Microstructural evolution of electrodes in sintering of multi-layer ceramic capacitors (MLCC) observed by synchrotron X-ray nano-CT

• Published in: Acta materialia Vol. 206; p. 116605
• Main Authors: Okuma, Gaku, Saito, Naoya, Mizuno, Kotaro, Iwazaki, Yoshiki, Kishi, Hiroshi, Takeuchi, Akihisa, Uesugi, Masayuki, Uesugi, Kentaro, Wakai, Fumihiro
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2021
• Subjects: 3D microstructure; MLCC; Sintering; Synchrotron X-ray tomography; 3D microstructure; MLCC; Synchrotron X-ray tomography; Sintering
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2020.116605

Synchrotron X-ray nano computed tomography was used to investigate the microstructural evolution during co-sintering of multi-layer ceramic capacitors (MLCC) consisting of Ni electrodes and BaTiO3 dielectric layers stacked alternately. As the electrode thickness reduced to submicron at the scale of a few particle diameters, the process produced the defect of inner electrode leading to capacitance loss. The discontinuous electrode region contained round holes and irregularly-shaped channels. The formation of discontinuity was associated with the increase of characteristic length of heterogeneous electrode structure, i.e., the coarsening occurred. The evolution of electrode morphology by surface/interface diffusion caused the breakup of ligament between two holes driven by instability induced by surface tension and stress. The ligament pinch-off inevitably generated sharp points which might enhance the local electric field bringing about the dielectric breakdown. A model was presented to explain the formation of defect from the heterogeneous particles packing in the electrode layer. [Display omitted]