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Copper containing oxides hold a widespread research interest in inorganic fields due to the fascinating electronic and magnetic properties the compounds exhibit. In the Cu-Sb-O ternary system, CuSb2O6 is the most intensively studied compound [1], owing to its unusual structural and magnetic behaviour. Jahn-Teller distortions from the Cu2+ cause an axial elongation of the Cu-O octahedra to give rise to a monoclinic structure (s.g. P21/n) [2]. At high temperatures, this material undergoes a second order phase transition to the tetragonal phase (s.g. P42/mnm), isostructural to room temperature structures of CoSb2O6 and NiSb2O6 [3]. This modification may only be possible through an intermediate orthorhombic modification in Pnma as defined through systematic symmetry reduction[4]. Through the doping of CuSb2O6 with Co and Ni, this structural transition can be investigated.
Neutron, lab X-ray and synchrotron single crystal and powder diffraction have been used to study phase transitions in both solid state solutions. In the Cu1−xCoxSb2O6 system, it was found that two phases exist between compositions x = 0.2 and 0.5, with a Cu-rich monoclinic phase and a Co-rich tetragonal phase. The magnetic susceptibility for all compounds match closely to CoSb2O6, even at low doping levels. This indicates a change from the 1D magnetic behaviour of CuSb2O6 to 2D. By contrast, the Cu1−xNixSb2O6 system exhibits a single phase region from x = 0.4, where only the tetragonal phase remains. This has been attributed to a reduction of Cu2+ due to the high temperatures used in synthesising these compounds.
[1] Giere O -E, Brahimi A, Deiseroth H J and Reinen D (1997) J. Solid State Chem. 131, 263
[2] Prokofiev A V, Ritter F, Assmus W, Gibson B J and Kremer R K (2003) J. Cryst. Growth. 247, 457
[3] Nikulin, AY, Zvereva EA, Nalbandyan VB, et al., Dalton Trans (2017), 46, 6059
[4] Bärnighausen H 1980 MATCH, Commun. Math. Chem. 9, 139
| Topic | Chemistry |
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