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The potential barrier formed at the grain boundaries in Fe-doped SrTiO3 is reported to be one of the main reasons of the exceptionally large grain boundary resistivity of the material. Of particular interest is thus how to accurately quantify the potential barrier height, Ψgb, in such electronic conductors. This study aims to expand the applicability of a linear diffusion model (namely I–V model) to electronic conductors. The I–V model has previously proven its success in accurate determination of Ψgb in popular ionic conductors. By employing 1 mol% Fe-doped SrTiO3 as a model material, the current–voltage characteristics of the grain boundary investigated demonstrate the power law behavior predicted by the I–V model, verifying the applicability of this model. The Ψgb estimated from the I–V model at different temperatures are compared with those from the resistivity ratio of the grain boundary to the bulk. The resistivity ratio has been exclusively used to determine Ψgb in various conductors over several decades and yet has limitations in its accuracy. The Ψgb determined by the I–V model are found to be substantially lower than those from the resistivity ratio; such discrepancy implies that the potential barrier only partially contributes to the high grain boundary resistivity of a lightly doped electron–hole conducting SrTiO3. [ABSTRACT FROM AUTHOR]

The extent of the influence of space charge on the electric current through the grain boundary in solid electrolytes can be parameterized by the grain boundary potential, i.e. the height of the potential barrier formed at the grain boundary. Previously the value of this parameter has been estimated exclusively by the ratio of the grain boundary resistivity to the bulk counterpart over several decades. We recently demonstrated that it can be alternatively determined by analyzing the current–voltage characteristic of the grain boundary. Furthermore, we theoretically justified that the conventional method is in fact a subset of the new method, therefore, the latter is a more reliable and comprehensive approach to determine the grain boundary potential. Here, we present the experimental results that verify our theoretical justification. The values of the grain boundary potential determined for 1 mol% Sr-doped LaGaO3 (LSG1) employing both methods are in excellent agreement with one another. Such a consistency has not been reported for other solid electrolytes to date and we provide an explanation for it. Our data also indicate that for the case of LSG1, the Nernst–Einstein relation is preserved at the electric field exceeding 900 kV cm−1. [ABSTRACT FROM AUTHOR]