Publications

2003

• New development in time-resolved micro-photoluminescence spectroscopy of heterogeneous natural and synthetic inorganic materials
  
  • Panczer Gérard
  • Ollier N.
  • Champagnon Bernard
  • Gaft M.
  • Boudeulle M
  • Moine B.
  Optical Materials, Elsevier, 2003, 24 (1-2), pp.253-257. Inorganic materials with optical properties and especially naturally multidoped geomaterials often present micro-scale heterogeneities (growth zoning, inclusions, devitrification, micro-phases…). Identification and optical effects of such heterogeneities have more and more to be taken into account. To reach the microscopic scale during photoluminescence studies, a microscope has been modified in order to allow pulsed laser injection (from UV to visible), beam focus with micro-scale resolution on the sample, as well as collection of micro- fluorescence. Such equipment allows now undertaking time-resolved measurements of micro-phases. Applications on phosphors, devitrified glass and geomaterials are presented. (10.1016/S0925-3467(03)00131-9)
  DOI : 10.1016/S0925-3467(03)00131-9
• Etude de la matière de vortex dans Bi2Sr2CaCU208 à l'aide de la résonnance de plasma Josephson.
  
  • Colson Sylvain
  , 2003. La résonance de plasma Josephson (JPR) nous permet d'évaluer la distance moyenne rw des excursions thermiques relatives de deux vortex bidimensionnels consécutifs sur la même ligne de flux, dans le supraconducteur lamellaire Bi2Sr2CaCu2O8+d (BSCCO). Ici, on a déterminé rw dans le solide de vortex dans des monocristaux de BSCCO sous-dopés, à l'aide de mesures expérimentales de la JPR en utilisant la perturbation de cavité résonante et la méthode bolométrique. Dans les échantillons vierges, sous faible champ magnétique, la dépendance en température T et en champ B de rw s'explique par le rôle dominant de la tension de ligne et sa renormalisation par les fluctuations thermiques. Celles-ci provoquent son amollissement, conduisant à la transition de phase du premier ordre entre le solide et le liquide de vortex. On observe une dépendance rw(T,B) identique dans les cristaux irradiés aux ions lourds, pour B << Bf , validant une description en terme de 'supraconducteur discret' du matériau.
• Response functions of semiconductors and insulators : from the Bethe-Salpeter equation to time-dependent density functional theory
  
  • Sottile Francesco
  , 2003. Electronic excitations, caused for example by irradiation with electrons, light or modern photon sources (synchrotron, ultra-fast lasers), are key quantities for the study of materials, ranging from solids to atoms, from surface to nanoscale systems. An accurate understanding and prediction of the interaction of radiation and matter can even favor remarkable technological breakthroughs, like new functionalities for bulk systems (e.g. in optoelectronics) or, in the long term, in biological applications ("bottom-up" assembling or molecular machines1).
• Helium behavior in UO2 polycrystalline disks
  
  • Guilbert Severine
  • Sauvage Thierry
  • Erramli Hassan
  • Barthe Marie-France
  • Desgardin Pierre
  • Blondiaux Gilbert
  • Corbel Catherine
  • Piron Jean-Paul
  Journal of Nuclear Materials, Elsevier, 2003, 321 (2-3), pp.121-128. (10.1016/S0022-3115(03)00212-5)
  DOI : 10.1016/S0022-3115(03)00212-5
• Raman spectroscopy study of β-irradiated silica glass
  
  • Boizot B.
  • Agnello S.
  • Reynard Bruno
  • Boscaino B
  • Petite G.
  Journal of Non-Crystalline Solids, Elsevier, 2003, 325 (1-3), pp.22-28. Natural and synthetic silica glass samples with different OH content have been submitted to β-irradiation at different doses from 106 to 5 × 109 Gy in a Van de Graaff accelerator. Structural changes under irradiation have been analyzed by Raman spectroscopy. The main findings are: (i) a decrease of the Si–O–Si angular dispersion and the average Si–O–Si angle as a function of dose and (ii) an increase of number of three-membered SiO4 ring concentration during irradiation. These results show therefore that purely electronic excitation from β-irradiation induces in a-SiO2 small but significant structural changes of the SiO4 membered ring statistics (size and dispersion), consistent with a slight densification. (10.1016/S0022-3093(03)00334-X)
  DOI : 10.1016/S0022-3093(03)00334-X
• Influence of external β-irradiation in oxide glasses
  
