Synthesis and Crystal Structure of a New Mixed-Valence Terbium Fluoride, KTbIIITbIV2F12, and Related KLnIIIMIV2F12Compounds (MIV=Tb, Zr, Hf;LnIII=Ce–Lu)
✍ Scribed by Eric Largeau; Malika El-Ghozzi; Daniel Avignant
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 543 KB
- Volume
- 139
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
During a phase relationship study of the system KF-TbF 3 -TbF 4 , carried out using X-ray diffraction on samples synthesized under a fluorine atmosphere, a new mixed-valence terbium fluoride, KTb 3 F 12 , was brought out. Its crystal structure was determined from single-crystal X-ray diffraction data and refined to a conventional R ؍ 0.031(R w ؍ 0.057) for 920 independent reflections with F > 4 (F). It crystallizes in the tetragonal system with space group I4/m(No. 87) and unit cell parameters a ؍ 7.715(1) A s , c ؍ 7.530(1) A s , Z ؍ 2. The crystal-structure analysis revealed a perfect ordering between Tb 3؉ and Tb 4؉ cations. The structure is built of chains of edge-sharing [TbF 8 ] 4؊ dodecahedra further linked by [TbF 8 ] 5؊ cubes alternating along the [001] direction with K ؉ ions in 12-coordination. A series of homologous compounds, KLn III M IV 2 F 12 (M IV ؍ Tb, Zr, Hf; Ln ؍ Ce-Lu), was also evidenced.