Dielectric Properties of Fine‐Grained Barium Titanate Based X7R Materials

Abstract

The next generations of multilayer ceramic capacitors are expected to have active ceramic layer thicknesses of 3 μm or less. To retain a reliable ceramic device, it is advantageous to engineer a uniform and fine‐grained microstructure. In this study, a dense ceramic (>96% of theoretical) with fine‐grained size (<0.2 μm), and permittivity of 2800, meeting the EIA X7R temperature characteristic has been obtained using hydrothermally synthesized BaTiO3 powder with precipitation‐coated additives. The temperature coefficient of capacitance (TCC) and the dissipation factor (DF) are investigated as a function of active layer thickness and compared with that of a conventional coarse‐grained dielectric of similar composition and fired density. The fine‐grained ceramic maintained X7R characteristic in active layers as thin as 3 μm under 1 VAC and 1 kHz test conditions. For equivalent active thickness, the DF of the fine‐grained version was consistently lower than the coarse‐grained material. These results indicate that an improved voltage coefficient is possible for finer‐grained materials under otherwise equivalent conditions. The possible causes for this behavior are also discussed.