Tesis sobre el tema "Thermopower"
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Koumoto, K., W. S. Seo y S. Ozawa. "Huge thermopower of porous Y_2O_3". American Institute of Physics, 1997. http://hdl.handle.net/2237/6986.
Texto completoOxley, John Paul. "Thermopower in two dimensional electron systems". Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293657.
Texto completoAbrahamson, Joel T. (Joel Theodore). "Energy storage and generation from thermopower waves". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76474.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references.
The nonlinear coupling between an exothermic chemical reaction and a nanowire or nanotube with large axial heat conduction guides a self-propagating thermal wave along the nano-conduit. The thermal conduit accelerates the wave by rapidly transporting energy to un-reacted fuel. The reaction wave induces what we term a thermopower wave, resulting in an electrical current in the same direction. At up to 7 W/g, peak power density is larger than that of many present micro-scale power sources (e.g. fuel cells, batteries) and even about seven times greater than commercial Li-ion batteries. Thermopower waves also tend to produce unipolar voltage pulses, although conventional thermoelectric theory predicts bipolar voltage. These waves also generate thermopower in excess of previous measurements in carbon nanotubes (CNTs) and therefore could increase figures of merit in a variety of thermoelectric materials. In this thesis, I have developed the theoretical framework to describe the thermal and chemical profiles of propagating reaction waves, and their electrical properties. My analysis yielded a new analytical solution for one-dimensional reaction and thermal diffusion systems with nth order kinetics that obviates many approximate or numerical approaches from the past 80 years. A generalized logistic. function describes the temperature and concentration profiles within the solid fuel and provides a solution for the wave velocity for a wide range of conditions. This approach offers new insight into such problems spanning several fields in science and engineering, including propulsion and self-propagating high temperature synthesis (SHS) of materials, as well as the dynamics of thermopower waves. Temperature and voltage measurements of thermopower waves on CNTs show that they can generate power as much as four times greater than predictions based on reference measurements of the Seebeck coefficient for static temperature gradients. We hypothesize that the excess thermopower stems from a chemical potential gradient across the CNTs. The fuel (e.g. picramide) adsorbs and dopes the CNTs ahead of the wave and desorbs and reacts behind the wave front. Furthermore, the excess thermopower depends on the mass of fuel added (relative to CNT mass), and the chemical potential difference matches the magnitude of the excess thermopower. Thus, a major conclusion of this thesis is that coupling to a chemical reaction can boost the performance of thermoelectric materials through differential doping. Thermopower waves can have well defined velocity oscillations for certain kinetic and thermal parameter values. Cyclotrimethylene-trinitramine (fuel) on multiwalled CNTs (conduit) system generates voltage oscillations of 400 to 5000 Hz. These frequencies agree with velocity oscillations predicted by my thermochemical model of the reaction wave, extended to include thermal transport within the conduits. Thermopower waves could thus find applications as new types of alternating current (AC) batteries and self-powered signal generators, which could easily be miniaturized. Microelectromechanical systems and sensors would benefit from thermopower wave generators to enable functions such as communications and acceleration that currently require large power packs. Additionally, the "self-discharge" rate of thermopower wave generators is extremely low in contrast to electrochemical storage, since their energy is stored in chemical bonds. Thermopower waves thus enable new energy storage devices and could exceed limitations of conventional thermoelectric devices.
by Joel T. Abrahamson.
Ph.D.
Isotalo, Heikki. "Thermopower in the characterization of electrically conducting polymers". [Hki] : Societas scientiarum Fennica, 1990. http://catalog.hathitrust.org/api/volumes/oclc/57960808.html.
Texto completoAnatska, Maryna Petrovna. "The transport coefficients in (R1.5Ce0.5)RuSr2Cu2O10-5 (R=Gd,Eu) rutheno-cuprates". Texas A&M University, 2006. http://hdl.handle.net/1969.1/5019.
Texto completoGibbings, C. J. "Thermoelectric properties of silicon inversion layers". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372871.
Texto completoHolland, Edward Robert. "Transport properties in electrically conductive polymeric materials". Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5233/.
Texto completoKopp, Bastian [Verfasser]. "Thermopower of Atomic-Size Contacts at Low Temperature / Bastian Kopp". Konstanz : Bibliothek der Universität Konstanz, 2016. http://d-nb.info/1115727486/34.
