Oxide eutectics: Role of interfaces in the material properties

Eutectics are a paradigm of micron scale composite materials with improved properties. Improved mechanical properties and thermal stability of eutecti cs as compared with ceramics or single crystals of component phases are a c onsequence of the presence of huge amounts of interfaces. Interface morphol ogy and ordered structures also invites to explore other properties of regu lar eutectics such as light guiding effects, anisotropic ion conduction, us e as structured substrates for patterned films, etc. In this work we report on the production of several eutectic crystals of wide band gap materials, grown from the melt by unidirectional solidification. The structure, mecha nical properties and interface morphology were determined using different t echniques including X-ray diffraction, SEM, TEM, Raman and optical spectros copy techniques. Examples of lamellar microstructures are provided by the Z rO2-CaO, ZrO2-NiO and CaF2-LiF systems. Planar light guiding and anisotropi c ion conduction are some of the unconventional properties of these regular composites. ZrO2-MgO, ZrO2-Al2O3 and CaF2-MgO are examples of fibrous eute ctics. The alumina-zirconia composite presents excellent mechanical propert ies also related to the presence of residual thermostresses that have been measured using different piezospectroscopic effects. The fluorite-magnesia eutectic is an example of semifaceted non-regular composite showing light g uiding effects.