Edited by the initiators of a priority research program funded by the German Science Foundation and written by an international team of key players, this is the first book to provide an overview of nanostructured thermoelectric materials -- putting the new developments into perspective alongside conventional thermoelectrics. As such, it reviews the current state of research on thermoelectric Bi2Te3 nanomaterials, covering advanced methods of materials synthesis, characterization of materials structures and thermoelectric properties, as well as advances in the theory and modeling of transport properties. Nanomaterials-based thermoelectric devices are also discussed with respect to their properties, their suitability for different energy generation applications, and in light of their commercialization potential. An outlook on the chances, challenges and future directions of research rounds off the book, giving a straightforward account of the fundamental and technical problems - plus ways to overcome them.

Table of Contents:
Preface XIII List of Contributors XVII Acknowledgments XXIII 1 Old and New Things in Thermoelectricity 1 Rudolf P. Huebener 1.1 ThreeThermoelectric Effects 2 1.1.1 Seebeck Effect 2 1.1.2 Peltier Effect 3 1.1.3 Thomson Effect 3 1.2 Semiconductors 4 1.3 My Entry into Thermoelectricity 6 1.4 Peltier Cascades 9 1.5 Challenge of Materials Science 9 References 10 Part I: Synthesis of Nanowires, Thin Films, and Nanostructured Bulk 11 2 Electrodeposition of Bi2Te3-Based Thin Films and Nanowires 13 William Töllner, Svenja Bäßler, Nicola Peranio, Eckhard Pippel, Oliver Eibl, and Kornelius Nielsch 2.1 Introduction 13 2.2 Fundamentals of Bi2Te3-Based Electrodeposition 14 2.3 Electrodeposition of Bi2Te3 Thin Films 16 2.4 Electrodeposition of Thermoelectric Nanowires 21 2.4.1 Electrodeposition of Bi2Te3 Nanowires 21 2.4.2 Ternary Bi2Te3-Based Nanowires 28 2.5 Conclusion 31 References 31 3 Bi2Te3 Nanowires by Electrodeposition in Polymeric Etched Ion Track Membranes: Synthesis and Characterization 33 Oliver Picht, Janina Krieg, and Maria Eugenia Toimil-Molares 3.1 Introduction 33 3.2 Synthesis of Bi2Te3 NWs with Controlled Size and Crystallography 36 3.2.1 Fabrication of Etched Ion-Track Membranes 36 3.2.1.1 Swift Heavy-Ion Irradiation 36 3.2.1.2 Chemical Etching 37 3.2.2 Electrodeposition of Bi2Te3 NWs 38 3.2.2.1 Experimental Setup 38 3.2.2.2 Electrodeposition of Bi2Te3 and Choice of the Electrolyte 40 3.2.2.3 Chronoamperometric Current–Time Curves 41 3.2.3 Morphological and Crystallographic Characterization of Bi2Te3 NWs 42 3.2.3.1 NWArrays 42 3.2.3.2 Morphology of Individual Nanowires as a Function of the Deposition Parameters 43 3.2.3.3 Adjusting the Nanowire Dimensions 44 3.2.3.4 Investigation of the Nanowire Crystallinity and Composition by TEM 45 3.2.3.5 Investigation of the Preferred Crystallographic Orientation of Wire Arrays by X-Ray Diffraction 49 3.3 Conclusions 50 References 51 4 Fabrication and Comprehensive Structural and Transport Property Characterization of Nanoalloyed Nanostructured V2VI3 Thin Film Materials 55 MarkusWinkler, Torben Dankwort, Ulrich Schürmann, Xi Liu, Jan D. König, Lorenz Kienle,Wolfgang Bensch, Harald Böttner, and Kilian Bartholomé 4.1 Situation/State of the Art before the Start of Our Combined Research Project 55 4.2 Motivation for Research on V2VI3 Multilayered