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  • Towards High Performance Nanostructured Thermoelectric Materials. A Bottom-Up Approach

    Doris Cadavid

    ADVERTIMENT. La consulta d’aquesta tesi queda condicionada a l’acceptació de les següents condicions d'ús: La difusió d’aquesta tesi per mitjà del servei TDX (www.tdx.cat) i a través del Dipòsit Digital de la UB (diposit.ub.edu) ha estat autoritzada pels titulars dels drets de propietat intel·lectual únicament per a usos privats emmarcats en activitats d’investigació i docència. No s’autoritza la seva reproducció amb finalitats de lucre ni la seva difusió i posada a disposició des d’un lloc aliè al servei TDX ni al Dipòsit Digital de la UB. No s’autoritza la presentació del seu contingut en una finestra o marc aliè a TDX o al Dipòsit Digital de la UB (framing). Aquesta reserva de drets afecta tant al resum de presentació de la tesi com als seus continguts. En la utilització o cita de parts de la tesi és obligat indicar el nom de la persona autora. ADVERTENCIA. La consulta de esta tesis queda condicionada a la aceptación de las siguientes condiciones de uso: La difusión de esta tesis por medio del servicio TDR (www.tdx.cat) y a través del Repositorio Digital de la UB (diposit.ub.edu) ha sido autorizada por los titulares de los derechos de propiedad intelectual únicamente para usos privados enmarcados en actividades de investigación y docencia. No se autoriza su reproducción con finalidades de lucro ni su difusión y puesta a disposición desde un sitio ajeno al servicio TDR o al Repositorio Digital de la UB. No se autoriza la presentación de su contenido en una ventana o marco ajeno a TDR o al Repositorio Digital de la UB (framing). Esta reserva de derechos afecta tanto al resumen de presentación de la tesis como a sus contenidos. En la utilización o cita de partes de la tesis es obligado indicar el nombre de la persona autora. WARNING. On having consulted this thesis you’re accepting the following use conditions: Spreading this thesis by the TDX (www.tdx.cat) service and by the UB Digital Repository (diposit.ub.edu) has been authorized by the titular of the intellectual property rights only for private uses placed in investigation and teaching activities. Reproduction with lucrative aims is not authorized nor its spreading and availability from a site foreign to the TDX service or to the UB Digital Repository. Introducing its content in a window or frame foreign to the TDX service or to the UB Digital Repository is not authorized (framing). Those rights affect to the presentation summary of the thesis as well as to its contents. In the using or citation of parts of the thesis it’s obliged to indicate the name of the author.

  • Doctorado en Física – Universidad de Barcelona – 2014

    Towards High Performance

    Nanostructured Thermoelectric

    Materials A Bottom-Up Approach

    Thesis by

    Doris Cadavid

    In Partial Fulfilment of the Requirements for the Degree of

    Doctor of Philosophy

    Supervisor

    Prof. Dr. Andreu Cabot

    Tutor

    Prof. Dr. Atilá Herms

    Department of Electronics

    University of Barcelona

  • Contents

    Acknowledgements ............................................................................ i

    Preface ............................................................................................. iii

    List of publications ........................................................................... v

    Summary of results ......................................................................... ix

    Resumen ........................................................................................ xiii

    Chapter 1 Introduction .............................................................. 1

    1.1 Thermoelectricity ............................................................... 6

    1.1.1 Thermoelectric effects .................................................... 9

    1.2 Derivation of the transport properties .............................. 11

    1.2.1 Boltzmann transport equation ...................................... 11

    1.2.2 Relation of the transport properties with non-

    equilibrium statistic .................................................................. 13

    1.3 Thermoelectric devices .................................................... 15

    1.3.1 Application: thermoelectric generator ......................... 15

    1.3.2 Application: thermoelectric refrigerator ...................... 19

    1.4 How to improve ZT .......................................................... 22

    1.5 Synthesis of the nanomaterials ......................................... 24

    1.5.1 Solution process: colloidal synthesis ........................... 25

    1.5.2 Nanocrystals macroscopic arrangement ....................... 31

    1.5.3 Challenges of the use of colloidal NCs for thermoelectrics ......................................................................... 32

    1.6 References ........................................................................ 34

    Chapter 2 Methods and techniques ........................................ 49

    2.1 Production of the bulk nanostructured material ............... 50

    2.1.1 Consolidation Techniques ............................................ 50

  • 2.2 Thermoelectric characterization ....................................... 53

    2.2.1 Seebeck coefficient ...................................................... 53

    2.2.2 Electrical resistivity ...................................................... 54

    2.2.3 Thermal conductivity ................................................... 55

    2.3 Structural and chemical characterization ......................... 56

    2.4 References ........................................................................ 58

    Chapter 3 Bottom-up processing of thermoelectric

    nanocomposites Ag2Te-PbTe ......................................................... 59

    3.1 Introduction ...................................................................... 59

    3.2 Experimental details ......................................................... 61

    3.2.1 Materials ....................................................................... 61

    3.2.2 Preparation of PbTe nanocrystals ................................. 62

    3.2.3 Preparation of Ag2Te nanocrystals ............................... 62

    3.2.4 Nanocomposite preparation.......................................... 63

    3.3 Results and discussion ...................................................... 63

    3.4 Conclusion ........................................................................ 73

    3.5 References ........................................................................ 74

    Chapter 4 Organic ligand displacement by metal salts to

    enhance nanoparticle functionality: Thermoelectric properties

    of Ag2Te .................................................................................. 83

    4.1 Introduction ...................................................................... 83

    4.2 Experimental details ......................................................... 86

    4.2.1 Materials ....................................................................... 86

    4.2.2 Preparation of Ag2Te nanocrystals ............................... 86

    4.2.3 Organic ligand displacement by metal salts ................. 87

    4.2.4 Preparation of bulk nanostructured material ................ 87

    4.3 Results and discussion ...................................................... 88

  • 4.4 Conclusion........................................................................ 97

    4.5 References ........................................................................ 98

    Chapter 5 Surface ligand influence on PbSe thermoelectric properties ................................................................................ 105

    5.1 Introduction .................................................................... 105

    5.2 Experimental details ....................................................... 108

    5.2.1 Materials ..................................................................... 108

    5.2.2 PbSe nanoparticles ..................................................... 108

    5.2.3 Organic ligand displacement ...................................... 109

    5.2.4 PbSe bulk nanomaterial ............................................. 109

    5.3 Results ............................................................................ 109

    5.3.1 PbSe OL ..................................................................... 109

    5.3.2 PbSe-LE ..................................................................... 115

    5.4 Discussion ...................................................................... 119

    5.4.1 Charge transport model .............................................. 119

    5.5 Conclusion...................................................................... 127

    5.6 References ...................................................................... 129

    Chapter 6 Colloidal Synthesis and Thermoelectric Properties

    of Cu2SnSe3 Nanocrystals ............................................................ 135

    6.1 Introduction .................................................................... 135

    6.2 Experiment

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