Structure and gas-sensing properties of SnO2-In2O3 nanocomposites synthesized by impregnation method

Abstract

The structure, conductivity and conductometric gas-sensing properties of SnO2-In2O3 composites synthesized by impregnating In2O3 nanocrystals with solution of SnCl4 have been investigated. The impregnation method was used to synthesize a composite comprising of SnO2 nanoclusters of 5–7 nm size deposited on the In2O3 nanocrystal surface. By EDX and XRD methods it was found that, the SnO2 nanoclusters contain indium ions, which deform the lattice of the clusters. The maximum efficiency of the synthesized composites in the detection of hydrogen in air is achieved when the SnO2 content in the composite is about 40 wt.%. At such proportions, according to the percolation theory, the current in the composite flows through aggregates of SnO2 nanoclusters. The response of sensitive layer containing 40 wt.% SnO2 to 1100 ppm hydrogen is 1400. Such a high sensitivity of the composite is attributed to the catalytic activity of SnO2 clusters, containing indium ions, and to high porosity of ​​conducting aggregates consisting of SnO2 nanoclusters of 5–7 nm size. This ensures effective interaction of these aggregates with oxygen and the analyzed gas. An additional factor that enhances the sensor response is the transfer of electrons from In2O3 nanoparticles to SnO2 nanoclusters.