Review-Temperature Dependence of Luminescence Intensity and Decay Time in Cr3+-Activated Oxide and Fluoride Phosphors

Studying temperature dependence of light emission intensities in luminescent materials is not only of scientific interest but also technological importance. It is well known that Mn4+-activated "fluoride" phosphors sometimes show an anomalous thermal quenching (TQ) behavior. This behavior is an increase in the integrated photoluminescence (PL) intensity I (PL) with increasing temperature T, called negative TQ, and is understood to be due to the electric dipole (parity) forbidden transitions of (2) E ( g ) -> (4) A (2g ) gained by coupling with the odd-parity lattice vibrations, nu (3), nu (4), and nu (6). The present article discusses the temperature dependence of the integrated PL intensity for the Cr3+-activated "oxide" and "fluoride" phosphors with an emphasis on negative TQ phenomenon. The effects of the (4) A (2g ) -> (4) T (2g ) excitation transitions in conjunction with those of the normal (positive) TQ are considered for developing a new analysis model of I (PL)(T) data. Our new analysis model shows a good agreement with the experimental I (PL)(T) data. Discussion is also given on the temperature dependence of luminescence decay time tau(T), demonstrating a strong correlation between I (PL)(T) and tau(T) except for negative TQ occurring only in I (PL)(T).