SiGe/electrode response to long-term high-temperature exposure

Joints between an n-type Si0.8Ge0.2(P0.3 atomic %) thermoelectric semiconductor and carbon electrodes were prepared by hot-pressing with thin sheets of titanium foil inserted between them at 1528 K in a vacuum. The content of phosphorous, measured using an Inductively Coupled Argon Plasma Emission Spectrometer, decreased from 0.20% to 0.11% after joining. To evaluate the upper limit of heating dependence, the SiGe/carbon electrode was exposed in an argon atmosphere at 1273 K and 1373 K for 300 hours, after which the resistance and Seebeck coefficient were measured. These results showed that the power factor (α²σ) could be effectively evaluated using the Larson-Miller Parameter (C=13.3). SEM and EPMA observations showed the presence of many voids in the junction layer of the SiGe/carbon electrode after exposure. The titanium atoms were enriched in the junction layer, and started diffusing at a temperature of 1273 K or over