Journal Article FZJ-2016-07359

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Composition dependent order-disorder transition in Nd$_{x}$Zr$_{1−x}$O$_{2−0.5x}$ pyrochlores: A combined structural, calorimetric and ab initio modeling study

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2017
Elsevier Science Amsterdam [u.a.]

Acta materialia 125, 166 - 176 () [10.1016/j.actamat.2016.11.059]

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Abstract: The order-disorder phase transition in the NdxZr1−xO2−0.5x system is studied by complementary techniques which include wet chemical synthesis of a series of compositions with various Nd/Zr ratios with the final annealing at 1873 K, X-ray diffraction, oxide melt solution calorimetry and ab initio thermodynamic modeling. Our structural data indicate the transition from ordered to disordered pyrochlore at x ∼0.31 at a temperature of 1873 K. Our calorimetric data show a transition enthalpy of ∼30 kJ/mol, which corresponds to an entropy of disordering of ∼16 J/K/mol. The latter value is significantly smaller than the configurational entropy of transition computed under the assumption of complete disorder in a fluorite phase, indicating a substantial degree of order remaining in the fluorite phase at the temperature of synthesis. The considered phases are computed ab initio using a series of special quasi-random structures that emulate the complete or partial disorder. The results of our calculations and thermodynamic modeling are in good agreement with the measured lattice parameters, the Nd content at the order-disorder transition, and the measured formation and transformation enthalpies. Thus our combined experimental and modeling results provide valuable insight into the disordering of this pyrochlore phase and of other pyrochlore materials.

Classification:

Contributing Institute(s):
  1. Nukleare Entsorgung und Reaktorsicherheit (IEK-6)
  2. JARA - HPC (JARA-HPC)
Research Program(s):
  1. 161 - Nuclear Waste Management (POF3-161) (POF3-161)
  2. Investigation of the new materials for safe management of high level nuclear waste. (jiek61_20131101) (jiek61_20131101)
  3. Investigation of the new materials for safe management of high level nuclear waste. (jara0038_20121101) (jara0038_20121101)
  4. Towards controlled QCD transport coefficients (jara0039_20121101) (jara0039_20121101)

Appears in the scientific report 2017
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Medline ; Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF >= 5 ; JCR ; No Authors Fulltext ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection
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Dokumenttypen > Aufsätze > Zeitschriftenaufsätze
JARA > JARA > JARA-JARA\-HPC
Institutssammlungen > IFN > IFN-2
Workflowsammlungen > Öffentliche Einträge
IEK > IEK-6
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