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

Abstract

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.