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Conductive Nature of Grain Boundaries in Nanocrystalline Stabilized Bi2O3 Thin-Film Electrolyte
journal contribution
posted on 2018-01-25, 00:00 authored by Seung
Jin Jeong, No Woo Kwak, Pilgyu Byeon, Sung-Yoon Chung, WooChul JungStabilized Bi2O3 has gained a considerable amount of attention
as a solid electrolyte material for low-temperature solid oxide fuel
cells due to its superior oxygen-ion conductivity at the temperature
of relevance (≤500 °C). Despite many research efforts
to measure the transport properties of stabilized Bi2O3, the effects of grain boundaries on the electrical conductivity
have rarely been reported and their results are even controversial.
Here, we attempt quantitatively to assess the grain boundary contribution
out of the total ionic conductivity at elevated temperatures (350–500
°C) by fabricating epitaxial and nano-polycrystalline thin films
of yttrium-stabilized Bi2O3. Surprisingly, both
epitaxial and polycrystalline films show nearly identical levels of
ionic conductivity, as measured by alternating current impedance spectroscopy
and this is the case despite the fact that the polyfilm possesses
nanosized columnar grains and thus an extremely high density of the
grain boundaries. The highly conductive nature of grain boundaries
in stabilized Bi2O3 is discussed in terms of
the clean and chemically uniform grain boundary without segregates,
and the implications for device application are suggested.