Direct Evidence for Cation Non‐Stoichiometry and Cottrell Atmospheres Around Dislocation Cores in Functional Oxide Interfaces

Mapping grain boundary heterogeneity at the nanoscale in a positive temperature coefficient of resistivity ceramic

“…The Pb segregation and Ba reduction observed here can be assumed to be attributed to A-site substitutions within the ABO 3 perovskite structure. Grain boundaries are well known for their disordered nature, formed by structural defects or dislocation cores, 24 and Pb being more volatile could be attracted to these defective (and highly strained) areas during sintering, 25 hence explaining the chemical heterogeneity observed here. It should be noted that the extent of Pb segregation could differ from one grain to another due to each grain developing slightly different strain gradients during the sintering process.…”

Chemistry of Ruddlesden–Popper planar faults at a ferroelectric–ferromagnet perovskite interface

“…23,24 We show next that the R-P faults are formed due to significant mass transport of Pb, resulting in the formation of PbO planar faults; at the outset the distance to which the Pb has diffused appears excessively large. However we highlight our theoretical model 11 which finds that stress values as low as 1.1 Â 10 9 N m À2 are sufficient to effect mass transport of Pb over distances of the order of few nm in order to relax the misfit strains at the perovskite ferroelectric-electrode interface.…”

“…High-resolution studies, including Z-contrast imaging and EDX mapping (with a step size of 0.5 nm), 11 were performed using a double-corrected (C s ) FEI Titan 80-300 FEGTEM, operated at 300 kV, using a convergence semiangle of 15.1 mrad and annular detector inner and outer radii of 40 mrad and 250 mrad, respectively.…”

“…The results reported here are consistent with recent similar findings on misfit dislocations, where we showed that the local strain fields associated with the dislocation core are high enough to create cation diffusion into the core. 11 …”

Analytical Aberration-Corrected STEM of Ferroelectric Functional Interfaces

“…As an essential corollary to these instrumentation developments, significant increases in detection limits and signal-to-noise ratios were achieved such that the improved data collection ability and greater flexibility of the instruments have arguably proved the most beneficial advances for the materials sciences community, allowing users to utilise efficiently all available analytical signals. These benefits are particularly evident in the specific example of the chemical structure of dislocation cores in ultra-thin ferroelectric PbZr 0.2 Ti 0.8 O 3 oxide films [3]. The current trend of aggressive downsizing of the building blocks of silicon electronics has resulted in the functional material being confined to nanometric size volume and the presence of even a single defect and its associated longrange field could indeed adversely affect the performance and/or reliability of the device.…”