Homogeneous precipitation synthesis and sintering behavior of microwave dielectrics: Ba(Mg1/3Ta2/3)O3

Barium magnesium tantalate (Ba(Mg1/3Ta2/3)O3) has been successfully prepared by a new homogeneous precipitation process. The presence of chlorine species in the precipitates results in direct formation of Ba(Mg1/3Ta2/3)O3 after 100°C drying, as well as rapid thermal expansion and cracking of specimens above 1300°C. When chlorine species are completely removed from the precipitates, Ba(Mg1/3Ta2/3)O3 starts to form from 600°C, and the desired pure phase is achieved after 900°C calcination for 2 h. With appropriate calcination followed by sintering at 1690°C, densified crack-free Ba(Mg1/3Ta2/3)O3 ceramics are achieved. In comparison with conventional solid state reactions, the new precipitation process developed here not only reduces the temperature of formation of superlattice structure, but also significantly increases the ordering parameter. This precipitation process is believed to be able to effectively suppress segregation of cations and enhance the compositional homogeneity of precursors, thereby facilitating an orderly arrangement of B-site cations in Ba(Mg1/3Ta2/3)O3.