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“Uniform patterns of Fe-vacancy ordering in the Kx(Fe,Co)2-ySe2 superconductors”. Kazakov SM, Abakumov AM, Perz-Mato JM, Ovchinnikov AV, Roslova MV, Boltalin AI, Morozov IV, Antipov EV, Van Tendeloo G, Chemistry of materials 23, 4311 (2011). http://doi.org/10.1021/cm201203h
Abstract: The Fe-vacancy ordering patterns in the superconducting KxFe2ySe2 and nonsuperconducting Kx(Fe,Co)2ySe2 samples have been investigated by electron diffraction and high angle annular dark field scanning transmission electron microscopy. The Fe-vacancy ordering occurs in the ab plane of the parent ThCr2Si2-type structure, demonstrating two types of patterns. Superstructure I retains the tetragonal symmetry and can be described with the aI = bI = as√5 (as is the unit cell parameter of the parent ThCr2Si2-type structure) supercell and I4/m space group. Superstructure II reduces the symmetry to orthorhombic with the aII = as√2, bII = 2as√2 supercell and the Ibam space group. This type of superstructure is observed for the first time in KxFe2ySe2. The Fe-vacancy ordering is inhomogeneous: the disordered areas interleave with the superstructures I and II in the same crystallite. The observed superstructures represent the compositionally dependent uniform ordering patterns of two species (the Fe atoms and vacancies) on a square lattice. More complex uniform ordered configurations, including compositional stripes, can be predicted for different chemical compositions of the KxFe2ySe2 (0 < y < 0.5) solid solutions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 20
DOI: 10.1021/cm201203h
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“Antisite Disorder and Bond Valence Compensation in Li2FePO4F Cathode for Li-Ion Batteries”. Karakulina OM, Khasanova NR, Drozhzhin OA, Tsirlin AA, Hadermann J, Antipov EV, Abakumov AM, Chemistry Of Materials 28, 7578 (2016). http://doi.org/10.1021/acs.chemmater.6b03746
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 10
DOI: 10.1021/acs.chemmater.6b03746
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“The Li3RuyNb1-yO4 (0 ≤y&le, 1) System: Structural Diversity and Li Insertion and Extraction Capabilities”. Jacquet Q, Perez A, Batuk D, Van Tendeloo G, Rousse G, Tarascon J-M, Chemistry of materials 29, 5331 (2017). http://doi.org/10.1021/acs.chemmater.7b01511
Abstract: Searching for novel high-capacity electrode materials combining cationic and anionic redox processes is an ever-growing activity within the field of Li-ion batteries. In this respect, we report on the exploration of the Li3RuyNb1-yO4 (O <= y <= 1) system with an O/M ratio of 4 to maximize the number of oxygen lone pairs, responsible for the anionic redox. We show that this system presents a very rich crystal chemistry with the existence of four structural types, which derive from the rocksalt structure but differ in their cationic arrangement, creating either zigzag, helical, jagged chains or clusters. From an electrochemical standpoint, these compounds are active on reduction via a classical cationic insertion process. The oxidation process is more complex, because of the instability of the delithiated phase. Our results promote the use of the rich Li3MO4 family as a viable platform for a better understanding of the relationships between structure and anionic redox activity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 17
DOI: 10.1021/acs.chemmater.7b01511
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“Alloy CsCdxPb1–xBr3Perovskite Nanocrystals: The Role of Surface Passivation in Preserving Composition and Blue Emission”. Imran M, Ramade J, Di Stasio F, De Franco M, Buha J, Van Aert S, Goldoni L, Lauciello S, Prato M, Infante I, Bals S, Manna L, Chemistry Of Materials 32, acs.chemmater.0c03825 (2020). http://doi.org/10.1021/acs.chemmater.0c03825
Abstract: Various strategies have been proposed to engineer the band gap of metal halide perovskite nanocrystals (NCs) while preserving their structure and composition and thus ensuring spectral stability of the emission color. An aspect that has only been marginally investigated is how the type of surface passivation influences the structural/color stability of AMX3 perovskite NCs composed of two different M2+ cations. Here, we report the synthesis of blue-emitting Cs-oleate capped CsCdxPb1–xBr3 NCs, which exhibit a cubic perovskite phase containing Cd-rich domains of Ruddlesden–Popper phases (RP phases). The RP domains spontaneously transform into pure orthorhombic perovskite ones upon NC aging, and the emission color of the NCs shifts from blue to green over days. On the other hand, postsynthesis ligand exchange with various Cs-carboxylate or ammonium bromide salts, right after NC synthesis, provides monocrystalline NCs with cubic phase, highlighting the metastability of RP domains. When NCs are treated with Cs-carboxylates (including Cs-oleate), most of the Cd2+ ions are expelled from NCs upon aging, and the NCs phase evolves from cubic to orthorhombic and their emission color changes from blue to green. Instead, when NCs are coated with ammonium bromides, the loss of Cd2+ ions is suppressed and the NCs tend to retain their blue emission (both in colloidal dispersions and in electroluminescent devices), as well as their cubic phase, over time. The improved compositional and structural stability in the latter cases is ascribed to the saturation of surface vacancies, which may act as channels for the expulsion of Cd2+ ions from NCs.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.6
