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 1000C) remains similar to that of undoped or acceptor-doped BaTiO3, its p-type conductivity in oxidizing atmospheres (e.g., Po2 > 10– 6at 1000C) 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 1000C), 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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