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Materials 2018, 11(6), 946;

Crystal Chemistry and Thermoelectric Properties of Type-I Clathrate Ba8Ni∼3.8SixGe42.2−x (x = 0, 10, 20, 42.2)

School of Metallurgy, Northeastern University, Shenyang 110819, China
Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8–10, 1040 Vienna, Austria
State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China
Institute of Materials Chemistry and Research, University of Vienna, Währingerstr. 42, 1090 Vienna, Austria
Authors to whom correspondence should be addressed.
Received: 10 May 2018 / Revised: 25 May 2018 / Accepted: 1 June 2018 / Published: 4 June 2018
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Thermoelectric materials are actively considered for waste heat recovery applications. To improve the heat to electricity conversion efficiency, fundamental understanding on composition, crystal structure, and interrelation with the thermoelectric properties is necessary. Here, we report the chemical and thermoelectric properties of type-I clathrates Ba 8 Ni 3.8 Si x Ge 42.2 x (x = 0, 10, 20, 42.2), to show that the Si substitution can retain the low lattice thermal conductivity as in pure Ge-based clathrates by adding defects (cage distortion) scattering and/or alloying effect, and the charge carrier concentration can be optimized and thus the electronic properties can be improved by tailoring the vacancy content. We demonstrate the vacancies in the pure Ge-based compound by Rietveld refinement, and possible vacancies in the quaternary compound by transport property measurements. We also show that, for intrinsic property studies in these compounds with such a complex crystal structure, a heat treatment for as cast alloys is necessary for phase purity and composition homogeneity. The highest Z T value of 0.19 at 550 ° C is reached in the compound with x = 10 . View Full-Text
Keywords: thermoelectric properties; crystal structure; clathrates; phase equilibrium thermoelectric properties; crystal structure; clathrates; phase equilibrium

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Dong, Y.; Ding, X.; Yan, X.; Zhang, L.; Tang, Z.; Chen, W.; Rogl, P.; Paschen, S. Crystal Chemistry and Thermoelectric Properties of Type-I Clathrate Ba8Ni∼3.8SixGe42.2−x (x = 0, 10, 20, 42.2). Materials 2018, 11, 946.

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