Geometrical analysis of superstructures in YBaCo4O8.5 by electron diffraction

Abstract Two kinds of superlattice reflections from oxygenated YBaCo 4 O 7 + δ phase are investigated based on the electron diffraction. In light of the method of the Niggli reduced cell, corresponding superstructures are determined to be a hexagonal lattice with parameters of a A  = 10.90(4) A and c A  = 10.02(6) A and an orthorhombic lattice with parameters of a B  = 18.90(4) A, b B  = 10.90(5) A and c B  = 10.05(0)A, respectively. With respect to their respective parent hexagonal structure, the two superstructures are determined to be 3 × 3 × 1 structure and 3 × 3 × 1 structure. In addition, the origin of superlattice reflections is also discussed. The study advances our understanding of structural property, the extraordinary oxygen ordering and the oxygen diffusion process in YBaCo 4 O 7 + δ .