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.

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.

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.

Ga-oxide spinel nanocrystals are wide band gap systems, which can be incorporated in a glass matrix by phase separation mechanisms. In suitable conditions, this kind of processes can give rise to transparent nanostructured glass-ceramics with UV excitation and luminescence properties potentially interesting in several technological areas. Nanophase size dispersion and volume fraction have been demonstrated to be controllable, at some extent, by suitable thermal treatments for nucleation and nano-crystallization in low-alkali gallium germanosilicate system. Here we report the results on the role of Al2O3 additions on the microstructure and optical response of the glass-ceramics fabricated in this system. Data of differential scanning calorimetry, X-ray diffraction, trans-mission electron microscopy, absorption and fluorescence spectroscopy show that Al2O3 addition, up to 4.5 mol %, turns out to have a considerable impact on the size and number density of precipitated nanocrystals, which are solid solutions of & gamma;-Ga2-xAlxO3 resulting from the partial incorporation of Al3+ ions into the crystalline phase. We show that the use of Al2O3 as an additive in the composition of gallium germanosilicates facilitates glass melting and leads to glass-ceramics with significantly modified photoluminescence characteristics such as decay lifetime and integrated intensity of light emission. The possible reasons are discussed.

The effect of a small addition of CeO 2 on the process of thermally stimulated formation of Au plasmonic nanoparticles in ZnO–MgO–Al 2 O 3 –SiO 2 glass containing the crystallization catalysts TiO 2 and ZrO 2 was investigated by means of absorption spectroscopy, differential-scanning calorimetry, and x-ray diffraction analysis. It is shown that on heating glass from temperatures slightly above T g up to temperatures near the exothermic peak the plasmon resonance band of nanoparticles undergoes a nonlinear shift, but the addition of CeO 2 substantially expands the shift zone to the long wavelengths of the spectrum. Computer modeling of the experimental absorption spectra was performed, the sizes of the formed nanoparticles were calculated, and a mechanism whereby adding CeO 2 effects the formation of plasmonic Au nanoparticles is proposed.

Many efforts are currently focused on materials with responsive features for neural-inspired devices. Different approaches are followed, based on various mechanisms – from ferroelectric switching to structural phase changes, from magnetic tunnel junctions to metal filament formation. Here we analyze an alternative strategy based on an unconventional electrical response arising from percolative charge transport and charge trapping in discrete random networks of oxide nanostructures in a dielectric matrix. After an analysis of the mechanisms which can potentially be a source of a plastic response in this class of systems, we report evidence of this behavior in a system comprising an alkali-germanosilicate amorphous matrix with incorporated Ga-oxide nanostructures. The active material – consisting in a film 70 nm thick interfaced to p-type Si and Au electrodes – gives a responsive behavior to pulsed bias which is accompanied by bias dependent electric conduction, with resistivity changes of an order of magnitude by applying 2 V, as well as a dielectric response with hysteretic features, as expected by the model. The results represent a first proof of concept of an unexplored strategy for the design of responsive systems.

The effect of added Al2O3, introduced by the substitution method, on the crystallization and spectral-luminescent properties of gallium germanosilicate glasses with γ-Ga2O3:Ni2+ nanocrystals was investigated. It was found that the Ni2+-luminescence efficiency increased on account of both an increase in the degree of crystallinity of glass with Al2O3 and an increase in the strength of the crystal field around the Ni2+ ions on account of Al3+ incorporation into the structure of the precipitated nanocrystals.

Fused yttrium-alumoborate glasses doped with ytterbium, silicon, chromium, and sodium were synthesized. The influence of the matrix on the "spectroscopic behavior" of chromium ions and the efficiency of their sensitization of Yb3+ luminescence was established by spectral-luminescence and EPR-studies. It was found that (1) chromium in alkali-free glasses is mainly in the oxidation degree Cr(III) with an appreciable admixture of Cr(IV) and Cr(V), (2) the partial replacement of Al2O3 or B2O3 by SiO2 and Y2O3 by Yb2O3 affects to a different extent the relative concentration of optical centers of chromium ions, (3) the addition of alkali results in the formation of Cr(VI) centers as a result of oxidation of less charged chromium ions and predominantly tetracoordinated Cr4+ and Cr5+, (4) Cr3+ ions make the main contribution to the luminescence sensitization of Yb3+ ions, while Cr4+ ions and to a lesser extent Cr5+ play the role of luminescence quencher and internal filter. Sensitization of Yb3+ luminescence through the charge transfer band in Cr(VI) was found. An alkaline glass doped with Cr and Yb upon excitation through the sensitizer produced a luminescence quantum yield of 32% and the conditions for its enhancement were considered. It is shown that the temperature quenching of luminescence of CrYb-containing glasses is significantly lower than that of Cr-containing glasses.

