Preparation and properties of Nb-coated barium titanate composite particles by surface modification with Nb alkoxide in hydrophobic solvent

Chemical processing for the preparation of Nb-coated barium titanate composite particles was investigated using surface modification technology, hydrolyzing Nb ethoxide on the surface of barium titanate particles dispersed in hydrophobic solvent. It was confirmed from the measurements of specific surface area and zeta potential as well as SEM, TEM and EDX observations of the resulting composite particles that the original barium titanate particles were coated uniformly with hydrolysis product of Nb ethoxide. Barium titanates coated with 1 wt% of Nb as oxide were well sintered at 1200-1300 degrees C. The dielectric constants of the sintered barium titanates showed flattened temperature dependence, but it depended upon the average particle size of original barium titanate. The sintered bodies of Nb-coated barium titanate powders with average particle size of similar to 0.2 mu m gave dielectric constants of 2000-3000 and those of barium titanate with average particle size of similar to 0.5 mu m showed dielectric constants of 3000-4000 at room temperature. The microstructure of the sintered barium titanate coated with Nb oxide consisted of grains of about 1 mu m, smaller than those of sintered original barium titanate.