受賞記念講演:平成14年度技術功績賞 Development of Dielectric Ceramics for Nickel Electrode Multilayer Capacitors (特集高精度電子部品材料)

概要

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Calcium-doped BaTiO3-based dielectrics have a high resistance to reduction. This can be explained by taking the following three factors into account: 1) decrease in conduction electron density caused by acceptor Ca ions at the Ti site, 2) low freezing temperature of the equilibrium reaction by Ca ions at the Ti site, and 3) large enthalpy change in the reduction reaction by Ca ions at the Ba site. Fine-grained BaTiO3 ceramics can be prepared using the tetragonal BaTiO3 powder using ultra-fine starting BaTiO3 powder synthesized by hydrolysis method. The non-uniform distortion is caused in the grains during sintering, which is attributed to the surface tension and clamping stress from the thin grain boundary layer. This suppresses the tetragonality symmetry of the grains and provides the BaTiO3 ceramics with a high dielectric constant, low loss, and flat capacitance temperature characteristics. The Ca-doped ultra-thin dielectric layer compatible with nickel electrode can realize the nickel electrode multilayer capacitors of large capacitance and large volumetric efficiency, which is competitive with the Ta and Al-electrolytic capacitors and as reliable as conventional precious metal electrode multilayer capacitors.
社団法人粉体粉末冶金協会の論文
2004-04-15