Niobates layered oxides

Group (IV) metal phosphates and phosphonates, transition metal oxides (titanates, silicates, niobates, etc.), layered oxides, and double hydroxides (aluminum, magnesium, iron, etc.) are some of the inorganic compounds used as layered host ma-... 

Inorganic layered oxides have attracted considerable attention due to their unique structural properties and applications, such as in intercalation reactions, ionic exchange processes, photochemical and semiconductor properties, and catalytic applications. In this chapter, titanates, niobates, tungstates, molybdates, and molybdenum oxide will be considered as specific examples. However, it is necessary to say that many other specific lamellar oxides are investigated, such as V2O5. 

There is often a wide range of crystalline soHd solubiUty between end-member compositions. Additionally the ferroelectric and antiferroelectric Curie temperatures and consequent properties appear to mutate continuously with fractional cation substitution. Thus the perovskite system has a variety of extremely usehil properties. Other oxygen octahedra stmcture ferroelectrics such as lithium niobate [12031 -63-9] LiNbO, lithium tantalate [12031 -66-2] LiTaO, the tungsten bron2e stmctures, bismuth oxide layer stmctures, pyrochlore stmctures, and order—disorder-type ferroelectrics are well discussed elsewhere (4,12,22,23). 

Niobium is always covered with an oxide layer. In aqueous solutions only some niobium compounds are soluble, mostly in the form niobate anions, for example, [H ,Nb60i9]( -- >-. 

Corresponding niobates also exist as discussed below. Noble metal co-catalysts (e.g., Pt) are loaded onto these photocatalysts by photocatalytic deposition from PPPtCk (see above). Since the oxide sheets have a net negative charge (that is balanced by the alkali cations), the PtCk2" anions are not intercalated in the host lattice.95 Instead, the Pt sites are formed on the external surfaces of the layered perovs-kite powder. 

Layered metal oxides(e.g. layered titanates, titanoniobates and niobates) intercalated with organic compounds have been extensively studied because of their potential applications in sorption, catalysis and conduction[1-3]. However, there are few studies on the preparation of inorganic oxide-pillared layered metal oxides, which have higher thermal stability than those layered metal oxides prepared by the intercalation of organic compounds[4-6]. He have reported that layered niobate and titanoniobate can react with NH2(CH2)3Si(OC2H3) 3 (abbreviated hereafter as APS) aqueous solution to obtain porous, thermostable silica-pillared layered metal oxides[7,8]. APS is a trialkoxysilane compound, its trialkoxy groups quickly undergo... 

In the development of transition metal oxide photocatalyts, a target has been placed on the macrostructural effects in an attempt to improve the photocatalytic activity. Layer structure A4NbgOi7 (A = K, Rb) consisting of macropolyanion sheets of niobates (NgOj ) has anisotropy along the stacking direction and... 

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