Red and Deep Red Emissions from Cubic K2SiF6:Mn4+ and Hexagonal K2MnF6 Synthesized in HF/KMnO4/KHF2/Si Solutions

Cubic K2SiF6:Mn4+ and hexagonal (h-) K2MnF6 red phosphors are synthesized in HF/KMnO4/KHF2/Si solutions under KMnO4-rich and KHF2-rich conditions, respectively. K2SiF6: Mn4+ exhibits efficient red photoluminescence (PL) emission at similar to 630 nm. h-K2MnF6 also exhibits red emission at similar to 630 nm and deep red emission at similar to 680 nm; however, the deep red emission undergoes considerable thermal quenching above 100 K. These two emission bands observed in h-K2MnF6 have the same PL excitation bands as those in K2SiF6: Mn4+. The red emissions can be assigned to the E-2(g) -> (4)A(2g) transition of the 3d(3) electrons in the MnF62- octahedra of h-K2MnF6 and K2SiF6. The deep red emission in h-K2MnF6 is considered to arise from a strongly distorted Mn4+ center in its hexagonal lattice. PL properties, such as the temperature dependence of the PL intensity and luminescence lifetime, of h-K2MnF6 are presented in details in comparison with those of K2SiF6:Mn4+. The addition of KHF2 is also found to be not so efficient to control the Mn doping level in K2SiF6: Mn4+. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.005204jes] All rights reserved.