• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 6
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 10
  • 10
  • 4
  • 4
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Thermoelectric Materials: Ternary and Higher Oxides and Tellurides

Cui, Yanjie January 2009 (has links)
Thermoelectric power generators can convert a temperature gradient into electrical energy, serving as a new energy resource by utilizing solar energy or by utilizing more waste heat. Thermoelectric coolers have the advantage of no moving parts, are quiet and release no gases that are harmful to the atmosphere, in contrast to compression-based refrigeration. While the low efficiency of “classical” thermoelectric devices limits their wide applications, the exploration of better thermoelectric materials is of great importance to improve the efficiency of thermoelectric devices. Good thermoelectric materials are usually narrow band gap semiconductors with a large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. This thesis deals with the exploration of new thermoelectric materials based on transition metal tellurides and the optimization of bulk materials based on oxides of low toxicity and high stability in air. In the first project, seven new ternary or quaternary tellurides, crystallizing in three different structure types, were synthesized and characterized. Single crystal X-ray diffraction was used for crystal structure determination; powder X-ray diffraction and energy dispersive X-ray analysis (EDAX) were used for phase and composition analyses. Physical properties of these compounds were predicted by electronic structure calculations and confirmed by physical property measurements. In the second project, two series of n-type doped perovskite SrTiO3 were prepared in a high temperature tube furnace under dynamic high vacuum of the order of 10–6 mbar, namely SrTi1-x(Nb,Ta)xO3, and Sr1-xLaxTi1-x(Nb,Ta)xO3. The phase purity was characterized by means of powder X-ray diffraction and electron probe micro analysis (EPMA). Rietveld refinements were performed to check for purity and symmetry reduction. The physical properties, such as Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured at high temperatures for all the samples. Of the series of Nb/Ta-doped strontium titanates SrTi1-x(Nb,Ta)xO3, SrTi0.90Ta0.10O3 exhibits the highest ZT value, namely 0.17 for at 752 K. Of the double substituted series, Sr0.99La0.01Ti0.99Ta0.01O3 was best with ZT = 0.13 at 660 K. The rapid increases imply that higher ZT values are likely to occur at higher temperatures.
2

Thermoelectric Materials: Ternary and Higher Oxides and Tellurides

Cui, Yanjie January 2009 (has links)
Thermoelectric power generators can convert a temperature gradient into electrical energy, serving as a new energy resource by utilizing solar energy or by utilizing more waste heat. Thermoelectric coolers have the advantage of no moving parts, are quiet and release no gases that are harmful to the atmosphere, in contrast to compression-based refrigeration. While the low efficiency of “classical” thermoelectric devices limits their wide applications, the exploration of better thermoelectric materials is of great importance to improve the efficiency of thermoelectric devices. Good thermoelectric materials are usually narrow band gap semiconductors with a large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. This thesis deals with the exploration of new thermoelectric materials based on transition metal tellurides and the optimization of bulk materials based on oxides of low toxicity and high stability in air. In the first project, seven new ternary or quaternary tellurides, crystallizing in three different structure types, were synthesized and characterized. Single crystal X-ray diffraction was used for crystal structure determination; powder X-ray diffraction and energy dispersive X-ray analysis (EDAX) were used for phase and composition analyses. Physical properties of these compounds were predicted by electronic structure calculations and confirmed by physical property measurements. In the second project, two series of n-type doped perovskite SrTiO3 were prepared in a high temperature tube furnace under dynamic high vacuum of the order of 10–6 mbar, namely SrTi1-x(Nb,Ta)xO3, and Sr1-xLaxTi1-x(Nb,Ta)xO3. The phase purity was characterized by means of powder X-ray diffraction and electron probe micro analysis (EPMA). Rietveld refinements were performed to check for purity and symmetry reduction. The physical properties, such as Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured at high temperatures for all the samples. Of the series of Nb/Ta-doped strontium titanates SrTi1-x(Nb,Ta)xO3, SrTi0.90Ta0.10O3 exhibits the highest ZT value, namely 0.17 for at 752 K. Of the double substituted series, Sr0.99La0.01Ti0.99Ta0.01O3 was best with ZT = 0.13 at 660 K. The rapid increases imply that higher ZT values are likely to occur at higher temperatures.
3

