Motomasa Imai

PZT Thin Film Preparation on Pt-Ti Electrode by RF Sputtering

Pt-Ti alloy films were studied for use as a lower electrode of the ferroelectric lead zirconate titanate (PZT) thin film capacitor. Pt-Ti alloy films with different Ti/Pt atomic ratios were first prepared by rf sputtering. Subsequently, PZT thin films were deposited also by rf magnetron sputtering on the Pt-Ti alloy metals. The Ti/Pt ratio in the alloy was found to strongly affect the crystal structure formation and the composition of the PZT thin films. The Ti/Pt ratio range from 0.02 to 0.17 was shown to bring about a preferable perovskite-type structure and a reproducible constant composition. The effect of Ti atoms in the Pt-Ti lower electrode was discussed in connection with the Pb atom evaporation rate.

A high-resolution transmission electron microscope study of a zinc oxide varistor

Investigations were made of varistor microstructure, the morphology of Bi2O3 at multiple ZnO grain junctions, Bi2O3/ZnO grain boundaries and ZnO/ZnO grain boundaries (especially whether Bi2O3 is present or not at the ZnO/ZnO grain boundary) by means of high-resolution transmission electron microscopy and X-ray microanalysis in the scanning transmission electron microscope. Bi2O3 at multiple ZnO grain junctions consists of small particles of 0.1μm in diameter, and they are vitrified to some extent. It is suggested that bismuth ions dissolve into ZnO grains over a 30 nm range from a Bi2O3/ZnO grain boundary; however, there is no bismuth at ZnO/ZnO grain boundaries.

Low firing and high dielectric constant X7R ceramic dielectric for multilayer capacitors based on relaxor and barium titanate composite

A temperature stable ceramic dielectric with a low firing temperature (1130 °C) and a high dielectric constant (3700 to 2600) has been developed by sintering the mixture of precalcined lead-based relaxor and prefired modified barium titanate.This dielectric was confirmed to be a two-phase ceramic composite body, according to X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and dielectric measurements.A shortcoming of the high dissipation factor in the dielectric has been reduced by incorporating MnO into the barium titanate constituent prior to mixed sintering.This ceramic dielectric meets X7R specifications in the EIA (Electronic Industries Association) standard.

Effects of SiO2 and Cr2O3 on the formation process of ZnO varistors

The effects of SiO2 and Cr2O3 on the formation process of ZnO varistors were investigated. Prior to formation of the Zn2.33Sb0.67O4 spinel phase (Sp-phase), a spinel-like phase forms. However, this phase does not control the varistor microstructure. The Sp-phase and the Bi2O3-phase which were formed by the decomposition of the Bi2(Zn4/3Sb2/3)O6 pyrochlore phase played important parts in the control of the varistor microstructure. That is, the Bi2O3 phase produced in the reaction promotes the initial sintering of the varistor and the Sp-phase inhibits the ZnO grain growth. In this reaction, SiO2 and Cr2O3 play a role in decreasing the decomposition temperature of the pyrochlore phase. Decreasing the decomposition temperature below 900° C (where ZnO grain growth begins) leads to the inhibition of ZnO grain growth.