Porous Uranyl Borophosphates with Unique Three-Dimensional Open-Framework Structures.

Bamboo‐derived hard carbon/carbon nanotube composites as anode material for long‐life sodium‐ion batteries with high charge/discharge capacities

Role of boron-containing ionic liquid in the synthesis of manganese borophosphate with extra-large 16-ring pore openings

New mixed-valence ethylenediamine-vanadium phosphate, [C2H8N2]{(VVO)(VIVOH)[PO(OH)3](PO4)2} with the 3D open framework structure, has been hydrothermally synthesized and characterized by elemental analysis, XRD, SEM, FTIR, UV-Vis DRS, and single-crystal X-ray diffraction. This compound crystallizes in the monoclinic system with the space group C2/c and cell parameters: a = 22.142(4), b = 8.8901(17), c = 16.195(3) A, β = 126.710(2)°, and V = 2555.6(9) A3. The structure exhibits a three-dimensional open framework topology with eight-membered ring channels, which are occupied by unprotonated ethylenediamine molecules through N-H ⋯ O hydrogen-bond interactions.

Structural assembly from phosphate to germanophosphate by applying germanate as a binder has been achieved. Two isotypic porous compounds, K3[M(II)4(HPO4)2][Ge2O(OH)(PO4)4]·xH2O (M(II) = Fe, Cd; x = 2 for Fe and 3 for Cd, denoted as KFeGePO-1 and KCdGePO-1, respectively), contain a known transition-metal phosphate (TMPO) layer, (∞)(2){[M2(HPO4)3]2–}, which is built from chains of trans-edge-sharing MO6 octahedra bridged by MO5 trigonal bipyramids that were further linked and decorated by phosphate tetrahedra. The layers are bound by infinite chains of GeO5(OH) octahedra, resulting in a 3D open-framework structure with 1D 12-ring channels that are occupied by K+ ions and water molecules. The curvature of the TMPO layers and shape of the 12-ring windows can be tuned by the transition metals because of their Jahn–Teller effect.

Hydrothermal synthesis and structural characterization of a novel NLO compound, La(MoO 2)(OH)(IO 3) 4

Oxyfluorinated Microporous Compounds: VIII. Synthesis and Structure Determination of V2PO8F, en (ULM-7V): The First Oxyfluorovanado(V) Phosphate Templated by Ethylenediamine

Two isostructural diarsenates, SrZnAs2O7 (strontium zinc diarsenate), (I), and BaCuAs2O7 [barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. The three-dimensional open-framework crystal structure consists of corner-sharing M2O5 (M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7 group shares its five corners with five different M2O5 square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine-coordinated M1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of the M1O9, M2O5 and As2O7 groups of known isostructural diarsenates, adopting the general formula M1(II)M2(II)As2O7 (M1(II) = Sr, Ba, Pb; M2(II) = Mg, Co, Cu, Zn) and crystallizing in the space group P2₁/n, are presented and discussed.

Four new ethylenediamine-templated iron arsenates and fluoroarsenates have been hydrothermally synthesized from iron metal, hydrofluoric and arsenic acids, and ethylenediamine. Fe(H2AsO4)(HAsO4)2.enH2.H2O (1) is one-dimensional and contains chains, FeIIIFeIIF2(HAsO4)(AsO4).enH2.2H2O (2) is a layered fluoroarsenate, and Fe3(HAsO4)6.enH2.NH3.NH4 (3) and Fe2F2(AsO4)2(H2O).enH2 (4) are an arsenate and a fluoroarsenate, respectively, with three-dimensional open-framework type structures. Compounds 1, 3, and 4 contain Fe(III) only, while 2 is a mixed-valence compound of Fe(III) and Fe(II). The structures were determined from single-crystal X-ray diffraction. Crystal data: (1) P2(1), a = 4.762(1) A, b = 16.086(3) A, c = 8.698(2) A, beta = 90.65(3) degrees, Z = 2; (2) P-1, a = 5.289(1) A, b = 7.573 (1) A, c = 8.888(2) A, alpha = 67.32(3) degrees, beta = 82.77(3) degrees, gamma = 69.76(3) degrees, Z = 1; (3) C2/c, a = 18.384(3) A, b = 8.785(1) A, c = 16.052(2) A, beta = 111.11(1) degrees, Z = 4; (4) Pbca, a = 10.490(2) A, b = 10.090(2) A, c = 20.540(4) A, Z = 8. Strong hydrogen bonding exists between the chains and the layers in 1 and 2, and between the diprotonated ethylenediamine and the inorganic part of the structures of 1, 2, and 4. The ethylenediamine in 3 is not hydrogen bonded, and as a result it is disordered. The compounds are characterized also by thermogravimetric analysis, infrared spectroscopy, elemental analysis, and magnetic measurements.

