Influence of microstructure on the cross-plane oxygen ion conductivity of yttria stabilized zirconia thin films

The electrical cross-plane conductivity of 8?mol% yttria stabilized zirconia (YSZ) thin films prepared by different deposition techniques, namely aerosol assisted chemical vapor deposition, wet spray pyrolysis (SP), and pulsed laser deposition (PLD), is correlated with their microstructure. Depending on deposition technique and process conditions, microstructures ranging from amorphous to randomly oriented nanocrystalline or columnar with preferred (111) orientation are obtained. Cross-plane AC impedance measurements of these thin films show that the oxygen ion conductivity of randomly oriented nanocrystalline samples is determined by the grain boundaries, which show significantly lower transport properties than the grain interior. In columnar microstructures, the conductivity is determined by ionic transport through the grains only. The same conduction behavior is found for amorphous and randomly oriented microstructures with grain sizes between 3?nm and 9?nm, indicating that no true size effects occur in 8?mol% YSZ. Grain and grain boundary conductivity determined for nanocrystalline 8?mol% yttria stabilized zirconia thin films of different microstructures.