Extraordinary physical properties arise at ferroelectric domain walls, where electronic reconstruction phenomena can be driven by bound charges. Great progress has been achieved in the characterization of such domain walls and first tomography techniques have been established, providing unprecedent insight into their 3D structure. Here, we present a non-destructive strategy for tomographic nanoscale imaging of ferroelectric domain walls using secondary electrons. Utilizing conventional scanning electron microscopy (SEM), we show that it is possible to reconstruct the position, orientation, and charge state of hidden domain walls located at distances up to several hundreds of nanometers beneath the surface. A mathematical model links the SEM intensity variations at the surface to the local domain wall properties, enabling non-destructive tomography with good noise tolerance on the timescale of seconds. Our SEM-based approach facilitates high-throughput screening of materials with functional domain walls and domain-wall-based devices. This is crucial for real-time monitoring during the production of device architectures and quality control.

Tetragonal Tungsten Bronze (TTB) systems with morphotropic phase boundaries (MPBs) allow for broader compositional engineering compared to the more extensively studied perovskites with MPBs, and thus provide unexplored opportunities for functional properties. In this study, we investigate the solid solution system Ba₄Na₂Nb₁₀O₃₀ (BNN)-K₄Bi₂Nb₁₀O₃₀ (KBiN). The crystal structures of the ceramics were characterised by powder X-ray diffraction, which indicated the system exhibits a transition from orthorhombic (Ama2) to tetragonal symmetry (P4/mbm) between 30 and 40 % KBiN content, accompanied by converging of the a- and b- lattice parameters. In general, an expansion of the in-plane (a, b) and a contraction of the out-of-plane (c) parameters are observed as the KBiN content is increased. The maxima in permittivity observed for compositions containing 20-35 % KBiN, suggest that ferroelectric phase transitions occur as a function of temperature, while more diffuse dielectric behaviour is exhibited for compositions with 40 % KBiN and higher. Non-linear P-E loops are evident up to 35 % KBiN, and vaguely present for 40 %. The most prominent ferroelectric character, assigned by large remanent polarisation and opening of the strain hysteresis response is exhibited at 35 % KBiN. The structural, electrical and electromechanical data suggests that a ferroelastic-paraelastic phase transition occurs between 30-35 % KBiN and a ferroelectric-paraelectric phase transition between 35 and 50 % KBiN. Thus, we suggest that two distinct phase transitions occur between 30 and 50 % KBiN content, mimicking the temperature dependent structural evolution observed in BNN. This work thus provides new insight into the solid solution of BNN and KBiN and showcases the properties manifested by ferroelastic-ferroelectric and ferroelectric-paraelectric phase transition in close proximity in a TTB system.

Scanning Transmission Electron Microscopy (STEM) is a crucial tool for characterizing Ferroelectrics, offering high spatial resolution for studying strain, defects, and more recently, in situ responses to environmental stimuli. However, the growing capability of STEM corresponds to an exponential growth in the complexity and volume of data. This presentation focuses on leveraging non-linear machine learning techniques to handle the increasing complexity and volume of STEM data. We explore the integration of spatial transformers and regularizers into autoencoders for analyzing both Bright and Darkfield STEM images. Brightfield imaging enables rapid, high-contrast acquisition of extensive sample areas, ideal for in-situ characterization, such as monitoring domain dynamics in various environments. We develop autoencoders with Spatial Transforming layers in the latent space, enhancing awareness of periodic domain patterns and automating their classification, shown with the domain response of Barium Titanate to temperature and background gas. Additionally, L1 Regularization scheduling promotes sparsity, disentanglement, and prevents overfitting. We also investigate the Spatial Transformer’s ability to interpret diffraction patterns in Darkfield imaging, providing higher spatial resolution insights into strain, domain walls, and point defects. A Cycle-Consistent Spatial Transforming Autoencoder model is developed to directly predict the transformation of diffraction patterns and yield higher resolution 2D strain maps than py4DSTEM. In the presence of noise and bias, directly predicting transformations allows the model to outperform traditional methods of finding disk positions through correlation methods or center-of-mass. These spatial transformers demonstrate robustness against noise, artifacts, and measurement bias while efficiently handling large STEM data volumes. Finally, we discuss plans for deploying these models as high-availability inference servers on Kubernetes clusters. Successful deployment onto a public platform opens the door to real-time electron microscopy analysis.

Prototypical antiferroelectric PbZrO₃ has been under scrutiny in the recent years not only for its possible application in energy storage and electrocaloric devices but, most fundamentally, for its ground state. Although PbZrO₃'s ground state has historically and experimentally been described as an orthorhombic 40-atoms cell with Pbam symmetry and '++--' polarization modulation along [110]c direction, some authors have proposed other symmetries. Among them we find an antiferroelectric 80-atoms Pnam, and even a ferrielectric 60-atoms Ima2, theoretical works showed that the energy differences between these phases are lower than 1meV/f.u.. In this work we study through ab-initio and shell-model simulations the occurrence of a 80-atoms Pbam phase with '+--+-++-' polarization modulation along [110]c direction whose energy is comparable with the proposed ground-state(s). Interestingly, Molecular Dynamics simulations at room temperature predict a non-hysteretical P-E loop for this new phase when the field is applied along [001]c direction, this is a desirable feature for energy storage applications.

