Stacking Fault Complexions in AgSbTe ₂ Thermoelectrics With Enhanced Electrical Conductivity

Designing nanostructures in thermoelectric materials is a very effective way to enhance the power conversion efficiency. Nanostructures can lead to a desirable reduction in the lattice thermal conductivity, but most of them also result in unwanted decrease in the electrical conductivity. In this work, stacking faults in AgSbTe 2 are found to simultaneously act as phonon scatterers and improve the electrical conductivity. Using electron channeling contrast imaging, a high density of stacking faults is identified at low‐angle grain boundaries in AgSbTe 2 . The atomic arrangement of the stacking faults is revealed by aberration‐corrected scanning transmission electron microscopy. Unlike conventional stacking faults, an additional translation vector of 1/8<111> causes a larger separation at the stacking faults. Segregation of Sb and Te and depletion in Ag at the stacking faults are quantified by atom probe tomography. The larger separation and chemical segregation increase the phonon scattering rate compared to undecorated stacking faults. Using electrical measurements at the micrometer scale, the chemically decorated stacking faults are found to consistently enhance the local electrical conductivity by 20% in the normal direction. Engineering crystal defect complexions to simultaneously promote electron conduction and phonon scattering adds a new dimension to thermoelectric materials design beyond their efficiency limit.