Oxides and chalcogenides

Oxides and Chalcogenides. The crystal structure, electrical and thermal properties, and applications of Zr02 have been reviewed. The absorption spectrum of the HfO molecule produced by flash discharge through HfCl4 has been recorded. An X-ray study of the Zr-S system between 1273 and 1473 K established the presence of the stoicheiometric phases ZrSj and ZrSj and a non-stoicheiometric phase y- 

Kovunova, Coordination Compounds of Zirconium and Hafnium with Organic Ligands , Shtiintsa, Kishinev, Mold. S.S.S.R., 1975 Chem. Abs 1976,84,115384). 

ZrSi 0-1.8- Thermodynamic data have been obtained for The dissocia- 

Oxides and Chalcogenides. The equilibrium constants of the exchange reaction 

Intercalation of alkali-metal atoms into zirconium disulphide has been reviewed.254 Only alternate layers of vacant sites are occupied by alkali-metal atoms when ZrS2 is treated with a dilute solution of alkali metal in liquid ammonia.255 At higher con- 

Furuseth, L. Brattas, and A. Kjekshus, Acta Chem. Scand., 1973, 27, 2367. 

Leblanc-Soreau, M. Danot, L. Trichet, and J. Rouxel, Mater. Res. Bull., 1972, 9, 191. 

Oxides and Chalcogenides. The crystal structure of monoclinic Zr02 has been redetermined, the results being in good agreement with those of earlier studies. HfPOjj (x = 0.91—1.09) has been synthesized by heating these elements at temperatures between 630 and 900 K. Some dissociation of the compound occurs above 700 K.  

Layer intercalation compounds of ZrSj and HfSj with NH3, N2H4, and RNHNHMe (R = H or Me) have been obtained and the corresponding layer expansions determined. The non-stoicheiometric zirconium and hafnium ditelluride phases ZrTe, (x = 1.74—1.45) and HfTei 94 have been characterized by X-ray diffraction studies. The non-stoicheiometry of the latter compound appears to be in the anion sub-lattice.  

Troyanov and V. 1. TsircTnikov, Vestnik Moskov Univ., Khim., 1973, 14, 67 Chem. Abs., 1973, 78,165605Z). 

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The compounds HgaY2X2 (Y = S, Se, Te X = Cl, Br, I) are insoluble in water, dilute acids, and cone. HCl, and they are not attacked by these solvents. Cone. HNO3 converts the sulfide chloride into the sulfide nitrate HgsSalNOsla (20, 290). With bases, rapid decomposition occurs, leading to the formation of oxide chacogenides (20), or a mixture of oxide and chalcogenide (111), a matter on which agreement has not yet been reached. 

The complete SILAR process was first described by Nicolau in 1985.1"3 Since then it has mostly been used to grow oxide and chalcogenide thin films. 

Oxide and chalcogenide films are the primary materials that have been produced by the SILAR technique. A few metal films and films of other materials have also been produced. 

Invented less than a decade ago,1 EISA has rapidly developed into a universal technique for fabrication of organized porous and patterned nanocomposite materials, ranging from metal oxides and chalcogenides to carbons, polymers, and metals.2,3 In addition to generating ordered mesoporous films, this technique may also be used to incorporate functional molecules and... 

Fig. 7.3 Electron bands for transition metal oxides and chalcogenides. M = metal, X chalcogen or oxygen. The filling of the bands is appropriate for MoSj.

Metal oxides and chalcogenides MRH Chromium trioxide 7.20/83, sodium peroxide... 

The overwhelming majority of colloidal semiconductors studied to date are metal oxides and chalcogenides with the greatest interest being shown in the chemically durable titanium dioxide. In turn, most of the research... 

Rajamathi M, Seshadri R. Oxide and chalcogenide nanoparticles from hydrothermal/ solvothermal reactions. Current Opinion in Solid State and Materials Science. 2002 6(4) 337-345. 

The band gap is characteristic of the electronic structure of the semiconductor and is defined as the energy difference (ABg) between the valence and conduction bands that is the highest energy band with all electronic levels occupied and the lowest energy band without electrons [18]. Table 19.1 shows some typical metal oxide and chalcogenide photocatalysts, together with their respective band gaps... 

Research has also focused on the study of highly reversible negative lithium insertion materials. Transition metal oxides and chalcogenides, such as M0O2, WO2, and TiS2, if combined with a metal oxide positive electrode material yield cells with low OCV values (ca. 1.5-2 V) [111]. 

Recently, Rajamathi and Seshadri [65] have reviewed the uses of solvothermal methods for the preparation of oxide and chalcogenide nanoparticles. For oxide nanoparticles, these methods can involve hydrolysis, oxidation and thermolysis, all performed under hydrothermal or solvothermal conditions. Some of the more striking examples are provided here. 

Metals, metal oxides, and chalcogenides constitute the main body of the sonochemical research. Only very few other groups of materials have been prepared by using power ultrasound. There may be two reasons for this first, the difficulty in preparing these materials and, secondly, lack of interest. However, we believe that the first reason can explain why an important material such as GaN, for example, has not been prepared sonochemically. 

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