Hexagonal EuAl₁₂O₁₉ is a quasi-two-dimensional ferromagnet below 1.3 K. Pyroelectric current measurements revealed a weak ferroelectric polarization below Tc = 49 K. The existence of a ferroelectric phase transition is supported by an anomaly in specific heat and thermal expansion. However, the temperature dependence of permittivity does not show a peak at Tc, but only a change of slope. This could argue in favor of an improper or pseudo-proper ferroelectric phase transition. However, single crystal synchrotron diffraction studies revealed no structural change at Tc and second harmonic generation measurements also showed no signal down to 5 K. This indicates that EuAl₁₂O₁₉ remains macroscopically centrosymmetric (space group P63/mmc) down to low temperatures. We propose to explain the observed behavior by frustrated antiferroelectricity or frustrated antipolar correlations below Tc. An external electric field induces a weak polarization visible in the pyrocurrent, but without the field the sample remains centrosymmetric. Dynamical frustration of antipolar order makes it impossible to see the long-range structural change in XRD and explains the observed strong relaxor ferroelectric-like dielectric dispersion below Tc. Similar frustrated antiferroelectricity was theoretically predicted in the isostructural BaFe₁₂O₁₉ below 4 K (Wang and Xiang, Phys. Rev. X 4, 011035 (2014)), but it was not experimentally observed due to the occurrence of quantum paraelectricity. However, the theory from Wang and Xiang predicts that Al cations are much more polar than Fe and this is the reason, why the antipolar correlations begin to build in EuAl₁₂O₁₉ already at 49 K.

Electrocaloric effect (ECE) is a very important and not yet fully described phenomenon occurring in materials with a polar structure. It involves changing the temperature of the tested material under the influence of an applied electric field. The need to conduct research related to ECE results from the need to find alternative cooling sources in the near future. The next-generation devices should hold significant potential for enhanced environmental friendliness and superior energy efficiency compared to current cooling devices. It is assumed that soon this innovative electrocaloric cooling method will render commonly used air conditioners and even heat pumps obsolete. For this reason, materials with high values of electrocaloric temperature change, as well as electrocaloric strength are constantly being sought.
In this work we will focus on the investigative significance of the indirect electrocaloric effect method that allows the determination of entropy change and temperature change with the use of equations derived from the Maxwell relationship.
Our considerations will be based on so far carried studies of the ECE using the indirect method for BaTiO3 ceramics doped with europium, commercial PZT ceramics and Pb5Ge3O11 crystals doped with barium and chromium.

The electrocaloric effect (ECE) refers to the isothermal entropy or adiabatic temperature change of ‎polar dielectrics when an electric field is applied or removed. The ading effect can be defined as the ‎time-dependent change in the functional properties of materials. In this work, we investigated the ‎influence of aging on the ECE in 0.055BaTiO3 – 0.945(Na0.5Bi0.5)TiO3 ceramics prepared by solid-state ‎synthesis in different atmospheres and at different temperatures. Polarization hysteresis loops were ‎measured in the temperature range from -20 °C to 200 °C, and the ECE was indirectly estimated within ‎the framework of a thermodynamic approach based on Maxwell’s relation. Direct measurements of ‎the ECE were performed using a quasi-adiabatic calorimeter. The pyroelectric current was measured ‎on pre-poled samples upon heating from -20 to 200 °C. The concentration of oxygen and bismuth ‎deficiency was studied using Rietveld refinement of X-ray diffraction patterns. The relationship ‎between the aging effect and the sintering conditions was studied. It has been shown that the aged ‎samples have a reduced depolarization temperature and that the maximum electrocaloric effect shifts ‎closer to room temperature.‎

The emergent properties that may arise at interfaces in heterostructures of dissimilar materials are of great interest in the pursuit of novel quantum materials for spintronics applications. An example that has garnered much attention in later years is the proximity coupling of a topological insulator and a magnetically ordered material. We consider thin films of ferromagnetic La₀.₇Sr₀.₃MnO₃ (LSMO) and topologically insulating Bi₂Te₃, both grown by pulsed laser deposition.
In order to evaluate the effect of proximity coupling between these two materials, a full understanding of each of the constituents' properties is necessary. As the signature of the topological nature of Bi₂Te₃ is found in the electronic surface state, we require band structure measurements through angle-resolved photoelectron spectroscopy (ARPES).
However, the surfaces of both Bi₂Te₃ and LSMO degrade when exposed to air, and ARPES is a highly surface sensitive technique. Thus, developing a methodology for surface preparation of both of these samples when re-introduced to vacuum is necessary. We present a study of different surface preparation techniques for both samples. The studied methods include annealing in an oxygen atmosphere for LSMO, along with argon ion sputtering at different energies and duration for both samples. The effect of each method is evaluated by X-ray photoelectron spectroscopy, yielding information on presence of contaminants and stoichiometry, and low energy electron diffraction, yielding information on surface crystallinity. The development of this methodology paves the way for further study into the electronic structures thin films of magnetic oxides and topological insulators.

