Osamu Furukawa

Dielectric Properties of Modified Lead Zinc Niobate Ceramic

Crystal structures, dielectric properties and electrical resistivities for partially substituted lead zinc niobate [Pb(Zn1/3Nb2/3)O3] ceramic were investigated. This ceramic, sintered at 1000–1050°C, was composed mainly of perovskite phase and showed a high dielectric constant (3500–5000) and a high resistivity (approximately 1013Ωcm) when partial substitutions of the Pb site by Ba or Sr and the (Zn1/3Nb2/3) site by Ti in the Pb(Zn1/3Nb2/3)O3 were carried out. The reason why the perovskite phase was stable in the sintered body is explained qualitatively by introducing the concepts of an electronegativity difference and a tolerance factor.

A new relaxor dielectric for high voltage multilayer ceramic capacitors with large capacitance

A new ceramic dielectric, based on (Pb0.65Ba0.35)(Zr0.7Ti0.3)O3 has been developed. This dielectric, fired at low temperature of 1080°C, showed a high dielectric constant of 4500, a less than 0.3% dissipation factor and flat temperature characteristics of capacitance satisfying Y5P specifications in the EIA (Electronic Industries Association) Standard. Evaluation as a multilayer ceramic capacitor (MLC) revealed an excellent capacitance dependence under a high DC field. Thus, this dielectric is one of the promising candidates for high voltage MLCs with large capacitance.

Lead Perovskite Relaxor-Based Low-Loss Ceramic Dielectric for High-Voltage Ceramic Capacitors

A low-loss ceramic dielectric with a less than 0.1% dissipation factor at 100 kHz, based on a modified lead zinc niobate relaxor, has been fabricated by shifting the ferroelectric transition temperature (Tc) to below -55°C. This dielectric has a high dielectric constant (K), ranging from 250 to 2000. The temperature coefficient of capacitance (TCC) locates at the middle area between values for temperature compensation dielectric and values for high-K dielectric. Even at 150°C, high insulation resistance, more than 5×1013 Ωcm, was also retained. Moreover, a typical composition with K=530 revealed that the dielectric has a high breakdown voltage of 95 kV per 10 mm of thickness and a TCC value of -2900 ppm/°C. Accordingly, this dielectric has proven useful for high-voltage ceramic capacitors.

Interference signal processing for dynamic displacement measurement with 1 ns time resolution

We propose a novel signal processing method for a laser-interferometer-based displacement measurement system with significantly improved time resolution that enables us to measure transient state vibration with an instantaneous frequency of 100 MHz. In this method, a reference light is modulated by a sinusoidal waveform, and dynamic displacement is derived from the envelope curves of the interference signal. Using a phase modulator to emulate dynamic displacement with an instantaneous frequency of 100 MHz and a maximum peak-to-peak amplitude of over 100 nm, we confirmed that the proposed method can be used to measure fast dynamic displacement with 1 ns time resolution within 2.6 nm standard deviation.

Effects of Specific Surface Area of Starting Pre-Calcined Dielectric Powders on Sintering Behavior and Dielectric Properties of Relaxor/Modified-BaTiO3 Composite

Sintering behavior and dielectric properties of relaxor/Zr-modified BaTiO3 (BTZ) dielectric composite have been investigated as functions of specific surface area (SSA) of starting pre-calcined dielectric powders, as well as firing temperature. Relative dielectric constant of the dielectric composite increased with the SSA of relaxor. However, this was not in the case with the BTZ powder. The relative dielectric constant decreased either when the SSA of BTZ was 2.0[m2/g] or when firing temperature was 1210°C. Optimization of the SSAs of relaxor and BTZ powders, as well as firing temperature made it possible to produce Multilayer Ceramic Capacitors (MLCs) which meet X7R specifications in the Electronic Industries Association (EIA) standard.