Tungsten trioxide

In a technical scale, WO3 is almost exclusively produced by calcination of APT under oxidizing conditions (in air). Usual equipment consists of rotary furnaces operating at 500-700 °C. Sufficient air supply must be provided to suppress any reducing reaction by the partly cracked ammonia. The ammonia evolved can be recovered by absorption in cold water and concentrated by subsequent distillation. 

Low-temperature calcined WO3 (approximately 500-550 °C) [5.55] is highly reactive and dissolves easily in water, which is not the case for higher-temperature calcined WO3. 

For special purposes, especially in the case where a high specific surface area is necessary and APT pseudomorphology is undesirable, WO3 can be produced also by calcination of tungstic acid. 

As precursor for the W and WC powder production, WO3 lost its importance mainly to tungsten blue oxide. WO3 is also used as a yellow pigment. 

---

Tungsten oxytetrachlofide [13520-78-0], WOCl, mp 211°C, bp 221°(Z, is a red crystalline soHd. It is soluble in carbon disulfide and ben2ene and is decomposed to tungstic acid by water. It may be prepared by refluxing sulfurous oxychloride, SOCI2, on tungsten trioxide (12) and purified after evaporation by sublimation. 

Tungsten oxydiiodide [14447-89-3] WO2I2, is prepared by heating a mixture of tungsten and tungsten trioxide with excess iodine in a 500—700°C temperature gradient for 36 h (20,21). 

Tungsten trioxide [1314-35-8] is a yellow powder. However, the smallest diminution of oxygen brings about a change in color. Tungsten... 

Anhydrous sodium tungstate, Na2W04, is prepared by fusing tungsten trioxide in the proper proportion with sodium hydroxide or sodium carbonate ... 

Orally in rats, the toxicity of sodium tungstate was highest, tungsten trioxide was intermediate, and ammonium tungstate [15855-70-6] lowest (59,60). In view of the degree of systemic toxicity of soluble compounds of tungsten, a threshold limit of 1 mg of tungsten per m of air is recommended. 

Members of the ion-insertion/extraction group, as inorganic or organic thin films, especially the former, have attracted the widest interest most recently. Tungsten trioxide was the eadiest exploited inorganic compound (4), even before the mechanism of its electrochromic response was understood (5). It is stiU the best known of the important ion-insertion/extraction group. 

Metal Oxides Tungsten trioxide, undoubtedly the most widely studied electrochromic material, is used in several types of commercial electrochromic devices. 

Aluminium oxide, arsenic trioxide, bismuth trioxide, calcium oxide, chromic oxide, lanthanum oxide, lead dioxide, magnesium oxide, manganese dioxide, molybdenum trioxide, phosphorus pentoxide, stannic oxide, sulfur dioxide (explodes), tantalum pentoxide, tungsten trioxide, vanadium pentoxide. 

Lithium is used to reduce metallic oxides in metallurgical operations, and the reactions, after initiation at moderate temperatures, are violently exothermic and rapid. Chromium(III) oxide reacts at 185°C, reaching 965° similarly molybdenum trioxide (180 to 1400°), niobium pentoxide (320 to 490°), titanium dioxide (200-400 to 1400°), tungsten trioxide (200 to 1030°), vanadium pentoxide (394 to 768°) also iron(II) sulfide (260 to 945°), and manganese tclluridc (230 to 600°C)... 

Figure 23 Photograph of a working tandem device based on a thin film of polycrystalline tungsten trioxide...

A crystallographic shear (CS) plane is a fault in which a plane of atoms has been (notionally) removed from the crystal. In oxides, this is frequently a plane of oxygen atoms, eliminated as a result of reduction. In the resulting structures, the slab types are all identical and the same as the parent phase. To illustrate this phenomenon, crystallographic shear in reduced tungsten trioxide will be described. 

Acrylic acid, Initiator, Water, 1148 Aluminium chloride, Water, 0062 Barium peroxide, Propane, 0216 1,3-Benzodithiolium perchlorate, 2677 1,1 -Bis(fluorooxy)tetrafluoroethane, 0641 Borane-tetrahydrofuran, 0138 Boron tribromide, Water, 0122 Bromine, Aluminium, Dichloromethane, 0261 Bromine, Tungsten, Tungsten trioxide, 0261 f 1,3-Butadiene, 1480 Calcium oxide, Water, 3937 Chlorine trifluoride, Refractory materials, 3981 Chromium trioxide, Acetic acid, 4242 Copper(II) oxide, Boron, 4281 Diazoacetonitrile, 0675 Dihydroxymaleic acid, 1447 Ethyl azide, 0872... 

Tungsten trioxide, WO j, by virtue of its high melting point (1473 K) and insolubility in neutral water and concentrated mineral acids, places it well within the confines of ceramic materials. However, a large branch of inorganic chemistry opens up for W03 when it is exposed to alkali. WO3 can be dissolved in aqueous sodium hydroxide solution to produce sodium tungstate, Na2W04 ... 

B. Scheffer, I.I. Heijeinga, and J.A. MouUjn, An electron spectroscopy and X-ray diffraction study of nickel oxide/alumina and nickel oxide/tungsten trioxide/alumina catalysts, J. Phys. Chem. 91, 4752 759 (1987). 

Figure 8.1 Beer s law-type plot of change in optical absorbance against charge density q for the cell WO3 polymer electrolyte Prussian Blue. Reprinted from Inaba, H Iwaka, M., Nakase, K., Yasukawa, H., Seo, I. and Oyama, N., Electrochromic display device of tungsten trioxide and Prussian Blue films using polymer gel electrolyte of methacrylate , Electrochim. Acta, 40, 227-232 (1995), Copyright 1995, with permission from Elsevier Science.

Calculate the extinction coefficient e of the tungsten trioxide bronze , H WOs, formed if a charge of 1F is passed through H0WO3 to increase the optical absorbance by 0.52 AD, taking / = 0.01 cm and n = 1. (Hint-take the concentration of bronze from the charge passed, i.e. the concentration of bronze within the WO3 host is X.)... 

Figure 8.14 Huggins analysis of a Warburg element in a Nyquist plot such as that shown in Figure 8.12(a), for the diffusion of Li" ions through solid-state WO3. The traces for Z and Z" against will not be parallel for features other than that of the Warburg. From Ho, C., Raistrick, I. D. and Huggins, R. A., Application of AC techniques to the study of lithium diffusion in tungsten trioxide thin films , J. Electrochem. Soc., 127, 343-350 (1980). Reproduced by permission of The Electrochemical Society, Inc.

---