Scholarlink

<p>Magnesium-based thermoelectric semiconductors have promising applications in automobiles and aircraft. Although a pulsed electric current sintering (PECS)-based one-step synthesis and sintering of impurity-doped Mg<sub>3</sub>Sb<sub>2</sub> with high thermoelectric performance has been reported, a better understanding of the synthesis process, resulting microstructure, and relationship between processing conditions and semiconducting properties is necessary to achieve further improvements in performance. In this study, the one-step direct synthesis mechanism and semiconducting properties of Mg<sub>3</sub>Sb<sub>2</sub> were systematically investigated via PECS of mixed elemental Mg and Sb powders, with a focus on the effects of the initial Mg/Sb ratio, sintering temperature, and atmosphere. The mixed powders were consolidated via PECS under uniaxial pressure in either an Ar atmosphere or vacuum. At 573&#xa0;K, unreacted Mg and Sb phases were predominant, whereas α-Mg<sub>3</sub>Sb<sub>2</sub> was the dominant phase at 673&#xa0;K, suggesting that the synthesis reaction proceeded via a solid-state process. Above 973&#xa0;K, the microstructure was largely homogeneous and consisted primarily of α-Mg<sub>3</sub>Sb<sub>2</sub> with traces of MgO. Microstructural analyses revealed that higher sintering temperatures improved both densification and grain growth. Thermoelectric measurements demonstrated that the carrier type and transport properties depend strongly on the processing atmosphere and Mg/Sb ratio. Samples prepared from Mg-rich starting powders (Mg/Sb = 2.125) and sintered at 973&#xa0;K in Ar exhibited a consistently negative Seebeck coefficient during both heating and cooling cycles, indicating stable n-type behavior. In contrast, samples with Mg/Sb ratios of 1.875 and 1.625 exhibited a change in carrier type from n-type to p-type during measurement, whereas those with a near-stoichiometric composition (Mg/Sb = 1.50) exhibited p-type conduction. At 1073&#xa0;K, n-type conduction was observed in Ar, whereas p-type conduction was observed in vacuum. Our results suggest that sintering in an Ar atmosphere using an Mg-rich starting powder with a composition exceeding the stoichiometric ratio can help achieve the one-step direct synthesis of n-type Mg<sub>3</sub>Sb<sub>2</sub> without dopant via PECS.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Effect of one-step synthesis conditions during pulsed electric current sintering on the semiconductor properties of Mg3Sb2

  • 期刊论文

  • 发表日期：

    2025年10月27日

查看全文
  • Jun-ichi Tani,
  • Hiromichi Ishikawa

摘要

Magnesium-based thermoelectric semiconductors have promising applications in automobiles and aircraft. Although a pulsed electric current sintering (PECS)-based one-step synthesis and sintering of impurity-doped Mg3Sb2 with high thermoelectric performance has been reported, a better understanding of the synthesis process, resulting microstructure, and relationship between processing conditions and semiconducting properties is necessary to achieve further improvements in performance. In this study, the one-step direct synthesis mechanism and semiconducting properties of Mg3Sb2 were systematically investigated via PECS of mixed elemental Mg and Sb powders, with a focus on the effects of the initial Mg/Sb ratio, sintering temperature, and atmosphere. The mixed powders were consolidated via PECS under uniaxial pressure in either an Ar atmosphere or vacuum. At 573 K, unreacted Mg and Sb phases were predominant, whereas α-Mg3Sb2 was the dominant phase at 673 K, suggesting that the synthesis reaction proceeded via a solid-state process. Above 973 K, the microstructure was largely homogeneous and consisted primarily of α-Mg3Sb2 with traces of MgO. Microstructural analyses revealed that higher sintering temperatures improved both densification and grain growth. Thermoelectric measurements demonstrated that the carrier type and transport properties depend strongly on the processing atmosphere and Mg/Sb ratio. Samples prepared from Mg-rich starting powders (Mg/Sb = 2.125) and sintered at 973 K in Ar exhibited a consistently negative Seebeck coefficient during both heating and cooling cycles, indicating stable n-type behavior. In contrast, samples with Mg/Sb ratios of 1.875 and 1.625 exhibited a change in carrier type from n-type to p-type during measurement, whereas those with a near-stoichiometric composition (Mg/Sb = 1.50) exhibited p-type conduction. At 1073 K, n-type conduction was observed in Ar, whereas p-type conduction was observed in vacuum. Our results suggest that sintering in an Ar atmosphere using an Mg-rich starting powder with a composition exceeding the stoichiometric ratio can help achieve the one-step direct synthesis of n-type Mg3Sb2 without dopant via PECS.