Anorthite porcelain: synthesis, phase and microstructural evolution

In the present study, anorthite (CaAl2Si2O8) porcelain was fabricated using Ca(OH)2, Al(OH)3, quartz, aluminous cement and feldspar as raw materials. Two compositions were formulated (coded as CAQ and CFQ) and their physico-mechanical properties (%AP, BD, flexural strength) were studied and compared. CAQ (21.2 wt% Ca(OH)2, 44.5 wt% Al(OH)3 and 34.3 wt% quartz) shows very poor densification and strength even after heating at 1450°C, although anorthite formation is observed on heating it at various temperatures. On the other hand, CFQ (48.6 wt% aluminous cement, 29.37 wt% feldspar and 22.06 wt% quartz) achieved full densification and superior strength at 1450°C with more anorthite formation compared to CAQ. X-ray diffraction and scanning electron microscope studies were also carried out to analyse the phase and microstructure evolution. The coefficient of thermal expansion of the anorthite-based sample was found to be lower than quartz and mullite porcelain which suggests its application as cooking ware.