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“Solution-gel-based surface modification of LiNi0.5Mn1.5O4-δ with amorphous Li-Ti-O coating”. Ulu Okudur F, Batuk M, Hadermann J, Safari M, De Sloovere D, Kumar Mylavarapu S, Joos B, D'Haen J, Van Bael MK, Hardy A, RSC advances 13, 33146 (2023). http://doi.org/10.1039/D3RA05599J
Abstract: LNMO (LiNi0.5Mn1.5O4-delta) is a high-energy density positive electrode material for lithium ion batteries. Unfortunately, it suffers from capacity loss and impedance rise during cycling due to electrolyte oxidation and electrode/electrolyte interface instabilities at high operating voltages. Here, a solution-gel synthesis route was used to coat 0.5-2.5 mu m LNMO particles with amorphous Li-Ti-O (LTO) for improved Li conduction, surface structural stability and cyclability. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) analysis coupled with energy dispersive X-ray (EDX) showed Ti-rich amorphous coatings/islands or Ti-rich spinel layers on many of the LTO-modified LNMO facets, with a thickness varying from about 1 to 10 nm. The surface modification in the form of amorphous islands was mostly possible on high-energy crystal facets. Physicochemical observations were used to propose a molecular mechanism for the surface modification, combining insights from metalorganic chemistry with the crystallographic properties of LNMO. The improvements in functional properties were investigated in half cells. The cell impedance increased faster for the bare LNMO compared to amorphous LTO modified LNMO, resulting in R-ct values as high as 1247 Omega (after 1000 cycles) for bare LNMO, against 216 Omega for the modified material. At 10C, the modified material boosted a 15% increase in average discharge capacity. The improvements in electrochemical performance were attributed to the increase in electrochemically active surface area, as well as to improved HF-scavenging, resulting in the formation of protective byproducts, generating a more stable interface during prolonged cycling.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.9
DOI: 10.1039/D3RA05599J
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“Site-specific mapping of transition metal oxygen coordination in complex oxides”. Turner S, Egoavil R, Batuk M, Abakumov AA, Hadermann J, Verbeeck J, Van Tendeloo G, Applied physics letters 101, 241910 (2012). http://doi.org/10.1063/1.4770512
Abstract: We demonstrate site-specific mapping of the oxygen coordination number for transition metals in complex oxides using atomically resolved electron energy-loss spectroscopy in an aberration-corrected scanning transmission electron microscope. Pb2Sr2Bi2Fe6O16 contains iron with a constant Fe3+ valency in both octahedral and tetragonal pyramidal coordination and is selected to demonstrate the principle of site-specific coordination mapping. Analysis of the site-specific Fe-L2,3 data reveals distinct variations in the fine structure that are attributed to Fe in a six-fold (octahedron) or five-fold (distorted tetragonal pyramid) oxygen coordination. Using these variations, atomic resolution coordination maps are generated that are in excellent agreement with simulations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 12
DOI: 10.1063/1.4770512
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“Using electron vortex beams to determine chirality of crystals in transmission electron microscopy”. Juchtmans R, Béché, A, Abakumov A, Batuk M, Verbeeck J, Physical review : B : condensed matter and materials physics 91, 094112 (2015). http://doi.org/10.1103/PhysRevB.91.094112
Abstract: We investigate electron vortex beams elastically scattered on chiral crystals. After deriving a general expression for the scattering amplitude of a vortex electron, we study its diffraction on point scatterers arranged on a helix. We derive a relation between the handedness of the helix and the topological charge of the electron vortex on one hand and the symmetry of the higher-order Laue zones in the diffraction pattern on the other for kinematically and dynamically scattered electrons. We then extend this to atoms arranged on a helix as found in crystals which belong to chiral space groups and propose a method to determine the handedness of such crystals by looking at the symmetry of the diffraction pattern. In contrast to alternative methods, our technique does not require multiple scattering, which makes it possible to also investigate extremely thin samples in which multiple scattering is suppressed. In order to verify the model, elastic scattering simulations are performed, and an experimental demonstration on Mn2Sb2O7 is given in which we find the sample to belong to the right-handed variant of its enantiomorphic pair. This demonstrates the usefulness of electron vortex beams to reveal the chirality of crystals in a transmission electron microscope and provides the required theoretical basis for further developments in this field.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 54
DOI: 10.1103/PhysRevB.91.094112
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“Effect of cation dopant radius on the hydrothermal stability of tetragonal zirconia: Grain boundary segregation and oxygen vacancy annihilation”. Zhang F, Batuk M, Hadermann J, Manfredi G, Mariën A, Vanmeensel K, Inokoshi M, Van Meerbeek B, Naert I, Vleugels J, Acta materialia 106, 48 (2016). http://doi.org/10.1016/j.actamat.2015.12.051
Abstract: The hydrothermal aging stability of 3Y-TZP-xM2O3 (M = La, Nd, Sc) was investigated as a function of 0.02–5 mol% M2O3 dopant content and correlated to the overall phase content, t-ZrO2 lattice parameters, grain size distribution, grain boundary chemistry and ionic conductivity.
The increased aging stability with increasing Sc2O3 content and the optimum content of 0.4–0.6 mol% Nd2O3 or 0.2–0.4 mol% La2O3, resulting in the highest aging resistance, could be directly related to the constituent phases and the lattice parameters of the remaining tetragonal zirconia.
