Download or read book Electron and Phonon Transport in Disordered Thermoelectric Materials written by Simon Thébaud and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decades, the increasingly pressing need for clean energy sources and the realization that a huge proportion of the world energy consumption is wasted in heat have prompted great interest in developing efficient thermoelectric generation modules. These devices could harvest waste heat from industrial processes or other sources, turning a temperature gradient into a voltage through the Seebeck effect. Efficient thermoelectric materials should exhibit a low thermal conductivity, a high electrical conductivity and a high Seebeck coefficient. Simultaneously optimizing these parameters is a great challenge of condensed matter physics and materials science. With a view to enhance the thermoelectric properties of several promising materials, we explore several strategies in which defects (atomic substitutions, vacancies...), disorder and dimensional confinement play a crucial role. We perform density functional theory calculations and projections on Wannier orbitals to construct realistic Hamiltonians and dynamical matrices describing their electronic and vibrational structure in real space. These parameters are then used to compute the thermoelectric transport properties using the Kubo formalism, the Boltzmann transport equation, the Landauer formalism, and the Chebyshev polynomial Green's function method that allows for an exact treatment of disorder. We investigate the electronic transport properties and thermoelectric performances of two promising materials for high-temperature power generation, strontium titanate and rutile titanium dioxide. Comparison of our predictions with a wealth of experimental data yields a very good agreement. We show that the increase of the Seebeck coefficient observed in strontium titanate superlayers, until now attributed to quantum confinement effects, is in fact well explained assuming delocalized electrons. The general effects of resonant states on electronic transport are explored in a model study, showing a sixfold increase of the thermoelectric performances. The particular case of strontium titanate is then examined, and localization effects are shown to destroy the performances if Vanadium atoms are introduced as resonant impurities. The influence of defects in two-dimensional materials is investigated. Contrary to adatoms, substitutions in transition metal dichalcogenides are shown to localize the charge carriers. We study the effect of vacancies on phonon transport in graphene, and determine the phonon-vacancy scattering rate. Comparison with thermal conductivity data for irradiated and finite-size graphene samples yields a very good agreement between theory and experiments.

Download or read book Nanoscale Thermal and Thermoelectric Energy Transport in Crystalline and Disordered Materials written by Jiawei Zhou and published by . This book was released on 2019 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Energy transport provides the fundamental basis for operation of devices from transistors to solar cells. Despite past theories that successfully illustrate the principles behind the energy transport based on solid state physics, the microscopic details of the energy transport are not always clear due to the lack of tool to quantify the contribution from different degrees of freedom. Recent progress in first principles computations and development in optical characterization has offered us new ways to understand the energy transport at the nanoscale in a quantitative way. In this thesis, by leveraging these techniques, we aim to providing a detailed understanding of thermal and thermoelectric energy transport in crystalline and disordered materials, especially about how the energy transport depends on atomistic level details such as chemical bondings. Specifically, we will discuss three examples. 1) Electron transport in semiconductors: how electrons propagate as they interact with lattice and impurities. 2) Interaction between charge and heat: how the free carriers have an impact on the heat dissipation in semiconductors 3) Heat conduction in polymers: how the heat transfer in an amorphous system depends on its molecular structures. In the case of electron transport, we developed and applied first principles simulation to show that a large electron mobility can benefit from symmetry-protected non-bonding orbitals. Such orbitals result in weak electron-lattice coupling that explains the unusually large power factors in half-Heusler materials - a good thermoelectric material system. By devising an optical experiment to probe the ultrafast thermal decay, we quantified the effect of electron-phonon interaction on the thermal transport. Our results show that the thermal conductivity can be significantly affected by the free carriers. Lastly, we built a theoretical model to understand the heat conduction in amorphous polymers, and used this knowledge to design materials that are heat-conducting yet soft. These understandings will potentially facilitate discovery of new material systems with beneficial charge and heat transport characteristic.

