Phase formation and dielectric properties of Mg₂TiO₄-Al₂O₃

Abstract

Powder mixtures of end members in MgO-TiO₂-Al₂O₃ ternary system and those of binary (1−x)Mg₂TiO₄-xAl₂O₃ were prepared corresponding to 0≤x ≤0.5 in subsolidus tie triangle of MgTiO₃-Mg₂TiO₄-MgAl₂O₄ and the reaction sequence, sintering and dielectric properties of which were studied. In both cases, MgTiO₃(ε_r=17) as the second phase increased and the composition of the solid solution grains concurrently shifted toward MgAl₂O₄(ε_r=8) with increasing Al₂O₃ content, which resulted in sluggish decrease in ε_r. Significant difference in microstructure, however, was seen between the two methods probably due to the difference in the reaction sequences.