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Theoretical and experimental studies of ternary and quaternary nitrides for machining and thermoelectric materials
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0001-5670-7644
2019 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Teoretiska och experimentella studier av ternära och kvarternära nitrider för metallbearbetning och termoelektriska material (Swedish)
Abstract [en]

Nitrides are used as coatings and thin films for a wide range of applications. The study and use of nitrides in the recent decades have shifted towards ternary, quaternary or even higher order (complex) nitrides. There is an interest to use ternary and quaternary nitrides for machining and thermoelectric materials, because it gives the possibility to choose composition and thereby design the materials properties. This thesis presents research results on TiAlN and and TiAlN-based coatings that are used as hard coatings for machining and on ternary scandium nitrides that are of interest for thin films for thermoelectric applications. The high-pressure high-temperature behavior of cubic TiAlN deposited on cubic boron nitride has been experimentally studied. It has been shown that the spinodal decomposition, which means decomposition into cubic domains enriched in TiN and AlN, is delayed as a result of high pressure compared to ambient pressure. No chemical interaction between coating and substrate occurs. TiZrAlN has been theoretically and experimentally studied at high temperature. The results show that the when Zr-content is decreased and the Al-content is increased the decomposition route changes from nucleation and growth to spinodal decomposition. The microstructure evolution with temperature depends on the initial composition. In the case where the decompositon starts with only spinodal decomposition the microstructure at 1100 °C consists of domains that are larger than in the case where the decomposition occurs by nucleation and growth. ScMN2 (M=V, Nb, Ta) phases have been experimentally demonstrated for M=Nb and Ta in a few studies, but have not been much investigated. In this theseis, their crystal structure, stability, elastic properties, electronic structure and thermoelectric properties have been studied. At 0 K and 0 GPa it has been shown that these three phases are thermodynamically and elastically stable. Additionally, these are narrow-bandgap semiconductors and their thermoelectric properties can be tuned by doping. Pressure has a stabilizing effect on these structures. When pressure increases from 0-150 GPa the elastic constants and moduli increases in the range 53-317 %.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. , p. 50
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1983
Keywords [en]
materials science; thin film physics; nitrides, machining; thermoelectrics
Keywords [sv]
materialvetenskap; tunnfilmsfysik; nitrider; metallbearbetning; termoelektricitet
National Category
Condensed Matter Physics Ceramics Other Materials Engineering
Identifiers
URN: urn:nbn:se:liu:diva-155101DOI: 10.3384/diss.diva-155101ISBN: 9789176851142 (print)OAI: oai:DiVA.org:liu-155101DiVA, id: diva2:1301744
Public defence
2019-06-05, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2019-04-02 Created: 2019-04-02 Last updated: 2019-10-16Bibliographically approved
List of papers
1. High temperature phase decomposition in TixZryAlzN
Open this publication in new window or tab >>High temperature phase decomposition in TixZryAlzN
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2014 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 4, no 12, p. 127147-1-127147-9Article in journal (Refereed) Published
Abstract [en]

Through a combination of theoretical and experimental observations we study the high temperature decomposition behavior of c-(TixZryAlzN) alloys. We show that for most concentrations the high formation energy of (ZrAl)N causes a strong tendency for spinodal decomposition between ZrN and AlN while other decompositions tendencies are suppressed. In addition we observe that entropic  effects due to configurational disorder favor a formation of a stable Zr-rich (TiZr)N phase with increasing temperature. Our calculations also predict that at high temperatures a Zr rich (TiZrAl)N disordered phase should become more resistant against the spinodal decomposition despite its high and positive formation energy due to the specific topology of the free energy surface at the relevant concentrations. Our experimental observations confirm this prediction by showing strong tendency towards decomposition in a Zr-poor sample while a Zr-rich alloy shows a greatly reduced decomposition rate, which is mostly attributable to binodal decomposition processes. This result highlights the importance of considering the second derivative of the free energy, in addition to its absolute value in predicting decomposition trends of thermodynamically unstable alloys.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-110682 (URN)10.1063/1.4905138 (DOI)000347170100078 ()
Note

On the day of the defence date the status of this article was Manuscript.

Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2020-03-19Bibliographically approved
2. Decomposition routes and strain evolution in arc deposited TiZrAlN coatings
Open this publication in new window or tab >>Decomposition routes and strain evolution in arc deposited TiZrAlN coatings
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2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 779, p. 261-269Article in journal (Refereed) Published
Abstract [en]

Phase, microstructure, and strain evolution during annealing of arc deposited TiZrAlN coatings are studied using in situ x-ray scattering and ex situ transmission electron microscopy. We find that the decomposition route changes from nucleation and growth of wurtzite AlN to spinodal decomposition when the Zr-content is decreased and the Al-content increases. Decomposition of Ti0.31Zr0.24Al0.45N results in homogeneously distributed wurtzite AlN grains in a cubic, dislocation-dense matrix of TiZrN consisting of domains of different chemical composition. The combination of high dislocation density, variation of chemical composition within the cubic grains, and evenly distributed wurtzite AlN grains results in high compressive strains, -1.1%, which are retained after 3 h at 1100 degrees C. In coatings with higher Zr-content, the strains relax during annealing above 900 degrees C due to grain growth and defect annihilation. (C) 2018 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Ti-Zr-Al-N; Hard coatings; Thermal stability; Strain evolution
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:liu:diva-154526 (URN)10.1016/j.jallcom.2018.11.039 (DOI)000457154700032 ()
Note

