Eita Tochigi

A new sealed lithium-peroxide battery with a co-doped Li2O cathode in a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte.

We propose a new sealed battery operating on a redox reaction between an oxide (O2−) and a peroxide (O22−) with its theoretical specific energy of 2570 Wh kg−1 (897 mAh g−1, 2.87 V) and demonstrate that a Co-doped Li2O cathode exhibits a reversible capacity over 190 mAh g−1, a high rate capability, and a good cyclability with a superconcentrated lithium bis(fluorosulfonyl)amide electrolyte in acetonitrile. The reversible capacity is largely dominated by the O2−/O22− redox reaction between oxide and peroxide with some contribution of the Co2+/Co3+ redox reaction.

Assessment of Strain-Generated Oxygen Vacancies Using SrTiO3 Bicrystals

Atomic-scale defects strongly influence the electrical and optical properties of materials, and their impact can be more pronounced in localized dimensions. Here, we directly demonstrate that strain triggers the formation of oxygen vacancies in complex oxides by examining the tilt boundary of SrTiO3 bicrystals. Through transmission electron microscopy and electron energy loss spectroscopy, we identify strains along the tilt boundary and oxygen vacancies in the strain-imposed regions between dislocation cores. First-principles calculations support that strains, irrespective of their type or sign, lower the formation energy of oxygen vacancies, thereby enhancing vacancy formation. Finally, current-voltage measurements confirm that such oxygen vacancies at the strained boundary result in a decrease of the nonlinearity of the I-V curve as well as the resistivity. Our results strongly indicate that oxygen vacancies are preferentially formed and are segregated at the regions where strains accumulate, such as heterogeneous interfaces and grain boundaries.

Atomic structure and strain field of threading dislocations in CeO2 thin films on yttria-stabilized ZrO2

Threading dislocations in CeO2 thin films grown on yttria-stabilized ZrO2 substrates were investigated by transmission electron microscopy (TEM), high-resolution TEM, and scanning TEM. It is revealed that there are two kinds of threading dislocations with the Burgers vector of b=1/2⟨110⟩: one is pure edge-type and the other is mixed-type. Comparing the strain field of the mixed-type dislocations with that of the Peierls–Nabarro and the Foreman dislocation models, we find that the Foreman model better describes it in CeO2.

Dynamic observations of dislocation behavior in SrTiO3 by in situ nanoindentation in a transmission electron microscope

The plastic deformation process of a SrTiO3 single crystal has been dynamically and microscopically observed by in situ nanoindentation in a transmission electron microscope. The plastic deformation of SrTiO3 was found to proceed by dislocation slips even at room temperatures under the present experimental condition, and the dynamic behavior of dislocations such as nucleation, propagation, and annihilation have been clearly captured. The detailed dislocation analyses revealed that the activated slip system is 〈110〉{11¯0} type, which is consistent with the results of macroscopic deformation experiments reported so far. The mechanisms of dislocation behavior are discussed based on the experimentally obtained results.

A New Rechargeable Sodium Battery Utilizing Reversible Topotactic Oxygen Extraction/Insertion of CaFeOz (2.5 ≤ z ≤ 3) in an Organic Electrolyte

At present, significant research efforts are being devoted both to identifying means of upgrading existing batteries, including lithium ion types, and also to developing alternate technologies, such as sodium ion, metal-air, and lithium-sulfur batteries. In addition, new battery systems incorporating novel electrode reactions are being identified. One such system utilizes the reaction of electrolyte ions with oxygen atoms reversibly extracted and reinserted topotactically from cathode materials. Batteries based on this system allow the use of various anode materials, such as lithium and sodium, without the requirement to develop new cathode intercalation materials. In the present study, this concept is employed and a new battery based on a CaFeO3 cathode with a sodium anode is demonstrated.

Dislocation structures and strain fields in [111] low-angle tilt grain boundaries in zirconia bicrystals

Structures of <111> low-angle tilt grain boundaries in yttria-stabilized cubic zirconia bicrystals were characterized by conventional transmission electron microscopy, high-resolution transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy. It is found that the 0.4 and 4.0 degrees tilt grain boundaries are composed of periodic arrays of edge dislocations with Burgers vectors . The experimentally estimated strain field of each dislocation in the 0.4 degrees tilt boundary was in good agreement with the theoretically predicted strain field from the Peierls-Nabarro model. On the other hand, the estimated strain field of each dislocation in the 4.0 degrees tilt boundary was clearly different from that in the 0.4 degrees tilt boundary, which suggests that the strain fields of neighbouring dislocations interact when the separation distance between dislocations is shorter than a critical value.

Direct Observation of Impurity Segregation at Dislocation Cores in an Ionic Crystal

Dislocations, one-dimensional lattice defects, are known to strongly interact with impurity atoms in a crystal. This interaction is generally explained on the basis of the long-range strain field of the dislocation. In ionic crystals, the impurity-dislocation interactions must be influenced by the electrostatic effect in addition to the strain effect. However, such interactions have not been verified yet. Here, we show a direct evidence of the electrostatic impurity-dislocation interaction in α-Al2O3 by visualizing the dopant atom distributions at dislocation cores using atomic-resolution scanning transmission electron microscopy (STEM). It was found that the dopant segregation behaviors strongly depend on the kind of elements, and their valence states are considered to be a critical factor. The observed segregation behaviors cannot be explained by the elastic interactions only, but can be successfully understood if the electrostatic interactions are taken into account. The present findings will lead to the precise and quantitative understanding of impurity induced dislocation properties in many materials and devices.

First principles pseudopotential calculation of electron energy loss near edge structures of lattice imperfections.

Theoretical calculations of electron energy loss near edge structures (ELNES) of lattice imperfections, particularly a Ni(111)/ZrO₂(111) heterointerface and an Al₂O₃ stacking fault on the {1100} plane, are performed using a first principles pseudopotential method. The present calculation can qualitatively reproduce spectral features as well as chemical shifts in experiment by employing a special pseudopotential designed for the excited atom with a core-hole. From the calculation, spectral changes observed in O-K ELNES from a Ni/ZrO₂ interface can be attributable to interfacial oxygen-Ni interactions. In the O-K ELNES of Al₂O₃ stacking faults, theoretical calculation suggests that the spectral feature reflects coordination environment and chemical bonding. Powerful combinations of ELNES with a pseudopotential method used to investigate the atomic and electronic structures of lattice imperfections are demonstrated.

Dislocation structures and electrical conduction properties of low angle tilt grain boundaries in LiNbO3

Dislocations in crystalline materials constitute unique, atomic-scale, one-dimensional structure and have a potential to induce peculiar physical properties that are not found in the bulk. In this study, we fabricated LiNbO3 bicrystals with low angle tilt grain boundaries and investigated the relationship between the atomic structure of the boundary dislocations and their electrical conduction properties. Observations by using transmission electron microscopy revealed that dislocation structures at the (0001) low angle tilt grain boundaries depend on the tilt angle of the boundaries. Specifically, the characteristic dislocation structures with a large Burgers vector were formed in the boundary with the tilt angle of 2°. It is noteworthy that only the grain boundary of 2° exhibits distinct electrical conductivity after reduction treatment, although LiNbO3 is originally insulating. This unique electrical conductivity is suggested to be due to the characteristic dislocation structures with a large Burgers ve...

Dissociation reaction of the 1/3\( \left\langle {\bar{1}101} \right\rangle \) edge dislocation in α-Al2O3

It has been reported that dislocations with 1/31¯101\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}