Fig. 4: Exceptional thermoelectric performance for low-to-medium grade waste heat harvesting.

Temperature-dependent a electrical conductivity (σ), b Seebeck coefficient (S), and c Hall carrier concentration (n_H), and mobility (μ_H) of Yb_0.5Mg_1.3Zn_1.2Sb₂ compounds. d HAADF-STEM images showing a grain boundary in Yb_0.5Mg_1.3Zn_1.2Sb₂ with corresponding EDS mapping showing Yb deficiency. e Atomic resolution HAADF-STEM image of Yb_0.5Mg_1.3Zn_1.2Sb₂ along the [11\(\bar{2}\)0] orientation and the corresponding fast Fourier transform pattern. f Integrated EDS intensity profile along the y-axis with quantification after multi-variate analysis⁴⁸. g Temperature-dependent thermal conductivity (κ)^17,18,19. h1 Temperature-dependent zT and h2 average zT (zT_ave) in comparion with literature^17,18,19. i Simulated maximum conversion efficiency (η_max) of a Zintl-based unicouple depending on the geometrical configuration, where the y-axis shows the ratio between height of Zintls and Bi₂Te₃-based (BT) compounds and the x-axis shows the ratio of cross section between p- and n-type legs. j Measured and predicted inner resistance (R_in) and open-circuit voltage (V_oc) as a function of temperature difference. k Conversion efficiency (η_out) of the Zintl-based module under different temperature differences.