Xie Hanhui, Wang Heng, Fu Chenguang, Liu Yintu, Snyder G Jeffrey, Zhao Xinbing, Zhu Tiejun
State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
Department of Materials Science, California Institute of Technology, Pasadena, CA 91125, (USA).
Sci Rep. 2014 Nov 3;4:6888. doi: 10.1038/srep06888.
The intrinsic structural disorder dramatically affects the thermal and electronic transport in semiconductors. Although normally considered an ordered compound, the half-Heusler ZrNiSn displays many transport characteristics of a disordered alloy. Similar to the (Zr,Hf)NiSn based solid solutions, the unsubstituted ZrNiSn compound also exhibits charge transport dominated by alloy scattering, as demonstrated in this work. The unexpected charge transport, even in ZrNiSn which is normally considered fully ordered, can be explained by the Ni partially filling interstitial sites in this half-Heusler system. The influence of the disordering and defects in crystal structure on the electron transport process has also been quantitatively analyzed in ZrNiSn1-xSbx with carrier concentration nH ranging from 5.0 × 10(19) to 2.3 × 10(21) cm(-3) by changing Sb dopant content. The optimized carrier concentration nH ≈ 3-4 × 10(20) cm(-2) results in ZT ≈ 0.8 at 875K. This work suggests that MNiSn (M = Hf, Zr, Ti) and perhaps most other half-Heusler thermoelectric materials should be considered highly disordered especially when trying to understand the electronic and phonon structure and transport features.
本征结构无序对半导体中的热输运和电子输运有显著影响。尽管通常被认为是一种有序化合物，但半赫斯勒ZrNiSn却表现出许多无序合金的输运特性。与基于(Zr,Hf)NiSn的固溶体类似，未被取代的ZrNiSn化合物也表现出以合金散射为主导的电荷输运，正如本工作所证明的那样。即使在通常被认为完全有序的ZrNiSn中出现的这种意外的电荷输运，也可以通过镍在这个半赫斯勒体系中部分填充间隙位置来解释。通过改变Sb掺杂剂含量，在载流子浓度nH范围为5.0×10(19)至2.3×10(21) cm(-3)的ZrNiSn1-xSbx中，也对晶体结构中的无序和缺陷对电子输运过程的影响进行了定量分析。优化的载流子浓度nH≈3 - 4×10(20) cm(-2)在875K时导致ZT≈0.8。这项工作表明，MNiSn（M = Hf、Zr、Ti）以及可能大多数其他半赫斯勒热电材料都应被视为高度无序的，特别是在试图理解其电子和声子结构以及输运特性时。
