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This paper considers the coordination state of boron and aluminum ions in barium aluminoborate glass with a constant ratio of BaO : B 2 O 3 = 0.5 and a variable ratio of Al 2 O 3 : BaO = 0-3. The dependence of the concentrations of boron and aluminum atoms with a variable coordination number on the Al 2 O 3 content was estimated by IR, 11 B and 27 Al NMR spectroscopy. The nonlinear nature of the obtained dependences was attributed to variations in the aluminum oxide properties. At a content of less than 30 mol % Al 2 O 3 serves pri marily as a network former, while an increase in the Al 2 O 3 concentration results in its higher modifying role in the studied glass.

IR and RS spectroscopy are used to study the effect of substituting barium and calcium for the sodium cation on the structure of sodium borosilicate glass with the composition 0.25Na 2 O; 0.25B 2 O 3 ; 0.5SiO 2 . Analysis of the recorded spectra showed that the substitution of the alkali-metal cations Ba 2+ and Ca 2+ for the Na + cation results in breaking of B-O-B and Si-O-Si bridges, as a result of which the fraction of oxygen end atoms increases and the degree of polymerization of the glass decreases.Matrices based on borosilicate glasses with different composition, which have the advantages of high radiation resistance and simple fabrication technology, are now widely used to immobilize radwastes [1]. Even though these glasses have long been used as a matrix material, the search for optimal compositions remains unresolved and requires continued study of the structure and properties of borosilicate glasses with a wide spectrum of compositions.The objective of the present work was to study the effect of substituting calcium and barium for the sodium cation on the structure of sodium borosilicate glass with the composition (mole fraction) 0.25Na 2 O; 0.25B 2 O 3 ; 0.5SiO 2 . The structure of glass with this composition has been studied in detail experimentally in [2, 3] and theoretically in [4]. It has been established that the boron atoms in this glass can occupy ternary and quaternary coordination, the former are mainly flat symmetric triangles BØ 3/2 (Ø -oxygen bridge atom) in which all oxygen atoms are bridge atoms. The fraction of asymmetric triangles BØ 2/2 O -is small but measurable experimentally. The silicate component of the network of this glass is represented as Q 4 , Q 3 and, possibly, in very small amounts Q 2 units (Q n -silicon-oxygen tetrahedron with n oxygen bridge atoms). Thermodynamic modeling shows that the fraction of different types of structural units in glasses with the compositions studied is as follows [4]: BØ 4/2 (B 4 ) -0.152; BØ 3/2 (B 3 ) -0.173; BØ 2/2 O -(B 3-) -0.009; Q 4 (SiØ 4/2 ) -0.326; Q 3 (SiØ 3/2 O -) -0.336; Q 2 (SiØ 2/2 OO 2 -) -0.002.On the whole it is evident that the distribution of the sodium ions between the silicon-and boron-containing structural units is approximately proportional to the value K = SiO 2 /B 2 O 3 (2 : 1). The sodium ions compensate the charge of the borate tetrahedral and oxygen end atoms belonging to the silicate structural units. EXPERIMENTAL PARTTwo series of glasses were synthesized and studied in this work. In the first series, calcium cations were gradually substituted for sodium cations, while in the second series barium cations were substituted for the sodium cations. The glasses were synthesized from reagents: analytically pure SiO 2 , ultrapure B 2 O 3 , and chemically pure CaO, BaO, and Na 2 CO 3 . The initial reagents taken in the appropriate proportions were carefully mixed with alcohol in a porcelain mortar, dried at temperature 100 -150°C, and melted in a platinum crucible in an electric furnace with a nichrome heater at temperature...

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