HIGH-RESOLUTION ELECTRON-MICROSCOPY ON YT TRIUM IODIDE CARBIDE OXIDES

An investigation on the real structure of the yttrium iodide carbide o xides has been carried out by means of HRTEM. In the structures planar layer fragments with the general composition Y2I2C are linked via cha ins of corner sharing Y4O tetrahedra building corrugated layers. A seq uence of compounds with the general formula (Y2I2C)(n)YO can be derive d where n denotes the number of linked octahedra chains in the plane s ections, and thus represents their width. Irregularities concerning th e width of the planar segments have been detected. Besides the so far known members of the series Y7I6C3O und Y9I8C4O, With n=3 and 4, respe ctively, an additional ordered compound with alternating 3 and 4 octah edra chains has been found. The introduction of the samples, which are very sensitive to air and moisture, into the microscope has been real ised using a specially designed transfer system.