ABSTRACT
As is apparent from Equation 16.1, the material’s transport properties are the key to achieving a high TE œgure of merit. šus, searching for materials that possess a high ZT value along with a relatively temperature-independent compatibility factor is the goal of much of the research in this œeld [3]. Referring to Equation 16.1, the high ZT material should be what has come to be known as a “phononglass electron-crystal” (PGEC) [5] that is, a material that simultaneously possesses a high Seebeck coef-œcient (o¿en called the thermopower), high electrical conductivity (weak electron scattering), and a low lattice thermal conductivity (strong phonon scattering). It is di²cult to satisfy these criteria in a simple crystalline bulk material since all three quantities (σ, α, and κ) that govern ZT are interrelated, and a modiœcation of any of these quantities o¿en adversely a¤ects the others, so classes of materials that are good TE materials are relatively rare.
