Magnetothermoelectric properties of the bulk extruded samples of Bi₈₅Sb₁₅ solid solution with different grain sizes

Abstract

Bulk extruded (including nanostructured) samples of Bi₈₅Sb₁₅ solid solutions consisting of particles with average sizes of 0.5 × 10⁵, 380, 30, and 15 nm were obtained and their electrical conductivity ($\sigma$), thermo-e.m.f. ($\alpha$), Hall (R_H), and thermal conductivity ($\chi$) coefficients in the temperature range ∼77–300 K and magnetic field strength (H) up to ∼74 × 10⁴ A/m have been investigated. With decreasing powder sizes in the samples an increase in $\sigma$ and a decrease in phonon thermal conductivity (${\chi }_l^{}$) and $\alpha ,$ R_H are observed; the dependences of these parameters of the samples on the size of the powders satisfactorily correlate in the studied temperature range. As the size of the crystals decreases, the concentration of the boundaries increases, this leads to increase of electron concentration in the samples. Effect of H on the electrical and thermal properties for annealed samples of Bi₈₅Sb₁₅ solid solutions was stronger than for the samples that have not undergone annealing.

Keywords:

• Annealing
• electrical conductivity
• extrusion
• grains
• texture