Regular Network of Misfit Dislocations at the BaZr0.8Y0.2O3-x/NdGaO3 Interface and Its Role in Proton Conductivity

The interface between mismatched perovskite oxides presents novel physical and chemical features of interest for the development of engineered materials with tailored properties. In this article, we report on the presence and properties of a regular network of misfit dislocations (MDs), which self-assembles at the interface between a thin film of the proton conductor BaZr0.8Y0.2O2.9 and the substrate, the (110) oriented NdGaO3 wide-gap insulator. The conductivity properties of this system strongly depend on the atmosphere at which a thermal annealing is carried out. Namely, a conductivity increase is observed after annealing at 450 °C in wet atmosphere. An annealing in dry environment at the same temperature brings back the conductivity to its pristine value. X-ray diffraction measurements show a strong increase of the strain field associated with the dislocation network, after annealing in wet atmosphere, suggesting that hydroxyl groups mostly accumulate in the cores of the interface MDs rather than in the bulk of the BaZr0.8Y0.2O2.9 thin film. A further annealing in dry environment allows to recover the initial value of the strain field. The reported data indicate a strong involvement of the interface MDs in the transport properties of perovskite oxide interfaces.