Optimization of Type-I Clathrates for Thermoelectric Properties

Jeung, Suk-kyung January 2012 (has links)
The increase in waste heat after consuming energy or burning fossil fuels is an issue environmentally and economically. Thermoelectric (TE) materials are developed to use in various applications because of their ability in converting waste heat into electricity. However, the applications are limited due to a low efficiency of materials, and research on thermoelectric materials is an on-going project for future use. Type-I clathrates are one of the TE materials which are studied in depth since the proposal of Slack’s PGEC (Phonon-Glass-Electron-Crystal) concept in 1995 due to their excellent thermoelectric properties. In this study, development and optimization of quaternary type-I clathrates will be the focus because double substitution often leads to better figure-of-merit, ZT, but it hasn’t really been studied. Higher ZT value is necessary because the energy conversion efficiency of TE materials is depending on the ZT value along with a larger temperature difference. Addition of lanthanoid elements as 2nd guest atoms to the main type-I clathrate structure, realized in Ba8Ga16Ge30, will be attempted to form quaternary compounds. The formation of the quaternary clathrates will be analyzed through powder X-ray diffraction, single crystal analysis and energy dispersive X-ray analysis. Also, as the performance of TE materials is examined through the figure of merit, ZT = TS²σ/κ, various techniques will be used to determine the Seebeck coefficient, the electrical conductivity and the thermal conductivity. The quaternary clathrates, Ba8-xLnxGa16Ge30 and Ba8-xLnxGa16+xGe30-x, where Ln = La, Ce and Eu were synthesized from the pure elements in stoichiometric ratios at 1000°C with slow cooling to room temperature. The products were then annealed at 600°C to acquire homogeneous samples for analyses. The various compositions of lanthanoid were intercalated into the structure of clathrates, which resulted in the quaternary clathrates with homogeneity. The crystal structure of quaternary clathrates with the space group of Pm-3n exhibited the same structure type as the ternary clathrates. The successfully formed products were refined with Rietveld refinements to understand their structures. The Eu containing clathrates crystallized with a lattice parameter a = 10.78251(6) Å, V = 1253.60(2) ų, for x = 0.3. The Ce containing clathrates also adopted the same space group with a lattice parameter a = 10.77331(6) Å, V = 1250.40(2) ų, for x = 0.3. The La containing clathrates formed with a lattice parameter a = 10.78494(6) Å, V = 1254.45(2) ų, for x = 0.3. Between 0.2 and 1.0 lanthanoid elements per formula unit were substituted with decreasing amount of barium where the actual amount of Ln in clathrates was lower than nominal amount. All these quaternary clathrates were found to be n-type semiconductors as determined through the Seebeck coefficient and electrical conductivity measurements.
4

