Review—Temperature Dependence of Luminescence Intensity and Decay Time in Mn4+-Activated Oxide Phosphors

Abstract

Thermal stability of the phosphor materials is of crucial importance and scientific interest. Mn4+-activated “fluoride” phosphors are known to 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, ν 3, ν 4, and ν 6. The same behavior can also occur in Mn4+-activated “oxide” phosphors. The present article discusses the temperature dependence of the integrated PL intensity I PL(T) for the Mn4+-activated oxide phosphors focusing on the negative TQ phenomenon. The effects of the 4 A 2g → 4 T 2g excitation transitions in conjunction with those of the normal (i.e., positive) TQ are considered for developing new analysis model of I PL vs T data. Our proposed analysis model shows a good agreement with the experimental data. Discussion is also given on the temperature dependence of decay time τ(T) and quantum efficiency η(T), in comparison with I PL(T), demonstrating a strong correlation among such important phosphor properties except for an occurrence of negative TQ only in I PL(T).