Spelling suggestions: "subject:"erudite."" "subject:"erudita.""
1 |
Thermal and charge conductivities of superconducting skutterudite compounds, PrRu4Sb12 and PrOs4Sb12Rahimi, Somayyeh Jay January 2007 (has links)
The measurement of thermal conductivity is a powerful probe that can be used for identifying the nature of heat and charge carriers and structure of the gap in the superconducting compounds. At low temperature when the effect of phonons in transporting heat becomes smaller, one can obtain information about the quasiparticle distribution and the superconducting gap structure.
In order to do a sensitive thermal conductivity measurement, we designed and built a thermal conductivity mount. The charge conductivity was measured through the same leads that we used for making the thermal conductivity measurements. To test the mount, we measured the heat and charge conductivity of a silver wire and determined the accuracy with which we could satisfy the Wiedemann--Franz law within 5 \%.
We will report the measurements of thermal and electrical conductivities of two filled skutterudite superconducting compounds, PrRu4Sb12 and PrOs4Sb12 at 1.1--35 K temperature range. The differences and similarities between the transport properties of these compounds in the superconducting and normal states along with the results of investigation of the Wiedemann--Franz law will be discussed in the following chapters.
|
2 |
Thermal and charge conductivities of superconducting skutterudite compounds, PrRu4Sb12 and PrOs4Sb12Rahimi, Somayyeh Jay January 2007 (has links)
The measurement of thermal conductivity is a powerful probe that can be used for identifying the nature of heat and charge carriers and structure of the gap in the superconducting compounds. At low temperature when the effect of phonons in transporting heat becomes smaller, one can obtain information about the quasiparticle distribution and the superconducting gap structure.
In order to do a sensitive thermal conductivity measurement, we designed and built a thermal conductivity mount. The charge conductivity was measured through the same leads that we used for making the thermal conductivity measurements. To test the mount, we measured the heat and charge conductivity of a silver wire and determined the accuracy with which we could satisfy the Wiedemann--Franz law within 5 \%.
We will report the measurements of thermal and electrical conductivities of two filled skutterudite superconducting compounds, PrRu4Sb12 and PrOs4Sb12 at 1.1--35 K temperature range. The differences and similarities between the transport properties of these compounds in the superconducting and normal states along with the results of investigation of the Wiedemann--Franz law will be discussed in the following chapters.
|
3 |
Synthesis of skutterudites as thermoelectric materials /Sellinschegg, Heike, January 2000 (has links)
Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 91-93). Also available for download via the World Wide Web; free to University of Oregon users.
|
4 |
Transport properties of 40% La filled skutterudite thin films theory and instrumentation /Attanayake, Harsha. January 2008 (has links)
Thesis (M.S.)--Bowling Green State University, 2008. / Document formatted into pages; contains viii, 32 p. : ill. Includes bibliographical references.
|
5 |
Fundamental investigations of skutterudite phase formation by the modulated elemental reactant method /Williams, Joshua R., January 2002 (has links)
Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 124-128). Also available for download via the World Wide Web; free to University of Oregon users.
|
6 |
Transport dans les composés thermoélectriques skutterudites de type R(x)Co(4-y)Ni(y)Sb(12) (R=Nd, Yb et In) / Transport in thermoelectric skutterudite compounds RxCo4-yNiySb12 (R=Nd, Yb AND In)Da Ros, Véronique 30 May 2008 (has links)
Dans le cadre du regain d’activité pour la thermoélectricité, les matériaux skutterudite suscitent un vif intérêt du fait de leurs performances dans la gamme de température 400-800 K. L’étude des propriétés structurales et thermoélectriques de triantimoniures de cobalt partiellement remplies au néodyme, à l’ytterbium ou à l’indium, et partiellement substituées au nickel a ainsi été menée. Des composés denses et homogènes ont été obtenus via une technique de métallurgie des poudres. L’analyse conjointe des résultats de diffraction des rayons X et de microsonde de Castaing a permis de déterminer les limites de solubilité x des éléments remplisseurs dans Co4Sb12 : ainsi, xNd ~ 0,05 – 0,06, et xYb ~ xIn ~ 0,18. Dans le cas de l’ytterbium, nous avons montré par diffraction de neutrons sur poudre que ces atomes sont localisés au centre des cavités de la structure et qu’ils présentent un paramètre de déplacement atomique élevé. Les propriétés électriques (résistivité électrique, pouvoir thermoélectrique, effet