Wolframioksidi

Wolframioksidi, or tungsten oxide, refers to oxides of tungsten, most commonly tungsten trioxide (WO3). Non-stoichiometric suboxides such as WO2 and various tungsten bronzes (HxWO3 and related WxOy phases) also exist. In solid form, WO3 is typically a yellow to blue-white powder and can appear colored when reduced or hydrated. The material is a wide-bandgap semiconductor, with a bandgap around 2.6–2.8 eV, and it can be sensitive to light and electric fields. When reduced to bronzes, it becomes blue and electrically conductive. WO3 is relatively stable in air but can be reduced under heating or in hydrogen-containing environments.

Preparation methods include oxidation of tungsten metal or tungsten compounds, hydro- or solvothermal routes, and deposition techniques for thin films. It forms hydrates and oxyanions in aqueous solutions and can react with bases to form tungstate salts.

Common applications of wolframioksidi include electrochromic devices such as smart windows, where WO3 changes color with ion intercalation under applied voltage; gas sensors for reducing gases and NOx; and photocatalysis or catalytic supports in organic oxidation and environmental remediation. Suboxides and doped forms extend conductivity and catalytic activity, enabling specialized sensors and electrodes.

Safety considerations: wolframioksidi powders should be handled to avoid inhalation; general chemical safety practices apply. Environmental concerns relate mainly to powder dispersion rather than bulk WO3 stability.

See also tungsten bronzes, tungstate, and tungsten oxide for related compounds.