Long-Term Stability of the Colossal Seebeck Effect in Metallic Cu2Se

Determination of thermoelectric properties is rather a challenging task, especially during a phase transition, where a drastic change in magnitude of thermoelectric properties is generally observed. In this study, we performed a precise measurement of the Seebeck coefficient on Cu2Se, which was recently reported to possess a colossal Seebeck coefficient with metallic electrical conductivity during a structural phase transition. We confirmed that the colossal Seebeck effect was stable over a long period of time, as high as −0.9 mV under an applied temperature gradient of 1 K. This fact clearly proved that the colossal Seebeck effect observable in metallic Cu2Se is potentially usable for a variety of thermoelectric applications.