Influence of the specific surface area and filler concentration on the coefficient of linear thermal expansion (CLTE) of sintered composites based on high lead fused glass and lead titanate was investigated in order to obtain solder materials offering unusually low CLTE values. The microstructure of compositions was investigated by optical microscopy methods in combination with birefringence testing with a localization of about 1 μm. In samples containing up to 55

We propose a new reactive force field of the ReaxFF family. It is based on computations of model structures with a small number of atoms (no more than four) by density functional theory with dispersion corrections. Unlike the existing force fields, our force field provides the correct description of two polymorphs of crystalline oxide B2O3 that qualitatively differ in the coordination of boron atoms (triangularly and tetrahedrally coordinated boron atoms). The force field application is exemplified by the derivation of the atomic model of borate glass as a result of imitating the melt cooling process. The model quality is verified by comparing with the reported experimental neutron diffraction data.

Borate glasses with a high content of lanthanum oxide are promising materials for the design of high refraction index optical media, although the fine tuning of their properties requires a detailed understanding of their atomic structure. We consider glasses of two systems: La2O3-xNb2O5-(1-x)B2O3 and La2O3-xTa2O5-(1-x)B2O3 with the refraction index varied approximately from 1.7 to 2.0. The local atomic structure of metal atoms is studied by Xray absorption fine structure (XAFS) spectroscopy: the environment of La atoms is probed by La L3-edge XANES, and of Ta atoms - by Ta L3-edge EXAFS. We propose a new approach for the analysis of La L3-XANES which allows a smooth variation of the coordination number N in addition to a commonly used variation of interatomic distances R. The proposed "N,R-fit" approach is verified by the application of a more commonly used method "FitIt" for a quantitative analysis of La L3-XANES spectra. The results of the analysis show that the number of nearest oxygen neighbors of La atoms increases with the increase of M2O5 (M = Ta, Nb) content achieved by the decrease of B2O3 content. On the contrary, the number of nearest oxygen neighbors of M = Ta, Nb atoms is approximately constant and changes occur in the next coordination shells. According to the results of EXAFS analysis, the second and third coordination shells are different for Ta and Nb despite their chemical similarity. And this difference correlates with the discrepancy in maximal content of metal oxide in the glass composition - 20 mol.% for Ta2O5 and 30 mol.% for Nb2O5.

Phosphate glasses with a high concentration of Nd3+ ions are key components for the development of efficient near-infrared (NIR) laser systems. The sensitization of Nd3+ ion luminescence in BaO–P2O5 glass using Ag nanoaggregates is investigated in this study. The results show that the thermally stimulated formation of Ag_m^n+ molecular clusters allow a 15-fold enhancement of the photoluminescence intensity of Nd3+ ions, whereas the formation of plasmonic nanoparticles (NPs) did not achieve such an enhancement. These results open new perspectives for controlling the properties of phosphate glasses and improving the efficiency of laser systems.

The local Abrio method of birefringence assessment was applied for the first time to strengthened glasses, and it was used to investigate the micro-stress distribution in float glass subjected to ion-exchange strengthening. It is demonstrated that the thickness of the stressed layer can be determined with great precision, and a correlation is found between the depth of the stressed layer and the penetration depth of potassium cations in the course of ion exchange.

Local electric field (LEF) distribution near Ag, Au, AgAu NPs synthesized by UV laser or temperature treatments, and near simulated Rb, AgRb, AuRb NPs in oxide glasses, was studied considering aggregates of 10–15 particles - necessary condition for description of optical extinction spectra. For efficient analysis of LEF spatial distributions under different sizes, components, agglomerations of NPs in these aggregates, approach was proposed that enables to obtain dependence of averaged LEF enhancement upon the distance from the nearest particles in aggregate. This approach reproduced enhancement of Er3+ luminescence intensity in zinc-tellurite glass after formation of Ag NPs and showed that average LEF enhancement per hypothetical Rare Earth ion (REI) is largest for aggregates of Ag, less for Rb, lowest for Au NPs. The optimal Ag NPs aggregate was estimated for best LEF enhancement per hypothetical REI. Simulated aggregates of Rb containing NPs demonstrated strong LEF, shifted in a wide range.

