Characterization of textured ceramics containing mullite from phyllosilicates

Organized ceramics are obtained from kaolinite and muscovite suspensions and shaped by aqueous tape casting or centrifugation. These processes favor the preferential orientation of particles in the powder compact. After sintering at 1400 °C, this study analyzed sample microstructures using QTA to determine the degree of the mullite orientation. The analyses revealed two main texture components, a planar texture along the c-axis of the mullite and a preferred orientation along the a-axis, which were aligned parallel and perpendicular to the casting plane, respectively. The important role of processing parameters in the organization degree of the mullite was apparent during the study. The elastic properties at different measurement scales were obtained using US echography and nanoindentation and were closely related to the organization degree of the mullite crystals obtained from the QTA analyses that were consistent with the development of an interconnected mullite network. The Young's moduli due to the nanoindentations were also determined parallel and perpendicular to the layers, and indicated the samples' anisotropic behavior. Both the Young's modulus and the anisotropy of the Young's modulus were correlated with the texture index. In particular, the anisotropy of the Young's moduli was linearly related to the overall texture index, highlighting the microstructures' anisotropic nature.