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

Abstract

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 Ag₃Sb 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%.