Download or read book Theory and Simulation Methods for Electronic and Phononic Transport in Thermoelectric Materials written by Neophytos Neophytou and published by . This book was released on 2020 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces readers to state-of-the-art theoretical and simulation techniques for determining transport in complex band structure materials and nanostructured-geometry materials, linking the techniques developed by the electronic transport community to the materials science community. Starting from the semi-classical Boltzmann Transport Equation method for complex band structure materials, then moving on to Monte Carlo and fully quantum mechanical models for nanostructured materials, the book addresses the theory and computational complexities of each method, as well as their advantages and capabilities. Presented in language that is accessible to junior computational scientists, while including enough detail and depth with regards to numerical implementation to tackle modern research problems, it offers a valuable resource for computational scientists and postgraduate researchers whose work involves the theory and simulation of electro-thermal transport in advanced materials.

Download or read book First Principles Studies of Phonons and Electrons in Bulk Thermoelectrics written by Yi Xia and published by . This book was released on 2016 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermoelectric materials, which enable direct conversion between thermal and electrical energy, provide an alternative for power generation and refrigeration. The key parameter that defines the efficiency of thermoelectric materials is the 'dimensionless figure of merit' ZT, which is composed of the Seebeck coefficient, electrical conductivity and total thermal conductivity respectively. Ideally, to achieve high ZT both the Seebeck coefficient and electrical conductivity should be large, while total thermal conductivity must be minimized. In this thesis, first-principles calculations of the Seebeck coefficient, lattice thermal conductivity and electrical conductivity are performed to study mechanisms and factors that gives rise to high ZT. One effective way to enhance ZT is through direct reduction of lattice thermal conductivity. We perform calculation and analysis of lattice thermal conductivity for thermoelectric materials by solving the Boltzmann transport equation iteratively in the framework of perturbation theory. The second- and third-order interatomic force constants are extracted using the recently developed CSLD (compressive sensing lattice dynamics) method. Afterwards, we evaluate opportunities to achieve further reduction of lattice thermal conductivity. Our first study of ternary zinc-blende-based mineral compounds famatinite (Cu3SbS4) and permingeatite (Cu3SbSe4) shows that optical modes in these two compounds contribute a sizable portion of the total lattice thermal conductivity and thus cannot be neglected. Due to the fact that phonon modes with mean free paths larger than 10 nm carry about 80% of the heat, nanostructuring, which reduces the mean free path, is a promising way to reduce the lattice thermal conductivity by reducing the characteristic length. In addition, our simple alloying model including mass disorder reproduces experimental findings that forming solid solutions rapidly decreases the lattice thermal conductivity. An alternative way to reduce lattice thermal conductivity is to introduce guest atoms in host cage structures. Our study of type-I Si clathrates containing guest atoms Na and Ba shows that Na tends to form incoherent localized phonon mode while Ba coherently couples with the host cages. The low lattice thermal conductivities of Na- and Ba-filled Si clathrates should be attributed to the dramatic reductions in both phonon lifetime and group velocity. Analysis of phonon scattering process reveals that localized modes can be effectively emitted and absorbed, thus dramatically enhancing overall scattering rates. Another widely adopted approach to achieve high ZT is through maintaining a high power factor. To accurately determine the Seebeck coefficient and electrical conductivity, we estimate carrier lifetime due to electron-phonon interaction under relaxation time approximation using the electron-phonon Wannier interpolation technique. Our study of noble metals Cu and Ag shows that their positive Seebeck coefficients can be mostly attributed to the negative energy dependence of carrier lifetime. In contrast to the previous study of positive Seebeck in Li, which is due to the deviation of electronic behavior from that in free electron model, it is the nontrivial energy dependence of electron-phonon interaction vertex that leads to the positive Seebeck coefficient. Intermetallic compound B20-type CoSi has drawn considerable attention due to its exceptionally high power factor and large Seebeck coefficient. Our study shows that the large negative Seebeck coefficient of the pristine CoSi is mostly due to the strong energy dependence of carrier lifetime, which together with the high electrical conductivity leads to the high power factor. For heat transport, both electron-phonon and phonon-phonon interactions contribute significantly to phonon scattering at temperatures lower than 200 K. While at temperatures higher than 300 K, phonon-phonon interaction dominates over electron-phonon interaction. Based on the optimized power factor with properly adjusted carrier concentration, we predict that the maximum ZTs at 300 and 600 K are about 0.11 and 0.25 respectively without further reducing the total thermal conductivity. Known good thermoelectric materials often are comprised of elements that are in low abundance, toxic and require careful doping and complex synthesis procedures. High performance thermoelectricity has been reported in earth-abundant compounds based on natural mineral tetrahedrite (Cu12Sb4S13). Our first-principles electronic structure calculations of Cu12Sb4S13 show that Cu atoms are all in the monovalent state, creating two free hole states per formula unit of the pristine compound. Optimal thermoelectric performance can be achieved via electron doping. Substituting transition metals on Cu 12d sites does the job. Detailed analysis shows that Zn and Fe substitutions tend to fill the empty hole states, while Ni substitution introduces an additional hole to the valence band by forming ferromagnetic configuration. Experimentally observed extremely low lattice thermal conductivity can be attributed to the out-of-plane vibrations of the three-fold Cu ions. This is further verified by the large Gruneisen parameter calculated.

