Small-polaron electronic transport in boron carbides

Electrical transport measurements indicate that the charge carriers form small polarons. Here, conduction is due to a large (nearly degenerate) density of small polarons which move via hopping. A unique and significant feature of the Seebeck coefficient is that here, in a disordered small-polaron material, vibrational energy is transported with the carrier as it hops. This gives rise to an augmentation of the Seebeck coefficient which rises with temperature. In a degenerate small-polaron material this term produces a figure-of-merit for a high-temperature thermoelectric generator which is greater than the maximum estimated previously by Heikes