Trirutile structure

Unit cells of the rutile and the trirutile structures. The positions of the twofold rotation axes have been included... 

In some circumstances the magnitudes of the translation vectors must be taken into account. Let us demonstrate this with the example of the trirutile structure. If we triplicate the unit cell of rutile in the c direction, we can occupy the metal atom positions with two kinds of metals in a ratio of 1 2, such as is shown in Fig. 3.10. This structure type is known for several oxides and fluorides, e.g. ZnSb20g. Both the rutile and tlie trirutile structure belong to the same space-group type PAjmnm. Due to the triplicated translation vector in the c direction, the density of the symmetry elements in trirutile is less than in rutile. The total number of symmetry operations (including the translations) is reduced to... 

Cr2NbOsF M1CrM204 Nb02F + Cr203 at 900°C X. trirutile structure i... 

The structure and distorted variants of it are also found for a number of mixed transition metal oxides. In the trirutile structure, the tetragonal c axis of the simple unit cell is tripled and the titanium sites are no longer equivalent. The mineral tapiolite, FeTa206, has this structure in which the Fe and Ta occupy separate crystallographic positions. The ferrous ion can be replaced by Mg+ and other divalent transition metal cations such as Co+ and Ni+. Antimonates of the form MSb206 (M+ = Mg, Fe, Co, Ni, Zn) also form with the trirutile structure. Examples are known in which the transition metals are mixed on the two sites. This occurs for WCr206, which might more correctly be formulated Cr(Cro.5 Wo.5)206. 

The cryochemical method is also rather useful for the preparation of various metastable compounds. Thus thermal decomposition of freeze-dried oxalate complexes resulted in the formation of metastable monoclinic CuNb20g and CuTa20g with trirutile structure. An unusual polymorph of FeOOH—akageneite—was found during analysis of freeze-dried hydrated ferric oxides obtained from different precursors under various precipitation conditions. Soft oxidation of... 

M Sb20fi. Three types of structure have been found for these compounds. The small ions of Mg and certain 3d metals form the trirutile structure (p. 203), sometimes described as the tapiolite structure, after the mineral of that name, FeTa20fi. Compounds with this structure include ... 

The MCr206 (M = Te, W) oxides show an ordered trirutile structure, first reported by Bayer [61] with space group P42/mnm. This structrure can be described as (Cr2O10)14- species built up from two octahedra sharing an edge ... 

Fig. 22. Trirutile structure of MCr206 (M = Te, W) exhibiting the stacking of Cr(III) ions...

Fe2TeOe has the trirutile structure and is a collinear antiferromagnet. Mdss-bauer spectra indicate a Neel temperature of 218 K, the saturation magnetic field at the Fe + site being 520 kG. The principal axis of the electric field gradient is perpendicular to the spin axis [173]. An independent measurement of the Neel temperature gives 201 K [174]. 

Cr,WO 250--180 -196 Gouy trirutile structure sign of 0p uncertain antiferromagnetic with 0 = 69 K 66M17, Fig. 90... 

Fe TeOg 550---77 Farad trirutile structure sharp peak at 201 K evidently due to the onset of 68D3, Fig. 204... 

Crai) [A] (3dr Simple compounds With oxygen TajCrOg room 4.7 trirutile structure, 69B34... 

---