Optimization of Type-I Clathrates for Thermoelectric Properties

Jeung, Suk-kyung January 2012 (has links)
The increase in waste heat after consuming energy or burning fossil fuels is an issue environmentally and economically. Thermoelectric (TE) materials are developed to use in various applications because of their ability in converting waste heat into electricity. However, the applications are limited due to a low efficiency of materials, and research on thermoelectric materials is an on-going project for future use. Type-I clathrates are one of the TE materials which are studied in depth since the proposal of Slack’s PGEC (Phonon-Glass-Electron-Crystal) concept in 1995 due to their excellent thermoelectric properties. In this study, development and optimization of quaternary type-I clathrates will be the focus because double substitution often leads to better figure-of-merit, ZT, but it hasn’t really been studied. Higher ZT value is necessary because the energy conversion efficiency of TE materials is depending on the ZT value along with a larger temperature difference. Addition of lanthanoid elements as 2nd guest atoms to the main type-I clathrate structure, realized in Ba8Ga16Ge30, will be attempted to form quaternary compounds. The formation of the quaternary clathrates will be analyzed through powder X-ray diffraction, single crystal analysis and energy dispersive X-ray analysis. Also, as the performance of TE materials is examined through the figure of merit, ZT = TS²σ/κ, various techniques will be used to determine the Seebeck coefficient, the electrical conductivity and the thermal conductivity. The quaternary clathrates, Ba8-xLnxGa16Ge30 and Ba8-xLnxGa16+xGe30-x, where Ln = La, Ce and Eu were synthesized from the pure elements in stoichiometric ratios at 1000°C with slow cooling to room temperature. The products were then annealed at 600°C to acquire homogeneous samples for analyses. The various compositions of lanthanoid were intercalated into the structure of clathrates, which resulted in the quaternary clathrates with homogeneity. The crystal structure of quaternary clathrates with the space group of Pm-3n exhibited the same structure type as the ternary clathrates. The successfully formed products were refined with Rietveld refinements to understand their structures. The Eu containing clathrates crystallized with a lattice parameter a = 10.78251(6) Å, V = 1253.60(2) ų, for x = 0.3. The Ce containing clathrates also adopted the same space group with a lattice parameter a = 10.77331(6) Å, V = 1250.40(2) ų, for x = 0.3. The La containing clathrates formed with a lattice parameter a = 10.78494(6) Å, V = 1254.45(2) ų, for x = 0.3. Between 0.2 and 1.0 lanthanoid elements per formula unit were substituted with decreasing amount of barium where the actual amount of Ln in clathrates was lower than nominal amount. All these quaternary clathrates were found to be n-type semiconductors as determined through the Seebeck coefficient and electrical conductivity measurements.
5

Síntese e Caracterização da liga Sn2SSe nanoestruturada obtida por Moagem Mecânica de Alta Energia

