Hiromu Ouchi

Dielectric Ceramics for Microwave Application

A review has been made to find the technical trend on the presently developed dielectric ceramics for microwave applications. Some new dielectric ceramics recently developed by authers that is (1) temperature stable and high Q materials of Ba(Zn1/3Ta2/3)O3 (BZT) and Ba(Zn1/3Nb2/3)O3–Ba(Zn1/3Ta2/3)O3 (BZNT) ceramics and (2) temperature stable and high dielectric constant materials of BaO–Sm2O3–TiO2(BST) ceramics and their applications have been introduced.

Dielectric Properties of Pb(Mg1/3Nb2/3)Ti(Ni1/2W1/2)O3 Ceramic

Dielectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3–Pb(Ni1/2W1/2)O3 pseudo-ternary ceramics were studied. The ceramics could be sintered at 1050°C, exhibited high dielectric constant (15000~20000) and high resistivity (1013Ωcm, 27000 ΩF). A small addition of MnO2 to these ceramics decreased the dissipation factor and caused a peculiar temperature dependence of dielectric constnt. The characteristics of multilayer chip capacitors made of these ceramics with Ag–Pd electrode are described.

Dielectric Properties of Pb(Mg1/3Nb2/3)(Zn1/3Nb2/3) (Fe2/3W1/3O3) Ceramics

Dielectric ceramics with the compositions of Pb(Mg1/3Nb2/3) O3–Pb(Zn1/3Nb2/3)O3–Pb(Fe2/3W1/3)O3 pseudo-ternary system were studied. The ceramics were sintered at 900°C, had high dielectric constant (6500) and small change of dielectric constant with temperature (+3%~-26% relative to 20°C between -25°C to 85°C). The powder processing of these compositions was studied. Pb2Nb2O7 phase remained in the ceramics with low calcining temperatures. Multilayer chip capacitors with Ag–Pd internal electrodes were fabricated.

Piezoelectric Properties of Hot-Pressed Lead Titanate Zirconate Family Ceramics

Piezoelectric properties of hot-pressed Pb(Zn1/3Nb2/3)O3–Pb(Sn1/3Nb2/3)O3–PbTiO3–PbZrO3 quaternary ceramics are described. The ceramics exhibited high coupling coefficient and high dielectric constant. A small addition of MnO2 to the quaternary ceramics increased markedly mechanical quality factor (QM=1400), and coercive field (Ec=20 kV/cm). The ceramics made it possible to produce high frequency transducer for large strain and high output voltage.