The advancement of next-generation solid-state cooling devices and energy storage technologies has been facilitated by the strategic chemical modification of lead (Pb)-free barium titanate (BaTiO3) ferroelectric materials, resulting in enhanced characteristics and performance. In this study, Ba0.92Ca0.08Ti0.91Zr0.09O3 (BCZT) and Ba0.92Ca0.08Ti0.91Sn0.09O3 (BCST) lead-free ceramics were synthesized through a high-temperature solid-state reaction method. Structural analyses, utilizing X-ray diffraction (XRD), confirmed the formation of a perovskite structure devoid of impurity phases. Additionally, XRD revealed the well-dispersed presence of Ca2+, Zr4+, and Sn4+ ions within the BaTiO3 lattice. Comprehensive investigations through Rietveld refinement of XRD and Raman spectroscopy affirmed the coexistence of orthorhombic (Amm2) and tetragonal (P4mm) phases at room temperature. In-depth exploration of electrical properties underscored the superior performance of the BCZT compound, exhibiting a remarkable dielectric constant (εr ≈ 13675) and converse piezoelectric coefficient (d33* ≈ 645 pm/V), surpassing the BCST ceramic. Conversely, BCST excelled in energy storage density (Wrec ≈ 192 mJ/cm3) with efficiency (η ≈ 73.26%) and demonstrated enhanced electrocaloric properties with adiabatic temperature change (∆T ≈ 0.980 K) and isothermal entropy change (∆S ≈ 1.1593 JKg-1K-1). These distinctions stemmed from a higher polarization change and a lower coercive electric field in the BCST ceramic. The analytical outcomes provide valuable insights for selecting dopants tailored to specific applications, highlighting the considerable potential of these ceramics in energy harvesting and the development of advanced solid-state cooling devices for future applications.

Over the last 20 years, digital devices such as smart phones, computers, and even smart watches have become more and more prominent in our lives. However, as these technologies become more utilized, the production of these devices puts an increasing strain on the environment. Thus, to keep our use of digital devices sustainable in the future, chip production processes must be analysed, and more sustainable alternatives must be considered.
In order to improve the sustainability of thin film processes, it is important to not only consider sustainable thin film deposition, but also sustainable patterning. Conventional litho-etch processes are unfortunately energy intensive and do not make efficient use of critical resources. Here, a novel patterning approach is shown, inspired by the concept of Selective Area Epitaxy and techniques used in the field of organic chemistry to develop a bottom-up patterning technique that is compatible with solution-based deposition techniques, such as dip coating and Chemical Solution Deposition. This technique uses hydrophobic Self-Assembled Monolayers to alter the properties of a substrate surface before deposition. By patterning the hydrophobic monolayers using UV-lithography, the substrate can be wetted selectively in solution-based thin film deposition, resulting in a patterned film. This study focusses on the deposition of lead-free ferroelectric oxides, using BaTiO₃ as the example material, but the technique is theoretically compatible with any oxide that can be deposited from aqueous solution. This technique not only has the potential to be more sustainable that conventional litho-etch processes but can also reduce the amount of contamination introduced in structures during the patterning process.

Acknowledgement: NTNU Norwegian University of Science and Technology is acknowledged for financial support.

The phenomenon of reentrant behavior was discovered in several materials, such as liquid crystals, superconductors, and magnetic spin glasses. In magnetic spin glasses, it describes a complex order of phase transitions upon cooling, where a coexistence of phases can be found between the Curie temperature and the reentrant spin glass transition temperature. Analogous to magnetic spin glasses, this phenomenon has also been seen in relaxor solid solutions.
In the case of (1-x)Ba(Ti0.85Zr0.15)O3 – xBi(Zn2/3Nb1/3)O3 solid solutions, a second dielectric anomaly was observed at low temperatures, along with the maximum of the dielectric permittivity, for x = 0.015, 0.02, 0.04, and 0.06. It manifests itself as a frequency dependent shoulder and maximum in the temperature dependences of the real and imaginary parts of dielectric permittivity, respectively. This unusual behavior indicates that a reentrant transition into a short-range ordered relaxor phase follows the global transition into a long-rang ordered ferroelectric phase upon cooling. Raman spectroscopy supports the findings of dielectric spectroscopy and shows, that the reentrant relaxor phase becomes more pronounced in the composition with x = 0.06. For x = 0.15, this unique character disappears, and the compounds behave like canonical relaxors.   

This study investigates the functional properties of porous Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics prepared using multi-walled carbon nanotubes (0-70% wt.%) and the burn-out method. The porous ceramics produced, with compositions Ba0.85Ca0.15Ti0.9Zr0.1O3 around the morphotropic phase boundary, present different porosity levels ranging from 3% to 25%. Comprehensive analyses of dielectric, ferroelectric, pyroelectric, piezoelectric, and non-linear properties emphasized the influence of porosity in the BaTiO3-based ceramic materials. The temperature dependence of permittivity indicates that porosity induces a shift in Curie temperature, influencing phase composition and functional properties. Ceramics with porosity exceeding 15% are found desirable, facilitating the removal of residual carbon nanotubes. A study on the poling electric field effect (applied electric field of 5, 7.5, and 10 kV/cm) on piezoelectric properties was discussed. Furthermore, the energy harvesting performance of porous Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics was explored for potential multi-functional tunable applications, and it was observed that even though the maximum voltage value recovered for 25% porosity is lower than those of dense ceramic, it still possesses energy harvesting potential for potential self-powered functionality. Non-linear dielectric characteristics demonstrate the advantages of introducing porosity: the 15-25% porosity range enhances dc-tunability with applied electric fields while reducing permittivity.

