uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Phase diagram and oxygen–vacancy ordering in the CeO2–Gd2O3 system: a theoretical study
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Department of Materials Science and Engineering, KTH Royal Institute of Technology, 10044 Stockholm, Sweden.
Department of Materials Science and Engineering, KTH Royal Institute of Technology, 10044 Stockholm, Sweden;Materials Center Leoben Forschung GmbH, A-8700 Leoben, Austria.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Department of Materials Science and Engineering, KTH Royal Institute of Technology, 10044 Stockholm, Sweden.
2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 17, p. 11805-11818Article in journal (Refereed) Published
Abstract [en]

We present the phase diagram of Ce1-xGdxO2-x/2 (CGO), calculated by means of a combined Density Functional Theory (DFT), cluster expansion and lattice Monte Carlo approach. We show that this methodology gives reliable results for the whole range of concentrations (x ≡ xGd ≤ 1). In the thermodynamic equilibrium, we observe two transitions: the onset of oxygen-vacancy (O-Va) ordering at ca. 1200-3300 K for concentrations xGd = 0.3-1, and a phase separation into CeO2 and C-type Gd2O3 occurring below ca. 1000 K for all concentrations. We also model 'quenched' systems, with cations immobile below 1500 K, and observe that the presence of random-like cation configurations does not prevent C-type vacancy ordering. The obtained transition temperatures for Va ordering agree rather well with existing experimental data. We analyse the effect of vacancy ordering and composition on the lattice parameters and relaxation pattern of cations.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2018. Vol. 20, no 17, p. 11805-11818
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-353404DOI: 10.1039/c8cp01029cISI: 000431824000034PubMedID: 29658037OAI: oai:DiVA.org:uu-353404DiVA, id: diva2:1217113
Funder
Swedish Research Council, VR 348-2012-6196 2015-05538EU, European Research CouncilAvailable from: 2018-06-12 Created: 2018-06-12 Last updated: 2018-09-26Bibliographically approved
In thesis
1. Configurational Thermodynamics of the CeO2-Gd2O3 System: A Combined DFT, Cluster Expansion and Monte Carlo Approach to Bulk and Interfaces
Open this publication in new window or tab >>Configurational Thermodynamics of the CeO2-Gd2O3 System: A Combined DFT, Cluster Expansion and Monte Carlo Approach to Bulk and Interfaces
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, we study the configurational thermodynamics of Ce1-xGdxO2-x/2 x ≤ 1 or CGO. We apply a combined Density Functional Theory (DFT), cluster expansion and Monte Carlo (MC) approach in which the configurational energy of CGO is described by means of the Ising-type Hamiltonian. The interactions are determined by the cluster expansion of total energies calculated with DFT for a set of various cation–anion configurations. This allows one to perform on- the-fly calculations of the configurational energies in MC simulations of cation and anion ordering.

The cluster interactions are essentially electrostatic and long-range, and describe the configurational energetics in the entire range of concentrations rather well.

The phase diagram obtained in the MC simulations allows one to rationalise existing experimental data and is largely in agreement with that. We observe the phase separation into pure oxides, in equilibrium, below ca. 1000 K for x ≤ 1 (however it is kinetically hindered as diffusion of cations below ca. 1500 K is slow). We also observe the C-type oxygen–vacancy ordering in the x = 0.3–1 range below ca. 1200–3300 K (C phase), and a largely disordered, fluorite (F) phase in the x ≤ 0.3 range and above the ordering temperature.

The DFT supercell calculations of the F and C phase configurations obtained in MC simulations allow us to study the effect of concentration and ordering on the lattice relaxations, lattice parameter and elastic moduli, providing insights into relation between preparation conditions, structure and properties.

The bulk cluster interactions appear to be applicable also to coherent CeO2/C- type Gd2O3 interfaces, hence we examine a configurational energy landscape of the oxygen vacancy migration therein.

This combined approach can be applied to study configurational thermodynamics of similar materials as well as the influence of configurational state on ionic conductivity and other properties.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 78
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1717
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-359578 (URN)978-91-513-0434-2 (ISBN)
Public defence
2018-10-30, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, 13:12 (English)
Opponent
Supervisors
Available from: 2018-10-05 Created: 2018-09-03 Last updated: 2018-10-16

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textPubMed

Authority records BETA

Žguns, Pjotrs A.Skorodumova, Natalia V.

Search in DiVA

By author/editor
Žguns, Pjotrs A.Skorodumova, Natalia V.
By organisation
Materials Theory
In the same journal
Physical Chemistry, Chemical Physics - PCCP
Physical Chemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 9 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf