TY - JOUR
T1 - Thermoelectric Properties of Na2ZnSn5 Dimorphs with Na Atoms Disordered in Tunnels
AU - Kanno, Masahiro
AU - Yamada, Takahiro
AU - Ikeda, Takuji
AU - Nagai, Hideaki
AU - Yamane, Hisanori
N1 - Funding Information:
This work was supported by JST PRESTO and JSPS KAKENHI (26288105) and was performed under the Cooperative Research Program of Network Joint Research Center for Materials and Devices. A part of this work was financially supported by the AIST-Tohoku University matching fund.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/1/24
Y1 - 2017/1/24
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.chemmater.6b04896
DO - 10.1021/acs.chemmater.6b04896
M3 - Article
AN - SCOPUS:85018517810
VL - 29
SP - 859
EP - 866
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 2
ER -