Thermoelectric Properties of Na2ZnSn5 Dimorphs with Na Atoms Disordered in Tunnels
Thermoelectric Properties of Na2ZnSn5 Dimorphs with Na Atoms Disordered in Tunnels
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DOI：
10.1021/acs.chemmater.6b04896
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发表时间：
2017-01
影响因子：
8.6
通讯作者：
M. Kanno;Takahiro Yamada;T. Ikeda;H. Nagai;H. Yamane
中科院分区：
文献类型：
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作者：
M. Kanno;Takahiro Yamada;T. Ikeda;H. Nagai;H. Yamane
二晶型物（两种多晶型物）hP-Na2ZnSn5（亚稳相）和tI-Na2ZnSn5（稳定相）的铸锭是由具有化学计量组成的组成元素熔体通过在1小时内从773 K到500 K（平均4.6 K min-1）炉冷以及以0.5 K min-1的速率从703 K到室温缓慢冷却来制备的。根据在 295 K 下测量的铸锭的电导率、塞贝克系数和热导率，计算出 hP-Na2ZnSn5 和 tI-Na2ZnSn5 的无量纲品质因数 (ZT) 分别为 0.21 和 2.8 × 10-2。热导率的晶格分量估计为 1.10 W m–1 K–1 (hP-Na2ZnSn5) 和 0.61 W m–1 K–1 (tI-Na2ZnSn5)。两相的单晶X射线衍射分析结果表明，Zn/Sn骨架孔道中的Na原子具有离散（静态）和较大的连续（动态）位置无序性，这可以起到降低晶格厚度的作用。
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 th...