Comprehensive study of α-MgAgSb: Microstructure, carrier transport properties, and thermoelectric performance under ball milling techniques

Abstract

• We systematically analyzed the crystal structure, microstructure, electronic, and thermal transport properties of α-MgAgSb using various ball milling techniques. • By controlling the microstructure, we enhanced charge carrier mobility, reduced resistivity, and improved the thermoelectric performance of α-MgAgSb. • Low-temperature resistivity analysis revealed distinct scattering mechanisms based on impurity levels and carrier mobility. • The distribution of Ag 3 Sb was found to increase interfacial resistance, impacting thermal conductivity as demonstrated using Effective Medium Theory methods. • Precise control over synthesis conditions was shown to be critical for optimizing the thermoelectric performance of α-MgAgSb. This study investigates the crystal structure, microstructure, electronic, thermal transport properties, and thermoelectric performance of α-MgAgSb synthesized through various ball milling techniques. Variations in synthesis methods can significantly impact thermoelectric performance. Our findings indicate that impurity phases, particularly the secondary phase Ag₃Sb, hinder grain growth and decrease carrier mobility. By systematically adjusting milling conditions, the increased grain size resulting from the suppression of impurity formation improves charge carrier mobility and enhances the power factor. Low-temperature resistivity analysis reveals distinct scattering mechanisms influenced by impurity levels. α-MgAgSb with a tiny content of Sb primarily exhibits electron-electron scattering, whereas higher impurity levels introduce both electron-electron and electron-phonon scattering. Additionally, thermal conductivity analysis using three Effective Medium Theory (EMT) methods shows that the distribution of Ag 3 Sb increases interfacial resistance. The maximum zT value of 1.36 was achieved in a compound with an α-MgAgSb to Sb ratio of 99%:1%. We demonstrate the effects of systematic adjustments in the synthesis for α-MgAgSb on impurity phases, carrier transport, and thermoelectric properties. As shown in Figure (a). the power factor increases with increasing carrier mobility, which is the key factor in enhancing thermoelectric performance. Among the samples, S4 exhibits higher carrier mobility and power factor, leading to improved zT values across the entire measured temperature range, as depicted in Figure (b). This study systematically elucidates the roles of impurity phases in the carrier transport mechanisms and thermoelectric properties of α-MgAgSb.

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