The data of experimental research of electrical conductivity and thermoelectric power of superfine powder of nonstoichiometric polyalkaline oxygen bronzes Mx'My''WO3 was established. Electrical conductivity of tungsten bronzes in thermocycles in 295-745K (vacuum) was studied. It will be observed that the bronzes after thermotreatment are semiconductors of n-type. Also the rise of electrical conductivity of powdery sodium, potassium bronzes in tens time was found. In their conditions the maximum value of electrical conductivity had bronze Na0.7WO3. Characteristic properties of mutual influence of nonstoichiometry of tungsten suboxides and chemical compositions, electrophysical properties of polyalkaline tungsten bronzes was established.
Keywords: electrical conductivity, polyalkaline oxide tungsten bronzes powder, thermoelectric power, nonstoichiometry, tungsten suboxide
Corrosion stability for 25 samples of mono- and bealkaline tungsten, molybdenum bronzes in solutions of acids HCl (20-26%), H2SO4 (21-60%), HNO3 (60%) and NaOH (20%), KOH (50%) alkalis at 293-358K and 1-15 month was studied. The samples of polycrystalline bronzes were prepared by electrolysis in melts of Li, Na, K, Rb, Cs of isopolytungstates and molybdates. General formula of bronzes chemical composition is Mx'My'EO3 with M', M'' - alkaline metals, E-W, Mo. High significance of corrosion stability of tungsten bronzes samples in water acids and alkalis was found. For molybdenum bronzes the best results in sulfuric acids and solutions were found. These differences are connected with peculiarity of crystal chemistry and nonstoichiometry of polyalkaline oxide tungsten, molybdenum bronzes.
Keywords: oxide alkaline bronze of W, Mo, corrosion stability, strong electrolyte, acid, alkali
Nonstoichiometric tungsten oxides WO3–x and oxide alkaline tungsten bronzes have been studied because of their potential applications in electrochromic devices such as solar panel arrays and “smart windows”. Different phases of
WO3–x have been considered. In this part we present results of our research which clearly show that all Magneli phases of tungsten oxides WOx (namely W40O118, W20O58, W5O14, W18O49, W8O23, W3O8) and oxide tungsten bronzes MxMyWO3 at M-Li, Na, K, Rb, Cs. They are characterized by metal – like properties. Their band structures display an energy gap in the valence band just below the Fermi level.
We present results of our electrochemical synthesis of tungsten oxide bronzes in ionic melts of the polytungsten salts. Among the new state – of – the art methods for their manufacture, electrochemical synthesis in ionic melts, which makes considerably better use of existing technologies, is highly productive, based on the discharge of oxyanions of the polytungstates.
Keywords: oxide alkali bronzes, alkaline tungsten bronzes, tungsten, molybdenum, nonstoichiometry, tungsten oxides, electroconductivity, electrochromism
Oxide bronzes MxEO3 (M–Na,K; E – W,Mo) are the inorganic materials for technics and chemical technology. Its properties, for example stability in wide interval of temperatures, are of great practical interest (electrodes for fuel elements, electronic apparatuses and others). In this article the results of studies of thermostability of sodium and potassium tungsten and molybdenum bronzes in atmosphere and vacuum condition at the temperatures range 20-1110°C were found. The samples are prepared by electrolysis of melts of sodium and potassium isopolytungstates and molybdates. Dates for bronzes Na0.92WO3 , Na0.68WO3 , Na0.53WO3 , Na0.15MoO3, K0.3MoO3 were characterized by the termogravimetric-differential- thermal analysis (TG-DTA). Regions of stability of Na0.92WO3 : 20-700°C , of MxMoO3 : 300-500°C were founded. Conclusion about correlation of nonstoichiometry of chemical composition of EOx bronzes and oxides, which making important role in formation of less - common metal bronzes structure.
Keywords: oxide alkali bronzes, tungsten, molybdenum, thermostability, nonstoichiometry, thermal analysis