Mg_(2)(Si,Sn)合金大尺寸试样低温固相反应法制备及其热电性能

Large-scale Preparation Through the Low-temperature Solid Phase Reaction Method and Thermoelectric Properties of Mg_(2)(Si,Sn)Alloys

Mg_(2)(Si,Sn)合金是一种受到广泛关注的中温区热电材料,具有成本低廉、环境友好等优点。Mg_(2)(Si,Sn)材料研究中非常重要的一环在于如何实现对Mg元素的精准控制,采用低温固相反应法可能是一种切实有效的方法。本研究通过低温固相反应法成功制备了高质量Mg_(2)(Si,Sn)合金试样,并将此方法应用至百克级Mg_(2)Si_(0.35)Sn_(0.635)Sb_(0.015)大尺寸试样的制备中,研究了大尺寸试样不同区域的热电性能及其均匀性。实验结果表明低温固相反应法能有效抑制Mg元素的挥发,实现对其较为精准的成分控制;制得的大尺寸试样的致密度沿压力方向存在规律性分布,越靠近试样中心材料致密度越高,相应地其组分含量和热电性能也随之变化。在640 K时,Mg_(2)Si_(0.35)Sn_(0.635)Sb_(0.015)大尺寸试样在所研究的不同区域最高zT值约为0.75,平均zT值达到0.66。

Mg_(2)(Si,Sn)based thermoelectric(TE)materials have attracted wide attention due to the advantages of low cost and environmentally friendly chemical constituents.How to achieve the precise control of Mg content is very significant in the research of Mg_(2)(Si,Sn)materials,while the low-temperature solid phase reaction method may be a practical and effective approach.High-quality Mg_(2)(Si,Sn)alloys were successfully synthesized by the low-temperature solid phase reaction method in this work,and also this method was applied to prepare hundred-gram scale Mg_(2)Si_(0.35)Sn_(0.635)Sb_(0.015)bulk sample.Thermoelectric properties and homogeneity in different regions of the large-scale sample were systematically studied.It is found that the low-temperature solid phase reaction method can effectively inhibit the volatilization of Mg element and achieve the composition control precisly.Along the pressure direction,the density of the large-scale bulk sample is regularly distributed,with the closer to the center of the sample,the higher the density is.Meanwhile the element contents and TE properties change with different regions of the large-scale sample as well.At 640 K,the highest zT value of Mg_(2)Si_(0.35)Sn_(0.635)Sb_(0.015)bulk sample was close to 0.75,and the average zT value reached 0.66.