Structure and crystallization behavior of glasses in the BaO–B2O3–Al2O3 system (original) (raw)
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Structure and nonisothermal crystallisation of glasses in the BaO–B2O3–TiO2 system
The structure and devitrification behaviour of barium borotitanate glasses, examined by Fourier transform infrared spectroscopy, differential thermal analysis and x-ray diffraction, are reported. Glass compositions are expressed by the formula: (50-x/2)BaO.(50-x/2)B 2 O 3 .xTiO 2 with x=4, 8 and 16. Titanium acting as glassformer gives a more polymerised structure increasing the glass stability with respect to devitrification. The nonisothermal devitrification of the studied glasses occurs in one or two steps depending on the TiO 2 content in the glass composition and the specific surface area of the sample. The surface crystallisation was found to be dominant for all glasses. The investigated glasses devitrify forming b-BaB 2 O 4 microcrystals as the main crystalline phase.
Crystallization of Glasses Containing K2O, PbO, BaO, Al2O3, B2O3, and TiO2
Crystals
The objective of this work was to obtain glass-ceramics from stable glasses, with a composition of barium, lead, and potassium titanate phases, for use as semiconductors. For this purpose, the glass-ceramic technique was used to control crystal growth and obtain a fine-grained microstructure. Various glasses containing K2O, PbO, BaO, Al2O3, B2O3, and TiO2 were prepared using a melt-quenching method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed a single amorphous phase of all samples. Infrared spectra confirmed the presence of B-O bonds stretching vibrations of (B3O6)3− boroxol rings and BO3 triangles, as well as Ti-O stretching vibrations of (TiO6/2) and (AlO6/2) octahedral units. Thermal analyses confirmed the presence of one or more crystallization peaks in the range of 700 to 744 °C. On this base, they were heat-treated to promote crystal growth. XRD and SEM detected Ba4Ti12O27, Ti7O13, and BaTiO3 phases, homogeneously distributed throughout the material ...
Glass formation and structure of glasses in B2O3―Bi2O3―MoO3 system
Journal of Non-Crystalline Solids, 2011
The purpose of this paper is to study the glass formation tendency in the ternary system B 2 O 3-Bi 2 O 3-MoO 3 and to define the main structural units building the amorphous network. A wide glass formation area was determined which is situated near the Bi 2 O 3-B 2 O 3 side. A liquid phase separation region was observed near the MoO 3-B 2 O 3 side for compositions containing below 25 mol% Bi 2 O 3 and their microheterogeneous structure was observed by SEM. The phase formation was characterized by X-ray diffraction (XRD). By DTA was established the glass transition temperature (T g) in the range of 380-420°C and crystallization temperature (T x) vary between 420 and 540°C. The main building units forming the amorphous network are BO 3 (1270 and 1200 cm − 1), BO 4 (930-880, 1050-1040 cm − 1), MoO 4 (840-760 cm − 1) and BiO 6 (470 cm − 1). It was proved that Bi 2 O 3 favors the BO 3 → BO 4 transformations while MoO 3 preserves BO 3 units in the amorphous network.
Crystallization kinetics of BaO–Al2O3–SiO2 glasses
Journal of Materials Research, 1989
Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system have been studied by differential thermal analysis (DTA), x-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt. %) 10BaO–38Al2O3–51SiO2–1MoO3 (glass A) and 39BaO–25Al2O3–35SiO2–1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3 · 2SiO2) and hexacelsian (BaO · Al2O3 · 2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 °C. It undergoes structural transformation into the orthorhombic form at ∼300 °C accompanied by a large volume change which is undesirable for structural app...
Thermal behavior and the properties of BaO–B2O3–P2O5 glasses
Journal of Thermal Analysis and Calorimetry, 2016
Borophosphate glasses of the BaO-B 2 O 3-P 2 O 5 ternary system were prepared and studied within the large glass-forming region of the system. Fourteen investigated glass samples of barium borophosphate glasses were discussed for a comparison of the compositional trends in their properties in four compositional series such as A: (100x)Ba(PO 3) 2-xB 2 O 3 , B: 40BaO-yB 2 O 3-(60y) P 2 O 5 , C: (50z)BaO-zB 2 O 3-50P 2 O 5 , and D: (60w)BaO-wB 2 O 3-40P 2 O 5. Changes in glass density and molar volume primarily depend on the BaO content in the glasses. The thermal properties were studied with a differential thermal analysis, hot-stage microscopy, and dilatometry. Glass transition temperature increases with a rising B 2 O 3 content most rapidly in the glass series A and B. It reaches its maximum in these series for the glasses containing 20-30 mol%, where the glass network represents a 3D structure interlinked with P-O-B, P-O-P, and B-O-B bridges. The thermal expansion coefficient decreases, in contrast, with the increasing B 2 O 3 content in these ternary glasses as well as their chemical durability. The crystallization of these glasses, in the samples with a low B 2 O 3 content, results in the formation of barium metaphosphate BaP 2 O 6. Certain crystallized samples also contain a small amount of BPO 4 , and diffraction lines of ternary compounds BaBPO 5 and Ba 3 B(PO 4) 3 were revealed in a number of samples. A new compound of the composition Ba 5 B 2 P 8 O 28 was identified in the crystallized glass 50BaO-10B 2 O 3-40P 2 O 5 .