Methods of laser micro- and nano-modification of the structure of transparent dielectrics offer much for the creation of a new type of glass-crystalline materials and new applications. In the present work, after a brief excursion into the history of glass-ceramics, transparent aluminosilicate sitalls [glass-ceramics] are discussed, mainly for the example of the Li2O–Al2O3–SiO2 system, and the areas of their new applications. The recently discovered possibilities of laser micro-modification of the structure of sitalls and the writing of elements of photonics and integrated optics in their interior volume are considered. Special attention is given to transparent glass-ceramics with thermal expansion coefficient close to zero.

Zinc magnesium aluminosilicate (ZMAS) glasses were obtained with the addition of Na2O (from 1.1 to 7.0 mol.

Effect of single-doping by Ag2O (8 mol.%), Au2O (0.016 mol.%), Rb2O (8 mol.%), Nd2O3 (0.5 mol.%), Er2O3 (0.5 mol.%) on the structure and optical properties of zinc-phosphate (PZ) glasses was studied. Crystal-chemical similarity of local structures of the dopants in these glasses and in the revealed for them reference crystals of corresponding chemical composition was established by XANES/EXAFS. The specifics of this principle for each of the glasses was determined. Combining the obtained parameters of the embedded metal's local structure with TEM, absorption and photoluminescence (PL) data, the presence of color centers (ionic dimers, nanoclusters, nanoparticles (NPs)), their specific type and optical performances were determined. It was shown that Nd, Er are homogeneously distributed in as-prepared PZ glass without clustering, retaining their PL properties. Formation of Ag, Au, Rb color centers and Au NPs in as-prepared single-doped PZ glasses were studied.

The influence of the modification of glass in the strontium-aluminum-boron-silicate system (SABS) on technological and physicochemical properties was investigated. Introducing two alkalis into the glass makeup significantly lowered the melting temperature, from 1500 to 1450°C, which effected changes in the properties of the glass. On introducing alkalis in amounts up to 5 mol.

The direct femtosecond laser writing of phase optical elements in glasses represents a promising technique for controlling light beams and developing new functional devices that operate on the birefringence effect. In this study, phase plates were written in the volume of silica and nanoporous glasses using a laser beam. For the first time, the chromatic dispersion curves of birefringence were measured for such plates using multiple methods. This allows the retardance of birefringent elements fabricated by direct laser writing to be estimated, even when using commercial birefringence analysis systems operating at a specific wavelength.

Based on calculations, the spatial distribution of the local electric field (LEF) for various structural configurations of silver nanoparticles (NPs) in silicate and zinc-phosphate glasses was studied. The features of this distribution determine the efficiency of energy transfer from plasmonic NPs to rare earth (RE) ions located in the particle vicinity. The mechanism of energy transfer through field enhancement via surface plasmon resonance of particles, which is dominant for NPs of sizes of ≥ 5 nm, is determined by several factors. To clarify their roles and significance, the dependencies of LEF upon the size, spatial distribution, and degree of agglomeration of silver NPs in glass were studied. Comparative analysis of the nature of the field enhancement in places of hypothetical location of RE ions was carried out on the basis of a visual representation of the spatial distribution of the LEF in the vicinity of agglomerates of plasmonic NPs. Based on simulations, the dependencies of LEF intensity enhancement, the spatial distribution of such places in relation to the nearest plasmonic particle, upon the concentration of NPs, their size, degree of agglomeration, and the presence of small (≤ 5 nm) particles in the sample along with the relatively large ones, were determined. The optimal configuration of silver particles in glass for obtaining the maximum average enhancement of LEF intensity per the site of possible location of RE ion is revealed to be an agglomerate of NPs with sizes slightly larger than 25 nm and average distances between particle centers about 30 nm.

The influence of the technological glass-melting parameters of the selected composition in the SrO-Al2O3-P2O3-SiO2-F system on the value of the refractive index and the amount of fluorine remaining in the glass structure post-melting was investigated. The lowering of the melting temperature combined with tableting of the charge [batch] increases fluorine absorption in the glass up to 17 wt.% at the same time, and the value of the refractive index reduction to n(D) = 1.49. It was experimentally established that in the multicomponent glass selected for glass-ionomer cements with two glass-forming oxides (SiO2 and P2O2) and a high Al2O3 content, each wt.% of fluorine reduces the refractive index by about 3.5 x 10 (-4) units.

