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1. P-T Phase Diagram of LuFe2O4

Author

Maria Poienar, Julie Bourgeois, Christine Martin, Maryvonne Hervieu, Françoise Damay, Gaston Garbarino, Michael Hanfland, Thomas Hansen, François Baudelet, Jean Louis Bantignies, Patrick Hermet, Julien Haines, and Jérôme Rouquette

Subjects
LuFe2O4, pressure-temperature phase diagram, Crystallography, QD901-999
Abstract

The high-pressure behavior of LuFe2O4 is characterized based on synchrotron X-ray diffraction and neutron diffraction, resistivity measurements, X-ray absorption spectroscopy and infrared spectroscopy studies. The results obtained enabled us to propose a P-T phase diagram. In this study, the low pressure charge-ordering melting could be detected by synchrotron XRD in the P-T space. In addition to the ambient pressure monoclinic C2/m and rhombohedral R 3 ¯ m phases, the possible P 1 ¯ triclinic phase, the monoclinic high pressure form Pm and metastable modulated monoclinic phases were observed; the latter modulated monoclinic phases were not observed in the present neutron diffraction data. Furthermore, the transition to the Pm phase which was already characterized by strong kinetics is found to be favored at high temperature (373 K). Based on X-ray absorption spectroscopy data the Pm phase, which could be recovered at atmospheric pressure, can be explained by a change in the Fe-local environment from a five-fold coordination to a distorted 5 + 1 one.

Published
2018
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2. Tl0.6Mo3S5, an original large tunnel-like molybdenum sulfide with Mo zigzag chains and disordered Tl cations

Author

Bernard Malaman, Bertrand Lenoir, Petr Levinský, Jaafar Ghanbaja, Patrick Gougeon, Anne Dauscher, Sylvie Migot, Maryvonne Hervieu, Philippe Gall, Jiří Hejtmánek, Christophe Candolfi, Institut des Sciences Chimiques de Rennes (ISCR), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Institute of Physics of the Czech Academy of Sciences (FZU / CAS), Czech Academy of Sciences [Prague] (CAS), French Agence Nationale de la Recherche (ANR), through the program Energy Challenge for Secure French National Research Agency (ANR) [ANR-15-CE05-0027], Czech Science Foundation Grant Agency of the Czech Republic [18-12761S], program of Czech Research Infrastructures [LM2018096], ANR-15-CE05-0027,MASSCOTE,Matériaux Sulfures à Structures Complexes: application à la Thermoélectricité(2015), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Diffraction, Materials science, 02 engineering and technology, Crystal structure, [CHIM.MATE]Chemical Sciences/Material chemistry, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, Crystallography, Zigzag, Electron diffraction, Chemistry (miscellaneous), Seebeck coefficient, [CHIM]Chemical Sciences, General Materials Science, Wave vector, Crystallite, 0210 nano-technology, Monoclinic crystal system
Abstract

International audience; We report on the crystal structure and physical properties of Tl0.6Mo3S5, which belongs to a novel family of materials with large tunnels, reminiscent of those observed in the romanechite structure type. Tl cations are partially filling these tunnels delimited by the Mo-S cluster framework in which the Mo atoms form infinite zigzag chains. Single-crystal X-ray diffraction data indicate that this compound crystallizes in the monoclinic, non-centrosymmetric space group P21 (no. 4; a = 9.344(2) angstrom, b = 3.234(2) A, c = 11.669(2) A and beta = 113.09(2)° at 293 K). While electron diffraction performed on single crystals further evidences a commensurate modulation running solely along the b axis with a modulation wave vector further experiments carried out on a polycrystalline sample suggest a compositional dependence of q on the Tl content. Low-temperature transport properties measurements (5-300 K) reveal that Tl0.6Mo3S5 behaves as a narrow-band-gap n-type semiconductor. The strongly non-linear temperature dependence of the thermopower further suggests the presence of several electronic bands contributing to the electrical transport. Consistent with the extended electronic distribution in the tunnels that requires a description using two adjacent Tl sites, specific heat data measured down to 0.35 K evidence the presence of a Schottky-type anomaly that may be associated with the tunneling of the Tl cations between several equivalent, off-centered equilibrium sites. This inherent disorder contributes to suppression of the low-temperature Umklapp peak in the lattice thermal conductivity kL, the temperature dependence of which mimics that observed in strongly-disordered compounds. In spite of this characteristic, high kL values of up to 3.8 W m-1K-1 are reached at 300 K, due to the covalent Mo-S network that contributes to maintaining high sound velocities.

