Chiral Twist Interface Modulation Enhances Thermoelectric Properties of Tellurium Crystal.

Abstract

Manipulating the grain boundary and chiral structure of enantiomorphic inorganic thermoelectric materials facilitates a new degree of freedom for enhancing thermoelectric energy conversion. Chiral twist mechanisms evolve by the screw dislocation phenomenon in the nanostructures; however, contributions of such chiral transport have been neglected for bulk crystals. Tellurium (Te) has a chiral trigonal crystal structure, high band degeneracy, and lattice anharmonicity for high thermoelectric performance. Here, Sb-doped Te crystals are grown to minimize the severe grain boundary effects on carrier transport and investigate the interface of chiral Te matrix and embedded achiral Sb2Te3 precipitates, which induce unusual lattice twists. The low grain boundary scattering and conformational grain restructuring provide electrical-favorable semicoherent interfaces. This maintains high electrical conductivity leading to a twofold increase in power factor compared to polycrystal samples. The embedded Sb2Te3 precipitates concurrently enable moderate phonon scattering leading to a remarkable decrease in lattice thermal conductivity and a high dimensionless figure of merit(zT)of 1.1 at 623 K. The crystal growth and chiral atomic reorientation unravel the emerging benefits of interface engineering as a crucial contributor to effectively enhancing carrier transport and minimizing phonon propagation in thermoelectric materials.