In situ studies on defect formation dynamics in flash-sintered TiO₂

Conventional sintering methods produce ceramics with limited mechanical flexibility. Recent studies have shown flash-sintered (FS) ceramics exhibit improved room-temperature deformability. This property is thought to arise from high-density defects formed during flash sintering. However, direct experimental evidence of defect formation and evolution remains scarce. Prior research has shown that defects like dislocations and stacking faults can influence material properties. No prior work had resolved how electric fields affect defect dynamics in FS ceramics. This gap motivated the need for in situ studies. Transmission electron microscopy (TEM) allows real-time observation of defect behavior. This paper contributes by comparing defect evolution in FS and conventionally sintered TiO₂. The study addresses a key uncertainty in ceramic deformation mechanisms.

The aim of this work is to investigate how electric fields influence defect formation and evolution in flash-sintered and conventionally sintered TiO₂. The specific problem involves understanding the mechanisms behind enhanced deformability in FS ceramics. The motivation stems from the lack of direct experimental evidence for defect dynamics under electric fields. The study compares defect evolution in FS and CS TiO₂ using in situ TEM. The researchers propose that electric fields may accelerate defect coalescence. This approach allows for real-time observation of stacking fault formation. The study focuses on Wadsley defects and their growth rates. The goal is to provide insights into the role of electric fields in defect dynamics.

The researchers used in situ biasing experiments in a transmission electron microscope (TEM). They compared flash-sintered (FS) and conventionally sintered (CS) polycrystalline TiO₂ samples. The experiments involved applying an electric field while observing defect evolution in real time. The TEM allowed for direct visualization of point defect coalescence. Stacking faults were identified as Wadsley defects during the study. The growth rates of these defects were measured in both FS and CS samples. The researchers tracked the formation of Magnéli phase in the FS samples. The study focused on defect dynamics under controlled electric field conditions.

In situ TEM revealed point defect coalescence under electric fields in both FS and CS TiO₂. Stacking faults, known as Wadsley defects, formed as a result of this coalescence. The average fault growth rate in FS samples was 10 times higher than in CS samples. This suggests electric fields accelerate defect evolution in FS ceramics. Magnéli phase, a 3D oxygen-deficient structure, was observed only in FS samples. This phase forms through aggregation of Wadsley defects. The study provides direct evidence of defect dynamics under electric fields. These findings highlight differences between FS and CS defect evolution.

The study shows that electric fields significantly influence defect formation in flash-sintered TiO₂. The observed 10-fold increase in fault growth rate in FS samples supports the role of electric fields in defect dynamics. The presence of Magnéli phase in FS samples suggests unique defect aggregation. These findings align with the authors' claim that electric fields enhance defect evolution. The results provide new insights into the mechanisms behind deformability in FS ceramics. The study confirms that Wadsley defects form under electric fields in both FS and CS samples. The authors propose that electric fields may be central to defect dynamics in FS ceramics. These conclusions trace directly to the authors' stated findings.