Anti-thermal-quenching red-emitting GdNbO4:Pr3+ phosphor based on metal-to-metal charge transfer for optical thermometry application

The thermal quenching of phosphors seems to be inevitable, which severely limits their applications related to high temperature. Therefore, the development of thermally stable phosphors and the exploration of anti-thermal quenching mechanism is still a pivotal need. Herein, an internal self-regulation anti-thermal quenching strategy has been proposed to develop Pr3+-activated GdNbO4 red phosphor, whose loss of red emission intensity can be compensated at the expense of blue emission during the heating process. The integrated photoluminescence intensity of GdNbO4:x%Pr3+ (x = 0.1-2.5) is maintained or even continuously enhanced from 300 K to 620 K based on the metal-to-metal charge transfer between Pr3+ ions and Nb5+ ions. For the GdNbO4:0.1%Pr3+ sample, the integrated intensity of its red emission remarkably reaches 290% at 540 K compared to that at 300 K. As expected, the opposite temperature response of Pr3+ 3P0 -> H-3(4) and D-1(2) -> H-3(4) indicates that GdNbO4:0.1%Pr3+ has advantage in optical thermometry based on MMCT (S-r = 0.7% K-1 at 430 K and S-a = 18% K-1 at 620 K). Our work could open a new gateway to design phosphors with anti-thermal quenching performance for high-temperature applications and develop high-performance optical temperature sensing in Pr3+-activated oxide phosphors.