Abstract
The structural characteristics are investigated of nanoheterogeneous films comprising ZnO, In2 O3 and ZnO + In2 O3 composite produced by aerosol spray pyrolysis technique (SPT). The process utilizes water solutions of zinc chloride and indium nitrate precursors. The X-ray diffraction data show that the SPT process results in polycrystalline films of hexagonal wurtzite type ZnO, and In2 O3 crystals of cubic structure. SPT-synthesized ZnO + In2 O3composites contain mixtures of these crystals. The morphology of the synthesized films is studied by scanning electron microscopy as well as the dependence of morphology on the synthesis conditions, specifically the temperature of the aerosol precipitation and the concentration of the precursors in solutions. The characteristics of nucleation and growth of oxide crystals during the synthesis of ZnO + In2 O3 composite films are also considered. The film with the composition 25 wt% ZnO + 75 wt% In2 O3 contains a large number of small crystal aggregates of arbitrary shape with a high density of contacts between the aggregates and are characterized by a homogeneous structure with high dispersion. Such morphology has high specific surface, which favors high sensory response. In addition, in this range of aggregate composition the relationship between the particles of the catalytically active component- ZnO, cleavage of hydrogen molecule, and In2 O3particles with a high concentration of conduction electrons is close to optimal for the maximum sensory effect in the detection of hydrogen.
Highlights
Metal oxide semiconductor films are widely applied in gas sensors
Such films are usually synthesized by a variety of techniques including Spray Pyrolysis Technique (SPT) [2], sol-gel technique [3], and chemical vapor deposition [4]
The present study focuses on spray pyrolysis technique (SPT)-synthesized composite films of ZnO + In2O3 and comparison with similar films of ZnO and In2O3
Summary
Metal oxide semiconductor films are widely applied in gas sensors The properties of such sensors including sensitivity, selectivity and response time depend critically on the film microstructure [1]. One of the important factors that determine the dependence of sensory phenomena in metal oxide composites on composition is the effect of composition on the morphology of the sensor film. It is important to clarify the morphological features of the composite sensors that exhibit high sensitivity These features depend on the nature of the components of the mixed metal oxide composite and the processing conditions. The present study focuses on SPT-synthesized composite films of ZnO + In2O3 and comparison with similar films of ZnO and In2O3 It relatesthe morphology of the ZnO + In2O3composite films to the sensor response
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