Inner mechanism of Pr3+ luminescence thermometers based on the intervalence charge transfer state

Abstract

Owing to their ultra-high temperature sensitivity, luminescence thermometers based on the intervalence charge transfer state of Pr3+ have drawn more and more attention. But the inner mechanism of Pr3+ luminescence thermometers, especially which parameters could affect the value of relative sensitivity, is still not fully revealed. In this paper, the luminescence thermometer properties of Ba1-xCaxTiO3:1%Pr3+ (x=0-0.7) with variation temperature have been systematically studied. The process of electrons in the 3P0 state passed through the intervalence charge-transfer state to the 1D2 state has been found to be sensitive to temperature variation. Through the intervalence charge transfer state engineering, we successfully realized the effective regulation of the intervalence charge transfer state energy position by replacing Ba2+ with Ca2+ and find that the effective energy gap between the 3P0 state and the intervalence charge transfer state is the key parameter that affects the relative sensitivity of luminescence thermometers. Moreover, the maximum relative sensitivity of Pr3+-doped BaTiO3, evaluated to be 2.26% K−1 at 413K under 450 nm excitation, is the one of the best performances among the Pr3+-based luminescence thermometers. This research could lead to the novel development of an efficient and high-performance optical thermometer.