“Structure of artificial grain boundaries in sapphire bicrystals with intermediate layers”. Vasiliev AL, Stepantsov EA, Ivanov ZG, Olsson E, Verbist K, Van Tendeloo G, Interface science 5, 223 (1997)
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 3
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“The superconducting state in square mesoscopic samples with two and four antidots”. Berdiyorov GR, Baelus BJ, Milošević, MV, Peeters FM, Physica: C : superconductivity 404, 56 (2004). http://doi.org/10.1016/j.physc.2003.09.111
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.404
Times cited: 3
DOI: 10.1016/j.physc.2003.09.111
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“Superconductivity in mesoscopic high-Tc superconducting particles”. Ivanov VA, Misko VR, Fomin VM, Devreese JT, Solid State Communications 125, 439 (2003). http://doi.org/10.1016/S0038-1098(02)00757-3
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 1.554
Times cited: 3
DOI: 10.1016/S0038-1098(02)00757-3
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“Synthesis and characterisation of lanthanide-based dioxide”. Esquivel MR, Zelaya E, Advances in applied ceramics 110, 219 (2011). http://doi.org/10.1179/1743676110Y.0000000021
Abstract: In the present work, the microstructure and structure of La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)(OH)(3) and La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)O(2) is obtained from transmission electron microscopy and X-ray diffraction measurements. Space group P6(3)/m is assigned to the structure of La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)(OH)(3). Lanthanides are assigned to Wyckoff positions 2c. Cell parameters are a=6.375(5) angstrom and c=3.753(5) angstrom. The thermal decomposition of this compound was studied by differential scanning calorimetry. The process is exothermal with an enthalpy change Delta H degrees value of -254 +/- 10 kJ mol(-1). The decomposition kinetics is complex and two global processes with E(a) values of 98 +/- 4 and 61 +/- 2 kJ mol 21 were observed. The product is a lanthanide dioxide. Space group Fm3m is assigned to the La(0.25)Ce(0.52)Nd(0.17)Pr(0.06)O(2). Lanthanides are distributed in Wyckoff positions 4a. The cell parameter is a=5.479(5) angstrom. Nanopores in the oxide surface are obtained using this method and characterised by STEM measurements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.325
Times cited: 3
DOI: 10.1179/1743676110Y.0000000021
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“Synthesis and crystal structure of Sr2ScBiO6”. Kazin PE, Abakumov AM, Zaytsev DD, Tretyakov YD, Khasanova NR, Van Tendeloo G, Jansen M, Journal of solid state chemistry 162, 142 (2001). http://doi.org/10.1006/jssc.2001.9375
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 3
DOI: 10.1006/jssc.2001.9375
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“Synthesis and crystal structure of the novel Pb5Sb2MnO11 compound”. Abakumov AM, Rozova MG, Chizhov PS, Antipov EV, Hadermann J, Van Tendeloo G, Journal of solid state chemistry 177, 2855 (2004). http://doi.org/10.1016/j.jssc.2004.04.047
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 3
DOI: 10.1016/j.jssc.2004.04.047
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“Synthesis and structural mechanisms of the 2201-type ferrites and polytypes: Fe2(Sr2-xAx)FeO6.5-\delta/2 (A = Ba, La, Tl, Pb and Bi)”. Lepoittevin C, Malo S, Van Tendeloo G, Hervieu M, Solid state sciences 11, 595 (2009). http://doi.org/10.1016/j.solidstatesciences.2008.12.005
Abstract: The Fe2(Sr2 − xAx)FeO6.5 − ä/2 systems have been investigated, by doping the iron rich 2201-type parent structure with Ba2+, La3+ and 5d10 post-transition cations. The syntheses have been carried out up to the limit of the 2201-type solid solutions, in order to test the role of the double iron layer Fe2O2.5 − ä/2. The localisation of the charge carriers in these compounds is consistent with their strong antiferro-magnetism. The investigation was then carried out in the transition part of the diagram up to the formation of stable phases. The study of structural mechanisms was carried using high resolution electron microscopy (transmission and scanning transmission), electron diffraction and energy dispersive spectroscopy. Different non-stoichiometry mechanisms are observed, depending on the electronic structure and chemical properties of the doping elements. The specific behavior of the modulated double iron layer is discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.811
Times cited: 3
DOI: 10.1016/j.solidstatesciences.2008.12.005
