Thermoelectric properties of BiBO₃-added Bi₂Sr₂Co₂O_y ceramics

Abstract

The thermoelectric properties of BiBO₃-added Bi₂Sr₂Co₂O_y ceramics have been investigated. Bi₂Sr₂Co₂O_y + x wt % BiBO₃ materials (x = 0, 0.16, 0.50, and 0.80) were prepared by the sol–gel method. The values of power factor (PF) and figure of merit (ZT) were evaluated using electrical resistivity (ρ), Seebeck coefficient (S) and thermal conductivity (k) measurements. The Bi₂Sr₂Co₂O_y + 0.16 wt % BiBO₃ sample has the lowest ρ among all studied materials. The S rises with a rising temperature above 400 K, indicating p-type conductivity for each sample. The value of S for the reference (pristine) Bi₂Sr₂Co₂O_y at 973 K is approximately 3–10 % higher than the BiBO₃-added compositions. Reference and 0.16 wt % BiBO₃-added samples exhibit higher PF values than those with higher BiBO₃ content (x = 0.50 and 0.80). Adding bismuth borate (x > 0.16) leads to a 1.6-fold decrease in the thermal conductivity of the Bi₂Sr₂Co₂O_y system at 573 K. The decrease of ρ (x = 0.16) and k (for all BiBO₃-added compositions) resulted in a 39 % improvement in the ZT value.