Calculations of the Racah parameter B for Mn4+ and Mn2+ ions doped in CaAl2O4

The luminescent materials CaAl2O4.:Mn4+ and CaAl2O4:Mn2+ were synthesized by solid state reaction method. The red luminescence of CaAl2O4:Mn4+ shows an asymmetric broad band peaking at 650 nm, respectively to the characteristic luminescence of Mn4+ ions. The emission spectrum of CaAl2O4:Mn2+ shows a broad green emission band centering at 545 nm respectively to the characteristic luminescence of Mn2+ ions. By doping different outer shells in the same host lattice, the ionic interaction between ions and the host lattice are also different. The differences are reflected in Racah parameter B, and the nephelauxetic effect /6. The /6 coefficient of CaAl2O4:Mn4+ is small, indicating that its orbitals expand greatly, the interaction force between Mn4+ and the host lattice is greater than that of Mn2+.