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“Synthesis and structure determination of ferromagnetic semiconductors LaAMnSnO6(A = Sr, Ba)”. Yang T, Perkisas T, Hadermann J, Croft M, Ignatov A, Van Tendeloo G, Greenblatt M, Journal of materials chemistry 21, 199 (2011). http://doi.org/10.1039/c0jm02614j
Abstract: LaAMnSnO(6) (A = Sr, Ba) have been synthesized by high temperature solid-state reactions under dynamic 1% H(2)/Ar flow. Rietveld refinements on room temperature powder X-ray diffraction data indicate that LaSrMnSnO(6) crystallizes in the GdFeO(3)-structure, with space group Pnma and, combined with transmission electron microscopy, LaBaMnSnO(6) in Imma. Both space groups are common in disordered double-perovskites. The Mn(3+) and Sn(4+) ions whose valence states were confirmed by X-ray absorption spectroscopy, are completely disordered over the B-sites and the BO(6) octahedra are slightly distorted. LaAMnSnO(6) are ferromagnetic semiconductors with a T(C) = 83 K for the Sr- and 66 K for the Ba-compound. The title compounds, together with the previously reported LaCaMnSnO(6) provide an interesting example of progression from Pnma to Imma as the tolerance factor increases. An analysis of the relationship between space group and tolerance factor for the series LaAMnMO(6) (A = Ca, Sr, Ba; M = Sn, Ru) provides a better understanding of the symmetry determination for double perovskites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 3
DOI: 10.1039/c0jm02614j
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“Synthesis, structure and properties of layered bismuthates: (Ba,K)3Bi2O7 and (Ba,K)2BiO4”. Khasanova NR, Kovba ML, Putilin SN, Antipov EV, Lebedev OI, Van Tendeloo G, Solid state communications 122, 189 (2002). http://doi.org/10.1016/S0038-1098(02)00096-0
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.554
Times cited: 3
DOI: 10.1016/S0038-1098(02)00096-0
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“Temperature effect on the 002 structure factor of ternary Ga1-xInxAs crystals”. Titantah JT, Lamoen D, Schowalter M, Rosenauer A, Physical review : B : condensed matter and materials physics 76, 073303 (2007). http://doi.org/10.1103/PhysRevB.76.073303
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 3
DOI: 10.1103/PhysRevB.76.073303
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“A temperature study of mixed AgBr-AgBrI tabular crystals”. Goessens C, Schryvers D, van Landuyt J, Geuens I, Gijbels R, Jacob W, de Keyzer R Hawaii, page 70 (1995).
Keywords: H1 Book chapter; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 3
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“K2CaV2O7 : a pyrovanadate with a new layered type of structure in the A2BV2O7 family”. Tyutyunnik AP, Slobodin BV, Samigullina RF, Verberck B, Tarakina NV, Journal of the Chemical Society : Dalton transactions 42, 1057 (2013). http://doi.org/10.1039/c2dt31246h
Abstract: The crystal structure of K2CaV2O7 prepared by a conventional solid-state reaction has been solved by a direct method and refined using Rietveld full profile fitting based on X-ray powder diffraction data. This compound crystallises in the triclinic space group (P (1) over bar, Z = 2) with unit cell constants a = 7.1577(1) angstrom, b = 10.5104(2) angstrom, c = 5.8187(1) angstrom, alpha = 106.3368(9)degrees, beta = 106.235(1)degrees, gamma = 71.1375(9)degrees. The structure can be described as infinite undulating CaV2O72- layers parallel to the ac plane, which consist of pairs of edge-sharing CaO6 octahedra connected to each other through V2O7 pyrogroups. The potassium atoms are positioned in two sites between the layers, with a distorted IX-fold coordination of oxygen atoms. The chemical composition obtained from the structural solution was confirmed by energy-dispersive X-ray analysis. The stability of compounds in the family of alkali metal calcium pyrovanadates is discussed based on an analysis of the correlation between anion and cation sizes and theoretical first-principles calculations.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.029
Times cited: 3
DOI: 10.1039/c2dt31246h
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“YBa2Cu3O7-x Josephson junctions and dc SQUIDs based on 45\text{\textdegree} a-axis tilt and twist grain boundaries : atomically clean interfaces for applications”. Tafuri F, Carillo F, Lombardi F, Granozio FM, dii Uccio US, Testa G, Sarnelli E, Verbist K, Van Tendeloo G, Superconductor science and technology
T2 –, International Superconductive Electronics Conference, JUN 21-25, 1999, BERKELEY, CALIFORNIA 12, 1007 (1999). http://doi.org/10.1088/0953-2048/12/11/393