Texto completoSrivastava, Gauri. "Low temperature measurement of thermopower in mesoscopic normal/superconducting nanostructures". Thesis, Royal Holloway, University of London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430893.
Texto completoMahajan, Sayalee G. (Sayalee Girish). "Improving efficiency of ID thermopower wave devices and studying 2D reaction waves". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101509.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (pages 124-127).
With growing energy consumption, current research in the field is focused on improving and developing alternatives for energy storage and conversion. Factors such as efficiency of energy conversion, usability of this converted form of energy, power density, energy density etc. help us in determining the right energy source or conversion technology for any specific application. The main aim of this thesis was to study self-propagating reaction waves as a means of converting chemical energy into electrical energy. We carried out numerical simulations to study these self-propagating reaction wave systems and their heat transfer properties. Our analysis shows that for certain specific system heat transfer properties, self-propagating reaction waves can sometimes lead to superadiabatic temperatures, which are temperatures higher than the predicted adiabatic reaction temperature. Having energy available at higher temperature has advantages in heat harvesting applications such as thermoelectricity and thermophotovoltaics. We calculated the improvement in efficiency of a modified thermophotovoltaics setup, when the input is a reaction wave, operating under superadiabatic conditions. Experimentally, we studied these self-propagating reaction waves by launching I D thermopower waves. We demonstrated improved chemical-to-electrical conversion efficiency of these devices (from about 10-⁴ % to 10-² %) by operating with newer fuels such as sodium azide and sucrose with potassium nitrate on single-walled carbon nanotube-based thermal conduits. The net efficiency of operation of the device was also improved to up to 1% by using external thermoelectric harvesters to capture the heat energy lost via convection and radiation. We proposed a model combining the ID reaction heat and mass balance equations with the theory of excess thermopower to predict the output voltage profiles of thermopower wave devices and extract useful data from the voltage plots obtained experimentally. This model allows us to quantify the impact of the device-to-device variation of the fuel and thermal conduit properties, and can guide us to a better choice of fuel-thermal conduit pairs to improve the efficiency of operation. Finally, we experimentally studied 2D reaction waves. These waves were launched with a nitrocellulose fuel layer atop an aluminum foil thermal conduit. A wave front characteristic, the shape of these wave fronts, was studied as a function of heat loss. Energy released by these reactions was again harvested using external thermoelectrics to convert heat energy into electricity. We demonstrated that such a setup of 2D reaction waves can be used to illuminate a light-emitting diode (LED).
by Sayalee G. Mahajan.
Ph. D.
Crump, Paul Andrew. "Classical and quantum electrical transport in two dimensional systems". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319648.
Texto completoSparks, Taylor David. "Oxide Thermoelectrics: The Role of Crystal Structure on Thermopower in Strongly Correlated Spinels". Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10243.
Texto completoEngineering and Applied Sciences
Möller, Thomas [Verfasser]. "Temperature Dependent Study of the Thermopower of Atomic and Molecular Scale Contacts / Thomas Möller". Konstanz : KOPS Universität Konstanz, 2020. http://d-nb.info/1213247276/34.
Texto completoCole, Jody Richard. "The effect of doping on the anisotropic electrical resistivity and thermopower of YBa₂Cu₃Ox". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597825.
Texto completoOhta, Hiromichi, Yumi Masuoka, Ryoji Asahi, Takeharu Kato, Yuichi Ikuhara, Kenji Nomura y Hideo Hosono. "Field-modulated thermopower in SrTiO3-based field-effect transistors with amorphous 12CaO・7Al2O3 glass gate insulator". American Institute of Physics, 2009. http://hdl.handle.net/2237/14153.
Texto completoPopuloh, Sascha. "Investigation of the Mott transition in chromium doped V2 O3 by means of ultrasound and thermopower experiments". Paris 11, 2009. http://www.theses.fr/2009PA112044.
