Structure of low-silica glasses in the K2O-Nb2O5-SiO2 system
PALEARI, A.
International Laboratory of Glass-Based Functional Materials
Department of Materials Science
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International Laboratory of Glass-Based Functional Materials
Department of Materials Science
PALEARI, A.
International Laboratory of Glass-Based Functional Materials
Department of Materials Science
International Laboratory of Glass-Based Functional Materials
Department of Materials Science
STEFANOVICH, S. Yu.
International Laboratory of Glass-Based Functional Materials
L.Ya. Karpov Institute of Physical Chemistry
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International Laboratory of Glass-Based Functional Materials
L.Ya. Karpov Institute of Physical Chemistry
Language
en
Article de revue
This item was published in
Theoretical Foundations of Chemical Engineering. 2013, vol. 47, n° 1, p. 1-9
English Abstract
The nanostructure and nonlinear optical properties of high-niobium glasses in the (1 − x)KNbO3-xSiO2 system with an SiO2 content x = 0.05-0.35 have been studied by small-angle neutron scattering (SANS), electron microscopy ...Read more >
The nanostructure and nonlinear optical properties of high-niobium glasses in the (1 − x)KNbO3-xSiO2 system with an SiO2 content x = 0.05-0.35 have been studied by small-angle neutron scattering (SANS), electron microscopy (EM), and second-optical-harmonic generation (SHG). Vitreous samples are manufactured by the methods of fast melt cooling (pressing with metal plates and quenching between rotating rolls). Glasses with x < 0.12 have been established to form a micro-inhomogeneous structure in the form of silica-enriched regions at the cooling rates used. According to SANS data, quenched glasses with x > 0.2 are homogeneous, but form a silica-enriched nanostructure after thermal treatments. At temperatures below ∼T g + 50°C, silica-enriched regions manifest a very slight tendency to grow, whereas, according to SANS and X-ray diffraction data, their chemical composition is observed to shift appreciably towards SiO2 with thermal treatment. The obtained data on an inhomogeneous structure allows us to clarify the complicated character of the previously revealed dependence T g (x). Nano-inhomogeneous transparent samples produce a weak SHG signal, which indicates the quasi-periodic modulation of the chemical composition and, correspondingly, polarizability, in the volume of glass. The nonlinear optical phase KNbO3 precipitates at later stages of crystallization, when a glass loses its transparency. In this case, the SHG signal is amplified by several orders of magnitude.Read less <
English Keywords
Nanostructured materials
Nonlinear optical
Niobium
Glasses
Origin
Hal imported