Reaction kinetics, sintering characteristics, and ordering behavior of microwave dielectrics: Barium magnesium tantalate

Abstract

The formation process of Ba(Mg_1/3Ta_2/3)O₃ was confirmed to be a direct reaction between constituent compounds without the presence of intermediate compounds. Isothermal analysis of reaction kinetics indicated the controlling reaction to be a three-dimensional diffusion process. Based on the Ginstling–Brounshtein model, the activation energy of the formation process was estimated to be 257 kJ/mol. A new definition of the ordering parameter for Ba(Mg_1/3Ta_2/3)O₃ was deduced to quantitatively evaluate the ordering degree. Raising sintering temperatures resulted in an increase in the ordering degree and bulk density of Ba(Mg_1/3Ta_2/3)O₃. Reducing the barium content in Ba(Mg_1/3Ta_2/3)O₃ substantially resulted in improved densification and enhanced ordering structure. On the other hand, an excess barium content in specimens hindered the progress of sintering, and also induced the disordering structure.