Structural, optical, and photoelectrochemical properties of nanocrystalline TiO2-In2O3 composite solids and films prepared by sol-gel method

Nanocrystalline titanium and indium oxides and TiO2-In2O3 composites have b een prepared by sol-gel technique using concentrated hydrous titanium dioxi de and indium hydroxide sols. Structure, optical, and photoelectrochemical properties of the composites with different molar ratios of TiO2 to In2O3 h ave been studied. The binary oxide films and xerogels annealed at temperatu res from 200 to 700 degreesC have a nanocrystalline structure without the c hemical interaction between the oxides. However, there is a strong mutual i nfluence of the components of the binary oxide systems, during their anneal ing which manifests itself in thermogravimetry and differential scanning ca lorimetry measurements and in a marked effect on the oxide crystallite size . Highly transparent TiO2-In2O3 films fabricated by spin-coating technique exhibit extreme dependencies of the various optical and photoelectrochemica l properties on the film composition. The band gap edge of the composite fi lms is blue-shifted, as compared with that of single-component films. Possi ble causes of these effects have been discussed, The conductivity of TiO2-I n2O3 films changes by 6 orders of magnitude in the range of compositions ne ar the calculated value for percolation threshold associated with the forma tion of 3D infinite clusters of interconnected In2O3 nanoparticles.