National Research Tomsk State University, Tomsk, Russia:

O. S. Khalipova, Associate Professor at the Department of Inorganic Chemistry, Candidate of Technical Sciences, e-mail: chalipova@mail.ru
D. S. Fedosov, Undergraduate Student
S. A. Kuznetsova, Associate Professor at the Department of Inorganic Chemistry, Candidate of Chemical Sciences, e-mail: katy20.05.2004@mail.ru

This paper examines the possibility to produce TiО₂ – CeO₂ films (2 to 15 mol % СеО₂) by sol-gel method using sols without stabilisers. It was established that butanol, tetrabutoxytitanium and cerium(III) nitrate sols become capable to form films on day 3 after their preparation due to hydrolysis, electrostatic interaction of hydrolysed salts with the solvent molecules, and polycondensation. When added, cerium(III) nitrate changes the viscosity of sols and the thickness of resultant films. Results of thermal, X-ray phase analyses and of electron probe microanalysis showed that the thermal destruction of sols at 600 oC within the entire range of СеО₂ addition studied leads to the formation of oxide system TiО₂ – CeO₂, which is a mixture of two phases: a crystalline phase of titanium dioxide with an anatase structure (max. crystal grain size ~7 nm) and an X-ray amorphous phase of cerium dioxide. The TiО₂ – CeO₂ films obtained on glass substrates have the thickness of 49–62 nm, the refraction index of 1.79–1.89 and the visible-region transmittance of 80–95%. An increase in the amount of cerium dioxide from 2 to 15 mol % leads to a decrease of the forbidden band width from 2.35 to 2.05 eV. The TiО₂ – CeO₂ films examined in this paper have a greater visible-region transmittance and a smaller forbidden band width compared with popular films of similar composition produced from sols with toxic surfactants.
Support for this research was provided under the Development Programme of the Tomsk State University Priority 2030.

1. Spasiano D., Marotta R., Malato S., Fernandez-Ibanez P., Di Somma I. Solar photocatalysis: Materials, reactors, some commercial, and pre-industrialized applications. A comprehensive approach. Applied Catalysis B: Environmental. 2015. Vol. 170-171. pp. 90–123.
2. Chung L., Chen W.-F., Koshy P., Sorrell C. C. Effect of Ce-doping on the photocatalytic performance of TiO₂ thin films. Materials Chemistry and Physics. 2017. Vol. 197. pp. 236–239.
3. Hamdi D., Mansouri L., Srivastava V., Sillanpaa M., Bousselmi L. Enhancement of Eu and Ce doped TiO₂ thin films photoactivity: Application on Amido Black photodegradation. Inorganic Chemistry Communications. 2021. Vol. 133. p. 108912.
4. Kayani Z. N., Riaz M. S., Naseem S. Magnetic and antibacterial studies of sol-gel dip coated Ce doped TiO₂ thin films: Influence of Ce contents. Ceramics International. 2020. Vol. 46. pp. 381–390.
5. Kidchob T., Malfatti L., Marongiu D., Enzo S., Innocenzi P. An alternative sol-gel route for the preparation of thin films in CeO₂ – TiO₂ binary system. Thin Solid Films. 2010. Vol. 518, Iss. 6. pp. 1653–1657.
6. Khan M. I., Suleman A., Hasan M. S., Ali S. S., Al-Muhimeed T. I. et al. Effect of Ce doping on the structural, optical, and photovoltaic properties of TiO₂ based dye-sensitized solar cells. Materials Chemistry and Physics. 2021. Vol. 274. p. 125177.
7. Mohammadi M. R., Fray D. J. Nanostructured TiO₂ – CeO₂ mixed oxides by an aqueous sol-gel process: Effect of Ce:Ti molar ratio on physical and sensing properties. Sensors and Actuators B. 2010. Vol. 150, Iss. 2. pp. 631–640.
8. Verma A., Samanta S. B., Mehra N. C., Bakhshi A. K., Agnihotry S. A. Sol-gel derived nanocrystalline CeO₂ – TiO₂ coatings for electrochromic windows. Solar Energy Materials & Solar Cells. 2005. Vol. 86, Iss. 1. pp. 85–103.
9. Wang H., Wang Z., Hong H., Yin Ya. Preparation of cerium-doped TiO₂ film on 304 stainless steel and its bactericidal effect in the presence of sulfate-reducing bacteria (SRB). Materials Chemistry and Physics. 2010. Vol. 124. pp. 791–794.
10. Livage J., Henry M., Sanchez C. Sol-gel chemistry of transition metal oxides. Progress in Solid State Chemistry. 1987. Vol. 18, Iss. 4. pp. 259–341.
11. Makishima A., Asami M., Wada K. Preparation of CeO₂ – TiO₂ coatings by the sol-gel process. Journal of Non-Crystalline Solids. 1988. Vol. 100. pp. 321–324.
12. Brusatin G., Guglielmi M., Innocenzi P., Martucci A., Battaglin G. et al. Microstructural and optical properties of sol-gel silica-titania waveguides. Journal of Non-Crystalline Solids. 1997. Vol. 220. pp. 202–209.

