Theoretical Investigations of the Electronic, Magnetic, and Thermoelectric Properties of Transition-metal Based Compounds PDF Download
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Author: Raad Edaan Haleoot
Publisher:
ISBN:
Category : Spintronics
Languages : en
Pages : 248
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Book Description
The electronic, magnetic, and thermoelectric properties of transition-metal based compounds were investigated by using the density functional theory and Boltzmann transport formalism. It was found that the Co-based Heusler compounds and InSe monochalcogenide are among the materials that may be used for future thermoelectric devices. Furthermore, the investigation showed that the quaternary Heusler compounds, such as, CoFeYGe, where Y is Ti or Cr, are half-metallic ferromagnetic materials with full electron spin polarization. The lattice thermal conductivity (mL) was found to decrease for these alloys as the temperature increases. The present investigation indicated that the phonon optical modes have a major contribution to the total mL as compared to the acoustic modes. It was also found that these compounds can be doped as either n- or p-type thermoelectric materials. The n-type material was found to possess higher thermoelectric efficiency as compared to the p-type. The calculations showed different behaviors of CoFeCuZ (Z= Al, As, Ga, In, Pb, Sb, Si, Sn) quaternary Heusler compounds. Two compounds, with Z = Al, As showed a metallic behavior, while the compounds with Z = Ga, In, Sb, Si, and Sn showed a nearly half-metallic behavior. Only CoFeCuPb was found to exhibit a half-metallic ferromagnetic behavior with a full electron spin polarization. The thermoelectric power factor of CoFeCuPb is high at room temperature and increases at higher temperatures. In addition, doping Ý-InSe with Bi atoms at the Se sites was found to decrease its lattice thermal conductivity, which leads to an increase in its figure of merit.
Author: Raad Edaan Haleoot
Publisher:
ISBN:
Category : Spintronics
Languages : en
Pages : 248
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Book Description
The electronic, magnetic, and thermoelectric properties of transition-metal based compounds were investigated by using the density functional theory and Boltzmann transport formalism. It was found that the Co-based Heusler compounds and InSe monochalcogenide are among the materials that may be used for future thermoelectric devices. Furthermore, the investigation showed that the quaternary Heusler compounds, such as, CoFeYGe, where Y is Ti or Cr, are half-metallic ferromagnetic materials with full electron spin polarization. The lattice thermal conductivity (mL) was found to decrease for these alloys as the temperature increases. The present investigation indicated that the phonon optical modes have a major contribution to the total mL as compared to the acoustic modes. It was also found that these compounds can be doped as either n- or p-type thermoelectric materials. The n-type material was found to possess higher thermoelectric efficiency as compared to the p-type. The calculations showed different behaviors of CoFeCuZ (Z= Al, As, Ga, In, Pb, Sb, Si, Sn) quaternary Heusler compounds. Two compounds, with Z = Al, As showed a metallic behavior, while the compounds with Z = Ga, In, Sb, Si, and Sn showed a nearly half-metallic behavior. Only CoFeCuPb was found to exhibit a half-metallic ferromagnetic behavior with a full electron spin polarization. The thermoelectric power factor of CoFeCuPb is high at room temperature and increases at higher temperatures. In addition, doping Ý-InSe with Bi atoms at the Se sites was found to decrease its lattice thermal conductivity, which leads to an increase in its figure of merit.