Optical and structural properties of BCBS glass system with and without alumina
Physica B: Condensed Matter, 2018
BaO-CaO-Al 2 O 3-SiO 2 (BCAS) glass and their derivatives have gained extreme importance for their high endurance to elevated temperatures and being suitable for various electrochemical applications. Two glass systems, one being 50mol% [SiO 2-B 2 O 3 ]-xBaO-(45x)CaO-5Al 2 O 3 called as BCBSA and another without Al 2 O 3 termed as BCBS were synthesized using melt quenching technique in the present work. Addition of ZnO and MgO as flux helped in melting them at 1300 ᴼC which is much lower than the usual melting temperature of these glasses [1-4]. Density of the quenched glasses was measured by Archimedes method and structural bond vibrations were confirmed through FTIR. UV Visible spectroscopy was used to determine band gap energy and confirm the insulating nature of the synthesized glasses. The samples were isothermally heated at 700 ᴼC, 800 ᴼC for 50 hours and at 900 ᴼC for 50 and 100 hours duration in air to allow the devitrification process to take place. The heat treated samples were analyzed by X-ray diffraction to identify the developed phases. Five Al 2 O 3 free samples synthesized at 1300 ᴼC by regular melt quenching technique were found to be devoid of the monocelsian phase. This is a detrimental phase for high temperature sealant applications as it has a very low coefficient of thermal expansion (CTE). Al 2 O 3 free BCBS glasses, properties of which are being reported for the first time and glasses with low BaO concentrations are found to meet the requirements for high temperature applications as sealants in Solid Oxide Fuel Cell (SOFC).
Structural Characterization of Borotellurite and Alumino-Borotellurite Glasses
Borotellurite (xB2O3-(100-x)TeO2; x= 15, 20, 25, 30 and 35 mol%) and alumino-borotellurite (yAl2O3-10B2O3-(100-y)TeO2; y= 5, 10, 20 and 30 mol%) glasses are prepared and studied by X-ray diffraction, density, differential scanning calorimetry, thermo-gravimetric analysis, UV-visible, infrared and Raman spectroscopy. Borotellurite glasses are hygroscopic and on crushing into powder, they absorb atmospheric water vapors to form crystalline precipitates of TeO2 in an amorphous matrix; the chemical durability of these glasses deteriorates with increasing B2O3 concentration. Refractive index of borotellurite glasses decreases from 2.29 to 2.26 while the glass transition temperature increases from 339 to 366oC with increase in B2O3 mol%. The short-range structure of glasses consists of TeO4, TeO3, BO4 and BO3 structural units. Using the ratio of the areas under TeO4/TeO3 and BO4/BO3 Raman and infrared bands respectively, the Te-O coordination is found to decrease from 3.63 to 3.56 and B-O co-ordination from 3.34 to 3.17 respectively on increasing B2O3 concentration from 5 to 30-mol%. Alumino-borotellurite glasses show an amorphous-amorphous phase separation at alumina concentration of 10-mol% and above, while alumino-borotellurite sample with 30-mol% of Al2O3 form crystalline precipitates of a-Al2O3 in an amorphous matrix.
2013
By controlled crystallization of glass samples from BaO-B 2 O 3-TiO 2 system glass ceramics can be obtained, based on borates and barium titanate (β-BaB 2 O 4 and BaTiO 3), with potential uses in electronics and electrical engineering. In this paper are presented the obtaining and some properties of glasses from the ternary system BaO-B 2 O 3-TiO 2 , containing B 2 O 3 between 20 and 50 molar%. For the obtained samples were determined density, thermal expansion coefficient, micro hardness, viscosity and hydrolytic stability. Determinations were also made by differential thermal analysis (DTA). The variation of the determined properties according to the oxide glass composition was explained. Prin cristalizarea controlată a probelor de sticlă din sistemul BaO-B 2 O 3-TiO 2 se pot obţine vitroceramici pe bază de boraţi şi titanaţi de bariu (β-BaB 2 O 4 şi BaTiO 3), cu potenţiale utilizări în electronică şi electrotehnică. În această lucrare sunt prezentate modul de obţinere precum şi o...