Bixbyite structure

Mixed (Fe,Mn)203-bixbyite structure, black (Fe.Mn)203-corundum structure, brown ... 

The bixbyite structure of e.g. SC2O3 represents a solution to the problem of filling three quarters of the tetrahedral sites of cubic close-packed Sc with O. It is not the simplest solution that would be the structure obtained by filling the tetrahedral sites not filled in CU2O (i.e. the pyrochlore structure of AgSb03, with Ag, Sb replaced by Sc, cf. Sect. 2.1.1.3). With normal Sc-O bond lengths that structure would have short O... O distances, and so an alternative structure that allows adjustment of the O... O and M... M distances is adopted. 

In the bixbyite structure (C form) the six-coordinated oxygen atoms are of two arrangements and the oxygen positions are sufficiently irregular to suggest anion vacancies. In the intermediate oxides the structures may be considered to... 

The pyrolysis of VF3 in water-ammonia vapour affords V2O2.70N0 15F0, 5 which has the bixbyite structure. 

At high pressures (34CiPa), UN transforms from cubic rock salt structure [256]) to hexagonal symmetry. At 10 MPa, IJN, is known to form with the fluorite structure Ut = 5.31 A) [257]. UjN, has the bixbyite structure [257]. UN is paramagnetic with a susceptibility maximum at 53 K. The higher nitrides are nonstoichiometric and have antiferromagnetic ordering temperatures from 94 K to 8 K (UN,.55 to UN,., ) [258],... 

Table 3. Structural data for nitrides with the bixbyite structure...

This compound can take two crystallographic structures, bixbyite and perovskite. In the bixbyite structure the lathanum and the yttrium anions are both placed in a mean el t-fold oxygen environment and in perovskite structure the lanthanum cation is strictly placed in a 12-fold oxygen environment and thus yttrium in a 6-fold environment. For a low temperature process we reach firstly the bixbyite structure and the perovskite... 

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