Ferreira, Joelma Maria de Oliveira 20 December 2016 (has links)
Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-02-20T15:24:48Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Joelma M. O. Ferreira.pdf: 2643340 bytes, checksum: eca2ac8dc24abdf2d8509611c7bad6f8 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-02-20T15:25:05Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Joelma M. O. Ferreira.pdf: 2643340 bytes, checksum: eca2ac8dc24abdf2d8509611c7bad6f8 (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-02-20T15:25:20Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Joelma M. O. Ferreira.pdf: 2643340 bytes, checksum: eca2ac8dc24abdf2d8509611c7bad6f8 (MD5) / Made available in DSpace on 2017-02-20T15:25:20Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação - Joelma M. O. Ferreira.pdf: 2643340 bytes, checksum: eca2ac8dc24abdf2d8509611c7bad6f8 (MD5) Previous issue date: 2016-12-20 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The study of tin chalcogenides SnX (X = O, S, Se, or Te) has attracted great attention of researchers due its intrinsic semiconductor characteristics. However, the binary compositions SnSe and SnS are the most studied at the present time because of the recently reported high value of ZT presented by the orthorhombic structure Pnma (SASSI et al., 2014; ZHAO et al., 2014), besides its anisotropic (AGARWAL et al., 2000) and polymorphic (MICHIELON DE SOUZA et al., 2016) characteristics. In this context, this research suggests the formation of a solid solution substitution Sn2SSe produced by mechanical alloying in two milling times, 1h and 10h. The structure, morphology and thermal behavior of the alloys were investigated using the following techniques: X-Ray Diffraction (XRD), Energy-Dispersive Analysis of X-ray (EDX), Scanning electron microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermal Treatment (TT), Fusion Process and Rietveld (MR) structural refinement method. The characterization by XRD confirmed that the produced alloys are constituted by a layered orthorhombic Sn2SSe single phase (space group Pnma). However, the sample produced in 10h also has the contaminant phase SnO2. The data adjusted by the Rietveld method allowed estimating the average crystallite size of 17,8nm and 19,6nm for the ternary phase Sn2SSe for samples with 1h and 10h of milling respectively. EDX did not show the contaminant phase present in the sample with 10h of milling, unlike XRD together with MR that revealed a relatively low amount of the contaminant about 7,6%. The DSC performed between 30o and 550oC in the uncontaminated sample was studied in concomitance with the TT and the melting process. The results showed the thermal instability of the sample and possible evaporation of Se and S elements above 240oC. The SEM showed that the alloy particles are irregular and of varying sizes. / O estudo dos calcogênios de estanho SnX (X=O, S, Se ou Te) tem atraído bastante atenção dos pesquisadores devido às suas características semicondutoras intrínsecas. Entretanto, as composições binárias SnSe e SnS são as mais estudadas na atualidade devido o alto valor de ZT apresentado pela estrutura ortorrômbica Pnma relatado recentemente(SASSI et al., 2014; ZHAO et al., 2014), tal como as suas características anisotrópicas(AGARWAL et al., 2000) e polimórficas(MICHIELON DE SOUZA et al., 2016). Nesse contexto, essa pesquisa, surgere a formação de uma solução sólida substitucional Sn2SSe produzida pela técnica de Moagem Mecânica de Alta Energia em dois tempos de moagem, 1h e 10h. A estrutura, morfologia e o comportamento térmico das ligas foram investigados através das seguintes técnicas: Difração de raios X (DRX), Espectroscopia de Fluorescência de Raios X por energia dispersiva (EDX), Microscopia Eletrônica de Varredura (MEV), Calorimetria Diferencial de Varredura (DSC), Tratamento Térmico (TT), Processo de Fusão e método de refinamento estrutural de Rietveld (MR). A caracterização por DRX confirmou que as ligas produzidas são constituídas pela fase única Sn2SSe de estrutura ortorrômbica (grupo espacial Pnma) disposta em camadas, no entanto a amostra produzida em 10h possui também a fase contaminante SnO2. Os dados ajustados pelo método de Rietveld permitiram estimar o tamanho médio de cristalito de 17,8nm e 19,6nm para a fase ternária Sn2SSe referentes às amostras com 1h e 10h de moagem respectivamente. A EDX não mostrou a fase contaminante presente na amostra com 10h de moagem ao contrario da DRX juntamente com o MR que revelaram uma quantidade relativamente baixa do contaminante cerca de 7,6%. A DSC realizada entre 30 e 550 oC na amostra não contaminada foi estudada em concomitância ao TT e ao processo de fusão e mostraram a instabilidade térmica da amostra bem como uma possível evaporação dos elementos Se e S a uma temperatura acima de 240oC. A MEV mostrou que as partículas das ligas são irregulares e de tamanhos variados.
6

Scalable Carbon Nanotube Networks Embedded in Elastomers and their use in Transverse Thermoelectric Power Generation

Prabhakar, Radhika January 2019 (has links)
No description available.
7

Etude des propriétés thermoélectriques des revêtements de matériaux de type β-FeSi2 / Study of thermoelectric properties of the coatings of β-FeSi2 type materials

