Adhesion at metal-ZrO2 interfaces

This article reviews the present state of research on metal-zirconia interfaces. Interfaces play a crucial role in establishing the macroscopic properties and performance of zirconia-based heterogeneous materials, particularly composites and layered structures, which have a major significance in an extraordinary variety of industrial and technological applications. We have compiled the results reported on recent experimental and theoretical investigations which address the understanding of the nature and strength of the interface interactions from the macroscopic length scale to the atomic characterization. We have mainly focused on microscopic experimental results and ab initio atomistic calculations of diverse metal-zirconia systems, which are limited by the requirement of low misfit between the metal and ZrO2 lattices. However, systematic investigations of the wettability of zirconia surfaces by liquid metals and of the mechanical properties of cermets and layered structures are also compiled, since they are intimately related to the strength of the interaction between metals and zirconia. Most applications use stabilized ZrO2 phases doped with aliovalent oxides, where the electronic and structural properties of the ideal ZrO2 lattice are significantly altered due to the combined presence of O vacancies and substitutional dopant cations. The existence of such defects has a significant impact on the metal adhesion, as evidenced both in the experiments and calculations. Additionally, the spontaneous structural transformation of zirconia in the presence of oxygen vacancies can occur, and its role in the interface interactions is explored. (c) 2006 Elsevier B.V. All rights reserved.