Zr vacancy interfaces: an effective strategy for collaborative optimization of ZrNiSn-based thermoelectric performance

Abstract

Grain boundaries play a key role in carrier/phonon transport in thermoelectric materials. Precise regulation of the chemical composition of the grain boundaries by conventional methods is a huge challenge. Here, the method of atomic layer deposition (ALD) is used to precisely control the Zr vacancy ratio and the ZrO₂ nanoparticle content in the grain boundary of the ZrNiSn_0.99Sb_0.01 (ZNSS) thermoelectric material. First-principles calculations show that the Zr vacancy interface not only introduces the Zr/Sn anisite defect, but also optimizes the interface barrier, which strongly decouples the Seebeck coefficient and electrical conductivity to achieve a substantial improvement in electrical performance. Benefiting from the optimization of the Zr vacancy interface for electrical transport, the highest power factor of 56.1 μW cm⁻¹ K⁻² is achieved at 873 K. At the same time, the multi-scale microscopic effect induced by the Zr vacancy interface and ZrO₂ nanoparticles can greatly suppress the lattice thermal conductivity. The maximum zT value of 1.13 is achieved, which is 35% higher than that of pure ZNSS. Our work puts forward a new idea of interface engineering for enhancing the thermoelectric performance of ZrNiSn-based materials based on ALD technology, which may be of great significance for the design of high performance thermoelectric materials.