Thermoelectric properties of Bi2Sr2Co2Ox polycrystalline materials

${\mathrm{Bi}}_{\mathrm{2}}{\mathrm{Sr}}_{\mathrm{2}}{\mathrm{Co}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{9}}$ (BC-2202) polycrystalline materials with a layered structure have been prepared by partial melting. The chemical compositions of the samples are ${\mathrm{Bi}}_{\mathrm{2}}{\mathrm{Sr}}_{\mathrm{2}}{\mathrm{Co}}_{\mathrm{2}}{\mathrm{O}}_x$ (2202), ${\mathrm{Bi}}_{\mathrm{1.8}}{\mathrm{Sr}}_{\mathrm{2}}{\mathrm{Co}}_{\mathrm{2}}{\mathrm{O}}_x$ (Bi-1.8), and ${\mathrm{Bi}}_{\mathrm{2}}{\mathrm{Sr}}_{\mathrm{1.8}}{\mathrm{Co}}_{\mathrm{2}}{\mathrm{O}}_x$ (Sr-1.8). All three samples are p-type conductors. The electric properties, namely, the Seebeck coefficient (S) and electric resistivity (ρ), of the samples are dependent on chemical composition. The S values increase with temperature at $\text{T>673\hspace{0.05em}}\mathrm{K}$ and, at 973 K, reach 100, 110, and 150 μV K⁻¹ for the 2202, the Bi-1.8, and the Sr-1.8 samples, respectively. Thermal conductivity (κ) for all samples is lower than for ordinary conducting oxides. The figure of merit (Z) increases with temperature for all samples. Z values at 973 K are ${\text{0.77×10}}^{\text{−4}},$ ${\text{0.61×10}}^{\text{−4}},$ and ${\text{2.0×10}}^{\text{−4}} {\mathrm{K}}^{\mathrm{-1}}$ for the 2202, Bi-1.8, and Sr-1.8 samples, respectively. The thermoelectric properties depend on the chemical composition of the BC-2202 phase. The BC-2202 material thus appears to be a promising thermoelectric material due to its high performance at high temperature (∼1000 K).