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According to the space charge concept, oxygen vacancies are depleted in the grain boundary space charge layers of acceptor-doped ZrO2; whereas electrons are expected to accumulate in the space charge layers if present, leading to significant changes in the grain boundary electrical properties. In this work, electrons were introduced to 8 mol % TiO2 and 7.36 mol % Y2O3-codoped ZrO2 by annealing in the mixture of 2% H-2-Ar; as a result, the grain boundary arc disappeared, and the electrical conductivities increased considerably, especially for the sample with finer grain size. Both phenomena suggest highly conductive grain boundaries resulting from the accumulation of electrons in the space charge layers. (C) 2003 The Electrochemical Society.
Guo et al. (Fri,) studied this question.