503 K. The maximum absolute sensitivity (Sa) and relative sensitivity (Sr) reach 0.318 K−1 (@328 K) and 1.62%K−1 (@393 K). In addition, the thermochromic performance of the resultant phosphors could be applied to qualitatively estimate the surrounding temperature. The spectral adjustability and high-sensitive of the developed phosphors highlight their multiplicity of applications in non-contact temperature measurement and white LED.