Sliding (moiré) ferroelectricity is a new type of ferroelectricity from switchable polarization between layers of bidimensional materials kept together by weak van der Waals forces, and that can therefore slide or tilt with respect to each other. It is studied on bi- or tri-layers with sophisticated techniques at the nanoscopic scale and, thanks to its robustness and low coercive field, it promises great advances In nanoelectronics, especially FeRAMs.
We present measurements of the dynamic Young's modulus of self-standing thick films of Ti3C2Tx MXene, which reveal a phase transition, as a steplike softening and increase of the mechanical losses below 350 K. This type of elastic anomaly is typical of phase transitions, where the square of the order parameter is coupled to strain. It is argued that, in spite of the metallic character of the MXene monolayers, it should be a ferroelectric transition, most likely of the sliding (moiré) type, due to charge transfer between the flakes, that slide with respect to each other. The interlayer nature of the transition is reinforced by the observation that it is suppressed by intercalation of water between the layers. If the transition were confirmed to be sliding ferroelectricity, it would be demonstrated that such a phenomenon can also be studied with simple macroscopic methods, and also in metallic materials, where probing the polarization is impossible with traditional methods.

According to Landau's theory of phase transitions the tricritical point is a point in which a line of first-order transition becomes a line of second-order transition. At the tricritical point, three-phase coexistence terminates in an extended parameter space.
An important fact is that the tricritical point occurs in some materials based on antiferroelectric PbZrO3, For example in the PbZrO3-PbSnO3 system such a situation can be observed. Based on the research of thermodynamic and optical properties it was suggested that in PbZr1-xSnxO3 (PZS) with a composition close to x=25% at of tin, a tricritical point occurs where the change in the nature of the phase transition from the first to the second order is observed. So far, the existence of an II order, i.e. continuous phase transition was not confirmed in the materials with perovskite structure
It should be considered that the addition of Sn ions into antiferroelectric PbZrO3, forming the PZS compound, exhibited several crystallographic phases depending on the x value and temperature. The main effect of this is stabilizing an intermediate incommensurate antiferroelectric phase that is believed to be ‘missed’ in pure PbZrO3. What is interesting for PZS with composition from the tricritical point, near the phase transition between two non-polar phases, we can observe large electrostrictive deformation. Thus, PZS appeared to be an ideal candidate for research in understanding the mechanisms responsible for the phase transitions in antiferroelectric crystals.
Here we present the study of the phase transition behavior for the antiferro-para transitions of PZS single crystals in the vicinity of a tricritical point.

Moiré bilayers have become established playground for realization of various strongly-correlated electronic and topological phenomena, like unconventional superconductivity and Chern insulator phases. Characterizing electrical properties of moiré bilayers at nanoscale can facilitate the understanding of its diverse electronic features. We experimentally demonstrate on graphene/hBN bilayer heterostructure and on twisted bilayer graphene how the correlative and variable-temperature scanning probe microscopy (SPM) can be utilized in performing the whole research process from identifying the region of interest with Kelvin probe force microscopy (KPFM) to revealing its local electrical and electromechanical properties using conducting-tip atomic force microscopy (ct-AFM) and piezoresponse force microscopy (PFM). We have achieved lateral resolution of < 10 nm in these moiré bilayers, which is remarkable for a dry-cryostat environment, and renders cryogenic SPM both suitable and user-friendly for studying moiré bilayers.

The integration of silicon nitride (SiN) caps has propelled the performance of AlScN-GaN HEMTs, yet the imperative quest for an optimized gallium nitride (GaN) cap on AlScN persists. This abstract delves into the compelling motivation for developing an enhanced GaN cap, emphasizing its potential to unlock superior device performance and significantly reduce ohmic contact resistance compared to SiN counterparts. Ongoing morphology optimization through analytical Scanning Transmission Electron Microscopy (STEM) and X-ray Photoelectron Spectroscopy (XPS) provides critical insights. Variations in Metal-Organic Chemical Vapor Deposition (MOCVD) growth conditions are explored to tailor the GaN cap based on the STEM investigations. The origins for island formation are studied by aberration corrected STEM (Nion UltraSTEM / Jeol NEOARM) in combination with energy dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS) to examine the structural and chemical interfacial properties of the all-nitride SiN capped and GaN capped Al0.94Sc0.06N layers with sub-nanometer resolution. AFM and STEM analysis highlighted the difference in growth mechanisms between GaN and SiN on AlScN and how Sc-contaminations in the MOCVD reaction chamber can induce a 3D-growth of GaN, leading to the formation of GaN islands rather than a uniform 2D layer, as typically the case for SiN or for optimized GaN growth.
This dual approach enables a comprehensive understanding of how the choice of cap layer influences the electronic structure and chemical environment at the material interface. Our findings shed light on the advancements achieved in optimizing GaN cap morphology and elucidate the correlation between structural improvements and electrical characteristics. Integrating STEM analyses provides an in-depth view, guiding the refinement of MOCVD growth processes. This research not only contributes to the ongoing optimization of GaN cap morphology but also enhances our understanding of the intricate effect of the cap layers in the AlScN-GaN HEMT architecture.

