Crystal structure, oxygen nonstoichiometry and properties of novel Ruddlesden-Popper phase Sm1.8Sr1.2Fe2O7-δ

Sm1.8Sr1.2Fe2O7-δ Ruddlesden-Popper (RP) phase has been prepared using a glycerol nitrate technique at 1100 °C in air. The X-ray diffraction (XRD) pattern for the single phase Sm1.8Sr1.2Fe2O7-δ was refined by the Rietveld method within the tetragonal structure (space group P42/mnm) with unit cell parameters a = 5.489(1) Å; c = 20.019 (1) Å. The oxygen content in Sm1.8Sr1.2Fe2O7-δ at room temperature determined by TGA and iodometric titration is estimated to be 6.85 ± 0.01. Thermal expansion, electrical conductivity and Seebeck coefficient of Sm1.8Sr1.2Fe2O7-δ were measured within the temperature range of 25-1100 °C in air. Electron holes were considered as the main charge carriers.