Densification and Structure Evolution of ZrB2-ZrO2 Composites Prepared by Plasma Activated Sintering using ZrB2@ZrO2 Powder

The densification and the structure evolution of the plasma activated sintered (PAS sintered) ZrB2-ZrO2 composite via the ZrO2-coated ZrB2 powder (ZrB2@ZrO2) prepared by in situ passivation method were investigated. The composition and microstructure were characterized by XRD, Raman, SEM, and EDS techniques. The coated powder has excellent sintering performance. The relative density of the composite reaches above 90% at 1 200 °C, and the main sintering process occurs between ZrO2 particles. While at above 1 500 °C, the relative density reaches above 95% and the main sintering process occurs between ZrB2 and ZrO2 particles. With the increase of ZrO2 coating content, the structure of the sintered body changes from ZrB2 continuous network structure to island structure. When the content is 20%, an island structure is formed. Increasing the ZrO2 content further causes the overheating of ZrO2. Thus, the best sintering performance reaches when the coating content is 20wt%.