Published
2021
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3. Rare earth ferrites LuFe2O4±x polymorphism, polytypism and metastable phases

Author

Antoine Maignan, Maryvonne Hervieu, C. Martin, Françoise Damay, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
Work (thermodynamics), Materials science, Rare earth, 02 engineering and technology, General Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Structural transitions, [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Crystallography, Polymorphism (materials science), Metastability, High pressure, 0103 physical sciences, Energy materials, [CHIM.CRIS]Chemical Sciences/Cristallography, [CHIM]Chemical Sciences, General Materials Science, Polymorphism, 010306 general physics, 0210 nano-technology, Oxygen content, Layered ferrites
Abstract

International audience; This work is a compendium of the structural properties of layered LnFe2O4±x ferrites, focussed on recently discovered polymorphs and their transitions through five complex commensurate and incommensurate modulated structures. These phases are obtained varying the oxygen content (reversibly from O4.0 to O4.5) or applying high pressure (up to 15 GPa). The relationships between the different structures are discussed and models are proposed. These ferrites, which contain magnetic cations and exhibit remarkable 3D flexibility, open the road for magnetic, electric, catalytic or energy materials. © 2015 Elsevier Masson SAS. All rights reserved.

Published
2015
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4. Spin Glass to Weak Ferromagnetic Transformation in a New Layered Cobaltite: Consequence of Topotactic Reactions with Water at Room Temperature

Author

Vincent Caignaert, Maryvonne Hervieu, A. Maignan, Teruki Motohashi, Denis Pelloquin, Valerie Pralong, and Bernard Raveau

Subjects
Materials science, Spin glass, General Chemical Engineering, Inorganic chemistry, Niobium, Oxide, chemistry.chemical_element, General Medicine, General Chemistry, Cobaltite, chemistry.chemical_compound, Crystallography, chemistry, Ferromagnetism, Materials Chemistry, Curie temperature, Hydrate, Cobalt
Abstract

A new n = 2-member of the Ruddlesden−Popper (RP) cobaltite series, Sr3-δCo1.9Nb0.1O6.65-δ, has been stabilized by niobium doping. This oxide reacts topotactically with atmospheric water through hydrolysis/hydration and reduction of cobalt, leading to an oxyhydroxide hydrate derivative, Sr3-δCo1.9Nb0.1O4.86-δ(OH)3.04·0.4H2O. The reaction with water at room temperature induces a magnetic transformation from a spin glass behavior with a freezing temperature Tg ≈ 50 K for the pristine RP oxide to weak ferromagnetism with an apparent Curie temperature TC ≈ 200 K for the oxyhydroxide hydrate derivative. The spectacular effect of water upon the magnetic properties of this layered oxide is explained by the partial reduction of Co4+ into Co3+ species, concomitantly inducing a coordination change for cobalt cations that form antiferromagnetic coupling between high-spin Co3+. A generalization of this phenomenon to other layered cobaltites and even iron oxides is considered.

Published
2005

5. Crystal Chemistry of High-Tc Superconducting Copper Oxides

Author

Bernard Raveau, Claude Michel, Maryvonne Hervieu, Daniel Groult, Bernard Raveau, Claude Michel, Maryvonne Hervieu, and Daniel Groult

Subjects
High temperature superconductors, Copper oxide superconductors
Abstract

The recent discovery of high-temperature superconductivity in copper­ based oxides is an event of major importance not only with respect to the physical phenomenon itself but also because it definitely shows that solid state chemistry, and especially the crystal chemistry of oxides, has a crucial place in the synthesis and understanding of new materials for future appli­ cations. The numerous papers published in the field of high Tc supercon­ ductors in the last five years demonstrate that the great complexity of these materials necessitates a close collaboration between physicists and solid state chemists. This book is based to a large extent on our experience of the crystal chemistry of copper oxides, which we have been studying in the laboratory for more than twelve years, but it also summarizes the main results which have been obtained for these compounds in the last five years relating to their spectacular superconducting properties. We have focused on the struc­ ture, chemical bonding and nonstoichiometry of these materials, bearing in mind that redox reactions are the key to the optimization of their supercon­ ducting properties, owing to the importance of the mixed valence of copper and its Jahn-Teller effect. We have also drawn on studies of extended defects by high-resolution electron microscopy and on their creation by ir­ radiation effects.