Download or read book Thermoelectricity and Advanced Thermoelectric Materials written by Ranjan Kumar and published by Woodhead Publishing. This book was released on 2021-06-03 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermoelectricity and Advanced Thermoelectric Materials reviews emerging thermoelectric materials, including skutterudites, clathrates, and half-Heusler alloys. In addition, the book discusses a number of oxides and silicides that have promising thermoelectric properties. Because 2D materials with high figures of merit have emerged as promising candidates for thermoelectric applications, this book presents an updated introduction to the field of thermoelectric materials, including recent advances in materials synthesis, device modeling, and design. Finally, the book addresses the theoretical difficulties and methodologies of computing the thermoelectric properties of materials that can be used to understand and predict highly efficient thermoelectric materials. This book is a key reference for materials scientists, physicists, and engineers in energy. Reviews the most relevant, emerging thermoelectric materials, including 2D materials, skutterudites, clathrates and half-Heusler alloys Focuses on how electronic structure engineering can lead to improved materials performance for thermoelectric energy conversion applications Includes the latest advances in the synthesis, modeling and design of advanced thermoelectric materials

Download or read book Advanced Thermoelectrics written by Zhifeng Ren and published by CRC Press. This book was released on 2017-11-06 with total page 790 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview on nanostructured thermoelectric materials and devices, covering fundamental concepts, synthesis techniques, device contacts and stability, and potential applications, especially in waste heat recovery and solar energy conversion. The contents focus on thermoelectric devices made from nanomaterials with high thermoelectric efficiency for use in large scale to generate megawatts electricity. Covers the latest discoveries, methods, technologies in materials, contacts, modules, and systems for thermoelectricity. Addresses practical details of how to improve the efficiency and power output of a generator by optimizing contacts and electrical conductivity. Gives tips on how to realize a realistic and usable device or module with attention to large scale industry synthesis and product development. Prof. Zhifeng Ren is M. D. Anderson Professor in the Department of Physics and the Texas Center for Superconductivity at the University of Houston. Prof. Yucheng Lan is an associate professor in Morgan State University. Prof. Qinyong Zhang is a professor in the Center for Advanced Materials and Energy at Xihua University of China.

Download or read book Theory and Simulation Methods for Electronic and Phononic Transport in Thermoelectric Materials written by Neophytos Neophytou and published by Springer Nature. This book was released on 2020-03-16 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces readers to state-of-the-art theoretical and simulation techniques for determining transport in complex band structure materials and nanostructured-geometry materials, linking the techniques developed by the electronic transport community to the materials science community. Starting from the semi-classical Boltzmann Transport Equation method for complex band structure materials, then moving on to Monte Carlo and fully quantum mechanical models for nanostructured materials, the book addresses the theory and computational complexities of each method, as well as their advantages and capabilities. Presented in language that is accessible to junior computational scientists, while including enough detail and depth with regards to numerical implementation to tackle modern research problems, it offers a valuable resource for computational scientists and postgraduate researchers whose work involves the theory and simulation of electro-thermal transport in advanced materials.