Structures 56 4.2.1 BinaryThin Films 58 4.2.2 Results Obtained for SL Structures 62 4.2.3 Results Obtained from aTheoretical Analysis of V2VI3 Binaries and Nanoscale SL Structures 66 4.3 Conclusion and Outlook 67 Acknowledgments 69 References 69 5 Structure and Transport Properties of Bi2Te3 Films 73 GuoyuWang, Lynn Endicott, and Ctirad Uher 5.1 Introduction 73 5.2 Structural Aspects of the Tetradymite-type Lattice 75 5.3 MBE Film Deposition 76 5.4 Structural Characterization of Bi2Te3 Films 78 5.5 Transport Properties of Films on Sapphire Substrates 85 5.6 Conclusion 95 Acknowledgment 95 References 95 6 Bulk-Nanostructured Bi2Te3-Based Materials: Processing, Thermoelectric Properties, and Challenges 99 Vicente Pacheco, Henrik Görlitz, Nicola Peranio, Zainul Aabdin, and Oliver Eibl 6.1 Success of ZT Enhancement in Nanostructured Bulk Materials 99 6.2 Methodology at Fraunhofer IFAM-DD: Previous Research 100 6.3 High-Energy Ball Milling Technology, SPS Technology, and Thermoelectric Characterization 102 6.4 Control of Crystallite Size and Mass Density 103 6.4.1 Optimizing Ball Milling Parameters 103 6.4.2 Optimizing SPS Parameters 105 6.5 Nanostructure – Transport Properties – Correlations in Sintered Nanomaterials 106 6.5.1 Transport Properties 106 6.5.2 Nanostructure 108 6.5.3 Crystallite Size–Lattice Thermal Conductivity Correlation 110 6.5.4 Composition–Antisite Defect Density–Electric Transport Correlation 111 6.5.5 Oxidized Secondary Phases–Oxidized Matrix–Electric Transport Correlation 112 6.6 Summary and State of the Art 113 6.7 Outlook Second Generation SPS Prepared Nanomaterials 114 References 115 Part II: Structure, Excitation, and Dynamics 119 7 High Energy X-ray and Neutron Scattering on Bi2Te3 Nanowires, Nanocomposites, and BulkMaterials 121 Benedikt Klobes, Dimitrios Bessas, and Raphaël P. Hermann 7.1 Introduction 121 7.2 Review of Published High-Energy X-ray and Neutron Scattering Studies on Bi2Te3 and Related Compounds 122 7.3 Element Specific Lattice Dynamics in Bulk Bi2Te3 and Sb2Te3 125 7.4 Nanostructure and Phonons in a Bi2Te3 Nanowire Array 130 7.5 Nanocomposites and Speed of Sound 134 7.6 Perspectives of High-Energy X-ray and Neutron Scattering 136 Acknowledgments 136 References 137 8 Advanced Structural Characterization of Bi2Te3 Nanomaterials 141 Nicola Peranio, Zainul Aabdin,Michael Dürrschnabel, and Oliver Eibl 8.1 From Bulk to Nanomaterials 141 8.2 Synthesis of Nanomaterials and Transport Measurements 142 8.3 Relevance of Advanced Microscopy and Spectroscopy for Bi2Te3 Nanomaterials 143 8.4 Nanostructure–Property Relations in Bulk and Nanomaterials 147 8.4.1 Chemical Modulations and Structural Disorder in Commercial Bulk Materials 147 8.4.2 Near Stoichiometric, Single Crystalline Nanowires for Transport in the Basal Plane 150 8.4.3 Epitaxial and Nano-alloyedThin Films with Low Charge Carrier Densities and High Power Factors 152 8.4.4 Highly Dense, Ultra-fine Nanostructured Bulk with Low Thermal Conductivities 153 8.5 Simulation of Electron Transport and Electron Scattering in Bi2Te3-Based Materials 155 8.5.1 Calculation of Electronic Transport Coefficients 156 8.5.2 Calculation of High-Energy Electron Scattering in Bi2Te3-Based Materials 158 8.6 Experimental Techniques and Simulation 161 References 161 Part III: Theory and Modeling 165 9 Density-Functional Theory Study