ABSTRACT
Cubic Lattice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 6.6 Electronic Band Structures of Perovskites. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
6.6.1 Cubic Perovskites with Transition Metal Ions: Semiconductors and Metals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
6.6.2 Cubic Perovskites with Main Group Ions . . . . . . . . . . . . . . . . . . . . . . . 171 6.6.3 Distorted Perovskites: NaTaO3, CaSnO3, and CdSnO3 . . . . . . . . 173
“DK3029_C006” — #2
6.7 Electronic Band Structures of Binary Oxides Used as Transparent Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 6.7.1 The Electronic Structure of SnO2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 6.7.2 The Electronic Structure of ZnO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 6.7.3 The Electronic Structure of CdO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 6.7.4 The Link between Conduction Band Width and Oxygen
Coordination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 6.7.5 Generality of the Anion Coordination — Bandwidth
Connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 6.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Metal oxides play an important role in many fields, including inorganic and materials chemistry, condensed matter physics, geology, materials science, and mechanical and electrical engineering. The importance of metal oxides lies in their variety, their chemical stability, and their fascinating chemical and physical properties. Metal oxides display properties ranging from piezoelectricity to superconductivity, from negative thermal expansion to ionic conductivity. Metal oxides are used as gemstones, transparent conductors, gas sensors, and catalysts to name but a few applications. They are used in computers, Li-ion batteries, fluorescent lights, cellular phones, and fuel cells. An important focus of scientists who synthesize and utilize metal oxides is to understand the origin of their properties and to learn how to manipulate these properties through modification of the composition, the crystal structure, and/or the defects. This requires an understanding of the electronic band structure, which, on the one hand, is the link between composition and crystal structure and on the other hand with chemical and physical properties. The optical and electrical transport properties can be understood directly from the electronic structure. The chemical reactivity and catalytic properties depend upon the energy levels and symmetry of electronic states near the Fermi level. Even the dielectric and mechanical properties can be traced to the chemical bonding that is the origin of the electronic structure.
