Bi 1 − x Sr x CuSeO oxyselenides as promising thermoelectric materials

$p$ -type BiCuSeO, a layered oxyselenide composed of conductive ${\left({\text{Cu}}_2{\text{Se}}_2\right)}^{2-}$ layers alternately stacked with insulating ${\left({\text{Bi}}_2{\text{O}}_2\right)}^{2+}$ layers, shows an enhancement of the electrical conductivity after substituting ${\text{Bi}}^{3+}$ by ${\text{Sr}}^{2+}$ , from $470\text{S}{\text{m}}^{-1}$ (BiCuSeO) to $4.8\times {10}^4\text{S}{\text{m}}^{-1}$ $\left({\text{Bi}}_{0.85}{\text{Sr}}_{0.15}\text{CuSeO}\right)$ at 293 K. Coupled to high Seebeck coefficients, this leads to promising values of the thermoelectric power factor that exceeds $500\mu \text{W}{\text{m}}^{-1}{\text{K}}^{-2}$ at 873 K. Moreover, the thermal conductivity of these layered compounds is lower than $1\text{W}{\text{m}}^{-1}{\text{K}}^{-1}$ at 873 K. Maximum $ZT$ values reach 0.76 at 873 K, making this family promising for thermoelectric applications in the medium temperature range.