High-resolution transmission electron microscopy study of Ca3CO4O9

The crystal structure of Ca3Co4O9 was investigated using high-rcsolution transmission electron microscopy (HRTEM) and the image- simulation method. The c* was 10.8Angstrom and the b parameters were 4.56Angstrom for the Ca2CoO3 block and 2.82Angstrom for the CoO2 sheet. The [110] zone axis HRTEM images confirmed that Ca3Co4O9 has a modulated layered structure with modulation. For the first time, the atomic positions of the Ca and Co atoms in the Ca2CoO3 block were identified, corresponding to three rows of dark spots in the [110] direction. The observed HRTEM images for Ca2CoO(3) agreed well with the calculated images based on the structural model obtained by the Rietveld refinement method.