Times cited: 44
DOI: 10.1021/acs.chemmater.0c03825
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“Layered Silicate Clays as Templates for Anisotropic Gold Nanoparticle Growth”. Hill EH, Claes N, Bals S, Liz-Marzán LM, Chemistry of materials 28, 5131 (2016). http://doi.org/10.1021/acs.chemmater.6b02186
Abstract: Clay minerals are abundant natural materials arising in the presence of water and are composed of small particles of different sizes and shapes. The interlamellar space between layered silicate clays can also be used to host a variety of different organic and inorganic guest molecules or particles. Recent studies of clay−metal hybrids formed by impregnation of nanoparticles into the interlayer spaces of the clays have not demonstrated the ability for templated growth following the shape of the particles. Following this line of interest, a method for the synthesis of gold nanoparticles on the synthetic layered silicate clay laponite was developed. This approach can be used to make metal−clay nanoparticles with a variety of morphologies while retaining the molecular adsorption properties of the clay. The surface enhanced Raman scattering enhancement of these particles was also found to be greater than that obtained from other metal nanoparticles of a similar morphology, likely due to increased dye adsorption by the presence of the clay. The hybrid particles presented herein will contribute to further study of plasmonic
sensing, catalysis, dye aggregation, and novel composite materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 13
DOI: 10.1021/acs.chemmater.6b02186
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“Structural and magnetotransport transitions in the electron-doped Pr1-xSrxMnO3(0.85\leq x\leq1) manganites”. Hervieu M, Martin C, Maignan A, Van Tendeloo G, Jirak Z, Hejtmanek J, Barnabe A, Thopart D, Raveau B, Chemistry and materials 12, 1456 (2000). http://doi.org/10.1021/cm000016o
Abstract: The exploration of the Mn4+-rich side of the Pr1-xSrxMnO3 system has allowed the extension of the domain of the cubic perovskite, by using a two-step process, combining synthesis under Ar flow at high temperature and O-2 pressure annealing at lower temperature. We show that these Pr-doped cubic perovskites exhibit a coupled structural (cubic-tetragonal) and magnetic (para-antiferro) transition connected with a resistivity jump at the same temperature. The strong interplay between lattice, charges, and spins for these oxides results from the appearance at low temperature of the distorted C-type antiferromagnetic structure. The Pr1-xSrxMnO3 magnetic phase diagram shows, for 0.9 less than or equal to x less than or equal to 1 (i.e., on the Mn4+-rich side), the existence at low temperature of C- and G-type antiferromagnetism. The absence of ferromagnetic-antiferromagnetic competition explains that magnetoresistante properties are not observed in this system, in contrast to Mn4+-rich Ln(1-x)Ca(x)MnO(3) systems.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 24
DOI: 10.1021/cm000016o
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“Iron catalysts for the growth of carbon nanofibers : Fe, Fe3C or both?”.He Z, Maurice J-L, Gohier A, Lee CS, Pribat D, Cojocaru CS, Chemistry of materials 23, 5379 (2011). http://doi.org/10.1021/cm202315j
Abstract: Iron is a widely used catalyst for the growth of carbon nanotubes (CNTs) or carbon nanofibers (CNFs) by catalytic chemical vapor deposition. However, both Fe and FeC compounds (generally, Fe3C) have been found to catalyze the growth of CNTs/CNFs, and a comparison study of their respective catalytic activities is still missing. Furthermore, the control of the crystal structure of iron-based catalysts, that is α-Fe or Fe3C, is still a challenge, which not only obscures our understanding of the growth mechanisms of CNTs/CNFs, but also complicates subsequent procedures, such as the removal of catalysts for better industrial applications. Here, we show a partial control of the phase of iron catalysts (α-Fe or Fe3C), obtained by varying the growth temperatures during the synthesis of carbon-based nanofibers/nanotubes in a plasma-enhanced chemical vapor deposition reactor. We also show that the structure of CNFs originating from Fe3C is bamboo-type, while that of CNFs originating from Fe is not. Moreover, we directly compare the growth rates of carbon-based nanofibers/nanotubes during the same experiments and find that CNFs/CNTs grown by α-Fe nanoparticles are longer than CNFs grown from Fe3C nanoparticles. The influence of the type of catalyst on the growth of CNFs is analyzed and the corresponding possible growth mechanisms, based on the different phases of the catalysts, are discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 91
