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

Abstract

Mixed WO 3 -CuWO 4 films have been prepared from aqueous solution of copper sulfate and polytungsten gel with molar ratio Cu/W from 0 to 100 %. These solutions were sprayed onto alumina substrates at 220 ºC. The obtained films were amorphous, and crystallized after an annealing at 300 ºC in air for 3 h. The annealed films were composed by a mixture of CuWO 4 and WO 3 phases. The film obtained from a solution with an equimolar ratio of Cu/W was a pure CuWO 4 . The pure WO 3 films obtained have a high surface "irregularities" (eventually the porosity). Those surface "irregularities" in the films were maintained or eventually increased as Cu/W molar ratio augments in the starting solution up to 10%. The gas sensitivities to butanol and ethanol vapors are also enhanced when the CuWO 4 phase increases in the film up to 7% -10%; further increments to this proportion the detection sensitivity decreases, so compromises are around 7% -10%. The gas sensitivity of pure CuWO 4 was lower than pure WO 3 .

Taguchi method assisted optimization of electrochemical synthesis and structural characterization of copper tungstate nanoparticles

“…Several physical or chemical synthesis routes, i.e., deposition by spray [18], deposition via pulsed laser [19], radio-frequency assisted sputtering deposition [20], sol-gel method [21], fabrication in solidphase [22], surfactant aided precipitation [23] and fabrication in polyol-media [24] have been utilized for the preparation of different morphologies of copper tungstate nanoparticles, i.e., nanofilm, nanosphere, and porous film. These methods have own advantages; however, each of them suffers from some restrictions such as requiring for the strictly controlled synthesis media, high synthesis costs, and complexities in the synthesis reaction.…”

First-principles calculations and X-ray spectroscopy studies of the electronic structure of CuWO4

“…Therefore, Table 1 Lattice parameters of copper tungstate, CuWO4, as determined by different authors (triclinic structure, space group P1). different routes are applied for obtaining high-quality CuWO 4 in the form of bulk crystals (e.g., slow-cooled indirect flux reaction technique [17,18], recrystallization in an ampoule for chemical vapour transport [19]), films on different substrates (e.g., spray-sol-gel deposition [20], radio-frequency (RF) sputtering deposition [21]) or nanocrystalline powders possessing poor agglomeration of crystallites [22]. When measuring electrical conduction of a single-crystal copper tungstate, Bharati et al [23] have shown that CuWO 4 is an intrinsic semiconductor with the band gap, E g , 1.52 eV.…”

Surface morphology engineering of metal‐oxide films by chemical spray pyrolysis

“…SnO 2 sols were obtained from tin alkoxide Sn(t-OAm) 4 or tin salt (SnCl 4 .5H 2 O) precursors and stabilized with ammonia or tetrabutyl ammonium hydroxide (TEA-OH) as peptizers [21]. The sols prepared as described above were sprayed onto the substrates heated at 130 °C for 1 h. The gas carrier flux and air pressure were kept at 40 L/min and 1.5x10…”

“…After annealing at a temperature of 400 °C, the samples crystallized into SnO 2 with mean grain sizes of around 20 nm. The morphology of SnO 2 films obtained from SnCl 4 5H 2 O and (C 5 H 11 O) 4 Sn precursors and annealed at 500 °C for 2 h are shown in Figs. 12a and 12b, respectively.…”

“…Films with different architecture have been produced by SPT, e.g. self-assembled quantum dots of iron oxide thin films were obtained from non-aqueous media [2], nanostructured spherical porous SnO 2 anodes for lithium-ion batteries [3], interconnected web-like architecture growth of sprayed WO 3 [4] and TiO 2 films [5], etc.…”