X-Ray and TEM Studies of CdTeMoO6 and CoTeMoO6: A New Superstructure of Fluorite Type with Cation and Anion Deficiencies (■CoTeMo)(□2O6)

✍ Scribed by Y. Laligant

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 779 KB
• Volume: 160
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9254

✦ Synopsis

The crystal structures of two telluromolybdates CdTeMoO 6 and CoTeMoO 6 have been solved ab initio. CdTeMoO 6 crystallizes in a tetragonal cell (space group No. 113, P4 2 1 m, Z ‫؍‬ 2) with a ‫؍‬ 5.2840(1) A s , c ‫؍‬ 9.0595(2) A s whereas CoTeMoO 6 crystallizes in orthorhombic space group P2 1 2 1 2 (No. 18) with two formula units in the unit cell of dimensions a ‫؍‬ 5.2545(1) A s , b ‫؍‬ 5.0653(1) A s , and c ‫؍‬ 8.8589(2) A s . The X-ray powder di4raction pattern data were re5ned by the Rietveld pro5le technique and led respectively to R Bragg ‫؍‬ 0.07 for CdTeMoO 6 and R Bragg ‫؍‬ 0.07 for CoTeMoO 6 . The crystal structure of CdTeMoO 6 is built up from corner-sharing distorted CdO 4 tetrahedra which build a layer in the a,b plane, while in CoTeMoO 6 cobalt atoms exhibited an octahedral distorted surrounding. Both compounds are simultaneously cation-and anion-de5cient 1.1.2 superstructures of 6uorite in which the electron lone pairs of tellurium are stereo-chemically active. High-resolution electron microscopy images of CdTeMoO 6 showed well-ordered crystals fragments, but in some crystals defects have also been detected.