DOI: 10.1021/cm202315j
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“From 2D to 3D : bridging self-assembled monolayers to a substrate-induced polymorph in a molecular semiconductor”. Hao Y, Velpula G, Kaltenegger M, Bodlos WR, Vibert F, Mali KS, De Feyter S, Resel R, Geerts YH, Van Aert S, Beljonne D, Lazzaroni R, Chemistry of materials 34, 2238 (2022). http://doi.org/10.1021/ACS.CHEMMATER.1C04038
Abstract: In this study, a new bottom-up approach is proposed to predict the crystal structure of the substrate-induced polymorph (SIP) of an archetypal molecular semiconductor. In spite of intense efforts, the formation mechanism of SIPs is still not fully understood, and predicting their crystal structure is a very delicate task. Here, we selected lead phthalocyanine (PbPc) as a prototypical molecular material because it is a highly symmetrical yet nonplanar molecule and we demonstrate that the growth and crystal structure of the PbPc SIPs can be templated by the corresponding physisorbed self-assembled molecular networks (SAMNs). Starting from SAMNs of PbPc formed at the solution/graphite interface, the structural and energetic aspects of the assembly were studied by a combination of in situ scanning tunneling microscopy and multiscale computational chemistry approach. Then, the growth of a PbPc SIP on top of the physisorbed monolayer was modeled without prior experimental knowledge, from which the crystal structure of the SIP was predicted. The theoretical prediction of the SIP was verified by determining the crystal structure of PbPc thin films using X-ray diffraction techniques, revealing the formation of a new polymorph of PbPc on the graphite substrate. This study clearly illustrates the correlation between the SAMNs and SIPs, which are traditionally considered as two separate but conceptually connected research areas. This approach is applicable to molecular materials in general to predict the crystal structure of their SIPs.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.6
DOI: 10.1021/ACS.CHEMMATER.1C04038
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“Existence of superstructures due to large amounts of Fe vacancies in the LiFePO4-type framework”. Hamelet S, Casas-Cabanas M, Dupont L, Davoisne C, Tarascon JM, Masquelier C, Chemistry of materials 23, 32 (2011). http://doi.org/10.1021/cm102511m
Abstract: LiFePO4 has been under intense scrutiny over the past decade because it stands as an attractive positive electrode material for the next generation of Li-ion batteries to power electric vehicles and hybrid electric vehicles, hence the importance of its thermal behavior. The reactivity of LiFePO4 with air at moderate temperatures is shown to be dependent on its particle size. For nanosized materials, a progressive displacement of Fe from the core structure leading to a composite made of nanosize Fe2O3 and highly defective, oxidized LixFeyPO4 compositions, among which the “ideal” formula LiFe2/3PO4. Herein we report, from both temperature-controlled X-ray diffraction and electronic diffraction microscopy, that these off-stoichiometry olivine-type compounds show a defect ordering resulting in the formation of a superstructure. Such a finding shows striking similarities with the temperature-driven oxidation of fayalite Fe2SiO4 (another olivine) to structurally defective laihunite, reported in the literature three decades ago.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 30
DOI: 10.1021/cm102511m
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“Comment on ALaMn2O6-y (A = K, Rb): novel ferromagnetic manganites exhibiting negative giant magnetoresistance”. Hadermann J, Abakumov AM, Van Rompaey S, Mankevich AS, Korsakov IE, Chemistry of materials 21, 2000 (2009). http://doi.org/10.1021/cm900298a
Keywords: Editorial; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 4
DOI: 10.1021/cm900298a
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“Solving the structure of Li ion battery materials with precession electron diffraction : application to Li2CoPo4F”. Hadermann J, Abakumov AM, Turner S, Hafideddine Z, Khasanova NR, Antipov EV, Van Tendeloo G, Chemistry of materials 23, 3540 (2011). http://doi.org/10.1021/cm201257b