Abstract: YBa2Cu3O7-x artificial grain boundary Josephson junctions have been fabricated, employing a recently implemented biepitaxial technique. The grain boundaries can be obtained by controlling the orientation of the MgO seed layer and are characterized by a misalignment of the c-axes (45 degrees a-axis tilt or 45 degrees a-axis twist). These types of grain boundaries are still mostly unexplored. We carried out a complete characterization of their transport properties and microstructure. Junctions and de SQUIDs associated with these grain boundaries exhibit an excellent Josephson phenomenology and high values of the ICRN product and of the magnetic flux-to-voltage transfer parameter respectively. Remarkable differences in the transport parameters of tilt and twist junctions have been observed, which can be of interest for several applications. A maximum speed of Josephson vortices as calculated from the voltage step values of the order of 2 x 10(6) m s(-1) is obtained. These devices could also have some impact on experiments designed to study the symmetry of the order parameter, exploiting their microstructure and anisotropic properties. High-resolution electron microscopy showed the presence of perfect basal plane faced boundaries in the cross sections of tilt boundaries.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 3
DOI: 10.1088/0953-2048/12/11/393
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“The superconducting bismuth-based mixed oxides”. Antipov EV, Khasanova NR, Pshirkov JS, Putilin SN, Bougerof C, Lebedev OI, Van Tendeloo G, Baranov A, Park YW, Journal of low temperature physics
T2 –, International Conference on Physics and Chemistry of Molecular and Oxide, Superconductors (MOS2002), AUG 13-18, 2002, HSINCHU, TAIWAN 131, 575 (2003). http://doi.org/10.1023/A:1022923924607
Abstract: The present paper describes the synthesis, characterization of mixed-valence bismuthates with 3- or 2-dimensional perovskite-like structures and structural criteria that influence superconductivity in these compounds. Single-phase samples of Sr1-xKxBiO3 were prepared for the broad range of K-content: 0.25 less than or equal to x less than or equal to 0.65. For these bismuthates the symmetry of the structure changes from monoclinic to orthorhombic and finally to tetragonal upon increasing the K-content thus resulting in the decrease of the Bi-O distances and reduction of the network distortions. Superconductivity with maximum T-c = 12K exists in the narrow range (x approximate to 0.5 – 0.6) within the stability field of the tetragonal phase (0.33 less than or equal to x less than or equal to 0.65), when the 3-dimensional octahedral framework has close to the ideal perovskite structure arrangement. At the same time compositions with close to optimal Bi-valence (x = 0.33 and 0.43) do not show any sign of superconductivity, probably, due to structural distortions. The layered type (BaK)(3)Bi2O7 and (Ba,K)(2)BiO4 bismuthates belonging to the A(n+1)B(n)O(3n+1) homologous series were investigated Buckling of the (BiO2) layers in the structure of the n = 2 member was revealed The formation of the n=1 bismuthate was found by Electron Microscopy and X-ray powder diffraction studies. Both types of compounds are considered to be possible candidates for new superconducting materials among bismuthates.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.3
Times cited: 3
DOI: 10.1023/A:1022923924607
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“Theoretical investigation of CoSi2/Si1-xGex detectors: influence of a Si tunneling barrier on the electro-optical characteristics”. Chu DP, Peeters FM, Kolodinski S, Roca E, Journal of applied physics 79, 1151 (1996)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.183
Times cited: 3
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“Transmission electron microscopy study of low-hysteresis shape memory alloys”. Delville R, James RD, Salman U, Finel A, Schryvers D, , 02005 (2009). http://doi.org/10.1051/esomat/200902005
Abstract: Recent findings have linked low hysteresis in shape memory alloys with phase compatibility between austenite and martensite. In order to investigate the evolution of microstructure as the phase compatibility increases and the hysteresis is reduced, transmission electron microscopy was used to study the alloy system Ti50Ni50-xPdx where the composition is systemically tuned to approach perfect compatibility. Changes in morphology, twinning density and twinning modes are reported along with special microstructures occurring when the compatibility is achieved. In addition, the interface between austenite and a single variant of martensite was studied by high-resolution and conventional electron microscopy. The atomically sharp, defect free, low energy configuration of the interface suggests that it plays an important role in the lowering of hysteresis. Finally, dynamical modeling of the martensitic transformation using the phase-field micro-elasticity model within the geometrically linear theory succeeded in reproducing the change in microstructure as the compatibility condition is satisfied. Latest results on the extension of these findings in other Ni-Ti based ternary/quaternary systems are also reported.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 3
