Masamitsu Nishida

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.

Effect of Y and Mn Doping in Pb(T, Zr)O3 Piezoelectric Ceramics on the Resonant Frequency and Capacitance Changes and Aging by Thermal Shock Tests

The effects of Y and Mn-doping in Pb(Zr, Ti)O3 (PZT) with respect to the resonant frequency changes and the aging phenomena caused by thermal treatment were studied in order to achieve a stable piezoelectric ceramic filter. Good thermal stability as well as a high mechanical quality factor QM were required for the piezoelectric ceramics to fabricate certain types of narrow band monolithic filters. The Cr-doped PZT showed a little aging phenomena in resonant frequency change after thermal shock tests, but QM was not high. The Cr and Mn-doped PZT had a large QM value, but a large amount of resonant frequency change and aging after thermal shock tests. It was observed that the PZT with the addition of Y and Mn has high QM and good temperature stability. These features were suitable for the use in filters and resonators.

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 Nanostructure-Controlled Lead-Perovskite-Based Ceramics

We studied the piezoelectric properties for structure-controlled ceramics of (Pb 0.9 Sr 0.1 )(Mg 1/3 Nb 2/3 ) 0.255 Ti 0.38 -Z 0.365 O 3 prepared by the ultrafine powder process called the «nanopowder process». The dense and uniform fine-grained ceramics in this system, which had the relative density of 97.5% and the average grain size of 1.9 μm, wire obtained by this process. The sample prepared by this process showed the large dielectric constant of above 5300 and the high electromechanical coupling factor k 31 of 0.41. It was found that, the nanopowder process is effective to improve the piezoelectric property. The maximum value of the piezoelectric constant |d 31 | was 356×10 -12 m/V

Preparation and Piezoelectric Properties of Ceramics-Plastic Composite Materials

Ceramics-plastic composite materials composed of piezoelectric hard materials with properties of high k33, high QM and low s33E for the ceramics and epoxy resin for the plastic were prepared. Dielectric and piezoelectric properties for thickness expansion were studied and new piezoelectric ceramics-plastic composite materials with properties of about 1/3 times lower densities (2.61 g/cm3), about 1/10 times lower relative dielectric constant (130), about 10 times higher elastic compliance constant (138.6×10-12 m2/N) and 4.4 times higher piezoelectric voltage constant (101×10-3 Vm/N) than usual ceramics were obtained.

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.