Texto completoThis work presents an experimental study of the high temperature Mott transition in chromium doped V2O3 by means of two different experimental techniques at pressures between ambient pressure and 6 kbar and temperatures from room T to 500 K. Ultrasound measurements as a direct probe of the compressibility were used to estimate the effects of the lattice on the Mott transition. We were able to present the first systematic study of the influence of the lattice degrees of freedom on the high temperature Mott transition in V2O3 and could verify the existence of a critical electronic temperature Telc that differs in the order of 3% or 4% from the temperature of the transition Tc of the bulk sample. Furthermore, observation of the behaviour of the transversal mode of the speed of sound allowed to conclude that this transition occurs without symmetry breaking and the order parameter is a scalar. In the second part the evolution of the Seebeck coefficient was investigated under the same experimental conditions. The studies around the critical point allowed us to establish an experimental phase diagram. Furthermore, we were able to show that the change of the Seebeck coefficient at the Mott transition is driven by the change in the resistivity rather than by the change of the particle-hole symmetry. As a consequence of this we could relate the scaling laws for the critical parameters related to conductivity to our data. In the vicinity of the transition our data were quite well reproduced by the mean field exponents found in the conductivity experiments
Böhnert, Tim [Verfasser] y Kornelius [Akademischer Betreuer] Nielsch. "Magneto-thermopower and Magnetoresistance of Co-Ni Alloy and Co-Ni/Cu Multilayered Nanowires. / Tim Böhnert. Betreuer: Kornelius Nielsch". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1052996698/34.
Texto completoOrovets, Christine M. "Search for Resonant Impurities in Bismuth and Bismuth-Antimony Alloys: Lithium, Magnesium, and Sodium". The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337715464.
Texto completoBurg, Tristan Kevin Materials Science & Engineering Faculty of Science UNSW. "Semiconducting properties of polycrystalline titanium dioxide". Publisher:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41262.
Texto completoStalaučinskas, Tadas. "Klaipėdos šiluminės elektrinės konversija į šiuolaikinį meno centrą Danės gatvėje". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100622_150120-55562.
Texto completoThe aim of the final work of MA – identify the teritory conversion opportunities of Klaipeda thermopower station, evaluating the current situation and taking the relevant research methods . Develop comercial and public infrastructure area by using architectural and urbanistical analysis and integrating it into the target –spacial structure of the city. It is suggested to empty the target area, except the buildings that have architectural and structural value. The Thermopower station is going to be the accent of the teritory and the part of town, and have a close relation with the architecture of the oldtown. Three solids composition is adopted for the function of the modern art center, where exposition spaces, conference halls, lobbies, restaurants, technical rooms are being established. Untraditional constuctive systems were adjusted to prepare this project. The work contains graphic matereal and text part: introduction, analytical part, the summary of the building data, the evaluation of the building‘s architectural and constructive technical condition, processing of the research matereal, architectural and contructive renovation suggestions, bibliography. Appedixes: graphic matereal copies, photos of the model of the project.
Köhler, Ulrike. "Thermoelectric transport in rare-earth compounds". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1215004993567-14165.
Texto completoCipiloglu, Mustafa Ali. "Thermoelectric Effects In Mesoscopic Physics". Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604753/index.pdf.
Texto completoKöhler, Ulrike. "Thermoelectric transport in rare-earth compounds". Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23707.
Texto completoPalacio, Morales Alexandra. "Thermoélectricité des composés fortement corrélés sous conditions extrêmes". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY042/document.
Texto completoThermopower is a technique whose importance is related to the possibility of directly measuring electronic properties of the systems, as it is sensitive to the derivative of the density of states. In this work, the low temperature regime of strongly correlated electron systems has been studied using this technique. For that, a new pressure-field thermopower device was developed, and used, to determine $(T,P,H)$ phase diagrams of the itinerant ferromagnets UCoAl and UGe$_2$, and of the weak antiferromagnet CeRh$_2$Si$_2$.For example, in the case of UCoAl, this same technique was used to analyze the metamagnetic transition from paramagnetic (PM) to ferromagnetic (FM) phases and to study its evolution towards the quantum critical end point. The existence of exotic magnetic excitations in the ground state and around the critical end point were also evidenced.On the compound CeRh$_2$Si$_2$, the suppression of the antiferromagnetic (AF) order by magnetic fields and pressures was explored. A strong change of the Fermi surface at $H_c$, the field at which the suppression of the AF into the paramagnetic polarized (PPM) phase, was observed. We show that under pressure, the magnetic fluctuations around the critical pressure $P_c$ masked the Fermi surface reconstruction of the AF phase into the PM phase. The analysis of the $(T,P,H)$ phase diagram revealed that the non-ordered phases of this compound (PM and PPM) are different, therefore pressure and field behave as different suppressor mechanisms.In the UGe$_2$ compound, the analysis of its Fermi surface by thermopower quantum oscillations was performed as a last example of the utility and of the importance of this technique. To the best of the author knowledge, this is the first time that this technique was used in heavy fermion systems. A comparison to traditional probes such as de Haas-van Alphen and Shubnikov–de Haas effects was done. We observed a good agreement between them and we explain the advantages and the disadvantages of thermopower quantum oscillations technique over the traditional probes
Zhang, Hongbin. "Relativistic Density Functional Treatment of Magnetic Anisotropy". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25132.
