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The disordered cubic structure of Ca7Co3Ga5O18 |
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| Authors: | J. Grins G. Svensson E.V. Antipov |
| Affiliation: | a Department of Inorganic Chemistry, Stockholm University, SE-10691 Stockholm, Sweden b Department of Chemistry, Moscow State University, 119899 Moscow, Russia c Department of Structural Chemistry, Stockholm University, SE-10691 Stockholm, Sweden d School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK |
| Abstract: | The new mixed oxide having composition close to Ca7Co3Ga5O18 was synthesized from CaCO3, Co3O4 and Ga2O3 at 1150 °C in air and studied by neutron and synchrotron X-ray powder diffraction, selected-area electron diffraction and high-resolution electron microscopy. The structure was refined, using time-of-flight (TOF) neutron powder diffraction data, in space group F432, with  and Z=8, to RF=0.7%. It is considerably disordered, with four different tetrahedral sites randomly occupied by Co and Ga atoms at a ratio of 1:2. The tetrahedra form a disordered (Co1/3Ga2/3)O2 3D-framework inside which isolated CoO6 octahedra, surrounded by 8 Ca atoms, are located. The structure is related to the ordered structure of Ca14Al10Zn6O35. Electron diffraction patterns confirmed the symmetry and unit cell and revealed no diffuse scattering. High-resolution electron microscopy images showed the absence of extended structural defects. |
| Keywords: | Ca7Co3Ga5O18 Neutron diffraction Synchrotron diffraction Electron diffraction Crystal structure |
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