I am unable to visualize the basic formation of Oxygen vacancies in Tio2 as sometimes information is a bit scattered. Can anyone help me with how these point defects are formed and what prompts ? Also, I have read that oxygen vacancies play a role in Anatase to rutile transformation. How do these vacancies aid in the structural re-arrangement when subjected to say calcination?
Dear Kailas Naresh, the following documents cover in details phase transition in TiO2. My Regards
10.1088/0022-3727/42/20/205101
https://www.researchgate.net/publication/225798364_Review_of_the_Anatase_to_Rutile_Phase_Transformation
DOI: 10.5772/intechopen.68601
https://doi.org/10.1063/1.5027672
https://doi.org/10.1021/acsomega.0c03431
Dear Kailas Naresh, the following documents cover in details phase transition in TiO2. My Regards
10.1088/0022-3727/42/20/205101
https://www.researchgate.net/publication/225798364_Review_of_the_Anatase_to_Rutile_Phase_Transformation
DOI: 10.5772/intechopen.68601
https://doi.org/10.1063/1.5027672
https://doi.org/10.1021/acsomega.0c03431
Oxygen vacancies are formed in reducing conditions which can be due to many parameters like high-temperature reduction under H2, the reduction under pure N2 gas, the reduction under high pressure with H2. The fundamental is in the absence of oxygen environment and in presence of reducing gases such as H2, Ti--O bonds break to generate H2O, thus leaving vacant oxygen site. These point defects are called f centers which have additional electrons, thereby reducing the band gap and thus imparts color to TiO2 which usually is white to anything from blue, black or grey.
Thank you Saurav Sorcar and Abdelkader BOUAZIZ for your answers. Really helpful :)
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