At low M2O3 dopant contents ≤0.4 mol%, the different aging behavior of tetragonal zirconia was attributed to the defect structure of the zirconia grain boundary which was influenced by the dopant cation radius. It was observed that the grain boundary ionic resistivity and the aging resistance followed the same trend: La3+ > Nd3+ > Al3+ > Sc3+, proving that hydrothermal aging is driven by the diffusion of water-derived mobile species through the oxygen vacancies. Accordingly, we elucidated the underlying mechanism by which a larger trivalent cation segregating at the zirconia grain boundary resulted in a higher aging resistance.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 37
DOI: 10.1016/j.actamat.2015.12.051
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“Trapping of Oxygen Vacancies at Crystallographic Shear Planes in Acceptor-Doped Pb-Based Ferroelectrics”. Batuk D, Batuk M, Tsirlin AA, Hadermann J, Abakumov AM, Angewandte Chemie: international edition in English 54, 14787 (2015). http://doi.org/10.1002/anie.201507729
Abstract: The defect chemistry of the ferroelectric material PbTiO3 after doping with Fe(III) acceptor ions is reported. Using advanced transmission electron microscopy and powder X-ray and neutron diffraction, we demonstrate that even at concentrations as low as circa 1.7% (material composition approximately ABO2.95), the oxygen vacancies are trapped into extended planar defects, specifically crystallographic shear planes. We investigate the evolution of these defects upon doping and unravel their detailed atomic structure using the formalism of superspace crystallography, thus unveiling their role in nonstoichiometry in the Pb-based perovskites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 3
DOI: 10.1002/anie.201507729
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“Complex Microstructure and Magnetism in Polymorphic CaFeSeO”. Cassidy SJ, Batuk M, Batuk D, Hadermann J, Woodruff DN, Thompson AL, Clarke SJ, Inorganic chemistry 55, 10714 (2016). http://doi.org/10.1021/acs.inorgchem.6b01951
Abstract: The structural complexity of the antiferromagnetic oxide selenide CaFeSeO is described. The compound contains puckered FeSeO layers composed of FeSe2O2 tetrahedra sharing all their vertexes. Two polymorphs coexist that can be derived from an archetype BaZnSO structure by cooperative tilting of the FeSe2O2 tetrahedra. The polymorphs differ in the relative arrangement of the puckered layers of vertex-linked FeSe2O2 tetrahedra. In a noncentrosymmetric Cmc21 polymorph (a = 3.89684(2) A, b = 13.22054(8) A, c = 5.93625(2) A) the layers are related by the C-centering translation, while in a centrosymmetric Pmcn polymorph, with a similar cell metric (a = 3.89557(6) A, b = 13.2237(6) A, c = 5.9363(3) A), the layers are related by inversion. The compound shows long-range antiferromagnetic order below a Neel temperature of 159(1) K with both polymorphs showing antiferromagnetic coupling via Fe-O-Fe linkages and ferromagnetic coupling via Fe-Se-Fe linkages within the FeSeO layers. The magnetic susceptibility also shows evidence for weak ferromagnetism which is modeled in the refinements of the magnetic structure as arising from an uncompensated spin canting in the noncentrosymmetric polymorph. There is also a spin glass component to the magnetism which likely arises from the disordered regions of the structure evident in the transmission electron microscopy.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 6
DOI: 10.1021/acs.inorgchem.6b01951
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“Strength, toughness and aging stability of highly-translucent Y-TZP ceramics for dental restorations”. Zhang F, Inokoshi M, Batuk M, Hadermann J, Naert I, Van Meerbeek B, Vleugels J, Dental Materials 32, e327 (2016). http://doi.org/10.1016/j.dental.2016.09.025
Abstract: OBJECTIVE: The aim was to evaluate the optical properties, mechanical properties and aging stability of yttria-stabilized zirconia with different compositions, highlighting the influence of the alumina addition, Y2O3 content and La2O3 doping on the translucency. METHODS: Five different Y-TZP zirconia powders (3 commercially available and 2 experimentally modified) were sintered under the same conditions and characterized by X-ray diffraction with Rietveld analysis and scanning electron microscopy (SEM). Translucency (n=6/group) was measured with a color meter, allowing to calculate the translucency parameter (TP) and the contrast ratio (CR). Mechanical properties were appraised with four-point bending strength (n=10), single edge V-notched beam (SEVNB) fracture toughness (n=8) and Vickers hardness (n=10). The aging stability was evaluated by measuring the tetragonal to monoclinic transformation (n=3) after accelerated hydrothermal aging in steam at 134 degrees C, and the transformation curves were fitted by the Mehl-Avrami-Johnson (MAJ) equation. Data were analyzed by one-way ANOVA, followed by Tukey's HSD test (alpha=0.05). RESULTS: Lowering the alumina content below 0.25wt.% avoided the formation of alumina particles and therefore increased the translucency of 3Y-TZP ceramics, but the hydrothermal aging stability was reduced. A higher yttria content (5mol%) introduced about 50% cubic zirconia phase and gave rise to the most translucent and aging-resistant Y-TZP ceramics, but the fracture toughness and strength were considerably sacrificed. 0.2mol% La2O3 doping of 3Y-TZP tailored the grain boundary chemistry and significantly improved the aging resistance and translucency. Although the translucency improvement by La2O3 doping was less effective than for introducing a substantial amount of cubic zirconia, this strategy was able to maintain the mechanical properties of typical 3Y-TZP ceramics. SIGNIFICANCE: Three different approaches were compared to improve the translucency of 3Y-TZP ceramics.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 4.07
DOI: 10.1016/j.dental.2016.09.025
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“Computationally Driven Discovery of a Family of Layered LiNiB Polymorphs”. Gvozdetskyi V, Bhaskar G, Batuk M, Zhao X, Wang R, Carnahan SL, Hanrahan MP, Ribeiro RA, Canfield PC, Rossini AJ, Wang C-Z, Ho K-M, Hadermann J, Zaikina JV, Angewandte Chemie: international edition in English 58, 15855 (2019). http://doi.org/10.1002/anie.201907499
Abstract: Two novel lithium nickel boride polymorphs RT-LiNiB and HT-LiNiB with layered crystal structures are reported. This family of compounds was theoretically predicted by using the adaptive genetic algorithm (AGA) and subsequently synthesized via a hydride route with LiH precursor as a lithium source. Being unique among the known ternary transition metal borides, the LiNiB structures feature Li layers alternating with nearly planar [NiB] layers, composed of Ni hexagonal rings centered by B-B pairs. A comprehensive study using a combination of single crystal/synchrotron powder X-ray diffraction data, solid-state 7Li and 11B NMR, scanning transmission electron microscopy, quantum chemistry calculations, and magnetism has shed light on the intrinsic features of these polymorphic compounds. The unique layered structures of LiNiB compounds make them ultimate precursors to further study their exfoliation, paving a way toward two-dimensional transition metal borides, MBenes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
