Modulated and ordered defect structures in electrically degraded Ni–BaTiO3 multilayer ceramic capacitors
- 1 November 2003
- journal article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 94 (9), 5990-5996
- https://doi.org/10.1063/1.1615300
Abstract
Structural defects formed on {111} planes of during the degradation of high performance multilayer X7R ceramic capacitors are studied using transmission electron microscopy and electron energy loss spectroscopy (EELS). Regular pseudocubic barium titanate grains are present in as-produced (virginal) base-metal electrode capacitors. However, there is a coexistence of regular, modulated, and long-range ordered structures in intentionally electrically degraded devices. The EELS analysis demonstrates that the concentration of oxygen vacancies in barium titanate with modulated or ordered structures is higher than that in the regular perovskite grains. The clustering or accumulation of oxygen vacancies in the structural framework of gives rise to the formation of new metastable structures. These observations are consistent with earlier models for degradation, but demonstrate that the details of the process may be more complex than originally assumed. Here we introduce new details on the nature of the reduction process and the manner in which the lattice accommodates the enhanced oxygen vacancy concentration towards the failed regions of the capacitors and in the vicinity of the “blocking” cathodic electrodes.
Keywords
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