Perovskite-type oxides with a chemical formula of ABO3 exhibit various functional properties. Among them, lithium ion-conducting oxides with A-site deficient perovskite-type structure such as La2/3－xLi3xTiO3 show fast lithium ion conductivity of 10－5 to 10－3 S/cm at room temperature. The high conductivity is attributable to the percolation-controlled diffusion of lithium ions in the vicinity of A-site via vacancy. In this report, recent research on perovskite-type lithium ion-conducting oxides are reviewed in terms of crystal structure including microstructure, and chemical bond. The relationship among structure, chemical bond, especially second-order Jahn-Teller effect attributable to the covalent bond between B ion with d0 electronic configuration and O ion, and lithium-ion diffusion are discussed.
For the structure determination of endohedral metallofullerenes (EMFs), X-ray crystallographic study is very powerful because it provides detailed information of the positions of encapsulated species as well as the cage structures. We have reported a number of X-ray crystal structures of EMFs and their derivatives, which are in good agreement with those suggested by theoretical calculations as well as NMR analyses. Herein we show the importance of interplay between experiments and theoretical calculations for the structure determination of EMFs by taking up La@C82, Gd@C82, and Sc2@C66 as the representative examples.
Orbital angular momentum (OAM) is a physical quantity representing a magnitude of orbital motion of an object. Recently, it has been recognized that a propagating wave in free space, such as photon, electron and neutron can similarly carry OAM. This OAM degree of freedom of electron beam has been attracting a great attention not only for physical interest but also for its potential applications. This article gives you an idea of what propagating waves carrying OAM are and reviews recent progress in researches of electron vortex beams.
We synthesized NiO nanoparticles with particle sizes ranging from about 2 to 22 nm in the pores of mesoporous silica and investigated their crystal structure and magnetic properties. The mesoporous silica was used as a template to equalize the particle size during the fabrication of NiO nanoparticles. The NiO nanoparticles in mesoporous silica exhibited the interesting size dependences of crystal structure and magnetic properties. The experimental results indicated that the magnetic properties of the NiO nanoparticles were strongly correlated with both the lattice strain and rhombohedral distortion of rock-salt structure. The magnetic properties for particle sizes above 8 nm exhibited significant decreases in both magnetic anisotropy energy and coercive field, which was attributed to the particle shape distortion.
Many molluscs use hemocyanin freely dissolved in hemolymph for oxygen transportation. Hemocyanin is one of the largest known proteins, of which total molecular mass is larger than 3.3 MDa. Although molluscan hemocyanin is used as immunotherapeutic agents, their detailed structures had not yet been revealed. As its enormous size and the propensity of dissociation hampered crystallization, structural studies have relied mainly on electron microscopy. To understand the oxygen transportation mechanism in detail and promote the biomedical application, high-resolution structure has been desired for a long time. In this study, we successfully determined the X-ray crystal structure of the intact 3.8-MDa hemocyanin from Japanese flying squid at 3.0 Å resolution, which revealed the detailed molecular architecture of the supermolecule.
Despite extensive studies on crystal structure of thin film BiFeO3 (BFO) thin film, it remains debated primarily due to its structural complexity as well as stress effect from underlying substrates. We have examined comprehensive crystal structure analysis for BFO thin layer (30 nm) grown on SrTiO3 (STO) substrate using cross-sectional transmission electron microscopy technique along three different zone axes. Nano-beam electron diffraction (NBED) patterns combined with structure factor (SF) calculations and high-resolution transmission electron microscopy images unambiguously reveal that BFO thin layer grows with rhombohedral structure that is identical to its bulk form. No evidence of monoclinic and/or tetragonal distortion is found. The rhombohedral BFO thin layer is found to grow onto STO by maintaining an epitaxial relationship in a manner that can minimize lattice mismatch at BFO/STO interface. Our current work clearly demonstrates that multiple-zone axes NBED combined with SF calculation is highly effective for precise crystal structure analysis of thin film BFO.