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The deformation and fracture behavior of polycrystalline Al2O3 and Al2O3/Nb/Al2O3 composites with perpendicular and inclined interfaces were investigated at room temperature by means of compression tests. It was found that polycrystalline Al2O3 fractured at higher stresses (>500 MPa) than Al2O3/Nb/Al2O3 composites, and that its failure always showed a split fracture mode. For the Al2O3/Nb/ Al2O3 specimens with interfaces perpendicular to the loading direction, cracks normally nucleated near the Nb/ Al2O3 interfaces and then propagated along the loading direction, finally leading to a split fracture in the polycrystalline Al2O3 parts. For the Al2O3/Nb/Al203 specimens with interfaces inclined to the loading direction, the split fracture of the polycrystailine Al2O3 parts strongly depends on the orientation of the Al2O3/Nb interfaces with respect to the loading direction. For all the Al2O3/Nb/Al2O3 specimens, intergranular cracking was seldom observed independent whether the interfaces are perpendicular or inclined to the loading direction. Based on these results, the fracture mechanisms of Al2O3 and Al2O3/Nb/Al2O3 specimens are discussed.