Author: Mohammad Amin Gharavi
Publisher: Linköping University Electronic Press
ISBN: 9179299644
Category :
Languages : en
Pages : 56
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Book Description
Thermoelectricity transforms temperature gradients across thermoelectric material into an external voltage through a phenomenon known as the Seebeck effect. This property has resulted in niche applications such as solid-state cooling for electronic and optoelectronic devices which exclude the need for a coolant or any moving parts and long-lasting, maintenance-free radioisotope thermoelectric generators used for deep-space exploration. However, the high price and low efficiency of thermoelectric generators have prompted scientists to search for new materials and/or methods to improve the efficiency of the already existing ones. Thermoelectric efficiency is governed by the dimensionless figure of merit ????, which depends on the electrical conductivity, thermal conductivity and Seebeck coefficient value of the material and has rarely surpassed unity. In order to address these issues, research conducted on early transition metal nitrides spearheaded by cubic scandium nitride (ScN) thin films showed promising results with high power factors close to 3000 ?Wm?1K?2 at 500 °C. These results are the main motivation behind my thesis where the conducted research is separated into two different routes: • the synthesis and characterization of chromium nitride thin films and its alloys • the study of hypothetical ternary nitrides equivalent to scandium nitride Rock-salt cubic chromium nitride (CrN) deposited in the form of thin films by reactive magnetron sputtering was chosen for its large Seebeck coefficient of approximately -200 ?V/K and low thermal conductivity between 2 and 4 Wm?1K?1. The results show that CrN in single crystal form has a low electrical resistivity below 1 m?cm, a Seebeck coefficient value of -230 ?V/K and a power factor close to 5000 ?Wm?1K?2 at room temperature. These promising results could lead to CrN based thermoelectric modules which are cheaper and more stable compared to traditional thermoelectric material such as bismuth telluride (Bi2Te3) and lead telluride (PbTe). Although cubic CrN has been shown to be a promising material for research with a large power factor, the electrical resistivity limits applications in pure form as the ???? is estimated to be slightly below 0.5. To overcome this issue, I enhanced the thermoelectric power-factor of CrN by alloying it with a conductor, Rock-salt cubic vanadium nitride (VN). VN is a suitable choice as both materials share the same crystal structure and have almost equal lattice constants. Through deposition at 720 °C, where a small amount of VN (less than 5%) and Cr2N is introduced into the film, a reduced electrical resistivity averaged around 0.8 × 10-3 ?cm, Seebeck coefficient value of 270 ?V/K and a power-factor of 9.1 × 10-3 W/mK2 is measured at room temperature, which surpasses the thermoelectric properties of Bi2Te3. Hexagonal dichromium nitride (Cr2N) nano-inclusions increase the charge carrier concentration and act as phonon scattering sites. Single crystal Cr2N was also studied separately, as it shows interesting elastic-plastic mechanical properties and high resistance to oxidation at high temperatures for long periods of time. In the second part of this thesis, hypothetical ternary nitrides equivalent to ScN are investigated for their prospective thermoelectric properties. Scandium nitride has a relatively high thermal conductivity value (close to 10 Wm?1K?1), resulting in a low ????. A hypothetical ternary equivalent to ScN may have a similar electronic band structure and large power factor, but with a lower thermal conductivity value leading to better thermoelectric properties. Thus, the elements magnesium, titanium, zirconium, and hafnium were chosen for this purpose. DFT calculations were used to simulate TiMgN2, ZrMgN2 and HfMgN2. The results show the MeMgN2 stoichiometry to be stable, with two rivaling crystal structures: trigonal NaCrS2 and monoclinic LiUN2. The calculated electronic band structure of these compounds shows a direct band-gap for the monoclinic and an indirect band-gap for the trigonal crystal structures. These findings, coupled with predicted Seebeck coefficient values, encourages actual synthesis of such materials. DFT calculations were also used to study (Zr, Mg)N and (Hf, Mg)N alloys based on the SQS model. The transition temperature between the ordered monoclinic structure of ZrMgN2 and HfMgN2 and the disordered (Zr, Mg)N and (Hf, Mg)N alloys is calculated to be approximately 800 K and 1050 K respectively. Density of State (DoS) calculations show that similar to (Ti, Mg)N, (Zr, Mg)N and (Hf, Mg)N are also semiconducting. The thermoelectric properties of both compounds are also predicted, and that in the range of a moderate change in the Fermi level, high Seebeck coefficient values at room temperature can be achieved. Finally, in order to complete the mentioned study on hypothetical ternaries, I deposited (Ti, Mg)N thin film alloys by reactive magnetron sputtering. These films, which were deposited at 400 °C, are porous and are crystallized in the rocksalt cubic structure. As-deposited films show an electrical resistivity of 150 m?cm and a Seebeck coefficient of -25 ?V/K, which shows semiconducting properties. In order to initiate a phase transformation, these films when annealed at approximately 800 °C, where nano-inclusions of a titanium/magnesium oxynitride are formed in a LiTiO2-type superstructure are identified by XRD and TEM analysis.
