Abstract
Systematic research on a new type of gas sensor devices based on the thermovoltaic effect in zinc oxide, inhomogeneously doped with impurities of variable valence, is presented in the article. The ZnO–ZnO–Me two-layer sandwich structure, in which the thermovoltaic effect is observed, is synthesized using sol–gel technology from sols by dissolving the inorganic zinc salt in alcohol and adding a surfactant, followed by the mixing and maturation of the sol. The lower layer of the nanostructure is formed from pure zinc oxide by immersing the substrate at ⅔ length in sol and drying. The upper layer of zinc oxide doped with copper or iron is formed by two or three immersions of the other end of the substrate by ⅔ length, followed by drying and annealing. It has been established that, based on the developed sensor device, it is possible to obtain an increased response to gas-analyzers (ethanol being an example).
Highlights
Lowering operating temperatures and an increase in sensitivity and selectivity are some of the main tasks for modern gas sensors [1,2,3]
In the case of the samples, the upper layer of which was formed by three immersions, the polarity of the electromotive force (EMF) changed due to a number of the reasons described above
2019, 9, 693 temperature range, with the exception of ZnO/ZnO–Fe, the upper layer of which was formed by three immersions in sol
Summary
Lowering operating temperatures and an increase in sensitivity and selectivity are some of the main tasks for modern gas sensors [1,2,3]. The industry produces sensors obtained using expensive methods and equipment to create and maintain a certain level of vacuum in the working chamber. Sol–gel technology methods, using both centrifugation and dipping operations to form gas-sensitive layers, are promising as an alternative to traditional methods [6]. The advantage of sol–gel methods for producing gas-sensitive sensors is the possibility of obtaining hierarchical network structures with geometric branch sizes commensurate with the value of the. Debye screen length [7]. This ensures a high distribution uniformity of the sensitive nanoelements of hierarchical structures on the surface of the adsorbent
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