Co-Doping Effect of Mn and Y on Charge and Mass Transport Properties of BaTiO3 |
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Authors: | Chung-Eun Lee Sun-Ho Kang Dong-Sook Sinn Han-Ill Yoo |
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Affiliation: | (1) School of Materials Science and Engineering, Seoul National University, Seoul, 151-742, Korea;(2) Samsung Electro-Mechanics Co., Ltd., Suwon, Kyunggi-Do, 442-743, Korea;(3) Present address: Chemical Technology Division, Argonne National Lab., U.S.A. |
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Abstract: | BaTiO3-based multilayer-ceramic capacitors (MLCC) using base metal (Ni) electrodes normally contains Mn and Y each approximately on the order of 0.5 mol%. It is only empirically known that the co-doping of Y and Mn facilitates sintering with the base-metal electrodes as well as improves the device performance and life time. In order to understand the effect of the co-doping, we have measured the electrical conductivity and chemical diffusivity on polycrystalline BaTiO3 that is co-doped with Y and Mn each by 0.5 mol% against oxygen partial pressure at elevated temperatures. It is found that while the n-type conductivity in reducing atmospheres (e.g., Po2 < 10– 6 atm at 1000 C) remains similar to that of undoped or acceptor-doped BaTiO3, its p-type conductivity in oxidizing atmospheres (e.g., Po2 > 10– 6at 1000 C) is remarkably suppressed compared to the latter. The chemical diffusivity is also similar to that of the latter in magnitude (e.g., 10– 2–10– 5 cm2/s at 1000 C), but its trend of variation with oxygen partial pressure is rather opposite. These variations of the conductivity and chemical diffusivity are mainly attributed to Mn ions changing their valence from +2 to +3 to +4 with increasing oxygen partial pressure. It is explained from a defect-chemical view why the codoping of fixed-valent donor (Y) and variable-valent acceptor (Mn) has been practiced in MLCC processing. |
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Keywords: | MLCC BaTiO3 acceptor-donor codoping defect structure chemical diffusivity |
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