Barium titanate zirconate ceramic capacitors - nickel oxide coatings reduced in hydrogen to form nickel electrodes

摘要

An unfired ceramic with high K (e.g. mixt. of titanates, oxides, zirconates, stannates) is stacked in a series of layers with an electrode between each layer, the electrodes extending to one edge, and then to the other, in alternate layers. The layers are then pressed and sintered at 1000-1400 degrees C. For the electrode, a material is used which does not react with the dielectric at the sintering temp. but which can be converted to an electrode, e.g. for ceramics sintered in air, nickel oxide alone or mixed with FeO, CoO, V2O5, SnO2, MnO etc. can be used. The oxide can be applied as a paint, the vehicle being lost in sintering. After sintering, the pressing is heated e.g. for 24 hours in hydrogen at 280 degrees C, reducing the nickel oxide to nickel, thus making a good condenser electrode. A slight redn. of the titanate occurs but this only reduces K values around 6000 by 10-15% and the power factor also remains at an acceptable level. By adding e.g. tin oxide to the nickel oxide the redn. temp. can be lowered. This process eliminates the use of expensive metals (e.g. Pt, Pd) as electrodes thereby reducing costs.