Review-Tanabe-Sugano Energy-Level Diagram and Racah Parameters in Mn4+-Activated Red and Deep Red-Emitting Phosphors

The electronic energy states in the Mn4+-activated phosphors are examined based on the Tanabe-Sugano energy-level diagram. Investigation is focused on the determination of the Racah and crystal-field parameters. The previous review [ECS J. Solid State Sci. Technol., 9, 016001 (2020)] suggested that some excited energy states E-2(g) and T-4(2g) of Mn4+ ion can be relatively accurately determined from photoluminescence (PL) and PL excitation spectra with performing the Franck-Condon principle analysis based on the configurational-coordinate model. However, it is very difficult to accurately determine the higher-lying T-4(1g), a energy from any optical spectrum. This higher-lying energy state needs in the calculation of the Racah parameters. Therefore, a set of expressions is proposed for an accurate determination of the Racah and also crystal-field-related parameters only by introducing E-2(g) and T-4(2g) values. Results are in good agreement with the Tanabe-Sugano energy-level diagram for the Mn4+- activated phosphors of various host materials like fluorides, oxides, and oxyfluorides. (C) 2019 The Electrochemical Society.