In this study, β -Zn 4 Sb 3 was prepared using the Zn-NaCl mixed-flux method based on the stoichiometric ratio of Zn/Sb/NaCl = (4− x ):3:(7+ x ) ( x = 0, 0.1, 0.2, 0.3). X-ray diffraction results showed that all samples were hexagonal rhombic crystal structures with the space group \(R\overline{3}c\) . A second phase of ZnSb was detected in the samples with x = 0.2 and x = 0.3. In addition, the crystal-cell volume and lattice parameter of all samples increased for the larger ion radius of Na + than Zn 2+ . The transmission electron microscopy image and corresponding area electron diffraction pattern demonstrated that the prepared samples had a complete crystal structure. All samples had hole conduction and exhibited p-type conduction behavior. The carrier concentration of the material increased with increased Na content and decreased Zn, ranging from 8.89 × 10 19 cm −3 to 17.82 × 10 19 cm −3 . Moreover, the thermal conductivity ( κ ) of x = 0–0.2 samples decreased with increased Na content; however, the sample with x = 0.3 had a higher κ owing to the appearance of a ZnSb phase. Thermogravimetric differential thermal analysis showed that no weight loss occurred below the melting point. Eventually, the sample with the nominal composition of β- Zn 3.8 Sb 3 NaCl 7.2 achieved a ZT value of 1.43 at 690 K.
Shuping Deng,Decong Li,Liping Zheng,Yu Tang,Zhong Chen,Luqi Sun,Wenting Liu,Lanxian Shen,Shukang Deng
In this work, the effect of Cd and Sn atoms partly substitution for Zn on among crystal growth, thermal stability, mechanical, and electrical transport property in β-Zn 4 Sb 3 is reported. In a series of samples prepared from the atomic ratios of Zn:Sb:Cd:Sn = 4.4:3: x :3 ( x = 0.2, 0.4, 0.6, and 0.8). Carrier concentration of all samples varies from 4.52 × 10 19 to 6.42 × 10 19 cm −3 as carrier mobility changes from 58.27 to 67.93 cm 2 V −1 s −1 at room temperature. As a result, electrical transport properties of the samples are optimized by Cd Sn co-doped. The experimental density of all the samples varies from 6.26 × 10 3 to 6.34 × 10 3 kg m −3 consistent with the theoretical value. The weight loss and melting point of the sample are determined to discuss thermal stability in the heating process in air, indicating that the single crystals β-Zn 4 Sb 3 possess an excellent thermal stability and it is practical importance in the TE application at high temperature. Consequently, the maximal power factor of 1.70 × 10 −3 W m −1 K −2 is achieved at 540 K for the sample with initial Cd content x = 0.2, which is enhanced by 40% compared with the single-doping system in β-Zn 4 Sb 3 .
Jie Zheng,Yu Tang,Yujie Xiang,Yonggui Tao,Kaiyuan Shen,Lanxian Shen,Wen Ge,Peizhi Yang,Shukang Deng
β-Zn4Sb3 is a promising thermoelectric (TE) material, as it contains low-cost and environment-friendly elements. However, its application has long been limited due to the lower figure of merit (ZT), poor mechanical properties, and inferior thermodynamic stability. In this research, we successfully synthesized Na/Ga codoped β-Zn4Sb3 with high thermoelectric performance and stability. The power factor (PF) value of the Ga-doped sample is significantly improved by optimizing carrier concentration, the maximum value of 2.28 × 10–3 W m–1 K–2 is obtained at 690 K, and the maximum ZT reaches 1.73 at 690 K for the Zn4.1Sb3(NaCl)7Ga0.12 sample. Moreover, the TG-DSC and oxidation resistance tests show that Na and Ga codoped β-Zn4Sb3 possess good stability. This work provides an attractive method for improving the thermoelectric properties and stability of β-Zn4Sb3 through diatomic doping.
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