Nobutatsu Yamaoka

X7R Multilayer Ceramic Capacitors with Nickel Electrodes

Electrical properties and microstructures of a holmium-doped (Ba1.01Mg0.01)O1.02(Ti0.98Zr0.02)O2 system were studied. Additions of Ho2O3 had little effect in preventing the dielectrics from reducing at high temperature, but the resistivity at low temperature increased with increasing amount of Ho2O3 when treated in oxidizing atmosphere at the cooling stage. From transmission electron micrograph (TEM) observation, it was noted that the microstructure exhibited a grain core-grain shell structure. Newly developed X7R multilayer ceramic capacitors with Ni electrodes revealed highly reliable electrical properties.

Properties of Glass-added Barium Titanate Based Ceramics Fired in a Reducing Atmosphere

Electrical properties and microstructures of glass-added barium titanate ceramics were studied. Resistivities of the ceramics were increased markedly by addition of glass components when they were fired in a reducing atmosphere. The flat temperature dependence of dielectric constant were obtained by substituting small amount of Sr and Ca for barium site under the presence of glass components. The multilayer ceramic chip capacitors with nickel electrodes which meet X7R specification have been developed. They exhibited high resistivity (>1012 Ωcm) and high dielectric constant (K=3300).

Characteristics of a SrTiO3-Base BL Capacitor with Nb2O5 and CuO Added

Characteristics of BL capacitors of semiconductive SrTiO3-base composition with Nb2O5 and CuO added were investigated. The grain growth was required for getting a high apparent dielectric constant under the firing condition in which a liquid phase appeared, and the ceramics with large grains such as 85 µm were fabricated. The apparent dielectric constant of 100,000 and the dissipation factor of less than 0.01 were obtained.

Low Temperature Sintered BaTiO3 Ceramics with Bi4Ti3O12 Added

Microstructures and electrical properties of BaTiO3 ceramics with Bi4Ti3O12 added were investigated. BaTiO3 powders were synthesized by calcining preliminarily at 1100°C to 1300°C. Heat-treating was examined at a temperature range from 1000°C to 1200°C. All samples fired above 1100°C have individually a saturated shrinkage. Apparent activation energies for the shrinkage processes were ab. 125 kcal/mol and ab. 114 kcal/mol for a sample of BaTiO3(H)–0.04Bi4Ti3O12 composition and that of BaTiO3(L)–0.04Bi4Ti3O12 composition, respectively. In a previous sample a dielectric constant of the Curie point near to 120°C changed markedly at a firing temperature between 1150°C and 1160°C.

PbTiO3 Based Pyroelectric Ceramics Modified with Stannate Compounds

The properties of PbCa(Cu, Nb)TiO3–NiSnO3 based pyroelectric ceramics were investigated. Microstructures were examined by a X-ray microanalysis. The pyroelectric ceramics were consisted of three individual of PbCa(Cu, Nb)TiO3 phase NiSnO3–NiTiO3 compound phase and SnO2 rich phase in a ceramic composition. Pyroelectric properties of the ceramics were Fv of 8.5×10-11 C cm/J and Curie point of 272°. By an addition of NiSnO3 to Pb0.7Ca0.3(Cu1/3Nb2/3)0.05Ti0.95O3, Fv were up to the high value with an increase of P(P=5.8×10-8 C/cm2°C) and a decrease of es(es=220).

The Electrical Properties of a SrTiO3 Bicrystal Joined by Thin Film of a Molten Bi2O3

A niobium-doped SrTiO3 single crystal was grown using the FZ (floating zone) method. The single crystal was sliced in two, and the two halves were joined by thin film of Bi2O3 which was sandwiched between the two half-crystals at a high temperature (1400°C). The electrical properties of the obtained bicrystal were similar to those of a SrTiO3 IBL capacitor. The bicrystal was considered to be applicable to the study of ceramic grain boundary properties.

Multilayer ceramic capacitors with nickel electrodes

Electrical properties and microstructures of holmium-doped (Ba,Ca,Mg)(Ti,Zr)O3 system were studied. Addition of Ho2O3 had little effect in preventing the dielectrics from reducing at high temperature, but the resistivity at low temperature of Ho-doped samples increased with increasing amount of Ho2O3 when they were treated in oxidizing atmosphere at the cooling stage. The newly developed dielectric materials exhibited high dielectric constant 18000 for Y5V specification, 3200 for X7R specification. Using these dielectric materials, Ni-electrode multilayer ceramic capacitors with high specific capacitance (Y5V 4.7μF, X7R 1μF in EIA 1206 size) were developed. They showed highly reliable electrical characteristics.

Properties of a ceramic capacitor composed of Zn-Cu electrodes

Abstract Zn-Cu electrodes were composed on both surfaces of ceramic capacitors and the properties were investigated. The electrical properties of a BaTiO3-based ceramic capacitor (Y5V) with a Zn-Cu electrodes were equal or excellent to the same ceramic capacitors with silver electrodes. An oxidation ratio of the fired Zn electrodes was examined by chemical analysis and ESCA. Zn metals were oxidized with the ratio of ca. 50%. As the result of a migration test examined in distilled water, the reaction starts after 1 min in a fired silver electrode, 9 min in a Cu plating electrode and in a Zn-Cu electrode, and more than 15 min in a fired Zn electrode.