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Phase analysis and determination of local charge carrier concentration in eutectic Mg2Si-Si alloys

TitlePhase analysis and determination of local charge carrier concentration in eutectic Mg2Si-Si alloys
Publication TypeJournal Article
Year of Publication2015
AuthorsLevin, EM, Hanus, R, Cui, J, Xing, Q, Riedemann, T, Lograsso, TA, Schmidt-Rohr, K
JournalMaterials Chemistry and Physics
Volume158
Pagination1-9
Date Published05
Type of ArticleArticle
ISBN Number0254-0584
Accession NumberWOS:000353736700001
KeywordsCrystal structure, Electron microscopy, mg2ge, nuclear magnetic resonance, silicon, Thermal properties, thermal-conductivity, Thermoelectric effect, thermoelectric properties
Abstract

SEM, and Si-29 NMR at 300 K, and the Seebeck effect, electrical resistivity, and thermal conductivity in the temperature range of 300-750 K have been measured. Si-29 NMR detects two distinct signals, at -177 and -80 ppm, in both materials, which are assigned to Mg2Si and Si phases, respectively. Both phases are slightly nonstoichiometric and doped with Mg. Two phases also are found by XRD and electron microscopy. Si-29 NMR spin-lattice relaxation measurements in Mg2Si and Si phases show at least two components, short and long, which can be attributed to different local carrier concentrations, high and low, respectively, reflecting a local electronic inhomogeneity in each phase. The carrier concentrations range between 0.6 x 10(19) and 9 x 10(19) cm(-3). The Seebeck coefficient in both alloys is mostly determined by the Si phase, while the thermal conductivity is limited by the Mg2Si phase with a lower value than that of the Si phase. By utilizing all characterization tools, we show how various experimental methods can be used as complementary methods to better understand the individual and combined properties of multiphase alloys. (C) 2015 Elsevier B.V. All rights reserved.

DOI10.1016/j.matchemphys.2015.03.017
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