Bioactive glasses have recently been extensively used to replace, regenerate, and repair hard tissues in the human body because of their ability to bond with living tissue. In this work, the effects of replacing Na₂O with MgO on the electrical, biosolubility, and thermal properties of the target glass 10Na₂O-60P₂O⁵-30CaO (in mol%) were investigated. The electrical properties of the glasses were studied with the impedance spectroscopy technique. At 473 K, DC conductivity values decreased from 4.21 x 10^-11 to 4.21 x 10^-12 S cm^-1 after complete substitution of MgO for Na₂O. All samples had a similar activation energy of the DC conduction process similar to 1.27 eV. Conduction mechanisms were found to be due to hop of ions: Na⁺, Mg²⁺ and probable H⁺. FTIR analysis showed that, as the Mg content increased, the Q² unit (PO₂^-) shifted towards higher wavenumbers. The proportion of Q³ unit (P₂O₅) decreased in the glass structure. This confirmed that the replacement of Na⁺ by Mg²⁺ was accompanied by concurrent polymerization of the calcium-phosphate glass network. The biosolubility test in the phosphate-buffered saline solution showed that the magnesium addition enhanced the biosolubility properties of Na₂O-CaO-P₂O₅ glasses by increasing their dissolution rate and supporting forming CaP-rich layers on the surface. The glass transition temperature increased, and thermal stability decreased substantially upon substitution of Na₂O by MgO.

Sodium-calcium-phosphate based oxynitride glasses and glass-ceramics doped with Mg, Si, and Nb were studied in vitro in simulated body fluid (SBF) under static conditions. The release of ions and pH changes up to 7 days of immersion were investigated. The nitrogen incorporation into phosphate glass matrix was found to notably influence in vitro dissolution only of homogenous glasses. Increasing the nitrogen content in the samples decreased the mean mass loss, while the niobate incorporation increased it. The correlation between the nitrogen content and increase in pH of SBF was also observed. The presence of phosphates crystallites was found to support the dissolution process at the beginning step (up to 3 days).

Oxynitride glasses are not yet commercialised primarily due to the impurities present in the network of these glasses. In this work, we investigated the microstructure and instinctive defects in nitrogen rich La-Si-O-N glasses. Glasses were prepared by heating a powder mixture of pure La metal, Si3N4, and SiO2 in a nitrogen atmosphere at 1650-1800 degrees C. The microstructure and impurities in the glasses were examined by optical microscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy in conjunction with electron energy-loss spectroscopy. Analyses showed that the glasses contain a small amount of spherical metal silicide particles, mostly amorphous or poorly crystalline, and having sizes typically ranging from 1 mu m and less. The amount of silicide was estimated to be less than 2 vol. %. There was no systematic relation between silicide formation and glass composition or preparation temperature. The microstructure examination revealed that the opacity of these nitrogen rich glasses is due to the elemental Si arise from the decomposition reaction of silicon nitride and silicon oxide, at a high temperature above similar to 1600 degrees C and from the metallic silicide particles formed by the reduction of silicon oxide and silicon nitride at an early stage of reaction to form a silicide intermetallic with the La metal.

Thin films in the aluminosilicate (AlSiO) system containing up to 31 at. % Al and 23 at. % Si were prepared by reactive RF magnetron co-sputtering in order to investigate the dependence of film formation and optical properties on substrate temperature and Si and Al contents. The obtained films were amorphous with smooth microstructure. The growth rate at different substrate temperatures ranged from 1.2 to 3.3 nm/min and increase with increasing the Si target power. The roughness decreases and thickness increases with increasing Si content. The thickness of the films grown at a deposition temperature of 100 °C is found to be higher than the films deposited at 300 and 500 °C. The AlSiO-coated glasses have a higher transmission in the visible region than the uncoated glass. The spectroscopic ellipsometry analysis reveals that the refractive index value decreased with decreasing the Al content, having extinction coefficient values of zero in the measured spectral region and band gap values ≥ 3.4 eV. The obtained thin films have over 90% transmittance in the visible range and no systematic variation of transmittance was observed with substrate temperature. The results suggest that glass substrate coated with AlSiO thin films have improved optical properties. 

In this work, glass-ceramics in the xBeO–20Fe₂O₃–(80-x)TeO₂ system with x = 0–25 mol% were synthesized by the traditional melt quenching route and studied by inductively coupled plasma optical emission spectroscopy, X-ray diffraction, confocal microscopy, infrared and Raman spectroscopy. BeO addition was found to support the crystallization process of Fe2O3 during melting, and an increased BeO content was associated with an increased fraction of the crystalline Fe₂O₃ phase and an increased size of these crystallites. Furthermore, samples doped with BeO exhibit an increasing polymerization of the residual tellurite glass network compared to the undoped sample. The magnetic properties and specific heat of all synthesized materials were measured, and the results show that all studied samples behave as spin-glasses. Also, the Morin transition of hematite was observed at 260 K with intensity depending on the material content in Fe₂O₃ crystalline phase, the formation of which correlates with the amount of added BeO.

