Effect of the heating rate on crystallization and densification of TiO₂ films prepared from alkoxide solutions containing various organic additives

ABSTRACT

The effect of the heating rate on crystallization and densification of sol–gel-derived TiO₂ films has been investigated. The TiO₂ gel films were prepared from Ti(OC₃H₇ⁱ)₄ solutions containing alcohols (2-butanol and 2-methoxyethanol), glycols (propylene glycol, diethylene glycol and dipropylene glycol) and chelating agents (acetylacetone and benzoylacetone) as organic additives, followed by heat treatment to 800°C at various heating rates. In the cases without organic additives and with alcohols, anatase films were obtained irrespective of the heating rate, where the refractive indexes of the films were higher for slower heating rate. Conversely, for the films prepared with glycols and chelating agents, rapid heating activated crystallization and densification. In particular, addition of chelating agents led to the formation of rutile films with much higher refractive indexes than those of the anatase films.

KEYWORDS:

• TiO₂ films
• sol-gel coating
• heating rate
• refractive index

Acknowledgments

We thank Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/21870764.2023.2252230

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by Nippon Sheet Glass Foundation for Materials Science and Engineering, 2022 Research Grant (No. 22-002).