Thermoelectric performance of lanthanum telluride produced via mechanical alloying

Lanthanum telluride (La(3-x)Te(4)) has been synthesized via mechanical alloying and characterized for thermoelectric performance. This work confirms prior reports of lanthanum telluride as a good high-temperature thermoelectric material, with zT similar to 1.1 obtained at 1275 K. The thermoelectric performance is found to be better than that of SiGe, the current state-of-the-art high-temperature n-type thermoelectric material. Inherent self-doping of the system allows control over carrier concentration via sample stoichiometry. Prior high-temperature syntheses were prone to solute rejection in liquid and vapor phases, which resulted in inhomogeneous chemical composition and carrier concentration. The low-temperature synthesis provides homogeneous samples with acceptable control of the stoichiometry, and thus allows a thorough examination of the transition from a heavily doped degenerate semiconductor to a nondegenerate semiconductor. The effect of carrier concentration on the Hall mobility, Seebeck coefficient, thermal and electrical conductivity, lattice thermal conductivity, and thermoelectric compatibility are examined for 0.03 <= x <= 0.33.