Sensor Properties of Nanostructured Systems Based on Indium Oxide with Co3O4 or ZrO2 Additives

Abstract

The effect of Co₃O₄ and ZrO₂ additives on the sensory response of In₂O₃-based nanostructured composites to H₂ and CO is studied. It is shown that the addition of small amounts of Co₃O₄ or ZrO₂ to In₂O₃ leads to a sharp increase in the sensory response to hydrogen. The maximum sensory response of the ZrO₂−In₂O₃ composite to 1100 ppm of hydrogen increases from 80 to 270 as the ZrO₂ content changes 0 to 20 wt %. The response to CO varies only slightly. For Co₃O₄−In₂O₃ composites, the maximum response to H₂ and CO increases with the Co₃O₄ content within 0−10 wt %. A further increase in the Co₃O₄ content leads to a significant decrease in the response, with composites containing ∼60 wt % Co₃O₄ being characterized by a very low efficiency. In the Co₃O₄−In₂O₃ system with a content of up to 60 wt % Co₃O₄, electronic conduction is realized, which changes to hole conduction at Co₃O₄ within 80−100 wt %. In the ZrO₂−In₂O₃ system, electric current flows through In₂O₃ nanocrystals, i.e., n-type conduction takes place. Possible reasons for the observed effects are discussed.