Abstract: The crystal structure of the Li2CoPO4F high-voltage cathode for Li ion rechargeable batteries has been completely solved from precession electron diffraction (PED) data, including the location of the Li atoms. The crystal structure consists of infinite chains of CoO4F2 octahedra sharing common edges and linked into a 3D framework by PO4 tetrahedra. The chains and phosphate anions together delimit tunnels filled with the Li atoms. This investigation demonstrates that PED can be successfully applied for obtaining structural information on a variety of Li-containing electrode materials even from single micrometer-sized crystallites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 46
DOI: 10.1021/cm201257b
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“Coupled cation and charge ordering in the CaMn306 tunnel structure”. Hadermann J, Abakumov AM, Gillie LJ, Martin C, Hervieu M, Chemistry of materials 18, 5530 (2006). http://doi.org/10.1021/cm0618998
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 33
DOI: 10.1021/cm0618998
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“Crystal structure of a lightweight borohydride from submicrometer crystallites by precession electron diffraction”. Hadermann J, Abakumov A, Van Rompaey S, Perkisas T, Filinchuk Y, Van Tendeloo G, Chemistry of materials 24, 3401 (2012). http://doi.org/10.1021/cm301548k
Abstract: We demonstrate that precession electron diffraction at low-dose conditions can be successfully applied for structure analysis of extremely electron-beam-sensitive materials. Using LiBH4 as a test material, complete structural information, including the location of the H atoms, was obtained from submicrometer-sized crystallites. This demonstrates for the first time that, where conventional transmission electron microscopy techniques fail, quantitative precession electron diffraction can provide structural information from submicrometer particles of such extremely electron-beam-sensitive materials as complex lightweight hydrides. We expect the precession electron diffraction technique to be a useful tool for nanoscale investigations of thermally unstable lightweight hydrogen-storage materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 17
DOI: 10.1021/cm301548k
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“Chemical activity of the peroxide/oxide redox couple : case study of Ba5Ru2O11 in aqueous and organic solvents”. Grimaud A, Iadecola A, Batuk D, Saubanere M, Abakumov AM, Freeland JW, Cabana J, Li H, Doublet M-L, Rousse G, Tarascon J-M, Chemistry of materials 30, 3882 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B01372
Abstract: The finding that triggering the redox activity of oxygen ions within the lattice of transition metal oxides can boost the performances of materials used in energy storage and conversion devices such as Li-ion batteries or oxygen evolution electrocatalysts has recently spurred intensive and innovative research in the field of energy. While experimental and theoretical efforts have been critical in understanding the role of oxygen nonbonding states in the redox activity of oxygen ions, a clear picture of the redox chemistry of the oxygen species formed upon this oxidation process is still missing. This can be, in part, explained by the complexity in stabilizing and studying these species once electrochemically formed. In this work, we alleviate this difficulty by studying the phase Ba5Ru2O11, which contains peroxide O-2(2-) groups, as oxygen evolution reaction electrocatalyst and Li-ion battery material. Combining physical characterization and electrochemical measurements, we demonstrate that peroxide groups can easily be oxidized at relatively low potential, leading to the formation of gaseous dioxygen and to the instability of the oxide. Furthermore, we demonstrate that, owing to the stabilization at high energy of peroxide, the high-lying energy of the empty sigma* antibonding O-O states limits the reversibility of the electrochemical reactions when the O-2(2-)/O2- redox couple is used as redox center for Li-ion battery materials or as OER redox active sites. Overall, this work suggests that the formation of true peroxide O-2(2-) states are detrimental for transition metal oxides used as OER catalysts and Li-ion battery materials. Rather, oxygen species with O-O bond order lower than 1 would be preferred for these applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 2
DOI: 10.1021/ACS.CHEMMATER.8B01372
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“Sn2-2xSbxFexO4 solid solutions as possible inert anode materials in aluminum electrolysis”. Govorov VA, Abakumov AM, Rozova MG, Borzenko AG, Vassiliev SY, Mazin VM, Afanasov MI, Fabritchnyi PB, Tsirlina GA, Antipov EV, Morozova EN, Gippius AA, Ivanov VV, Van Tendeloo G, Chemistry of materials 17, 3004 (2005). http://doi.org/10.1021/cm048145i
