Defect structure of flash-sintered strontium titanate

Abstract

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 2O 3, which did not exhibit any signs of flash sintering. Previous attempts at flash sintering could only be achieved in MgO-doped Al 2O 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. © 2012 The American Ceramic Society.