High thermoelectric performance via stacking-controlled symmetry breaking in layered AZnBi (A = Rb, Cs) Zintl materials

作者：A. Wani, Nirma Kumari, SuDong Park, Byungki Ryu · 发表于：Materials today physics · 年份：2025 · DOI：10.1016/j.mtphys.2026.102190 · 研究领域：Physics

High thermoelectric efficiency requires high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. However, strategies that suppress thermal conductivity often simultaneously degrade electrical conductivity, making effective electrical-thermal decoupling highly challenging. Here, we show that atomic-layer stacking order change in XZnBi (X = Rb, Cs) provides an efficient route to achieve such decoupling. Even though electronic transport coefficients and relaxation times remain largely insensitive to stacking order due to preserved Fermi-surface topology, the lattice thermal conductivity exhibits a strong stacking dependence, with AB stacking significantly suppressing it below 1 Wm$^{-1}$K$^{-1}$ at temperatures above 300 K. The stacking transition from AA to AB breaks structural symmetries. It increases the three-phonon phase space and available scattering channel, substantially suppressing phonon transport by about 50$\%$ in both materials. As a result, the AB-stacked phases yield high ZT values of 1.96 (1.69) in n-type CsZnBi (RbZnBi) at 900 K, which is about 40$\%$ (30$\%$) higher than AA stacking. These findings establish the XZnBi family as promising thermoelectric candidates and highlight stacking-order controlled phonon transport as a robust strategy for advancing thermoelectric material design.