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1. Low-energy quasi-circular electron correlations with charge order wavelength in Bi ₂ Sr ₂ CaCu ₂ O _8+δ

   https://doi.org/10.1126/sciadv.adg3710  

   Scott, Kirsty; Kisiel, Elliot; Boyle, Timothy J.; Basak, Rourav; Jargot, Gaëtan; Das, Sarmistha; Agrestini, Stefano; Garcia-Fernandez, Mirian; Choi, Jaewon; Pelliciari, Jonathan; et al (July 2023, Science Advances)

   Most resonant inelastic x-ray scattering (RIXS) studies of dynamic charge order correlations in the cuprates have focused on the high-symmetry directions of the copper oxide plane. However, scattering along other in-plane directions should not be ignored as it may help understand, for example, the origin of charge order correlations or the isotropic scattering resulting in strange metal behavior. Our RIXS experiments reveal dynamic charge correlations over theq_x-q_yscattering plane in underdoped Bi₂Sr₂CaCu₂O_8+δ. Tracking the softening of the RIXS-measured bond-stretching phonon, we show that these dynamic correlations exist at energies below approximately 70 meV and are centered around a quasi-circular manifold in theq_x-q_yscattering plane with radius equal to the magnitude of the charge order wave vector,q_CO. This phonon-tracking procedure also allows us to rule out fluctuations of short-range directional charge order (i.e., centered around [q_x= ±q_CO,q_y= 0] and [q_x= 0,q_y= ±q_CO]) as the origin of the observed correlations. 

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2. Enhancement of Ni–(Y ₂ O ₃ ) _0.08 (ZrO ₂ ) _0.92 fuel electrode performance by infiltration of Ce _0.8 Gd _0.2 O _2−δ nanoparticles

   https://doi.org/10.1039/c9ta12316d  

   Park, Beom-Kyeong; Scipioni, Roberto; Cox, Dalton; Barnett, Scott A. (February 2020, Journal of Materials Chemistry A)

   This paper addresses the use of Ce 0.8 Gd 0.2 O 2−δ (GDC) infiltration into the Ni–(Y 2 O 3 ) 0.08 (ZrO 2 ) 0.92 (YSZ) fuel electrode of solid oxide cells (SOCs) for improving their electrochemical performance in fuel cell and electrolysis operation. Although doped ceria infiltration into Ni–YSZ has recently been shown to improve the electrode performance and stability, the mechanisms defining how GDC impacts electrochemical characteristics are not fully delineated. Furthermore, the electrochemical characteristics have not yet been determined over the full range of conditions normally encountered in fuel cell and electrolysis operation. Here we present a study of both symmetric and full cells aimed at understanding the electrochemical mechanisms of GDC-modified Ni–YSZ over a wide range of fuel compositions and temperatures. Single-step GDC infiltration at an appropriate loading substantially reduced the polarization resistance of Ni–YSZ electrodes in electrolyte-supported cells, as measured using electrochemical impedance spectroscopy (EIS) at various temperatures (600–800 °C) in a range of H 2 O–H 2 mixtures (3–90 vol% H 2 O). Fuel-electrode-supported cells had significant concentration polarization due to the thick Ni–YSZ supports. A distribution of relaxation times approach is used to develop a physically-based electrochemical model; the results show that GDC reduces the reaction resistance associated with three-phase boundaries, but also appears to improve oxygen transport in the electrode. Increasing the H 2 O fraction in the H 2 –H 2 O fuel mixture reduced both the three-phase boundary resistance and the gas diffusion resistance for Ni–YSZ; with GDC infiltration, the electrode resistance showed less variation with fuel composition. GDC infiltration improved the performance of fuel-electrode-supported full cells, which yielded a maximum power density of 2.28 W cm −2 in fuel cell mode and an electrolysis current density at 1.3 V of 2.22 A cm −2 , both at 800 °C. 

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3. Identification of critical buffer traps in Si δ-doped β-Ga ₂ O ₃ MESFETs

   https://doi.org/10.1063/1.5118250  

   McGlone, Joe F.; Xia, Zhanbo; Joishi, Chandan; Lodha, Saurabh; Rajan, Siddharth; Ringel, Steven; Arehart, Aaron R. (October 2019, Applied Physics Letters)
4. One Step Synthesis of Sr ₂ Fe _1.3 Co _0.2 Mo _0.5 O _6−δ -Gd _0.1 Ce _0.9 O _2−δ for Symmetrical Solid Oxide Fuel Cells

   https://doi.org/10.1149/1945-7111/ab8927  

   Yang, Yanru; Li, Shishuai; Yang, Zhibin; Chen, Yu; Zhang, Panpan; Wang, Yuhao; Chen, Fanglin; Peng, Suping (May 2020, Journal of The Electrochemical Society)

   null (Ed.)
5. Free-standing bilayered vanadium oxide films synthesized by liquid exfoliation of chemically preintercalated δ-Li _x V ₂ O ₅ · n H ₂ O

   https://doi.org/10.1039/D1MA00085C  

   Houseman, Luke; Mukherjee, Santanu; Andris, Ryan; Zachman, Michael J.; Pomerantseva, Ekaterina (April 2021, Materials Advances)

   null (Ed.)

   A free-standing film composed of bilayered vanadium oxide nanoflakes is for the first time synthesized using a new low-energy process. The precursor powder, δ-Li x V 2 O 5 · n H 2 O, was prepared using a simple sol–gel based chemical preintercalation synthesis procedure. δ-Li x V 2 O 5 · n H 2 O was dispersed and probe sonicated in N -methyl pyrrolidone to exfoliate the bilayers followed by vacuum filtration resulting in the formation of a free-standing film with obsidian color. X-ray diffraction showed lamellar ordering of a single-phase material with a decreased interlayer distance compared to that of the precursor powder. Scanning electron microscopy images demonstrated stacking of the individual nanoflakes. This morphology was further confirmed with scanning transmission electron microscopy that showed highly malleable nanoflakes consisting of ∼10–100 vanadium oxide bilayers. One of the most important consequences of this morphological rearrangement is that the electronic conductivity of the free-standing film, measured by the four-probe method, increased by an order of magnitude compared to conductivity of the pressed pellet made of precursor powder. X-ray photoelectron spectroscopy measurements showed the coexistence of both V 5+ and V 4+ oxidation states in the exfoliated sample, possibly contributing to the change in electronic conductivity. The developed approach provides the ability to maintain the phase purity and crystallographic order during the exfoliation process, coupled with the formation of a free-standing film of enhanced conductivity. The produced bilayered vanadium oxide nanoflakes can be used as the building blocks for the synthesis of versatile two-dimensional heterostructures to create innovative electrodes for electrochemical energy storage applications. 

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