Feng, Xiaohua 26 May 2016 (has links)
L'incertitude de l'énergie mondiale avec l'augmentation constante de la demande d'énergie déclenche la recherche de technologies de conversion d'énergie à haut rendement. Les dispositifs thermoélectriques (TE) peuvent jouer un rôle très important dans la collecte et la valorisation de l'énergie car ils peuvent être employés pour récupérer la chaleur résiduelle. Par exemple, la quantité de chaleur émise sous forme de déchets par les différents moteurs thermiques est évaluée en centaines de millions de MWh /an.Cette thèse vise à démontrer la faisabilité de fabrication des systèmes de récupération de la chaleur issue des déchets à l'échelle industrielle en utilisant des générateurs thermoélectriques (TE). Les techniques de fabrication proposées sont basées sur l'utilisation de technologies avancées comme le frittage par spark plasma, le broyage, la fusion laser sélective et la technologie de projection thermique. Ces techniques rendent possible l'élaboration de revêtements de matériau thermoélectrique avec des performances thermoélectriques supérieures et une flexibilité forte liées aux choix multiples de tailles, de formes et de matériaux.Nous nous sommes intéressés à l'étude du matériau semi-conducteur ß-FeSi2 car il présente un coefficient de mérite fort dans une plage de température de 300-800oC qui est la température des gaz en sortie de moteur voiture.Les techniques de SLM (Selective Laser Melting), de broyage, de frittage et de frittage flash (SPS) ont été successivement utilisées pour aboutir à l'élaboration de l'alliage ¿-FeSi2. Les revêtements ont ensuite été obtenus par la technique de projection plasma sous basse pression.Concernant le revêtement formé à partir de l'alliage par procédé LPPS, la transformation de phase de la phase cubique -ferrosilicium et de la phase quadratique ¿-Fe2Si5 en phase orthorhombique ß-FeSi2 se produit en obéissant aux réactions péritectique et eutectique. Après recuit sous température et temps appropriés, les revêtements présentent une phase complète ß-FeSi2 sur le substrat céramique.En outre pour une application à grande échelle, il est nécessaire de déposer ce type de revêtement sur un substrat en acier inoxydable et il convient dans ce cas d'utiliser un masque approprié pour fabriquer le dispositif thermoélectrique. / The uncertainty in the global energy with the constant increase in energy demand triggers the search for energyconversion technologies with high efficiency. The thermoeletrical devices (TE) can play a relevant role in thecollection and recovery of energy because they can be used to recover waste heat. For example, the amount of heatemitted as waste by different ombustion engines is evaluated hundreds of millions of MWh / year.This thesis aims to demonstrate the feasibility of anufacturing heat recovery systems from waste on an industrialscale using thermoelectric generators (TE). The proposed manufacturing techniques are based on the use ofadvanced technologies such as spark plasma sintering, crushing, selective laser melting and thermal spraytechnology. These techniques make possible the development of thermoelectric material coatings with superiorthermoelectric performance and high flexibility related to multiple choices of sizes, shapes and materials.The study of semiconductor ß-FeSi2 material was conducted in this goal because it has a strong merit coefficient(ZT) in the temperature range of 300-800°C which is the temperature of the output gas of the cars.Selective Laser Melting, sintering and spark plasma sintering (SPS) were successively used to lead to themanufacture of ¿-FeSi2 alloy. The coatings were then obtained by low pressure plasma spraying.Concerning the coating formed from the alloy, the phase transformation of the cubic phase ¿-ferro-silicon and thetetragonal phase ¿-Fe2Si5 in the orthorhombic phase ß-FeSi2 is produced by obeying the eritectic and eutecticreactions. After annealing under suitable temperature and time, the coatings sprayed on the ceramic bstratepresent a complete phase ß-FeSi2.In view of a large-scale application, it is necessary to spray this type of coating on a stainless steel substrate and inthis case to use a suitable mask for making the appropriate thermoelectric device.
8

Modélisation du transport thermique dans des matériaux thermoélectriques / Modeling of thermal transport properties of thermoelectric materials

