Electric characterization of grain boundaries in ionic conductors by impedance spectroscopy measurements in a bicrystal

Here we show impedance spectroscopy measurements on a bicrystal of the ionically conducting yttria stabilized zirconia (YSZ). By using micrometer sized electrodes it is possible to measure ionic transport perpendicular to a single grain boundary, and characterize its electrical properties. We are thus able to obtain the microscopic parameters that determine the charge distribution at the grain boundary and the ionic transport through it, as the potential energy barrier Delta Phi = 0.35 +/- 0.01 V at 275 degrees C, and the space charge layer thickness lambda(.) = 5 +/- 1 angstrom. These values are significantly different from those previously obtained in polycrystalline ceramic samples of the same material, and show much better agreement with the values predicted by the Mott-Schottky model for the charge distribution and ionic transport through the grain boundary.