PbTe基热电电极接头界面扩散与反应及电极材料优化

发布时间：2018-06-17 13:20

  本文选题：Pb + Te基热电材料　； 参考：《清华大学》2015年博士论文

【摘要】：PbTe基热电器件能直接将热能转化为电能而发电,主要应用于太空探测器电源、汽车废热回收和工业废热利用。目前,PbTe基热电电极接头主要采用机械方法连接,导致器件重量增加、结构复杂和使用不便,接头接触电阻和热阻也较大,降低了器件热电转化效率;另外,PbTe基热电电极接头高温端要求在550oC及一定应力条件下长期稳定工作,因此接头制备难度较大。本论文以开发高性能PbTe基热电电极接头为目标,期望获得综合性能良好的冶金结合接头。本论文首先采用一步热压烧结法进行Ni/PbTe、Nb/PbTe、Fe/PbTe和Mo/PbTe四种热电电极接头的连接试验,研究了接头的界面结构,分析了接头界面扩散与反应行为,讨论了接头界面结构形成机制。对Ni/PbTe接头而言,Ni与PbTe可能形成共晶液相,界面既可能发生液固或固固等置换反应生成Ni3±xTe2相和液态Pb,还可能发生反应析出三元相和共晶相;形成的液相和生成的液态Pb会大量渗透入Ni箔晶界。对Nb/PbTe接头而言,Nb与PbTe不会形成共晶液相,Nb与PbTe发生固相置换反应生成Nb3Te4相和液态Pb,生成的液态Pb也不会渗透入Nb晶界。Nb3Te4反应层的生长是由Nb原子通过Nb3Te4扩散至PbTe界面的扩散速率控制的生长过程。对Fe/PbTe和Mo/PbTe接头而言,Fe和Mo与PbTe在连接温度范围内既不会形成共晶液相也不会发生置换反应。本论文选用NiFeMo合金和Fe/Ni双层金属两种电极材料与PbTe进行连接,分析了界面结构及其形成机理。相比Ni/PbTe接头,NiFeMo与PbTe的共晶温度提高,NiFeMo与PbTe没有发生明显的界面反应,Fe原子和Mo原子的存在抑制了Ni与PbTe的界面反应。对Fe/Ni/PbTe接头而言,可能形成五种界面结构,分别为:(1)Fe(Ni)/非连续颗粒状(Fe,Ni)1.12Te/PbTe(Ni);(2)Fe/Fe(Ni)/Ni(Fe)/PbTe(Ni);(3)Fe/Fe0.88Ni0.12/Ni(Fe)/Ni3±xTe2/PbTe(Ni);(4)Fe/Fe0.88Ni0.12/(Fe,Ni)1.26Te+Pb/PbTe;(5)Fe/孔洞Fe0.88Ni0.12/(Fe,Ni)1.26Te+Pb/PbTe。通过对各接头界面结构、力学性能、热电性能和电学性能的分析,结果表明Fe/6μmNi/PbTe接头在连接工艺650℃/150min时制备的界面结构Fe/Fe0.88Ni0.12/Ni(Fe)/Ni3±xTe2/PbTe较优,接头既能实现良好连接又能抑制晶界渗透,是较理想的PbTe基热电电极接头。
[Abstract]:PbTe based thermoelectric devices can directly convert heat energy into electric energy and generate electricity. It is mainly used in space detector power source, automobile waste heat recovery and industrial waste heat utilization. At present, the PbTe based thermoelectric electrode joint is mainly connected by mechanical method, which leads to the increase of device weight, the complexity of structure and the inconvenience of application. The contact resistance and thermal resistance of the joint are also large, which reduces the thermoelectric conversion efficiency of the device. In addition, the high temperature end of PbTe based thermoelectric electrode joint is required to work stably for a long time under 550 OC and certain stress conditions, so it is difficult to prepare the joint. The aim of this thesis is to develop high performance PbTe based thermoelectric electrode joints and to obtain metallurgical bonding joints with good comprehensive properties. In this paper, the bonding tests of four kinds of thermoelectric electrode joints (Ni / PbTeN, Fe / PbTe and Mo / PbTe) were carried out by means of one step hot pressing sintering method. The interface structure of the joint was studied, the diffusion and reaction behavior of the interface was analyzed, and the formation mechanism of the interface structure of the joint was discussed. For Ni / PbTe joints, the eutectic liquid phase may be formed between Ni / PbTe and Ni / PbTe. The interface may produce Ni3 卤xTe2 phase and liquid Pb2 phase, and precipitate ternary and eutectic phases at the interface. The formed liquid phase and the resulting liquid Pb permeate into the grain boundary of Ni foil in large quantities. For NB / PbTe joints, NB and PbTe do not form eutectic liquid phase substitution reaction between NB and PbTe to form Nb3Te4 phase and liquid PbTe, and the resulting liquid Pb will not permeate into NB grain boundary. Nb3Te4 reaction layer grows by NB atom diffusing through Nb3Te4 to PbTe. The diffusion rate of the interface controls the growth process. For Fe / PbTe and Mo / PbTe joints, there is neither eutectic liquid phase nor substitution reaction between Fe, Mo and PbTe in the range of bonding temperature. In this paper, two kinds of electrode materials, NiFeMo alloy and Fe / Ni bilayer metal, were used to connect with PbTe, and the interface structure and formation mechanism were analyzed. Compared with the eutectic temperature of NiFeMo and PbTe, there is no obvious interfacial reaction between NiFeMo and PbTe. The existence of Fe atom and Mo atom inhibits the interfacial reaction between Ni and PbTe. 瀵笷e/Ni/PbTe鎺ュご鑰岃█,鍙�鑳藉舰鎴愪簲绉嶇晫闈㈢粨鏋�,鍒嗗埆涓，

本文编号：2031193