Download or read book The Physics of Phonons written by Gyaneshwar P. Srivastava and published by Routledge. This book was released on 2019-07-16 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: There have been few books devoted to the study of phonons, a major area of condensed matter physics. The Physics of Phonons is a comprehensive theoretical discussion of the most important topics, including some topics not previously presented in book form. Although primarily theoretical in approach, the author refers to experimental results wherever possible, ensuring an ideal book for both experimental and theoretical researchers. The author begins with an introduction to crystal symmetry and continues with a discussion of lattice dynamics in the harmonic approximation, including the traditional phenomenological approach and the more recent ab initio approach, detailed for the first time in this book. A discussion of anharmonicity is followed by the theory of lattice thermal conductivity, presented at a level far beyond that available in any other book. The chapter on phonon interactions is likewise more comprehensive than any similar discussion elsewhere. The sections on phonons in superlattices, impure and mixed crystals, quasicrystals, phonon spectroscopy, Kapitza resistance, and quantum evaporation also contain material appearing in book form for the first time. The book is complemented by numerous diagrams that aid understanding and is comprehensively referenced for further study. With its unprecedented wide coverage of the field, The Physics of Phonons will be indispensable to all postgraduates, advanced undergraduates, and researchers working on condensed matter physics.

Download or read book Electron phonon Coupling and Thermal Transport in the Thermoelectric Compound Mo3Sb7 xTex written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Phonon properties of Mo3Sb7-xTex (x = 0, 1.5, 1.7), a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, and with first-principles simulations. The substitution of Te for Sb leads to pronounced changes in the electronic struc- ture, local bonding, phonon density of states (DOS), dispersions, and phonon lifetimes. Alloying with tellurium shifts the Fermi level upward, near the top of the valence band, resulting in a strong suppression of electron-phonon screening, and a large overall stiffening of interatomic force- constants. The suppression in electron-phonon coupling concomitantly increases group velocities and suppresses phonon scattering rates, surpassing the effects of alloy-disorder scattering, and re- sulting in a surprising increased lattice thermal conductivity in the alloy. We also identify that the local bonding environment changes non-uniformly around different atoms, leading to variable perturbation strengths for different optical phonon branches. The respective roles of changes in phonon group velocities and phonon lifetimes on the lattice thermal conductivity are quantified. Lastly, our results highlight the importance of the electron-phonon coupling on phonon mean-free-paths in this compound, and also estimates the contributions from boundary scattering, umklapp scattering, and point-defect scattering.

Download or read book Thermoelectrics and its Energy Harvesting 2 Volume Set written by David Michael Rowe and published by CRC Press. This book was released on 2018-10-03 with total page 1120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprising two volumes, Thermoelectrics and Its Energy Harvesting reviews the vast improvements in technology and application of thermoelectric energy with a specific intention to reduce and reuse waste heat and improve novel techniques for the efficient acquisition and use of energy.Materials, Preparation, and Characterization in Thermoelectrics i

Download or read book Materials Aspect of Thermoelectricity written by Ctirad Uher and published by CRC Press. This book was released on 2016-11-25 with total page 868 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, novel families of materials have been discovered and significant improvements in classical thermoelectric materials have been made. Thermoelectric generators are now being used to harvest industrial heat waste and convert it into electricity. This is being utilized in communal incinerators, large smelters, and cement plants. Leading car and truck companies are developing thermoelectric power generators to collect heat from the exhaust systems of gasoline and diesel engines. Additionally, thermoelectric coolers are being used in a variety of picnic boxes, vessels used to transport transplant organs, and in air-conditioned seats of mid-size cars. Consisting of twenty-one chapters written by top researchers in the field, this book explores the major advancements being made in the material aspects of thermoelectricity and provides a critical assessment in regards to the broadening of application opportunities for thermoelectric energy conversion.

Download or read book Electron phonon Coupling and Thermal Transport in the Thermoelectric Compund Mo3Sb7 xTex written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Phonon properties of Mo3Sb7-xTex (x = 0,1.5,1.7), a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, and with first-principles simulations. The substitution of Te for Sb leads to pronounced changes in the electronic structure, local bonding, phonon density of states, dispersions, and phonon lifetimes. Alloying with tellurium shifts the Fermi level upward, near the top of the valence band, resulting in a strong suppression of electron-phonon screening and a large overall stiffening of interatomic force constants. The suppression in electron-phonon coupling concomitantly increases group velocities and suppresses phonon scattering rates, surpassing the effects of alloy-disorder scattering and resulting in a surprising increased lattice thermal conductivity in the alloy. We also identify that the local bonding environment changes nonuniformly around different atoms, leading to variable perturbation strengths for different optical phonon branches. Here, changes in phonon group velocities and phonon scattering rates are quantified, highlighting the large effect of electron-phonon coupling in this compound.

