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 degrees C. At higher temperatures, abnormal grain growth, substrate uncovering and film break-up into islands were observed. At 1300 degrees 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 phi-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 omega-rocking curve measured on the (001) peak of the substrate.