Enhancing microstructure homogeneity and electrical conductivity in flash-sintered 8YSZ: Impact of electric-current ramp control and thermal insulation

Our study aimed to comprehend how variations in flash sintering parameters affect the evolution of microstructure and electrical properties of yttria-stabilised zirconia. For this purpose, cylindrical samples were sintered via a classic flash method (voltage-current control), with controlled increase in the current ramp, employing thermal insulation, and combining current ramp control with thermal insulation. The results demonstrated that the combination of current ramp control and thermal insulation yielded higher densification compared to other variations. Microstructural analysis revealed finer grain sizes and lower grain-boundary tensions on employing current ramp control, particularly when combined with thermal insulation. For all flash-sintering methods, greater electrical conductivity of grain boundaries was observed compared to conventional sintering, suggesting an enhancement in ionic conduction. This study underscores the potential of customised FS techniques in optimising sintering processes and enhancing material properties.