Imprinting oxides: Dislocations can be problematic for the properties of functional oxides and are often avoided as a result. Höfling et al. found that introducing a network of dislocations to barium titanate actually enhanced the dielectric and piezoelectric properties. The authors introduced the dislocation network with uniaxial compression, which forced the material to have a domain structure that enhanced the piezoelectric coefficient by a factor of 19. This strategy should be a useful tool for optimizing properties of other functional oxides. Science , abe3810, this issue p. 961

Dislocations are usually expected to degrade electrical, thermal and optical functionality and to tune mechanical properties of materials. Here, we demonstrate a general framework for the control of dislocation–domain wall interactions in ferroics, employing an imprinted dislocation network. Anisotropic dielectric and electromechanical properties are engineered in barium titanate crystals via well-controlled line-plane relationships, culminating in extraordinary and stable large-signal dielectric permittivity (≈23100) and piezoelectric coefficient (≈2470 pm V^–1). In contrast, a related increase in properties utilizing point-plane relation prompts a dramatic cyclic degradation. Observed dielectric and piezoelectric properties are rationalized using transmission electron microscopy and time- and cycle-dependent nuclear magnetic resonance paired with X-ray diffraction. Succinct mechanistic understanding is provided by phase-field simulations and driving force calculations of the described dislocation–domain wall interactions. Our 1D-2D defect approach offers a fertile ground for tailoring functionality in a wide range of functional material systems.

We report an intrinsic strain engineering, akin to thin filmlike approaches, via irreversible high-temperature plastic deformation of a tetragonal ferroelectric single-crystal ${\mathrm{BaTiO}}_3$. Dislocations well-aligned along the [001] axis and associated strain fields in plane defined by the $[110]/[\overline{1}10]$ plane are introduced into the volume, thus nucleating only in-plane domain variants. By combining direct experimental observations and theoretical analyses, we reveal that domain instability and extrinsic degradation processes can both be mitigated during the aging and fatigue processes, and demonstrate that this requires careful strain tuning of the ratio of in-plane and out-of-plane domain variants. Our findings advance the understanding of structural defects that drive domain nucleation and instabilities in ferroic materials and are essential for mitigating device degradation.

Residual stress and plastic strain in additive manufactured materials can exhibit significant microscopic variation at the powder scale, profoundly influencing the overall properties of printed components. This variation depends on processing parameters and stems from multiple factors, including differences in powder bed morphology, non-uniform thermo-structural profiles, and inter-layer fusion. In this research, we propose a powder-resolved multilayer multiphysics simulation scheme tailored for porous materials through the process of selective laser sintering. This approach seamlessly integrates finite element method (FEM) based non-isothermal phase-field simulation with thermo-elasto-plastic simulation, incorporating temperature- and phase-dependent material properties. The outcome of this investigation includes a detailed depiction of the mesoscopic evolution of stress and plastic strain within a transient thermo-structure, evaluated across a spectrum of beam power and scan speed parameters. Simulation results further reveal the underlying mechanisms. For instance, stress concentration primarily occurs at the necking region of partially melted particles and the junctions between different layers, resulting in the accumulation of plastic strain and residual stress, ultimately leading to structural distortion in the materials. Based on the simulation data, phenomenological relation regarding porosity/densification control by the beam energy input was examined along with the comparison to experimental results. Regression models were also proposed to describe the dependency of the residual stress and the plastic strain on the beam energy input.