Investigations On Electronic Structure Of The New ABO₃ Perovskite Oxide

In this work,the microstructure and electronic properties of ABO₃ perovskite oxides were investigated by using transmission electron microscopy and first-principles calculations.The results of transmission electron microscopy and electron energy loss spectroscopy were significant for understanding the electronic structure of perovskite oxides.This research will provide a theoretical basis.Follows were the main research contents:（1）The microstructure of the perovskite-type oxide Li Os O₃ was studied using transmission electron microscopy.The results showed that the structure of the Li Os O₃ was a perovskite structure,the sample was a single crystal compound.It can be seen from the high-resolution image that the measured inter-planar spacings were about 0.369 nm and 0.329nm,the lattice spacing corresponds to（-110）and（020）planes of Li Os O₃ crystal.The Fourier transform of the high-resolution image were in agreement with the diffraction spots.The electronic structure of the perovskite oxide Li Os O₃ was calculated by first-principles calculation.The density of states near the Fermi level was full,mainly contributed to the transition hybridization between O_S-5d orbital and the O-2p orbital,showing metallic properties.（2）In low-loss of the electron energy loss spectrum（EELS）,the main peak at 25.98 e V（A₅）was the plasma peak,which can be attributed to the collective oscillation of valence electrons.Other peaks were attributed to single electron excitation from the valence band（VB）to conduct band（CB）.From the density of states and the electron energy loss spectrum,the ferroelectricity in Li Os O₃ was mainly caused by the transition hybridization between the Os-5d orbital electrons and the O-2p orbital electrons.The ELNES of O-K edge was compared with the experimental spectra taken by the transmission electron microscope.In order to studied the influence of the electronic structure of Li Os O₃,the core-hole effect,spin-orbit coupling（SOC）effect,and electronic correlation effect were studied respectively.（3）The electronic structure of Al ions doped perovskite oxide Sr Ti O₃ was studied by first-principles calculation.According to the band structure,the band gap of pure Sr Ti O₃ was1.838 e V,which was showed semiconductor properties.Subsequently,Al ions were doped in the Sr₈Ti₈O₂₄ suppercell with 40 atoms at the Sr site and Ti site respectively.It was found that Al-doped Sr Ti O₃ at the Sr site was more conducive to adjust of the band gap.And the concentration of Al ion have a great influence of the band gap.（4）In order to explore the influence of band gap and effect on the photocatalytic performance,a period elements of Al,the same main group elements of Al and rare earth elements doped Sr Ti O₃ were investigated by using first-principles calculations.From the band structure,it was found that Al,P and S ions were more conducive to the adjustment of the band gap in a period elements of Al,and the results of Al-doped of Sr Ti O₃ and In-doped Sr Ti O₃ were beneficial to the adjustment of band gap,which were consistent with the results of the energy band spectrum.In addition,the results of doping of rare earth elements had a non-negligible effect on the adjustment of the band gap.The results provided a theoretical basis for subsequent research.