Reversible structural transition in spark plasma-sintered thermoelectric Zn4Sb3

• Published in: Journal of materials science 2016-02, Vol.51 (4), p.2041-2048
• Main Authors: Zhang, T, Zhou, K, Li, X. F, Chen, Z. Q, Su, X. L, Tang, X. F
• Format: Article
• Language: English
• Subjects: Acceleration; Annealing; antimony; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Crystallography and Scattering Methods; Direct current; Materials Science; Migration; Original Paper; phase transition; Phase transitions; Plasma sintering; Polymer Sciences; Positron annihilation; Solid Mechanics; Spark plasma sintering; spectroscopy; Thermoelectricity; Vacancies; X-ray diffraction; zinc; Zinc antimonides
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-015-9514-y

Thermoelectric Zn₄Sb₃ prepared by spark plasma sintering (SPS) method has been studied by X-ray diffraction (XRD) and positron annihilation spectroscopy. A reversible structural transformation between β-Zn₄Sb₃ and ZnSb was confirmed by XRD measurements. It was found that the as-milled powder is composed of the pure β-Zn₄Sb₃ phase, but after SPS, one side of the sintered sample changes to the ZnSb phase. Upon annealing at 300 °C, the ZnSb phase converts back to β-Zn₄Sb₃ phase. During these phase transition processes, Zn migration driven by direct current and Zn diffusion activated by annealing play important roles. Another interesting finding is that excess Zn can suppress the decomposition of β-Zn₄Sb₃ into ZnSb and Zn. Positron annihilation lifetime measurements confirm that the diffusion of Zn introduces large amounts of vacancy clusters in the ZnSb-side, and most of them are recovered when the ZnSb phase converts back to β-Zn₄Sb₃ due to the migration of Zn driven by annealing. The positron lifetime results further show the acceleration of Zn migration at about 150 °C. The existence of Zn vacancies is also observed in the β-Zn₄Sb₃ structure.