Figure 4. Theoretically and experimentally demonstrated independent control of κ_zz and ρ_xx, and its enhancement of performance by introducing Ni porosity.

(a) Theoretical porosity effects on (a) κ_zz, ρ_xx and (b) Z_xzT of the Bi_0.5Sb_1.5Te₃ (red) and Ni (blue) layers. (c) Experimentally obtained resistance, generated voltage and output power of a 11-cm long tubular BST/Ni tilted multilayers. The dashed lines show the fitting curves based on theoretical calculation. Also shown are the TEM images of (b) the Bi_0.5Sb_1.5Te₃ layer and (c) the Ni layer of the BST/Ni multilayer fabricated by SPS at 500°C and 50 MPa under vacuum.