In-plane chemical pressure essential for superconductivity in BiCh2-based (Ch: S, Se) layered structure

BiCh2-based compounds (Ch: S, Se) are a new series of layered superconductors, and the mechanisms for the emergence of superconductivity in these materials have not yet been elucidated. In this study, we investigate the relationship between crystal structure and superconducting properties of the BiCh2-based superconductor family, specifically, optimally doped Ce1-xNdxO0.5F0.5BiS2 and LaO0.5F0.5Bi(S1-ySey)2. We use powder synchrotron X-ray diffraction to determine the crystal structures. We show that the structure parameter essential for the emergence of bulk superconductivity in both systems is the in-plane chemical pressure, rather than Bi-Ch bond lengths or in-plane Ch-Bi-Ch bond angle. Furthermore, we show that the superconducting transition temperature for all REO0.5F0.5BiCh2 superconductors can be determined from the in-plane chemical pressure.

Liquid-phase step-by-step growth of an iron cyanide coordination framework on LiCoO₂ particle surfaces

Surface modification of inorganic objects with metal-organic frameworks (MOFs) - organic-inorganic hybrid framework materials with infinite networks - opens wide windows for potential applications. In order to derive a target property, the key is the ability to fine tune the degree of modification. Solution-based step-by-step growth techniques provide excellent control of layer thickness which can be varied with the number of deposition cycles. Such techniques with MOFs have been mainly applied to flat substrates, but not to particle surfaces before. Here, we present the facile surface modification of inorganic particles with a framework compound under operationally simple ambient conditions. A solution-based sequential technique involving the alternate immersion of LiCoO2 (LCO) - a positive electrode material for a lithium ion battery - into FeCl2·4H2O and K3[Fe(CN)6] solutions results in the formation of Prussian blue (PB) nanolayers on the surface of the LCO particles (PBNL@LCO). The PB growth is finely controlled by the number of immersion cycles. An electrochemical cell with PBNL@LCO as a positive electrode material exhibits a discharge capacity close to the specific capacity of LCO. The results open a new direction for creating suitable interfacial conditions between electrode materials and electrolytes in secondary battery materials.

Direct ethanol fuel cell using hydrotalcite clay as a hydroxide ion conductive electrolyte

An alkaline-type direct ethanol fuel cell (DEFC) using a natural clay electrolyte with non-platinum catalysts is proposed. So-called hydrotalcite clay, Mg–Al layered double hydroxide intercalated with CO₃²⁻, is shown to be a hydroxide ion conductor. An alkaline-type DEFC using this natural clay as the electrolyte and aqueous solution of ethanol and potassium hydroxide as a source of fuel exhibits excellent electrochemical performance from room temperature to 80 °C.

Structure of polyphenylsilsesquioxane particles prepared by two-step acid-base catalyzed sol-gel process and formation of hollow particles

Spherical polyphenylsilsesquioxane (PhSiO(3/2)) particles, one of the inorganic-organic hybrid materials, were synthesized by a two-step acid-base catalyzed sol-gel process, and hollow particles were successfully prepared by washing the as-prepared particles with organic solvents. It was found that the inside and outside parts of the as-prepared particles were composed of PhSi03/2 species with relatively low and high molecular weight, respectively, i.e., the PhSiO(3/2) particles had a kind of "core-shell" structure. Because the core portion in the as-prepared particles was soluble in ethanol and tetrahydrofuran, hollow particles were obtained through washing the as-prepared PhSiO(3/2) particles with ethanol or tetrahydrofuran. Furthermore, the molecular weight of the as-prepared particles was varied by the concentration of phenyltriethoxysilane used as a starting alkoxide. As a result of the variation of the molecular weight, the hollow PhSiO(3/2) particles with different stabilities against organic solvents were formed.

Inorganic−Organic Hybrid Membranes with Anhydrous Proton Conduction Prepared from 3-Aminopropyltriethoxysilane and Sulfuric Acid by the Sol−Gel Method

Inorganic-organic hybrid membranes with anhydrous proton conduction were prepared from 3-aminopropyltriethoxysilane and H2SO4 by the sol-gel method. The membrane has a unique structure: a hexagonal phase formed by the stacking of rodlike polysiloxanes with ion complexes of ammonium groups and HSO4- extruded outside. The membranes showed high conductivity of 2 x 10-3 S cm-1 at 200 degrees C under dry atmosphere. In the membrane, protons probably migrate through the outside of the rodlike polysiloxanes along hydrogen-bond chains formed among HSO4- anions.