Studying the Behavior of Relaxors, Antiferroelectrics and Ferroelectric Materials with Cryogenic/In Situ STEM

Determining the chemical and structural order/disorder within functional oxides is often key to understanding their properties as a function of temperature and electric field. This is particularly true in relaxor ferroelectrics and antiferroelectrics. To achieve this, cryogenic and in situ STEM have emerged as powerful tools for exploring phase transitions in these functional oxides.<br/><br/>In this talk, I will delve into the application of cryogenic aberration-corrected scanning transmission electron microscopy (STEM) to directly discern nanoscale structural changes at the atomic level in relaxor ferroelectric and antiferroelectric materials, complementing diffraction studies and room-temperature information. By acquiring images sensitive to chemistry (angle annular dark-field STEM) and light elements (integrated differential phase contrast STEM) under cryogenic conditions, we establish direct correlations between nanoscale chemical order regions, distorted oxygen octahedra, and local polarization concerning temperature and/or applied biasing.<br/><br/>Additionally, we will discuss the correlation of antiphase boundaries in an antiferroelectric material with local chemical disorder and their behavior as a function of temperature. Further, multislice ptychography will be shown to enable the disambiguation of various structural and chemical boundary models, concluding that the boundary is inclined and disordered compared to the ‘bulk’ thin film. Moreover, antiferroelectric nanodomains reside within the chemically disordered regions of the antiphase boundaries.