The effect of PO2,5 and AlO1,5 additions on structural changes and crystallization behavior of SiO2-TiO2 sol-gel derived glasses and thin films

SiO 2 -TiO 2 -PO 2,5 (STP) and SiO 2 -TiO 2 -AlO 1,5 (STA) glasses were prepared by sol-gel processing. Their infrared absorption spectra (IR), differential thermal analysis curves (DTA) and X-ray diffraction patterns (XRD) have been recorded. In the SiO 2 -TiO 2 system, the chemical homogeneity of...

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Bibliographic Details
Published in:Journal of sol-gel science and technology 2010-07, Vol.55 (1), p.126-133
Main Author: Vasconcelos, H. C.
Format: Article
Language:English
Subjects:
Absorption spectra
Aluminum oxide
Anatase
Ceramics
Chemistry
Chemistry and Materials Science
Colloidal gels. Colloidal sols
Colloidal state and disperse state
Composites
Cristobalite
Crystallization
Differential thermal analysis
Diffraction patterns
Exact sciences and technology
General and physical chemistry
Glass
Heat treatment
Infrared absorption
Infrared analysis
Infrared spectra
Infrared spectroscopy
Inorganic Chemistry
Materials Science
Melts
Nanotechnology
Natural Materials
Optical and Electronic Materials
Organic chemistry
Original Paper
Phosphorus pentoxide
Precipitates
Silicon dioxide
Sol gel process
Sol-gel processes
Tetrahedra
Thin films
Titanium
Titanium dioxide
X-ray diffraction
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Summary:SiO 2 -TiO 2 -PO 2,5 (STP) and SiO 2 -TiO 2 -AlO 1,5 (STA) glasses were prepared by sol-gel processing. Their infrared absorption spectra (IR), differential thermal analysis curves (DTA) and X-ray diffraction patterns (XRD) have been recorded. In the SiO 2 -TiO 2 system, the chemical homogeneity of the sol-gel glass could be evaluated by the relative concentration of Si-O-Ti heterocondensation comparing to Si-O-Si homocondensation. For the STA system, a gradual decrease of the Si-O-Ti/Si-O-Si band ratio (based on IR spectra) with the addition of Al 2 O 3 is observed, with the simultaneous formation of Si-O-Al and Ti-O-Al bounds, i.e Al 3 + ions are dissolved in the SiO 2 -TiO 2 glass matrix and do not promote glass-in-glass phase-separation in the composition range of 0–15 mol% AlO 1.5 . In the STP system, on the other hand, P=O bond IR stretch in the ternary glasses indicates that P=O free PO 2 O 2/2 − tetrahedra are formed, rather than the double bonded POO 3/2 tetrahedra that usually occur in binary SiO 2 -P 2 O 5 glasses. It can be concluded that SiO 2 -TiO 2 -P 2 O 5 glass separates into a SiO 2 -rich phase and a TiO 2 (P 2 O 5 )-rich phase. During heat-treatment in STA system only anatase precipitates, even at T  ~ 1,000 °C, while in for STP, anatase (TiO 2 ) or (TiO) 2 P 2 O 7 (TOP) crystals precipitate at ~600 °C, depending on the P 2 O 5 concentration. The major crystal phase, cristobalite, precipitated at ~1,000 °C and at ~1,200 °C, the P-containing phase melts.
ISSN:0928-0707
1573-4846
DOI:10.1007/s10971-010-2223-8