Optical and structural properties of Mn-doped magnesium titanates fabricated with excess MgO

Optical and Structural Properties of Mn4+‐Activated (ZnxMg1–x)2TiO4 Red Phosphors

“…The signal from Mn 2+ ions in the cubic (Zn,Mg) 2 TiO 4 phase shows smaller intensity as compared with Mn 2+ in (Zn,Mg)TiO 3 . A similar effect was observed in the magnesium titanates, [ 33 ] where the intensity of Mn 2+ EPR signal in the MgTiO 3 was more than 10 times larger than in the Mg 2 TiO 4 . Moreover, the EPR signals of Mn 2+ in the hexagonal and cubic zinc–magnesium titanate phases overlap and so it is difficult to determine whether Mn 2+ ions are present in the (Zn,Mg) 2 TiO 4 phase of the phosphors obtained at 800 and 900 °C.…”

“…Such situation has been observed for Mn 4+ ‐activated Mg 2 TiO 4 and MgTiO 3 phosphors sintered with excess MgO. [ 31,33 ] It has been shown that PL intensity of the Mn 4+ ‐doped Mg 2 TiO 4 can be increased in 1.1–3 times as about 19 mol% excess MgO is added. [ 31 ] The effect of Zn doping on the PL intensity found in this work is of the same order and possible is of the same reason.…”

“…First, formation of the Mn 2+ centers in the Zn 2 TiO 4 can be less favorable than in the Mg 2 TiO 4 . For example, much smaller concentration of the Mn 2+ in the Mg 2 TiO 4 as compared with the MgTiO 3 [ 33 ] is apparently due to a stronger tendency for manganese to replace Mg 2+ in crystal lattice of the MgTiO 3 . Second, the doping of (Zn,Mg) 2 TiO 4 with Zn from the secondary ZnO phase can hinder substitution of site Mg 2+ ions with Mn and facilitate incorporation of manganese onto Ti 4+ site.…”

“…This situation is similar to that observed in the Mg 2 TiO 4 and MgTiO 3 . [31,33] At the same time, in the phosphors with x ¼ 0.75 and 1.0, formation of the Mn 2þ centers is less possible. This can be caused by several reasons.…”

Site Preference-Driven Mn4+ Stabilization in Double Perovskite Phosphor Regulating Quantum Efficiency from Zero to Champion

“…Furthermore, the EPR test also confirms the evolution of Mn charge states by the cation-pair substitution. As shown in Figure b, all the Mn-doped samples show sextets of lines with the g -factor about 2.00 but with different signal intensities, indicating the existence of Mn 2+ with different concentrations . The high-resolved sextets of lines claim the high Mn 2+ content in nonluminous Ca 2 MgWO 6 :5.0% Mn and CaNa 0.5 La 0.5 MgWO 6 :5.0% Mn (CO).…”