Published
2013

6. Oxygen storage capacity and structural flexibility of LuFe2O4Cx (0 < x< 0.5)

Author

Antoine Maignan, Jérôme Rouquette, Erik Elkaim, Christine Martin, J. Bourgeois, Françoise Damay, Maryvonne Hervieu, Maria Poienar, Anne Guesdon, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), ANR-08-BLAN-0005,NewTOM,New Transition metal Oxide Materials(2008), ANR-08-JCJC-0092,RESPECT,Relations Structure-Propriétés et transitions structurales dans les ferroélectriques électroniques LuFe2O4 en fonction de la Pression et de la Température(2008), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)

Subjects
Thermogravimetric analysis, Materials science, Oxygen storage, Intercalation (chemistry), chemistry.chemical_element, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, 7. Clean energy, Oxygen, General Materials Science, Absorption (electromagnetic radiation), LuFe2O4, ComputingMilieux_MISCELLANEOUS, Multifunctional applications, Mechanical Engineering, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Ferroelectricity, 0104 chemical sciences, chemistry, Chemical engineering, Mechanics of Materials, Transmission electron microscopy, Oxygen absorption, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Ferrite (magnet), 0210 nano-technology, Structural flexibility
Abstract

International audience; Combining functionalities in devices with high performances is a great challenge that rests on the discovery and optimization of materials. In this framework, layered oxides are attractive for numerous purposes, from energy conversion and storage to magnetic and electric properties. We demonstrate here the oxygen storage ability of ferroelectric LuFe2O4Cx within a large x range (from 0 to 0.5) and its cycling possibility. The combination of thermogravimetric analyses, X-ray diffraction and transmission electron microscopy evidences a complex oxygen intercalation/de-intercalation process with several intermediate metastable states. This topotactic mechanism is mainly governed by nanoscale structures involving a shift of the cationic layers. The ferrite is highly promising because absorption begins at a low temperature ( D 200 C), occurs in a low oxygen pressure and the uptake of oxygen is reversible without altering the quality of the crystals. The storage/release of oxygen coupled to the transport and magnetic properties of LnFe2O4 opens the door to new tunable multifunctional applications.

Published
2014
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7. Sr 21 Bi 8 Cu 2 (CO 3 ) 2 O 41 , a Bi 5+ Oxycarbonate with an Original 10L Structure

Author

Gustaaf Van Tendeloo, Maryvonne Hervieu, Sylvie Malo, Anne Guesdon, Marco Daturi, Denis Pelloquin, Artem M. Abakumov, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), EMAT, University of Antwerp, University of Antwerp (UA), Center for Electrochemical Energy Storage, Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia., Laboratoire catalyse et spectrochimie (LCS), Centre National de la Recherche Scientifique (CNRS)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Université de Caen Normandie (UNICAEN), Normandie Université (NU), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Electron Microscopy for Materials Science - EMAT (Antwerp, Belgium), Universiteit Antwerpen = University of Antwerpen [Antwerpen], and Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Diffraction, Inorganic carbon compounds, Hexagonal crystal system, Chemistry, Structure (category theory), Infrared spectroscopy, 3. Good health, Layered structure, Inorganic Chemistry, Paramagnetism, Crystallography, Chemical structure, Transmission electron microscopy, Group (periodic table), Oligomers, Cations, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry, Layers
Abstract

The layered structure of Sr21Bi8Cu2(CO3)(2)O-41 (Z = 2) was determined by transmission electron microscopy, infrared spectroscopy, and powder X-ray diffraction refinement in space group P6(3)/mcm (No. 194), with a = 10.0966(3)angstrom and c = 26.3762(5)angstrom. This original 10L-type structure is built from two structural blocks, namely, [Sr15Bi6Cu2(CO3)O-29] and [Sr6Bi2(CO3)O-12]. The Bi5+ cations form [Bi2O10] dimers, whereas the Cu2+ and C atoms occupy infinite tunnels running along (c) over right arrow. The nature of the different blocks and layers is discussed with regard to the existing hexagonal layered compounds. Sr21Bi8Cu2(CO3)(2)O-41 is insulating and paramagnetic.