Niobium doped biosolubility glasses in the Na–Ca–(Mg)–P–Si–O system were prepared by using an untypical two-step synthesis route. The parent glass was melted in air atmosphere at 1350 °C followed by re-melting the glass in Nb crucible with the addition of metallic Mg/Ca powder in the nitrogen atmosphere. The second melting step was carried out at 1450–1650 °C, using an induction furnace. The topography and structure of the obtained glasses were characterized by confocal microscopy, X-ray powder diffraction and infrared spectroscopic techniques. The chemical compositions were examined by energy-dispersive X-ray spectroscopy (EDS). The glasses were found to be of grayish color, X-ray amorphous and having network connectivity between ~ 2.5 and 2.7. The network connectivity of re-melted glasses was lower than the one of the parent glass. The glass structure consists of a highly disrupted silicate network of predominantly Q2 groups as well as isolated orthophosphate tetrahedra. The parent glass contains nanocrystallites consisted of apatitic PO₄³⁻ groups. The re-melted glasses contain non-apatitic or amorphous calcium phosphates. The obtained glass transition temperatures range from 530 to 568 °C and exhibit higher values for glassed doped with Ca metal. These glasses have improved thermal stability as compared to reference bioglasses. The biosolubility test in phosphate buffered saline solution (PBS) confirms that the glasses have biosolubility properties and HAp formation on the surfaces was observed.

Inspired by the work of John Duffy on optical basicity of oxyfluoride glasses, we apply here the conceptof optical basicity to oxynitride systems. While in the original work of Duffy and Ingram the basicity of amedium could be probed by s2 ions like Pb2+, the low energy intrinsic absorption edge of nitridecontainingsystems does not allow the use of such probe ions. This study uses therefore experimentaldata on refractive index and density of alkaline earth and rare earth containing silicate oxynitride glasses,prepared by the authors or taken from the literature. In addition, literature reports on experimental orcalculated refractive index, density and polarizability data are used to compare pure nitride systems, e.g.bulk or thin film materials that are either crystalline or glassy. We compare simple and complex nitridesystems with their oxygen counterparts, by calculating their optical basicity using the chemicalcomposition as well as the established relationship between optical basicity, L, and electronicpolarizability in oxide systems. Our results on oxynitride systems are in good agreement with Duffy’sprevious work on oxyfluoride glasses and indicate that the optical basicity varies for the isoelectronicanions in nitrides, oxides and fluorides (N3:O2:F) of a cation Mm+ as follows: L(MFm) = 1/2L(M2Om) =1/3L(M3Nm). Using this relation for CaO, for which the optical basicity was set as unity by Duffy andIngram, one has L(CaF2) = 0.50, L(CaO) = 1.00 and L(Ca3N2) = 1.50. The optical basicity of complexnitrides can therefore be calculated by the same method established for oxides using the equivalentfractions and the basicity of the constituent nitrides. The relationship between nitride polarizability aNand basicity L(nitride) was found to be linear, with L(nitride) = 0.39aN 0.14 where aN is given in Å3.

Laser melting techniques have been used in the preparation of unconventional glasscompositions with high melting temperatures. Thus, we wanted to test the feasibilityof using a CO2 laser in the preparation of nitrogen-rich oxynitride glasses and nitridesilicate glasses. Melting from oxides and metallic raw materials, we wanted to studyfirst glass formation and possible evaporation losses of the glass components. Twoglass series were prepared and studied for their structure and thermal properties, onewith Ca2+- and a higher melting La3+-doped soda-lime-silicate (SLS) series. In lessthan 3 minutes of laser melting, spheres of up to 6 mm diameter were successfullyfabricated. The obtained glass samples were homogeneous and transparent in thevisible region. X-ray diffraction and Raman spectroscopic analysis confirmed theamorphous nature of the synthesized samples. Sodium losses increase as calcium isadded to the soda-lime-silicate glass. As expected, increasing Ca2+ or La3+ additionlead to increased depolymerization of the silicate network. Moreover, the increasesin Tg with the addition of Ca2+ or La3+ ions indicating strengthening of the sodalime-silicate glass by increasing strength of the M-O bonds of divalent and trivalentions over monovalent sodium ions, weak Na-O bonds also resulting in significantevaporation loss during the short laser melting times. The thermal stability decreasesupon addition of Ca2+ or La3+ ions to the soda-lime-silicate glasses.

To stabilize the global temperature and mitigate climate change, the emission of anthropogenic greenhouse gases will have to be greatly reduced. To make it possible, the energy sector will have to transfer from fossil energy to environmentally friendly and carbon neutral sources.

Electrical properties of beryllium-alumino-silicate glasses containing sodium ions or sodium and lithium ions were studied with impedance spectroscopy technique over a frequency range from 10 mHz to 1 MHz and at temperature range from 213 to 473 K. The frequency- and temperature-dependent conductivity spectra of individual single alkali glasses were superimposed by means of the Summerfield scaling. Mixed-alkali glasses do not overlap into a single master curve. Glasses doped with sodium ions exhibit significantly higher values of D.C. conductivity and lower activation energy (~0.63 eV) than glasses doped with both sodium and lithium ions (~0.95 eV). The observed mixed-alkali effect can be described by the dynamic structure model (DSM). The conductivity pre-exponential factors and activation energy follow the Meyer-Neldel rule in both glass series. It was observed that the replacement of SiO₂ by BeO in single cation glasses resulted in decrease in activation energy and pre-exponential factor σ₀. In mixed cations glasses similar effect found for D.C. conduction process parameters was assigned to influence of both oxides BeO and Al₂O₃.