Structural and thermoelectric properties of Mn15Si26, Mn4Si7 and MnSi2, synthesized using arc-melting method

Manganese (Mn) and silicide (Si) are important earth-abundant and non-toxic elements, and alloys integrating these elements are practical thermoelectrics. Higher manganese silicide’s, Mn15Si26 (1.73), Mn4Si7 (1.75), and MnSi2 have been synthesized using the arc-melting method under the argon atmosphere. We present a systematic study of the effects of Si content on phase formation, transport, and thermoelectric characteristics in these alloys. The powder X-ray diffraction (XRD) data reveals that Mn15Si26, Mn4Si7 and MnSi2 crystallize in the tetragonal structure, having I 4¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{4 }$$\end{document} 2d, P 4¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{4 }$$\end{document} C2 and P 4¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{4 }$$\end{document} C2 space groups, respectively. Additionally, the XRD patterns suggest that increased Si content facilitates decreased secondary MnSi phase, attributed to the Si-site occupancy limit. Temperature-dependent resistivity suggests the alloys metallic nature and could fit the empirical model in the measured temperature range 5-300 K. Besides, the positive Seebeck coefficient (S) pragmatic in alloys suggests that holes serve as the majority carriers (p-type). The improved power factor (PF) noted in MnSi2 with a maximum value of 279.2 μW⁄(mK2) at 300 K. This improvement in PF can be due to an increase in density of states effective mass with increase in Si content.