Polycrystalline well-shaped blocks of indium oxide obtained by the sol-gel method and their gas-sensing properties

Aging-induced aggregation of the nanoparticles in the colloidal solution of indium hydroxide leads to the formation of micrometer particles in the form of well-shaped blocks. As shown by high-resolution transmission electron microscopy and selected area electron diffraction, the well-shaped blocks have a polycrystalline nature composed of small nanounits. After calcination at 400 degreesC, they consist of cubic and hexagonal In2O3. Semiconducting sensors, composed of well-shaped blocks of cubic and hexagonal In2O3, show high sensitivity to low levels of ozone in the air.