Multiple-Filling-Induced Full-Spectrum Phonon Scattering and Band Convergence Leading to High-Performance n-Type Skutterudites.

Abstract

Filling guest atoms into the nanovoids of skutterudite compounds provides effective scattering for low-frequency phonons to reduce the lattice thermal conductivity. However, it is still difficult to simultaneously realize the full-spectrum phonon scattering and band engineering in the n-type skutterudites with higher thermoelectric performance. Here, we reveal that the combination of five types of element atoms in the lattice nanovoids brings about dense dislocations, abundant precipitated nanoparticles, and electronic band convergence in the n-type skutterudites. The Seebeck coefficient shows an increase with little deterioration on the carrier mobility due to the enhanced density of states near the Fermi level, leading to a 11% enhancement in the power factor at 823 K. The lattice thermal conductivity is significantly reduced to approach the glass limit due to the full-spectrum phonon scattering. As a result, a peak ZT value of about 1.7 at 823 K and an average ZT value of about 1.2 from 323 to 823 K are obtained. High thermoelectric performance combined with the structural optimization enables the simulated maximum energy conversion efficiency of the skutterudite module to reach up to 15.0%. Our finding opens a new dimension for doping atoms to achieve simultaneous optimization of electrical and thermal properties in polynary thermoelectric materials.