Homologous rare earth boron cluster compounds: a possible n-type counterpart to boron carbide

Abstract

There is a large incentive to discover/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 "unfriendly" (e.g. acidic, corrosive) conditions. We have discovered that a homologous series of newly found layered rare earth B12 icosahedra compounds, exhibit both p-type and n-type behavior depending on the number of boron icosahedra layers. This is the first discovery of a B12 icosahedra compound exhibiting n-type behavior without extreme doping and is exciting because it may be a possible counterpart to the p-type boron carbide which is well known to be an attractive high temperature thermoelectric material. The first samples were prepared by conventional hot press and cold press methods and were not so dense. Utilizing spark plasma synthesis (SPS) we have been able to prepare samples with significantly improved properties