Thermoelectric properties of Ca3−xEuxCo4O9+δ (0≤x≤0.1)

• The nonmetallic to metallic transition occur in the low temperature regime for all the samples.
• The total thermal conductivity decreases with increasing europium content.
• Ca2.95Eu0.05Co4O9+δ has the highest dimensionless figure of merit of 0.038 at 300 K.

Ca3−xEuxCo4O9+δ (x=0.00, 0.05 and 0.10) samples were prepared by conventional solid-state synthesis and their properties measured at 25–300 K. The x-ray diffraction (XRD) patterns revealed that all the samples are single phase. The thermopower of all the samples was positive, indicating that the predominant carriers are holes over the entire temperature range. The total thermal conductivity values decreased monotonically with increasing Eu3+ content. Ca2.95Eu0.05Co4O9+δ had the highest dimensionless figure of merit of 0.038 at 300 K, representing an improvement of about 52% compared to undoped Ca3Co4O9+δ.