Ln₃Au₃Sb₄: Thermoelectrics with low thermal conductivity

The thermoelectric properties of intermetallic compounds with the Y₃Au₃Sb₄ structure type, of formula Ln₃Au₃Sb₄ for Ln = Gd, Nd, Ho, and Sm, are reported. The highest Seebeck coefficients are on the order of 100-200 μV/K, indicating that the dominant carriers are holes, and increase with increasing temperature. Variation of the Au:Sb ratio significantly affects the resistivities and Seebeck coefficients. Materials with mixtures of lanthanides on the large atom site show improved Seebeck coefficients without degradation of the electrical resistivity. The thermal conductivities are very low, even for the stoichiometric materials, and decrease in materials with mixed lanthanides. Band-structure calculations show a complex multivalley character for both valence and conduction bands.