This paper presents the results of studying the process of laser formation of microstructures from silver nanoparticles in nanoporous quartz glasses. Glass samples were impregnated with organometallic molecules Ag(hfac)COD in a supercritical carbon dioxide environment. The formation of point and linear microstructures was carried out by high-frequency (70 MHz) femtosecond laser radiation with a wavelength of 525 nm and energy in the pulse up to 1 nJ. It was found that the formation of microstructures occurs due to photo- and thermal decomposition of precursor molecules with the formation of plasmonic silver nanoparticles. It is shown that the developed temperatures can exceed the melting point of glass, which leads to the appearance of microstructures with altered refractive index. A qualitative model explaining the individual stages of cluster formation in the glass volume under point laser impact is presented.

For the first time, a local Abrio method for estimating birefringence was applied to hardened glasses, and the distribution of microstresses in float glass subjected to ion exchange hardening was studied. The possibility of precision determination of the thickness of the stressed layer is shown, the correlation between the depth of the stressed layer and the penetration depth of potassium cations during ion exchange is established.

We have obtained the X-ray total scattering patterns at wavelength 0.20735 ? and corresponding to them radial distribution functions (RDF) of electron density for glasses in the La2O3–Nb2O5–B2O3 and BaO–Nb2O5–P2O5 systems. The RDF demonstrate separate peaks at distances below ~1 nm which points on the middle range ordering in the considered glasses. The consideration of RDF for BaO–Nb2O5–P2O5 glasses system with high concentration of BaO show that the middle range order is caused by the polyhedra chains of ideal BaO crystal, and these chains does not belong to any low-index crystal plane. For La2O3–Nb2O5–B2O3 glasses system the polyhedra chains are observed which resemble those in the LaB3O6 crystal, with polyhedra bound through borate groups. For all considered glasses the niobium polyhedra does not form extended chains.

By the Marotta et al method, temperature of 670 ?C at a holding time of 2 hours provides the maximum rate of nucleation the crystalline phase of ?-eucryptite-like solid solutions was found. The activation energy of nucleation and the Avrami parameter were measured by the DSC method, allowing to estimate the crystallization characteristics. The gradient crystallization method has established the temperature range of heat treatment, within which it is possible to obtain a transparent glass-ceramic. The refinement of regime the nucleation stage made it possible to reduce the time of the second stage crystallization required for the complete formation of the transparent glass-ceramic structure. Varying the holding time at a temperature of 710 ?C makes it possible to smoothly change the CTE in the range of ?(3…+41)?10–7 K?1 in the temperature range from ?120 to +500 ?C.

Using absorption spectroscopy, differential scanning calorimetry, and X-ray powder diffraction, we studied the effect of a small addition of CeO2 on the process of thermally stimulated formation of plasmonic Au nanoparticles in the glass of the ZnO–MgO–Al2O3–SiO2 system containing TiO2 and ZrO2 as nucleating agents. It is shown that when the glass is heated from temperatures slightly above Tg to temperatures in the region of the exothermic peak, the plasmon resonance band of Au nanoparticles undergoes a nonlinear shift; however, the addition of CeO2 significantly expands the the shift to the long wavelength region of the spectrum. We performed the computer simulation of the experimental optical absorption spectra, estimated the sizes of the formed nanoparticles and proposed the mechanism of the effect of the CeO2 addition on the formation of plasmonic Au nanoparticles.

The formation of micro-scale tracks in the bulk of porous glass samples using femtosecond laser pulses was investigated, which is of interest for laser writing of active optical waveguides. It was ascertained that the impregnation of nanoporous glass with a bismuth nitrate solution effects the appearance of an orange luminescence band on excitation at 488 nm, which is intensified in the formed tracks. It is demonstrated that increasing the laser pulse energy to 200 nJ makes it possible to increase the phase contrast for tracks written in nanoporous glass containing bismuth, compared to tracks recorded in additive-free nanoporous glass.

Изучена динамика развития структуры двулучепреломляющих лазерно-индуцированных модификаций в нанопористом стекле в зависимости от количества записывающих фемтосекундных импульсов. Обнаружена трансформация эллиптической полости, вытянутой перпендикулярно поляризации записывающего лазерного пучка, в двулучепреломляющую нанорешетку, которая сопровождается увеличением фазовой задержки. Продемонстрирована возможность перезаписи структур путем изменения ориентации их медленной оси двулучепреломления, что обуславливает перспективность применения высококремнеземистых нанопористых стекол в качестве носителей информации с возможностью перезаписи.