Browsing by Author "Luneville, L"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Intricate disorder in defect fluorite/pyrochlore: a concord of chemistry and crystallography
    (Springer Nature, 2017-06-16) Simeone, D; Thorogood, GJ; Huo, D; Luneville, L; Baldinozzi, G; Petricek, V; Porcher, F; Ribis, J; Mazerolles, L; Largeau, L; Berar, JF; Surble, S
    Intuitively scientists accept that order can emerge from disorder and a significant amount of effort has been devoted over many years to demonstrate this. In metallic alloys and oxides, disorder at the atomic scale is the result of occupation at equivalent atomic positions by different atoms which leads to the material exhibiting a fully random or modulated scattering pattern. This arrangement has a substantial influence on the material’s properties, for example ionic conductivity. However it is generally accepted that oxides, such as defect fluorite as used for nuclear waste immobilization matrices and fuel cells, are the result of disorder at the atomic scale. To investigate how order at the atomic scale induces disorder at a larger scale length, we have applied different techniques to study the atomic composition of a homogeneous La 2 Zr 2 O 7 pyrochlore, a textbook example of such a structure. Here we demonstrate that a pyrochlore, which is considered to be defect fluorite, is the result of intricate disorder due to a random distribution of fully ordered nano-domains. Our investigation provides new insight into the order disorder transformations in complex materials with regards to domain formation, resulting in a concord of chemistry with crystallography illustrating that order can induce disorder. © The Author(s) 2017
  • Thumbnail Image
    Item
    Radiation-induced micro-structures as ground states of a Swift-Hohenberg energy functional
    (American Institute of Physics (AIP), 2019-02-08) Simeone, D; Thorogood, GJ; Murphy, GL; Forestier, A; Garcia, P; Luneville, L
    We demonstrate that the Swift-Hohenberg functional, which is used to describe patterning observed in out of equilibrium systems such as diblock copolymers, Rayleigh-Benard convection, and thin film magnetic garnets, can be applied to radiation-induced patterns that occur in non-miscible alloys. By comparing ground states obtained from the minimization of this functional and a 2D numerical simulation performed on an irradiated AgCu material, which is the archetype of a non-miscible alloy, we show that the Swift-Hohenberg functional provides all possible patterns generated under irradiation and the solubility limits of radiation-induced precipitates in these patterns. To rationalize the formation of these radiation-induced patterns, we propose a generic “pseudophase diagram” that relies not only on the irradiation flux and temperature but also on the overall composition of the alloy. Tuning this overall composition offers the opportunity to tailor new materials with various micro-structures overcoming the limitation of the equilibrium phase diagram. © 2019 Author(s). Published under license by AIP Publishing.