The precursor solution consists of Titanium Tetra Isopropoxide,Acetic acid,methanol and propanol.The shift is towards the lower angle from the standard XRD value for TiO2.Samples were annealed at 300,400,500,600 degree celsius.
- The main reason of the peak shifting is the stress of the film.
- Might be these are some possible reason for peak shift of your film growth parameters, deposition method, substrate - film relation and thickness.
I suspect the main reason is that you do not have 'pure' TiO2 (anatase or rutile) in the materials - it's a compositional change related to the decomposition of your precursor. The sol-gel process basically would precipitate 'Ti(OH)4' and, with calcination at various temperatures, there will be partial decomposition to TiO2 with higher temperatures favoring more complete decomposition. These intermediate Ti 'compounds' (Ti(OH)4 through TiO2) hold onto - OH and - H groups strongly. I suspect in your series that the higher calcination temperatures favor 'true' TiO2 - rutile or anatase forms. Small sizes, strain, instrumental broadening are all factors that broaden the x-ray peak but should not shift the (position of the) peak markedly. You do not state what form of TiO2 you are expecting or comparing to - there are 3 phases to investigate (rutile, anatase, brookite) and you should consult a phase diagram for the stability at various temperatures.
I concur with Alan that you might have a mix of different TiO2 phases with chemisorbed water (OH groups) or other chemical groups attached. Annealing at higher temperatures will remove the OH-groups or other contamination and rearragement of the TiO2 structures will take place. Compare your XRD -data with the ASTM XRD standards of rutile, anatase and brookite. If you find additional peaks at lower temperatures these are probably compositions with the chemical groups mentioned above.
An interesting combination with XRD is a DTA-analysis to see at which temperature you loose weight of the samples.
Thank you very much for the answers..I am expecting an Anatase form but the shift in peak is 4 degrees lower than the standard value..what could have caused this huge shift?
I concur with Alan, small deviations due to stoichiometry changes are possible comparing your sample with the ASTM standard for anataas but these are usually only 0.1-0.2 of a degree. A 4 degree difference means you have a different material or one of the other TiO2 phases.
XRD peak position are greatly affected by the way you prepared your sample for the test. You'd better exclude these factors.
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