Metal halide perovskites (MHPs) combine excellent optoelectronic properties with strong X-ray attenuation, offering a promising platform for high performance and adaptable radiation detectors beyond the limitations of conventional rigid semiconductors. However, state of the art performance has so far been restricted to rigid single crystal perovskite devices, while flexible film-based counterparts have significantly lagged. Here, we close this gap by embedding a polymer-perovskite composite into a mechanically robust yet flexible Teflon membrane. Through comprehensive spectroscopic analysis, we provided direct evidence for a dual-action interaction mechanism, where PMA passivates the inorganic Pb²⁺ lattice to enhance phase stability while also interacting with the organic FA⁺ cations to promote a more ordered local environment. This interaction enhances crystallinity and suppresses non-radiative recombination. As a result, our flexible detectors deliver an outstanding sensitivity of 2.3 × 10⁵ µC Gy_air⁻¹ cm⁻² and an ultra-low detection limit of 0.09 nGy_air s⁻¹. Importantly, this high performance is accompanied by excellent device to device reproducibility, long term stability in ambient conditions, and robust mechanical durability under bending. This work presents a comprehensive strategy for developing flexible perovskite based X-ray detectors that simultaneously achieve record sensitivity and practical reliability, enabling the development of next-generation wearable and medical imaging applications.

Anode-free sodium ion batteries (SIBs) promise higher energy density and lower costs, by eliminating the need for an anode host material; however, achieving efficient Na plating/stripping remains a major challenge. Here, three electrolyte classes − carbonate-based, glyme-based, and a localized high-concentration electrolyte−are evaluated for Na plating/stripping on a commercial carbon-coated aluminium current collector. Measurements across a broad temperature and current range (−30°C–+60°C, 0.25–14 mA cm⁻²⁻) and studies on the Na growth modes by operando optical microscopy reveal the superior behavior of the glyme-based electrolyte, including a uniform crystalline metal deposition. In anode-free full cells with Na₄Fe₃(PO₄)₂P₂O₇ as cathode, this electrolyte enables superior cycling with 75.3% capacity retention over 400 cycles at areal loadings above 3 mAh cm⁻²⁻. Projected energy densities of 290 Wh/kg and 751 Wh/l are calculated at the cell-stack level, exceeding current LiFePO₄-based Li-ion batteries. The excellent Na plating/stripping behavior is evidenced by a particularly low initial areal capacity loss (IACL, mAh cm⁻²). The IACL parameter represents the first cycle Na inventory loss that must be compensated by the cathode. Unlike for conventional Na-ion cells with traditional anodes, the IACL is a constant for anode-free cells. For the given cell, the IACL amounts to only 0.14–0.16 mAh cm⁻² (~5% of the 3 mAh cm⁻² cathode areal capacity). This highlights the potential of anode-free SIBs using commercially available components.

The pinning-controlled mobility of ferroelectric/ferroelastic domain walls is an important part of managing polarization switching and determining the final properties of ferroelectric and piezoelectric materials. Here, we assess the impact of temperature on dislocation-induced domain wall pinning as well as on dislocation-tuned dielectric and piezoelectric response in barium titanate single crystals. Our solid-state nuclear magnetic resonance spectroscopy results indicate that the entire sample exclusively permits in-plane domains, with their distribution remaining insensitive to temperature changes below the Curie temperature (T_C). The domain wall pinning field monotonically decreases with increasing temperature up to T_C, as evidenced by a combination of experimental observations and phase-field simulations. Our work highlights the promising potential of dislocation engineering in controlling domain wall mobility within bulk ferroelectrics.

“Medium-entropy” highly disordered amorphous Li garnets, with ≥4 unique local bonding units (LBUs), hold promise for use as solid-state electrolytes in hybrid or all-solid-state batteries owing to their grain-boundary-free nature and low-temperature synthesis requirement. Through this work, we resolved the local structure of amorphous Li garnet and understood their implication for Li dynamics. These medium-entropy amorphous structures possess unique characteristics with edge- and face-sharing LBUs, not conforming to the classic Zachariasen glass formation rules, and can be synthesized in a wide but processing-friendly temperature range (<680°C). Within these amorphous structures, Li and Zr are identified as the network formers and La as network modifier, with maxima in Li dynamics observed for smaller Li–O and Zr–O coordination; this structure understanding serves as a baseline for identifying additional network formers to further modulate Li transport. Our insight provides fundamental guidelines for the structure and phase design for amorphous Li garnets and paves the way for their integration in next-generation batteries.