Texto completoSpin-Bahn-Kopplung reduziert die Symmetrie ferromagnetischer Festkörper. Das bedeutet, dass die physikalischen Eigenschaften ferromagnetischer Stoffe anisotrop bezüglich der Magnetisierungsrichtung sind. In dieser Dissertation werden mittels numerischer voll-relativistischer Dichtefunktional-Rechnungen zwei Arten physikalischer Eigenschaften untersucht: magnetische Oberflächen-Anisotropieenergie (MAE) und anisotrope Thermokraft durch Lifshitz-Übergänge. Nach einer kurzen Einführung in die relativistische Dichtefunktional-Theorie in Kapitel 2 wird in Kapitel 3 die MAE ferromagnetischer dünner Filme untersucht. In diesen Systemen ist es für ein Verständnis experimenteller Ergebnisse wichtig, verschiedene Beiträge zu separieren: Volumenanteil der magnetokristallinen Anisotropie (MCA), Formanistropie und Oberflächen bzw. Grenzflächenanisotropie. Durch Anpassen berechneter Daten für dicke Schichten an ein phänomenologisches Modell konnten verlässliche Oberflächen Anisotropien erhalten werden. In dieser Weise wurde die MAE von Co- Schichten mit unterschiedlichen Geometrien untersucht, wobei der Einfluss von Orbitalpolarisations-Korrekturen (OPC) im Vordergrund stand. Es wurde gefunden, dass die Oberflächenanisotropie hauptsächlich von der Geometrie bestimmt wird. Während OPC bessere Ergebnisse für die Orbitalmomente liefert, wird die MAE überschätzt. Im zweiten Teil von Kapitel 3 wird der Einfluss elektrischer Felder auf die MAE von dünnen ferromagnetischen Filmen mit L10-Struktur untersucht. Unter Verwendung eines einfachen Modells zur Simulation des elektrischen Feldes liefern die Rechnungen gute Übereinstimmung mit vorliegenden experimentellen Ergebnissen. Es wird vorhergesagt, dass für CoPt ein noch größerer Effekt existiert. Weiterhin wurde gefunden, dass die magnetoelektrische Kopplung von der Größe der Abschirmladung bestimmt wird. Dies ist eine wichtige Einsicht, um die Magnetisierungsrichtung durch ein elektrisches Feld kontrollieren zu können. In Kapitel 4 werden Lifshitz-Übergänge untersucht, die ein gekantetes Magnetfeld hervorruft. Es wurden mehrere Lifshitz-Übergänge in geordnetem FePt gefunden, welche kleine Anomalien in der Zustandsdichte hervorrufen. Mit Hilfe eines Zweiband-Modells wird gezeigt, dass an solchen Übergängen das singuläre Verhalten kinetischer Eigenschaften durch Interband- Streuung verursacht wird und dass die Singularität proportional zur Ableitung der singulären Zustandsdichte ist. In FePt wird durch chemische Unordnung diese Singularität zu einer Anomalie verschmiert. Der Einfluss einer Verbreiterung der Energieniveaus der kritischen Bänder in FePt wurde mittels CPA untersucht. Es wurde gefunden, dass in experimentell verfügbaren dünnen FePt-Filmen Lifshitz-Übergänge bis zu 3% Erhöhung der Thermokraft erzeugen, wenn die Magnetisierung von der leichten in die harte Richtung gedreht wird
Momtaz, Zahra Sadre. "Transporte em nanoestruturas: fenômenos quânticos em poços duplos e triplos". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-04012017-143327/.