Andrea, Luc 08 April 2016 (has links)
Les matériaux thermoélectriques permettent de convertir de l'énergie thermique en énergie électrique. Leur rendement de conversion trop faible limite cependant leur utilisation à grande échelle. Plusieurs voies d'optimisation sont utilisés afin d'augmenter les rendements de conversion en diminuant la conductivité thermique. Dans cette thèse, nous modélisons les propriétés de transport thermique des matériaux half-Heusler parfaits et dopés qui présentent des propriétés thermoélectriques intéressantes. La méthode repose sur la théorie de la fonctionnelle de la densité pour calculer les propriétés harmoniques et anharmoniques des composés parfaits et déterminer les temps de vie des phonons. Ensuite, ces derniers sont utilisés pour écrire une équation de transport de Boltzmann pour la densité de phonons dont la résolution donne accès à la conductivité thermique. L'inclusion de défauts ponctuels a pour objectif de réduire la conductivité thermique par diffusion des phonons. Pour modéliser leur effet dans un régime de forte concentration une méthode champ moyen a été développée et appliquée aux half-Heusler. Pour traiter le régime dilué, une méthode faisant appel aux fonctions de Green a été utilisée. Ces deux méthodes montrent que des réductions significatives de conductivité thermique des composés NiTiSn, NiZrSn et NiHfSn sont déjà obtenues pour des concentrations de 10 % en dopants. / Thermoelectric materials provide a way to convert thermal energy into electrical energy. Nonetheless, their low efficiency is the main obstacle for global scale applications. Experimentally, specific treatments can lead to great improvement in the efficiency, mainly by lowering the thermal conductivity. This thesis is aimed at calculating from first principles, the thermal transport properties in perfect and doped half-Heusler thermoelectric materials. We begin with a theoretical analysis of the harmonic and anharmonic properties of phonons for perfect phases.The density functional theory is used to deduce the phonons lifetime from phonon-phonon interactions. The lifetimes are integrated into the Boltzmann transport equation for the phonon density, which solution allows us to compute fully ab initio the lattice thermal conductivity. The purpose of point defects is to scatter the phonons and thus reduce thermal conductivity. We developed two methods to account for the defects on thermal transport. The first one, based on a mean field approach, is suitable for the high concentration regimes. The second one in the framework of Green functions theory is used for dilute regimes. Both methods consistently show that the main reduction of thermal conductivity is already obtained within around 10 % of solute elements in NiTiSn, NiZrSn and NiHfSn.
9

Bi0.5Sb1.5Te3+0.33 wt% aerogel與Cu0.02Bi2Te2.7Se0.3熱電薄膜與元件之熱電性質研究 / Thermoelectric properties of Bi0.5Sb1.5Te3+0.33 wt% aerogel and Cu0.02Bi2Te2.7Se0.3 thermoelectric thin film and device

