New thermoelectric materials with high performance (ZT>l)-Re silicide 4

由于对环境安全的日益关注，热电材料重新引起人们的兴趣。热电性能通常用所谓的无量纲优值ZT来评价，其中Z=α^2σ/κ，α、σ、κ分别表示塞贝克系数、电导率和热导率。ZT值越大，热电性能越好，一般认为热电材料要实际应用必须满足ZT>1的条件。我们最近发现，稀土硅化物表现出一个大的ZT值接近ZT=1。在本研究中，我们努力通过三元合金化进一步提高这种稀土硅化物的热电性能。我们预期性能的改善不仅通过电子结构的变化，而且通过微观结构的变化，如在密度和排列的Si空位的变化和无公度结构的形成。比娜 ...更多信息 当沿[001]沿着测量时，ry硅化物在800 K下表现出ZT=0.75。当过渡金属被Re取代时，随着合金含量的增加，通常形成从剪切结构开始的自适应结构。发生从剪切到自适应结构的转变的合金化量取决于每种合金化元素。这在Mo和W的低含量下发生，而自适应结构在Ru、Fe、Cr和Nb的溶解度极限内不形成。一般来说，当合金为自适应型组织时，性能得到改善，而当合金为剪切型组织时，性能没有明显改善。2at.%时，ZT值达到0.85 Mo添加的Re硅化物，其表现出自适应结构。当添加Al以取代Si时，在孪晶界附近局部形成自适应结构。这导致热导率显著降低，导致在400 K下Zt值大于1。少

There is a renewed interest in thermoelectric materials because of the increased attention to environmental safety. The performance of thermoelectric properties is usually evaluated with the so-called dimensionless figure of merit ZT where Z=α^2σ/κ, and, α, σ, κ denote Seebeck coefficient, electrical conductivity respectively and thermal conductivity. The performance is better for the larger ZT value and it is generally believed that the condition of ZT>1 must be satisfied for thermoelectric materials to be practically used. We have recently found that Re-silicide exhibits a large ZT value close to ZT=1. In the present study, we made an effort to further improve the thermoelectric performance of this Re-silicide through ternary alloying. We expect the performance improvement not only through the changes in electronic structure but also through microstructure changes such as the change in the density and arrangement of Si vacancies and the formation of incommensurate structure. The bina … More ry silicide exhibits ZT=0.75 at 800K when measured along [001]. When transition-metals are replaced with Re, incommensurate microstructures are usually formed starting with the shear structure followed by the adaptive structure as the alloying content increases. The alloying amount at which the transition from the shear to adaptive structures occurs depend on each alloying elements. This occurs at a low content for Mo and W while the adaptive structure does not form within the solubility limit for Ru, Fe, Cr and Nb. Generally speaking, the property improvement occurs when the alloy takes the adaptive-type structure, whereas when the alloy takes the shear-type structure, no significant improvement occurs. The ZT value of 0.85 is achieved for 2at.% Mo added Re-silicide, which exhibits an adaptive structure. When Al is added to replace Si, the adaptive structure is locally formed in the close vicinity of twin boundaries. This leads to the significantly decreased thermal conductivity, resulting in the Zt value greater than 1 at 400K. Less