This study examines the temperature-dependent hydrothermal synthesis of MoS2 nanoflowers at 200°C, 220°C, and 240°C, revealing a significant transition from non-polar bulk material to a polar 2D structure. X-ray diffraction analysis confirms alignment with the hexagonally symmetrical 2H-phase of MoS2 within the P63/mmc space group, with relative peak intensities showing an increase from 200°C to 220°C followed by a decrease at 240°C. FESEM micrographs depict agglomerated, rounded carnation flower-like hierarchical morphology with uniform size and shape distributions. Optical spectra provide quantitative insights into response of MoS2 on adsorbate binding and facilitates the characterization of the adsorption process. Optical characteristics including direct bandgap, Urbach energy, and dispersion parameters (E0 and Ed) were evaluated for each sample. Practical implications of this polar behavior are explored through adsorption properties in Methylene Blue dye removal from wastewater. The sample synthesized at 240°C exhibiting a peak removal efficiency of 97.74% in 20 minutes, attributed to increased surface area (24.43 m2/g) and pore size (0.129 cm3/g). Furthermore, the study systematically investigates the impact of various kinetic parameters—initial dye concentration, catalytic dosage, and contact time—on the dye removal efficiency. This interdisciplinary effort underscores the synergy between optical spectroscopy, material synthesis, and environmental applications, highlighting the potential of MoS2 nanoflowers as efficient adsorbents for water purification. The findings contribute to the fundamental understanding of the optical properties of polar dielectrics and suggest tailored applications in optoelectronics and sensing fields.

On-the-fly machine-learned interatomic potentials have recently opened a new avenue for finite temperature calculations with first-principles accuracy. The potentials are trained using a combination of molecular dynamics (MD), density functional theory (DFT) and machine learning, with the latter deciding when to perform DFT steps and update the potentials. These can easily be trained for complex functional materials and allow for calculations of very large supercells which are not feasible using standard DFT. Furthermore, this may prove especially useful when investigating ferroic materials, particularly ferroic domain walls (DWs) which require large supercell sizes. In this study, we compare results from machine-learned potentials with both experimental data as well as DFT calculations to explore the possibilities of machine-learned potentials for ferroelectric materials.

Here we investigate phase transition and DWs in known ferroelectric LiNbO₃, BiFeO₃ and YMnO₃. We accurately predict phase transitions with parameters matching both ab initio MD simulations and experiments exceptionally well. Furthermore, we use our generated potentials together with nudged elastic bands (NEB) to study DW mobility with and without point defects and compare it to DFT-predicted mobilities. Finally, we discuss the use of machine-learned potentials for investigating ferroelectric materials and the validity of the results.

In improper ferroelectrics, the spontaneous polarization arises as a secondary effect caused by a structural or magnetic instability, promoting the formation of domains and domain walls with unusual physical properties. Gd₂(MoO₄)₃ is a classical example of an improper ferroelectric material, which has been extensively studied with respect to its bulk properties. In contrast, the domain physics and local responses at the nanoscale are much less explored.
Here, we present a comprehensive study of the improper ferroelectric domains in Gd₂(MoO₄)₃, using piezoresponse force microscopy. In addition to the established micrometer-sized polarization domains, we resolve an intriguing pattern of nanodomains with a periodicity of about 70 nm. We show that the nanodomains are stable below 343 K, which is different from the Curie temperature (T꜀ = 432 K), below which the much larger polarization domains are observed. Furthermore, we demonstrate reversible switching of the nanodomains by local electric fields and study their response to mechanical stresses. Our findings provide new insight into the domain physics of the prototypical improper ferroelectric Gd₂(MoO₄)₃ and introduce novel opportunities for property engineering at the nanoscale.