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 11
DOI: 10.1021/cm048145i
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“Oxygen vacancy ordering in the double-layered Ruddlesden-Popper cobaltite Sm2BaCo2O7-\delta”. Gillie LJ, Hadermann J, Hervieu M, Maignan A, Martin C, Chemistry of materials 20, 6231 (2008). http://doi.org/10.1021/cm8010138
Abstract: A new oxygen-deficient Ruddlesden−Popper (RP) cobaltite Sm2BaCo2O7−δ (δ ≈ 1.0) has been synthesized and the crystal structure elucidated by Rietveld analysis of X-ray powder diffraction (XRD) data and transmission electron microscopy (TEM). The phase crystallizes in a primitive orthorhombic unit cell, with lattice parameters a = 5.4371(4) Å; b = 5.4405(4) Å and c = 19.8629(6) Å, and space group Pnnm. Contrary to other oxygen-deficient cobalt RP phases, the oxygen vacancies are located in the equatorial positions of the [CoO] layers to give an intralayer structure similar to Sr2Mn2O5, which is not usually observed for cobalt-containing materials. The Sm3+ and Ba2+ cations show a strong preference for distinct sites, with the majority of the larger Ba2+ cations situated in the perovskite block layers and Sm3+ cations predominantly in the rock salt layers. Magnetic susceptibility data demonstrate the strong antiferromagnetic (AFM) character of Sm2BaCo2O7−δ.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 7
DOI: 10.1021/cm8010138
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“Off-stoichiometry effects on the crystalline and defect structure of hexagonal manganite REMnO3 films (RE = Y, Er, Dy)”. Gélard J, Jehanathan N, Roussel H, Gariglio S, Lebedev OI, Van Tendeloo G, Dubourdieu C, Chemistry of materials 23, 1232 (2011). http://doi.org/10.1021/cm1029358
Abstract: The crystalline and defect structure of epitaxial hexagonal RExMnyO3 (RE = Er, Dy) films with varying cationic composition was investigated by X-ray diffraction and transmission electron microscopy. The films are composed of a strained layer at the interface with the substrate and of a relaxed layer on top of it. The critical thickness is of 10 to 25 nm. For Mn-rich films (or RE deficient), an off-stoichiometric composition maintaining the hexagonal LuMnO3-type structure is stabilized over a large range of the RE/Mn ratio (0.72−1.00), with no Mn-rich secondary phases observed. A linear dependence of the out-of-plane lattice parameter with RE/Mn is observed in this range. Out-of-phase boundary (OPB) extended defects are observed in all films and exhibit a local change in stoichiometry. Such a large solubility limit in the RE deficient region points toward the formation of vacancies on the RE site (RExMnO3−δ, with 0.72 ≤ x < 1), a phenomenon that is encountered in perovskite manganites such as LaxMnO3−δ (x < 1) and that may strongly impact the physical properties of hexagonal manganites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 17
DOI: 10.1021/cm1029358
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“_Fe2O3 nanoparticles with mesoporous MCM-48 silica: in situ formation and characterisation”. Fröba M, Köhn R, Bouffaud G, Richard O, Van Tendeloo G, Chemistry of materials 11, 2858 (1999). http://doi.org/10.1021/cm991048i
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 202
DOI: 10.1021/cm991048i
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“Synthesis and structure of Bi14O20(SO4), a new bismuth oxide sulfate”. Francesconi MG, Kirbyshire AL, Greaves C, Richard O, Van Tendeloo G, Chem. mater. 10, 626 (1998). http://doi.org/10.1021/cm9706255
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 30
DOI: 10.1021/cm9706255
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“Antiferromagnetic order breaks inversion symmetry in a metallic double perovskite, Pb₂NiOsO₆”. Feng HL, Kang C-J, Manuel P, Orlandi F, Su Y, Chen J, Tsujimoto Y, Hadermann J, Kotliar G, Yamaura K, McCabe EE, Greenblatt M, Chemistry Of Materials 33, 4188 (2021). http://doi.org/10.1021/ACS.CHEMMATER.1C01032
Abstract: A polycrystalline sample of Pb2NiOsO6 was synthesized under high-pressure (6 GPa) and high-temperature (1575 K) conditions. Pb2NiOsO6 crystallizes in a monoclinic double perovskite structure with a centrosymmetric space group P2(1)/n at room temperature. Pb2NiOsO6 is metallic down to 2 K and shows a single antiferromagnetic (AFM) transition at T-N = 58 K. Pb2NiOsO6 is a new example of a metallic and AFM oxide with three-dimensional connectivity. Neutron powder diffraction and first-principles calculation studies indicate that both Ni and Os moments are ordered below T-N and the AFM magnetic order breaks inversion symmetry. This loss of inversion symmetry driven by AFM order is unusual in metallic systems, and the 3d-Sd double-perovskite oxides represent a new class of noncentrosymmetric AFM metallic oxides.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
