A thermoelectric half-Heusler material comprising niobium (Nb), iron (Fe) and antimony (Sb) wherein the material comprises grains having a mean grain size less than one micron. A method of making a nanocomposite half-Heusler thermoelectric material includes melting constituent elements of the thermoelectric material to form an alloy of the thermoelectric material, comminuting (e.g., ball milling) the alloy of the thermoelectric material into nanometer scale mean size particles, and consolidating the nanometer size particles to form the half-Heusler thermoelectric material comprising at least niobium (Nb), iron (Fe) and antimony (Sb) and having grains with a mean grain size less than one micron.
RESEARCH OR DEVELOPMENT
 This invention was made with government support under grant number DE-EE0004840 from the U.S. Department of Energy. The government may have certain rights in the invention.