Download or read book Energy Materials Discovery written by Geoffrey A Ozin and published by Royal Society of Chemistry. This book was released on 2022-06-13 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: Materials have the potential to be the centrepiece for the transition to viable renewable energy technologies if they realise a specific suite of properties and achieve a desired set of performance metrics. The envisioned transition involves the discovery of materials that enable generation, conversion, storage, transmission, and utilization of renewable energy. This book presents, through the eye of materials chemistry, an umbrella view of the myriad of classes of materials that make renewable energy technologies work. They are poised to facilitate the transition of non-renewable and unsustainable energy systems of the past into renewable and sustainable energy systems of the future. It is a story that often begins in chemistry laboratories with the discovery of new energy materials. Yet, to displace materials in existing energy technologies with new ones, depends not only on the ability to design and engineer a superior set of performance metrics for the material and the technology but also the requirement to meet a demanding collection of economic, regulatory, social, policy, environmental and sustainability criteria. Disruption in the traditional way of discovering materials is coming with the emergence of artificial intelligence, machine learning and robotic automation designed to accelerate the well-established discovery process, massive libraries of materials can be evaluated and the possibilities are endless. This book provides a perspective on the application of these new technologies to this field as well as an overview of energy materials discovery in the broader techno-economic and social context. Any budding researcher or more experienced materials scientist will find a guide to a fascinating story of discovery and emerge with a vision of what is next.

Download or read book Thermoelectric Materials written by Ken Kurosaki and published by Walter de Gruyter GmbH & Co KG. This book was released on 2020-06-08 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: How can you design good thermoelectric materials? This book covers thermoelectric material concepts and synthesis techniques in particular focusing methods for enhancing current materials designs to achieve the greatest thermoelectric efficiencies. This book is ideal for researchers and advanced students of materials science, physics, and energy.

Download or read book Thermoelectric Materials and Devices written by Lidong Chen and published by Elsevier. This book was released on 2020-09-25 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermoelectric Materials and Devices summarizes the latest research achievements over the past 20 years of thermoelectric material and devices, most notably including new theory and strategies of thermoelectric materials design and the new technology of device integration. The book's author has provided a bridge between the knowledge of basic physical/chemical principles and the fabrication technology of thermoelectric materials and devices, providing readers with research and development strategies for high performance thermoelectric materials and devices. It will be a vital resource for graduate students, researchers and technologists working in the field of energy conversion and the development of thermoelectric devices. Discusses the new theory and methods of thermoelectric materials design Combines scientific principles, along with synthesis and fabrication technologies in thermoelectric materials Presents the design optimization and interface technology for thermoelectric devices Introduces thermoelectric polymers and organic-inorganic thermoelectric composites

Download or read book Materials Preparation and Characterization in Thermoelectrics written by David Michael Rowe and published by CRC Press. This book was released on 2012-04-25 with total page 555 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes updated theoretical considerations which provide an insight into avenues of research most likely to result in further improvements in material performance. It details the latest techniques for the preparation of thermoelectric materials employed in energy harvesting, together with advances in the thermoelectric characterisation of nanoscale material. The book reviews the use of neutron beams to investigate phonons, whose behaviour govern the lattice thermal conductivity and includes a chapter on patents.

Download or read book Phonon and Electron Transport Through Interfaces and Disordered Structures written by Qichen Song (Scientist in mechanical engineering) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding phonon and electron transport is of great significance for designing efficient solid-state devices such as transistors, laser diodes and thermoelectric energy converters. The structural randomness is inevitable in solid-state devices, and it is often regarded as the undesirable scattering source for phonons and electrons. This thesis studies manipulating phonon and electron flow using structural randomness via mode-resolved Green's function calculations and pump-probe optical characterizations.