Surface and near-surface structure of silicate glasses

This paper presents analytic results, derived by diffractional low and large angle X-ray scattering methods, currently applied in our laboratory, as well as novel methods of electron emission microscopy and interference-phase optical microscopy for studying the internal structure, and that of surface and near-surface layers of raw and stepwise-etched, composite oxide silicate glasses of the type SiO₂-Na₂O-CaO-MgO. The structural and topographic studies are supplemented with quantitative analysis of chemical composition on a micro-scale and in micro-regions by electron microprobe and microscopic measurements of the temperature characteristics in a series of the above glasses. Moreover, a discussion is given of chemical corrosion, surface strcuture and topography, and the distribution of micro and macro-inhomogeneity regions in surface layers. Structural parameters are obtained which described the surface and internal structure of silicate glasses well adapted to the construction of an approximate aperiodic nodal model. The applications of the latter and the accuracy of its parameters are discussed.     

Luminescence of praseodymium in silicate glasses

The term scheme of the absorption and luminescence spectra of Pr³⁺ in silicate glasses was established and interpreted for the region 0.4–2.5 . It was shown that a radiationless transfer of excitation energy exists between Pr³⁺ and Yb³⁺ ions. This leads to concentration quenching of the Pr³⁺ luminescence in the first case, and to sensitized Yb³⁺ luminescence in the second case.     

Cauchy's dispersion equation reconsidered: Dispersion in silicate glasses

We formulate a novel method of characterizing optically transparent substances using dispersion theory. The refractive index is given by a generalized Cauchy dispersion equation with coefficients that are moments of the uv and ir absorptions. Mean dispersion, Abbé number, and partial dispersion are combinations of these moments. The empirical relation between index and dispersion for families of glasses appears as a consequence of Beer's law applied to the uv spectra.     

二元碱金属硅酸盐玻璃团簇结构的拉曼散射活性及其阳离子效应

提出一种拉曼光谱校正方法.通过计算二元碱会属硅酸盐团簇基元的拉曼光谱,对实验光谱高频区的非桥氧(Onb)对称伸缩振动的强度进行了校正,从而建立谱峰强度和团簇实际浓度的直观相关关系,同时,分析研究了二元碱金属硅酸盐玻璃阳离子对谱峰强度的影响.校正后的拉曼光谱可以真实地显示同化学成分的二元碱金属硅酸盐玻璃表观实验拉曼谱峰强...     

Subthreshold emission in silicate glasses and quartz crystals

Journal of Applied Spectroscopy -     

Nonlinear light absorption and luminescence in silicate glasses

The study of luminescence of high-purity multicomponent silicate glasses excited by radiation of a N₂ laser (λ=337 nm, P≈12kW) showed darkening of a sample and a monotone decrease in luminescence intensity and the transmitted radiation intensity from pulse to pulse. Additional illumination with radiation of an Ar⁺ laser (λ=514.5 nm) caused an increase in luminescence intensity. An increase in absorption and a decrease in luminescence intensity were found to be caused by two-photon absorption and electron-hole pair production.     

Fluorescence yield in rare-earth-doped sol-gel silicate glasses

We have used trivalent terbium to investigate the mechanism behind fluorescence enhancement by Al³⁺ co-doping. Our results indicate that rare-earth (RE) ions cluster together in aluminum-rich regions of the glass, and behave as if they were dispersed uniformly throughout these regions when the ratio of Al to RE is ∼10 or greater. We also studied the effects of adding chemical drying agents to the precursor solution for the synthesis of sol-gel-derived silicate glasses. Such glasses can be treated at significantly higher annealing temperatures without degradation of optical quality, and have the density of melt glass. Fluorescence yield from doped RE ions improves markedly with the addition of the drying agents, and the denser glasses are not subject to rehydration.     

Subcritical viscosity anomaly in sodium silicate glasses

A subcritical viscosity anomaly is reported in binary mixtures of Na₂O-SiO₂. The results are discussed qualitatively in terms of inhomogeneities which are present in the system.     

Dielectric relaxation in alkali silicate glasses: A new intepretation

The electric and dielectric properties of a ternary alkali sillicate glass (0.14 Na₂0?0.11 Mg0?0.75 SiO₂) have been studied as a function of temperature (350 K ? 600 K) and frequency (1 Hz ? 100 khz) using the impedance spectroscopy. It is proved that dispersion arises from the motion of sodium ions. Experimental data are interpreted with the helo of the CTRW, Continuous Time Random Walk, formalism developed by Scher and Lax which assumes that all the alkali ions are mobile but with different mobilities.     

Quantitative Raman spectroscopy: speciation of cesium silicate glasses

The silicate speciation forms an important aspect of the structure of silicate melts, a subject of interest to both the earth‐ and materials science communities. In this study, the Qⁿ speciation of binary cesium silicate glasses was studied by Raman spectroscopy. A method to extract the equilibrium constant from a set of Raman spectra is presented, and the least‐squares optimization algorithm is given (in Supporting Information). Log(K), the equilibrium constant of the speciation reaction, 2Q³ = Q⁴ + Q², equals −2.72 ± 0.11 at the glass transition. This extends the previously established correlation between log(K) and the inverse of the ionic radius of the network modifier to cesium. Copyright © 2009 John Wiley & Sons, Ltd.     

Phase separation and partial devitrification in soda-lime silicate glasses

2 O-rich droplets dispersed throughout the SiO₂-rich matrix and nanoparticles of metallic silver. In exchanged specimens the joint effect of colloidal silver and electric field results in partial transformation of the amorphous droplets into crystalline Na₂O particles. Received: 11 February 1998 / Accepted: 20 November 1998 / Published online: 24 February 1999     

Local coordination geometry around Cu and Cu ions in silicate glasses: an X-ray absorption near edge structure investigation

We present an X-ray absorption near edge structure (XANES) study on Cu⁺ and Cu²⁺ ions in silicate glasses at the Cu K-edge, aimed to determine the geometry of the local structure around the metal. This study is based on the comparison between experimental data and theoretical calculations made in the framework of multiple scattering theory. The XANES signals relative to several clusters are simulated on the basis of known crystalline structures involving Cu⁺ and Cu²⁺ ions in silicate matrices. Concerning the Cu²⁺ in glass, the simulations suggest the presence of a square coordination of oxygen atoms around the absorber, with a possible presence of metal ions in the second shell. As for the Cu⁺ ions, the metal clustering is excluded and a linear O-Cu-O coordination is evidenced. Received 30 April 1999     

Single molecule acid-base kinetics and thermodynamics

We report a method in which temperature dependent single-molecule fluorescence measurements are used to study the kinetics and thermodynamics of the acid-base interaction in films of photoresist polymer. We use the two distinct fluorescent prototropic forms of Coumarin 6 (C6-->C6+) to indicate the state of the acid-base system. Data are analyzed using a statistical model of the intensity probability distributions, yielding temperature dependent proton exchange rates, which is confirmed through agreement with a simple two-state Monte Carlo model. The temperature dependent rates are used to calculate the activation enthalpy for proton exchange.