The effects of Si doping on the thermoelectric and magnetic properties of Ca_0.98Bi_0.02Mn_1-xSi_xO _3-δ with x = 0.00, 0.02 and 0.03

Ca_0.98Bi_0.02Mn_1-xSi_xO _3-δ (x = 0.00, 0.02 and 0.03) samples are prepared by solid state reaction. All the samples are single phase with an orthorhombic structure. A metal-like behavior is observed for x = 0.00, and it switches to nonmetal-like behavior for x = 0.03. Co-substituting bismuth for calcium and silicon for manganese could modify the electronic states and hence the transport properties. The thermopower of all the samples is negative, indicating that the predominant carriers are electrons over the entire temperature range. The electrical resistivity, thermopower increase and thermal conductivity decreases with increasing Si content. Among the samples, Ca_0.98Bi _0.02Mn_0.98Si_0.02O_3-δ exhibits the highest dimensionless figure of merit (0.045), which is about 84% higher than that of the undoped at 540 K. Magnetic moments of doped samples decrease as compared to undoped sample. The Neel temperature occurred at around 120 K for all the samples.