Published
2014
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8. Modular construction of oxide structures-compositional control of transition metal coordination environments

Author

John B. Claridge, Matthew J. Rosseinsky, Christophe Tenailleau, Mathieu Allix, Maryvonne Hervieu, James P. Hirst, Michael F. Thomas, Centre National de la Recherche Scientifique - CNRS (FRANCE), Ecole Nationale Supérieure d'Ingénieurs de Caen - ENSICAEN (FRANCE), and University of Liverpool (UNITED KINGDOM)

Subjects
Neutrons, Annealing (metallurgy), Matériaux, Non-blocking I/O, Inorganic chemistry, Iron oxide, Oxide, General Chemistry, Biochemistry, Catalysis, chemistry.chemical_compound, Crystallography, Colloid and Surface Chemistry, Transition metal, chemistry, Octahedron, Vacancy defect, Selected area diffraction, Structures-compositional
Abstract

The effects of reaction temperature and pO2 were investigated on a series of (Ba,Ca,Nd)FeO3-delta perovskite systems in order to isolate phases containing ordered arrangements of the distinct vacancy and cation ordering patterns identified in less compositionally complex iron oxide systems. Initial synthesis in air at high temperature yields cubic perovskite phases (I) with average iron oxidation states higher than 3; selected area electron diffraction together with diffuse features observed in the synchrotron X-ray diffraction (SXRD) patterns of these materials show evidence of small domains of short-range cation and vacancy order. Annealing these materials in nitrogen or in a sealed tube in the presence of an NiO/Ni buffer yielded the Fe(3+) phase Ca2Ba2Nd2Fe6O16 (II), closely related to Sr2LaFe3O8 but with partial cation order as well as anion order present the larger Ba cations are largely present in the 12-coordinate site between the octahedral iron layers, and Ca is largely present in 10-coordinate sites between octahedral and tetrahedral sites. Further reduction of Ca2Ba2Nd2Fe6O16 using a Zr getter yields the mixed-valence phase Ca2Ba2Nd2Fe6O15.6 (III). The structure of III was solved by maximum entropy analysis of XRD data coupled with analysis of high-temperature neutron diffraction data and refined against combined SXRD and high-Q ambient-temperature neutron data. This material crystallizes in a 20-fold perovskite super cell (Imma, a approximately square root(2 x a(p), b approximately 10 x a(p), c approximately square root(x 2a(p)) and can be visualized as an intergrowth between brownmillerite (Ca2Fe2O5) and the YBa2Fe3O8 structure. There are three distinct iron coordination environments, octahedral (O), square-pyramidal (Sp), and trigonal planar (Tp, formed by distorting the tetrahedral site in brownmillerite), which form a Sp-O-Tp-O-Sp repeat. Bond valence calculations indicate that Tp is an Fe(2+) site, while the O and Sp sites are Fe(3+). The A-site cations are also partially ordered over three distinct sites: 8-coordinate between the Sp layers, 10-coordinate between Tp and O layers, and 12-coordinate between Sp and O layers. Mossbauer spectroscopy, magnetometry, and variable-temperature neutron diffraction show that the material undergoes two magnetic transitions at approximately 700 and 255 K.

Published
2008

9. Reactivity of (–)-cytisine and derivatives towards palladium salts. X-ray characterization of a new palladium complex of (–)-cytisine

Author

Jacques Rouden, Jacques Muzart, Sandrine Bouquillon, André Leclaire, Marie-Claire Lasne, Maryvonne Hervieu, Bernard Tinant, Institut de Chimie Moléculaire de Reims - UMR 7312 (ICMR), SFR Condorcet, Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Centre National de la Recherche Scientifique (CNRS)-SFR CAP Santé (Champagne-Ardenne Picardie Santé), Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Université de Reims Champagne-Ardenne (URCA)-Université de Picardie Jules Verne (UPJV)-Université de Reims Champagne-Ardenne (URCA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Réactions sélectives et applications (RSA), Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de chimie moléculaire et thioorganique (LCMT), Centre National de la Recherche Scientifique (CNRS)-Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU), Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Université de Reims Champagne-Ardenne (URCA)-Institut de Chimie du CNRS (INC)-SFR CAP Santé (Champagne-Ardenne Picardie Santé), Université de Reims Champagne-Ardenne (URCA)-Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS)-SFR Condorcet, Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS)-Université de Reims Champagne-Ardenne (URCA)-Centre National de la Recherche Scientifique (CNRS), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut Normand de Chimie Moléculaire Médicinale et Macromoléculaire (INC3M), Normandie Université (NU)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Le Havre Normandie (ULH), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Cytisine, Stereochemistry, General Chemical Engineering, chemistry.chemical_element, Crystal structure, 010402 general chemistry, 01 natural sciences, Medicinal chemistry, Catalysis, Kinetic resolution, chemistry.chemical_compound, [CHIM]Chemical Sciences, Reactivity (chemistry), 010405 organic chemistry, General Chemistry, 0104 chemical sciences, 3. Good health, chemistry, 13. Climate action, Phenethyl alcohol, Complexation, Enantiomer, Palladium, X-ray analysis
Abstract

