Preparations and characterizations of nanostructured TiO2 and TiO2-Si(Ti)O2 composite systems

Nanocrystalline TiO2 and TiO2-SiO2 composites have been prepared by sol-gel route. The samples are consolidated and sintered to get nanostructured TiO2 and nanostructured TiO-SiO2 composites. In the TiO2-SiO2 system, the TiO2 nanograins are dispersed in the Si(Ti)O-2 matrix. The experimental techniques namely powder X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Energy Dispersive Analysis of X-ray (EDAX) have been used to determine the crystal structure and compositions. Impedance measurements are made for the samples in the frequency range between 10 Hz and 10 MHz in oxygen atmosphere at various temperatures between 500 and 950 degreesC. The results show that the impedance developed independently from the regions of grain and grain boundary. With the increase in temperature the impedance spectrum becomes smooth having lower d.c. resistance compared to the values for lower temperatures. The conductivity of the grain boundary is found to be dominant compared to that of the grain. The glass like Si(Ti)O-2 insulating structure in between the TiO2 nanograins seems to control the transport properties of the system. (C) 2001 Elsevier Science Ltd. All rights reserved.