Iron tantalates

Iron Tantalates.—The meta-salt, Fe0.Ta206, has been obtained more or less pure by fusing tantalum pentoxide and ferrous fluoride with excess of potassium chloride.8 Iron tantalates occur naturally in niobites and tantaMtes. The ore tapiolite has the approximate composition FeO.Ta2Os the tantalum may be partially substituted by niobium.9... 

The analysis of ferrotantalum alloys and of tantalum steels also involves the conversion of the tantalum present into the pentoxide. The material is dissolved in hydrofluoric add and nitric acid, evaporated to dryness, and the residue fused with potassium hydrogen sulphate extraction with dilute hydrochloric acid and hydrolysis yield a predpitate of hydrated tantalic pentoxide, the iron remaining in solution.7... 

Monophosphate tungsten bronzes with pentagonal tunnels NASICON = Sodium super ionic conductor NLO = Nonlinear Optical PLZT = Lead lanthanum zirconium titanate PZT = Lead zirconium titanate SBT = Strontium Bismuth Tantalate, SrBi2Ta209 SOFC = Solid oxide fuel cell TTB = Tetragonal tungsten bronze YAG = Yttrium iron garnet 3D = Three-dimensional TEOS = Tetraethylorthosilicate. 

Niobium and tantalum (both rare, 3x 10 %) are extracted (Fig. 243) from a mineral which is a mixed niobate and tantalate of iron and manganese, (Fe,Mn) (Nb,Ta,Og)2. When it contains more niobium than tantalum it is known as columbite, otherwise as tantalite. 

Potassium niobate, together with the analogous tantalate, is soluble, whereas iron and titanium remain in the insoluble residue, along with 3 to 4 per cent of the niobium. 

Following the successful synthesis of tetraisopropoxoaluminates of later 3d transition metals, the chemistry of their niobate, tantalate and zirconate derivatives has also been extensively investigated since 1985 niobate/tantalate, M(01V)g derivatives of Mn(n), ° chromium, iron, " cobalt, nickel,copper,and zirconate, Zr2(OI )9 derivatives of iron, cobalt, nickel and copper (Eqs 3.44 and 3.45) ... 

The IR and Raman spectra of lithium triborate glasses doped with Nb205 contained characteristic features of NbOe units. The IR spectra of oxide materials (Mn,Fe)(Nb,Ta)206 gave assignments to Nb/Ta-Oe and Fe/Mn-Oe octa-hedra. Raman spectroscopy was used to monitor the M (= Nb or Ta) environments in phosphoniobate and -tantalate glasses doped with iron. ... 

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