Annealing Effect on the phase Transformation in

Abstract

This work describes the effect of temperature on the phase transformation of titanium dioxide (TiO2) prepared using metal organic precursors as starting materials. X-ray diffraction (XRD) was used to investigate the structural properties of TiO2 gels calcined at different temperatures (300, 500, 700) ?C. the results showed that the samples have typical peaks of TiO2 polycrystalline brookite nanopowders after calcined at (300 ?C), which confirmed by (111), (121), (200), (012), (131), (220), (040), (231), (132) and (232) diffraction peaks. Also, XRD diffraction spectra showed the presence of crystallites of anatase with low proportion of rutile phase where calcined at (500 ?C), while rutile phase domains at (700 ?C). The crystallite size of TiO2 nanopowders was calculated by Scherer's formula and showed that the crystallite size decreased and then increased with increasing the annealing temperature.

Study of Structural , Optical and Electrical Properties for Cr -Doped Tio2 Sensor for NH3 Gas

“…The gas sensitivity of undoped and doped TiO 2 films is calculated from measuring the resistance change in thin films in air and in gas . Figure (8) shows the gas sensitivity of undoped TiO 2 and doped with (Chromium) . It can be seen from this observation that the sensitivity values of all samples increase with time.…”

“…Brookite has been rarely used because its preparation is quite difficult [9]. Anatase possesses a higher photocatalytic activity than rutile due to the difference in the optical band gap [10] .There are many techniques to synthesis TiO 2 thin films, including sol-gel ,sputtering , anodic oxidation, pulsed laser deposition (PLD) , electron-beam evaporation and spray pyrolysis [8]. Among available techniques Spray pyrolysis is a cheap chemical deposition procedure, allowing the growth of rough-surface films at atmospheric pressure and on large area [11].…”