  • Ollier Nadège
  • Champagnon Bernard
  • Boizot Bruno
  • Panczer Gérard
  • Padlyak B.
  Journal of Non-Crystalline Solids, Elsevier, 2003, 323 (1-3), pp.200-206. Radiation effects in oxide glass as external β-irradiation has been investigated by Raman spectroscopy, Cr3+ luminescence and EPR spectroscopy to analyze microstructure evolution. Comparison between simplified and complex glasses (high-level nuclear waste glass analogue) was undertaken. Migration and segregation of sodium have been confirmed on simplified irradiated glasses by a polymerization increase and dissolved oxygen presence. Densification under irradiation has also been demonstrated with the increase of three-membered silicate rings in silicate glass and the decrease of the average Si–O–Si angle in the borosilicate glass. In both glasses, Cr3+ crystal field was increased, suggesting a Cr–O length decrease. The complex borosilicate glass responds differently: densification effect and Na segregation were not detected. Under β-irradiation, electron-trapping processes on Cr6+ occurred, forming Cr4+ and Cr5+ species. (10.1016/S0022-3093(03)00307-7)
  DOI : 10.1016/S0022-3093(03)00307-7
• Polymorphism of tricalcium silicate in Portland cement: a fast visual identification of structure and superstructure.
  
  • Courtial Mireille
  • de Noirfontaine Marie-Noëlle
  • Dunstetter Frederic
  • Gasecki Gilles
  • Signes-Frehel Marcel
  Powder Diffraction, Cambridge University Press (CUP), 2003, 18 (1), pp.7-15. So-called alite is a solid solution of tricalcium silicate Ca3SiO5 with a few percent of impurities. It constitutes the major phase of anhydrous Portland cement. In industrial compounds, alite crystallises into two monoclinic forms designated M1 and M3. The possibility of correlation between the crystallographic structure of the clinker and its reactivity is still an open question. The answer of such a question involves a proper quantitative analysis of the various phases –including the exact alite polymorph- of the industrial product. The rather similar structure of the two alites makes it difficult to distinguish them from their XRD patterns. This paper shows that five angular windows in the X-Ray diffraction patterns can be used with synthetic alites as well as industrial compounds, to identify the nature of the actual polymorph (M1 or M3) present and the structural model to be used (with or without superstructure) in subsequent Rietveld analysis of the data. (10.1154/1.1523079)
  DOI : 10.1154/1.1523079
• Anisotropic Enhancement of Superconductivity in Heavy-Ion Irradiated KBa BiO3
  
  • Marcenat C.
  • Blanchard S.
  • Marcus J.
  • Paulius L.M.
  • J. van Der Beek C.
  • Konczykowski M.
  • Klein Thierry
  Physical Review Letters, American Physical Society, 2003, 90, pp.037004. We have measured the specific heat, resistivity, and ac susceptibility of K; Ba BiO3 single crystals before and after introduction of either point or columnar defects by electron (EI) or heavy-ion irradiation (HII).While the magnetic field dependence of these properties remains mainly unaffected by EI, the irreversibility line and the location of the specific heat anomaly are both shifted up in temperature after HII. The shift is apparent only if the magnetic field is applied parallel to the ion tracks. For perpendicularly applied fields, both lines lie at the same field as in the pristine sample. These experiments call the nature of the vortex liquid state into question. (10.1103/PhysRevLett.90.037004)
  DOI : 10.1103/PhysRevLett.90.037004
• Radiation-induced defects in dickites from the El Berrocal granitic system (Spain): relation with past occurrence of natural radioelements.
  
