Ultra-Rapid Crystal Growth of Textured SiC Using Flash Spark Plasma Sintering Route

Abstract

A novel processing route that induces simultaneous densification and texturing of SiC ceramics by Flash Spark Plasma Sintering (FSPS) is reported. Unlike hot forging (which produces texturing in a direction orthogonal to the load as a result of plastic deformation), FSPS produced texturing parallel to the pressing direction. The texturing was driven by a thermal gradient generated within the sample along its axial direction due to the higher electrical resistivity of SiC compared to the pressing graphite punch (the sample midthickness was hotter than the surfaces in contact with the graphite punches). In FSPSed SiC samples, the microstructure consisted of large SiC plate-like elongated crystals (thickness between 40 and 100 μm, width up to 500 μm) with their c-axis (slow growth direction) orthogonal to the Physical Vapor Transport (PVT) direction. The mechanisms producing densification and texture were studied for SiC with and without boron carbide sintering additives. In order to achieve a dense and textured portion of the sample, the presence of a liquid phase during sintering was necessary.