Effect of Cu Doping on Synthesis, Composition and Sensor Properties of In₂O₃ Nanostructures

Cu-doped In₂O₃ nanocomposites with copper compositions of 1-3 wt.% are synthesized by a hydrothermal method using water or alcohol as a solvent. Cubic In₂O₃ is formed when water is used for synthesis, while composites synthesized in alcohol contain rhombohedral In₂O₃. This trend is independent of the amount of copper introduced. The Cu ions are shown to be uniformly distributed in the In₂O₃ nanoparticles without significant destruction of the indium oxide structure. All the composites exhibit a porous structure that depends on the solvent used for the synthesis. The addition of copper to both crystalline forms of indium oxide increases the resistance of the films and reduces the operating temperature. The phase state of indium oxide also affects the conductivity of the composites. There is an increase in sensory response to H₂ and CO with the introduction of Cu into samples with cubic structure, but a reduction in response in samples with the rhombohedral phase of indium oxide.