High-temperature thermoelectric characterization of filled strontium barium niobates: Power factors and carrier concentrations

Thermoelectric properties of oxygen-deficient filled strontium barium niobates (SBN, Sr xBa6-xNb10O30-δ) in the composition range from the barium end member to a Sr:Ba ratio of 80:20 were investigated. The electrical conductivity, Seebeck coefficients, and power factors for ceramic samples annealed at 1300-1310 °C for 30 h under forming gas (∼10^-16 pO2 atm) were evaluated from ∼350 to 970 K. The conduction mechanism in the filled SBNs was found to be similar to that of the heavily-reduced unfilled SBNs reported in literature. However, relative to the unfilled counterparts heat-treated at 10^-16 atm pO2, larger power factors were observed in the filled SBNs. The thermoelectric performance of these filled SBNs was composition-sensitive; lower Sr contents showed higher electrical conductivities, and power factors. Electron diffraction and Hall experiments suggest that both mobility and carrier concentration are enhanced with decreasing Sr. For ceramic samples, the highest power factors achievable were found for low Sr, heavily-reduced filled compositions.