Characterization and butanol/ethanol sensing properties of mixed tungsten oxide and copper tungstate films obtained by spray-sol-gel

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Damián M.A.
Estrada W.
Rodriguez Y.
Solis J.L.
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Elsevier BV
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Mixed WO3-CuWO4 films have been prepared from an aqueous solution of copper sulfate and polytungsten gel with a molar ratio of Cu/W from 0 to 100%. These solutions were sprayed on to alumina substrates at 220 °C. The obtained films were amorphous and crystallized after annealing at 300 °C in air for 3 h. The annealed films were composed of a mixture of CuWO4 and WO3 phases. The film obtained from a solution with an equimolar ratio of Cu/W was pure CuWO4. The pure WO 3 films obtained have high surface 'irregularities', such as porosity. These surface 'irregularities' in the films were maintained or even increased as Cu/W molar ratio augments in the starting solution up to 10%. The gas sensitivity to butanol and ethanol vapors is also enhanced when the CuWO4 phase increases in the film by up to 7-10%; with further increments to this proportion the detection sensitivity decreases, so compromises are approximately 7-10%. The gas sensitivity of pure CuWO 4 was lower than that of pure WO3.
This work has been financially supported by the International Program for Physical Science of Uppsala University (IPPS), the Instituto de Investigación of Universidad Nacional de Ingenieria, and CONCYTEC (Peruvian Research Council).
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Tungsten compounds