In addition to graphene and graphite, some of the best-known layered materials are the layered thiophosphates with common chemical composition of CuInP2Q6 (Q=S, Se). This class of materials has been studied extensively for a long time. A comprehensive study of polarization swithing in a ferroelectric copper indium thiophosphate CuInP2S6 (CIPS) has been reported both in nanoscale as well as bulk crystals. It was confirmed stable ferroelectric polarization in an intrinsically layered CIP (below ~50 nm thickness). Anomalous polarization switching was found in a ferroelectric CIPS in bulk crystalline. Such anomalous behavior was found to correlate with its ionic conductivity.
The sulfur and selenium compounds have similar structure. Despite this structural similarity, the physical properties are quite different as evidenced by dielectric, ultrasonic, caloric etc. characterization. It was proposed that this anomaly is evidenced for the coexistence of ferrielectric and antiferroelectric ordering. In this report, switching dynamics of CIPS single crystals are presented over wide ranges of temperature and electric field. Ferroelectric switching is usually difficult to experimentally demonstrate in these materials, mostly due to an intrinsic high conductivity and low-temperature ferroelectric behavior. Through comprehensive polarization switching and dielectric spectroscopy studies in both temperature and frequency domains, we reveal that the ionic conductivity influences polarization switching behavior by thermally activated hopping of copper ions in the lattice of CIPS.
The ability of certain materials to convert the electrical energy to heat and vice versa, known as the electrocaloric effect (ECE) was discovered in 1930. This effect originates from the specific coupling between polarisation and temperature. It is known, that strongly polar materials, such as ferroelectrics (FE) and antiferroelectrics (AFE), can be promising ECE candidates, since the larger the polarisation change, the larger ECE will be achieved. Since the electrocaloric effect is tightly related to the polarisation, we have attempted to determine the magnitude of the EC effect in CIPS single crystals and relate these properties with the ionic conductivity.

Multi-layered ceramic capacitor (MLCC) is one of the passive components with a structure in which internal metal electrodes and dielectric ceramic layers are stacked and is used in electronic devices such as mobile phones and electric vehicles. In general, the dielectric properties of MLCC have been analyzed on a macroscopic scale. However, nanoscale studies of dielectric properties are needed to understand underlying mechanisms for improving reliability of MLCC. In particular, while it is widely known that the domain structures affects capacitance of MLCC, it is not clearly understood yet what causes the change in capacitance associated with domain structures in MLCC. In this study, we investigated the change of domain structures associated with capacitance in sub-micrometer scaled areas using piezoresponse force microscopy. We analyzed multi-dimensional domain structures over a couple of micron-meter areas of the BaTiO3 layers in MLCC and revealed the correlation between domain structure and capacitance. These results could provide insight on the improvement of MLCC performance.

Twin walls present in ferroelastic materials introduce a compelling opportunity for the advancement of nanoscale device applications, through the functionalization of a natural interface in a single material. Ferroelastic domain walls exhibit a local breaking of inversion symmetry, along with the suppression of the primary order parameter. This gives rise to phenomena absent in the bulk, such as emergent polarization from the activation of polar instabilities, in an otherwise non-polar material. Orthorhombic CaMnO₃ with space group Pnma, is a non-polar antiferromagnetic material with strong spin-phonon coupling, suggesting that the strain field across the wall can alter the magnetic ordering through structural distortion of antiferrodistortive octahedral rotations. It is thus a promising candidate material for realizing multiferroicity in a single-phase material.

In this work, density functional theory calculations were carried out on ferroelastic domain walls in CaMnO₃ with various patterns of intra-plane and inter-plane magnetic order, to conduct a detailed investigation of the coupling between magnetic properties and the emerging polarization. We find that the distortions introduced at the twin wall lead to an energetically favorable environment for the location of a magnetic wall. Furthermore, the magnitude and configuration of B-site displacements is dependent on the type of magnetic order and the local environment of octahedral distortions, where some magnetic planes are preferred above others. Finally, we discuss the emerging prospects of realizing room-temperature multiferroicity in ferroelastic domain walls.

ErMnO3 is a ferroelectric p-type semiconductor with a combination of insulating, neutral, and conductive domain walls. Through high-resolution scanning transmission electron microscopy (HRSTEM) we can identify and characterise ferroelectric domains, domain walls, and polarisation directions through the shifts of atomic columns. This method relies on the correlation of atomic shifts and displacement of cations and anions to a dipole moment in the unit cell and is a somewhat indirect inference of the polarisation. HRSTEM polarisation mapping requires high spatial resolution, limiting the field of view in a standard 2k x 2k image. To measure the polarisation of the ferroelectric domains in ErMnO3 over larger fields of view and with a more direct method we employ four-dimensional STEM (4D-STEM), where we acquire convergent beam diffraction (CBED) patterns for each pixel of the STEM scan. By observing the change of centre of mass (CoM) in the CBED diffraction spots, the polarisation direction and magnitude can be determined from the nanoscale out to the microscale, bridging a gap between small field of view HRSTEM and large field of view piezoresponse force microscopy previously used to characterise this material. Atomic scale measurements of the CoM tell us about the electrostatic potential within the unit cell and local measurement of the dipoles. At the larger scale, CoM and virtual dark field measurements help us understand the configuration of domains in ErMnO3 and the breaking of Friedel’s Law allow us to visualise non-ferroelastic domains which do not show contrast in other S/TEM imaging techniques. The charges at head-to-head and tail-to-tail domain walls can induce migration of oxygen vacancies and changes in valency observed by electron energy loss spectroscopy (EELS). This work focuses on the application of a variety STEM based characterisation techniques to ferroelectric and non-ferroelastic ErMnO3, and how the complimentary techniques lead to better understanding of the system.

