The effect of lanthanum on the fabrication of ZrB2–ZrC composites by spark plasma sintering

The effect of the addition of the rare earth element, lanthanum, on the sintering characteristics of ZrB2–ZrC composites has been analyzed during a spark plasma sintering (SPS) process. Microscopic observation confirmed that lanthanum accelerated mass transport by the formation of the liquid phase between the particles induced by the spark plasma in the initial stage of the SPS process, and then these were recrystallized to form a lanthanum-containing secondary phase at the grain boundaries and at the grain boundary triple junctions. In spite of the strong covalent bonding characteristics of the ZrB2–ZrC composite there are many well-developed dislocation structures observed. acture toughness of the lanthanum-containing ZrB2–ZrC is about 2.56 MPa m1/2, which is comparable to that of the pure composite. Therefore, it is concluded that lanthanum is very effective as a sintering aid for the ZrB2–ZrC composite without any degradation of the mechanical properties.