LOW-TEMPERATURE HYDROTHERMAL SYNTHESIS OF BA(MG1 3TA2/3)O-3 SOL-DERIVED POWDERS/

Powders of the microwave dielectric material barium magnesium tantalat e Ba(Mg1/3Ta2/3)O-3 have been produced by hydrothermal synthesis at mo derately low temperatures (160 to 350 degrees C). It was found that wh ile it is relatively straightforward to produce the material in the de sired perovskite phase at or below 200 degrees C, the powder particles tend to be highly irregular in morphology with extremely small dimens ions (of the order of 10 nm) and deficient in magnesium (with some pre cipitation of the excess magnesium as the hydroxide). The effects of b oth higher synthesis temperatures and different feedstock preparation were thus investigated with the aim of improving the precipitation of magnesium under hydrothermal conditions in order to produce a more hom ogeneous, stoichiometric powder and significant progress was made. It was found that when near-stoichiometric particles are formed, they ado pt rounded morphologies and exhibit larger particle sizes (around 30-5 0 nm). These results show that the hydrothermal feedstock and the synt hesis temperature used have a profound effect on particle stoichiometr y, which in turn affects the growth morphology of the particles.