Crystal structure and thermoelectric properties of type-I clathrate compounds in the Ba-Ga-Ge system

Norihiko L. Okamoto, Kyosuke Kishida, Katsushi Tanaka, Haruyuki Inui

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48 Citations (Scopus)

Abstract

The crystal structure and thermoelectric properties of type-I clathrate compounds in the Ba-Ga-Ge system have been investigated as a function of Ga content. The solid solubility of Ga in the type-I clathrate compounds is determined to be X=16 when expressed with the formula of Ba8 GaX Ge46-X. As the Ga content increases, the crystal structure changes from a superlattice structure to the normal type-I clathrate structure with the transition occurring at X=3.5-5. The density of Ge vacancies in the type-I clathrate phase decreases as the Ga content increases. The absolute values of electrical resistivity and Seebeck coefficient increase, while that of lattice thermal conductivity decreases with the increase in the Ga content. The changes in electrical resistivity and Seebeck coefficient are explained in terms of the number of excess electrons, while the change in lattice thermal conductivity is explained in terms of the extent of the rattling motion of Ba atoms encapsulated in the cage structure.

Original languageEnglish
Article number073504
JournalJournal of Applied Physics
Volume100
Issue number7
DOIs
Publication statusPublished - 2006

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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