Electric Current-Assisted Sintering of 8YSZ: A Comparative Study of Ultrafast High-Temperature Sintering and Flash Sintering

Electric current-assisted sintering (ECAS) is a promising powder consolidation technique that can achieve short-term sintering with high heating rates. Currently, main methods of performing ECAS are indirect heating of the powder compact in a conductive tool or direct heating with current flowing through the powder compact. Various influencing factors have been identified to explain the rapid densification during ECAS, such as ultrahigh heating rates, extra-high temperatures, and electric field. However, the key consolidation-enhancing factor is still under debate. This study aims at understanding the role of heating rate on the enhanced densification during ECAS of 8 mol% Y₂O₃-stabilized ZrO₂ (8YSZ) by experimental and numerical methods. Two different heating modes, ultrafast high-temperature sintering (UHS, indirect heating) and flash sintering (FS, direct heating), are studied. The novel UHS technique is successfully applied to consolidate the 8YSZ samples. Additionally, finite element methods (FEM) combined with a constitutive model is adopted to predict the densification and grain growth. Furthermore, a comparison of UHS and FS is performed to investigate the thermal effect (heating rate) and athermal effect (electric field) individually. The results indicate that the high heating rate is the key factor of the rapid densification during UHS and FS of 8YSZ.