  • Allard Thierry
  • Ildefonse Philippe
  • Del-Villar Luis-Pérez
  • Sorieul Stéphanie
  • Pelayo Marta
  • Boizot Bruno
  • Balan Etienne
  • Calas Georges
  European Journal of Mineralogy, Copernicus, 2003, 15, pp.629-640. This study deals with the radiation-induced defects in fracture filling clay-minerals from the El Berrocal U-deposit (Spain), which is considered as a natural analogue of a high-level nuclear waste repository in granitic rock. Mineralogical analyses shows the widespread occurrence of dickite as a secondary alteration phase, together with various amounts of associated smectite, illite, carbonates and primary minerals. Native radiation-induced defects accumulated in the dickite and smectite structure are identified by electron paramagnetic resonance spectroscopy (EPR). They are distinguished by their spectroscopic parameters and thermal stability, and can be reproduced by artificial irradiation. The dickite defects are similar to the well-characterized features in natural kaolinites, including defects stable at the scale of geological periods. Dickite can thus be used as a natural dosimeter to trace radioelement transfer in relevant geological systems. The concentration of stable defects in dickites is related to the present dose-rates, assuming dosimetry parameters from model kaolinites and several scenarii for dickite ages inferred from major tectonic events. This study demonstrates that the El Berrocal dickites correspond to different generations having recorded retention or migration events of radioelements within the whole system. (10.1127/0935-1221/2003/0015-0629)
  DOI : 10.1127/0935-1221/2003/0015-0629
• Study of the effect of high electronic excitations in quasicrystals irradiated with heavy ions
  
  • Coddens G.
  • Dunlop A.
  • Dammak Hichem
  • Chatterjee R.
  • Calvayrac Y.
  • Quiquandon M.
  • Elkaïm E.
  • Gailhanou M.
  • Rouzière S.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2003, 211 (1), pp.122-132. We have studied the effect of irradiation with 900 MeV Pb and 780 MeV Xe ions on quasicrystals Al62Cu25.5Fe12.5 and the related cubic α-phase Al55Cu27Fe11Si 7. The fluences ranged from 1010 to 5.8×10 13 ions/cm2. Irradiations were performed at 80 K and at room temperature. The structural changes induced by the electronic excitations were studied by high-resolution X-ray diffraction. Whereas one might have expected the irradiations to induce important structural transformations, e.g. a phase transition from an icosahedral to a rhombohedral phase, only minor structural modifications are observed in the icosahedral phase and none in the α-phase. The defects created are not phasonic. Our results suggest a remarkable structural stability of these phases with respect to heavy-ion irradiation. © 2003 Elsevier B.V. All rights reserved. (10.1016/S0168-583X(03)01210-2)
  DOI : 10.1016/S0168-583X(03)01210-2
• Magnetization reversal and two level fluctuations by spin-injection in a ferromagnetic metallic layer
  
  • Wegrowe J. -E.
  Physical Review B: Condensed Matter and Materials Physics (1998-2015), American Physical Society, 2003, 68, pp.214414. Slow magnetic relaxation and two level fluctuations measurements under high current injection is performed in single-contacted ferromagnetic nanostructures. The magnetic configurations of the samples are described by two metastable states of the uniform magnetization. The current-dependent effective energy barrier due to spin-transfer from the current to the magnetic layer is measured. The comparison between the results obtained with Ni nanowires of 6 $\\mu $m length and 60 nm diameter, and Co (10 nm)/Cu (10 nm)/Co(30 nm) nanometric pillars of about 40 nm in diameter refined the characterization of this effect. It is shown that all observed features cannot be reduced to the action of a current dependent effective field. Instead, all measurements can be described in terms of an effective temperature, which depends on the current amplitude and direction. The system is then analogous to an unstable open system. The effect of current induced magnetization reversal is interpreted as the balance of spin injection between both interfaces of the ferromagnetic layer.
• Tricalcium Silicate Ca3SiO5, the major component of anhydrous Portland Cement: on the conservation of distances and directions and their relationship to the structural elements
  
  • de Noirfontaine Marie-Noëlle
  • Dunstetter Frederic
  • Courtial Mireille
  • Gasecki Gilles
  • Signes-Frehel Marcel
  Zeitschrift für Kristallographie, De Gruyter, 2003, 218 (1), pp.8-11. Tricalcium silicate, the major component of Portland cement exhibits a complex phase diagram, surprisingly still not completely understood. In this letter, new results are highlighted including a comprehensive study of the superstructure relationship between the polymorphs, and new ideas about the structural analysis. The organisation of the silicate skeleton can be described in terms of 1-D or 2-D elements, from which arise new hypotheses about the cohesion and the chemical origin of the observed superstructures. (10.1524/zkri.218.1.8.20769)
  DOI : 10.1524/zkri.218.1.8.20769