Unlike metals where dislocations carry strain singularity but no charge, dislocations in oxide ceramics are characterized by both a strain field and a local charge with a compensating charge envelope. Oxide ceramics with their deliberate engineering and manipulation are pivotal in numerous modern technologies such as semiconductors, superconductors, solar cells, and ferroics. Dislocations facilitate plastic deformation in metals and lead to a monotonous increase in the strength of metallic materials in accordance with the widely recognized Taylor hardening law. However, achieving the objective of tailoring the functionality of oxide ceramics by dislocation density still remains elusive. Here a strategy to imprint dislocations with {100}<100> slip systems and a tenfold change in dislocation density of BaTiO₃ single crystals using high-temperature uniaxial compression are reported. Through a dislocation density-based approach, dielectric permittivity, converse piezoelectric coefficient, and alternating current conductivity are tailored, exhibiting a peak at medium dislocation density. Combined with phase-field simulations and domain wall potential energy analyses, the dislocation-density-based design in bulk ferroelectrics is mechanistically rationalized. These findings may provide a new dimension for employing plastic strain engineering to tune the electrical properties of ferroics, potentially paving the way for advancing dislocation technology in functional ceramics.

Tailoring the electromechanical properties of a material without altering the original composition is an emerging phenomenon for the optimization of functional properties. Post-sintering annealing with varying maximum temperatures, cooling rates, and atmospheres can influence the crystallographic phases, domain structures, conductivity, mechanical properties, and the temperature stability of the electromechanical properties. K_1/2Bi_1/2TiO₃ (KBT) is a high-temperature stable >280 °C A-site complex perovskite piezoelectric and is critical for high-temperature applications. However, the influence of annealing conditions on crystal structure, domain structure, and functional properties is not well-known. This work demonstrates the effect of annealing cooling rate and maximum temperature on the macroscopic electromechanical response as well as the crystal and domain structure. It is shown that the room-temperature state of KBT can be reversibly switched between the ferroelectric and relaxor state, where the slow cooling from 900 °C favors the stabilization of the relaxor state and quenching induces the ferroelectric state. Importantly, the quenched sample showed a stable piezoelectric coefficient up to 368 °C in the depolarization temperature, an increase of 78 °C. The origin of ferroelectric-relaxor state change is proposed to be related to the A-site cation redistribution and the associated change in the crystal structure and domain structure.

We report an intrinsic strain engineering, akin to thin filmlike approaches, via irreversible high-temperature plastic deformation of a tetragonal ferroelectric single-crystal BaTiO3. Dislocations well-aligned along the [001] axis and associated strain fields in plane defined by the [110]/[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.

Reversible field-induced phase transitions define antiferroelectric perovskite oxides and lay the foundation for high-energy storage density materials, required for future green technologies. However, promising new antiferroelectrics are hampered by transition´s irreversibility and low electrical resistivity. Here, we demonstrate an approach to overcome these problems by adjusting the local structure and defect chemistry, delivering NaNbO₃-based antiferroelectrics with well-defined double polarization loops. The attending reversible phase transition and structural changes at different length scales are probed by in situ high-energy X-ray diffraction, total scattering, transmission electron microcopy, and nuclear magnetic resonance spectroscopy. We show that the energy-storage density of the antiferroelectric compositions can be increased by an order of magnitude, while increasing the chemical disorder transforms the material to a relaxor state with a high energy efficiency of 90%. The results provide guidelines for efficient design of (anti-)ferroelectrics and open the way for the development of new material systems for a sustainable future.