Texto completoIn this thesis, we present the studies of magneto-transport in narrow , wide and triple quantum wells in low magnetic fields. Depending on the desired studies, we have measured the magneto-resistance both in linear and nonlinear regimes and under the application of AC current, microwave irradiation and temperature gradient along the samples. We have reported the observation of nonlinear effects of AC current on magneto-inter-sub-band oscillations (MIS) of triple quantum wells (TQWs). The MIS oscillations in single and double quantum well system and also nonlinear effects due to DC current have been studied before in these systems. Our results are explained according to a generalized model based on non-equilibrium part of electron distribution function. The nonlocal magneto-resistance under microwave irradiation is also studied within this thesis. The obtained results provide evidence for an edge-state current stabilized by microwave irradiation due to nonlinear resonances and have been described by a model based on the nonlinear dynamics and Chirikov standard map. Finally, we have observed the phonon-drag voltage oscillations correlating with the resistance oscillations under microwave irradiation in a two-dimensional electron gas in perpendicular magnetic field. The influence of dissipative resistivity modified by microwave on phonon-drag voltage perpendicular to the phonon flux can explain our observations. Moreover, sharp features observed in phonon drag voltage suggest the current domains associated with these states can exist in the absence of external DC driving.
Romanovsky, Igor Alexandrovich. "Novel properties of interacting particles in small low-dimensional systems". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07102006-041659/.
Texto completoLandman, Uzi, Committee Member ; Yannouleas, Constantine, Committee Member ; Bunimovich, Leonid, Committee Member ; Chou, Mei-Yin, Committee Member ; Pustilnik, Michael, Committee Member.
Pawula, Florent. "Particularités des oxydes de ruthénium sondées par l'effet Seebeck". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC225/document.
Texto completoThis thesis deals with the synthesis, the structural study and the magnetic properties and electronic transport studies of different ruthenium oxide families, presenting various magnetic and electronic behaviors, with rutile, R-type hexaferrite and hollandite structures. The goal of this thesis was the study of the ruthenium oxide peculiarities probed by the Seebeck effect in the following materials: RuO2 rutile (edge-shared RuO6 chain interconnected by their vertices) with Boltzmann type transport dominated by electron-phonon interactions, BaCo2Ru4O11 et BaMn2Ru4O11 R-type hexaferrites (edge-shared RuO6 octahedra, forming kagome planes, and face-shared RuO6 octahedra) soft ferromagnetic bad metals, and two new hollandites Sr1.5Ru6.1Cr1.9O16 et Ba1.5Ru6.1Cr1.9O16 (double chains of edge-shared RuO6 octahedra, interconnected by their vertices) with localized transport and cluster-glass behavior. The synthesis of both new hollandites by solid state reaction allowed us to show the existence of negative magnetoresistance in this compound family. This thesis shows that the behavior of the Seebeck coefficient of ruthenium oxides with structures mainly consisting of edge-shared RuO6 octahedra presents two different behaviors. At low T, S strongly depends on the crystallographic structure and on the associated electronic structure. On the other hand, in the high T limit, S tends a common value independently of the structure as reported here for the R-type hexaferrites and the hollandites and as previously observed in the ferromagnetic metal SrRuO3 perovskite (apex-shared RuO6 octahedra) and in the metallic with Pauli-type magnetism quadruple perovskite LaCu3Ru4O12 (apex-shared RuO6 octahedra). In these R-type hexaferrites BaCo2Ru4O11 and BaMn2Ru4O11 and these two new hollandites Sr1.5Ru6.1Cr1.9O16 and Ba1.5Ru6.1Cr1.9O16, the high temperature Seebeck coefficient reaches a value dominated by the Ru spin entropy term
Lipp, Dieter. "Thermische Tieftemperatureigenschaften von Seltenerd-Übergangsmetall-Borkarbiden". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1021367425218-47062.
