Correlation between dielectric constant and chemical structure of sodium silicate glasses

Abstract

The chemical structure of sodium aluminosilicate glasses is determined by high resolution x-ray photoelectron spectroscopy ͑XPS͒ as silicon is gradually replaced by aluminum. A well-defined chemical state is found for silicon, aluminum, and sodium atoms, while three different environments are identified for oxygen atoms corresponding to Si-O-Si, Si-O-Al, and Si-O-Na bonds. The binding energy of Na 1s photoelectrons increases significantly with increasing aluminum substitution while that of Al 2p and components of O 1s photoelectrons remains approximately constant. Thus, the ionicity of sodium increases with aluminum amount, but the over all electron density around silicon, aluminum, and different types of oxygen atoms remains unchanged. The dielectric constant of the glasses increases with increasing aluminum substitution. It is analyzed in terms of the polarizabilities of constituent structural units, viz., silicon tetrahedra, nonbridging oxygen-sodium ion pairs, and aluminum tetrahedron-sodium ion pairs. The electronic polarizability of oxygen ions depends linearly on their negative charge and can be correlated to the O 1s XPS binding energy. The ionic polarizability of sodium ions increases with an increasing aluminum amount, and correlates directly with the Na 1s XPS binding energy.

Octamethylcyclotetrasiloxane-Based, Low-Permittivity Organosilicate Coatings

“…The electronic polarizability of SiO 2 as determined from the model is 2.87 Å, 3 in close agreement with literature data. 37,38 The numbers for ͑CH 3 ͒ 2m SiO 2−m and Si͑CH 2 ͒ x O 2−x are larger than for SiO 2 , because replacing the Si-O bond with Si-CH 3 or Si-CH 2 bond breaks the Si sp 3 symmetry. This causes a shift in the electron distribution around the Si atom and results in a stronger molecular dipole moment.…”

Dielectric Constant of Sodium Silicate Glasses in Relation to Their Chemical Structure

“…Here we primarily focus on the distribution of Na 3s' valence electrons which are most pertinent for relating to the electrical properties. Detailed structure information for chemical structure around all the elements is presented elsewhere [3,6].…”

“…In order to analyze the dielectric constant of the sodium aluminosilicate glasses in terms of the microscopic polarizabilities, three structural units are considered: the silicon tetrahedra [SiO2], the non-bridging oxygen -sodium ion pairs [0 1 2 -Na], and the aluminum tetrahedronsodium ion units [A10 2 -Na]. The ionic polarizability of these three units is calculated by a stepcomposition method [6]. The sodium ionic polarizability, acc , ,, is then obtained by averaging the polarizabilities of [0Ol 2 -Na] and [Al0 2 -Na] according to their relative concentration ( Table 2).…”

Effect of electrical properties of glass electrodes on the performance of RPC detectors for the INO-ICAL experiment

“…The modification of SiO 2 network through Na + (alkali ion) network modifiers is illustrated in figure 4b. In an electric field, the more content of network modifiers leads to more easily polarizable nonbridging oxygens and therefore increase of the relative permittivity of material [11,12]. The tested Asahi glass has larger amount of sodium (Na) component (∼ 2%) compared to Saint-Gobain glass as seen in table 2.…”