Exothermic synthesis of ceramic materials based on barium and strontium aluminosilicates

Abstract

Ceramic materials were synthesized in the RO(R=Ba, Sr)–Al2O3–SiO2 system using exothermic synthesis from solutions containing barium and strontium nitrates, silica and organic reducing agents (glycine and carbamide). It was shown that only the use of a mixture of glycine and carbamide as well as the addition of ammonium nitrate allows carrying out a complete exothermic synthesis with the formation of an X-ray amorphous product with a small fraction of the crystalline phase. It was established that monophase materials based on barium and strontium aluminosilicates (BaAl2Si2O8 and SrAl2Si2O8) are formed when the obtained X-ray amorphous product is heat-treated at the temperatures above 10000C. Ceramics from synthesized materials sintered at 15500C has a high refractoriness, open porosity of 0–1.0%, compressive strength of 115–120 MPa; dielectric constant of 3.25–6.0 (at the frequency of 1 MHz) and the loss tangent of (1.5–5.2)10–3. The results shows that the exothermic synthesis ensures the preparation of nano- and sub-microcrystalline powders in the system RO(R=Ba, Sr)–Al2O3–SiO2. Materials based on the obtained aluminosilicates can be used in the manufacture of protective structures for devices operating in the radio frequency band, in radar installations of aviation and rocket technology, in microwave elements, etc.