Texto completoIn der vorliegenden Arbeit werden Untersuchungen zu thermischen Tieftemperatureigenschaften, wie der spezifischen Wärmekapazität, der Wärmeleitfähigkeit und der Thermokraft, an supraleitenden Seltenerd-Übergangsmetall-Borkarbiden vorgestellt. Es wurde der Einfluß von gezielt hervorgerufener Unordnung im kristallographischen Aufbau, die durch isoelektronische Substitutionen des Seltenerd-Elements und des Übergangsmetalls sowie durch Söchiometrievariationen erzeugt wurde, auf die thermischen und supraleitenden Tieftemperatureigenschaften untersucht. Folge der strukturellen Unordnung ist eine Reduzierung der charakteristischen Eigenschaften, wie der Sprungtemperatur der Supraleitung Tc, der Sommerfeldkonstanten gamma, des oberen kritischen Magnetfelds Hc2(0), der negativen Krümmung in der Feldabhängigkeit des T-linearen Beitrags zur spezifischen Wärme gamma(H) sowie eine Reduzierung der positiven Krümmung in der Temperaturabhängigkeit von Hc2(T). Isoelektronische Substitutionen auf dem Seltenerd-Platz führen aber nicht zum Erreichen des dirty limit. Eine Reduzierung der relevanten supraleitenden und thermischen Eigenschaften durch Pt-Beimengungen wird ähnlich wie im Falle der Lu-Substitution festgestellt. Die Konzentrationsabhängigkeit von Hc2(0) sowie die Krümmung von Hc2(T) weisen hier auf einen Übergang vom clean limit zum quasi-dirty limit durch die Pt-Substitution hin
Isotta, Eleonora. "Nanostructured thermoelectric kesterite Cu2ZnSnS4". Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/315174.
Texto completoIsotta, Eleonora. "Nanostructured thermoelectric kesterite Cu2ZnSnS4". Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/315174.
Texto completoLipp, Dieter. "Thermische Tieftemperatureigenschaften von Seltenerd-Übergangsmetall-Borkarbiden". Doctoral thesis, Technische Universität Dresden, 2001. https://tud.qucosa.de/id/qucosa%3A24137.
Texto completoIn der vorliegenden Arbeit werden Untersuchungen zu thermischen Tieftemperatureigenschaften, wie der spezifischen Wärmekapazität, der Wärmeleitfähigkeit und der Thermokraft, an supraleitenden Seltenerd-Übergangsmetall-Borkarbiden vorgestellt. Es wurde der Einfluß von gezielt hervorgerufener Unordnung im kristallographischen Aufbau, die durch isoelektronische Substitutionen des Seltenerd-Elements und des Übergangsmetalls sowie durch Söchiometrievariationen erzeugt wurde, auf die thermischen und supraleitenden Tieftemperatureigenschaften untersucht. Folge der strukturellen Unordnung ist eine Reduzierung der charakteristischen Eigenschaften, wie der Sprungtemperatur der Supraleitung Tc, der Sommerfeldkonstanten gamma, des oberen kritischen Magnetfelds Hc2(0), der negativen Krümmung in der Feldabhängigkeit des T-linearen Beitrags zur spezifischen Wärme gamma(H) sowie eine Reduzierung der positiven Krümmung in der Temperaturabhängigkeit von Hc2(T). Isoelektronische Substitutionen auf dem Seltenerd-Platz führen aber nicht zum Erreichen des dirty limit. Eine Reduzierung der relevanten supraleitenden und thermischen Eigenschaften durch Pt-Beimengungen wird ähnlich wie im Falle der Lu-Substitution festgestellt. Die Konzentrationsabhängigkeit von Hc2(0) sowie die Krümmung von Hc2(T) weisen hier auf einen Übergang vom clean limit zum quasi-dirty limit durch die Pt-Substitution hin.
Chickering, William Elbridge. "Thermopower in Two-Dimensional Electron Systems". Thesis, 2016. https://thesis.library.caltech.edu/9320/2/thesis.pdf.
Texto completoThe subject of this thesis is the measurement and interpretation of thermopower in high-mobility two-dimensional electron systems (2DESs). These 2DESs are realized within state-of-the-art GaAs/AlGaAs heterostructures that are cooled to temperatures as low as T = 20 mK. Much of this work takes place within strong magnetic fields where the single-particle density of states quantizes into discrete Landau levels (LLs), a regime best known for the quantum Hall effect (QHE). In addition, we review a novel hot-electron technique for measuring thermopower of 2DESs that dramatically reduces the influence of phonon drag.
Early chapters concentrate on experimental materials and methods. A brief overview of GaAs/AlGaAs heterostructures and device fabrication is followed by details of our cryogenic setup. Next, we provide a primer on thermopower that focuses on 2DESs at low temperatures. We then review our experimental devices, temperature calibration methods, as well as measurement circuits and protocols.
