Improvement of Thermoelectric Performance of Intermetallic Compound Phases by Reduction of Thermal Conductivity through Phonon Scattering

通过声子散射降低热导率改善金属间化合物相的热电性能

基本信息

批准号：
16360345
负责人：
KIMURA Yoshisato
金额：
$ 9.54万
依托单位：
Tokyo Institute of Technlogy
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

We have focused on half-Heusler MNiSn (M=Hf, Zr) as potential candidates for n-type thermoelectric materials used at high temperatures around 1000 K. It is possible to achieve large Seebeck coefficient and low electrical resistivity in single-phase alloys fabricated by directional solidification using the optical floating zone melting method (OFZ-DS). To further improve thermoelectric properties through lowering the lattice thermal conductivity, we proposed a new fabrication process combining OFZ-DS method with hot-pressing (HP) aiming to produce composite microstructures. It is advantageous to introduce interfaces for reducing the lattice thermal cnductivity by phonon scattering. Monolithic half-Heusler alloy powders were prepared from OFZ-DS ingots, and sintered by HP under various conditions. In HfNiSn/ZrNiSn composite, continuous solid solution (Hf, Zr) NiSn phase plays a role to reduce the lattice thermal conductivity by the solid solution effect. A composite of fine ZrO_2 particl … More es homogeneously dispersed in the HfNiSn matrix was also prepared aiming to reduce the lattice thermal conductivity. We anticipated that electrical properties would be sacrificed by introduced interfaces, though, excellent power factors can be achieved. Thermal diffusivity can be apparently reduced by introducing interfaces while heat capacity is affected by interfaces and impurity phases formed during HP process. It is hard to suppress the formation of impurity oxide phases during HP process. Considering the oxide formation in the sintering process, HfNiSn/ZrNiSn composite was sintered under the Ar-4%H_2 deoxidizing atmosphere using compact powders without applying load. We found that deoxidizing atmosphere is quite effective to suppress the oxide formation and that thermal conductivity can be lowered by controlling density, i.e. porosity, of sintered specimens. It indicates that the optimization of density by controlling the applied load is effective to achieve the best balance of low thermal conductivity and excellent electrical properties, which leads us to maximize thermoelectric performance of half-Heusler based thermoelectric materials. Less

我们专注于Half-Heusler MNISN（M = HF，ZR），作为在高温约为1000 K的高温下使用的N型热电材料的潜在候选物。有可能在单相合金中实现大型Seebeck Core和低电抗性，并使用使用光学浮动区融化方法（Ofz-ds-ofz-ds）在单相合金中实现。为了通过降低晶格导热率进一步改善热电特性，我们提出了一种新的制造工艺，将OFZ-DS方法与热压（HP）相结合，旨在产生复合微观结构。引入界面来降低通过声子散射降低晶格的热cnductitive是有利的。单层半手合金粉是由OFZ-DS归纳制备的，并在各种条件下被HP烧结。在HFNISN/ZRNISN复合材料中，连续固体溶液（HF，ZR）NISN相在固体溶液效应中降低晶格导热率。精细的Zro_2颗粒的复合材料……更多地分散在HFNISN矩阵中的ES还准备了降低晶格导热率。我们预计将通过引入的界面来牺牲电气性能，但是可以实现出色的功率因子。在HP过程中形成的界面和杂质阶段的影响时，可以通过引入界面引入界面来显然可以降低热扩散率。在HP过程中，很难抑制杂质氧化物相的形成。考虑到烧结过程中的氧化物形成，HFNISN/ZRNISN复合材料在AR-4％H_2脱氧大气下使用紧凑的粉末烧结而不施加载荷。我们发现脱氧大气可以抑制氧化物的形成非常有效，并且可以通过控制密度，即孔隙率，即烧结样本的密度来降低热导率。它表明通过控制施加的负载来优化密度可以有效地实现低导热率和出色的电特性的最佳平衡，从而使我们最大程度地提高了基于半身的热电学材料的热电性能。较少的