Many of the intriguing characteristics of ferroelectric materials arise from the physical responses at the level of the domains. In conventional ferroelectric systems, such as like Pb(Zr,Ti)O₃, BaTiO₃, and LiNbO₃, polarization reversal between monodomain states takes place through a nucleation and growth process. Different from these systems, hexagonal manganites (MnO𝑅₃, R = Sc, Y, In, and Dy-Lu) host topological meeting points of domain walls that cannot be erased, giving rise to a fundamentally different switching behavior. Here, we explore the switching dynamics of ferroelectric domains in ErMnO₃, using band-excitation piezoresponse force microscopy (BE-PFM). Our measurements reveal a uniform and consistent polarization reversal process, that can be best described by an electric-field-driven domain breathing mode. Importantly, the absence of nucleation and growth in the investigated voltage regime differentiates to the switching process from polarization reversal in conventional systems. Our study provides new insights into the dynamics of the topologically protected domains and expands previous switching studies towards the local scale.

Barium titanate (BaTiO3 or BTO) known as lead-free peroskite-type material with high dielectric permittivity and piezoelectric coefficient, which, being introduced into a polydimethylsiloxane (PDMS) polymer, is extremely promising as a piezoelectric nanogenerator (PNG) for energy-harvesting applications. There are a lot of works devoted to BaTiO3/PDMS-based PNGs and attempts to increase their performance. The latter was tried to be solved in different ways [1], such as by varying the filler concentration, by chemical doping, by using different BTO morphologies, and so on. However, not many works (only one [2] to be precise) were found that focused on the effect of BTO grain size on BTO\PDMS-based PNGs properties, despite the well-known relationship between grain size and piezoelectric coefficient [3]. The specified gap is proposed to be partially filled.
In the current work, by using the simple dispersion method with some pressing-based modifications, a set of BTO\PDMS composites with different grain sizes (300, 500, and 700 nm) and concentrations (23, 30, and 40 vol.%) of BTO will be prepared. The dielectric properties of the prepared materials over a wide frequency and temperature ranges will be demonstrated. Influence of BTO grain size and content on relaxation processes and on ferroelectric-paraelectric phase transition in BTO\PDMS composites will be discussed. The obtained complex data on the dielectric permittivity of the BTO/PDMS composite system could be further beneficial when designing based on them eco-friendly energy-harvesting devices.

Acknowledgements
This research has received funding from the Research Council of Lithuania (LMTLT), agreement No S-PD-22-90.

References
[1] D. Hu et al., Nano Energy, 2019, doi.org/10.1016/j.nanoen.2018.10.053
[2] E. Tsege et al., RSC advances, 2016, doi.org/10.1039/C6RA13482C
[3] T. Hoshina, Journal of the ceramic society of Japan, 2013, doi:10.2109/jcersj2.121.156

Tetragonal tungsten bronzes (TTBs), with the general formula A24A12C4B12B2830, are a family of ferroelectric materials, which, due to their broad compositional space and structural flexibility make them a suitable framework for tuneable lead-free oxide ferroelectrics.

The Ba-containing TTBs such as Ba4Na2Nb10O30 (BNN) with a Tc of ~560oC[1] is of particular interest in high temperature applications where there is a lack of suitable materials. Previous experimental work on substituting the A-site Na cation with larger alkali metals: K and Rb, show a systematic decrease in Tc in addition to uncovering the integral role that cation disorder plays on the structural parameters of these systems.[1]

However, there is little in terms of mechanistic understandings of these compositions using first principles characterisation techniques. In this work, density functional theory (DFT) calculations using both standard and hybrid functionals are performed on BNN-based compositions: Ba4A2Nb10O30 (A = Na, K, Rb ). In particular, we probe the origin of the high Tc as well as the thermodynamics of disorder. In particu

and the trends associated with the compositional engineering, as well as the thermodynamics of disorder and its effect on structural and electronic properties. The effects of this study are discussed in line with experimental work done in parallel as well as implications for the future direction of these materials.

In recent years, the possibility to grow high-quality ultrathin ferroelectric films has revived interest in perovskite ferroelectrics for FeRAM (Ferroelectric RAM) applications, which were once believed to have reached their scaling limits. In these devices, the ferroelectric is sandwiched between two conductive electrodes and the information is stored by polarisation direction in the ferroelectric film. The high remanent polarisation and low coercive field make perovskite materials ideal for low-power FeRAM applications. Ferroelectricity has been observed in ultrathin perovskite films down to 3 nm in epitaxy but has yet to be demonstrated in polycrystalline films, which would be preferred in industry.
In this work, we demonstrate the thickness scaling of polycrystalline BaTiO₃ down to 10 nm with remarkable remanent polarisation values. In the first half of this work, we developed a novel platinum silicide based conductive electrode that also acts as an oxygen migration barrier during the high temperature growth of BaTiO₃. We also studied different stack heterostructures for silicide formation and its impact on the ferroelectric properties of BaTiO₃. In the second half, we used this platinum silicide template/bottom electrode to deposit BaTiO₃ thin films with 10-40 nm film thickness using pulsed laser deposition (PLD). The polarisation electric-field (P-E) measurements revealed enhancements in the ferroelectric characteristics of BaTiO₃, with polarisation values (Pr ~ 10-18 µC/cm²) higher than all literature reported on polycrystalline BaTiO₃ thin films. We also try to understand the influence of the strain imposed by platinum silicide on BaTiO₃ thin films and its impact on the ferroelectric response. Our findings provide new insights into potential for scaling perovskite ferroelectrics and the opportunities for integrating perovskite materials into CMOS technologies

