Vol 45, No 2 (2019)

In 2008, V.Ya. Shevchenko and S.V. Krivovichev built the zeolites series related to paulingite based on the inorganic gene concept and predicted a new zeolite named ISC-1 (Institute of Silicate Chemistry-1) [1]. The structure and composition of ISC-1 are described in detail in [2]. The found chemical formula of the new zeolite ISC-1 is Na₁₄K₂₄Al₃₈Si₂₀₂O₄₈ · nH₂O. Further research on the principles of assembly of zeolites and prediction of another previously unknown zeolite, ISC-2 (Institute of Silicate Chemistry-2), and the conditions of its formation are presented in [3–5]. The combinatorial-topological analysis of the crystal structure of the new aluminosilicate zeolite ISC-1 with cubic cell parameters а = 25.039 Å, V = 15 699 ų, and spatial group Im\(\bar {3}\)m is performed by computer-based methods (ToposPro software package) [6]. The topological type of the framework composed of bonded Т–(Si,Al)O₄ tetrahedra is characterized by a combination of polyhedral tilings: t-grc (48 T-atoms), t-pau (32 T-atoms), t-plg (30 T-atoms),t-opr (16 T- atoms), and t-oto (16 T- atoms). A framework-forming precursor for zeolites of 30 T-tetrahedra, which corresponds to the t-plg tile and contains an organic template Me₂-DABCO (N,N′-dimethyl-1,4-diazabicyclo[2.2.2]octane), is established by the complete decomposition of the 3D atomic lattice into cluster structures. t-plg nanoclusters with the symmetry g = \(\bar {3}\)m are characterized by 4-, 6-, and 8-rings and the n-hedral symbol [4⁶. 6². 8⁶]. Na-spacers statistically occupy neighboring positions in the 8-ring and between the 4‑rings of the neighboring t-plg clusters. The basic 3D lattice type indicative of t-plg clusters center-of-gravity positions correspond to a simple cubic lattice with CN = 6. The self-assembly code of the 3D structure from complementary bonded nanoclusters-precursors is simulated in its entirety: primary chain → microlayer → framework. The doubled distance between t-plg clusters centers corresponds to the cubic cell translation vector a = 25.039 Å.

The luminescence properties of bismuth-containing high-silica glass obtained after impregnating matrices of porous glass in nitrate solutions of bismuth nitrate pentahydrate for 24–48 h followed by heat treatment in the range from 400 to 890°C are studied. It is found that the concentration of Bi(NO₃)₃ in the impregnating solution affects the content of bismuth in the synthesized samples stronger than the duration of the impregnation and the temperature of the heat treatment. It is established that all the samples studied in this work have blue-green luminescence (λ_em = 420–520 nm at λ_exc = 300 nm) caused by the presence of Bi³⁺ ions. When the concentration of bismuth in the samples is increased a long-wavelength shift of the luminescence band maximum is observed. When the heat treatment temperature is increased a shortwave shift is observed. A yellow-orange luminescence with the maximum in the λ_em range of 576–582 nm (λ_exc = 480 nm) caused by the presence of Bi²⁺ ions is observed for the samples with a high bismuth content (1.17–1.18 wt % of Bi₂O₃) heat-treated in air at ~700 and 750°C.

In the present research work Se₇₅Te₁₃In₁₂ chalcogenide glass has been prepared by melt quenching technique. The non-isothermal Differential Scanning Calorimetry (DSC) measurement of synthesized alloy has been executed at constant heating rate of 25 K/min. The glass transition temperature (T_g), crystallization temperature (T_c) and melting temperature (T_m) are found to be 349, 376 and 533 K, respectively. Thin films of 400 nm thickness of Se₇₅Te₁₃In₁₂ alloy were prepared by thermal evaporation technique. To study the phase transformation, the thermal annealing was done at two different temperatures 353 and 363 K for 2 h in a vacuum furnace under a vacuum of 10^–3 Torr. Optical measurements were done for as-prepared and annealed films. The optical band gap is found to decrease with increasing annealing temperature. The transformed phases of as grown and thermally annealed films were analyzed by High Resolution X-ray diffraction (HRXRD) and Field Emission Scanning Electron Microscope (FESEM).

Effects of ZnO-B₂O₃ (ZB) addition have been investigated on the sintering behavior, structure and microwave dielectric properties of CaLa₄Ti₄O₁₅ ceramics. The sintering temperature of CaLa₄Ti₄O₁₅ ceramics with a very small amount of ZB addition such as 0.2 and 0.5% is obviously reduced from 1550 to 1375°C, and the sintering temperature range is significantly broadened to 1350–1450°C. With the increase of ZB addition, the secondary phases of CaLa₄Ti₅O₁₇ and LaBO₃ are observed in these ceramics. Not only sintering behavior but also microwave dielectric properties of CaLa₄Ti₄O₁₅ ceramics have been enhanced by a small amount of ZB addition. Excellent microwave dielectric properties of ε = 42.7, Qf = 46.678THz, τ_f = –3.5 ppm/°C are achieved for the CaLa₄Ti₄O₁₅ ceramics with 0.5% ZB addition sintered at 1375°C.

The possibility of applying glycerin and other alternative substances (acetic acid, gelatin, starch, saccharose, and paraffin) in as a pore-forming agent for the synthesis of foam glass is investigated. A composition consisting of a batch mixture based on colorless container BT-1 glass and suggested pore-forming agents is calculated and the thermal treatment of these mixtures is performed. According to the processed experimental data on the density and porosity, an original parameter is introduced which allows characterizing the homogeneity of the porous structure; the criteria for selecting an organic substance as a pore-forming agent are also proposed.

The thermal behavior of antiferromagnets FeBO₃ and Fe₃BO₆ is investigated according to the low-temperature powder X-ray diffraction data. Unit cell parameters were refined by the Rietveld method. The coefficients of thermal expansion are calculated. The interrelation between the expansion and crystal structure is described.