Could you help me to explain, why if I used high calcination temperature (put into 600oC of temp condition, directly) can transform my TiO2 into anatase-rutile phase mixture. But if I annealed in the 600oC by slowly heating, i only obtain anatase phase? Thank you so much!
Dear Chintya
Check this link out
http://link.springer.com/article/10.1007%2Fs10853-010-5113-0#
Hi Mr. Mondal,
Thank you for your paper link!
I am quite wondering, why if I used slow or fast heating rate to change the crystal phase, the slower heating rate showed the crystal was more strong and obvious in Raman and XRD. Is there any explanation for it? Thank you,
Best regards,
Chintya
Chintya,
The transformation of anatase to rutile in an aqueous setting was precisely the topic of my thesis research, so you can actually click on my name and it will take you to some of my papers. The short answer is that in water-based solutions, anatase crystallizes first because for very small particle sizes, the effect of surface energy makes anatase more stable. As particles grow, the anatase phase becomes unstable and dissolves, and this feeds the growth of rutile particles. In your experiments (which I assume are dry, and seem to be at higher temperature of 600 oC, the small domains of anatase and rutile probably produce similar surface energy effects, keeping anatase stable until rutile domains grow larger. However, in a dry system the mechanism is more likely to be a solid state reaction, and I don't know the details of how that would proceed.
To Mr. Mondal - I will coincidentally be visiting SIU next week to give a talk on this topic, so if you happen to see this note, come to the talk and it would be great to chat!
Best,
Dan Hummer
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