Latter chapters focus on the physics and thermopower results in the QHE regime. After reviewing the basic phenomena associated with the QHE, we discuss thermopower in this regime. Emphasis is given to the relationship between diffusion thermopower and entropy. Experimental results demonstrate this relationship persists well into the fractional quantum Hall (FQH) regime.
Several experimental results are reviewed. Unprecedented observations of the diffusion thermopower of a high-mobility 2DES at temperatures as high as T = 2 K are achieved using our hot-electron technique. The composite fermion (CF) effective mass is extracted from measurements of thermopower at LL filling factor ν = 3/2. The thermopower versus magnetic field in the FQH regime is shown to be qualitatively consistent with a simple entropic model of CFs. The thermopower at ν = 5/2 is shown to be quantitatively consistent with the presence of non-Abelian anyons. An abrupt collapse of thermopower is observed at the onset of the reentrant integer quantum Hall effect (RIQHE). And the thermopower at temperatures just above the RIQHE transition suggests the existence of an unconventional conducting phase.
Lou, Hou-Lun y 羅晧倫. "Dynamic Thermopower of Ni-DNA System". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/259qhg.
Texto completoLee, Jui-Kan y 李瑞康. "Transport and Thermopower Studies of Indium Tin Oxide Films". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/41260849119722087583.
Texto completo輔仁大學
物理學系
98
We have measured the resistance, thermopower and magnetoresistance of a series of annealed indium tin oxide (ITO) thin films (thickness 21nm) and compared with Bloch-Grüneisen law, Seebeck effect and two-dimensional weak-localization effect, respectively. We extracted Debye temperature , electron-phonon coupling constant , Fermi energy , carrier concentration , phase breaking time . This observation provided a direct experimental proof of the free-electron-like characteristic of the energy band structure of ITO. Besides, our results also revealed the electron-phonon interaction was very weak in ITO films. Our extracted values of ~1050 K and cm-3 are very close to previous studies, and are larger one order of magnitude than metals.
Wang, Yu-Hao y 王宇豪. "Thermopower,specific heat and magnetic properties in FeSi2 nanoparticles". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/02994040106672007475.
Texto completo輔仁大學
物理學系
91
The high-temperature α-phase of FeSi2 is metallic while low-temperature β-phase is a semiconductor . In this thesis we present the study of thermopower S, thermal conductivityκand electrical conductivityσ of α and β-phases of FeSi2 . Furthermore, the values of Figure of Merit Z = S2σ/κwere calculated and the results shows β- FeSi2 had higher thermpower as well as higher efficiency Z compared with theα- FeSi2. The nanoparticles of β- FeSi2 were fabricated by different methods such as flash evaporation, EDM and ball milling. We discuss how the size effects on S,κandσ inβ- FeSi2. The result show that the values of S, κ and σ in β- FeSi2 nanoparticles were smaller than the bulk. The specific heat of β- FeSi2 nanoparticles was higher than the bulk at 0.3 to 30 K . The magnetic susceptibility of β- FeSi2 nanoparticles and bulks were measured from 2 to 300 K, and the results reveals thatβ- FeSi2 nanoparticles have superparamagnetism and Blocking Temperature at 70 K.
Duarte, Nicolas Benjamin Tadigadapa Srinivas A. "Thermopower measurement of gold nanowire systems using a micromachined workbench". 2008. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-3314/index.html.
Texto completoChih-Ting, Chen y 陳志挺. "Thermopower , thermal conductivity and specific heat in Bi2Te3 bulk and nanoparticles". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/38081379361892512692.
Texto completo淡江大學
物理學系
91
This experiment is aim to improve on TE material quality as Seebeck coefficient and thermal conductivity by analyzing, and hopefully increasing, the TE figure of merit, Z, which is an important factor related to efficient energy conversion. Fortunately, theory and literature have revealed that by decreasing the dimensions of our samples, we can increase Seebeck coefficient, and therefore, improve on the Z.So,we reduce our specimen Bi2Te3 size by milling and EDM methods and try to study the relationship between sample size and it’s thermopower, thermal conductivity and specific heat.
Su, C. H. y 蘇家弘. "Set-Up of Simultaneous Real-Time Measurements of High-Temperature Resistivity and Thermopower". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/41013154974946927011.
