Percolation conduction in hybrid thermoelectric material consisting of Bi_0.88Sb_0.12 and barium ferrite particles

A hybrid material consisting of thermoelectric Bi_0.88Sb _0.12 and Ba ferrite Bi_0.88Sb_0.12(BaFe ₁₂O₁₉)_x (x = 0, 0.025, 0.04 and 0.08) was synthesized using sintering. Powder x-ray diffraction patterns and scanning electron microscopy images of the hybrid indicate that the BaFe ₁₂O₁₉ particles were well distributed in the host Bi _0.88Sb_0.12 phase. The temperature dependence of the electrical resistivity ρ of the host Bi-Sb exhibits metallic behavior. By the addition of Ba ferrite particles, the ρ at 300 K increases intensively and ρ(Τ) then behaves similarly to a semiconductor. However, it is noted that the thermoelectric power S is unchanged. Inhibition of current and heat flows by a restricted conduction path and the unchanged electromotive force generated by the Seebeck effect in the conduction path can be understood based on a site-percolation model consisting of conducting Bi-Sb and insulating Ba ferrite. The critical volume fraction p_c of this system was estimated experimentally as p_c = 0.68.