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

• Published in: Thin solid films Vol. 444; no. 1; pp. 104 - 110
• Main Authors: Damián, M.A., Rodriguez, Y., Solis, J.L., Estrada, W.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.11.2003; Elsevier Science
• Subjects: Copper tungstate; Cross-disciplinary physics: materials science; rheology; Ethanol; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Pyrolysis; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Spray coating techniques; Tungsten oxide; Tungsten oxide; Pyrolysis; Ethanol; Copper tungstate; Chemical sensors; Inorganic compounds; Spray coatings; Transition element compounds; Crystallization; Roughness; Surfaces; Volatile organic compound; Tungsten oxides; Experimental study; Thin films; Sensitivity; Aqueous solutions; Preparation; Thermal annealing; Sol-gel process; Copper tungstates; Gas detector; Growth from solution
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(03)01048-4

Mixed WO 3–CuWO 4 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 CuWO 4 and WO 3 phases. The film obtained from a solution with an equimolar ratio of Cu/W was pure CuWO 4. 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 CuWO 4 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 WO 3.