Role of SnTe Addition in Enhancing the Figure of Merit of AgCuTe-Based Materials

Recently, AgCuTe has garnered growing interest as a promising superionic conductor. Herein, we investigated the thermoelectric property changes induced by introducing SnTe into AgCuTe. The introduction of SnTe enabled a nearly 20% enhancement in the Seebeck coefficient. Combining with the relatively high electrical conductivity, a power factor of 9.3 μW cm–1 K–2 was achieved at 723 K. Particularly, by introducing SnTe into AgCuTe, multiple-scale defects including atomic-scale lattice disorder, nanoprecipitates, and micrometer-scale grain boundaries were constructed as an effective hierarchical phonon scattering mechanism. Owing to the scattering of full-wavelength phonons, we yielded a low lattice thermal conductivity of 0.2 W m–1 K–1, which approached the amorphous limits. Consequently, a maximum zT up to 1.1 was obtained at 723 K for AgCuTe–3 wt % SnTe, which was nearly 40% higher than that of pristine AgCuTe.