Recent Trends in Thermoelectric Materials Research II

Transcription

1 Recent Trends in Thermoelectric Materials Research II SEMICONDUCTORS AND SEMIMETALS Volume 70 Volume Editor TERRY M. TRITT DEPARTMENT OF PHYSICS AND ASTRONOMY CLEMSON UNIVERSITY CLEMSON, SOUTH CAROLINA ACADEMIC PRESS A Harcourt Science and Technology Company San Diego San Francisco New York Boston London Sydney Tokyo

2 Contents PREFACE LIST OF CONTRIBUTORS ix xv Chapter 1 Use of Atomic Diplacement Parameters in Thermoelectric Materials Research 1 Brian C. Sales, David G. Mandrus, and Bryan C. Chakoumakos I. INTRODUCTION 1 II. ELEMENTARY THEORY OF ATOMIC DEPLACEMENT PARAMETERS 4 III. INTERPRETING ADP DATA 6 1. Einstein Model 7 2. Debye Model 8 3. Static Disorder Einstein and Debye Temperatures from Room Temperature ADP Data IV. CLATHRATELIKE THERMOELECTRIC COMPOUNDS 14 V. ESTIMATION OF THE LATTICE THERMAL CONDUCTIVITY FROM ADP DATA Elementary Theory of Lattice Heat Conduction Lattice Heat Conduction: A More Realistic Model 21 VI. EXAMPLES FilledSkutterudites: LaFe i Sb l2 and YbFe i Sb l Tl 2 SnTe LaB Semiconducting Clathrates: Sr s Ga 16 Ge 30 and Ba s Ga l6 Ge CeRuGe i 32 VII. SUMMARY 33 REFERENCES 34 Chapter 2 Electronic and Thermoelectric Properties of Half- Heusler Alloys 37 S. Joseph Poon I. INTRODUCTION The Crystal Structure Electronic Crystals Thermoelectric Properties 40 V

3 vi CONTENTS 4. Other New Intermetallic Phases Goals of This Chapter 41 II. EXPERIMENTAL PROCEDURES 42 III. UNDOPED COMPOUNDS WITH VALENCE ELECTRON COUNT NEAR Semiconducting and Semimetallic Properties Bandgap States in the VEC = 18 Alloys Carrier Mohilities Magnetic Properties and Band-Structure Results Thermoelectnc Properties 57 IV. DOPED ALLOYS Transport Properties Bandgap Features Inferredfrom Doping Studies Impurity Band Transport Properties Thermoelectnc Properties 66 V. SUMMARY 71 REFERENCES 72 Chapter 3 Overview of the Thermoelectnc Properties of Quasicrystalline Materials and Their Potential for Thermoelectnc Applications 77 Terry M. Tritt, A. L. Pope, and J. W. Kolis I. QUASICRYSTALS: BACKGROUND AND INTRODUCTION 77 II. QUASICRYSTALS: STRUCTURAL AND MECHANICAL PROPERTIES 80 III. SYNTHETIC METHODS FOR THE GROWTH OF QUASICRYSTALS Scope and Introduction General Considerations Analysis Synthesis of Stahle Phases Grain Growth 87 IV. INTRODUCTION TO THERMOELECTRIC MATERIALS 90 V. QUASICRYSTALS AS THERMOELECTRICS? 91 VI. THERMOELECTRIC PROPERTIES OF QUASICRYSTALS Various Quasicrystalline Families Electrical Resistivity Thermopower Thermal Conductivity Thermal and Electrical Transport in AlPdMn for Thermoelectrics 101 VII. FUTURE DIRECTIONS AND APPROACH 109 VIII. SUMMARY 110 REFERENCES 111 Chapter 4 Military Applications of Enhanced Thermoelectrics Alexander C. Ehrlich and Stuart A. Wolf I. INTRODUCTION 117 II. THERMAL MANAGEMENT Biological Electronic Other 121