Funding Agencies|VINNOVA (Swedish Governmental Agency for Innovation Systems) [2016-05156]; Swedish Government Strategic Research Area (SFO Mat LiU) [2009 00971]; Swedish Research Council [2017-03813]; Rontgen-Angstrom Cluster frame grants [VR 2011-6505, VR 2017-06701]

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2020-03-19
3. Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN2-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations
Open this publication in new window or tab >>Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN2-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations
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2019 (English)In: Condensed Matter, ISSN 2410-3896, Vol. 4, no 2, article id 36Article in journal (Refereed) Published
Abstract [en]

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but they have up to now not been much studied. However, based on the properties of binary ScN and its alloys, it is reasonable to expect these phases to be of relevance in a range of applications, including thermoelectrics. Here, we have used first-principles calculations to study their thermodynamic stability, elastic, thermoelectric and electronic properties. We have used density functional theory to calculate lattice parameters, the mixing enthalpy of formation and electronic density of states as well as the thermoelectric properties and elastic constants (cij), bulk (B), shear (G) and Young’s (E) modulus, which were compared with available experimental data. Our results indicate that the considered systems are thermodynamically and elastically stable and that all are semiconductors with small band gaps. All three materials display anisotropic thermoelectric properties and indicate the possibility to tune these properties by doping. In particular, ScVN2, featuring the largest band gap exhibits a particularly large and strongly doping-sensitive Seebeck coefficient.

Place, publisher, year, edition, pages
Basel: MDPI, 2019
Keywords
ScTaN2; inverse MAX phase; thermoelectric properties; density functional theory
National Category
Physical Sciences Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-156671 (URN)10.3390/condmat4020036 (DOI)000475286700002 ()
Note

Funding agencies: Swedish Research Council (VR) [2016-03365]; Knut and AliceWallenberg Foundation through the Academy Fellows Program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; European Res

Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-07-30Bibliographically approved
4. Effects of high pressure on ScMN2-type (M = V, Nb, Ta) phases studied by density functional theory
Open this publication in new window or tab >>Effects of high pressure on ScMN2-type (M = V, Nb, Ta) phases studied by density functional theory
2019 (English)In: Results in Physics, ISSN 2211-3797, Vol. 13, article id 102293Article in journal (Refereed) Published
Abstract [en]

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but their high-pressure properties have not been studied. Here, we have used first-principles calculations to study their thermodynamic stability, elastic and electronic properties at high-pressure. We have used density functional theory to calculate the formation enthalpy relative to the competing binary phases, electronic density of states and elastic constants (c(ij)), bulk (B), shear (G) and Youngs (E) modulus as the pressure is varied from 0 to 150 GPa. Our results show that when the pressure increases from 0 to 150 GPa, elastic constants, bulk, shear and elastic moduli increase in the range 53-216% for ScTaN2, 72-286% for ScNbN2, and 61-317% for ScVN2.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
ScTaN2; Inverse MAX phase; High pressure; Density functional theory
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-159276 (URN)10.1016/j.rinp.2019.102293 (DOI)000476618700182 ()
Note

Funding Agencies|Swedish Research Council (VR) [2016-03365]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-10-16Bibliographically approved
5. The Effect of Point Defects on the Electronic Density of States of ScMN2-Type (M = V, Nb, Ta) Phases
Open this publication in new window or tab >>The Effect of Point Defects on the Electronic Density of States of ScMN2-Type (M = V, Nb, Ta) Phases
2019 (English)In: Condensed Matter, ISSN 2410-3896, Vol. 4, no 3, article id 70Article in journal (Refereed) Published
Abstract [en]

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb. They are narrow-bandgap semiconductors with potentially interesting thermoelectric properties. Point defects such as dopants and vacancies largely affect these properties, motivating the need to investigate these effects. In particular, asymmetric peak features in the density of states (DOS) close to the highest occupied state is expected to increase the Seebeck coefficient. Here, we used first principles calculations to study the effects of one vacancy or one C, O, or F dopant on the DOS of the ScMN2 phases. We used density functional theory to calculate formation energy and the density of states when a point defect is introduced in the structures. In the DOS, asymmetric peak features close to the highest occupied state were found as a result of having a vacancy in all three phases. Furthermore, one C dopant in ScTaN2, ScNbN2, and ScVN2 implies a shift of the highest occupied state into the valence band, while one O or F dopant causes a shift of the highest occupied state into the conduction band.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
ScTaN2; YNbN2; inverse MAX phase; point defect; density of states
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-160948 (URN)10.3390/condmat4030070 (DOI)000487966200001 ()
Note

Funding agencies: Swedish Research Council (VR)Swedish Research Council [2016-03365]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping U

Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-11-04Bibliographically approved

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Theoretical and experimental studies of ternary and quaternary nitrides for machining and thermoelectric materials(1806 kB)219 downloads
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