The use of glassceramics in photocatalysis is an attractive option for the realization of smart optical fibers and self-cleaning windows. Here we present the photocatalytic activity of germanosilicate glasses embedding Ga2O3 nanocrystals prepared by batch melting and glass heat treatment. The powdered material is used for UV-assisted degradation of rhodamine in water. The kinetics show changes after repeated experiments. In the first cycle, the apparent rate is governed by a second-order reaction with a Gaussian-like shape, whereas the second cycle follows a first-order reaction. The modification appears to be correlated with perturbations in the defect population. Photoluminescence has been used to monitor the evolution of such defects. Kinetic data on photoreactions and defect formation have been modelled in a combined frame in which the defect concentration determines the photocatalytic activity. The results prove the photocatalytic ability of the studied glassceramics. Moreover, the general validity of the kinetic model can be of interest for other systems in which the photocatalytic response depends on photoreactive species concentration.

The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence efficiency can be enhanced by changing the submicron-inhomogeneous structure of the initial glasses.

The effect of adding the oxide Nd2O3(0.1 – 3.0 mol.%) on the synthesis conditions, crystallization, and spectral properties of a thermostable Li2O–Al2O3–SiO2(LAS) sitall was studied. The introduction of up to 1 mol.% Nd2O3 no effect on the crystallization properties and the precipitation of the main crystalline phase of β-eucryptite-like solid solutions LixAlxSi1–xO2, whereas increasing the Nd2O3 molar content to 3% significantly changes the nature of the crystallization of LAS glass. The obtained results show that the optical sitalls with near-zero CLTE, activated by neodymium ions right up to the level $$ {N}_{\mathrm{Nd}}^{3+}\sim 4\times {10}^{20}{\mathrm{cm}}^{-3} $$ , can be regarded as a base for producing new light-emitting thermostable optical media.

Glass meeting the GOST requirements concerning stria-free category-1 optical glass was produced in the system Me2O–Ga2O3–GeO2–SiO2 (Me = Li, Na). The subsequent heat treatment results in the precipitation of γ-Ga2O3 nanocrystals in it and triggering of luminescence excited by only UV radiation in the solar-blind range. The integral visible-light transmission and luminescence intensity of the developed material are comparable with these characteristics of glass-crystalline samples for which the glass was obtained by the melt quenching method.

Gallium incorporation in silicate glasses gives rise to compounds in which the nucleation and growth of Ga-oxide nanostructures can be designer controlled so as to obtain a number of functional properties for photonic applications. However, despite planar geometry pertains to a large part of modern technology, no information is available yet on the scalability of Ga-oxide segregation mechanisms in oxide thin films. In fact, incorporated Ga-oxide nanostructures have only been obtained in bulk materials. Here we show that deposition of Ga-alkali-germanosilicate thin films by radiofrequency-plasma sputtering gives rise to Ga-oxide nanostructures incorporated in an amorphous matrix. X-ray diffraction, X-ray reflectivity, small-angle X-ray scattering, and atomic force microscopy data unveil the formation of lenticular nanoaggregates, only a few nm thick, even in as-deposited materials as a result of two-dimensional aggregation of spinel-like Ga2O3 nanoparticles. Importantly, the aggregate size distribution is controlled not only by the temperature but also by the film thickness when it is reduced from 102 nm to only a few nm. The results open the way to the design of oxide-in-oxide thin films with incorporated networks of nanostructures which can act as percolation paths for unconventional electric responses in neuromorphic functional systems.

Transparent germanosilicate glass-ceramics embedding γ-Ga2O3:Ni2+ nanocrystals have been fabricated. Optical amplification in the glass-ceramics was observed at ∼1.32μm under 0.96μm diode laser pumping in the 3A2g (3F) ↔ 3T2g (3F) resonance band of Ni2+ ions. The magnitude of the gain was estimated to be ∼13%.

The particulars of the effect of focused femtosecond laser pulses on antimony silicate glass with the composition 25Sb 2 O 3 ∙75SiO 2 % (molar content) in thermal and athermal regimes were studied. It was found that in contrast to quartz, alkali silicate, and some borosilicate glasses the birefringence of the form characteristic for the formation of nanogratings does not arise in the laser-modified zones of the studied glass. Weak birefringence with slow axis parallel to the polarization plane of the writing laser beam, accompanied by precipitation of crystalline phases, seemingly including the cubic modification of Sb 2 O 3 , arises in the modified zones under irradiation by 10 6 pulses with energy > 100 nJ and repetition frequency 10 and 200 kHz.

Ga-Oxide nano-segregation in alkali-germanosilicate amorphous films gives rise to a responsive material with nonlinear electric conduction and hysteretic charging mechanisms.

We report on design and fabrication of Ni2+-doped glass-ceramics from a low-alkali optical glass in Li2O-Na2O-Ga2O3-SiO2-GeO2 system by melting technique and subsequent thermally controlled nano-crystallization. The analysis of differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, absorption and fluorescence spectroscopy reveals, for the first time, the real possibility of optimizing the integrated intensity of Ni2+ near-infrared emission through controlled pre-treatments at temperatures of nanophase nucleation, with the enhancement up to a factor of four with respect to gallium germanosilicate glass-ceramics obtained without pre-treatments. Importantly, the effects on the light emission are shown to be related to the influence of pre-treatment on size and size distribution of the gallium oxide nanocrystals which result from subsequent crystallization at higher temperature.