DOI: 10.1002/anie.201907499
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“Exsolution of SrO during the Topochemical Conversion of LaSr3CoRuO8to the Oxyhydride LaSr3CoRuO4H4”. Jin L, Batuk M, Kirschner FKK, Lang F, Blundell SJ, Hadermann J, Hayward MA, Inorganic chemistry 58, 14863 (2019). http://doi.org/10.1021/acs.inorgchem.9b02552
Abstract: Reaction of the n = 1 Ruddlesden-Popper oxide LaSr3CoRuO8 with CaH2 yields the oxyhydride phase LaSr3CoRuO4H4 via topochemical anion-exchange. Close inspection of X-ray and neutron powder diffraction data in combination with HAADF-STEM images reveals that nanoparticles of SrO are exsolved from the system during the reaction, with the change in cation stoichiometry accommodated by the inclusion of n > 1 (Co/Ru)nOn+1H2n ‘perovskite’ layers into the Ruddlesden-Popper stacking sequence. This novel pseudo-topochemical process offers a new route for the formation of n > 1 Ruddlesden-Popper structured materials. Magnetization data are consistent with a LaSr3Co1+Ru2+O4H4 (Co1+, d8, S = 1; Ru2+, d6, S = 0) oxidation/spin state combination. Neutron diffraction and μ+SR data show no evidence for long-range magnetic order down to 2 K, suggesting the diamagnetic Ru2+ centers impede the Co-Co magnetic exchange interactions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 1
DOI: 10.1021/acs.inorgchem.9b02552
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“Structure and magnetic properties of Sm(Fe,Si)(9)C/alpha-Fe nanocomposite magnets”. Bez R, Zehani K, Batuk M, Van Tendeloo G, Mliki N, Bessais L, Journal of alloys and compounds 695, 810 (2017). http://doi.org/10.1016/J.JALLCOM.2016.10.122
Abstract: SmFe8.75 Si-0.25 C/alpha-Fe nanocomposites have been successfully synthesized using high energy milling, followed by annealing at 750 degrees C. The crystal structure of these compounds was characterized by the Rietveld method using powder X-ray diffraction data. By increasing the concentration of Sm, we observed a decrease in the amount of alpha-Fe phase. The morphology of the samples was determined by scanning and transmission electron microscopy. The average grain size is about 20 nm. The magnetic properties were investigated at room temperature and at 10 K. A ferromagnetic behavior was observed in all samples at both temperatures. An increase of the soft magnetic phase alpha-Fe induced an increase in the magnetization and a decrease in coercivity. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.133
Times cited: 1
DOI: 10.1016/J.JALLCOM.2016.10.122
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“Crystal Structure, Defects, Magnetic and Dielectric Properties of the Layered Bi3n+1Ti7Fe3n-3,O9n+11 Perovskite-Anatase lntergrowths”. Batuk D, Batuk M, Filimonov DS, Zakharov KV, Volkova OS, Vasiliev AN, Tyablikov OA, Hadermann J, Abakumov AM, Inorganic chemistry 56, 931 (2017). http://doi.org/10.1021/ACS.INORGCHEM.6B02559
Abstract: The Bi3n+1Ti7Fe3n-3,O9n+11 materials are built of (001)(p) plane parallel perovskite blocks with a thickness of n (Ti,Fe)O-6 octahedra, separated by periodic translational interfaces. The interfaces are based on anatase-like chains of edge -sharing (Ti,Fe)O-6 octahedra. Together with the octahedra of the perovskite blocks, they create S-shaped tunnels stabilized by lone pair Bi3+ cations. In this work, the structure of the n = 4-6 Bi3n+1Ti7Fe3n-3,O9n+11 homologues is analyzed in detail using advanced transmission electron microscopy, powder X-ray diffraction, and Mossbauer spectroscopy. The connectivity of the anatase-like chains to the perovskite blocks results in,a 3ap periodicity along the interfaces, so that they can be located either on top of each other or with shifts of +/- a(p) along [100](p). The ordered arrangement of the interfaces gives rise to orthorhombic Immm and monoclinic A2/m polymorphs with the unit cell parameters a = 3a(p), b = b(p), c = 2(n + 1)c(p) and a = 3a(p), b = b(p), c = 2(n + 1)c(p) – a(p), respectively. While the n = 3 compound is orthorhombic, the monoclinic modification is more favorable in higher homologues. The Bi3n+1Ti7Fe3n-3,O9n+11 structures demonstrate intricate patterns of atomic displacements in the perovskite blocks, which are supported by the stereochemical activity of the Bi3+ cations. These patterns are coupled to the cationic coordination of the oxygen atoms in the (Ti,Fe)O-2 layers at the border of the perovskite blocks. The coupling is strong in the 1/ = 3, 4 homologues, but gradually reduces with the increasing thickness of the perovskite blocks, so that, in the n = 6 compound, the dominant mode of atomic displacements is aligned along the interface planes. The displacements in the adjacent perovskite blocks tend to order antiparallel, resulting in an overall antipolar structure. The Bi3n+1Ti7Fe3n-3,O9n+11 materials demonstrate an unusual diversity of structure defects. The n = 4-6 homologues are robust antiferromagnets below T-N = 135, 220, and 295 K, respectively. They show a high dielectric constant that weakly increases with temperature and is relatively insensitive to the Ti/Fe ratio.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 3
DOI: 10.1021/ACS.INORGCHEM.6B02559
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“Crystal structure study of manganese and titanium substituted BaLaFe2O6-δ”. Ben Hafsia A, Hendrickx M, Batuk M, Khitouni M, Hadermann J, Greneche J-M, Rammeh N, Journal of solid state chemistry 251, 186 (2017). http://doi.org/10.1016/j.jssc.2017.04.019
Abstract: Barium lanthanum ferrite and four Mn/Ti substituted materials were synthesized by the sol-gel method. The crystal structure of the materials was studied by a combination of X-ray powder diffraction, electron diffraction, scanning transmission electron microscopy and 57Fe Mössbauer spectrometry. BaLaFe2O6-δ has a cubic perovskite structure and Ba0.7La1.3FeMnO6-δ is distorted perovskite with the R-3c symmetry, both from electron diffraction and X-ray powder diffraction. However, according to transmission electron microscopy, the crystals of BaLaFeTiO6-δ, BaLaFeTi0.5Mn0.5O6-δ, and BaLaFe0.5Ti0.5MnO6-δ consist of nanodomains with different symmetries (Pm3m next to R-3c due to octahedral tilts), whereas the bulk X-ray powder diffraction patterns for these compounds correspond to the simple cubic structure. 57Fe Mössbauer spectrometry confirms that all materials contain high spin state Fe3+ ions which are strongly influenced by the chemical disorder
resulting from various cationic environments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
DOI: 10.1016/j.jssc.2017.04.019