DOI: 10.1021/ACS.CHEMMATER.1C01032
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“AVPO4F (A = Li, K): A 4 V Cathode Material for High-Power Rechargeable Batteries”. Fedotov SS, Khasanova NR, Samarin AS, Drozhzhin OA, Batuk D, Karakulina OM, Hadermann J, Abakumov AM, Antipov EV, Chemistry of materials 28, 411 (2016). http://doi.org/10.1021/acs.chemmater.5b04065
Abstract: A novel potassium-based fluoride-phosphate, KVPO4F, with a KTiOPO4 (KTP) type structure is synthesized and characterized. About 85% of potassium has been electrochemically extracted on oxidation producing a cathode material with attractive performance for Li-ion batteries. The material operates at the electrode potential near 4V vs Li/Li+ exhibiting a sloping voltage profile, extremely low polarization, small volume change of about 2% and excellent rate capability, maintaining more than 75% of the initial capacity at 40C discharge rate without significant fading.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 46
DOI: 10.1021/acs.chemmater.5b04065
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“Au@ZIFs: stabilization and encapsulation of cavity-size matching gold clusters inside functionalized Zeolite Imidazolate Frameworks, ZIFs”. Esken D, Turner S, Lebedev OI, Van Tendeloo G, Fischer RA, Chemistry of materials 22, 6393 (2010). http://doi.org/10.1021/cm102529c
Abstract: The selective formation and stabilization of very small, naked metal particles inside the cavities of metal organic frameworks (MOFs) and the simultaneous realization of an even distribution of the particles throughout the crystalline MOF host matrix over a wide range of metal loading are challenging goals. MOFs reveal high specific surface areas, tunable pore sizes, and organic linkers, which are able to interact with guests. The chemically very robust zeolite imidazolate frameworks (ZIFs) are a subclass of MOFs. We chose the microporous sodalite-like ZIF-8 (Zn(MelM)(2); IM = imidazolate) and ZIF-90 (Zn(ICA)(2); ICA = imidazolate-2-carboxyaldehyde) as host matrices to influence the dispersion of imbedded gold nanoparticles (Au NPs). The metal loading was achieved via gas phase infiltration of [Au(CO)Cl] followed by a thermal hydrogenation step to form the Au NPs. Low-dose high-resolution transmission electron microscopy ((HR)TEM) and electron tomography reveal a homogeneous distribution of Au NPs throughout the ZIF matrix. The functional groups of ZIF-90 direct the anchoring of intermediate Au species and stabilize drastically smaller and quite monodisperse Au NPs in contrast to the parent not functionalized ZIF-8. The particles can be very small, match the cavity size and approach defined molecular clusters of magic numbers, i.e., Au(55), independently from the level of loading. Post-synthetic oxidation of the aldehyde groups to yield alkyl esters by the adjacent, catalytically active metal NPs is presented as a new concept of encapsulating nanoparticles inside MOFs and allows multiple steps of metal loadings without decomposition of the MOF.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 194
DOI: 10.1021/cm102529c
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“Transmission electron microscopy study of BA0.5Sr0.5CO0.8Fe0.2O3-\delta Perovskite decomposition at intermediate temperatures”. Efimov K, Xu Q, Feldhoff A, Chemistry of materials 22, 5866 (2010). http://doi.org/10.1021/cm101745v
Abstract: The cubic perovskite Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta) (denoted BSCF) is the state-of-the-art ceramic membrane material used for oxygen separation technologies above 1150 K. BSCF is a mixed oxygen-ion and electron conductor (MIEC) and exhibits one of the highest oxygen permeabilities reported so far for dense oxides. Additionally, it has excellent phase stability above 1150 K. In the intermediate temperature range (750-1100 K), however, BSCF suffers from a slow decomposition of the cubic perovskite into variants with hexagonal stacking that are barriers to oxygen transport. To elucidate details of the decomposition process, both sintered BSCF ceramic and powder were annealed for 180-240 h in ambient air at temperatures below 1123 K and analyzed by different transmission electron microscopy techniques. Aside from hexagonal perovskite Ba(0.5)Sr(0.5)CoO(3-delta) , the formation of lamellar noncubic phases was observed in the quenched samples. The structure of the lamellae with the previously unknown composition Ba(1-x)Sr(x)Co(2-y)Fe(y)O(5-delta) was found to be related to the 15R hexagonal perovskite polytype. The valence and spin-state transition of cobalt leading to a considerable diminution of its ionic radius can be considered a reason for BSCF's inherent phase instability at intermediate temperatures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 117
