Electron microscopy and electron energy-loss spectroscopy study of Nd 1-x Sr x CoO 3-δ (0 ≤ x ≤ 1) system

A solid solution of Nd1−xSrxCoO3−δ (with x=0, 1/3, 2/3, and 1) has been prepared and characterized by a combination of X-ray diffraction, electron microscopy, and electron energy-loss spectroscopy (EELS). The structural characterization indicates that Nd-doped materials present an orthorhombic symmetry with a=√2xap, b=√2xap, and c=2xap (ap refers to lattice parameter of simple cubic perovskite), while SrCoO2.5 has an orthorhombic symmetry with a=√2xap, b=4xap, and c=√2xap. EELS analysis revealed that Co are in 3+ oxidation states but in different spin configurations.