Pseudobrookite structure

In this structure there is octahedral coordination of the B ions, but the coordination of A is unusual. It can be described either as a highly deformed octahedron or as a distorted tetrahedron, for in Fe2Ti05 Fe has four neighbours at a mean Fe-0 distance of 1-92 A and two more at 2-30 A. Ti has six octahedral neighbours as in the forms of Ti02, FeTi03, Al2TiOs also has the pseudobrookite structure for TisOs see p. 466. 

Another example lies in the development of cordierite, a desirable and stable refractory, low-thermal-expansion crystal in the Si02—AI2O3—MgO system. Here a reaction occurs between metastable phases, spinel, a-quartz, and the nucleating titanate (pseudobrookite structure) to produce cordierite and rutile as follows ... 

Titanate Pigments Colored Rutile, Priderite, and Pseudobrookite Structured Pigments... 

I 6 Titanate Pigments Colored Rutile, Priderite, and Pseudobrookite Structured Pigments Table 6.6 Lattice parameter changes (vs. pureTiOj) in DR pigments. 

In their study of spinels, Navrotsky and Kleppa (1967b, 1968) paid particular attention to the variation of the distribution of cations between octahedral and tetrahedral sites. They observed a change in enthalpy of solution upon heating a natural MgAl20i spinel and proposed a simple model to describe the thermodynamics of disordering. Navrotsky (1975) has applied a similar model to compounds having the pseudobrookite structure. An important consequence of massive cation disorder is the stabilization of such... 

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