DOI: 10.1021/cm101745v
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“Theoretical investigation of grain size tuning during prolonged bias-enhanced nucleation”. Eckert M, Mortet V, Zhang L, Neyts E, Verbeeck J, Haenen ken, Bogaerts A, Chemistry of materials 23, 1414 (2011). http://doi.org/10.1021/cm102481y
Abstract: In this paper, the effects of prolonged bias-enhanced nucleation (prolonged BEN) on the growth mechanisms of diamond are investigated by molecular dynamics (MD) and combined MD-Metropolis Monte Carlo (MD-MMC) simulations. First, cumulative impacts of CxHy+ and Hx+ on an a-C:H/nanodiamond composite were simulated; second, nonconsecutive impacts of the dominant ions were simulated in order to understand the observed phenomena in more detail. As stated in the existing literature, the growth of diamond structures during prolonged BEN is a process that takes place below the surface of the growing film. The investigation of the penetration behavior of CxHy+ and Hx+ species shows that the carbon-containing ions remain trapped within this amorphous phase where they dominate mechanisms like precipitation of sp3 carbon clusters. The H+ ions, however, penetrate into the crystalline phase at high bias voltages (>100 V), destroying the perfect diamond structure. The experimentally measured reduction of grain sizes at high bias voltage, reported in the literature, might thus be related to penetrating H+ ions. Furthermore, the CxHy+ ions are found to be the most efficient sputtering agents, preventing the build up of defective material.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 9.466
Times cited: 9
DOI: 10.1021/cm102481y
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“Structures and magnetism of La1-xSrxMnO3-(0.5+x)/2 (0.67\leq x\leq1) phases”. Dixon E, Hadermann J, Hayward MA, Chemistry of materials 24, 1486 (2012). http://doi.org/10.1021/cm300199b
Abstract: Topotactic reduction of La1-xSrxMnO3 (0.67 <= x <= 1) phases with sodium hydride yields a series of isoelectronic materials of composition La1-xSrxMnO3-(0.5+x)/2. Lanthanum rich members of the series (0.67 <= x <= 0.83) adopt anion deficient perovskite structures with a 6-layer -OTOOT'O- stacking sequence of sheets of octahedra/square-based pyramids (O) and sheets of tetrahedra (T). The strontium rich members of the series (0.83 <= x <= 1) incorporate “step defects” into this 6-layer structure in which the OTOOT'O stacking sequence is converted into either OOTOOT' or TOOT'OO at a defect plane which runs perpendicular to the [201] lattice plane. The step defects appear to provide a mechanism to relieve lattice strain and accommodate additional anion deficiency in phases with x > 0.83. Magnetization and neutron diffraction data indicate La1-xSrxMnO3-(0.5+x)/2 phases adopt antiferromagnetically ordered states at low-temperature in which the ordered arrangement of magnetic spins is incommensurate with the crystallographic lattice.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 13
DOI: 10.1021/cm300199b
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“Tuning the pore size of ink-bottle mesopores by atomic layer deposition”. Dendooven J, Goris B, Devloo-Casier K, Levrau E, Biermans E, Baklanov MR, Ludwig KF, van der Voort P, Bals S, Detavernier C, Chemistry of materials 24, 1992 (2012). http://doi.org/10.1021/cm203754a
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 52
DOI: 10.1021/cm203754a
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“Reduced Na2+xTi4O9 composite : a durable anode for sodium-ion batteries”. De Sloovere D, Safari M, Elen K, D'Haen J, Drozhzhin OA, Abakumov AM, Simenas M, Banys J, Bekaert J, Partoens B, Van Bael MK, Hardy A, Chemistry of materials 30, 8521 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B03301
Abstract: Sodium-ion batteries (SIBs) are potential cost-effective solutions for stationary energy storage applications. Unavailability of suitable anode materials, however, is one of the important barriers to the maturity of SIBs. Here, we report a Na2+xTi4O9/C composite as a promising anode candidate for SIBs with high capacity and cycling stability. This anode is characterized by a capacity of 124 mAh g(-1) (plus 11 mAh g(-1) contributed by carbon black), an average discharge potential of 0.9 V vs Na/Na+, a good rate capability and a high stability (89% capacity retention after 250 cycles at a rate of 1 degrees C). The mechanisms of sodium insertion/deinsertion and of the formation of Na2+xTi4O9/C are investigated with the aid of various ex/in situ characterization techniques. The in situ formed carbon is necessary for the formation of the reduced sodium titanate. This synthesis method may enable the convenient synthesis of other composites of crystalline phases with amorphous carbon.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 9.466
Times cited: 7
