Features of formation of the celsian phase during firing of heat-resistant ceramics in the system BaO–Al2O3–SiO2

Abstract

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.

Determining patterns in the formation of cordierite phase during the synthesis of density-sintered low-temperature ceramics based on glasses of the MgO–Al2O3–SiO2 system

“…To achieve the required level of high-temperature resistance of materials, it is advisable to use alkaline-free or low-alkaline aluminosilicate systems. In this case, heat-resistant materials are made on the basis of BaO-Al 2 O 3 -SiO 2 (BAS) and SrO-Al 2 O 3 -SiO 2 (SAS) systems, which contain the crystalline phases of monoclinic celsian [8] and strontium anorthite [9]. These materials can operate in the temperature range exceeding 1100 °C.…”