Hall) et thermiques (conductivité thermique) ont été scrutées sur une vaste gamme de température (2 à 800 K). L’analyse des mesures, entre 2 et 800 K, a montré que plus la teneur en élément inséré est élevée, plus celui-ci a un impact bénéfique sur les propriétés thermoélectriques. Les performances maximales atteintes s’élèvent ainsi à ZT ~ 0,3 pour le composé Nd0,052Co4Sb12 à 800 K, ZT ~ 0,9 pour le composé In0,180Co4Sb12 à 710 K et ZT ~ 1 pour le composé Yb0,180Co4Sb12 à 800 K. L’optimisation de ces matériaux a alors été considérée via la substitution partielle du cobalt par du nickel. Nous avons montré que la présence de nickel augmente la concentration de porteurs de charge et modifie les mécanismes de diffusion onde ceux-ci. Dans le cas des composés partiellement remplis au néodyme, son impact sur les propriétés thermoélectriques est très bénéfique. Pour les composés à l’indium et à l’ytterbium, des compensations de l’influence du nickel sur les différents paramètres s’opèrent si bien que les performances thermoélectroniques globales du matériau ne présentent pas d’amélioration significative / In a context of renewed interest in thermoelectric compounds, skutterudite materials are an interesting target because of their good performances in the temperature range 400-800 K. The study of structural and thermoelectric properties of cobalt triantimonides partially filled with neodymium, ytterbium and indium, and partially substituted with nickel, has been undertaken. Dense and homogeneous samples have been obtained using a powder metallurgy technique. The joint analysis of X-ray diffraction and electroprobe microanalysis led to the determination of the solubility limit of the filler elements: xNd ~ 0,05 – 0,06, and xYb ~ xIn ~ 0,18. For ytterbium, we were able to prove by powder neutron diffraction technique that the atoms are localized at the centre of the structure and that they have a very high atomic displacement parameter. Electrical properties (electrical resistivity, thermal conductivity, Hall effect) and thermal properties (thermal conductivity) have been investigated on a very large range of temperature (2 to 800K). The exploitation of the measurements showed that the higher the quantity of each insertion element, the greater its beneficial impact on the thermoelectric properties. The best performances have been reached with ZT ~ 0,3 for Nd0,052Co4Sb12 at 800 K, ZT ~ 0,9 in the case of In0,180Co4Sb12 at 710 K and ZT ~ 1 for Yb0,180Co4Sb12 at 800 K. An optimisation was considered using the partial substitution of cobalt by nickel. The impact of nickel on the thermoelectric performances on ternary compounds was very different depending on the element. In the case of neodymium, the presence of nickel modified the diffusion mechanism of the carriers and its impact was very beneficial. For indium and ytterbium, the impact of nickel did not lead to any significant improvement
|
7 |
CoGe&esc;b1&esc;s&&dotb;esc;b5&esc;sSe&esc;b1&esc;s&&dotb;esc;b5&esc;s [electronic resource] : structural and transport properties characterization / by Randolph Ertenberg.Ertenberg, Randolph. January 2003 (has links)
Title from PDF of title page. / Document formatted into pages; contains 43 pages. / Thesis (M.S.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: Skutterudites have been of great interest for thermoelectric applications over the last ten years. Scientific interest has focused on the unique transport properties Skutterudites possess due to the unique crystal structure. Technical interest has grown since it was discovered that some compounds rival the current best thermoelectric materials. To further the understanding of this material system, and optimize its thermoelectric properties, the synthesis and characterization of polycrystalline n- and p-type CoGe&esc;b1&esc;s&&dotb;esc;b5&esc;sSe&esc;b1&esc;s&&dotb;esc;b5&esc;s was undertaken. Structural, morphological, chemical, electrical, thermal and magnetic properties were studied. These data are compared to those of the binary Skutterudite CoSb3. The results of this study show a very sensitive dependence of the physical properties on stoichiometry. / ABSTRACT: While the thermoelectric figure of merit is low in these materials, it is apparent that optimization via doping and "void filling" will lead to improved thermoelectric properties. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.
|
8 |
An assessment of the long-range electric quadrupole interactions in praseodymium-filled skutterudites /Sapkota, Ram P., January 2005 (has links)
Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 51-55.
|
9 |
Synthesis, crystal chemistry, and properties of skutterudites /Smalley, Arwyn Lisa Emrys, January 2005 (has links)
Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 110-113). Also available for download via the World Wide Web; free to University of Oregon users.
