Barczak Sonia A, Buckman Jim, Smith Ronald I, Baker Annabelle R, Don Eric, Forbes Ian, Bos Jan-Willem G
Institute of Chemical Sciences and Centre for Advanced Energy Storage and Recovery, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Institute of Petroleum Engineering, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Materials (Basel). 2018 Mar 30;11(4):536. doi: 10.3390/ma11040536.
TiNiSn is an intensively studied half-Heusler alloy that shows great potential for waste heat recovery. Here, we report on the structures and thermoelectric properties of a series of metal-rich TiNiSn compositions prepared via solid-state reactions and hot pressing. A general relation between the amount of interstitial Ni and lattice parameter is determined from neutron powder diffraction. High-resolution synchrotron X-ray powder diffraction reveals the occurrence of strain broadening upon hot pressing, which is attributed to the metastable arrangement of interstitial Ni. Hall measurements confirm that interstitial Ni causes weak n-type doping and a reduction in carrier mobility, which limits the power factor to 2.5-3 mW m K for these samples. The thermal conductivity was modelled within the Callaway approximation and is quantitively linked to the amount of interstitial Ni, resulting in a predicted value of 12.7 W m K at 323 K for stoichiometric TiNiSn. Interstitial Ni leads to a reduction of the thermal band gap and moves the peak ZT = 0.4 to lower temperatures, thus offering the possibility to engineer a broad ZT plateau. This work adds further insight into the impact of small amounts of interstitial Ni on the thermal and electrical transport of TiNiSn.
TiNiSn是一种经过深入研究的半赫斯勒合金，在废热回收方面显示出巨大潜力。在此，我们报告了通过固态反应和热压制备的一系列富金属TiNiSn组合物的结构和热电性能。通过中子粉末衍射确定了间隙Ni含量与晶格参数之间的一般关系。高分辨率同步加速器X射线粉末衍射揭示了热压过程中应变展宽的出现，这归因于间隙Ni的亚稳排列。霍尔测量证实，间隙Ni导致弱n型掺杂并降低载流子迁移率，这将这些样品的功率因子限制在2.5 - 3 mW m⁻¹ K⁻²。热导率在卡洛威近似范围内进行建模，并与间隙Ni的含量定量相关，对于化学计量比的TiNiSn，在323 K时预测值为12.7 W m⁻¹ K⁻¹。间隙Ni导致热带隙减小，并将峰值ZT = 0.4移至更低温度，从而提供了设计宽ZT平台的可能性。这项工作进一步深入了解了少量间隙Ni对TiNiSn热传输和电传输的影响。