何駿佑, Ho, Chun Yu Unknown Date (has links)
近幾年來,熱電材料蓬勃發展是許多物理、化學以及材料科學家的熱門研究的方向,然而此一跨領域的基礎研究工作處於萌芽的階段。熱電材料的益處在於可將熱機或是冷凍機之上所產生的廢熱轉化成電能。本研究利用鉍化碲(Bismuth Tellurium)在室溫附近具有一熱電優質係數(ZT)為1.0的熱電表現,其具有非常低的熱傳導率以及適當的載子傳輸性質,因此Bi-Te的合金系列成為大家研究的趨勢,成為另一項重大的焦點引發相當的關注。鉍化碲元素皆是地球殼中豐富的元素,且鉍化碲是對人無毒且對環境無害的化合物,相較於其他高性能熱電材料(一般由稀少元素/貴金屬組成),具有非常大商業化的潛力。鉍化碲本身為非常穩定的多層層狀結構(Quintuple Layer),表現出極低的熱傳導率以及良好的導電性。為了未來能製作出微小的熱電模組,本研究利用射頻磁控濺鍍系統(Radio-Frequency Magnetron Sputtering System)調控濺鍍參數的方式,得到最佳熱電性質之薄膜後,再使用半導體製程技術製作微結構的陣列熱電薄膜,利用光微影製程及金屬遮罩兩種分別不同的方式決定所需之電極和薄膜陣列之圖形。本論文使用磁控濺鍍設備,靶材n-type和p-type分別選用Cu0.02Bi2Te2.7Se0.3 和Bi0.5Sb1.5Te3+0.33 wt% Aerogel之熱電材料,經由實驗改變磁控濺鍍的工作壓力、RF power,再透過ZEM-3、EDS對薄膜的研究分析得到(最佳鍍膜參數) 最佳鍍膜品質參數(seebeck、電阻)。決定鍍膜參數後使用本研究開發的兩種方式製作微結構熱電元件,一使用光微影半導體製程,二使用金屬遮罩,針對兩種製程方式所得的n-type和p-type陣列熱電薄膜成長過程做比較與研究探討。 / In recent years, physicists, chemists and material scientists at many major universities and research institutions throughout the world are attempting to create novel materials with high thermoelectric (TE) efficiency. It will be beneficial to harvest waste heat into electrical energy. Especially heating and cooling are other major applications for this class of new TE materials. At present the thermoelectric (TE) material bismuth telluride (Bi2Te3) baesd systems exhibit best figure of merit (ZT). Bismuth and tellurium are earth-abundant elements and Bi2Te3 is non-toxic to human beings and the environment. Therefore, it has great potential in commercial implements. Bismuth telluride is a quintuple layer-structured compound possessing ultralow thermal conductivity and moderate electrical conductivity. In this work, the TE thin film and device are fabricated and optimized by Radio-Frequency Magnetron Sputtering System (RFMSS) and the influence of the preparative parameters such as working pressure and working power of RF sputtering are investigated. In this study, we used the magnetron sputtering equipment and the thermoelectric materials n-type target and p-type target were Cu0.02Bi2Te2.7Se0.3 and Bi0.5Sb1.5Te3+0.33 wt% aerogel, respectively. In this study, the experimental changes the magnetron sputtering working pressure, RF power before the ZEM-3, EDS analysis the thin film thermoelectric properties to get the best thin film quality parameters (Seebeck coefficient, resistivity, power factor). After the thin film parameters were determined, the microstructural thermoelectric 442 pairs device were fabricated by the photolithography semiconductor process, and n-type and p-type arrays used by photolithography to define a pattern and deposit Au electrodes onto the substrate by thermal evaporation.
10

Alternative Uses of CZTS Thin Films for Energy Harvesting

Mustaffa, Muhammad Ubaidah Syafiq 07 September 2021 (has links)
The search for renewable energy resources and ways to harvest them has become a global mainstream topic among researchers nowadays, with solar cells and thermoelectric generators among the energy harvesting technologies currently being researched in vast. CZTS (Cu2ZnSnS4), a p-type semiconducting material initially researched to replace copper indium gallium selenide (CIGS) as the light absorbing layer in thin film solar cells, was studied in this doctoral work for alternative uses in energy harvesting. This work aims to systemically investigate the prospects of CZTS to be used as hole transport layers and thermoelectric generators. CZTS thin film was successfully fabricated using a versatile approach involving hot-injection synthesis of CZTS nanoparticles ink followed by spin coating and thermal treatment. Results obtained revealed the possibility to fine control CZTS thin film fabrication based on ink concentration and spin. Besides that, thermal treatment temperature was found to affect the film’s overall properties, where an increase in thermal treatment temperature improved the degree of crystallinity and electrical properties. In addition, a phase change going from less stable cubic and wurtzite structures to a more stable tetragonal structure was also observed. Furthermore, CZTS was found to be a good candidate to replace the commonly used organic hole transport layer in perovskite solar cells, with potentials in improving performance and stability. In addition, CZTS also possessed good transport properties to be a potential p-type material in a thermoelectric generator, with the preliminary performance of fabricated CZTS/AZO thermoelectric generator showing a maximum power output of ~350 nW at ~170 KΔT. These findings provide new perspectives for CZTS in energy harvesting applications, despite the struggle in its development as the absorber layer in thin film solar cells. Besides providing a deeper understanding of CZTS and its vast possibilities in energy harvesting applications, promising future research stemming from this work is also limitless, reinventing ways in material studies, in search of alternative applications which may be of benefit.

Page generated in 0.0942 seconds