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Journal of Materials Science, September 2014, Volume 49, Issue 17, pp 6074-6080.
Jun Wang, Hans Conrad.
Materials Science and Engineering Department, North Carolina State University, Raleigh, NC, 27695-7907, USA.
Abstract
A model based on the effect of a modest applied dc electric field on grain growth is proposed for the contribution of the space charge to the grain boundary (GB) energy in 3 mol % yttria-stabilized zirconia (3 YSZ). The model considers that the total GB energy γ0b (the capillary driving force for grain growth) consists of three major components: (a) γΣb due to the misorientation between neighboring grains, (b) γsb due to the size misfit between the segregated solute and the solvent cations, and (c) γeb the electrostatic (space charge) component, which results from the segregation of the aliovalent yttrium ions to the grain boundaries. The former two components combined comprise 40 % of the total GB energy in 3 mol % yttria-stabilized zirconia and the electrostatic component 60 %. Based on the model, the calculated magnitudes of the three components were in qualitative accord with theoretical considerations and with values reported in the literature. A reduction in γeb, and in turn in γ0b, results from the bias exerted by the applied field on the space charge potential that occurs with the segregation of the yttrium ions to the grain boundaries. The observed reduction of grain growth in 3 mol % yttria-stabilized zirconia by an applied electric field is attributed mainly to the reduction in γeb by the field.
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