Reactivity of (-)-cytisine and substituted cytisines towards PdCl2(MeCN)(2) and Pd(OAC)(2) has been studied. Two complexes of Pd(II), PdCl2((-)-cytisine)(2) and Pd(OAC)(2)((-)-cytisine)(2) were prepared. X-ray analysis of Pd(OAc)(2)((-)-cytisine)(2) revealed a square planar environment of the metal center and a trans geometry. Cytisine and N-methylcytisine have been combinated to Pd(OAc)(2) or PdCl2(MeCN)(2) to catalyze the oxidative kinetic resolution of phenethyl alcohol. (C) 2006 Academie des sciences. Published by Elsevier SAS. All rights reserved.

Published
2006
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10. Novel, oxygen-deficient <tex>n=3$</tex> RP-member <tex>Sr_{3}NdFe_{3}O_{9-\delta}$</tex> and its topotactic derivatives

Author

Joke Hadermann, M. Giot, Claude Michel, Denis Pelloquin, Maryvonne Hervieu, Bernard Raveau, and Vincent Caignaert

Subjects
chemistry.chemical_classification, Diffraction, Oxygen deficient, General Chemical Engineering, Oxide, General Chemistry, Polymer, law.invention, Crystallography, chemistry.chemical_compound, Hydrolysis, chemistry, law, Lattice (order), Materials Chemistry, Orthorhombic crystal system, Electron microscope
Abstract

The stabilization of the n = 3 member of the Ruddlesden−Popper series has been investigated in the Sr−Nd−Fe−O system. A new series of phases closely derived from RP-type structures has been synthesized and characterized by X-ray diffraction and electron microscopy. The control of the oxygen stoichiometry first allowed us to isolate a new highly oxygen deficient, layered oxide, Sr3NdFe3O9-δ. The structural analysis has revealed that this oxide crystallizes in an orthorhombic lattice (ap√2 × ap√2 × 28 A), distorted with regard to the ideal I-type symmetry of the RP-type structures. Interestingly, this oxygen-deficient n = 3 RP-member reacts at room temperature with ambient moisture to transform into a hydrated oxyhydroxide, Sr3NdFe3O7.5(OH)2·H2O. This second phase can be dehydrated topotactically in two steps by heating to 400 °C, leading to Sr3NdFe3O7.5(OH)2 and then Sr3NdFe3O8.5+δ, respectively. The reversible character of these hydration/hydrolysis reactions is also demonstrated.

Published
2004

11. Strain effects in charge-ordered Pr0.5Ca0.5MnO3 manganite thin films

Author

B. Mercey, Ch. Simon, Wilfrid Prellier, Maryvonne Hervieu, E. Rauwel Buzin, B. Raveau, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), and Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], Materials science, Analytical chemistry, Mineralogy, General Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, Condensed Matter Physics, Manganite, Pulsed laser deposition, Charge ordering, Compressive strength, Lattice (order), Ultimate tensile strength, [CHIM]Chemical Sciences, General Materials Science, Orthorhombic crystal system, Thin film
Abstract

Thin films of the charge-ordered (CO) compound Pr 0.5 Ca 0.5 MnO 3 have been grown by utilizing the Pulsed Laser Deposition technique. Films are deposited onto LaAlO 3 and SrTiO 3 substrates in order to check the effect of strains (compression and tensile). Using various techniques of characterization, we show that the strains of substrate influence the lattice parameters, the orientation of the orthorhombic structure, the transport properties and the stability of the CO state.

