Synthesis and characterization of Celsian by solid-state reaction process from mullite

Monolithic barium aluminosilicate (Celsian), with good thermal shock resistance, high thermal stability, and strong versatility, is attractive material as a ceramic matrix for high-temperature composites. However, Celsian cannot be precipitated directly during the synthesis process but can only be generated by crystallographic transformation of the metastable Hexacelsian at high temperatures, and this process is sluggish. In this study, mullite was chosen as the main raw material for the synthesis of Celsian with almost fully monoclinic through a simple one-step solid-state reaction process at a lower temperature and shorter time, which was investigated using differential thermal analysis, phase identification, microstructure observation, and FactSage thermodynamic calculations. The results showed that mullite is a favorable raw material for the synthesis of Celsian, effectively avoiding the appearance of BaAl2O4 in Hexacelsia, making it possible to synthesize Celsian with almost fully monoclinic with only 4.5 h of holding at 1300 & DEG;C. This is a significant improvement compared to the higher temperatures and longer holding times required for the synthesis of Celsian from other raw materials, according to previous literature.