Mn4+vs Mn2+-A comparative study as efficient activator ions in phosphor materials: A review

The properties of Mn4+ (3d3) and Mn2+ (3d5) ions as the transition-metal efficient activators for phosphor materials are discussed in detail from spectroscopic points of view. The spectroscopic properties of 3dn activator ions are examined by analyzing photoluminescence (PL) and PL excitation (PLE) spectra based on the Franck-Condon principle with the configurational-coordinate model. The PL and PLE spectral features are analyzed while keeping in mind their different 3dn electron configurations that are the lowest excited-state level of 2E in the former ion (Mn4+) being almost parallel to that of the ground level 4A2, whereas that of 4T1 in the latter ion (Mn2+) being strongly dependent on the crystal-field splitting parameter Dq; those are easily under-stood from their Tanabe-Sugano energy-level diagram schemes. Study has also been focused on the temperature -dependent PL intensities of the Mn ion-activated phosphors by analyzing the experimental data with our pro-posed theoretical model.