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°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.

Copper-antimony-sulfide compounds have desirable earth-abundant compositions for application in renewable energy technologies, such as solar energy and waste heat recycling. These compounds can be synthesized by bottom-up, solution-phase techniques that...

The recent discovery that specific materials can simultaneously exhibit n-type conduction and p-type conduction along different directions of the single crystal has the potential to impact a broad range of electronic and energy-harvesting technologies. Here, we establish the chemical design principles for creating materials with this behavior. First, we define the singlecarrier and multicarrier mechanisms for axis-dependent conduction polarity and their identifying band structure fingerprints. We show using first-principles predictions that the AMX (A = Ca, Sr, Ba; M = Cu, Ag, Au; X = P, As, Sb) compounds consisting of MX honeycomb layers separated by A cations can exhibit p-type conduction in-plane and n-type conduction cross-plane via either mechanism depending on the doping level. We build up the band structure of BaCuAs using a molecular orbital approach to illustrate the structural origins of the two different mechanisms for axis-dependent conduction polarity. In total, this work shows this phenomenon can be quite prevalent in layered materials and reveals how to identify prospective materials.