13. Leonov A. I. High-temperature chemistry of oxygen compounds of cerium. Leningrad : Nauka, 1969. 201 p.
14. Hume-Rothery W., Smallman R. E., Haworth C. W. Structure of metals and alloys. London : Metals & Metallyrgy Trust, 1969. 407 p.
15. Chen W.-F., Koshy P., Huang Y., Adabifiroozjaei E., Yao Y. et al. Effects of precipitation, liquid formation, and intervalence charge transfer on the properties and photocatalytic performance of cobalt-or vanadium-doped TiO₂ thin films. International Journal of Hydrogen Energy. 2016. Vol. 41. pp. 19025–19056.
16. Inturi S. N. R., Boningari T., Suidan M., Smirniotis P. G. Visible-lightinduced photodegradation of gas phase acetonitrile using aerosol-made transition metal (V, Cr, Fe, Co, Mn, Mo, Ni, Cu, Y, Ce and Zr) doped TiO₂. Applied Catalysis B: Environmental. 2014. Vol. 144. pp. 333–342.
17. Bellamy L. New data on Infrared Spectra of complex molecules. Translated from English. Moscow : Mir, 1971. 318 p.
18. Nakamoto K. Infrared and Raman spectra of inorganic and coordination compounds. Moscow : Mir, 1991. 535 p.
19. Kazitsyna L. A., Kupletskaya N. B. Application of IR, UV and NMR spectroscopy in organic chemistry. Moscow : Vysshaya shkola, 1971. 264 p.
20. Vasconcelos D. C. L., Costa V. C., Nunes E. H. M., Sabioni A. C. S. et al. Infrared spectroscopy of titania sol-gel coatings on 316L stainless steel. Materials Sciences and Applications. 2011. Vol. 2. pp. 1375–1382.
21. Kuznetsova S., Khalipova O., Chen Y.-W., Kozik V. The joint effect of doping with tin(IV) and heat treatment on the transparency and conductivity of films based on titanium dioxide as photoelectrodes of sensitized solar cells. Nanosystems: Physics. Chemistry. Mathematics. 2022. Vol. 13, Iss. 2. pp. 192–203.
22. Zherebtsov D. A., Kuznetsov G. F., Kleshchev D. G., Syutkin S. A., Pervushin V. Y. et al. Сharacteristics of the hydrous titanium dioxide-anatase phase transformation during hydrothermal treatment in aqueous solutions. Russian Journal of Inorganic Chemistry. 2010. Vol. 55. pp. 1197–1201.
23. Verma A., Bakhshi A. K., Agnihotry S. A. Effect of different precursor sols on the properties of CeO₂ – TiO₂ films for electrochromic window applications. Electrochimica Acta. 2006. Vol. 51, Iss. 22. pp. 4639–4648.
24. Zaitsev V. B., Konstantinova Е. А., Deygen D. M., Rumyantseva M. N., Podolko E. V. et al. Optoelectronic properties of nitrogen and carbon doped nanocrystalline titania. Moscow University Physics Bulletin. 2013. Vol. 68. pp. 387–396.
25. Erdey-Gruz T. Transport phenomena in aqueous solutions. Translated from English. Ed. by N. S. Lidorenko, Yu. A. Mazitov. Moscow : Mir, 1976. 596 p.
26. Martin M. V., Alfano O. M., Satuf M. L. Cerium-doped TiO₂ thin films: Assessment of radiation absorption properties and photocatalytic reaction efficiencies in a microreactor. Journal of Environmental Chemical Engineering. 2019. Vol. 7. p. 103478.