|
10 |
Etude de la stabilité thermique d'un matériau skutterudite et développement de barrières de diffusion pour applications thermoélectriques / Study of the thermal stability of a skutterudite material and development of diffusion barriers for thermoelectric applicationsBoulat, Laetitia 06 November 2014 (has links)
Dans le contexte énergétique actuel, la thermoélectricité, basée sur la conversion directe de l'énergie thermique en énergie électrique, est en plein essor. Cette technologie, qui permet de récupérer l'énergie perdue sous forme de chaleur au cours de processus industriels, est basée sur l'utilisation de modules thermoélectriques. Ces modules sont constitués de la juxtaposition de branches thermoélectriques, constituées de semi-conducteurs n et p, reliées par des jonctions électriques. Dans la gamme de températures de 300 à 600°C, les matériaux de type skutterudite RM4X12 (R : terre rare, M : métal de transition, X : pnictogène) présentent des propriétés thermoélectriques intéressantes. Cependant, les propriétés aux interfaces entre les jonctions électriques et le matériau thermoélectrique jouent un rôle très important dans la performance des modules thermoélectriques. Il est nécessaire de minimiser les pertes électriques et thermiques au niveau de ces interfaces. De même, en zone chaude principalement, il est impératif de limiter l'inter-diffusion entre les éléments constituant le matériau thermoélectrique et le matériau utilisé pour les connexions électriques. La formation de composés aux interfaces peut, en effet, être à l'origine de la dégradation des propriétés du matériau thermoélectrique. Ces contraintes conduisent à introduire des barrières de diffusion entre le matériau thermoélectrique et les connexions électriques. C'est dans ce contexte que ce situe la présente étude, l'objectif étant d'étudier la potentialité de matériaux à base de nitrure de tantale en tant que barrières de diffusion. Ainsi, des couches minces à base de nitrure de tantale ont été déposées, par le procédé de pulvérisation cathodique, sur les substrats de type skutterudite, CeFe4Sb12, les connexions électriques étant en cuivre. L'efficacité de barrières monocouches, TaN, et tri-couches, TaN/Ta/TaN, a été étudiée, ces couches présentant une épaisseur totale de 1 ou 1,5 µm. La première étape de ce travail a consisté en l'étude de la stabilité thermique du matériau skutterudite afin de déterminer le domaine d'utilisation en température de ce matériau. Dans une seconde étape, la potentialité de monocouches, TaN, et multicouches, TaN/Ta/TaN, en tant que barrières de diffusion a été déterminée à partir d'une étude microstructurale. Les assemblages CeFe4Sb12/barrière/Cu ont été préalablement soumis à des traitements thermiques sous vide à des températures variant de 400 à 600°C. Enfin dans une dernière étape, l'étude théorique des mécanismes de migration a été menée à partir des calculs d'énergies d'incorporation et de migration des atomes étrangers, tels que le cuivre et l'antimoine, dans le nitrure de tantale massif. / Due to the current energy context, thermoelectricity based on the direct conversion of thermal energy into electrical energy is of great interest. Direct conversion of thermal energy to electrical energy requires the use of thermoelectric devices made of n- and p-type semiconductor couples connected by electrical junctions. RM4X12 (R: rare earth, M: transition metal, X: pnictogen) skutterudite compounds have been reported to be promising for thermoelectric applications in the [400-600]°C intermediate temperature range. However the performance of thermoelectric devices is strongly dependent on the joining of thermoelectric couples with metal electrodes as the conversion efficiency is greatly influenced by the contact resistance. High electrical and thermal conductivities are required associated with a high interfacial mechanical strength. Moreover the joining material has to be selected to avoid any interfacial reaction occurring during the device fabrication and use. Diffusion barriers are also needed to limit these interfacial reactions which may be detrimental to the thermoelectric device performance. The aim of this work is to study the efficiency of tantalum nitride based materials as diffusion barriers. TaN single layer and TaN/Ta/TaN multilayers barriers were deposited by sputtering between the CeFe4Sb12 skutterudite substrate and the Cu electrical junction. The inter-diffusion of elements was studied through these mono- and multi-layers, of 1 μm or 1.5 μm in thickness. In a first step, the thermal stability of the skutterudite has been investigated to determine the use temperature range of this material. In a second step the efficiency of TaN and TaN/Ta/TaN layers as diffusion barriers has been determined from a microstructural study. CeFe4Sb12/barrier/Cu stackings were previously annealed under vacuum in the [400-600]°C temperature range. Finally a theoretical study of the migration mechanisms was carried out from the calculations of the incorporation and migration energies of species, more specifically Sb and Cu, in the bulk tantalum nitride.
|
Page generated in 0.0439 seconds