Contacting Cu Electrodes to Mg₂Si_0.3Sn_0.7: Direct vs. Indirect Resistive Heating

Abstract

Mg₂(Si,Sn)-based thermoelectric materials have been gaining interest in the past years due to their attractive properties. In this work, we present the outcome of using two different approaches to contact n-and p-type Mg₂Si_0.3Sn_0.7 legs with Cu electrodes to study the influence of current on the joining procedures. The first approach is a direct current heating procedure where the current runs directly through the sample, while the second approach uses the current as an indirect source of resistive heating. Results show that Cu diffuses into n- and p-type materials, creating relatively thick and complex reaction layers, both under direct and indirect resistive heating, and these layers have, respectively, an average thickness of 200 and 100 μm. Electrical contact resistance r_c values are also similar for both types, under both joining conditions (<10 μΩ cm²). The directly and indirectly contacted samples were then annealed, and the results for all samples were similar. The reaction layers developed similarly in all cases and the contact resistances remained low (<10 μΩ cm²).