SPS APPARATUS AS A HIGH-TEMPERATURE CREEP TESTING DEVICE FOR ADVANCED CERAMICS

The spark plasma sintering (SPS) apparatus keeps growing steadily in popularity due to its excellent sintering capabilities. The data output of the SPS system includes temperature, applied pressure, relative punch displacement (RPD) and electric pulse parameters (i.e., voltage, mode of current, frequency, etc.). In principle, the SPS apparatus is a high temperature dilatometer and can be used for the investigation of mechanical properties of ceramics at high temperatures. The accuracy of RPD measurements (about 1 µm) is suitable for high temperature experiments, such as creep. We have successfully demonstrated that the apparatus can be applied as a high-temperature creep testing device for advanced ceramics. Using hybrid high-pressure SiC SPS tooling, creep experiments were performed on alumina (in the temperature range of 1125-1250°C under 80-120 MPa). Apparent activation energies and stress exponent values were determined (Q=454, n=1.9-2.1). The apparent activation energy for spinel decreased with applied stress, while the stress exponent decreased with temperature. The observed creep behavior (i.e creep parameters Q and n) in the tested regime as well as microstructure evidence of deformed samples (such as grain boundary cavities and equiaxed grains) fits the creep mechanism of grain boundary sliding accommodated by dislocation climb or glide and are in good agreement with the reported data in literature.