Lithiation dynamics and phase transition mechanisms in most battery cathode materials remain poorly understood, because of the challenge in differentiating inter- and intra-particle heterogeneity. In this work, the structural evolution inside Li_1−xMn_1.5Ni_0.5O₄ single crystals during electrochemical delithiation is directly resolved with operando X-ray nanodiffraction microscopy. Metastable domains of solid-solution intermediates do not appear associated with the reaction front between the lithiated and delithiated phases, as predicted by current phase transition theory. Instead, unusually persistent strain gradients inside the single crystals suggest that the shape and size of solid solution domains are instead templated by lattice defects, which guide the entire delithiation process. Morphology, strain distributions, and tilt boundaries reveal that the (Ni²⁺/Ni³⁺) and (Ni³⁺/Ni⁴⁺) phase transitions proceed through different mechanisms, offering solutions for reducing structural degradation in high voltage spinel active materials towards commercially useful durability. Dynamic lattice domain reorientation during cycling are found to be the cause for formation of permanent tilt boundaries with their angular deviation increasing during continuous cycling.

Achieving substantial electrostrain alongside a large effective piezoelectric strain coefficient (d₃₃*) in piezoelectric materials remains a formidable challenge for advanced actuator applications. Here, a straightforward approach to enhance these properties by strategically designing the domain structure and controlling the domain switching through the introduction of arrays of ordered {100} dislocations is proposed. This dislocation engineering yields an intrinsic lock‐in steady–state electrostrain of 0.69% at a low field of 10 kV cm⁻¹ without external stress and an output strain energy density of 5.24 J cm⁻³ in single‐crystal BaTiO₃, outperforming the benchmark piezoceramics and relaxor ferroelectric single‐crystals. Additionally, applying a compression stress of 6 MPa fully unlocks electrostrains exceeding 1%, yielding a remarkable d₃₃* value over 10 000 pm V⁻¹ and achieving a record‐high strain energy density of 11.67 J cm⁻³. Optical and transmission electron microscopy, paired with laboratory and synchrotron X‐ray diffraction, is employed to rationalize the observed electrostrain. Phase‐field simulations further elucidate the impact of charged dislocations on domain nucleation and domain switching. These findings present an effective and sustainable strategy for developing high‐performance, lead‐free piezoelectric materials without the need for additional chemical elements, offering immense potential for actuator technologies.

We study the complex ferroelastic/ferroelectric domain structure in the prototypical ferroelectric PbTiO3 epitaxially strained on (110)o-oriented DyScO3 substrates, using a combination of atomic force microscopy, laboratory and synchrotron x-ray diffraction, and high resolution scanning transmission electron microscopy. We observe that the anisotropic strain imposed by the orthorhombic substrate creates a large asymmetry in the domain configuration, with domain walls macroscopically aligned along one of the two in-plane directions. We show that the periodicity as a function of film thickness deviates from the Kittel law. As the ferroelectric film thickness increases, we find that the domain configuration evolves from flux-closure to a/c-phase, with a larger scale arrangement of domains into superdomains.

The influence of edge-type threading dislocations (TDs) on the epitaxial growth of AlGaN on native AlN substrates was investigated theoretically and experimentally. In the step flow growth regime, we find that pure edge-type TDs cause a pinning of surface steps, resulting in curved step segments. Theoretical calculations reveal that this pinning mechanism is solely mediated by the altered surface potential due the strain field imposed by the TD. Within the curved step segment, the step width is subject to changes resulting in an altered Ga/Al incorporation rate. According to the density functional theory calculation, this effect is related to the different surface diffusion length of Ga and Al and represents a further destabilization mechanism during step flow growth. Another consequence of surface step pinning is the occurrence of areas where the step width is increased. These areas serve as precursors for 2D nucleation due to an increased adatom density. Once nucleated, these nuclei grow along the c-direction via continuous 2D nucleation, while lateral expansion occurs due to adatom incorporation on the m-facets.

Electrical aging in lead zirconate titanate (PbZr_xTi_1−xO₃) thin films has been intensively studied from a macroscopic perspective. However, structural origins and consequences of such degradation are less documented. In this study, we have used synchrotron radiation to evaluate the behavior of ferroelectric domains by X-ray diffraction (XRD). The sample was loaded with an AC triangular bias waveform between ±10 V with a number of cycle varying from one up to 10⁸. At each step of the aging procedure, XRD spectra had been collected in situ during the application of an electric field on a capacitor. The fine analysis of the (200) pseudo-cubic peak structure allows to separate the evolution of the volume of a/c tetragonal and rhombohedral domains along the electrical biasing. Throughout the aging, both intrinsic and extrinsic responses of tetra and rhombohedral domains are altered, the behavior depending on the observed phase. This methodology opens up new perspectives in the comprehension of the aging effect in ferroelectric thin film.