Using crystal chemical data to estimate phase formation in the BeO−MgO−Al2O3−SiO2 system

Abstract

Crystallization of the beryllium indialite (Mg2BeAl2Si6O18) melt is investigated. Crystallization at high cooling rates and thermal gradients gives metastable compounds (petalite structural type, mullite, sapphririne); under slow cooling and in the absence of thermal gradients, stable beryllium indialite crystallizes. The main reason for that, suggested from structural motifs of the formed phases, is that most of the magnesium exists in the melt as MgO4 in the former case or as MgO6 in the latter case. The same (petalite) structural type crystallizes from liquates differing only in a ratio of type-forming elements. The composition of metastable phases is determined.