Sol-gel fabrication of heteroepitaxial zirconia films on MgO(001) substrates

Zirconia films were fabricated by sol-gel dip coating of single-crystal MgO (001) substrates. Continuous polycrystalline layers of tetragonal zirconia, 40 nm thick, were obtained after firing at 600°C. At higher temperatures, abnormal grain growth, substrate uncovering and film break-up into islands were observed. At 1300°C, single-crystal islands of tetragonal MgO-ZrO2 solid solution appeared to be heteroepitaxially grown on the MgO(001) substrate, verified by X-ray rocking curve results from (001) zirconia planes and φ-scan experiments of the (113) planes. Semicoherent magnesia-zirconia interfaces were faceted and the large mismatch was accommodated through ordered misfit dislocations networks, as imaged by high-resolution transmission electron microscopy. Residual microdeformations of the MgO substrate were illustrated by increased full width at half-maximum (FWHM) of the ω-rocking curve measured on the (001) peak of the substrate.