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“Grain-boundary engineering for aging and slow-crack-growth resistant zirconia”. Zhang F, Chevalier J, Olagnon C, Batuk M, Hadermann J, Van Meerbeek B, Vleugels J, Journal of dental research 96, 774 (2017). http://doi.org/10.1177/0022034517698661
Abstract: Ceramic materials are prone to slow crack growth, resulting in strength degradation over time. Although yttria-stabilized zirconia (Y-TZP) ceramics have higher crack resistance than other dental ceramics, their aging susceptibility threatens their long-term performance in aqueous environments such as the oral cavity. Unfortunately, increasing the aging resistance of Y-TZP ceramics normally reduces their crack resistance. Our recently conducted systematic study of doping 3Y-TZP with various trivalent cations revealed that lanthanum oxide (La2O3) and aluminum oxide (Al2O3) have the most potent effect to retard the aging kinetics of 3Y-TZP. In this study, the crack-propagation behavior of La2O3 and Al2O3 co-doped 3Y-TZP ceramics was investigated by double-torsion methods. The grain boundaries were examined using scanning transmission electron microscopy and energy-dispersive spectroscopy (STEM-EDS). Correlating these analytic data with hydrothermal aging studies using different doping systems, a strategy to strongly bind the segregated dopant cations with the oxygen vacancies at the zirconia-grain boundary was found to improve effectively the aging resistance of Y-TZP ceramics without affecting the resistance to crack propagation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.755
Times cited: 3
DOI: 10.1177/0022034517698661
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“Luminescence Property Upgrading via the Structure and Cation Changing in AgxEu(2–x)/3WO4and AgxGd(2–x)/3–0.3Eu0.3WO4”. Morozov VA, Batuk D, Batuk M, Basovich OM, Khaikina EG, Deyneko DV, Lazoryak BI, Leonidov II, Abakumov AM, Hadermann J, Chemistry of materials 29, 8811 (2017). http://doi.org/10.1021/acs.chemmater.7b03155
Abstract: The creation and ordering of A-cation vacancies and the effect of cation substitutions in the scheelite-type framework are investigated as a factor for controlling the scheelite-type structure and luminescence properties. AgxEu3+(2−x)/3□(1−2x)/3WO4 and AgxGd(2−x)/3−0.3Eu3+0.3□(1−2x)/3WO4 (x = 0.5−0) scheelite-type phases were synthesized by a solid state method, and their structures were investigated using a combination of transmission electron microscopy techniques and powder synchrotron X-ray diffraction. Transmission electron microscopy also revealed the (3 + 1)D incommensurately modulated character of AgxEu3+(2−x)/3□(1−2x)/3WO4 (x = 0.286, 0.2) phases. The crystal structures of the scheelite-based AgxEu3+(2−x)/3□(1−2x)/3WO4 (x = 0.5, 0.286, 0.2) red phosphors have been refined from high resolution synchrotron powder X-ray diffraction data. The luminescence properties of all phases under near-ultraviolet (n-UV) light have been investigated. The excitation spectra of AgxEu3+(2−x)/3□(1−2x)/3WO4 (x = 0.5, 0.286,0.2) phosphors show the strongest absorption at 395 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. The excitation spectra of the Eu2/3□1/3WO4 and Gd0.367Eu0.30□1/3WO4 phases exhibit the highest contribution of the charge transfer band at 250 nm and thus the most efficient energy transfer mechanism between the host and the luminescent ion as compared to direct excitation. The emission spectra of all samples indicate an intense red emission due to the 5D0 → 7F2 transition of Eu3+. Concentration dependence of the 5D0 → 7F2 emission for AgxEu(2−x)/3□(1−2x)/3WO4 samples differs from the same dependence for the earlier studied NaxEu3+(2−x)/3□(1−2x)/3MoO4 (0 ≤ x ≤ 0.5) phases. The intensity of the 5D0 → 7F2 emission is reduced almost 7 times with decreasing x from 0.5 to 0, but it practically does not change in the range from x = 0.286 to x = 0.200. The emission spectra of Gd-containing samples show a completely different trend as compared to only Eu-containing samples. The Eu3+ emission under excitation of Eu3+(5L6) level (λex = 395 nm) increases more than 2.5 times with the increasing Gd3+ concentration from 0.2 (x = 0.5) to 0.3 (x = 0.2) in the AgxGd(2−x)/3−0.3Eu3+0.3□(1−2x)/3WO4, after which it remains almost constant for higher Gd3+ concentrations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 7
DOI: 10.1021/acs.chemmater.7b03155
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“Synthesis and structural characterization of a novel Sillén &ndash, Aurivillius bismuth oxyhalide, PbBi3VO7.5Cl, and its derivatives”. Charkin DO, Plokhikh IV, Kazakov SM, Kalmykov SN, Akinfiev VS, Gorbachev AV, Batuk M, Abakumov AM, Teterin YA, Maslakov KI, Teterin AY, Ivanov KE, Solid state sciences 75, 27 (2018). http://doi.org/10.1016/j.solidstatesciences.2017.11.006
Abstract: A new Sillen – Aurivillius family of layered bismuth oxyhalides has been designed and successfully constructed on the basis of PbBiO2X(X = halogen) synthetic perites and g-form of Bi2VO5.5 solid elec- trolyte. This demonstrates, for the first time, the ability of the latter to serve as a building block in construction of mixed-layer structures. The parent compound PbBi3VO7.5-dCl (d = 0.05) has been investigated by powder XRD, TEM, XPS methods and magnetic susceptibility measurements. An unexpected but important condition for the formation of the mixed-layer structure is partial (ca. 5%) reduction of VV into VIV which probably suppresses competitive formation of apatite-like Pb – Bi vanadates. This reduction also stabilizes the g polymorphic form of Bi2VO5.5 not only in the intergrowth structure, but in Bi2V1-xMxO5.5-y (M – Nb, Sb) solid solutions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.811
Times cited: 1
DOI: 10.1016/j.solidstatesciences.2017.11.006
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“High-temperature properties of (La,Ca)(Fe,Mg,Mo)O3-\delta perovskites as prospective electrode materials for symmetrical SOFC”. Istomin SY, Morozov AV, Abdullayev MM, Batuk M, Hadermann J, Kazakov SM, Sobolev AV, Presniakov IA, Antipov EV, Journal of solid state chemistry 258, 1 (2018). http://doi.org/10.1016/J.JSSC.2017.10.005
Abstract: La1-yCayFe0.5+x(Mg,Mo)(0.5-x)O3-delta oxides with the orthorhombic GdFeO3-type perovskite structure have been synthesized at 1573 K. Transmission electron microscopy study for selected samples shows the coexistence of domains of perovskite phases with ordered and disordered B-cations. Mossbauer spectroscopy studies performed at 300 K and 573 K show that while compositions with low Ca-content (La0.55Ca0.45Fe0.5Mg0.2625Mo0.2375O3-delta and La0.5Ca0.5Fe0.6Mg0.175Mo0.225O3-delta) are nearly oxygen stoichiometric, La0.2Ca0.8Fe0.5Mg0.2625Mo0.2375O3-delta is oxygen deficient with delta approximate to 0.15. Oxides are stable in reducing atmosphere (Ar/H-2, 8%) at 1173 K for 12 h. No additional phases have been observed at XRPD patterns of all studied perovskites and Ce1-xGdxO2-x/2 electrolyte mixtures treated at 1173-1373K, while Fe-rich compositions (x >= 0.1) react with Zr1-xYxO2-x/2 electrolyte above 1273 K. Dilatometry studies reveal that all samples show rather low thermal expansion coefficients (TECs) in air of 11.4-12.7 ppm K-1. In reducing atmosphere their TECs were found to increase up to 12.1-15.4 ppm K-1 due to chemical expansion effect. High-temperature electrical conductivity measurements in air and Ar/H-2 atmosphere show that the highest conductivity is observed for Fe- and Ca-rich compositions. Moderate values of electrical conductivity and TEC together with stability towards chemical interaction with typical SOFC electrolytes make novel Fe-containing perovskites promising electrode materials for symmetrical solid oxide fuel cell.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 5
DOI: 10.1016/J.JSSC.2017.10.005
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“Surface passivation of CIGS solar cells using gallium oxide”. Garud S, Gampa N, Allen TG, Kotipalli R, Flandre D, Batuk M, Hadermann J, Meuris M, Poortmans J, Smets A, Vermang B, Physica status solidi : A : applications and materials science 215, 1700826 (2018). http://doi.org/10.1002/PSSA.201700826
Abstract: This work proposes gallium oxide grown by plasma-enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se-2 (CIGS) solar cells. In preliminary experiments, a metal-insulator-semiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS-CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5nm passivation layer show an substantial absolute improvement of 56mV in open-circuit voltage (V-OC), 1mAcm(-2) in short-circuit current density (J(SC)), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.775
Times cited: 8
DOI: 10.1002/PSSA.201700826
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“Influence of Mono- and Bimetallic PtOx, PdOx, PtPdOx Clusters on CO Sensing by SnO2 Based Gas Sensors”. Kutukov P, Rumyantseva M, Krivetskiy V, Filatova D, Batuk M, Hadermann J, Khmelevsky N, Aksenenko A, Gaskov A, Nanomaterials 8, 917 (2018). http://doi.org/10.3390/nano8110917
Abstract: To obtain a nanocrystalline SnO2 matrix and mono- and bimetallic nanocomposites SnO2/Pd, SnO2/Pt, and SnO2/PtPd, a flame spray pyrolysis with subsequent impregnation was used. The materials were characterized using X-ray diffraction (XRD), a single-point BET method, transmission electron microscopy (TEM), and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with energy dispersive X-ray (EDX) mapping. The electronic state of the metals in mono- and bimetallic clusters was determined using X-ray photoelectron spectroscopy (XPS). The active surface sites were investigated using the Fourier Transform infrared spectroscopy (FTIR) and thermo-programmed reduction with hydrogen (TPR-H-2) methods. The sensor response of blank SnO2 and nanocomposites had a carbon monoxide (CO) level of 6.7 ppm and was determined in the temperature range 60-300 degrees C in dry (Relative Humidity (RH) = 0%) and humid (RH = 20%) air. The sensor properties of the mono- and bimetallic nanocomposites were analyzed on the basis of information on the electronic state, the distribution of modifiers in SnO2 matrix, and active surface centers. For SnO2/PtPd, the combined effect of the modifiers on the electrophysical properties of SnO2 explained the inversion of sensor response from n- to p-types observed in dry conditions.
Keywords: A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
Impact Factor: 3.553
Times cited: 7
DOI: 10.3390/nano8110917
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“Effect of Bimetallic Pd/Pt Clusters on the Sensing Properties of Nanocrystalline SnO2 in the Detection of CO”. Malkov I V, Krivetskii VV, Potemkin D I, Zadesenets A V, Batuk MM, Hadermann J, Marikutsa A V, Rumyantseva MN, Gas'kov AM, Russian journal of inorganic chemistry 63, 1007 (2018). http://doi.org/10.1134/S0036023618080168
Abstract: Nanocrystalline tin dioxide modified by Pd and Pt clusters or by bimetallic PdPt nanoparticles was synthesized. Distribution of the modifers on the SnO2 surface was studied by high-resolution transmission electron microscopy and energy dispersive X-ray microanalysis with element distribution mapping. It was shown that the Pd/Pt ratio in bimetallic particles varies over a broad range and does not depend on the particle diameter. The effect of platinum metals on the reducibility of nanocrystalline SnO2 by hydrogen was determined. The sensing properties of the resulting materials towards 6.7 ppm CO in air were estimated in situ by electrical conductivity measurements. The sensor response of SnO2 modified with bimetallic PdPt particles was a superposition of the signals of samples with Pt and Pd clusters.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 0.787
Times cited: 3
DOI: 10.1134/S0036023618080168
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“Can surface reactivity of mixed crystals be predicted from their counterparts? A case study of (Bi1-xSbx)2Te3 topological insulators”. Volykhov AA, Sanchez-Barriga J, Batuk M, Callaert C, Hadermann J, Sirotina AP, Neudachina VS, Belova AI, Vladimirova NV, Tamm ME, Khmelevsky NO, Escudero C, Perez-Dieste V, Knop-Gericke A, Yashina LV, Journal of materials chemistry C : materials for optical and electronic devices 6, 8941 (2018). http://doi.org/10.1039/C8TC02235F
Abstract: The behavior of ternary mixed crystals or solid solutions and its correlation with the properties of their binary constituents is of fundamental interest. Due to their unique potential for application in future information technology, mixed crystals of topological insulators with the spin-locked, gapless states on their surfaces attract huge attention of physicists, chemists and material scientists. (Bi1-xSbx)(2)Te-3 solid solutions are among the best candidates for spintronic applications since the bulk carrier concentration can be tuned by varying x to obtain truly bulk-insulating samples, where the topological surface states largely contribute to the transport and the realization of the surface quantum Hall effect. As this ternary compound will be evidently used in the form of thin-film devices its chemical stability is an important practical issue. Based on the atomic resolution HAADF-TEM and EDX data together with the XPS results obtained both ex situ and in situ, we propose an atomistic picture of the mixed crystal reactivity compared to that of its binary constituents. We find that the surface reactivity is determined by the probability of oxygen attack on the Te-Sb bonds, which is directly proportional to the number of Te atoms bonded to at least one Sb atom. The oxidation mechanism includes formation of an amorphous antimony oxide at the very surface due to Sb diffusion from the first two quintuple layers, electron tunneling from the Fermi level of the crystal to oxygen, oxygen ion diffusion to the crystal, and finally, slow Te oxidation to the +4 oxidation state. The oxide layer thickness is limited by the electron transport, and the overall process resembles the Cabrera-Mott mechanism in metals. These observations are critical not only for current understanding of the chemical reactivity of complex crystals, but also to improve the performance of future spintronic devices based on topological materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.256
