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Energetics of Al doping and intrinsic defects in monoclinic and cubic zirconia: First-principles calculations
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
2009 (Engelska)Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, nr 11, s. 115208-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

First-principles theory within the supercell approach has been employed to investigate Al doping and intrinsic defects in monoclinic and cubic zirconia. The effect of oxygen chemical potential and Fermi level on the formation energy and on the defect concentration have been taken into account. The formation of oxygen vacancies is found to be energetically more favorable in the cubic than in the monoclinic phase under the same oxygen chemical potential and Fermi energy. In both phases, substitutional Al decays from neutral charge state into the charge state -1, with the transition energy just above to the top of the valence band. Our findings indicate that by confining the Fermi energy to the region between the middle of the band gap and the bottom of the conduction band, high Al solubility could be achieved, although formation of Al is likely followed by the formation of interstitial oxygen. Furthermore, the concentration of Al with charge state -1 along with the equilibrium Fermi energy have been calculated in a self-consistent procedure. Here, the possible compensating defects with the relevant charge states have been considered. The obtained concentrations of Al and oxygen vacancies follow the experimental trend but underestimates experimental data. When the formation of defect clusters, composed by two substitutional Al and one oxygen vacancy, are considered, good quantitative agreement with experimental values of both Al and oxygen vacancy concentration is achieved. The results suggest that defect clusters will be formed as a result of Al doping in cubic phase of ZrO2, whereas the concentration of defect clusters is negligible in the monoclinic phase, both in accordance with experiment.

Ort, förlag, år, upplaga, sidor
2009. Vol. 80, nr 11, s. 115208-
Nyckelord [en]
GENERALIZED GRADIENT APPROXIMATION, SYSTEM, ZRO2, ZRO2-AL2O3, DEPOSITION
Nationell ämneskategori
Materialteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-10160DOI: 10.1103/PhysRevB.80.115208ISI: 000270383200066Scopus ID: 2-s2.0-70350584532OAI: oai:DiVA.org:kth-10160DiVA, id: diva2:209769
Anmärkning
QC 20100913. Uppdaterad från Submitted till Published (20100913)Tillgänglig från: 2009-03-27 Skapad: 2009-03-27 Senast uppdaterad: 2017-12-13Bibliografiskt granskad
Ingår i avhandling
1. Study of solid oxide systems from first principles calculations: energetics and magnetic properties of native defects and dopants in ZrO2 and MgO
Öppna denna publikation i ny flik eller fönster >>Study of solid oxide systems from first principles calculations: energetics and magnetic properties of native defects and dopants in ZrO2 and MgO
2009 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2009. s. v, 33
Serie
KTH/MSE--09/02
Identifikatorer
urn:nbn:se:kth:diva-10168 (URN)978-91-7415-202-9 (ISBN)
Presentation
2009-02-23, Rum K408, KTH, Brinellvägen 23, Stockholm, 13:15 (Engelska)
Handledare
Anmärkning
QC 20101108Tillgänglig från: 2009-03-27 Skapad: 2009-03-27 Senast uppdaterad: 2010-11-08Bibliografiskt granskad
2. Atomistic modelling of functional solid oxides for industrial applications: Density Functional Theory, hybrid functional and GW-based studies
Öppna denna publikation i ny flik eller fönster >>Atomistic modelling of functional solid oxides for industrial applications: Density Functional Theory, hybrid functional and GW-based studies
2011 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In this Thesis a set of functional solid oxides for industrial applications have been addressed by first principles and thermodynamical modelling. More specificially, measurable quantities such as Gibbs free energy, geometry and electronic structure have been calculated and compared when possible with experimental data. These are crystalline and amorphous aluminum oxide (Al2O3), Zirconia (ZrO2), magnesium oxide (MgO), indiumoxide (In2O3) and Kaolinite clay (Al2Si2O5(OH)4).

The reader is provided a computation tool box, which contains a set of methods to calculate properties of oxides that are measurable in an experiment. There are three goals which we would like to reach when trying to calculate experimental quantities. The first is verification. Without verification of the theory we are utilizing, we cannot reach the second goal -prediction. Ultimately, this may be (and to some extent already is) the future of first principles methods, since their basis lies within the fundamental quantum mechanics and since they require no experimental input apart from what is known from the periodic table. Examples of the techniques which may provide verification are X-Ray Diffraction (XRD), X-ray Absorption and Emission Spectroscopy (XAS and XES), Electron Energy Loss Spectroscopy and Photo-Emission Spectroscopy (PES). These techniques involve a number of complex phenomena which puts high demands on the chosen computational method/s. Together, theory and experiment may enhance the understanding of materials properties compared to the standalone methods. This is the final goal which we are trying to reach -understanding. When used correctly, first principles theory may play the role of a highly resolved analysis method, which provides details of structural and electronic properties on an atomiclevel. One example is the use of first principles to resolve spectra of multicomponentsamples. Another is the analysis of low concentrations of defects. Thorough analysis of the nanoscale properties of products might not be possible in industry due to time and cost limitations. This leads to limited control of for example low concentrations of defects, which may still impact the final performance of the product. On example within cutting tool industry is the impact of defect contents on the melting point and stability of protective coatings. Such defects could be hardening elements such as Si, Mn, S, Ca which diffuse from a steel workpiece into the protective coating during high temperature machining. Other problems are the solving of Fe from the workpiece into the coating and reactions between iron oxide, formed as the workpiece surface is oxidized, and the protective coating.

The second part of the computational toolbox which is provided to the reader is the simulation of solid oxide synthesis. Here, a formation energy formalism, most often applied to materials intended in electronics devices is applied. The simulation of Chemical Vapour Deposition (CVD) and Physical Vapor Deposition (PVD) requires good knowledge of the experimental conditions, which can then be applied in the theoretical simulations. Effects of temperature, chemical and electron potential, modelled concentration and choice of theoretical method on the heat of formation of different solid oxides with and without dopants are addressed in this work. A considerable part of this Thesis is based upon first principles calculations, more specifically, Density Functional Theory (DFT) After Kohn and Pople received the Nobel Prize in chemistry in 1998, the use of DFT for computational modelling has increased strikingly (see Fig. 1). The use of other first principles methods such as hybrid functionals and the GW approach (see abbreviations for short explanations and chapter 4.5 and 5.3.) have also become increasingly popular, due to the improved computational resources. These methods are also employed in this Thesis.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2011
Nyckelord
density functional theory, oxides, GW
Nationell ämneskategori
Den kondenserade materiens fysik Den kondenserade materiens fysik Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:kth:diva-29257 (URN)978-91-7415-868-7 (ISBN)
Disputation
2011-02-18, F3, Lindstedsvägen 26, KTH, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning
QC 20110201Tillgänglig från: 2011-02-01 Skapad: 2011-01-28 Senast uppdaterad: 2012-03-28Bibliografiskt granskad

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Århammar, CeciliaMoysés Araújo, C.Ahuja, Rajeev
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