The discovery has been published in the August issue of Advanced Materials (Vol. 19, No. 17, pp. 2313-2318), one of
the most prestigious journals in the field of Materials Science. The key feature of the new material is the nanofibrillar structure, which was obtained by growing the
material by directional solidification from the melt at high growth rates in an inert atmosphere using the laser-heated floating zone method. Under conditions of cooperative growth, the ternary eutectic presented a homogeneous microstructure, formed by bundles of single-crystal alumina and yttrium -aluminum garnet whiskers of ≈ 100 nm in width with smaller yttria-stabilized zirconia whiskers between them.
The interfaces were free from amorphous phases and very strong, being able to withstand the extremely high thermo-elastic residual stresses generated upon cooling.
The outstanding strength of the ternary eutectics was explained in terms of the synergistic effect of the microstructure refinement provided by the high growth rates, and the toughening induced by crack deflection along the nanofibrills due to the anisotropy in the fracture toughness of sapphire and to the thermal residual stresses.
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