Thermoelectric efficiency of graded SicGe1–c alloys

We consider SicGe1–c graded systems of length L=3mm and L=100 nm, under the action of an electric field E, and crossed by an electrical current i, the two sides of which are kept at two different temperatures Th and Tc. The dependence on composition and temperature of the thermal conductivity is analyzed. We evaluate the thermal conductivity in correspondence of the constant temperatures T=300 K, T=400 K, and T=500K and investigate the thermoelectric efficiency of the system as a function of the stoichiometric variable c and of the effective temperature gradient (Th-Tc)/L. For each temperature, we calculate the values of c in the interval [0, 1] which realize the optimal efficiency of the thermoelectric energy conversion. The corresponding values of the thermal conductivity are determined as well. For L=3mm, we find that the best efficiency of thermoelectric energy conversion is achieved at T=500K, c=0.325568, and lambda 7.3444 Wm^(-1) K^(-1). For L=100 nm, we obtain the best efficiency at T=500K, c= 0.613937, and lamba=0.1510 Wm^(-1) K^(-1).