Optical properties of Co3+ doped in α-Al2O3 with Considering Lattice Relaxation Effect

Abstract

Search of new luminescence materials to improve the current white-ight emitting diode (LED) is still ongoing. Several investigations such as the ion dependence, the host crystal dependence has been done previously. Since we want to get a complete picture of ion-host combination dependence, we investigated α-Al2O3: TM3+. In this work we estimated the optical properties of α-Al2O3 doped with Co3+. We constructed model clusters consisting of 7 atoms. The lattice relaxation effects due to the Co3+ substitution were calculated using Shannon’s crystal radii method and geometry optimizations in the Cambridge Serial Total Energy Package (CASTEP) method. The one-electron Discrete Variational-Xα (DV-Xα) method was used to estimate the molecular orbital energies, while the many-electron Discrete Variational Multielectron (DVME) method was used to estimate the d-d absorption spectra. Since Co3+ belongs to 3d 6 configuration, there are two possible spin states i.e., high-spin (HS) and low-spin (LS) states.