Institute of High-temperature Electrochemistry of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

S. V. Vakarin, Senior Researcher, e-mail: s.vakarin@ihte.uran.ru
O. L. Semerikova, Researcher
S. A. Surat, Engineer
A. A. Pankratov, Researcher
Yu. P. Zaykov, Director

The aim of this study was the determination of conditions for obtaining of nanocrystalline coating of oxide tungsten bronzes with hexagonal structure on tungsten substrates. The following object of the study was selected: K_xLi_yWO₃ bronze, obtained by electrolysis of 0,30 K₂WO₄ – 0,25Li₂WO₄ – 0,45 WO₃ mol.% melt at 700 and 750 ^oC. Electrolysis was carried out by pulse potentiostatic method in a three-electrode cell. Platinum wire was used as anode. There was taken a platinum foil (1 cm2) half-immersed in the melt as a reference electrode. Tungsten foil was used as a cathode. The obtained deposits were examined by electron microscopy, X-ray and chemical analysis. It is established, that the electrochemical method allows to get a nanocrystalline coatings on a tungsten substrate. Each micro-crystal of deposit is characterized as oriented nano-needle structure. Additionally, dependence of “overvoltage — pulse duration” parameters is linear. It was found that nanocrystalline bronze contains less alkali metal than the coarse-grained structure. It is concluded that bronze with such composition is formed with participation of more polymerized anionic forms. The areas of conditions (“overvoltage - pulse duration”) are determined for the case when (0001) planes of micro-crystals differ in their morphology. It is shown that nanocrystalline bronze is formed with more polymerized anionic forms. The conclusions are devoted to formation of mechanism for micro-crystal of oxide tungsten bronze with hexagonal structure during the electrochemical synthesis from molten salts. Nanocrystalline bronze can find application in medicine, electrotechnics, radio, food and chemical industry for manufacturing of ion-selective elements for analysis of micro-media, electrochromic devices, cold cathodes and catalysts for chemical reactions.

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