The purpose of this review article is to present and clarify the various phosphor properties of Mn2+ activator ion in the intra-3d
5-shell electronic configuration. Even though the concepts of intra-3d
5-shell electronic configuration in Mn2+ ion are well understood at this time, some important properties of this ion in the various host materials have been hampered by a lack of definite knowledge of such phosphor systems. The Mn2+-activated phosphor properties examined in the present article can be classified into seven groups: (1) spectral feature of Mn2+-ion photoluminescence (PL) and PL excitation (PLE) transitions, (2) temperature dependence of PL intensity, (3) temperature dependence of PL decay lifetime, (4) Mn2+ concentration effects on PL properties, (5) excitonic transition-related Mn2+ luminescence, (6) crystalline morphology effects: bulk sample vs microcrystalline sample, and (7) crystalline morphology effects: quantum confinement-induced phenomena. Key expressions for theoretically analyzing PL and PLE spectral features, together with PL intensity variation with temperature, for the Mn2+ emission were discussed in detail. A detailed discussion is also given of the acceptability of such phosphor properties and behaviors from an applicational point of view.