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Redox properties of CeO2-MO2 MO2 (M=Ti, Zr, Hf or Th) solid solutions from first principles calculations
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
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2007 (Engelska)Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, nr 3, s. 031909-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The authors have used density functional theory calculations to investigate how the redox thermodynamics and kinetics of CeO2 are influenced by forming solid solutions with TiO2, ZrO2, HfO2, and ThO2. Reduction is facilitated by dissolving TiO2 (largest improvement), HfO2, or ZrO2 (least improvement), while ThO2 makes reduction slightly more difficult. The migration barrier is much lower in the neighborhood of a Ti (largest decrease), Hf, or Zr (least decrease), while the binding energy of solute ions and vacancies increases in the same sequence. They rationalize the properties of ceria solid solutions in terms of defect cluster relaxations.

Ort, förlag, år, upplaga, sidor
2007. Vol. 90, nr 3, s. 031909-
Nationell ämneskategori
Övrig annan teknik
Identifikatorer
URN: urn:nbn:se:kth:diva-6889DOI: 10.1063/1.2431775ISI: 000243582400031Scopus ID: 2-s2.0-33846459357OAI: oai:DiVA.org:kth-6889DiVA, id: diva2:11729
Anmärkning
QC 20100622Tillgänglig från: 2007-03-14 Skapad: 2007-03-14 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. From the Electronic Structure of Point Defects to Functional Properties of Metals and Ceramics
Öppna denna publikation i ny flik eller fönster >>From the Electronic Structure of Point Defects to Functional Properties of Metals and Ceramics
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Point defects are an inherent part of crystalline materials and they influence important physical and chemical properties, such as diffusion, hardness, catalytic activity and phase stability. Increased understanding of point defects enables us to tailor the defect-related properties to the application at hand. Modeling and simulation have a prominent role in acquiring this knowledge. In this thesis thermodynamic and kinetic properties of point defects in metals and ceramics are studied using first-principles calculations based on density functional theory. Phenomenological models are used to translate the atomic level properties, obtained from the first-principles calculations, into functional materials properties. The next paragraph presents the particular problems under study.

The formation and migration of vacancies and simple vacancy clusters in copper are investigated by calculating the energies associated with these processes. The structure, stability and electronic properties of the low-oxygen oxides of titanium, TiOx with 1/3 < x < 3/2, are studied and the importance of structural vacancies is demonstrated. We develop an integrated first-principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on vacancy-induced ordering of the substoichiometric

carbonitride phase, TiCxNy (x+y < 1). The possibility of forming higher oxides of plutonium than plutonium dioxide is explored by calculating the enthalpies for nonstoichiometric defect-containing compounds and the analysis shows that such oxidation is only produced by strong oxidants. For ceria (CeO2) doped with trivalent ions from the lanthanide series we probe the connection between the choice of a dopant and the improvement of ionic conductivity by studying the oxygen-vacancy formation and migration properties. The significance of minimizing the dopant-vacancy interactions is highlighted. We investigate the redox thermodynamics of CeO2-MO2 solid solutions with M being Ti, Zr, Hf, Th, Si, Ge, Sn or Pb and show that reduction is facilitated by small solutes.

The results in this thesis are relevant for the performance of solid electrolytes, which are an integral part of solid oxide fuel cells, oxygen storage materials in automotive three-way catalysts, nuclear waste materials and cutting tool materials.

Ort, förlag, år, upplaga, sidor
Stockholm: Materialvetenskap, 2007
Nyckelord
first principles, ab initio, density functional theory, Calphad, point defects, diffusion, solid electrolytes, oxygen storage materials
Nationell ämneskategori
Övrig annan teknik
Identifikatorer
urn:nbn:se:kth:diva-4309 (URN)978-91-7178-590-9 (ISBN)
Disputation
2007-03-30, F2, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20100622Tillgänglig från: 2007-03-14 Skapad: 2007-03-14 Senast uppdaterad: 2012-03-22Bibliografiskt granskad

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Andersson, David A.Johansson, Börje
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