Times cited: 3
DOI: 10.1039/C8TC02235F
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“MnFe0.5Ru0.5O3 : an above-room-temperature antiferromagnetic semiconductor”. Tan X, McCabe EE, Orlandi F, Manuel P, Batuk M, Hadermann J, Deng Z, Jin C, Nowik I, Herber R, Segre CU, Liu S, Croft M, Kang C-J, Lapidus S, Frank CE, Padmanabhan H, Gopalan V, Wu M, Li M-R, Kotliar G, Walker D, Greenblatt M, Journal of materials chemistry C : materials for optical and electronic devices 7, 509 (2019). http://doi.org/10.1039/C8TC05059G
Abstract: A transition-metal-only MnFe0.5Ru0.5O3 polycrystalline oxide was prepared by a reaction of starting materials MnO, MnO2, Fe2O3, RuO2 at 6 GPa and 1873 K for 30 minutes. A combination of X-ray and neutron powder diffraction refinements indicated that MnFe0.5Ru0.5O3 adopts the corundum (alpha-Fe2O3) structure type with space group R (3) over barc, in which all metal ions are disordered. The centrosymmetric nature of the MnFe0.5Ru0.5O3 structure is corroborated by transmission electron microscopy, lack of optical second harmonic generation, X-ray absorption near edge spectroscopy, and Mossbauer spectroscopy. X-ray absorption near edge spectroscopy of MnFe0.5Ru0.5O3 showed the oxidation states of Mn, Fe, and Ru to be 2+/3+, 3+, and similar to 4+, respectively. Resistivity measurements revealed that MnFe0.5Ru0.5O3 is a semiconductor. Magnetic measurements and magnetic structure refinements indicated that MnFe0.5Ru0.5O3 orders antiferromagnetically around 400 K, with magnetic moments slightly canted away from the c axis. Fe-57 Mossbauer confirmed the magnetic ordering and Fe3+ (S = 5/2) magnetic hyperfine splitting. First principles calculations are provided to understand the electronic structure more thoroughly. A comparison of synthesis and properties of MnFe0.5Ru0.5O3 and related corundum Mn2BB'O-6 derivatives is discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.256
Times cited: 1
DOI: 10.1039/C8TC05059G
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“Sub-ppm H2S sensing by tubular ZnO-Co3O4 nanofibers”. Rumyantseva MN, Vladimirova SA, Platonov VB, Chizhov AS, Batuk M, Hadermann J, Khmelevsky NO, Gaskov AM, Sensors And Actuators B-Chemical 307, 127624 (2020). http://doi.org/10.1016/j.snb.2019.127624
Abstract: Tubular ZnO – Co3O4 nanofibers were co-electrospun from polymer solution containing zinc and cobalt acetates. Phase composition, cobalt electronic state and element distribution in the fibers were investigated by XRD, SEM, HRTEM, HAADF-STEM with EDX mapping, and XPS. Bare ZnO has high selective sensitivity to NO and NO2, while ZnO-Co3O4 composites demonstrate selective sensitivity to H2S in dry and humid air. This effect is discussed in terms of transformation of cobalt oxides into cobalt sulfides and change in the acidity of ZnO oxide surface upon cobalt doping. Reduction in response and recovery time is attributed to the formation of a tubular structure facilitating gas transport through the sensitive layer.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.401
DOI: 10.1016/j.snb.2019.127624
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“Topochemical deintercalation of Li from layered LiNiB : toward 2D MBene”. Bhaskar G, Gvozdetskyi V, Batuk M, Wiaderek KM, Sun Y, Wang R, Zhang C, Carnahan SL, Wu X, Ribeiro RA, Bud'ko SL, Canfield PC, Huang W, Rossini AJ, Wang C-Z, Ho K-M, Hadermann J, Zaikina J V, Journal Of The American Chemical Society 143, 4213 (2021). http://doi.org/10.1021/JACS.0C11397
Abstract: The pursuit of two-dimensional (2D) borides, MBenes, has proven to be challenging, not the least because of the lack of a suitable precursor prone to the deintercalation. Here, we studied room-temperature topochemical deintercalation of lithium from the layered polymorphs of the LiNiB compound with a considerable amount of Li stored in between [NiB] layers (33 at. % Li). Deintercalation of Li leads to novel metastable borides (Li similar to 0.5NiB) with unique crystal structures. Partial removal of Li is accomplished by exposing the parent phases to air, water, or dilute HCl under ambient conditions. Scanning transmission electron microscopy and solid-state Li-7 and B-1(1) NMR spectroscopy, combined with X-ray pair distribution function (PDF) analysis and DFT calculations, were utilized to elucidate the novel structures of (Li similar to 0.5NiB) and the mechanism of Li-deintercalation. We have shown that the deintercalation of Li proceeds via a “zip-lock” mechanism, leading to the condensation of single [NiB] layers into double or triple layers bound via covalent bonds, resulting in structural fragments with Li[NiB](2) and Li[NiB](3) compositions. The crystal structure of Li similar to 0.5NiB is best described as an intergrowth of the ordered single [NiB], double [NiB](2), or triple [NiB](3) layers alternating with single Li layers; this explains its structural complexity. The formation of double or triple [NiB] layers induces a change in the magnetic behavior from temperature-independent paramagnets in the parent LiNiB compounds to the spin-glassiness in the deintercalated Li similar to 0.5NiB counterparts. LiNiB compounds showcase the potential to access a plethora of unique materials, including 2D MBenes (NiB).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
DOI: 10.1021/JACS.0C11397
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“Chemistry, local molybdenum clustering, and electrochemistry in the Li2+xMo1-xO3 solid solutions”. Savina AA, Saiutina VV, Morozov AV, Boev AO, Aksyonov DA, Dejoie C, Batuk M, Bals S, Hadermann J, Abakumov AM, Inorganic chemistry 61, 5637 (2022). http://doi.org/10.1021/ACS.INORGCHEM.2C00420
Abstract: A broad range of cationic nonstoichiometry has been demonstratedfor the Li-rich layered rock-salt-type oxide Li2MoO3, which has generally been considered as a phase with a well-defined chemical composition. Li2+xMo1-xO3(-0.037 <= x <= 0.124) solid solutions were synthesized via hydrogen reduction ofLi2MoO4in the temperature range of 650-1100 degrees C, withxdecreasing with theincrease of the reduction temperature. The solid solutions adopt a monoclinicallydistorted O3-type layered average structure and demonstrate a robust localordering of the Li cations and Mo3triangular clusters within the mixed Li/Mocationic layers. The local structure was scrutinized in detail by electron diffractionand aberration-corrected scanning transmission electron microcopy (STEM),resulting in an ordering model comprising a uniform distribution of the Mo3clusters compatible with local electroneutrality and chemical composition. The geometry of the triangular clusters with their oxygenenvironment (Mo3O13groups) has been directly visualized using differential phase contrast STEM imaging. The established localstructure was used as input for density functional theory (DFT)-based calculations; they support the proposed atomic arrangementand provide a plausible explanation for the staircase galvanostatic charge profiles upon electrochemical Li+extraction fromLi2+xMo1-xO3in Li cells. According to DFT, all electrochemical capacity in Li2+xMo1-xO3solely originates from the cationic Moredox process, which proceeds via oxidation of the Mo3triangular clusters into bent Mo3chains where the electronic capacity of the clusters depends on the initial chemical composition and Mo oxidation state defining the width of the first charge low-voltageplateau. Further oxidation at the high-voltage plateau proceeds through decomposition of the Mo3chains into Mo2dimers and further into individual Mo6+cations
