Reliability improvement in BaTiO ₃ ‐based multilayer ceramic capacitors by incorporating alloying of nickel internal electrodes

Abstract The mechanism of the reliability improvement by alloying Ni internal electrodes of BaTiO 3 ‐based multilayer ceramic capacitors (MLCCs) was studied from two perspectives: electric barrier formation at the electrode‐dielectric interface and diffusion of alloying elements into the bulk dielectric layer. In the case of Ni‐Sn alloy electrodes, the reliability improvement is due to the formation of a Sn segregation layer at the interface between the internal electrode and the dielectric layer, and the associated formation of a Schottky barrier, which is an electron barrier layer. Therefore, when the dielectric layer is sufficiently thin, this electron barrier layer functions critically, but as the dielectric film thickness increases, the effect of this barrier layer gradually decreases because of an increased number of grain boundaries and the grains in the dielectric layer, which are other factors that determine the insulation. On the other hand, in the case of Ni‐In alloy electrodes, In diffuses not only at the interface between the internal electrode and the dielectric, but also into the shell part of the “core‐shell” structure of the BaTiO 3 grains in the dielectric layer along with the grain boundaries. Therefore, it was revealed that the reliability improvement continues even if the dielectric thickness increases to a certain extent. The outstanding improvement in the reliability of the Ni–In MLCC could be derived from not only the formation of an electrical barrier at the interface between the internal electrode and the dielectric layer, but also enhanced resistivity provided by a grain boundary barrier layer and an intragranular acceptor region at the shell region of the core‐shell structure by the In diffusion.