A TEM study on the microstructure of spark plasma sintered ZrB₂-based composite with nano-sized SiC dopant

Sintering behavior of ZrB₂ ceramic with nano-sized SiC dopant was studied. ZrB₂-25 ​vol% nano-sized SiC was selected as the starting mixture to fabricate the composite. The manufacturing process was accomplished at 1800 ​°C for 5 ​min under 25 ​MPa via spark plasma sintering (SPS). The as-sintered sample reached a relative density of 99%. Besides the initial phases, namely ZrB₂ and SiC, the high-resolution X-ray diffraction (HRXRD) was used to study the formation of an in-situ ZrC phase. The possible chemical interactions during the ZrC phase formation were scrutinized. The microstructure of the composite was studied by the field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Elemental analysis through FESEM evaluations revealed the formation of amorphous phases, rich in Zr, C, Si, B, and O elements, which was in harmony with the thermodynamical assessments. TEM studies endorsed the formation of such phases, containing a glassy bed of Si–B–O with ZrC and C islands dispersed therein.