MATERIALS LETTERS, vol.61, no.2, pp.551-555, 2007 (SCI-Expanded)
Layers of lanthanum titanate (La2Ti2O7) and alpha-alumina (alpha-Al2O3) were employed to form a layered composite in order to improve the fracture toughness of monolithic alumina. The composites were produced by two different processing methods. In the first, individually presintered pellets of alpha-Al2O3 and La2TiO7 were stacked together and hot-forged. In the second, tape cast molten salt La2Ti2O7 and dense alpha-Al2O3 were stacked together and hot-forged. The forged composite samples were investigated by optical microscopy, scanning electron microscopy (SEM), Vickers indentation and three-point bending. During the hot-forging process, an interphase, aluminum titanate (Al2TiO5) was found to form as a result of the reaction between alpha-Al2O3 and La2Ti2O7. The flexural strength and the fracture toughness of the resulting laminate composites were found to be 320 MPa and 7.1 MPa m(1/2), respectively. Indentation experiments showed that the newly formed Al2TiO5 at the interface is sufficiently weak to promote crack deflection and hence increase the fracture energy and mechanical properties of the composite. (c) 2006 Elsevier B.V. All rights reserved.