CITRATE ROUTE TO ULTRA-FINE BARIUM POLYTITANATES WITH MICROWAVE DIELECTRIC-PROPERTIES

Highly reactive and ultra-fine barium polytitanates (BaO-nTiO(2), n=4, 4.5, 5) with a particle size of 30-50 nm have been prepared by the citrate route. Solubility isotherms were calculated for the BaCO3-citric acid-H2O and TiO(OH)(2)-citric acid-H2O-H2O systems at 25 degrees C to predict the optimum pH condition for preparing pure and stable citrate complexes. Pure and well crystallized powders with monodispersive, nanometer-sized particles could be obtained by thermal decomposition of the optimally prepared citrate precursors at relatively low temperatures. Details of the crystallization process and particle characteristics of citrate-derived barium polytitanates are described. The sinterability and microwave dielectric properties of BaTi4O9 and Ba2Ti9O20 were also measured and are discussed briefly.