Defects are essential to engineering the properties of functional materials ranging from semiconductors and superconductors to ferroics. Whereas point defects have been widely exploited, dislocations are commonly viewed as problematic for functional materials and not as a microstructural tool. We developed a method for mechanically imprinting dislocation networks that favorably skew the domain structure in bulk ferroelectrics and thereby tame the large switching polarization and make it available for functional harvesting. The resulting microstructure yields a strong mechanical restoring force to revert electric field–induced domain wall displacement on the macroscopic level and high pinning force on the local level. This induces a giant increase of the dielectric and electromechanical response at intermediate electric fields in barium titanate [electric field–dependent permittivity (ε33) ≈ 5800 and large-signal piezoelectric coefficient (d33*) ≈ 1890 picometers/volt]. Dislocation-based anisotropy delivers a different suite of tools with which to tailor functional materials.

The oxidation of neopentane was studied in jet-stirred reactors at atmospheric pressure over a temperature range 500–850 K and ϕ = 0.5. The products were analyzed with chromatographic, mass spectrometric, and photoelectron spectroscopic setups complemented with theoretical calculations. This combination provides a comparison of photo-ionization mass spectrometry and gas chromatography for the quantification of mole fractions and highlights the relevant differences between them, while mass-tagged photoelectron spectroscopy sheds light onto the isomeric distribution. The new data and corresponding analyses are expected to provide valuable guidance for an extension of the kinetic model and the choice of experimental methods. The main first and second O2-addition products were observed in agreement with the literature (e.g., 3,3-dimethyloxetane, acetone, isobutene, and γ-ketohydroperoxide). The simulated mole fractions of the products using a literature kinetic model were compared to the experimental results. Even though the kinetic model has been validated previously, significant discrepancies between the measured and simulated mole fractions of 2-methylpropanal and methacrolein, two fuel-specific low-temperature oxidation products, were found. Furthermore, some experimentally observed species related to γ-ketohydroperoxide decomposition were not predicted indicating that the model is incomplete. The detection of 2-methylpropanal and formic acid highlighted the importance of the Korcek-type pathway.

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The in situ biasing transmission electron microscopy technique is employed to investigate the nucleation and growth of the ferroelectric phase during the electric field-induced phase transition in Pb 0.99 {Nb 0.02 [(Zr 0.57 Sn 0.43 ) 0.94 Ti 0.06 ] 0.98 }O 3 , a PbZrO 3 -based antiferroelectric ceramic. The first-order displacive phase transition is found to be highly reversible with the initial antiferroelectric domain configuration almost completely recovered upon removal of the applied field. In the forward transition from the antiferroelectric to ferroelectric phase, {100} c facets are dominant on the phase boundary; while in the reverse transition from the ferroelectric to antiferroelectric phase during bias unloading, the phase boundary is segmented into {101} c and {121} c facets. The motion of the phase boundary is nonuniform, taking the form of sequential sweeping of facet segments. The elastic distortion energy and the depolarization energy at the antiferroelectric/ferroelectric phase boundary is suggested to dictate the facet motion.