DOI: 10.1051/esomat/200902005
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“Transmission electron microscopy study of microstructural evolution in nanograined Ni-Ti microwires heat treated by electric pulse”. Delville R, Malard B, Pilch J, Sittner P, Schryvers D, Diffusion and defect data : solid state data : part B : solid state phenomena 172/174, 682 (2011). http://doi.org/10.4028/www.scientific.net/SSP.172-174.682
Abstract: Transmission electron microscopy and mechanical testing were employed to investigate the evolution of microstructure and functional superelastic properties of 0.1mm diameter as-drawn Ni-Ti wires subjected to a non-conventional heat treatment by controlled electric pulse current. This method enables a finer control of the recovery and recrystallisation processes taking place during the heat treatment and accordingly a better control on the final microstructure. The best functional properties were obtained for heat-treated Ni-Ti wires having a nanograined microstructure (20-50 nm) partially recovered through polygonization and partially recrystallized. Such microstructure is highly resistant against dislocation slip upon cycling, while microstructures annealed for longer time and showing mostly recrystallized grains were prone to dislocation slip, particularly as the grain size exceeds 100 nm. The density of dislocation defects increased significantly with increasing grain size of the microstructure. The activity of three <100>/{011} slip systems was identified in the largest grains of 500-1200 nm. An additional mode of plastic deformation, {114} compound austenite twinning, was observed in the largest grains of fully recrystallized microstructures. It is proposed that dislocation slip (and possibly deformation twinning) occurring in superelastic cycling is coupled with the stress-induced martensitic transformation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 3
DOI: 10.4028/www.scientific.net/SSP.172-174.682
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“Tunable exciton Aharonov-Bohm effect in a quantum ring”. Li B, Magnus W, Peeters FM, Journal of physics : conference series
T2 –, Proceedings of the 11th International Conference on Optics of Excitons in Confined Systems, September 7-11, 2009, Spain / Vina, L. [edit.], et al. [edit.] 210, 012030 (2010). http://doi.org/10.1088/1742-6596/210/1/012030
Abstract: We studied the optical Aharonov-Bohm effect for an exciton in a semiconductor quantum ring. A perpendicular electric field applied to a quantum ring with large height, is able to tune the exciton ground state energy such that it exhibits a weak observable Aharonov-Bohm oscillations. This Aharonov-Bohm effect is tunable in strength and period.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 3
DOI: 10.1088/1742-6596/210/1/012030
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“Unconventional dynamics of vortex shells in mesoscopic superconducting corbino disks”. Misko VR, Lin NS, Peeters FM, Physica: C : superconductivity 470, 939 (2010). http://doi.org/10.1016/j.physc.2010.02.058
Abstract: The dynamics of vortex matter in mesoscopic superconducting Corbino disk is strongly influenced by the discrete vortex structure arranged in shells. While in previous works the vortex dynamics has been studied in large (macroscopic) and in very small mesoscopic disks (containing only few shells), in the intermediate-size regime it is much more complex and unusual, due to: (i) the competition between the vortexvortex interaction and confinement and (ii) (in)commensurability among the vortex shells. We found that the interplay between these effects can result in a very unusual vortex dynamical behavior: (i) unconventional angular melting (i.e., propagating from the boundary, where the shear stress is minimum, towards the center) and (ii) unconventional dynamics of shells (i.e., the inversion of shell velocities with respect to the gradient driving force). This unusual behavior is found for different number of shells.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.404
Times cited: 3
DOI: 10.1016/j.physc.2010.02.058
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“The vortex-magnetic dipole interaction in the London approximation”. Milošević, MV, Yampolskii SV, Peeters FM, Journal of low temperature physics 130, 321 (2003). http://doi.org/10.1023/A:1022200504151
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.3
Times cited: 3
DOI: 10.1023/A:1022200504151
