Doping effect in N-type rare earth boron carbonitrides

For possible waste heat applications, there is a large incentive to develop thermoelectric materials which can function at high temperature. Boron-rich cluster compounds are attractive as materials because of their stability under high temperature and ldquounfriendlyrdquo (e.g. acidic, corrosive) conditions. B₁₂ icosahedra compounds have been predominantly p-type. However, we have recently discovered n-type behavior in a homologous series of compounds. These compounds may be developed as counterparts to boron carbide which is well known to be an attractive high temperature thermoelectric material. The first samples were prepared by conventional hot press and due to their low density, had low power factors. Doping with small amounts of boride metals were shown to largely improve the power factor.