Powder X-ray diffraction and Rietveld analysis of La_(1-x)Ba_xCoO_3 (0 < x ≤ 0.5)

摘要

Detailed structural properties of La_(1-x)Ba_xCoO_3 (LBCO) have been investigated by means of X-ray powder diffraction and Rietveld analysis. A structural phase transformation from R3c to Pm3m at x=0.30-0.35 has been detected based on a comparison between the refinements of R3c and Pm3m. The Co-O bond length of the CoO_6 octahedron expanded rapidly with increasing Ba content when x < 0.1, and then it leveled off and kept constant at 0.1 ≤ x ≥ =0.35, where the Co-O-Co bond angle reaches 180°. The Co-O bond length expansion resumed with increasing Ba content beyond x=0.35.