Ammonium niobates

Niobates are usually insoluble in water even many of the alkali niobates are insoluble. Insoluble alkali niobates are formed when niobium pentoxide is fused with only small proportions of alkali carbonate. 7 6 Sodium niobate, 7Na20.6Nb205. H20, is insoluble in solutions of high sodium-ion concentration, and is therefore precipitated. by the addition of sodium salts to solutions of potassium niobate. Ammonium niobates are unknown when excess of an ammonium salt is added to a solution of an alkali niobate, a voluminous precipitate is thrown down which is rapidly decomposed by water to yield niobic 1 Larsson, Zeitsck. anorg. Ch m., 1896,12,197. 

Decomposition of lithium niobate, LiNb03, by molten ammonium hydrofluoride can be performed even at temperatures as low as 130-260°C [122]. The process also enables the separation of niobium and lithium, yielding ammonium oxyfluoroniobate and lithium fluoride. The interaction can be represented by Equation (132) ... 

It can be prepared by heating metallic niobium or any of the lower oxides, or the sulphide, carbide, or nitride of niobium, in air or oxygen. Ammonium niobium oxyfluoride, (NH4)jNbOFs, also yields the pentoxide on being heated in air. Solutions of the alkali niobates yield a white gel of the hydrated pentoxide when treated with mineral adds, sulphuric acid bring usually preferred. Insoluble niobates on fusion... 

After being strongly ignited, niobium pentoxide becomes insoluble in all acids other than hydrofluoric acid, but is dissolved by molten potassium hydrogen sulphate, ammonium hydrogen sulphate, and borax. It is also insoluble in solutions of alkalis, but is converted into the alkali niobates by fusion with alkali hydroxides and carbonates. 

A large number of inorganic layer crystals such as micas, sodium silicates, niobate, uranate, vanadate, titanate, zirconium phosphate, graphitic acids, crystalline silicic acids, vanadium oxyhydrate, calcium phosphoric acid esters, and titanium disulfide develop alkyl crystals between their rigid crystal layers by ion exchange with, for example, alkyl ammonium salts and by intercalation inorganic... 

An aqueous precursorfor 0.75Pb(Zni/3- Nb2/3)O3-0.25BaTiOs solid solution was synthesized by Van Werde et al. (2001). They used acetates of lead and zinc, and Nb(V) peroxocitrato complex. The solution of lead zincate niobate was prepared by adding the compounds into aqueous solution of ammonium citrate. The aqueous solution was stable when pH was higher than 8 and the citrate acid/cation mole ratio was higher than 1.5. The aqueous precursor for barium titanate was prepared by using titanium(IV) peroxocitrato complex and barium acetate. They found that the solid solution of PZN and BT is crystallized as a perovskite phase at temperatures as low as 800°C. 

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