Microwave hybrid and conventional sintering of Al2O3 and Al2O3/ZrO2 multilayers fabricated by aqueous tape casting

In this study, microwave hybrid sintering and conventional sintering of Al2O3- and Al2O3/ZrO2-laminated structures fabricated via aqueous tape casting were investigated. A combination of process temperature control rings and thermocouples was used to measure the sample surface temperatures more accurately. Microwave hybrid sintering caused higher densification and resulted in higher hardness in Al2O3 and Al2O3/ZrO2 than in their conventionally sintered counterparts. The flexural strength of microwave-hybrid-sintered Al2O3/ZrO2 was 70.9% higher than that of the conventionally sintered composite, despite a lower sintering temperature. The fracture toughness of the microwave-hybrid-sintered Al2O3 increased remarkably by 107.8% despite a decrease in the relative density when only 3 wt.% t-ZrO2 was added. The fracture toughness of the microwave-hybrid-sintered Al2O3/ZrO2 was significantly higher (247.7%) than that of the conventionally sintered composite. A higher particle coordination and voids elimination due to the tape casting and the lamination processes, the microwave effect, the stress-induced martensitic phase transformation, and the grain refinement phenomenon are regarded as the main reasons for the mentioned outcomes.

Automated summary

This study investigated the microwave hybrid sintering and conventional sintering of Al2O3- and Al2O3/ZrO2-laminated structures fabricated via aqueous tape casting. Microwave hybrid sintering resulted in higher densification and hardness compared to conventional sintering. The flexural strength and fracture toughness of the microwave-hybrid-sintered Al2O3/ZrO2 were significantly higher than those of the conventionally sintered composite, despite a lower sintering temperature. The outcomes were attributed to the tape casting and lamination processes, microwave effects, stress-induced martensitic phase transformation, and grain refinement phenomenon.