Lead iron tungstate

There are a whole range of lead-containing relaxors based on lead zinc niobate (PZN), lead iron niobate (PFN), lead iron tungstate (PFW), and solid solutions with each other and with BaTiOs (BT), PbTi03 (PT), and SrTiOs (ST). Some of the solid-solution phases are PMN-PT, PMN-PT-PZN, PMN-PZN, PFN-PFW, PFN-PMN, and PFW-PT. 

Lead iron tungstate (PFW) PbFeWO 183 20,000 Multilayered capacitors... 

PFW. Lead iron tungstate (from the chemical symbols Pb, Fe, W). pH. Symbol for the acidity or alkalinity of a solution it is a number equivalent to the logarithm, to the base 10, of the reciprocal of the concentration of hydrogen ions in an aqueous solution. The point of neutrality is pH7 a solution with a pH below 7 is acid, above 7 is alkaline. The pH of a casting slip is of practical importance in determining its rheological properties. 

T. C. Reiley et al., A Low Temperature Firing Thick Film Capacitor Material Based on Lead Iron Niobate Tungstate, Matl. Res. Bull., vol. 19, no. 12, pp. 1543-1549,1984. 

H. 8-Hydroxyquinaldine (XI). The reactions of 8-hydroxyquinaldine are, in general, similar to 8-hydroxyquinoline described under (C) above, but unlike the latter it does not produce an insoluble complex with aluminium. In acetic acid-acetate solution precipitates are formed with bismuth, cadmium, copper, iron(II) and iron(III), chromium, manganese, nickel, silver, zinc, titanium (Ti02 + ), molybdate, tungstate, and vanadate. The same ions are precipitated in ammoniacal solution with the exception of molybdate, tungstate, and vanadate, but with the addition of lead, calcium, strontium, and magnesium aluminium is not precipitated, but tartrate must be added to prevent the separation of aluminium hydroxide. 

Many heavy metals react with dithiol to give coloured precipitates, e.g. bismuth, iron(III), copper, nickel, cobalt, silver, mercury, lead, cadmium, arsenic, etc. molybdate and tungstate also react. Of the various interfering elements, only arsenic distils over with the tin when a mixture is distilled from a medium of concentrated sulphuric acid and concentrated hydrobromic acid in a current of carbon dioxide. If arsenic is present in quantities larger than that of the tin it should be removed. 

Although flotation was developed as a separation process for mineral processing and applies lo the sulfides of copper, lead, zinc, iron-molybdenum, cobalt, nickel, and arsenic and to nonsullides, such as phosphates, sodium chloride, potassium chloride, iron oxides, limestone, feldspar, fluorite, chromite, tungstates, silica, coal, and rhodochrosilc, flotation also applies to nonmineral separations. Flotation is used in the water disposal field, particularly in connection with petroleum waste water cleanup. 

Lead-based inhibitors and zinc phosphate inhibitors are thought to plug up the discontinuities in the natural oxide layer and hence offer protection. This is akin to the repair of an imperfect oxide film of iron by chromates, molybdates or tungstates. 

Tkachenko et al reported that compacts in iron, copper, nickel or cobalt matrices had operating temperature limits between 200 and 600 C, but compacts in molybdenum gave satisfactory friction and wear to 900 C in vacuum. A satisfactory composite for high-temperature aircraft brakes was described as containing 25% molybdenum disulphide, alumina and lead tungstate in a nickel matrix . The composites were pressed at 880 to 1080 MPa and sintered at 1010 C for two hours in vacuum. 

The carbonates, sulphates, and borates are decomposed. The sulphides of the alkalies and alkaline earths are decomposed while the sulphides of arsenic, antimony, molybdenum, zinc, cadmium, tin, iron, lead, copper, mercury, and palladium are not attacked. Cobalt sulphate is not attacked, while the sulphates of the alkalies and alkaline earths are attacked and dissolved. Alkali tungstates, ammonium arsenite and arsenate, copper arsenite, ammonium magnesium arsenate, ammonium molybdate and vanadate, potassium cyanide and ferrocyanide are decomposed. Paraffin is not attacked shellac, gum arabic, gum tragacanth, copal, etc., are decomposed. Celluloid is slowly attacked. Silk paper, gun cotton, gelatin, parchment are dissolved. M. Meslans 22 has studied the esterification of alcohol by hydrofluoric acid. 

In addition to the above, preparation in w/o microemulsions of nanoparticles of various other types of compounds, viz. silica-coated iron oxide, Fe203-Ag nanocomposite, oxides of ytrium, erbium, neodymium, vanadium and cobalt, titanates of barium and lead, ferrites of barium, strontium, manganese, cobalt and zinc, oxide superconductors, aluminates, zirconium silicate, barium tungstate, phosphates of calcium, aluminium and zinc, carbonates of calcium and barium, sulphides of molybdenum and sodium, selenides of cadmium and silver etc. have been reported. Preparative sources and related elaboration can be found in [24]. 

With the exception of the lead oxide the metal oxides used are very interesting materials with respect to catalytic applications. Tungstates and molybdates are widely used in partial oxidation reaction [6], iron oxides are the basis of many important industrial cat ysts, which are for instance, used for the dehydrogenatitm of ethyl benzene to styrene. If the surfactant template could be removed from the structures, very high surface area catalysts could be accessible. 

Vauquelin investigated cerium compounds and prepared metallic cerium, tungstates, and meteorites, which Edward Howard found to consist mainly of iron and nickel. Vauquelin showed that the minerals rutile and anatase are two varieties of titanium oxide, prepared fairly pure lead dioxide by boiling red-lead with dilute nitric acid, and determined the composition of carbon disulphide by passing the vapour over red-hot copper. ... 

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