Heat-resistant ceramics of -eucryptite composition was synthesized in the current work. To this end, the method of ceramics production was combined with the principle of reactive formation of the material structure. Taking into account the calculated data about the compositions of eutectics and temperature of their melting in the specific binary systems Li 2 O2SiO 2-Li 2 OÀl 2 Î 3 2SiO 2 and Li 2 O2SiO 2-Li 2 OÀl 2 Î 3 4SiO 2 , a comparatively low-melting glass was developed in the system Li 2 O-Àl 2 Î 3-SiO 2 (with a melting temperature of 1250 0 Ñ). Its function in the composition consists in the intensification of the processes associated with the formation of the crystalline phase of -eucryptite and sintering of the ceramic material as a whole. Based on the results of experimental study, we concluded that the duration and temperature of sintering of ceramics directly determine its microstructure and physicotechnical properties. In order to achieve the complex of the highest indices, the firing of eucryptite ceramics should be performed at the temperature of 1350 0 Ñ with the isothermal time of 3 h. -eucryptite phase is formed as the distinct prismatic crystals of hexagonal shape with a size of 4-7 m. The developed composition of eucryptite ceramics allows obtaining the products or individual elements with varying complexity of shapes, which significantly reduces the amount of rejects.

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In the synthesis of heat-resistant ceramics in the system BaO–Al2O3–SiO2 (BAS), it is important to find ways of intensifying the process of transition of hexagonal celsian to monoclinic celsian without an increase in sintering temperature. Monoclinic form of celsian is characterized by higher thermal, electro-insulating, and mechanical properties. This paper deals with the features of formation of the phase composition of celsian ceramics when using BAS glass of eutectic composition and glass in the system Li2O–Al2O3–B2O3–SiO2 (LABS) of spodumene composition as modifying components. It is shown that monoclinic celsian is the final crystalline phase formed in ceramics synthesized on the basis of barium carbonate and kaolin. Monoclinic celsian is formed stepwise; and the hexagonal celsian appears first. The complete transition hexagonal celsianmonoclinic celsian occurs only in the process of high temperature firing at 12500C. Notably, the degree of ceramic sintering remains low (water absorption is 11.0%). Introduction of BAS glass contributes to the complete transition of hexagonal celsian to monoclinic celsian at a reduced temperature of 11000C. Maximum effect in the formation of monoclinic celsian is achieved by the introduction of LABS glass. As a result, the temperature of formation of this modification maximally decreases to 8000C. In this case, complete sintering of celsian ceramics is achieved at the temperature of 12500С.

The search for effective modifiers of the structure of densely baked cordierite ceramics to reduce the firing temperature is a relevant task but typically requires a large amount of experimental research. The object of this study is the reaction of the formation of the cordierite phase with the participation of glass components of the eutectic compositions of the MgO– Al2O3–SiO2 system under low-temperature firing conditions. In this case, thermodynamic analysis was used as a tool to assess the probability of chemical reactions. Thermodynamic analysis can significantly reduce the volume of the experimental sample. This paper reports the results of theoretical and experimental studies into the features of the course of chemical reactions with the participation of glass components of eutectic compositions of the MgO–Al2O3–SiO2 system. It was revealed that once the stoichiometric ratio is maintained, the resulting product of the interaction between the components of eutectic glasses of the MgO–Al2O3–SiO2 system with charging components is cordierite. Changes in the mineralogical composition of cordierite compositions depending on the firing temperature have been determined. The formation of the cordierite phase is preceded by the process of transformation of meta kaolinite Al2O3·2SiO2, which is a product of kaolin dehydration, into mullite 3Al2O3·2SiO2. Subsequently, the formation of cordierite (in addition to crystallizing directly from eutectic glasses) occurs with the participation of the mullite phase. The formation of the cordierite phase occurs in several stages and is completed at a temperature of 1300 °C. The established features of the reactions of cordierite formation make it possible to determine the most optimal compositions for glasses  of the MgO–Al2O3–SiO2 system to obtain low-temperature cordierite ceramics with a high degree of sintering. At the same time, it is also possible to control the phase composition of ceramics and its properties