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The high-temperature electrical conductivity and thermopower of several compounds in the In2O3(ZnO)k system (k=3, 5, 7, and 9) were measured, and the band structures of the k=1, 2, and 3 structures were predicted based on first-principles calculations. These phases exhibit highly dispersed conduction bands consistent with transparent conducting oxide behavior. Jonker plots (Seebeck coefficient versus natural logarithm of conductivity) were used to obtain the product of the density of states and mobility for these phases, which were related to the maximum achievable power factor (thermopower squared times conductivity) for each phase by Ioffe analysis (maximum power factor versus Jonker plot intercept). With the exception of the k=9 phase, all other phases were found to have maximum predicted power factors comparable to other thermoelectric oxides if suitably doped.

Jonker plots (Seebeck coefficient versus logarithm of conductivity) have been utilized to obtain the product of the density of states (DOS) and mobility (l) in oxide semiconductors, from which the maximum electrical conductivity can be estimated for degenerate transparent conducting oxide (TCO) applications. In addition, the DOS-l product can be utilized to predict the maximum achievable ''power factor'' (PF, Seebeck coefficient squared times conductivity) for oxide semiconductors. The PF is an important parameter governing the figure of merit for thermoelectric oxide (TEO) applications. The procedure employs an analysis developed by Ioffe, and provides an important screening tool for oxide (and other) thermoelectric materials, based upon data from polycrystalline ceramic specimens. Several oxides, including known transparent conductors, are considered as TCO and TEO case studies in the present work.