Microstructural Design of Dielectrics for Ni-MLCC with Ultra-thin Active Layers

The influence of raw BaTiO3 (BT) powder characteristics such as particle size and crystallinity on the microstructure as well as the electrical properties of X7R-type multilayer ceramic capacitors with Ni internal electrodes (Ni-MLCCs) was investigated in the BT-Ho-Mg-Mn system. For the MLCC samples, the dielectric constant at room temperature decreased with a decrease in the grain size. In particular, it drastically decreased for the grain sizes of less than 200 nm. Furthermore, the dielectric constant was considerably dependent on the tetragonality (c/a) of the raw BT powder, whereas the full-width at half maximum (FWHM) had little effect on the electrical properties. The samples obtained from the raw BT powder with high c/a showed the inhibited grain growth and they consisted of a large number of core-shell grains having clear domain patterns in the core region. Accordingly, the sample with high c/a showed high dielectric constant and good temperature characteristics with respect to capacitance.