Dear All
Please, What is the cause of pale yellow color of TiO2 prepared by sol gel ?
I prepared it as following:
5 ml Titanium isopropoxide + 50 ml isopropanol and added solution B (10 ml isopropanol+0.1 ml HNO3+1.5 ml water) was added dropwise and then left for gelation for 1 d, then drying at 60 C and calcination at 500 C for 2 hr.
Regards,
Heating TiO2 to a temperature exceeding 400◦C, an irreversible change, yellowing, takes place.
This is due to the crystal lattice expansion, recrystallization accompanied by the formation of rutile nuclei and the crystallites growth.( please go through the introduction of the attached article) for more explanations,
Thank you
Small particles of titania can scatter light into the yellow region too. I wonder if you have particulate contamination in your film (possibly from the sintering temperatures mentioned in the above answer).
Have a look at:
August 11th 2011 Optical properties of the three forms of titanium dioxide
http://tinyurl.com/pbgf9hj
Also take a look at:
Influence of deposition parameters on optical properties of TiO films K. Narasimha Rao Opt. Eng. 41(9) 2357–2364 (September 2002)
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