Thermoelectric Properties of Na2ZnSn5 Dimorphs with Na Atoms Disordered in Tunnels

Masahiro Kanno, Takahiro Yamada, Takuji Ikeda, Hideaki Nagai, Hisanori Yamane

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    3 Citations (Scopus)

    Abstract

    Ingots of dimorphs (two polymorphs), hP-Na2ZnSn5 (metastable phase) and tI-Na2ZnSn5 (stable phase), were prepared from the melt of the constituent elements with the stoichiometric composition by furnace cooling from 773 to 500 K within 1 h (4.6 K min-1 on average) and slow cooling at a rate of 0.5 K min-1 from 703 K to room temperature, respectively. From the electrical conductivities, Seebeck coefficients, and thermal conductivities measured at 295 K for the ingots, the dimensionless figures of merit (ZT) of hP-Na2ZnSn5 and tI-Na2ZnSn5 were calculated to be 0.21 and 2.8 × 10-2, respectively. The lattice components of the thermal conductivities were estimated to be 1.10 W m-1 K-1 (hP-Na2ZnSn5) and 0.61 W m-1 K-1 (tI-Na2ZnSn5). Results of the crystal structure analysis by single-crystal X-ray diffraction of both phases demonstrated that the Na atoms in the tunnels of Zn/Sn frameworks had discrete (static) and large continuous (dynamic) positional disorder, which could play a role in reducing the lattice thermal conductivity due to phonon scattering. The disorder of 23Na nuclei was also evidenced by the solid-state nuclear magnetic resonance spectroscopy.

    Original languageEnglish
    Pages (from-to)859-866
    Number of pages8
    JournalChemistry of Materials
    Volume29
    Issue number2
    DOIs
    Publication statusPublished - 2017 Jan 24

    ASJC Scopus subject areas

    • Chemistry(all)
    • Chemical Engineering(all)
    • Materials Chemistry

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