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0915-R07-10

Nanostructured (Sn,Ti, Nb)O2 Solid Solution for Hydrogen Sensing Maria Cristina Carotta, Michele Benetti, Vincenzo Guidi, Sandro Gherardi, Cesare Malagu', Beatrice Vendemiati, and Giuliano Martinelli Physics Department, University of Ferrara, Via Saragat 1/C, Ferrara, 44100, Italy

ABSTRACT A novel co-precipitation route for preparation of a single-phase nanograined (Ti, Sn, Nb)O2 solid solution has been accomplished in the proportions Sn:Ti:Nb 100:42:5. Electron microscopy and X-ray diffraction have been adopted to observe the morphology and the structure. Calcination at 550, 650, 850 or 1050 °C for 2h, showed rutile-like single-phase. The powders have been deposited as thick films through screen-printing technique to achieve gas sensors. SEM analysis of both powders and films showed regularly-shaped nanometric particles, the nanostructure being maintained up to 1050°C. The sensing layers, obtained from powders calcined at 550 °C, and fired at 650 or 850 °C, have been tested vs. several reducing gases showing large responses to hydrogen with good selectivity. INTRODUCTION Nowadays, detection of hydrogen is particularly useful in chemical, petroleum and semiconductor industries, as well as for safety applications in fuel cells or gas-burning power generators, or as firing alarm. Hydrogen sensors could also be used in medical applications, e.g. as a diagnostic tool to monitor some types of bacterial infections. A wide variety of semiconductor oxides has been proposed for gas sensing, SnO2 being the most widely used, also in commercial devices. SnO2-based gas sensors, indeed, exhibit high response to reducing gases, such as H2, hydrocarbons and CO, although they suffer from poor selectivity. Furthermore chemical degradation at high temperature and low oxygen partial pressure give rise to changes in electrical properties upon prolonged exposure to reducing gases [1]. TiO2 is comparatively more stable with temperature than SnO2 despite its lower sensitivity due to the higher density of surface states, leading to pinning of the Fermi level [2]. Recently, great attention has been paid to mixed metal oxides and solid solutions with the expectation of an electrical behaviour superior to that of single-oxide counterparts [3-5]. In an earlier work, the authors investigated Sn1-xTixO2 (0.3