Thermoelectric power of single-crystal graphite at low temperatures

Abstract

Abstract The thermoelectric power (TEP) along the basal plane of a synthetic single-crystal graphite has been measured in the temperature range from 300°K down to 7°K. The TEP versus temperature diagram exhibits two anomalies; a sharp negative dip located at 35°K on the abscissa and a pronounced positive peak centred at 120°K. The latter is followed further by the change of sign of TEP from plus to minus at 235°K. Through a consideration of the momentum exchange between phonons and electrons, the negative dip has been considered as originating from the phonon drag effect, while the positive peak and the change of sign are attributed to the variation of the so-called mobility ratio (electron versus hole) with temperature. On the basis of appropriate assumptions, a clear separation between the electron diffusion and phonon drag components has successfully been made of the observed TEP data.