DOI: 10.1021/ACS.CHEMMATER.8B03301
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“Short-range layered A-site ordering in double perovskites NaLaBB'O6 (B = Mn, Fe, B' = Nb, Ta)”. Dachraoui W, Yang T, Liu C, Ling G, Hadermann J, Van Tendeloo G, Llobet A, Greenblatt M, Chemistry of materials 23, 2398 (2011). http://doi.org/10.1021/cm200226u
Abstract: The new compounds NaLaFeTaO6, NaLaFeNbO6, NaLaMnTaO6, and NaLaMnNbO6 have been synthesized and characterized with a combination of transmission electron microscopy, X-ray powder diffraction (XRPD), neutron powder diffraction (NPD), and magnetization measurements. Through electron microscopy study, a local layered order of the A-cations has been detected without the typical occurrence of rock salt order at the B-cation site. Satellite reflections in the electron diffraction related to the local layered order are not visible on the XRPD or NPD patterns. The occurrence of local layered order is supported by pair distribution function analysis, which also reveals the presence of uncorrelated displacements of the Nb and Ta cations. The octahedra are tilted according to the system a−b+a−, and the coordinates were refined from XRPD and NPD with a disordered cation distribution in the space group Pnma. The magnetic exchange interactions in NaLaFeTaO6 and NaLaFeNbO6 are antiferromagnetic, while they are ferromagnetic in NaLaMnTaO6 and NaLaMnNbO6. Long-range magnetic ordering is not observed down to 4 K for any of the compositions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 14
DOI: 10.1021/cm200226u
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“Local oxygen-vacancy ordering and twinned octahedral tilting pattern in the Bi0.81Pb0.19FeO2.905 cubic perovskite”. Dachraoui W, Hadermann J, Abakumov AM, Tsirlin AA, Batuk D, Glazyrin K, McCammon C, Dubrovinsky L, Van Tendeloo G, Chemistry of materials 24, 1378 (2012). http://doi.org/10.1021/cm300178x
Abstract: The structure of Bi0.81Pb0.19FeO2.905 was investigated on different length scales using a combination of electron diffraction, high-resolution scanning transmission electron microscopy, synchrotron X-ray powder diffraction, and Mössbauer spectroscopy. In the 80300 K temperature range, the average crystal structure of Bi0.81Pb0.19FeO2.905 is a cubic Pm3̅m perovskite with a = 3.95368(3) Å at T = 300 K. The (Pb2+, Bi3+) cations and O2 anions are randomly displaced along the 110 cubic directions, indicating the steric activity of the lone pair on the Pb2+ and Bi3+ cations and a tilting distortion of the perovskite framework. The charge imbalance induced by the heterovalent Bi3+ → Pb2+ substitution is compensated by the formation of oxygen vacancies preserving the trivalent state of the Fe cations. On a short scale, oxygen vacancies are located in anion-deficient (FeO1.25) layers that are approximately 6 perovskite unit cells apart and transform every sixth layer of the FeO6 octahedra into a layer with a 1:1 mixture of corner-sharing FeO4 tetrahedra and FeO5 tetragonal pyramids. The anion-deficient layers act as twin planes for the octahedral tilting pattern of adjacent perovskite blocks. They effectively randomize the octahedral tilting and prevent the cooperative distortion of the perovskite framework. The disorder in the anion sublattice impedes cooperative interactions of the local dipoles induced by the off-center displacements of the Pb and Bi cations. Magnetic susceptibility measurements evidence the antiferromagnetic ordering in Bi0.81Pb0.19FeO2.905 at low temperatures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 27
DOI: 10.1021/cm300178x
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“Tetrahedral chain order in the Sr2Fe2O5 brownmillerite”. d' Hondt H, Abakumov AM, Hadermann J, Kalyuzhnaya AS, Rozova MG, Antipov EV, Van Tendeloo G, Chemistry of materials 20, 7188 (2008). http://doi.org/10.1021/cm801723b
Abstract: The crystal structure of the Sr2Fe2O5 brownmillerite has been investigated using electron diffraction and high resolution electron microscopy. The Sr2Fe2O5 structure demonstrates two-dimensional order: the tetrahedral chains with two mirror-related configurations (L and R) are arranged within the tetrahedral layers according to the −L−R−L−R− sequence, and the layers themselves are displaced with respect to each other over 1/2[111] or 1/2[11] vectors of the brownmillerite unit cell, resulting in different ordered stacking variants. A unified superspace model is constructed for ordered stacking sequences in brownmillerites based on the average brownmillerite structure with a = 5.5298(4)Å, b = 15.5875(12)Å, c = 5.6687(4)Å, and (3 + 1)-dimensional superspace group I2/m(0βγ)0s, q = βb* + γc*, 0 ≤ β ≤ 1/2, 0 ≤ γ ≤ 1.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 64
DOI: 10.1021/cm801723b
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