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We report the investigation of the dynamic behavior of charge-density waves (CDWs) in a quasi-one-dimensional material K0.3MoO3 using x-ray scattering and multiple x-ray diffraction. Under the application of voltages, we demonstrate that the occurrence of nonlinear conductivity caused by CDW is through the internal deformation of the CDW lattice, i.e., a phase jump of 2π, as the applied voltage exceeds the threshold. By measuring the evolution of peak width of satellite reflections as a function of the field strength, we also report that the CDW lattice can be driven to move and undergo a dynamic phase transition, i.e., from the disordered pinning state to ordered moving solid state, and finally, to disordered moving liquid. [ABSTRACT FROM AUTHOR]

The first observation of the X‐ray multiple‐wave interaction in an incommensurate charge‐density‐wave (CDW) modulated structure at low temperatures is reported for an example of a quasi‐two‐dimensional material, NbSe2‐2H. Via the coherent interaction between the X‐ray waves propagating in the CDW‐modulated structure and the host structure, the phase‐dependent intensity variations of a CDW reflection were detected. In accord with a centrosymmetric structure, the phases of the structure‐factor triplets of two CDW reflections and a Bragg reflection of the host structure were determined to be either 0 or 180°, and not to vary with temperature. Relative phase differences of the two CDW reflections are also deduced. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) has attracted substantial attention on account of its usefulness in producing hydrogen by photoelectrochemical (PEC) water splitting. The exploitation of BiVO4 for this purpose is yet limited by severe charge recombination in the bulk of BiVO4, which is caused by the short diffusion length of the photoexcited charge carriers and inefficient charge separation. Enormous effort has been made to improve the photocurrent density and solar-to-hydrogen conversion efficiency of BiVO4. This study demonstrates that modulating the composition of the electrode and the electronic configuration of BiVO4 by decoration with silver nanoparticles (Ag NPs) is effective in not only enhancing the charge carrier concentration but also suppressing charge recombination in the solar water splitting process. Decoration with a small number of Ag NPs significantly enhances the photocurrent density of BiVO4 to an extent that increases with the concentration of the Ag NPs. At 0.5% Ag NPs, the photocurrent density approaches 4.1 mA cm−2 at 1.23 V versus a reversible hydrogen electrode (RHE) under solar simulated light illumination; this value is much higher than the 2.3 mA cm−2 of pure BiVO4 under the same conditions. X-ray absorption spectroscopy (XAS) is utilized to investigate the electronic structure of pure BiVO4 and its modification by decoration with Ag NPs. Analytical results indicate that increased distortion of the VO4 tetrahedra alters the V 3d–O 2p hybridized states. Additionally, as the Ag concentration increases, the oxygen vacancy defects that act as recombination centers in BiVO4 are reduced. In situ XAS, which is conducted under dark and solar illumination conditions, reveals that the significantly enhanced PEC performance is attributable to the synergy of modulated atomic/electronic structures and the localized surface plasmon resonance effect of the Ag nanoparticles. [ABSTRACT FROM AUTHOR]

Use of aluminum alloy anodes as metal fuel in electrochemical batteries has specific advantages in numerous applications. In this paper, we report novel Al alloy anodes obtained by adding In and Bi to a reported Al ternary-element alloy, Al-Zn-Sn. An electron probe microanalyzer is used to obtain the elemental composition of Al-5Zn-0.1Sn, Al-5Z-0.1Sn-0.1In, and Al-5Zn-0.1Sn-0.1In-0.1Bi. Tafel analysis, electrochemical impedance spectroscopy, and constant-current chronopotentiometry are performed for electrochemical analysis. In addition, the self-corrosion of the alloys is examined to determine the hydrogen evolution and anode discharge stability. These results indicate that Al-5Zn-0.1Sn-0.1In-0.1Bi has the highest anode performance. On the basis of the scanning electron microscopy and transmission electron microscopy microstructure analysis, we propose that the dissolution and sedimentation process induced by Bi nanoprecipitates may activate a passive Al surface, significantly enhancing the discharge efficiency. • Al-5Zn-0.1Sn-0.1In-0.1Bi alloy is first synthesized which displays high discharging performance in battery applications. • XRD, SEM, and TEM showed the minor crystals and grains in Al-5Zn-0.1Sn-0.1In-0.1Bi. • The self-corrosion is examined indicating a dissolution mechanism of the Al alloy. • In and Bi in the Al alloy collapsed during discharge, which refreshed the passivated Al surface. [ABSTRACT FROM AUTHOR]

The open question of crystal symmetry for YBaCuFeO5, still under debate, is resolved by using diffraction anomalous fine structure and resonant multi-beam X-ray diffraction at the Fe and Cu K edges. The different asymmetric intensity distributions observed at 7, 7.1305 and 8.9945 keV give direct evidence that the space group of YBaCuFeO5 should be P4/ mmm with the distance between Cu and apical O atoms longer than that between Fe and O atoms. This approach provides a direct way to resolve detailed structural symmetry which is indeterminate in conventional Bragg diffraction. [ABSTRACT FROM AUTHOR]

Through the detailed studies utilizing x-ray and neutron powder diffraction and magnetometry measurements, we report the magnetic phase transitions in the B-site disorder perovskite oxide PrFe 0.5 Cr 0.5 O 3. The Fe3+/Cr3+ sublattice was observed to form a long-range magnetic order with the G x F z configuration below T N = 270 K from neutron powder diffraction. It then undergoes the second-order phase transition to F x G z spin configuration below 210 K and the transition ends at ~170 K. On the other hand, long range magnetic ordering with F x C y configuration at Pr3+ sublattice can be identified at base temperature. The magnetic phase diagram is derived with spontaneous spin ordering and reorientation at A- and B-sublattices. [ABSTRACT FROM AUTHOR]