Author: Joseph Francis Alward
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Book Description
Author: Isaac B. Bersuker
Publisher: John Wiley & Sons
ISBN: 0470920858
Category : Science
Languages : en
Pages : 658
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Book Description
With more than 40% new and revised materials, this second edition offers researchers and students in the field a comprehensive understanding of fundamental molecular properties amidst cutting-edge applications. Including ~70 Example-Boxes and summary notes, questions, exercises, problem sets, and illustrations in each chapter, this publication is also suitable for use as a textbook for advanced undergraduate and graduate students. Novel material is introduced in description of multi-orbital chemical bonding, spectroscopic and magnetic properties, methods of electronic structure calculation, and quantum-classical modeling for organometallic and metallobiochemical systems. This is an excellent reference for chemists, researchers and teachers, and advanced undergraduate and graduate students in inorganic, coordination, and organometallic chemistry.
Author: Kazuko Motizuki
Publisher: Springer Science & Business Media
ISBN: 3642034209
Category : Technology & Engineering
Languages : en
Pages : 142
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Book Description
This book on the magnetic properties of 3d-transition metal compounds focuses on 3d-metal pnictides. It couples experimental data with phenomenological discussions and explores how certain behaviors can be explained based on an itinerant electron picture.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Hideo Hosono
Publisher: Elsevier
ISBN: 0080463908
Category : Technology & Engineering
Languages : en
Pages : 478
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Book Description
A research project at the Tokyo Institute of Technology – dedicated to fostering innovation in the field of nanomaterials – was selected as one of the 21st Century COE (Center of Excellence) programs. The achievements of this COE program, which builds on the strong tradition of materials science in the Institute, are summarized within this book. Nanomaterials: Research Towards Applications is divided into four main parts: - Revolutionary Oxides - State-of-the-Art Polymers - Nanostructure Design for New Functions - Nanostructure Architecture for Engineering Applications - Each section consists of three or four chapters related to inorganic, organic and metallic nanomaterials
Author: Isaac B. Bersuker
Publisher: Wiley
ISBN: 9781394178896
Category : Science
Languages : en
Pages : 0
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Book Description
This book covers the theory underlying the electronic structure and properties of transition metal compounds, including physical methods of their investigation. The new edition has been thoroughly updated and incorporates many new developments and methods in the field. The content of the third edition has gone through significant changes with the entire book modified and updated to take into account the developments in the field since the last edition published, as well as based on the readers experience with the use of the book. The most significant changes are due to Chapters 5, 7, and 11. Chapter 5 has been thoroughly rewritten to take into account the fast developing methods of ab initio calculations of electronic structure of coordination compounds. Similarly, chapter 7 includes the latest developments in application of vibronic coupling and the Jahn-Teller and pseudo Jahn-Teller effects to solve coordination chemistry problems. In chapter 11, the more up-to-date views on reactivity, chemical activation, and catalysis are discussed, including the role of the pseudo Jahn-Teller effect. Additionally the questions, exercises, and problems to each chapter of the book have been reviewed and extended, and more problem solving examples are included. Similarly, additional illustrations, graphic presentations, and references have been added.
Author: Michael Bachmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 114
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Book Description
Author: Babak Anasori
Publisher: Springer Nature
ISBN: 3030190269
Category : Technology & Engineering
Languages : en
Pages : 534
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Book Description
This book describes the rapidly expanding field of two-dimensional (2D) transition metal carbides and nitrides (MXenes). It covers fundamental knowledge on synthesis, structure, and properties of these new materials, and a description of their processing, scale-up and emerging applications. The ways in which the quickly expanding family of MXenes can outperform other novel nanomaterials in a variety of applications, spanning from energy storage and conversion to electronics; from water science to transportation; and in defense and medical applications, are discussed in detail.
