Effect of Zn migration on the thermoelectric properties of Zn₄Sb₃ material

β-Zn₄Sb₃ is interesting as thermoelectric material at moderate temperature due to the extreme low thermal conductivity. Recent success in energy band engineering or nano-engineering led to a significant improvement in the thermoelectric properties of β-Zn₄Sb₃. In this work, we utilize the direct current to drive the migration of Zn by designing of sintering mould. Obvious Zn migration under the direct current applied in the plasma activated sintering (PAS) process is found in Zn₄Sb₃ compounds, and Zn exhibits significantly heterogeneous gradient composition distribution. At the top of sample, the single-phase Zn₄Sb₃ decomposes into ZnSb phase because of the loss of Zn, while Zn originated from lattice and interstitial sites in Zn₄Sb₃ is abundant in the bottom. The temperature-dependent transport measurements are also carried out at 323–673 K. Zn migration has a huge influence on the thermoelectric properties because of the sensitivity of Zn₄Sb₃. The maximum power factor can reach ~ 1.44 mW m⁻¹ K⁻² at 673 K due to the high Seebeck coefficient and low resistivity, which is one of the highest values in the reported results. The resulting peak ZT value of ~ 1.2 at 673 K is obtained. To control the Zn distribution by tuning the current is a feasible approach to improve the thermoelectric properties of Zn₄Sb₃ material.