Fabrication of silica-anatase multilayer coating on a KCaZnSi glass substrate

• Published in: Thin solid films Vol. 441; no. 1; pp. 50 - 55
• Main Authors: Okudera, H, Nonami, T
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 22.09.2003; Elsevier Science
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Coatings; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; General and physical chemistry; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Photocatalyst; Physics; Silicon oxide; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Titanium oxide; Silicon oxide; Coatings; Titanium oxide; Photocatalyst; Inorganic compounds; Anatase; Photocatalysis; Transition element compounds; Crystallization; Polycrystals; Amorphous state; Experimental study; Thin films; Multilayers; Optical transmission; Silicon oxides; Preparation; Titanium; Ultraviolet visible spectrum; Dip coating; Thermal annealing; Catalyst activity; Sol-gel process; Growth from solution
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(03)00885-X

A transparent, rigid amorphous silica (SiO 2)-anatase phase titania (TiO 2) multilayer coating was fabricated on KCaZnSi glass substrate (i.e. slide glass for optical microscope use). The silica and titania layers were successively fabricated in that order by the hydrolysis of Si-tetraethoxide in ethanol and Ti-tetraethoxide in iso-propanol, respectively, at 20 °C and annealing in air at 350 °C after each cycle. X-ray diffraction profiles showed that the titania upperlayer was successfully transformed to polycrystalline anatase in samples where the thickness of the silica underlayer d s was 230 nm and/or that of the titania upperlayer d t was 99 nm and that no crystallization occurred in samples where d s and d t were 115 nm and 55 nm, respectively. No amorphous-anatase transformation occurred when the silica underlayer was not prepared nor when it was used as-deposited. This indicated that amorphous-anatase transformation in the upperlayer was hindered by the migration of elements diffused from the substrate. The silica underlayer of d s=115 nm was less effective as a barrier to these elements but was still sufficient when a thicker upperlayer, i.e. d t=99 nm, was fabricated. Ultraviolet–visible (UV–Vis) spectroscopy indicated efficient filtering of UV light by the multilayer coating where d s=115 nm and d t=99 nm. The absorption edge was determined to be at λ=318 nm, while the loss of visible light was less than 12% per coating over the range of 480–850 nm.