The electronic, structural, and piezoelectric properties of perovskite BiFe1-xCoxO3 (BFCO) have been investigated using a first-principles calculation with optimized structures. Our calculated results show that the most stable structure changes from rhombohedral to monoclinic to tetragonal as x increases and that piezoelectric constants show maximums at the rhombohedral structure. These results are qualitatively in good agreement with the experimental results. However, even with the randomness of Fe and Co atoms, the piezoelectric constants do not show maximums at the monoclinic structure. This result suggests that the morphotropic phase boundary (MPB) does not appear in BFCO owing to a much larger c/a ratio in monoclinic and tetragonal structures.

The number of reported metallic compounds with polar crystal structures is limited due to the incompatibility of the acentricity and metallicity. Particularly, metallic oxides with polar crystal structures are rare. In this work, we designed a single-layer Aurivillius oxide Bi2ReO6 to explore metallic polar oxides. Single crystals and polycrystalline samples of Bi2ReO6 are synthesized by high-pressure methods. Bi2ReO6 crystallizes in the tetragonal structure with the polar space group P42cm (No. 101). Bi2ReO6 consists of alternative stacking of (Bi2O2)2+ layers and perovskite-like [ReO4]2– layers. Theoretical calculations further support that Bi2ReO6 with the polar space group is more stable and the tilts of ReO6 octahedra stabilize the system and break the inversion symmetry. Our magnetic and electrical data and low-temperature specific heat data indicate that Bi2ReO6 is a Pauli metal. The calculated electronic structures for Bi2ReO6 support the metallic nature, and the density of states at the Fermi level is contributed mainly from Re 5d orbitals hybridized with O 2p orbitals.

Microstructure analysis of Kr+ irradiation and post-irradiation corrosion of modified N36 zirconium alloy

We reported the high working voltage of K-ion battery (KIB) comparable to Li-ion and higher than Na-ion thanks to the standard potential of potassium is lower than those of lithium and sodium in non-aqueous electrolyte [1,2]. In 2015, our group reported graphite negative electrode delivering 250 mAh g-1 or higher with excellent reversibility [1]. Furthermore, a Prussian blue analogue (PBA) of K2Mn[Fe(CN)6] demonstrated highly reversible potassium insertion/extraction and 4 V operation, realizing a 4 V-class K2Mn[Fe(CN)6]/graphite full cell [3]. The previous studies revealed that a three-dimensional open framework structure of PBAs is suitable for insertion/extraction of large K+ ion. Addition to the PBAs, polyanionic compounds are potential positive electrode materials for KIBs due to their open framework structure and inductive effect. In this talk, our recent studies on potassium insertion into various polyanionic compounds, such as heterosite FePO4, KFePO4, KMnPO4, K2FeP2O7, K2MnP2O7, KVPO4F, KVOPO4, monoclinic KFeSO4F, and orthorhombic KFeSO4F (o-KFeSO4F) [4,5], will be presented to give a perspective of potassium insertion material design. Because K+ ion is too large to occupy the octahedral site in heterosite FePO4 prepared from olivine-type LiFePO4, the crystallinity of heterosite FePO4 significantly decreases after potassium insertion. On the other hand, KVPO4F, KVOPO4, and o-KFeSO4F possess the KTiOPO4-type structure providing large channels to diffuse K+ ion and show the reversible potassium insertion/extraction properties and excellent rate performance. These results indicate that the crystal structure plays a key factor for reversible potassium insertion and rate performance. Moreover, the average discharge voltage of KVPO4F and KVOPO4 is as high as 4 V in a K half-cell. That of o-KFeSO4F is 3.6 V, which is notably high redox potential of Fe2+/Fe3+ due to the strong inductive effect of SO4 2- and F- on the Fe2+/3+ couple. The cycling stability of these high-voltage electrode materials is highly improved by using highly concentrated potassium salt solutions [6]. From these results, we will present our future insight into electrochemical potassium insertion chemistry for high voltage battery applications.

For growing high quality epitaxial VO2 thin films, the substrate with suitable lattice parameters is very important if considering the lattice matching. In addition, the thermal conductivity between the substrate and epitaxial film should be also considered. Interestingly, the c-plane of hexagonal 6H-SiC with high thermal conductivity has a similar lattice structure to the VO2 (010), which enables epitaxial growth of high quality VO2 films on 6H-SiC substrates. In the current study, we deposited VO2 thin films directly on 6H-SiC (0001) single-crystal substrates by pulsed laser deposition (PLD) and systematically investigated the crystal structures and surface morphologies of the films as the function of growth temperature and film thickness. With optimized conditions, the obtained epitaxial VO2 film showed pure monoclinic phase structure and excellent phase transition properties. Across the phase transition from monoclinic structure (M1) to tetragonal rutile structure (R), the VO2/6H-SiC (0001) film demonstrated a sharp resistance change up to five orders of magnitude and a narrow hysteresis width of only 3.3 °C.

Organically templated metal sulfate-oxalates: Solvent-free synthesis, crystal structure, and proton conduction

Synthesis and crystal structure of a new open-framework iron phosphate (NH 4) 4Fe 3(OH) 2F 2[H 3(PO 4) 4]: Novel linear trimer of corner-sharing Fe(III) octahedra