The influence of experimental conditions on the morphology and phase composition of Nb-doped ZrO2 films prepared by spark anodization

This paper reports the morphological and microstructural characterization of Nb-doped ZrO2 films obtained by anodic doping in conditions of spark electrolytic breakdown. The oxide films were prepared by galvanostatic anodization of metallic Zr in oxalic acid solution containing ammonium oxaloniobate, NH4H2[NbO(C2O4)3]⋅3H2O using Nb(V) ions as the precursor dopant. The characterization was performed by SEM and XRD. A factorial design was used to optimize the experiments and study the influence of experimental variables on morphology and phase composition. The results demonstrated that the dopant concentration is the most important factor that affected the analyzed responses. A significant influence of this variable was observed on the pore average diameter and on the percentage of the stabilized tetragonal phase. The temperature also affected the phase composition, however no effect was observed on the morphological response.