Review—Temperature Dependence of Transition-Metal and Rare-Earth Ion Luminescence (Mn <sup>4+</sup> , Cr <sup>3+</sup> , Mn <sup>2+</sup> , Eu <sup>2+</sup> , Eu <sup>3+</sup> , Tb <sup>3+</sup> , etc.) I: Fundamental Principles
Sadao Adachi
Abstract
Thermal stability of the phosphor materials is of crucial importance and scientific interest. Various Mn 4+ -activated fluoride, oxide, and oxyfluoride phosphors show an anomalous thermal quenching (TQ) behavior, i.e., no decrease or an increase in the integrated photoluminescence intensity I PL with increasing temperature T , known as zero or negative TQ. The purpose of this article is to discuss such anomalous behaviors of thermal stability of the phosphors doped with various kinds of activator ions from an aspect of solid-state physics. Mn 4+ (3 d 3 )-activated fluoride phosphor is a good example to understand the fundamentals of such foreign ion-activated phosphors. The luminescence transitions of 2 E g → 4 A 2 g in 3 d 3 -configuration ions are both parity and spin-forbidden transitions and, therefore, one can expect no strong light emission. Herein, Mn 4+ luminescence is discussed by considering parity integral. This approach helps better understanding of the peculiar luminescence properties observed in the various 3 d 3 ion-activated phosphors. The luminescence properties of the HK 3 SnF 8 :Mn 4+ and Cs 2 WO 2 F 4 :Mn 4+ phosphors are examined in detail as a verification of our proposed model. This model will be successfully applied to other kinds of activator ions, such as Cr 3+ , Mn 2+ , Eu 2+ , Eu 3+ , and Tb 3+ in a separate article (II).