Improved optical thermometric sensitivity of Eu3+‐doped calcium niobate phosphor via nonstoichiometric control

Abstract Eu 3+ ‐doped calcium niobate CaNb x O 6 phosphors were successfully prepared by a solid‐state reaction, and the crystal structure, morphology, energy transfer process, and temperature‐dependent behaviors were systematically investigated. The CaNb x O 6 host matrix presents the self‐activated characteristic emission at 470 nm due to the charge transfer transition of Nb 5+ –O 2+ , and the corresponding photoluminescence intensity reaches the maximum intensity when the nonstoichiometric ratio of Ca 2+ /Nb 5+ ions is 1:1.9. Moreover, the energy transfer process from the host (470 nm) to Eu 3+ (612 nm) ions in the CaNb 1.9 O 6 :Eu 3+ phosphor is demonstrated, and the corresponding energy transfer efficiency is significantly enhanced compared with that of stoichiometric sample. Furthermore, it is observed that nonstoichiometric ratio of Nb 5+ ions deteriorates the thermal quenching of the matrix while guaranteeing the thermal stability of the activators, resulting in the relative sensitivity ( S r ) of CaNb 1.9 O 6 :Eu 3+ being greatly improved from 2.235% to 3.673% K −1 . Herein, these results provide an effective strategy for manipulating the sensitivity of optical thermometers of phosphors based on the induced modulation of the temperature‐response performance via nonstoichiometric control.