Fluorochalcogenide glasses

A new variety of chalcogenide vitreous materials—fluorochalcogenide glasses—have been synthesized by the introduction of sodium, thallium, lead, manganese, and bismuth fluorides into the Ga₂S-GeS₂ system. These glasses are characterized by high glass transition temperatures (560–670 K), an optical transmittance up to 75% in the visible (from 0.48 μm) and IR (to 7.5 μm) spectral ranges, chemical durability in reactive acid media, low crystallization ability, and the stability of physicochemical and optical properties. Depending on the introduced fluoride, the glasses can be dielectrics, semiconductors, or ionic semiconductors. The spectral investigation of fluorochalcogenide glasses by using the X-ray emission, Raman, NMR, and EPR spectroscopy reveals the complex features of their structure. The metal cations form bonds with sulfur in different structural positions. The glass network providing the mobility of sodium ions is formed in sodium fluoride-containing glasses. The formation of groupings of the [≡Ga ← F-Ge≡] type is the main structural feature of fluorochalcogenide glasses.     

Perlite-based glasses

The dilatometric, viscosity, crystallization, and melting properties of glasses based on local raw materials mined in Armenia were studied. The glass compositions thus developed are claimed to be suitable for the manufacture of wide- and narrow-neck containers. Translated from Steklo i Keramika, No. 10, pp. 12–13, October, 1997.     

Oxyhalide silicate glasses

The data available in the literature on the properties and structure of silicate glasses containing halides are reviewed. The results of measurements of thermal, electrical, and chemical characteristics that illustrate effects associated with the incorporation of halogens (fluorine, chlorine) into the silicate glass matrix are summarized. Different concepts regarding the mechanisms of halogen incorporation are analyzed, and the structural role of halogens in glasses is discussed. The factors responsible for the volatilization of halogens in the course of synthesis and specific features of their dissolution in silicate melts are considered.     

Terbium-doped fluoroaluminate glasses

A study was undertaken into vitrification in terbium-doped glasses. It was found that it is possible to produce glass with 12.8 mole % TbF₃ on substituting terbium for yttrium. The physicochemical and luminescence properties of the glasses under photo-and x-ray excitation were investigated. It was shown that terbium-doped oxygen-free fluoroaluminate glasses efficiently convert x-rays to visible light. Translated from Steklo i Keramika, No. 3, pp. 3–6, March, 1997.     

Cluster-assembled metallic glasses

A bottom-up approach to nanofabricate metallic glasses from metal clusters as building blocks is presented. Considering metallic glasses as a subclass of cluster-assembled materials, the relation between the two lively fields of metal clusters and metallic glasses is pointed out. Deposition of selected clusters or collections of them, generated by state-of-the-art cluster beam sources, could lead to the production of a well-defined amorphous material. In contrast to rapidly quenched glasses where only the composition of the glass can be controlled, in cluster-assembled glasses, one can precisely control the structural building blocks. Comparing properties of glasses with similar compositions but differing in building blocks and therefore different in structure will facilitate the study of structure–property correlation in metallic glasses. This bottom-up method provides a novel alternative path to the synthesis of glassy alloys and will contribute to improving fundamental understanding in the field of metallic glasses. It may even permit the production of glassy materials for alloys that cannot be quenched rapidly enough to circumvent crystallization. Additionally, gaining deeper insight into the parameters governing the structure–property relation in metallic glasses can have a great impact on understanding and design of other cluster-assembled materials.     

Theory of glasses

It is argued that is possible to define a ‘perfect glass’ which is both preparable experimentally and understandable theoretically. Some basic conditions and statistical thermodynamics are derived. Polymerized glasses are complex substances but it is argued that progress may be possible by considering them to have short range properties, and long range properties. Examples are given of models of glasses with such properties and their behaviour is shown to be amenable to theory.