Defect Structure of Flash‐Sintered Strontium Titanate

Flash sintering of strontium titanate ( SrTiO 3 ) is studied at different applied fields to understand its effect on density and grain growth. In particular, the defect structure is investigated by optical and structural analysis. SrTiO 3 exhibited a trend in densification opposite that of ionically or electronically conductive ceramics: as the applied voltage decreased, the density increased. Abnormal grain growth in conventionally sintered SrTiO 3 is arrested by flash sintering. Interestingly, undoped SrTiO 3 behaved differently than undoped Al 2 O 3 , which did not exhibit any signs of flash sintering. Previous attempts at flash sintering could only be achieved in MgO ‐doped Al 2 O 3 . We believe that non‐stoichiometric Ruddlesden‐Popper phases in SrTiO 3 , as indicated by ultrafast optical spectroscopy, X ‐ray diffraction, conductivity measurements, and transmission electron microscopy, assist flash sintering by increasing local conductivity through enhanced defect content.