Analysis on the Sintering Process of X7R MLCC Materials

Transmission Electron Microscopy and Scanning Transmission Electron Microscopy were applied to study sintering process of the X7R MLCC materials, BaTiO3-MgO-Y2O3-(BaCa)SiO3. Though the materials were porous at the intermediate state of sintering process, the Ar-ion beam milling technique was employed for specimen preparation of electron microscopy. Succeeding in preparation, structural changes in microscopic scale have become visible. It has found that at rather low firing temperatures where the materials would not show any shrinkage in the macroscopic scale, the additives such as yttria, were already active. It was confirmed that thin Y layers of a few nanometers in thickness were formed at the surface of BaTiO3 Particles. The macroscopic shrinkage could progress, as yttria or calcia begins to diffuse toward the inner part of BaTiO3 particles. After the shrinkage, so-called core-shell structures could be observed.