Texto completo國立彰化師範大學
光電工程技術研究所
92
Abract This thesis describes the set up of simultaneous real-time measurements of high-temperature resistivity and thermopower. This system is used to study the thermoelectric properties of hot-pressed Bi2Te3 and Na0.65Co1-xNixO2. We use current sourcemeter Keithley 2400, digit multimeter Keithley 2000 and high-temperature vacuum furnace, which were interface by the IEEE488 to measure the high-temperature resistivity and thermopower simultaneously. Data acquisition is automatically controlled by a user-writer program usingVB6.0 language. Bi2Te3 was prepared via metal-organo complex method and hot pressing process at various combination of temperature and pressure. The resistivity and thermopower of Bi2Te3 were measured from 77K to 573K. From XRD patterns, on the preferential orientation (0,0,15) reflection plane is observed for all the hot-pressed Bi2Te3 samples. These results show that the electrical resistivity decreases and thermopower exhibits a optimum values with increasing temperature. Based on the combination of resistivity and thermopower data, we can conclude that the mobility increases with increasing temperature. The carrier concentration shows minimum value probably due to the lattice deformation and the composition deviation of tellurium from stoichiometric Bi2Te3. The power factor of the hot-pressed sample prepared at the pressure of 220 MPa and at 350℃ is 8.8μW/cmK2. Polycrystalline samples of Na0.65Co1-xNixO2 were prepared by rapid heat-up method and high-temperature resistivity and thermopower were measured up to 573K. We find that the phase stability of Na0.65Co1-xNixO2 is poor in vacuum and the measurement is not reliable because of phase formation of Co3O4. With temperature increasing, the resistivity of Na0.65Co1-xNixO2 decreases and the thermopower increases. Therefore, Na0.65Co1-xNixO2 has better thermoelectric properties at high temperature as compared to low temperatures and shows promising application at high temperatures.
Jayaraman, Aditya. "Tuning the electrical and thermoelectric properties of bilayer graphene by band engineering". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/5188.
Texto completoTseng, Kai-Sheng y 曾凱笙. "Negative Capacitance Effect and Thermopower in C6H2X2(NH2)2-Single Molecule Junctions (X=H, F, Cl, Br)". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/d5v33h.
Texto completo國立交通大學
電子物理系所
106
We study the effect of functional substitution in negative capacitance and thermopower in single-molecule junctions from first-principles, The single-molecule junction is formed by a C6H2X2(NH2)2 molecule (x=H,F,Cl,Br) sandwiched between two Au electrodes connected to a battery. The electric dipole moment is induces by the asymmetric molecule due to functional substitution, and thus forming a ferroelectric single-molecule junction. When a voltage is applied, negative capacitance may occur owing to the inversion of the electric dipole moment. Firstly we relax the structure of C6H2X2(NH2)2 by total energy calculation using VASP. It’s charge density of C6H2X2(NH2)2 is applied as the initial guess density for current-carrying wave functions obtained self-consistently in the framework of density-functional theory combined to Lippmann-Schwinger equation under various voltages. The non-equilibrium wave functions are applied to calculate the charge distribution, electric multipole moments current and Seebeck coefficient, we also investigate the correlation between electric multipole moments and the current and Seebeck coefficient.
Mitra, Richa. "Coulomb drag to thermopower response in dimensionally mismatched InAs nanowire-Graphene heterostructures and anisotropic noise in ReS2". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4770.
Texto completoRyu, Yeontack. "Energy Carrier Transport In Surface-Modified Carbon Nanotubes". Thesis, 2012. http://hdl.handle.net/1969.1/148118.
Texto completo"Synthesis, Structures and Properties of Thermoelectric Materials in the Zn-Sb-In System". Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.9179.
Texto completoDissertation/Thesis
Ph.D. Chemistry 2011
Pandey, Tribhuwan. "Addressing the Challenges in Designing of Efficient Thermoelectric Materials". Thesis, 2015. https://etd.iisc.ac.in/handle/2005/4806.
Texto completoHamad, Nagat El-Sabaey Farag. "Magnetische und Elektrische Eigenschaften von Nd0.66(Sr1-yLiy)0.34MnO3 Manganiten". Doctoral thesis, 2003. http://hdl.handle.net/11858/00-1735-0000-0006-B0B6-E.
Texto completoWalter, Marvin. "The tunnel magneto-Seebeck effect in magnetic tunnel junctions". Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0022-5E09-E.
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