Citrate route to ultra-fine barium polytitanates with microwave dielectric properties

Highly reactive and ultra-fine barium polytitanates (BaO-nTiO2, 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-H2O2-H2O systems at 25 °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.