Fabricating a Novel Intragranular Microstructure for Al₂O₃/GdAlO₃ Ceramic Composites

In order to make the embryonic form of intragranular structure, the Al₂O₃/GdAlO₃ system was selected due to its excellent mechanical properties. Gd₂O₃ and Al(NO₃)₃·9H₂O were used as the starting materials. A co-precipitation method was used for the preparation of fine ceramics and applied to synthesize the nano-powder of GdAlO₃ firstly. Then, the nano-powder of GdAlO₃ was mixed with the precipitates by the second co-precipitation method. After drying and calcination, the compound powder with eutectic composition (77 mol % Al³⁺-23 mol % Gd³⁺) was fast sintered by using the spark plasma sintering technique. The results revealed that the phases of the sintered samples were Al₂O₃ and GdAlO₃. The phases showed a homogeneous and interlaced distribution. All the matrix grains were submicron. The sizes of the intragranular structures were between 50 nm and 150 nm. Therefore, the intragranular structure displayed a novel mixture of nanometer⁻submicron and submicron⁻submicron types. The different intragranular structures all changed the fracture modes of Al₂O₃ grains from intergranular fracture to transgranular fracture.