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“Vortex matter in the presence of magnetic pinning centra”. Milošević, MV, Peeters FM, Journal of low temperature physics 130, 311 (2003). http://doi.org/10.1023/A:1022248420080
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.3
Times cited: 3
DOI: 10.1023/A:1022248420080
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“Warm-electron transport in a two-dimensional semiconductor”. Xu W, Peeters FM, Devreese JT, Semiconductor science and technology 7, 1251 (1992)
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Impact Factor: 2.19
Times cited: 3
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“Selective Plasma Oxidation of Ultrasmall Si Nanowires”. Khalilov U, Yusupov M, Bogaerts A, Neyts EC, The journal of physical chemistry: C : nanomaterials and interfaces 120, 472 (2016). http://doi.org/10.1021/acs.jpcc.5b11027
Abstract: Device performance of Si|SiOx core-shell based nanowires critically depends on the exact control over the oxide thickness. Low-temperature plasma oxidation is a highly promising alternative to thermal oxidation allowing for improved control over the oxidation process, in particular for ultrasmall Si nanowires. We here elucidate the room temperature plasma oxidation mechanisms of ultrasmall Si nanowires using hybrid molecular dynamics / force-bias Monte Carlo simulations. We demonstrate how the oxidation and concurrent water formation mechanisms are a function of the oxidizing plasma species and we demonstrate how the resulting core-shell oxide thickness can be controlled through these species. A new mechanism of water formation is discussed in detail. The results provide a detailed atomic level explanation of the oxidation process of highly curved Si surfaces. These results point out a route toward plasma-based formation of ultrathin core-shell Si|SiOx nanowires at room temperature.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 3
DOI: 10.1021/acs.jpcc.5b11027
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“Characterization of the size and position of electron-hole puddles at a graphene p-n junction”. Milovanovic SP, Peeters FM, Nanotechnology 27, 105203 (2016). http://doi.org/10.1088/0957-4484/27/10/105203
Abstract: The effect of an electron-hole puddle on the electrical transport when governed by snake states in a bipolar graphene structure is investigated. Using numerical simulations we show that information on the size and position of the electron-hole puddle can be obtained using the dependence of the conductance on magnetic field and electron density of the gated region. The presence of the scatterer disrupts snake state transport which alters the conduction pattern. We obtain a simple analytical formula that connects the position of the electron-hole puddle with features observed in the conductance. The size of the electron-hole puddle is estimated from the magnetic field and gate potential that maximizes the effect of the puddle on the electrical transport.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 3.44
Times cited: 3
DOI: 10.1088/0957-4484/27/10/105203
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“Ab-initio study of the segregation and electronic properties of neutral and charged B and P dopants in Si and Si/SiO2 nanowires”. Schoeters B, Leenaerts O, Pourtois G, Partoens B, Journal of applied physics 118, 104306 (2015). http://doi.org/10.1063/1.4930048
Abstract: We perform first-principles calculations to investigate the preferred positions of B and P dopants, both neutral and in their preferred charge state, in Si and Si/SiO2 core-shell nanowires (NWs). In order to understand the observed trends in the formation energy, we isolate the different effects that determine these formation energies. By making the distinction between the unrelaxed and the relaxed formation energy, we separate the impact of the relaxation from that of the chemical environment. The unrelaxed formation energies are determined by three effects: (i) the effect of strain caused by size mismatch between the dopant and the host atoms, (ii) the local position of the band edges, and (iii) a screening effect. In the case of the SiNW (Si/SiO2 NW), these effects result in an increase of the formation energy away from the center (interface). The effect of relaxation depends on the relative size mismatch between the dopant and host atoms. A large size mismatch causes substantial relaxation that reduces the formation energy considerably, with the relaxation being more pronounced towards the edge of the wires. These effects explain the surface segregation of the B dopants in a SiNW, since the atomic relaxation induces a continuous drop of the formation energy towards the edge. However, for the P dopants, the formation energy starts to rise when moving from the center but drops to a minimum just next to the surface, indicating a different type of behavior. It also explains that the preferential location for B dopants in Si/SiO2 core-shell NWs is inside the oxide shell just next to the interface, whereas the P dopants prefer the positions next to the interface inside the Si core, which is in agreement with recent experiments. These preferred locations have an important impact on the electronic properties of these core-shell NWs. Our simulations indicate the possibility of hole gas formation when B segregates into the oxide shell.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 3