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.6
Times cited: 3
DOI: 10.1021/ACS.INORGCHEM.2C00420
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“Nanoscale phase separation in the oxide layer at GeTe (111) surfaces”. Frolov AS, Callaert C, Batuk M, Hadermann J, Volykhov AA, Sirotina AP, Amati M, Gregoratti L, Yashina LV, Nanoscale 14, 12918 (2022). http://doi.org/10.1039/D2NR02261C
Abstract: As a semiconductor ferroelectric, GeTe has become a focus of renewed attention due to the recent discovery of giant Rashba splitting. It already has a wide range of applications, from thermoelectricity to data storage. Its stability in ambient air, as well as the structure and properties of an oxide layer, define the processing media for device production and operation. Here, we studied a reaction between the GeTe (111) surface and molecular oxygen for crystals having solely inversion domains. We evaluated the reaction kinetics both ex situ and in situ using NAP XPS. The structure of the oxide layer is extensively discussed, where, according to HAADF-STEM and STEM-EDX, nanoscale phase separation of GeO2 and Te is observed, which is unusual for semiconductors. We believe that such behaviour is closely related to the ferroelectric properties and the domain structure of GeTe.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 6.7
DOI: 10.1039/D2NR02261C
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“Impact of anionic ordering on the iron site distribution and valence states in oxyfluoride Sr2FeO3+xF1-x(x=0.08, 0.2) with a layered Perovskite network”. Gamon J, Bassat J-M, Villesuzanne A, Duttine M, Batuk M, Vandemeulebroucke D, Hadermann J, Alassani F, Weill F, Durand E, Demourgues A, Inorganic chemistry 62, 10822 (2023). http://doi.org/10.1021/ACS.INORGCHEM.3C01455
Abstract: Sr2FeO3+x F1-x (x = 0.08, 0.2), an n = 1 Ruddlesden-Popperphase, was synthesized from the oxidationof Sr2FeO3F in air at high temperature followinga fluorine for oxygen substitution and Fe3+ to Fe4+ oxidation. A structural investigation of both compounds was performedusing complementary and high-resolution techniques (Synchrotron X-rayand electron diffraction, Mo''ssbauer spectroscopy, HR-STEM)coupled to DFT calculation. This study reveals that oxidation leadsto a high degree of apical anion disorder coupled to antiphase boundaries. Sr2FeO3F, an oxyfluoride compoundwith an n = 1 Ruddlesden-Popper structure,was identifiedas a potential interesting mixed ionic and electronic conductor (MIEC).The phase can be synthesized under a range of different pO(2) atmospheres, leading to various degrees of fluorinefor oxygen substitution and Fe4+ content. A structuralinvestigation and thorough comparison of both argon- and air-synthesizedcompounds were performed by combining high-resolution X-ray and electrondiffraction, high-resolution scanning transmission electron microscopy,Mo''ssbauer spectroscopy, and DFT calculations. While the argon-synthesizedphase shows a well-behaved O/F ordered structure, this study revealedthat oxidation leads to averaged large-scale anionic disorder on theapical site. In the more oxidized Sr2FeO3.2F0.8 oxyfluoride, containing 20% of Fe4+, two differentFe positions can be identified with a 32%/68% occupancy (P4/nmm space group). This originates due to the presenceof antiphase boundaries between ordered domains within the grains.Relations between site distortion and valence states as well as stabilityof apical anionic sites (O vs F) are discussed. This study paves theway for further studies on both ionic and electronic transport propertiesof Sr2FeO3.2F0.8 and its use in MIEC-baseddevices, such as solid oxide fuel cells.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.6
DOI: 10.1021/ACS.INORGCHEM.3C01455
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“Incommensurate Modulations and Perovskite Growth in LaxSr2–xMnO4−δAffecting Solid Oxide Fuel Cell Conductivity”. Vandemeulebroucke D, Batuk M, Hajizadeh A, Wastiaux M, Roussel P, Hadermann J, Chemistry of Materials (2024). http://doi.org/10.1021/acs.chemmater.3c03199
Abstract: Ruddlesden-Popper La????Sr2−????MnO4−???? materials are interesting symmetric solid oxide
fuel cell electrodes due to their good redox stability, mixed ionic and electronic conducting behavior and thermal expansion that matches well with common electrolytes. In reducing environments – as at a solid oxide fuel cell anode – the x = 0.5 member, i.e. La0.5Sr1.5MnO4−????, has a much higher total conductivity than compounds with a different La/Sr ratio, although all those compositions have the same K2NiF4-type I4/mmm structure. The origin for this conductivity difference is not yet known in literature. Now, a combination of in-situ and ex-situ 3D electron diffraction, high-resolution imaging, energy-dispersive X-ray analysis and electron energy-loss spectroscopy uncovered clear differences between x=0.25 and x=0.5 in the pristine structure, as well as in the transformations upon high-temperature reduction. In La0.5Sr1.5MnO4−????, Ruddlesden-Popper n=2 layer defects and an amorphous surface layer are present, but not in La0.25Sr1.75MnO4−????. After annealing at 700°C in 5% H2/Ar, La0.25Sr1.75MnO4−???? transforms to a tetragonal 2D incommensurately modulated structure with modulation vectors ⃗????1 = 0.2848(1) · (⃗????* +⃗????*) and ⃗????2 =0.2848(1) · (⃗????* – ⃗????*), whereas La0.5Sr1.5MnO4−???? only partially transforms to an orthorhombic 1D incommensurately modulated structure,
with ⃗???? = 0.318(2) · ⃗????*. Perovskite domains grow at the crystal edge at 700°C in 5%
H2 or vacuum, due to the higher La concentration on the surface compared to the bulk, which leads to a different thermodynamic equilibrium. Since it is known that a lower degree of oxygen vacancy ordering and a higher amount of perovskite blocks enhance oxygen mobility, those differences in defect structure and structural transformation upon reduction, might all contribute to the higher conductivity of La0.5Sr1.5MnO4−???? in solid oxide fuel cell anode conditions compared to other La/Sr ratios.
