Papers by Keyword: Sb

Abstract: We investigated the effects of Fe3O4 (0~0.1 wt.%) on the thermoelectric properties of Bi1Sb4Te7.5 alloy prepared by mechanical alloying process. The Seebeck coefficient increased with Fe3O4 content, but the power factor decreased with Fe3O4 content because of the decreased electrical conductivity. The thermal conductivity decreased with Fe3O4. The carrier concentration measured by the Hall effect measurement decreased with Fe3O4. The thermal conductivity of 0.1 wt.% Fe3O4 alloy was 0.814 W/Km, 20%lower than that of Fe3O4 free alloy. As a result, the small addition of Fe3O4 improved the Z value owing to the decreased thermal conductivity by adding Fe3O4. The Z value of 0.01 wt.% Bi1Sb4Te7.5 alloy was 3.1×10-3 /K, the highest value among the prepared alloys.

Abstract: We have investigated the lattice diffusion of B and Sb by means of molecular beam epitaxy in Si1−xGex (x < 0.2) layers grown on Si(001) substrate. Using Si1−xGex relaxed buffers we were able to differentiate the chemical effect (change in the Ge composition) as opposite to the biaxial stress effect (due to the epitaxy on Si) on dopant diffusion. B diffusion follows a behavior opposite to Sb diffusion versus Ge composition and biaxial stress. These results are explained in view of the difference of diffusion mechanism between B (interstitials) and Sb (vacancies). We also show that dopant diffusion follows contrasting behaviors under biaxial pressure and hydrostatic pressure, and that the activation volume of dopant diffusion is of opposite sign for biaxial pressure and for hydrostatic pressure. This is explained using a formalism based on the extra work done by the system for diffusion under pressure, concluding that for biaxial stress the activation volume depends mainly on the relaxation volume linked to the defect formation.