||Energy shortage has become one the most critical issues, and therefore the development of thermoelectric (TE) materials, which allows the direct conversion between waste heat and electricity, has attracted growing attentions. Among all types of thermoelectric materials, the hexagonal rhombohedric β-Zn4Sb3, which is constituted by cost-effective, earth-abundant and non-toxic elements, features with intrinsically low lattice thermal conductivity, owing to the disordering of Zn-interstitials, and has been viewed as a promising mid-temperature TE material. Phase diagram provides fundamental yet essential information, and therefore the 350˚C isothermal section and liquidus projection of ternary Cu-Sb-Zn system are constructed in this study. Various ternary alloys are thermally-equilibrated at 350oC for 45 days to clarify the phase relations, with an emphasis upon the homogeneity rang of Zn4Sb3 phase at elevated temperature. As for the liquidus projection, the ternary alloys are either air-cooled or water-quenched, to investigate the solidification behaviors of ternary Cu-Sb-Zn system.|
Apart from the phase diagram determinations, the selective p-type Zn4-xSb3 alloys with varying Zn/Sb ratios were grown by Bridgman method, and their thermoelectric properties were measured. Alloy Zn4.06Sb2.94 featured with nano-sized Zn inclusion reaches a peak value of zT~0.9 at 657K, showing 112% enhancement compared with that of the stoichiometric Zn4Sb3 (zT~0.8). In addition, the Cu-doped Zn4-xSb3 alloys are prepared, and the maximum zT of 0.8 is obtained in (Zn4Sb3)0.93Cu0.07 at 659 K, presumably attributed to the existence of secondary Cu5Zn8 that improves the electrical conductivity.