Crystallization Kinetics of Barium Strontium Titanate Glass-Ceramics

Barium strontium titanate has been targeted as one potential ferroelectric glass-ceramic for high energy density dielectric materials. Previous testing has shown that the dielectric constant of these materials was as high as 1000 and dielectric breakdown strength up to 800 kV/cm. This did not, however, result in exceptional energy density (~ 0.90 J/cm3). In order to increase overall energy density refining agents can be added to the melt, but the nucleation and growth of the ceramic particles can also play a role. Therefore, in this study the crystallization kinetics were observed to more fully understand how the barium strontium titanate (BST) phase forms so that the optimal energy density could be achieved. It was found that the activation energy was 400 -430 kJ/mol, while the average Avrami parameter was 2.2 -2.5 for BST 70/30 with various additives. The activation energy is close to the disassociation of the Si-O bonds, while crystallization most likely occurs in the bulk with the mechanism of growth being interface controlled.