High-resolution scanning transmission electron microscopy (STEM) enjoys great advantages for atomic-resolution visualization of the atomic structure, while failing to disclose structural information along the atomic columns. On the other hand, solid-state nuclear magnetic resonance (NMR) spectroscopy is highly sensitive to the three-dimensional, local structure around atoms in the bulk sample but typically cannot provide an intuitive visualization of the structure. Thus, the combination of atomic-resolution (S)TEM and solid-state NMR spectroscopy has the potential to establish an in-depth, multidimensional structural understanding. Here, we explore this novel strategy to probe the structure of antiferroelectric perovskite oxides PbZrO₃ and (Pb,La)(Zr,Sn,Ti)O₃. We combine complementary information regarding the in-plane displacement vector mapping from STEM with the analysis of local PbO₁₂ environments from ²⁰⁷Pb NMR spectroscopy to provide unprecedented insight into Pb displacements. For PbZrO₃, an ordered 4-fold in-plane displacement modulation is clearly revealed via STEM imaging; meanwhile, the out-of-plane information is provided by two discrete ²⁰⁷Pb NMR signals attributed to two crystallographic Pb sites in the 2D-PASS NMR spectrum. In the chemically modified (Pb,La)(Zr,Sn,Ti)O₃ system, disorder of the structure manifests in not only an inhomogeneous displacement modulation but also a broad distribution of ²⁰⁷Pb chemical shifts, related to significant disorder of displacement magnitudes and a favoring of larger displacements. We show that the displacement distribution depends on whether both in-plane and out-of-plane displacements or only out-of-plane displacements are considered. Our findings demonstrate the advantages in the structural analysis using combined TEM and NMR approaches, hence laying the foundation work for controlling and optimizing functional properties.

Lead zirconate (PbZrO₃, PZ) is a prototype antiferroelectric (AFE) oxide from which state-of-the-art energy storage materials are derived by chemical substitutions. A thorough understanding of the structure-property relationships of PZ-based materials is essential for both performance improvement and the design of more environmentally friendly replacements. (Pb_1−xBa_x)ZrO₃ (PBZ) can serve as a model system for studying the effect of A-site substitution in the perovskite lattice, with barium destabilizing the AFE state. Here, the two-dimensional ²⁰⁷Pb solid-state NMR spectra of PZ and PBZ were recorded to analyze the local structural role of barium substitution. At low substitution levels, ²⁰⁷Pb NMR spectroscopy reveals the presence of Pb-O bond length disorder. Upon crossing the threshold value of x for the macroscopic phase transition into a ferroelectric (FE) state, the barium cations cause local-scale lattice expansions in their vicinity, resulting in the collapse of two lead lattice sites into one. The stabilization of the larger volume site coincides with the favoring of larger lead displacements. We also observed more covalent bonding environments which may originate from the lower polarizability of the barium cations, facilitating the formation of stronger Pb-O bonds in their vicinity. From the local structural point of view, we propose that the substitution-induced AFE → FE phase transition is therefore related to an increasing correlation of larger lead displacements in larger oxygen cavities as the barium content increases. Our results also highlight ²⁰⁷Pb NMR spectroscopy as a valuable method for the characterization of the structure-property relationships of PbZrO₃-based AFE and FE oxides.

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.

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 (e₃₃) ≈ 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.

Na _1/2Bi _1/2TiO ₃-based materials have been earmarked for one of the first large-volume applications of lead-free piezoceramics in high-power ultrasonics. Zn ²⁺-doping is demonstrated as a viable route to enhance the thermal depolarization temperature and electromechanically harden (1-y)Na _1/2Bi _1/2TiO ₃-yBaTiO ₃ (NBT100yBT) with a maximum achievable operating temperature of 150 °C and mechanical quality factor of 627 for 1 mole % Zn ²⁺-doped NBT6BT. Although quenching from sintering temperatures has been recently touted to enhance T _F-R, with quenching the doped compositions featuring an additional increase in T _F-R by 17 °C, it exhibits negligible effect on the electromechanical properties. The effect is rationalized considering the missing influence on conductivity and therefore, negligible changes in the defect chemistry upon quenching. High-resolution diffraction indicates that Zn ²⁺-doped samples favor the tetragonal phase with enhanced lattice distortion, further corroborated by ²³Na Nuclear Magnetic Resonance investigations.

