Crystal structure of bismuth gallium aluminium oxide, Bi-2(GaxAl1-x)(4)O-9, x=0.4, 0.6, 0.8

Al-2 4Bi2Ga1 O-6(9), orthorhombic, pbam (no 55), a = 7 79697(7) angstrom, b = 8.16575(7) angstrom, c = 5 75442(5) angstrom, V = 366.4 angstrom(3), Z = 2, Rw(P) = 0.067, R(P) = 0 048, R(l) = 0 022, T = 293 K. Al16Bi2Ga24O9, orthorhombic, Pbam (no 55), a = 7.83752(8) angstrom, b = 8 20096(8) angstrom, c = 5 79475(6) angstrom, V = 372 5 angstrom(3), Z = 2, Rw(P) = 0 081, R(P) = 0 057 R(l) = 0.031 T = 293 K. Al08Bi2Ga32O9, orthorhombic, Pbam (no 55), a = 7 88345(6) angstrom, b = 8 24579(6) angstrom, c = 5.84335(4) angstrom, V = 379 9 angstrom(3), Z = 2, Rw(P) = 0 075, R(P) = 0 054, R(l) = 0 028, T = 293 K

Investigations of the Anisotropic Optical Reflectivity of Binary and Ternary Nb-W Oxides Possessing Block-Type Crystal Structure

We have studied the anisotropic optical properties of binary NbO2.5-δ (0 8) in the infinite block direction only

Itinerant-electron Ferromagnetism in W(Nb)O3-d

The crystal structure and the magnetic properties of the W1-xNbxO3-d, (x<0.03) system have been investigated. In contrast to the orthorhombic diamagnetic WO3, the material with x=0.01 is paramagnetic down to 5 K. Introducing of 2.5 at. % of Nb into WO3 leads to a tetragonal structure and to a weak itinerant ferromagnetic ordering below TC= 225 K. The saturation magnetic moment at 5 K is 1.07*10-3 mB, whereas the paramagnetic effective moment is 0.06 mB per mole. This high ratio indicates itinerant ferromagnetism in W0.975Nb0.025O3-d.Comment: accepted to Physica

Synthesis and Characterization of Vanadium Substituted Potassium Tungsten Bronzes, K x V y W 1-y O 3

A series of vanadium substituted potassium hexagonal tungsten bronzes KxVyW1-yO3 (K-HTB) were prepared by conventional solid state method at 800 °C with compositions of x = 0.30 and 0.00 ? y ? 0.15. A mixture of K-HTB and non bronze phases with y ? 0.20 was observed. The proportion of this non bronze phase increases with increasing vanadium content. The non bronze phases in the mixture could not be indexed yet. In contrast, a very small amount of vanadium can be substituted in potassium tetragonal tungsten bronzes (K-TTB) at 800 °C with x = 0.50 and 0.00 ? y ? 0.02, however at 700 °C vanadium substituted K-TTB can be prepared with 0.00 ? y ? 0.05. Further substitution of vanadium in K-TTB decomposes to K-HTB and non-bronze phases

The effect of gel-type contributions in lime-sand bricks, alkali-activated slags and CEMI/CEMIII pastes: Implications for next generation concretes

Lime-sand bricks of different ages were investigated using IR-spectroscopy, thermogravimetry, and X-ray diffraction/scattering. After subtraction of the dominant quartz contribution (80%), the IR spectra show the absorption peaks of the hydrothermally formed binder phases. The spectra also show the alteration of the binder during ageing under atmospheric conditions by the influence of CO2 forming carbonate and a condensed SiO2-gel (secondary gel). The alteration could also be proven in X-ray pattern, obtaining a separation between crystalline CSH and amorphous contributions in the freshly produced lime-sand brick, too. Here, the formation of CSHamorph could be understood as a precursor state (primary gel) to the crystallization of CSH phases. X-ray patterns of aged bodies of alkali-silicate solution activated slags (AAS), CEM-I/CEM-III pastes, and CEM-I concrete indicate that in all cases a similar amorphous CSH-type phase (CSHamorph) was formed, which is responsible for the hardening properties as the glue. The main X-ray peak of CSHamorph obtained using CuKα-radiation with a usual diffractometer is observed between 24◦ and 35◦ 2 Theta with maximum at about 29◦ 2 Theta, whereas it appears much more broadly distributed between 15◦ and 35◦ 2 Theta with maximum between 26◦ and 28◦ 2 Theta for a geopolymer body prepared using the reaction of alkali-silicate solution and metakaolin (AAMK). This is due to the network formed by siloxo and sialate units in the case of AAMK, given that any crystallization can be ruled out. The origin of increasing mechanical strength during the ageing of AAS mortars must be due to further crosslinking of the preformed siloxo chains. Thermal treatment up to 800◦C leads to a complete loss of any mechanical strength of the CEM pastes due to the destruction of crystalline CSH-phases, whereas geopolymer bodies maintain their strength. Implications for next generation concrete include that cement clinker could be completely replaced by using a using alkali silcate solution technology for gel formation. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Tracking heterogeneous structural motifs and the redox behaviour of copper-zinc nanocatalysts for the electrocatalytic CO₂ reduction using operando time resolved spectroscopy and machine learning

Copper-based catalysts are established catalytic systems for the electrocatalytic CO2 reduction reaction (CO2RR), where wasteful CO2 is converted into valuable industrial resources, such as energy-dense C2+ products, using energy from renewable sources. However, better control over the catalyst selectivity, especially at industrially relevant high current density conditions is needed to expedite the economically viability of the CO2RR. For this purpose, bimetallic materials, where copper is combined with a secondary metal, comprise a promising and a highly tunable catalyst for CO2RR. However, the synergy between copper and the selected secondary metal species, the evolution of the bimetallic structural motifs under working conditions and the effect of the secondary metal on the kinetics of the Cu redox behavior require careful investigation. Here, we employ operando quick X-ray absorption spectroscopy (QXAFS), coupled with machine-learning based data analsysis and surface-enhanced Raman spectroscopy (SERS) to investigate the time-dependent chemical and structural changes in catalysts derived from shape-selected Zn/Cu2O nanocubes under CO2RR conditions at current densities up to -500 mA/cm2. We furthermore relate the transformation observed under working conditions to the catalytic activity and selectivity and correlate potential-dependent surface and subsurface processes. We report that the addition of Zn to a Cu-based catalyst has crucial impact on the kinetics of subsurface processes, while redox processes of the Cu surface layer remain largely unaffected. Interestingly, the presence of Zn was found to contribute to the stabilization of cationic Cu(I) species, which is of catalytic relevance since Cu(0)/Cu(I) interfaces have been reported beneficial for the efficient CO2 conversion to complex multicarbon products. At the same time, we attribute the increase of the C2+ product selectivity to the formation of Cu-rich CuZn alloys in samples with low Zn content, while Zn-rich alloy phases result in an increased formation of CO paralleled by an increase of the parasitic hydrogen evolution reaction