ABSTRACT
Phase diagrams are important in the study of thermoelectric materials in two essential aspects. First, thermoelectric performance is largely dependent on the carrier concentration, which is determined by the dopant solubility. To obtain a dopant solubility that properly optimizes carrier concentration, knowledge of the equilibrium phase diagram is required. Second, phase separation on different length scales [1-3] has been shown to have great ability in reducing the lattice thermal conductivity, thus enhancing thermoelectric performance. A variety of microstructures, as well as shape, size, and density of
CONTENTS
10.1 Introduction ........................................................................................................................ 351 10.2 Methodology ......................................................................................................................354 10.3 Stable Compositions and Vegard’s Law .......................................................................... 356
10.3.1 Solubility Debate regarding Yb ........................................................................... 356 10.3.2 Skutterudite Lattice Expansion due to Yb Filling ............................................. 358 10.3.3 Stable Compositions in the Ternary Phase Diagram System .......................... 359 10.3.4 Vegard’s Law in the Ternary Phase Diagram System.......................................360
10.4 Solubility Design Strategies .............................................................................................364 10.4.1 Solubility Barrier of Ce in Ce-CoSb3 ...................................................................364 10.4.2 Optimum Doping of Ce-CoSb3 Skutterudites ...................................................365 10.4.3 Ultrahigh Filling Fraction Limit of Ce in Ce-CoSb3 Skutterudites .................365 10.4.4 Thermoelectric Properties of Optimized Ce-CoSb3 Skutterudites ................. 370
10.5 Substitutional and Compound Defects .......................................................................... 372 10.5.1 Solubility Debate regarding In and Ga ............................................................... 372 10.5.2 Density Functional Theory Calculations of In-and Ga-Doped CoSb3
