Base-Metal Electrode-Multilayer Ceramic Capacitors: Past, Present and Future Perspectives

Multilayer ceramic capacitor (MLCC) production and sales figures are the highest among fine-ceramic products developed in the past 30 years. The total worldwide production and sales reached 550 billion pieces and 6 billion dollars, respectively in 2000. In the course of progress, the development of base-metal electrode (BME) technology played an important role in expanding the application area. In this review, the recent progress in MLCCs with BME nickel (Ni) electrodes is reviewed from the viewpoint of nonreducible dielectric materials. Using intermediate-ionic-size rare-earth ion (Dy₂O₃, Ho₂O₃, Er₂O₃, Y₂O₃) doped BaTiO₃ (ABO₃)-based dielectrics, highly reliable Ni-MLCCs with a very thin layer below 2 µm in thickness have been developed. The effect of site occupancy of rare-earth ions in BaTiO₃ on the electrical properties and microstructure of nonreducible dielectrics is studied systematically. It appears that intermediate-ionic-size rare-earth ions occupy both A- and B-sites in the BaTiO₃ lattice and effectively control the donor/acceptor dopant ratio and microstructural evolution. The relationship between the electrical properties and the microstructure of Ni-MLCCs is also presented.