Fabrication and reliability evaluation of CoSb3/W–Cu thermoelectric element

Joining of thermoelectric material with electrode is the key technique in the construction of thermoelectric device for the practical application. In this study, a suitable W–Cu alloy electrode was introduced into CoSb3-based element with insertion of Ti layer by means of spark plasma sintering. Finite element analysis showed that the maximum thermal residual stress appeared at the cylindrical surface zone close to the CoSb3/electrode interface. SEM results showed that an intermetallic compound (IMC) layer formed at the CoSb3/Ti interface. After accelerated thermal aging, a three-layer IMC structure was observed at the CoSb3/Ti interface and EDS analysis confirmed that the IMC layers were composed of TiCoSb, TiSb2 and TiSb. The CoSb3/Ti/W80Cu20 elements had sufficient shear strength for the reliability of thermoelectric device. The contact resistance of CoSb3/Ti/W–Cu was minimal and below the 50 μΩ cm2, indicating the element exhibited a good electrical contact. The reliability evaluation showed that the element had high thermal duration stability.

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► The CTE of W80Cu20 alloy matches with the CoSb3 material.
► The CoSb3/electrode interface is well bonded.
► IMC layers formed at the CoSb3/Ti interface during thermal aging.