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Title: Gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline type-I Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) clathrates prepared by combining arc melting and spark plasma sintering methods

Abstract

The gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline n-type Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) compounds with the type-I clathrate structure is presented. Samples were prepared by combining arc melting and spark plasma sintering methods. Powder x-ray diffraction, Rietveld analysis, scanning electron microscopy, and energy-dispersive x-ray spectroscopy show that the solubility limit of gallium in the type-I clathrate phase is close to x=15, which is slightly higher than that for a single crystal. The carrier concentration at room temperature decreases from 2 Multiplication-Sign 10{sup 21} cm{sup -3} to 4 Multiplication-Sign 10{sup 20} cm{sup -3} as the Ga content x increases. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity vary systematically with the carrier concentration when the Ga content x varies. The effective mass (2.0m{sub 0}), the carrier mobility (10 cm{sup 2} V{sup -1} s{sup -1}), and the lattice thermal conductivity (1.1 W m{sup -1} K{sup -1}) are determined for the Ga content x=14.51. The dimensionless thermoelectric figure of merit ZT is about 0.55 at 900 K for the Ga content x=14.51. The calculation of ZT using the experimentally determined material parameters predicts ZT=0.8 (900 K) at the optimum carrier concentration of about 2 Multiplication-Sign 10{supmore » 20} cm{sup -3}. - Graphical abstract: The gallium composition dependence of crystallographic and thermoelectric properties is presented on polycrystalline n-type Ba{sub 8}Ga{sub x}Si{sub 46-x} with the type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods. The thermoelectric figure of merit ZT reaches 0.55 at 900 K due to the increase in the Ga content (close to x=15), and a calculation predicts further improvement of ZT at the optimized carrier concentration. Highlights: Black-Right-Pointing-Pointer Crystallographic properties of Ba{sub 8}Ga{sub x}Si{sub 46-x} clathrates are characterized. Black-Right-Pointing-Pointer Arc melting and spark plasma sintering process enables increase of Ga content. Black-Right-Pointing-Pointer We elucidate the Ga composition dependence of thermoelectric properties. Black-Right-Pointing-Pointer Thermoelectric figure of merit ZT is improved due to the increased Ga content. Black-Right-Pointing-Pointer Calculation predicts a potential ZT=0.8 at 900 K at optimized carrier concentration.« less

Authors:
 [1]; ; ;  [1];  [1]
  1. Department of Electrical Engineering, Faculty of Engineering, Tokyo University of Science, Yamaguchi, 1-1-1 Daigaku-Dori, Sanyoonoda 756-0884 (Japan)
Publication Date:
OSTI Identifier:
22149807
Resource Type:
Journal Article
Journal Name:
Journal of Solid State Chemistry
Additional Journal Information:
Journal Volume: 193; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0022-4596
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CLATHRATES; CRYSTALLOGRAPHY; ELECTRIC CONDUCTIVITY; GALLIUM; MELTING; MONOCRYSTALS; PLASMA; POLYCRYSTALS; POWDERS; SCANNING ELECTRON MICROSCOPY; SINTERING; THERMAL CONDUCTIVITY; THERMOELECTRIC PROPERTIES; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY

Citation Formats

Anno, Hiroaki, JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Yamada, Hiroki, Nakabayashi, Takahiro, Hokazono, Masahiro, Shirataki, Ritsuko, and JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075. Gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline type-I Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) clathrates prepared by combining arc melting and spark plasma sintering methods. United States: N. p., 2012. Web. doi:10.1016/J.JSSC.2012.03.069.
Anno, Hiroaki, JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Yamada, Hiroki, Nakabayashi, Takahiro, Hokazono, Masahiro, Shirataki, Ritsuko, & JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075. Gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline type-I Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) clathrates prepared by combining arc melting and spark plasma sintering methods. United States. doi:10.1016/J.JSSC.2012.03.069.
Anno, Hiroaki, JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Yamada, Hiroki, Nakabayashi, Takahiro, Hokazono, Masahiro, Shirataki, Ritsuko, and JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075. Sat . "Gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline type-I Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) clathrates prepared by combining arc melting and spark plasma sintering methods". United States. doi:10.1016/J.JSSC.2012.03.069.
@article{osti_22149807,
title = {Gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline type-I Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) clathrates prepared by combining arc melting and spark plasma sintering methods},
author = {Anno, Hiroaki and JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075 and Yamada, Hiroki and Nakabayashi, Takahiro and Hokazono, Masahiro and Shirataki, Ritsuko and JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075},
abstractNote = {The gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline n-type Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) compounds with the type-I clathrate structure is presented. Samples were prepared by combining arc melting and spark plasma sintering methods. Powder x-ray diffraction, Rietveld analysis, scanning electron microscopy, and energy-dispersive x-ray spectroscopy show that the solubility limit of gallium in the type-I clathrate phase is close to x=15, which is slightly higher than that for a single crystal. The carrier concentration at room temperature decreases from 2 Multiplication-Sign 10{sup 21} cm{sup -3} to 4 Multiplication-Sign 10{sup 20} cm{sup -3} as the Ga content x increases. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity vary systematically with the carrier concentration when the Ga content x varies. The effective mass (2.0m{sub 0}), the carrier mobility (10 cm{sup 2} V{sup -1} s{sup -1}), and the lattice thermal conductivity (1.1 W m{sup -1} K{sup -1}) are determined for the Ga content x=14.51. The dimensionless thermoelectric figure of merit ZT is about 0.55 at 900 K for the Ga content x=14.51. The calculation of ZT using the experimentally determined material parameters predicts ZT=0.8 (900 K) at the optimum carrier concentration of about 2 Multiplication-Sign 10{sup 20} cm{sup -3}. - Graphical abstract: The gallium composition dependence of crystallographic and thermoelectric properties is presented on polycrystalline n-type Ba{sub 8}Ga{sub x}Si{sub 46-x} with the type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods. The thermoelectric figure of merit ZT reaches 0.55 at 900 K due to the increase in the Ga content (close to x=15), and a calculation predicts further improvement of ZT at the optimized carrier concentration. Highlights: Black-Right-Pointing-Pointer Crystallographic properties of Ba{sub 8}Ga{sub x}Si{sub 46-x} clathrates are characterized. Black-Right-Pointing-Pointer Arc melting and spark plasma sintering process enables increase of Ga content. Black-Right-Pointing-Pointer We elucidate the Ga composition dependence of thermoelectric properties. Black-Right-Pointing-Pointer Thermoelectric figure of merit ZT is improved due to the increased Ga content. Black-Right-Pointing-Pointer Calculation predicts a potential ZT=0.8 at 900 K at optimized carrier concentration.},
doi = {10.1016/J.JSSC.2012.03.069},
journal = {Journal of Solid State Chemistry},
issn = {0022-4596},
number = ,
volume = 193,
place = {United States},
year = {2012},
month = {9}
}