Hisamitsu Shizuno

Dielectric Properties of Rare-Earth-Oxide-Doped BaTiO3 Ceramics Fired in Reducing Atmosphere

In order to gain an understanding of highly reliable electrical characteristics for the Ho-doped multilayer ceramic capacitors with Ni electrodes, dielectric properties of various rare-earth-oxide-doped BaTiO3 ceramics were studied. The smaller ionic radius rare-earth-oxide (Dy, Ho, Er)-doped samples showed lower resistivity in reducing atmosphere, but higher resistivity in oxidizing atmosphere at the cooling stage, compared with the larger-ion (La, Sm, Gd)-doped samples. Multilayer ceramic capacitors with Ni electrodes using the smaller-ion-doped materials showed smaller aging rate and longer lifetime. We developed Ni-electrode MLCs with X7R specification as 1 µ F in the 2125 type.

Properties of Y5V Multilayer Ceramic Capacitors with Nickel Electrodes

In order to realize nickel electrode multilayer ceramic capacitors with high capacitance per volume, the holmium-doped (Ba, Ca, Mg)(Ti, Zr)O3 system was studied. In the case of maintaining an oxidizing atmosphere at the cooling stage, the resistivities of the dielectric materials were easily recovered by doping with Ho. The newly developed dielectric material exhibited high dielectric constant (18,000) and high resistivity (>10-12 Ω cm). Using the dielectrics, nickel electrode multilayer ceramic capacitors with high specific capacitance (Y5V 4.7 µF in EIA 1206 size) were developed. They showed highly reliable characteristics.