Flash sintering of Al₂O₃–ZrO₂ ceramics under alternating current electric field

In this study, the influence of alternating current (AC) electric field on flash sintering and microstructural evolution of alumina–zirconia (Al₂O₃–ZrO₂) composite was systematically investigated at furnace temperature of 800 °C. Compared with direct current (DC) electric field, AC electric field not only promoted densification and grain growth of Al₂O₃–ZrO₂ composite, but also improved the uniformity of microstructure of ceramics. Grain size of AC flash-sintered samples was found to be inversely related to electric field, and positive correlation was observed with current density limit. Dense Al₂O₃–ZrO₂ composite ceramic was fabricated via AC flash sintering under 60 mA mm⁻² at low furnace temperature within 120 s, and as-sintered samples exhibited relatively good mechanical properties. The mechanism involving synergistic effect of Joule heating and defects generation under the influence of electric field was proposed to explain rapid densification during AC flash sintering. These results indicate the feasibility of preparation of dense composite ceramic with homogeneous microstructure via AC flash sintering.