Structure, conductivity and sensor properties of NiO–In<sub>2</sub>O<sub>3</sub> composites synthesis by different methods

The effect of the synthesis method of NiO–In2O3 composites on their structural, conductive and sensory characteristics when detecting hydrogen was studied. Impregnation of indium oxide nanoparticles with a nickel nitrate salt and a hydrothermal method with aqueous solutions of the corresponding salts were used. It has been shown that during the impregnation process, nickel oxide is formed in the form of amorphous nanoparticles on the surface of indium oxide, and during hydrothermal treatment, nickel ions are introduced into In2O3 structures. In impregnated composites, the particle size of indium oxide does not depend on the composition and is 60 nm, while in hydrothermal composites it decreases from 35 to 30 nm with increasing nickel content. With an increase in nickel content from 0 to 3 wt.% for both synthesis methods, the conductivity decreases, and the resistance for hydrothermal samples is an order of magnitude higher than for impregnated ones. The sensory response was almost twice as high.