Uniform Coating of Nanometer-Scale BaTiO^sub 3^ Layer on Spherical Ni Particles via Hydrothermal Conversion of Ti-Hydroxide

A uniform BaTiO3 nano layer was coated on spherical Ni particles for multilayer ceramic capacitor applications via a Ti-hydroxide coating using the controlled hydrolysis of a TiCl4 butanol solution containing (C2H5)2NH (diethylamine, DEA) and its subsequent hydrothermal reaction at various [Ba(OH)2], residual [DEA], and hydrothermal temperatures. The hydrothermal conversion was successful at [Ba(OH)2]>=0.065M (Ba/Ti>=1.3) and T>=150 degree C, and the residual DEA in the Ti-hydroxide coating layer not only affected the formation of the BaTiO3 phase but also resulted in a rough surface morphology. When a minimal amount of DEA was involved in the formation of Ti-hydroxide, a uniform BaTiO3 coating with a clean surface morphology could be attained, which was confirmed by elemental mapping of the coated powder and the observation of hollow spheres after removing the Ni core. The BaTiO3 coating was very effective not only in preventing Ni oxidation but also in shifting the starting point of Ni densification to a higher temperature. [PUBLICATION ABSTRACT]