Luminescence of Mn4 + in the Distorted Perovskite Gd2MgTiO6

The deep red luminescence of Mn 4+ in the distorted perovskite Gd 2 MgTiO 6 is reported and discussed. The excitation spectrum of Mn 4+ luminescence is dominated by the O 2- to Mn 4+ charge-transfer transition at ∼31,700 cm -1 . The luminescence is due to the 2 E → 4 A 2 transition with the zero-phonon line at ∼14,685 cm -1 and the associated side bands at longer wavelengths. Evidence is presented for the occurrence of multiple Mn 4+ sites in the host lattice. This is attributed to the deviation from a perfect 1 :1 order between the B-site ions (Mg 2+ /Ti 4+ ) of the perovskite lattice. The unactivated host lattice also exhibits Mn 4+ luminescence due to the presence of this ion as an impurity in one of the starting materials (TiO 2 ). Evidence is presented for Gd 3+ to Mn 4+ energy transfer in this host lattice.