Exploration and Optimization of Tellurium‐Based Thermoelectrics

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Figure 17.7 Seebeck coefficient (circle) and electrical conductivity (diamond) of Ba 2Cu 6.6Te 6. The metallic character, even though persistent in only one direction, stands against using this telluride in the thermoelectric energy conversion, unless one succeeds in preparing a device wherein the metallic direction is exclusively perpendicular to the carrier transport direction, or one produces a more significant distortion into the Te chain leading to a band gap formation. While the latter occurs readily in form of a Peierls distortion [319] in many one‐dimensional materials, such as in the Te chain of RbUSb0.33Te6, [320] this case already displays a distorted chain making a further introduction of a gap‐ opening distortion highly unlikely. 17.4. Conclusion The new Ba2Cu7‐xTe6 telluride was discovered and characterized. Its crystal structure, determined by an X‐ray structure determination, is of a new structure type with infinite zigzag chains of Cu8‐clusters and infinite distorted pseudo‐linear chains of Te atoms. The band structure calculations show two steep bands arising from antibonding Te–Te interactions crossing the Fermi level parallel to a*, pointing to one‐dimensional metallic properties. The electrical conductivity and Seebeck measurements yielded values around 180 –1 cm –1 and 50 V∙K ‐1 , respectively, at room temperature. The power factor was found to be 1.45 W∙cm ‐1 K ‐2 at 750 K, which is low compared to advanced thermoelectrics. This material could on the other hand become a useful thermoelectric, if large single crystals of defined orientation could be grown, but thus far our attempts to do so failed (or a Peierls distortion be introduced). 178
Section VI – Supplementary Information EndNote Bibliography, Tabulated Appendices 179
Page 1 and 2:
Exploration and Optimization of Tel
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Abstract Thermoelectric materials a
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Acknowledgements To begin, I would
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Table of Contents List of Figures..
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9.3.1. Heating, XRD, and Structural
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List of Figures Figure 1.1 (a) Pelt
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Figure 9.2 Selected DOS calculation
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List of Equations Equation 1.1 Dime
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Table B.1 Atomic positions, isotrop
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Section I: Fundamentals Background
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Opposing the Peltier Effect is the
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Hence it follows that a good thermo
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a b ∗ Equation 1.4 (a) Ele
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Historically, thermoelectric materi
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1.3.2. Advantages and Disadvantages
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common stoichiometry studied with c
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Figure 1.8 (a) Ge Quantum Dots [74]
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Chapter 2. Background of the Solid
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2.2. Defects, Non‐Stoichiometry a
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electric field draws electrons towa
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∑ known as a Bloch function, w
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orbital Hamilton population [96] i
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2.5.1. Doping and Substitution: Tun
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The major problem with exclusively
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Chapter 3. Synthesis Techniques All
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Since reactions are driven by both
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Table 3.1 Commonly used fluxes. [12
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The procedure is carried‐out on a
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Chapter 4. X‐Ray Diffraction Anal
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The closely related electron densit
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The majority of samples emerge from
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int ∑ mean ∑ | | Equat
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4.3.1. Rietveld Method In 1967, Hug
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Chapter 5. Physical Property Measur
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The electrical conductivity, σ, is
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a p b 0.1388 53 c Equati
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measurement implies that there was
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Figure 5.6 Home‐made electrical c
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The SEM is constructed from an elec
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The EDX measurement system utilized
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2 4 ext Equation 6.2 Ma
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Section III - Layered Bi2Te3 Compou
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aforementioned studies address the
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Pb‐based compound (~‐60 V∙K
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also differ in 2 there, while the r
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Table 7.2 LeBail data for phase‐p
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The physical properties, as mention
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Upon examination of the power facto
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Sn2Bi2Te5 was eventually found pure
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From the understanding of this comp
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Table 8.1 Rietveld refinements on S
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Although there is evidence here of
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Figure 8.3 DOS calculation comparis
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In order to better determine if the
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8.3.3. Physical Property Measuremen
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Figure 8.7 Thermal conductivity (le
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the thermal conductivity slope that
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8.4. Conclusions and Future Work A
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in Chapter 3 (except Arc Melting) w
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Table 9.2 LeBail refinements on var
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9.2.3.1. Doping Trials: [Tr]xSn1‐
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9.2.3.2. Substitution Trials: [Tr]x
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One can observe a variety of grain
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9.2.5. Conclusions Drawn from SnBi4
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SnBi4Te7, but suggest similar albei
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9.4. Project Summary and Future Wor
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Chapter 10. Introduction to Tl5Te3
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Figure 10.2 DOS calculations for Tl
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Thallium‐based chalcogenides clea
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: 36.3 (expected: 48.8 : 13.8 : 37.
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sintering of these pellets. A cold
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Figure 11.2 Thermoelectric properti
Page 145 and 146: at 319 K, increasing smoothly to 0.
Page 147 and 148: purity upon the first heating with
Page 149 and 150: Tl/Sn/Bi present in the 4c Wyckoff
Page 151 and 152: V∙K ‐1 at 592 K. As the bismuth
Page 153 and 154: Electrical conductivity values are
Page 155 and 156: Chapter 13. Modifications of Tl9SbT
Page 157 and 158: Table 13.1 Rietveld refinements for
Page 159 and 160: make an observable trend despite th
Page 161 and 162: The electrical conductivity values
Page 163 and 164: Section V - Ba Late‐Transition‐
Page 165 and 166: Obviously, compounds possessing the
Page 167 and 168: Table 14.1 Known Ba‐Cg‐Q compou
Page 169 and 170: All samples were analyzed by means
Page 171 and 172: crystal structure study of the Se
Page 173 and 174: As emphasized in Figure 15.2 (b), t
Page 175 and 176: The Cu-Cu COHP curve, cumulated ove
Page 177 and 178: Chapter 16. Ba3Cu17‐x(S,Te)11 and
Page 179 and 180: the selenide‐telluride before, th
Page 181 and 182: surrounded by three Q1 atoms. Besid
Page 183 and 184: Figure 16.3 The three‐dimensional
Page 185 and 186: Figure 16.5 Seebeck coefficient (le
Page 187 and 188: Chapter 17. Ba2Cu7‐xTe6 17.1. Int
Page 189 and 190: Table 17.1 Crystallographic Data fo
Page 191 and 192: Table 17.2 Atomic coordinates, Ueq
Page 193 and 194: 17.3.2. Electronic Structure Calcul
Page 195: Figure 17.6 Crystal orbital Hamilto
Page 199 and 200: [33] Rowe, D. M.; Kuznetsov, V. L.;
Page 201 and 202: [90] Albright, T. A.; Burdett, J. K
Page 203 and 204: [156] Cottenier, S., Density Functi
Page 205 and 206: [219] Toure, A. A.; Kra, G.; Eholie
Page 207 and 208: [294] Kanno, R.; Ohno, K.; Kawamoto
Page 209 and 210: Table A.3 Atomic positions and Ueq
Page 211 and 212: Table B.2 Selected interatomic dist
Page 213 and 214: Table B.5 Atomic coordinates and Ue
Page 215 and 216: Table B.7 Selected interatomic dist
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Exploration and Optimization of Tellurium‐Based Thermoelectrics

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