Published
2003
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12. Staircase effect in metamagnetic transitions of charge and orbitally ordered manganites

Author

A. Maignan, Maryvonne Hervieu, Sylvie Hébert, Vincent Hardy, Christine Martin, and Bernard Raveau

Subjects
Physics, Condensed Matter - Materials Science, Strongly Correlated Electrons (cond-mat.str-el), Condensed matter physics, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Collapse (topology), Charge (physics), Condensed Matter Physics, Electronic, Optical and Magnetic Materials, Interpretation (model theory), Magnetization, Condensed Matter - Strongly Correlated Electrons, Antiferromagnetism, Condensed Matter::Strongly Correlated Electrons
Abstract

This paper reports on peculiar metamagnetic transitions which take place in antiferromagnetic, charge and orbitally ordered (AFCOO) manganites. At very low temperatures, the virgin magnetization curves of some of these compounds exhibit several, sharp steps giving rise to a staircase-like shape. This staircase effect is shown to be sensitive to various experimental parameters. Several potential interpretations of the staircase effect are discussed in relation to this set of results. A martensitic-like scenario, involving a leading role of the structural distortions associated to the collapse of the orbital ordering, is found to be the most plausible interpretation., To be published in J. Mag. Mag. Mat

Published
2003

13. Neutron scattering evidence for magnetic field driven abrupt magnetic and structural transitions in a phase separated manganite

Author

Annie Brûlet, Emmanuelle Suard, B. Raveau, Gilles André, Antoine Maignan, C. Martin, Damien Saurel, Ch. Simon, Maryvonne Hervieu, François Fauth, C. Yaicle, Richard Retoux, Sylvie Hébert, Vincent Hardy, Françoise Bourée, Z. Jirák, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), European Synchrotron Radiation Facility (ESRF), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut Laue-Langevin (ILL), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, ILL, and Arxiv, Import

Subjects
Physics, Condensed Matter - Materials Science, Condensed matter physics, Neutron diffraction, Order (ring theory), Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, 02 engineering and technology, Neutron scattering, 021001 nanoscience & nanotechnology, Manganite, 01 natural sciences, [PHYS.COND.CM-MS] Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Magnetization, Ferromagnetism, 0103 physical sciences, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Antiferromagnetism, Condensed Matter::Strongly Correlated Electrons, 010306 general physics, 0210 nano-technology, Ground state
Abstract

Substitutions at the Mn site of the charge-ordered ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ manganite is an effective way to induce abrupt jumps on the magnetic-field-driven magnetization curve. In order to get new insights into the origin of this remarkable feature, the ${\mathrm{Pr}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{Mn}}_{0.97}{\mathrm{Ga}}_{0.03}{\mathrm{O}}_{3}$ perovskite manganite has been studied by neutron diffraction versus temperature and at 2.5 K in an applied magnetic field up to 6 T. A weak and complex antiferromagnetic order is found for the low-temperature ground state. Magnetic transitions, associated with structural ones, are evidenced for certain strengths of magnetic field, which gives rise to the steplike behavior corresponding to the magnetization curve. Small-angle neutron scattering provides evidence for a nucleation process of micron-size ferromagnetic domains which follows the magnetization behavior.

Published
2003

14. The layered manganate <tex>Sr_{4-x}Ba_{x}Mn_{3}O_{10}:$</tex> synthesis, structural and magnetic properties

Author

Claude Michel, Antoine Maignan, Bernard Raveau, N. Floros, Gustav van Tendeloo, and Maryvonne Hervieu

Subjects
Chemistry, Manganate, Inorganic chemistry, Oxide, General Chemistry, Crystal structure, Condensed Matter Physics, Magnetic susceptibility, chemistry.chemical_compound, Crystallography, Octahedron, Antiferromagnetism, General Materials Science, Lamellar structure, Solid solution
Abstract

The layered manganate Sr 4 Mn 3 O 10 has been synthesized and a partial substitution of Ba for Sr, leading to the solid solution Sr 4− x Ba x Mn 3 O 10 with 0≤ x ≤2.50, has been shown. This phase, isotypic to Ba 4 TiPt 2 O 10 , crystallizes in the Cmca space group with a =5.4766(1) A, b =12.4659(2) A, c =12.5282(2) A for x =0. The structural analysis of this oxide shows close relationships with the 9 L-hexagonal BaMnO 3 structure, both structures being built up from ‘Mn 3 O 12 ’ trioctahedral units of face sharing octahedra, linked through their apices. The main difference between the two structures concerns the relative orientation of two successive Mn 3 O 12 groups, leading to a layered structure for Sr 4 Mn 3 O 10 and to a tridimensional framework for 9 L-BaMnO 3 . The detailed HREM study shows the existence of extended defects, mainly along (010), which correspond to shearing mechanisms and suggests the possible existence of other original members. These oxides show an antiferromagnetic transition at T N =210–215 K.

