The High-Temperature Thermoelectric Properties of Polycrystalline Ba8Ga x Al y Si46?x?y Type-I Clathrates

Thermoelectric materials suitable for practical thermoelectric power generators should, ideally, be based on light elements, for example Si and Al, which are abundantly available. For this reason, silicon clathrate compounds in which both Ga and Al were substituted for Si were synthesized and their thermoelectric properties were investigated. The temperature-dependent electrical resistivity of the samples indicated their metallic nature, and their negative Seebeck coefficient suggested that charge transport in the samples was mainly through electron transport. The maximum absolute value of the Seebeck coefficient achieved was ?180 μV/K at 1040 K for Ba_7.90Ga_13.8Al_2.29Si_30.0. Thus, these materials have potential for use in practical thermoelectric power generators.