Determination structurale des fluorozirconates de thallium trivalent

• Published in: Materials research bulletin 1994, Vol.29 (4), p.405-415
• Main Authors: Gervais, J.F., Fournes, L., Grannec, J., Gravereau, P., Laval, J.P., Hagenmuller, P.
• Format: Article
• Language: fre
• Subjects: Chemical Sciences; Engineering Sciences; Material chemistry; Materials
• ISSN: 0025-5408; 1873-4227
• DOI: 10.1016/0025-5408(94)90073-6

In the TlF 3-ZrF 4 system, two phases have been detected : a cubic one formulated Tl 0.67Zr 0.33F 3.33 and crystallizing with the Pm3̄m space group ( a=4.061(1) A ̊ ) and a rhombohedral one, TlZr 3F 15 (R3̄c space group with a=12.196(1) A ̊ , c=11.161(1) A ̊ ). The structures have been refined using the Rietveld method. The refinement converges to R I=0.038 and 0.042 for Tl 0.67Zr 0.33F 3.33 and TlZr 3F 15 respectively. The structures derive from the ReO 3-type by anionic insertion. In Tl 0.67Zr 0.33F 3.33 this mechanism involves two anion positions : one, F1, is slightly shifted from the ideal ReO 3 anionic site and the other, F2, is displaced further away. The anion-excess may be explained by a substitution of some F1 atoms by F2-F2 pairs. The anionic polyhedra are constituted of pentagonal bipyramids and distorted octahedra. The anion-excess in TlZr 3F 15 results from the insertion of fluorine atoms on the two opposite faces of the unit cell of the ReO 3 prototype. This structure can be described as a three-dimensional framework of cornersharing dodecahedra and distorted octahedra.