DOI: 10.1063/1.4930048
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“Microstructure and phase composition characterization in a Co38Ni33Al29 ferromagnetic shape memory alloy”. Lu JB, Schryvers D, Materials characterization 118, 9 (2016). http://doi.org/10.1016/j.matchar.2016.04.028
Abstract: Transmission electron microscopy was performed to investigate the microstructures of a secondary phase and its surrounding matrix in a Co38Ni33Al29 ferromagnetic shape memory alloy. The secondary phase shows a γ′ L12 structure exhibiting a dendritic morphology with enclosed B2 austenite regions while the matrix shows the L10 martensitic structure. A secondary phase-austenite-martensite sandwich structure with residual austenite ranging from several hundred nanometers to several micrometers wide is observed at the secondary phase-martensite interface due to the depletion of Co and enrichment of Al in the chemical gradient zone and the effect of the strong martensitic start temperature dependency of the element concentrations. The crystallographic orientation relationship of the secondary phase and the B2 austenite fits the Kurdjumov-Sachs relationship.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
Times cited: 3
DOI: 10.1016/j.matchar.2016.04.028
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“Bi(3n+1)Ti7Fe(3n-3)O(9n+11) Homologous Series: Slicing Perovskite Structure with Planar Interfaces Containing Anatase-like Chains”. Batuk D, Tsirlin AA, Filimonov DS, Zakharov KV, Volkova OS, Vasiliev A, Hadermann J, Abakumov AM, Inorganic chemistry 55, 1245 (2016). http://doi.org/10.1021/acs.inorgchem.5b02465
Abstract: The n = 3-6 members of a new perovskite-based homologous series Bi(3n+1)Ti7Fe(3n-3)O(9n+11) are reported. The crystal structure of the n = 3 Bi10Ti7Fe6O38 member is refined using a combination of X-ray and neutron powder diffraction data (a = 11.8511(2) A, b = 3.85076(4) A, c = 33.0722(6) A, S.G. Immm), unveiling the partially ordered distribution of Ti(4+) and Fe(3+) cations and indicating the presence of static random displacements of the Bi and O atoms. All Bi(3n+1)Ti7Fe(3n-3)O(9n+11) structures are composed of perovskite blocks separated by translational interfaces parallel to the (001)p perovskite planes. The thickness of the perovskite blocks increases with n, while the atomic arrangement at the interfaces remains the same. The interfaces comprise chains of double edge-sharing (Fe,Ti)O6 octahedra connected to the octahedra of the perovskite blocks by sharing edges and corners. This configuration shifts the adjacent perovskite blocks relative to each other over a vector (1/2)[110]p and creates S-shaped tunnels along the [010] direction. The tunnels accommodate double columns of the Bi(3+) cations, which stabilize the interfaces owing to the stereochemical activity of their lone electron pairs. The Bi(3n+1)Ti7Fe(3n-3)O(9n+11) structures can be formally considered either as intergrowths of perovskite modules and polysynthetically twinned modules of the Bi2Ti4O11 structure or as intergrowths of the 2D perovskite and 1D anatase fragments. Transmission electron microscopy (TEM) on Bi10Ti7Fe6O38 reveals that static atomic displacements of Bi and O inside the perovskite blocks are not completely random; they are cooperative, yet only short-range ordered. According to TEM, the interfaces can be laterally shifted with respect to each other over +/-1/3a, introducing an additional degree of disorder. Bi10Ti7Fe6O38 is paramagnetic in the 1.5-1000 K temperature range due to dilution of the magnetic Fe(3+) cations with nonmagnetic Ti(4+). The n = 3, 4 compounds demonstrate a high dielectric constant of 70-165 at room temperature.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 3
DOI: 10.1021/acs.inorgchem.5b02465
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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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“Measuring the height-to-height correlation function of corrugation in suspended graphene”. Kirilenko DA, Brunkov PN, Ultramicroscopy 165, 1 (2016). http://doi.org/10.1016/j.ultramic.2016.03.010