Published
2000

15. Cluster configurations in modulated EuV x Mo 8± y O 14 crystals

Author

H. Leligny, J. Tortelier, Patrick Gougeon, Bernard Raveau, Maryvonne Hervieu, Pascal Roussel, D. Grebille, Ph. Labbé, Laboratoire de cristallographie et sciences des matériaux (CRISMAT), École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC), Unité de Catalyse et Chimie du Solide - UMR 8181 (UCCS), Centrale Lille Institut (CLIL)-Université d'Artois (UA)-Centrale Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Lille, Institut des Sciences Chimiques de Rennes (ISCR), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche sur les Matériaux Avancés (IRMA), Normandie Université (NU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Institut national des sciences appliquées Rouen Normandie (INSA Rouen Normandie), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Rouen Normandie (UNIROUEN), Institut National des Sciences Appliquées (INSA)-Normandie Université (NU)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Université d'Artois (UA)-Centrale Lille-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), and Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Diffraction, Chemistry, Inorganic chemistry, General Medicine, Crystal structure, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 010402 general chemistry, 010403 inorganic & nuclear chemistry, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, 0104 chemical sciences, Crystal, Crystallography, Lattice (order), Cluster (physics), Orthorhombic crystal system, Wave vector, ComputingMilieux_MISCELLANEOUS, Solid solution
Abstract

Three orthorhombic crystals of chemical formula Eu x V y Mo8±z O14 were investigated by X-ray diffraction (Mo Kα radiation, λ = 0.71073 Å). They have nearly the same lattice parameters (a ≃ 11.3, b ≃ 10.0, c ≃ 9.2 Å), display one-dimensional incommensurate modulations of wavevector q* = γc* and are characterized by the same superspace group Cmca(00γ)s00. The crystals differ both in their compositions (namely Eu0.976(6)V1.13(5)Mo7.10(5)O14, Eu0.986(4)V1.10(3)Mo7.30(1)O14 and EuMo7.96(1)O14) and in their γ components [0.195 (2), 0.245 (2) and 0.286 (3), respectively]. The average structures of these crystals appear closely related to the structures of LaMo7.7O14 (not modulated) and LaMo8O14 (modulated); however, two main differences are outlined: first, the modulation direction is c in the Eu-containing crystals but b in the modulated La-containing crystal [q* = (1/3)b*], second, the Eu-containing crystals have centrosymmetric structures while the La-containing crystals have polar structures (space group C2ca). The Mo (or Mo and V) atoms are stacked to form (001) layers of metallic clusters. The density modulation of these structures implies the existence of the new types of clusters Mo9, Mo10, Mo6V4, Mo7V3 and Mo8V2 besides the clusters M 8 (Mo8, Mo6V2 and Mo7V) and M 7 (Mo7 and Mo6V) which are already known. Mo8 units with cis and trans configurations and Mo6V2 units with a trans configuration appear as the main cluster types in these crystals. The nature of the metallic clusters changes along c, but inside one (001) layer it is likely that only one cluster type with a given configuration is present. The main structural result is the formation, in some unit cells, of strong intercluster Mo—Mo, Mo—V or V—V bonds with distances close to 2.6 Å within a layer as well as between two neighbouring layers.

Published
1999
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19. The (3 + 2)D structure of oxygen deficient LaSrCuO3.52.

Author

Joke Hadermann, Olivier Pérez, Nicolas Créon, Claude Michel, and Maryvonne Hervieu

Abstract

The (3 + 2)D modulated structure of the oxygen deficient compound LaSrCuO3.52 was determined using a combination of electron diffraction and neutron diffraction. The cell parameters are a = b = 3.7587(3) Å, c = 13.0074(9) Å, α = β = γ = 90°, superspace group I4/mmm (αα0, α−α0)00 mg, α = 0.2222(3), Rp = 4.5%, R0 = 2.1%, R1 = 4.9%. The oxygen vacancies are located in the CuO2−δ plane and are ordered with the oxygen atoms, creating three different oxygen environments for the Cu atoms: CuO4 squares, CuO5 pyramids and CuO6 octahedra. [ABSTRACT FROM AUTHOR]

Published
2007
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20. One route for low dimensional oxide design: understanding their complexity.