It is well known that disordered relaxor ferroelectrics exhibit local polar correlations. The origin of localized fields that disrupt long-range polar order for different substitution types, however, is unclear. Currently, it is known that substituents of the same valence as Ti⁴⁺ at the B-site of barium titanate lattice produce random disruption of Ti-O-Ti chains that induces relaxor behavior. On the other hand, investigating lattice disruption and relaxor behavior resulting from substituents of different valence at the B-site is more complex due to the simultaneous occurrence of charge imbalances and displacements of the substituent cation. The existence of an effective charge mediated mechanism for relaxor behavior appearing at low (<10%) substituent contents in heterovalent modified barium titanate ceramics is presented in this work. These results will add credits to the current understanding of relaxor behavior in chemically modified ferroelectric materials and also acknowledge the critical role of defects (such as cation vacancies) in lattice disruption, paving the way for chemistry-based materials design in the field of dielectric and energy storage applications.

Understanding about the local structure plays an increasing role for the discovery of structure-property relations in electroceramics. Despite that, characterization techniques dedicated to the local structure are still not widespread in the electroceramics community. Nuclear magnetic resonance spectroscopy (NMR) has the potential to close this gap, as particularly sensitive to minute distortions and well-suited for the structural analysis of partially disordered materials, such as solid-solutions. This review aims at an introduction of this technique tailored to the materials scientist. Following a brief description of the base concepts, its capabilities are demonstrated by a series of tangible examples from local structural questions pertinent to materials based on three classes of lead-free perovskites, namely BaTiO₃, NaNbO₃ and Na_1/2Bi_1/2TiO₃. Beyond its application to lead-free perovskite oxides, the concepts illustrated here are of broad interest for further oxides and materials in general.

The formation of associated defects (e.g.[Al _Ti-V _O]˙) upon acceptor doping is commonly seen as a reason for trapping of mobile vacancies in perovskite ionic conductors and electromechanical hardening in piezoelectric perovskites. In order to clarify the presence of associated defects in Al-doped (Na _1/2,Bi _1/2)TiO ₃(NBT-Al) and Al-substituted ((Na,K) _1/2Bi _1/2)TiO ₃-BiAlO ₃(NKBT-BA), we employ a combination of impedance spectroscopy, ²⁷Al NMR spectroscopy, and electronic structure calculations. Our results indicate that associated defects between and oxygen vacancies can only be found in case of low acceptor doping concentrations. This suggests a decreased driving force for defect association at high doping concentrations as the reason for the non-linear dependence between acceptor concentration and oxygen ionic conductivity for NBT-based ceramics. Furthermore, the combination of experimental and theoretical techniques provides clear evidence for the successive occupation of the B-site, the A-site, and finally the formation of a secondary phase with increasing Al ³⁺content. Altogether, these results call for a new evaluation of the interaction between aliovalent dopants and O ²⁻vacancies in acceptor-doped functional oxides, with implications for the design of ionic conductors as well as ferroelectric materials.

Antiferroelectric materials exhibit a unique electric-field-induced phase transition, which enables their use in energy storage, electrocaloric cooling, and nonvolatile memory applications. However, in many prototype antiferroelectrics this transition is irreversible, which prevents their implementation. In this work, we demonstrate a general approach to promote the reversibility of this phase transition by targeted modification of the material's local structure. A new NaNbO₃-based composition, namely (1− x)NaNbO₃−xSrSnO₃, was designed with a combination of first-principles calculations and experimental characterization. Our theoretical study predicts stabilization of the antiferroelectric state over the ferroelectric state with an energy difference of 1.4 meV/f.u. when 6.25 mol % of SrSnO₃ is incorporated into NaNbO₃. A series of samples was prepared using solid-state reactions, and the structural changes upon SrSnO₃ incorporation were investigated using X-ray diffraction and ²³Na solid-state nuclear magnetic resonance spectroscopy. The results revealed an increase in the unit cell volume and a more disordered, yet less distorted local Na environment, which were related to the stabilization of the antiferroelectric order. The SrSnO₃-modified compositions exhibited well-defined double polarization loops and an eight times higher energy storage density as compared to unmodified NaNbO₃. Our results indicate that this first-principles calculations based approach is of great potential for the design of new antiferroelectric compositions.