The Phonon—Glass Electron-Crystal Approach to Thermoelectric Materials Research

Based on the theory outlined in Part I, one can list the requirements for materials suitable for thermoelectric cooling and power generation applications at and above ambient temperatures. For semiconductors these are the basic criteria: 1. High crystal symmetry with the electronic bands near the Fermi level and many valleys. 2. Heavy element compounds with small electronegativity differences between constituent elements. 3. Energy gap of about 10 k B T, where T is the temperature of operation and k B is Boltzmann’s constant.