Published online by Cambridge University Press: 15 February 2011
The mechanical properties of zirconia are known to be a function of phase composition. We show here that a nanolaminate geometry can be used to control the phase composition of zirconia films. The experiment consisted of growth of nanoscale multilayer films (nanolaminates) of polycrystalline zirconia and amorphous alumina by reactive sputter deposition on Si (111) and fused silica substrates. The films were characterized using x-ray diffraction and high resolution electron microscopy. The results show that both monoclinic (m) and tetragonal (t) zirconia polymorphs were formed in the zirconia layers. Most crystallites are oriented with either close-packed {111}-t or {111}-m planes parallel to the substrate. The volume fraction of tetragonal zirconia, the desired phase for transformation-toughening behavior, increases with decreasing zirconia layer thickness. Nanolaminates with a volume fraction of tetragonal zirconia exceeding 0.8 were produced without the addition of a stabilizing dopant, and independent of the kinetic factors that limit tetragonal zirconia growth in pure zirconia films.