Author

Maryvonne Hervieu and Claude Michel

Abstract

The design of new architectures and the optimization of particular properties need detailed knowledge of the real crystalline state and structural mechanisms of the materials. In this feature article, we intend to illustrate how combination of two complementary techniques, high resolution electron microscopy (HREM) and beam diffraction techniques (electrons, X-rays, neutrons), is efficient. Three examples of low dimensional oxides are presented, focussing our attention on the existence of successive ‘structural’ levels. [ABSTRACT FROM AUTHOR]

Published
2007
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21. Ordered Pd2+Cu2+ substitution in 1.2.3. superconductor : The oxide YBa2Cu(3−x)PdxOy (X ≈ 0,5) with Pd2+ in square planar coordination

Author

Robert Tournier, Maryvonne Hervieu, Y. Laligant, André Sulpice, A. Le Bail, B. Raveau, Gerard Ferey, Centre de Recherches sur les Très Basses Températures (CRTBT), and Université Joseph Fourier - Grenoble 1 (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Inorganic chemistry, Oxide, Energy Engineering and Power Technology, chemistry.chemical_element, Crystal structure, 02 engineering and technology, 01 natural sciences, Square (algebra), Inorganic Chemistry, Magnetization, chemistry.chemical_compound, Planar, 0103 physical sciences, Materials Chemistry, [CHIM]Chemical Sciences, Physical and Theoretical Chemistry, Electrical and Electronic Engineering, 010306 general physics, Inorganic compound, ComputingMilieux_MISCELLANEOUS, chemistry.chemical_classification, Superconductivity, [PHYS]Physics [physics], Resistive touchscreen, Condensed matter physics, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Copper, 3. Good health, Electronic, Optical and Magnetic Materials, Crystallography, chemistry, Meissner effect, X-ray crystallography, Ceramics and Composites, 0210 nano-technology, Palladium
Abstract

The substitution of copper by palladium II in YBa 2 Cu 3 O 7 leads to a new compound Yba 2 Cu 2.5 Pd 0.5 O y with orthorhombic symmetry ( a = 3.841(1) A, b = 3.883(1) A, c = 11.671(3) A; space group Pmmm ) in which Pd exclusively occupies (1a) sites of the structure, corresponding to cations in square planar coordination. A resistive transition occurs at 49 K; magnetic measurements indicate less than 5% of the full Meissner effect.

Published
1988
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22. Two Variants of the 1/2[110]p(203)p, Crystallographic Shear Structures: The Phasoid Sr0.61 Pb0.18(Fe0.75Mn0.25)02.29.

Author

Lepoittevin, Christophe, Hadermann, Joke, MaIo, Sylvie, Olivier Pérez, Van TendeIoo, Gustaaf, and Maryvonne Hervieu

Subjects
*PEROVSKITE, *TRANSMISSION electron microscopy, *CRYSTALLOGRAPHY, *X-ray diffraction, *SPECTRUM analysis
Abstract

For the composition (Sr0.61Pb0.18)(Fe0.75Mn0.25)O2.29, a new modulated crystallographic shear structure, related to perovskite, has been synthesized and structurally characterized by transmission electron microscopy. The structure can be described using a monoclinic supercell with cell parameters am = 27.595(2) Å, bm = 3.8786(2) Å, cm = 13.3453(9) Å, and βm = 100.126(5)°, refined from powder X-ray diffraction data. The incommensurate crystal-lographic shear phases require an alternative approach using the superspace formalism. This allows a unified description of the incommensurate phases from a monoclinically distorted perovskite unit cell and a modulation wave vector. The structure deduced from the high-resolution transmission electron microscopy and high-angle annular dark-field-scanning transmission electron microscopy images is that of a 1/2[110]p,(203)p, crystallographic shear structure. The structure follows the concept of a phasoid, with two coexisting variants with the same unit cell. The difference is situated at the translational interface, with the local formation of double (phase 2) or single (phase 1) tunnels, where the Pb cations are likely located. [ABSTRACT FROM AUTHOR]

Published
2009
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