of Point Defects in Bi2Te3 167 Adham Hashibon and Christian Elsässer 9.1 Introduction 167 9.2 Thermoelectric Properties 168 9.3 The Lattice Structure of Bi2Te3 173 9.4 Point Defects in Bi2Te3-Related Materials 174 9.5 Concentration of Point Defects 177 9.6 Calculation of Formation Energies from First Principles 178 9.7 Recent DFT Results for the Point Defect Energies in Bi2Te3 180 9.8 Summary and Outlook 183 Acknowledgments 184 References 184 10 Ab Initio Description of Thermoelectric Properties Based on the Boltzmann Theory 187 Nicki F. Hinsche, Martin Hölzer, Arthur Ernst, Ingrid Mertig, and Peter Zahn 10.1 Introduction 187 10.1.1 Low-Dimensional Thermoelectrics 188 10.1.2 Phonon-Glass Electron-Crystal 189 10.1.3 Phonon-Blocking and Electron-Transmitting Superlattices 191 10.2 Transport Theory 193 10.2.1 Linearized Boltzmann Equation and Relaxation Time Approximation 193 10.2.2 Transport Coefficients 194 10.3 Results 197 10.3.1 Influence of Strain 197 10.3.2 Superlattices 203 10.3.3 Thermal Conductivity - Toward the Figure of Merit 206 10.3.4 Lorenz Function of Superlattices 208 10.3.5 Phonons 211 10.4 Summary 213 References 214 Part IV: Transport PropertiesMeasurement Techniques 223 11 Measuring Techniques for Thermal Conductivity and Thermoelectric Figure of Merit of V–VI Compound Thin Films and Nanowires 225 F. Völklein, H. Reith, A. Meier, and M. Schmitt 11.1 Introduction 225 11.2 Methods for the Investigation of the In-plane Thermal Conductivity of Thin Films 227 11.2.1 Steady-State Joule Heating Method for Determining the Thermal Conductivity and Emissivity of Electrically Conducting Films 227 11.2.2 Microfabricated λ-Chips for Measurements of In-Plane Thermal Conductivity 230 11.2.3 The λ-Chips for Transient Measurements of the In-Plane Thermal Conductivity and the Specific Heat Capacity of Thin Films 235 11.3 Steady-State Measurements of the Cross-PlaneThermal Conductivity of Thin Films 236 11.4 Investigation of Cross-PlaneThermal Conductivity of Nanowire Arrays 243 11.5 Characterization ofThermal Conductivity and Thermoelectric Figure of Merit of Single Nanowires 245 11.5.1 Design of the z-Chip 245 11.5.2 Electrical Conductivity Measurement 248 11.5.3 Thermopower Measurements 248 11.5.4 Thermal Conductivity Measurement 250 Acknowledgments 251 References 251 12 Development of a Thermoelectric Nanowire Characterization Platform (TNCP) for Structural and Thermoelectric Investigation of Single Nanowires 253 ZhiWang, S. Hoda Moosavi,Michael Kroener, and PeterWoias 12.1 Introduction 253 12.2 TNCP Initial Design 256 12.3 First and Second Generations of TNCP 257 12.3.1 Design, Modeling, and Simulation 257 12.3.2 Design Improvements and New Characteristics for the Second Generation Chip Design 259 12.3.3 Fabrication 262 12.4 Nanowire Assembly Utilizing Dielectrophoresis 264 12.4.1 Theory 264 12.4.2 Experimental Details 267 12.4.2.1 Liquid Medium Selection 267 12.4.2.2 Nanowire Assembly Process 267 12.4.2.3 Acceleration ofWater Droplet Evaporation 269 12.4.2.4 Recognition of Properly Assembled Nanowires 269 12.4.2.5 Results and Discussion 270 12.5 Ohmic Contact Generation 271 12.5.1 SEM Electron Beam Induced Deposition (EBID) 271 12.5.2 Shadow Mask Techniques 275 12.5.2.1 Design and Fabrication 275 12.5.2.2 Experimental Process 277 12.6 Summary and Outlook 277 References 279 Appendix 283 Index 287