Evaluation of Cu-Ni-Based Alloys for Thermoelectric Energy Conversion

The recent revitalization of Ioffe plots (entropy conductivity versus electrical conductivity) reminds us that Isotan (Cu55Ni44Mn1) is an outstanding thermoelectric material with a power factor of up to 60 W cm-1 K-2 at a specific electrical conductivity of almost 20,000 S cm-1 at elevated temperature. Even though, Isotan is widely used in thermoelements for temperature measurement, its high open-circuited thermal conductivity of approximately 70 W cm-1 K-2 [1] hindered further research as a promising thermoelectric material. Isotan was chosen as a starting composition. Influence of partial substitution of Cu and Ni with heavy elements (Sn,W) on the thermoelectric properties was studied. The alloys were fabricated by arc-melting and microstructurally characterized for grain size and elemental composition by scanning electron microscope (SEM) combined with energy-dispersive X-ray (EDXS). Lattice symmetry and parameters were estimated by X-ray diffraction (XRD). Functional properties as Seebeck coefficient, electrical conductivity and power factor were used to evaluate the thermoelectric performance.