Ilmenite structures

The FeTi03, hR30, structural type (ilmenite structure) is ... 

The ilmenite structure is adopted by oxides of formula ABO3 when A and B are similar in size and their total charge adds up to +6. The structure is named after the mineral of Fe Ti" 03, and the structure is very similar to the corundum structure described... 

The ilmenite structure is found for MMnCb (M = Ni and Co), MTiC>3 (M = Mg, Mn, Ni, Co and Cd), CrRh03, FeRh03, FeV03, LiNbOs, MgGeC>3, NaSbC>3, and NaBiCb. For MM Cb compounds with large M cations the perovskite structure is encountered. 

Ilmenite structure the stmcture of the mineral FeTiOs Metathetical reaction a common type of reaction, also known as a donble decomposition reaction, in which the anions and cations of the reactants are interchanged in the prodncts (e.g. AX - - BY AY - - BX)... 

M SbOs. The salt NaSbOs may be prepared by heating NaSb(OH)g in air or by fusing Sb203 with sodium carbonate-there are similar silver and lithium salts. The sodium salt has the ilmenite structure the compound thought to be a polymorphic modification is actually Na2Sb205(OH)2 (see later). The structure ofLiSbOs is related to that of NaSb03 in the way described in Chapter 4. In both structures M and Sb each occupy one-third of the octahedral holes in a h.c.p. assembly of 0 atoms, but the choice of holes occupied is different in the two structures (p. 145). 

KSb03 is prepared by heating KSb(OH)6 and is trimorphic. One form has the ilmenite structure, and the other a cubic structure illustrated in Fig. 5.33 (p. 183). In the latter structure octahedral SbOg groups share edges and vertices, and this is also true of K3SbsOi4. There Is apparently no compound K2Sb20j. 

The ilmenite structure is common among ternary oxides of the general form ABO3 when the ions A and B are of roughly similar radii. However, if one ion B much smaller than A, and A is not too much smaller than 0, the perovskite structure (Fig. 4.17) is adopted. This comprises a ccp array of A + and O ", while occupies one-fourth of the 0-holes and... 

A few oxides with the ilmenite structure are listed in table 8.o8. It will be seen from this list that, with the exception of CdTiOs, all are oxides in which the A ion is considerably smaller than the corresponding ion in the perovskite structure. The dimorphism of CdTi03, which at high temperatures has the perovskite structure, is readily explained by the fact that the radius of the Cd2+ ion (0-97 A) is very close to the critical value for transition between the perovskite and ilmenite arrangements. Again it will be noted that the list includes a number of titanates which should more properly be described as complex oxides. 

Table 8.08. Some compounds with the ilmenite structure...

A considerable number of materials called titanates are known, some of which are of technical importance. Nearly all of them have one of the three major mixed metal oxide structures (page 54), and indeed the names of two of the structures are those of the titanium compounds that were the first found to possess them, namely, FeTi03, Hmenite, and CaTi03, perovskite. Other titanites with the ilmenite structure are MgTiOa, MnTi03, CoTi03... 

Thomas ei rj/. used multinuclear O, K, and Ti SSNMR experiments along with ah initio calculations in 2004 to study the origins of the high optical nonlinearity in KTi0P04 (KTP) [142]. The authors wanted to determine if the octahedral TiOg environment was connected to optical properties in KTP, and how these Ti environments compared to the TiOe octahedra featured in the perovskite and ilmenite structures. Single-crystal 47/49.J.- experiments were not of great utifity due to the presence... 

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