Fabrication of homogeneous nanosized nickel powders using a planetary ball mill: Applications to multilayer ceramic capacitors (MLCCs)

Given the increasing demand for multilayer ceramic capacitors (MLCCs) for miniaturization of electronic parts, a narrow nanoparticle size distribution is crucial to optimize MLCC performance and stability. We explored the sintering behavior of nickel powder with the goal of controlling particle size. A micro-sized nickel oxide powder was milled to uniform size (183.2 ± 53.8 nm) using a planetary ball mill; the size distribution was more uniform than that of a commercial powder (400.2 ± 183.4 nm). The sintering characteristics and capacitive features of the powders were analyzed after reduction in hydrogen. We found that the milled powder, with a narrow particle size distribution, exhibited delayed sintering rate, which paralleled the shrinkage of the of BaTiO3 layer. Discrete layers were thus obtained. Moreover, use of the milled powder reduced capacitance noise by 25% compared to that when other powders were employed; our milled powder contributed to the formation of stable electrodes.