Grain boundary conductivities of 0.58% Y2O3 doped CeO2 thin films

We have prepared Y2O3 doped CeO2 thin films on various substrates using electron beam evaporation. Both polycrystalline and single crystal-like textured films were shown by x-ray diffraction and transmission electron microscopy analyses. AC impedance spectroscopy was used to study the electrical properties of the films. The ionic conductivities of the films are dominated by grain boundaries, and higher as compared to that of a bulk material having the same dopant concentration sintered at 1500 degrees C. The grain boundary conductivities of the films were investigated with regard to grain size, grain boundary impurity segregation, space charge on grain boundaries, and grain boundary misorientations. The contribution of grain boundary misorientation to the, resistance of the grain boundary is considered to be negligible with respect to those of the impurity layer and space-charge layers. The grain boundary resistance may originate from the oxygen vacancy depletion in the space-charge layers.