4 CONTENTS vii III. POWER GENERATION 122 IV. CONCLUSION 124 Chapter 5 Theoretical and Computational Approaches for Identifying and Optimizing Novel Thermoelectric Materials 125 David J. Singh I. INTRODUCTION 125 II. SOME FUNDAMENTAL CONSIDERATIONS The Thermoelectric Figure ofmerit Lattice Thermal Conductivity 127 III. FIRST PRINCIPLES METHODOLOGY Density Functional Calculations Kinetic Transport Theory 131 IV. SKUTTERUDITES Binary Skutterudites Ce-Filled Skutterudites La-Filled Skutterudites Lattice Dynamics and Effects of Filling Prospects 162 V. CHEVREL PHASES 162 VI. ß-Zn 4 Sb VII. HALF-HEUSLER COMPOUNDS 170 VIII. CONCLUDING REMARKS 172 REFERENCES 173 Chapter 6 Thermoelectric Properties of the Transition Metal Pentatellurides: Potential Low-Temperature Thermoelectric Materials 179 Terry M. Tritt and R. T. Littleton, IV I. PENTATELLURIDES: BACKGROUND AND INTRODUCTION Overview oflnterest in Low-Dimensional Conductors in the 1980s Anomalous Electrica! Transport in HfTe 5 and ZrTe Synthesis and Structure Effects of Stress and Pressure Magnetotransport and Hall Effect 186 II. INTRODUCTION TO THERMOELECTRIC MATERIALS General Description Low-Temperature Refrigeration Applications 189 III. PENTATELLURIDES AS POSSIBLE LOW-TEMPERATURE THERMOELECTRIC MATERIALS. 190 IV. RECENT DEVELOPMENTS IN PROPERTIES OF PENTATELLURIDES Doping on the Transition Metal Site (M x A y Te 5, M = Hf, Zr, A = Zr, Ti) Doping on the Chalcogen Site (MTe 5 x Ch x, M = Hf, Zr, A = Se, Sb) Magnetotransport: Overview of Recent Results Thermal Conductivity of Pentatellurides Summary of Thermoelectric Properties 201 V. DISCUSSION AND CONCLUSIONS 201

5 viii CONTENTS VI. SUMMARY 203 REFERENCES 204 Chapter 7 Thermomagnetic Effects and Measurements 207 Franz Freibert, Timothy W. Darling, Albert Migliori, and Stuart A. Trugman I. INTRODUCTION 207 II. THERMOMAGNETIC EFFECTS Adiabatic and Isothermal Conditions Definition of Transport Coefficients Electronic Refrigeration Ideal Behavior 217 III. PHENOMENOLOGICAL ANALYSIS Equations of Performance Microscopic Electronic Properties Umkehr Effect 222 IV. MATERIALS SURVEY Basic Material Requirements Compensated Materials Bismuth and Bismuth-Antimony Alloys Doped Materials 229 V. EXPERIMENTAL MEASUREMENT TECHNIQUES Experimental Fundamentals Isothermal Measurements Adiabatic Measurements 238 VI. SUMMARY 241 REFERENCES 241 Chapter 8 Heat and Electricity Transport through Interfaces M. Bartkowiak and G. D. Mahan I. INTRODUCTION 245 II. BOUNDARY IMPEDANCES 247 III. WIEDEMANN-FRANZ LAW AT BOUNDARIES 251 IV. ENERGY BALANCE EQUATIONS FOR ELECTRONS AND PHONONS OUT OF EQUILIBRIUM 253 V. THERMAL INSTABILITY 256 VI. EFFECTIVE THERMOELECTRIC PROPERTIES Effective Thermal Conductivity Effective Seebeck Coefficient Effective Figure of Merit 262 VII. SUPERLATTICES 266 VIII. SUMMARY 269 REFERENCES 270 INDEX 273 CONTENTS OF VOLUMES IN THIS SERES 279