Thermoelectric Performance of Tetrahedrite Synthesized by a Modified Polyol Process

Tetrahedrite, a promising thermoelectric material composed of earth-abundant elements, has been fabricated utilizing the rapid and low energy modified polyol process. Synthesis has been demonstrated for undoped and zinc-doped tetrahedrite samples on the gram scale requiring only 1 h at 220 degrees C. This method is capable of incorporating dopants and producing particles in the 50-200 nm size regime. For determination of bulk thermoelectric properties, powders produced by this solution-phase method were densified into pellets by spark plasma sintering. Thermopower, electrical resistivity, and thermal conductivity were obtained for temperatures ranging from 323 to 723 K. Maximum ZT values at 723 K were found to be 0.66 and 1.09 for the undoped and zinc-doped tetrahedrite samples, respectively. These values are comparable to or greater than those obtained using time and energy intensive conventional solid-state methods. Consolidated pellets fabricated using nanomaterial produced by this solution-phase method were found to have decreased thermal conductivity, increased electrical resistivity, and increased thermopower. Exceptionally low total thermal conductivity values were found (below 0.7 W m(-1) K-1 for undoped tetrahedrite and 0.5 W m(-1) K-1 for zinc-doped tetrahedrite), with both having lattice thermal conductivities below 0.4 W m(-1) K-1. This study explores how nanostructuring and doping of tetrahedrite via a solution-phase polyol process impacts thermoelectric performance.