Keywords: A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ;
Impact Factor: 8.6
DOI: 10.1021/acs.chemmater.3c03199
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“Disproportionation of Co2+ in the topochemically reduced oxide LaSrCoRuO₅”. Liang Z, Batuk M, Orlandi F, Manuel P, Hadermann J, Hayward MA, Angewandte Chemie: international edition in English 63, e202313067 (2024). http://doi.org/10.1002/ANIE.202313067
Abstract: Complex transition-metal oxides exhibit a wide variety of chemical and physical properties which are a strong function the local electronic states of the transition-metal centres, as determined by a combination of metal oxidation state and local coordination environment. Topochemical reduction of the double perovskite oxide, LaSrCoRuO6, using Zr, yields LaSrCoRuO5. This reduced phase contains an ordered array of apex-linked square-based pyramidal Ru3+O5, square-planar Co1+O4 and octahedral Co3+O6 units, consistent with the coordination-geometry driven disproportionation of Co2+. Coordination-geometry driven disproportionation of d(7) transition-metal cations (e.g. Rh2+, Pd3+, Pt3+) is common in complex oxides containing 4d and 5d metals. However, the weak ligand field experienced by a 3d transition-metal such as cobalt leads to the expectation that d(7+) Co2+ should be stable to disproportionation in oxide environments, so the presence of Co1+O4 and Co3+O6 units in LaSrCoRuO5 is surprising. Low-temperature measurements indicate LaSrCoRuO5 adopts a ferromagnetically ordered state below 120 K due to couplings between S=(1)/(2) Ru3+ and S=1 Co1+.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 16.6
DOI: 10.1002/ANIE.202313067
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“Revealing pH-Dependent Activities and Surface Instabilities for Ni-Based Electrocatalysts during the Oxygen Evolution Reaction”. Yang C, Batuk M, Jacquet Q, Rousse G, Yin W, Zhang L, Hadermann J, Abakumov AM, Cibin G, Chadwick A, Tarascon J-M, Grimaud A, ACS energy letters , 2884 (2018). http://doi.org/10.1021/acsenergylett.8b01818
Abstract: Multiple electrochemical processes are involved at the catalyst/ electrolyte interface during the oxygen evolution reaction (OER). With the purpose of elucidating the complexity of surface dynamics upon OER, we systematically studied two Ni-based crystalline oxides (LaNiO3−δ and La2Li0.5Ni0.5O4) and compared them with the state-of-the-art Ni−Fe (oxy)- hydroxide amorphous catalyst. Electrochemical measurements such as rotating ring disk electrode (RRDE) and electrochemical quartz microbalance microscopy (EQCM) coupled with a series of physical characterizations including transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS) were conducted to unravel the exact pH effect on both the OER activity and the catalyst stability. We demonstrate that for Ni-based crystalline catalysts the rate for surface degradation depends on the pH and is greater than the rate for surface reconstruction. This behavior is unlike that for the amorphous Ni oxyhydroxide catalyst, which is found to be more stable and pH-independent.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
DOI: 10.1021/acsenergylett.8b01818
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“Understanding the Activation of Anionic Redox Chemistry in Ti4+-Substituted Li2MnO3as a Cathode Material for Li-Ion Batteries”. Paulus A, Hendrickx M, Mayda S, Batuk M, Reekmans G, von Holst M, Elen K, Abakumov AM, Adriaensens P, Lamoen D, Partoens B, Hadermann J, Van Bael MK, Hardy A, ACS applied energy materials 6, 6956 (2023). http://doi.org/10.1021/acsaem.3c00451
Abstract: Layered Li-rich oxides, demonstrating both cationic and anionic redox chemistry being used as positive electrodes for Li-ion batteries,have raised interest due to their high specific discharge capacities exceeding 250 mAh/g. However, irreversible structural transformations triggered by anionic redox chemistry result in pronounced voltagefade (i.e., lowering the specific energy by a gradual decay of discharge potential) upon extended galvanostatic cycling. Activating or suppressing oxygen anionic redox through structural stabilization induced by redox-inactivecation substitution is a well-known strategy. However, less emphasishas been put on the correlation between substitution degree and theactivation/suppression of the anionic redox. In this work, Ti4+-substituted Li2MnO3 was synthesizedvia a facile solution-gel method. Ti4+ is selected as adopant as it contains no partially filled d-orbitals. Our study revealedthat the layered “honeycomb-ordered” C2/m structure is preserved when increasing the Ticontent to x = 0.2 in the Li2Mn1-x Ti (x) O-3 solidsolution, as shown by electron diffraction and aberration-correctedscanning transmission electron microscopy. Galvanostatic cycling hintsat a delayed oxygen release, due to an improved reversibility of theanionic redox, during the first 10 charge-discharge cyclesfor the x = 0.2 composition compared to the parentmaterial (x = 0), followed by pronounced oxygen redoxactivity afterward. The latter originates from a low activation energybarrier toward O-O dimer formation and Mn migration in Li2Mn0.8Ti0.2O3, as deducedfrom first-principles molecular dynamics (MD) simulations for the“charged” state. Upon lowering the Ti substitution to x = 0.05, the structural stability was drastically improvedbased on our MD analysis, stressing the importance of carefully optimizingthe substitution degree to achieve the best electrochemical performance.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 6.4
DOI: 10.1021/acsaem.3c00451
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