Crystallization and dielectric properties of oxyfluoride aluminosilicate glasses added with Na2O

Mineralizers can efficiently promote the transition of barium aluminosilicate (BaAl2Si2O8, BAS) from hexacelsian to celsian (H-M). However, the detailed mechanism regarding the phase transformation of BAS is still unclear, especially in different glass systems. Herein we systematically studied the crystallization behaviors of SiO2-Al2O3-BaF2 glass in supercooled oxyfluoride aluminosilicate liquids with increasing Na2O concentration, and the influence of crystal phases precipitated from the precursor glass on the dielectric properties of oxyfluoride aluminosilicate glass ceramics was analyzed. We observed that the high addition of Na2O promoted no transformation of H-M, but resulted in the precipitation of second phases (e.g., NaAlSi2O6, Ba3AlF9). Our results provide guidance for designing glass ceramics containing celsian (Monoclinic BAS) nanocrystals with superior thermodynamically stable and dielectric characters.