Abstract: Nanocorrugation of 2D crystals is an important phenomenon since it affects their electronic and mechanical properties. The corrugation may have various sources; one of them is flexural phonons that, in particular, are responsible for the thermal conductivity of graphene. A study of corrugation of just the suspended graphene can reveal much of valuable information on the physics of this complicated phenomenon. At the same time, the suspended crystal nanorelief can hardly be measured directly because of high flexibility of the 2D crystal. Moreover, the relief portion related to rapid out-of-plane oscillations (flexural phonons) is also inaccessible by such measurements. Here we present a technique for measuring the Fourier components of the height-height correlation function H(q) of suspended graphene which includes the effect of flexural phonons. The technique is based on the analysis of electron diffraction patterns. The H(q) is measured in the range of wavevectors q approximately 0.4-4.5nm(-1). At the upper limit of this range H(q) does follow the T/kappaq(4) law. So, we measured the value of suspended graphene bending rigidity kappa=1.2+/-0.4eV at ambient temperature T approximately 300K. At intermediate wave vectors, H(q) follows a slightly weaker exponent than theoretically predicted q(-3.15) but is closer to the results of the molecular dynamics simulation. At low wave vectors, the dependence becomes even weaker, which may be a sign of influence of charge carriers on the dynamics of undulations longer than 10nm. The technique presented can be used for studying physics of flexural phonons in other 2D materials.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 2.843
Times cited: 3
DOI: 10.1016/j.ultramic.2016.03.010
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“Effective ionisation coefficients and critical breakdown electric field of CO2at elevated temperature: effect of excited states and ion kinetics”. Wang W, Bogaerts A, Plasma sources science and technology 25, 055025 (2016). http://doi.org/10.1088/0963-0252/25/5/055025
Abstract: Electrical breakdown by the application of an electric field occurs more easily in hot gases than in cold gases because of the extra electron-species interactions that occur as a result of dissociation, ionization and excitation at higher temperature. This paper discusses some overlooked physics and clarifies inaccuracies in the evaluation of the effective ionization coefficients and the critical reduced breakdown electric field of CO2 at elevated temperature, considering the influence of excited states and ion kinetics. The critical reduced breakdown electric field is obtained by balancing electron generation and loss mechanisms using the electron energy distribution function (EEDF) derived from the Boltzmann transport equation under the two-term approximation. The equilibrium compositions of the hot gas mixtures are determined based on Gibbs free energy minimization considering the ground states as well as vibrationally and electronically excited states as independent species, which follow a Boltzmann distribution with a fixed excitation temperature. The interaction cross sections between electrons and the excited species, not reported previously, are properly taken into account. Furthermore, the ion kinetics, including electron–ion recombination, associative electron detachment, charge transfer and ion conversion into stable negative ion clusters, are also considered. Our results indicate that the excited species lead to a greater population of high-energy electrons at higher gas temperature and this affects the Townsend rate coefficients (i.e. of electron impact ionization and attachment), but the critical reduced breakdown electric field strength of CO2 is only affected when also properly accounting for the ion kinetics. Indeed, the latter greatly influences the effective ionization coefficients and hence the critical reduced breakdown electric field at temperatures above 1500 K. The rapid increase of the dissociative electron attachment cross-section of molecular oxygen with rising vibrational quantum number leads to a larger electron loss rate and this enhances the critical reduced breakdown electric field strength in the temperature range where the concentration of molecular oxygen is relatively high. The results obtained in this work show reasonable agreement with experimental results from literature, and are important for the evaluation of the dielectric strength of CO2 in a highly reactive environment at elevated temperature.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.302
Times cited: 3
DOI: 10.1088/0963-0252/25/5/055025
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