Oxygen removal at grain boundaries in platinum films on YSZ

Abstract

Platinum films with different types of grains (different grain boundary angles and grain sizes) and different fractions of grains have been prepared on YSZ and then anodically polarised. On the basis of the size and the development of the electrical resistance during polarisation and the microstructural changes due to polarisation, the following oxygen removal ways are supposed: i) High angle grain boundaries are oxygen permeable and oxygen can be built out here without microstructural changes. ii) At twins and at high angle grain boundaries, oxygen bubbles can also be formed and grow in size. In the case of bubbles at twin positions, these bubbles rupture completely, when the pressure within them is high enough. In the case of bubbles within polycrystalline films, the bubbles crack at the grain boundaries, which are widened afterwards. iii) Small angle grain boundaries are not as oxygen permeable as high angle grain boundaries, but also here oxygen bubbles can be formed. These bubbles do not grow in size or crack.