Gas sensing properties of the nanostructured anodic Zr–W oxide film

The sensing properties of nanostructured Zr–W mixed oxide film have been investigated. The film was prepared via anodizing a sputter-deposited Zr–W alloy layer through nanopores in an anodic alumina layer superimposed on the alloy. The morphology, structure and chemical composition of the film were examined by SEM and XRD. The film consists of an array of self-ordered nanocolumns protruding from a continuous thin oxide layer. The initially amorphous film material crystallizes to monoclinic WO3 and orthorhombic ZrO2 due to a high temperature annealing in air. A sensor employing the ZrO2–WO3 oxide film as active layer was fabricated and used for detecting various concentrations (1–1000 ppm) of H2, CO, C2H5OH and NO2 at temperatures up to 300 °C. In hydrogen detection experiments, the sensor was very fast, with a response time of 19 s, and highly sensitive to hydrogen, with a response value of up to 50, while showing incomparably weaker and slower responses to carbon monoxide, ethanol and nitrogen dioxide. The features of the films revealed to date are of importance for improving the chemical, structural and exploitation stability of nanostructured tungsten-oxide-based films and their selectivity in hydrogen gas detection.