Patterns in the Synthesis Processes, the Microstructure and Properties of Strontium Anorthite Ceramics Modified by Glass of Spodumene Composition

Abstract

To create heat-resistant structural materials capable of operating at high temperatures (up to 1,400 °C), glass crystalline materials based on the SrO–Al 2 O 3 –SiO 2 system are promising. This paperreports the results of studying strontium-anorthite ceramics modified with boron-containing glass of the spodumene composition. It was established that in order to achieve a set of high physical and technical indicators of ceramics at reduced firing temperatures (1,200‒1,300 °C), it is necessary to introduce glass in the amount of 20‒30 % by weight. In this case, densely baked materials with low TCLE values were obtained (32.0–33.4)·10 -7  degrees -7 , which predetermine their high thermal resistance (not lower than 850 °C). The principal crystalline phase of the examined ceramics is a monoclinic modification of strontium anorthite that mainly forms its microstructure. The strontium anorthite crystals measuring from 1‒2 µm to 3–4 µm are tightly connected via thin layers of the residual glass phase. In the glass phase, the β-spodumene crystals the size of 0.1–0.3 µm are evenly distributed. The observed microstructure features of ceramics determine zero values of water absorption and open porosity, as well as high density values (2.40–2.50 g/cm 3 ) and mechanical compression strength values (237–246 MPa). The dense microstructure also makes it possible to achieve high dielectric indicators (e=4.4–4.8; tgδ=0.005–0.007) in an ultra-high-frequency electromagnetic field. Therefore, the designed materials are promising as radio-translucent materials, including structural ones. In addition, the enrichment of the residual glass phase with the refractory components of the SAS system in the process of firing the examined ceramics predetermines its increased resistance to high-temperature heating during operation