Generic Approach for Contacting Thermoelectric Solid Solutions: Case Study in n- and p-Type Mg₂Si_0.3Sn_0.7

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Contacting thermoelectric (TE) legs is crucial for device performance, but material compatibility issues arise with compositional changes in TE solid solutions.
• Mismatched thermal expansion coefficients often lead to unsuitable contact materials, posing a significant challenge for optimizing TE materials.

Purpose of the Study:

• To develop a versatile, single-step metallization strategy applicable to a broad compositional range of thermoelectric solid solutions.
• To address the challenge of finding suitable contact materials for advanced thermoelectric materials.

Main Methods:

• A multilayer, single-step contacting approach was proposed, featuring an outer metal foil, an intermediate diffusion barrier layer (TE material mixed with metal powder), and an inner TE material layer.
• The technique was applied to n- and p-doped Mg2Si0.3Sn0.7 using Cu and Ni, with monoblock sintering for single-step compaction.
• Microscopic analysis, intermetallic phase identification, and electrical contact resistance (rc) measurements were performed.

Main Results:

• A well-bonded, crack-free interface was achieved, with the MgNi2Sn phase identified as critical for preventing interdiffusion.
• Low electrical contact resistance values of 3 μΩ cm² for n-type and 19 μΩ cm² for p-type legs were obtained.
• Post-annealing stability tests showed minimal changes in the interface and contact resistance, confirming the technique's robustness.

Conclusions:

• The proposed multilayer single-step metallization technique offers a viable solution for contacting diverse thermoelectric solid solutions.
• This method ensures excellent interface integrity and low contact resistance, crucial for the long-term stability and performance of thermoelectric devices.