Indentation response of pulsed electric current sintered polymer derived HfO2/Si–C–N(O) nanocomposites

The influence of pulsed electric current sintering on the structural evolution and indentation response of hafnia incorporated silicon carbonitride polymer derived ceramics was studied. Despite the absence of any sintering additives, appreciable sintering at 1400 °C with a density of ∼2.7 g/cc was observed. Sintering beyond 1300 °C resulted in the phase separation and nano-crystallization of amorphous Si–Hf–C–N–O ceramic. The crystallite coarsening was insignificant and thereby the tetragonal phase of hafnia was retained in the ceramic nanocomposite. A relatively high indentation hardness and elastic modulus of ∼18 GPa and ∼313 GPa were determined by depth sensing nanoindentation technique.