The solid solution (1-x)PZT-xPFN is one of the most promising single-phase multiferroic materials for applications in multifunctional devices. Previous research has mainly focused on the electrical and magnetic properties of ceramic samples, while studies on thin films are scarcer. On the other hand, little is known about the optical and electronic properties of this system. In this work, we synthesized thin films of (1-x)PZT-xPFN using the sol-gel technique to investigate their optical and multiferroic properties. We observed that the incorporation of Fe3+ ions into the PZT matrix not only induces multiferroic behavior with the presence of ferroelectricity and ferromagnetism at room temperature, but also effectively enhances the optical absorption of this material in the visible light region. We also studied the structural and electronic properties of the solid solution with x=0.5 through first-principles calculations. The simulations support the idea that the ferromagnetic behavior is related to the existence of Fe-rich nanoregions. The presence of Fe-3d states at the lower edge of the conduction band explains the redshift of the absorption onset observed experimentally. The reduction of the band gap produced by Fe/Nb co-doping in PZT without modifying the ferroelectric properties of the material makes the solid solution (1-x)PZT-xPFN a promising candidate for photo-multiferroic applications.

The pursuit of new energy solutions aims at enabling a reliable power source for future technologies, in addition to delivering sustainable, cost-effective energy to communities worldwide. One possible option for green energy is harnessing low-amplitude mechanical vibrations as a renewable energy source. Mechanical vibrations, ubiquitous in our surroundings, possess the potential to be converted into electricity, offering a clean energy solution. The energy yield from such vibrations is determined by their amplitude and frequency, which vary across different sources. Vibrations can be categorized into natural phenomena like seismic activity and earthquakes, alongside anthropogenic sources such as transportation, construction sites, mining, carbon capture and storage (CCS) injection, as well as several other examples. This presentation introduces the E-VIBES project, a highly ambitious initiative aimed at exploring the potential of mechanical vibrations as an energy source. In the E-VIBES project we will examine natural and anthropogenic vibration sources through data analysis and literature review and evaluate their potential as energy sources based on magnitude, frequency and occurrence rate. Subsequently, we intend to design and construct an energy harvester utilizing appropriate technologies such as piezoelectric or electromagnetic mechanisms tailored to the selected vibration sources. An important element in the design process will be to find solutions that drive down costs and increase accessibility for as many technologies and communities as possible. The device will undergo real-world testing to assess their efficiency and viability in generating electricity from mechanical vibrations. Finally, a socio-economic analysis will be conducted to evaluate the potential societal impact of the energy harvester. E-VIBES will benefit from an international team with experts in relevant disciplines, including geophysics, material science, theoretical modelling, electronics design, and economics, ensuring a multidisciplinary approach to address the complex challenges involved in the project.

Abstract
Renewable energy sources, including offshore wind, are advancing rapidly, necessitating robust and sustainable electrical power transmission systems. Most challenges associated with cable terminations and joints in these systems arise from the solid-solid interfaces within these cable accessories. These crucial components, installed manually on site, have their integrity significantly dependent on the selection of components and the quality of craftsmanship.
Silicone rubber (SiR) has been largely used as electrical insulation material for cable accessories. Slip-on terminations and joints utilize the hyper-elastic properties of SiR to achieve a desirable radial pressure to create a firm interface between the cable core insulation and the accessory and provide the needed electrical insulation functionality. SiR utilized in high voltage (HV) cable insulations can be molded into different shapes and sizes, with hardness dependent on processes and additives used. While in operation, it is likely that dynamic mechanical stresses influence the performance of SiR material and most importantly at interfaces.
Depending on the environment of installation, SiR is likely to undergo mechanically induced aging arising from dynamic expansion and contraction from variations in the power (current loading) transported by the cable. This is likely to induce or promote formation of cavities, or cracks at interfaces which under significant electrical stress may succumb to partial discharges resulting into deterioration of the insulating property and thus electrical breakdown. Here, we investigate the effect of dynamic mechanical aging on the stress relaxation response of SiR with focus on the interface and lubricant used. Different grades of SiR were subjected to accelerated mechanical aging. AFM, SEM with EDS, 3D optical profilometer, FTIR were used to examine SiR before and after dynamic mechanical aging. The effect of dynamic mechanical aging on SiR interface properties has been presented and discussed.
Acknowledgement
This work is funded by the project “High voltage subsea connections for resilient renewable offshore grids” (SeaConnect), supported by the Research Council of Norway (Project no. 336512) and the following partners: Benestad Solutions AS, LowEmission Centre, NKT GmbH, NTNU, Systèmes et Connectique du Mans (SCM), University of Strathclyde.

To probe the emerging magnetic spin at the antiferromagnetic LaFeO3 layer due to interfacial effect, with element specificity in (111)-La0.7Sr0.3MnO3/LaFeO3 epitaxial multilayers, we utilise resonant soft X-ray reflectivity (RSXR) technique with axial sensitivity. This emerging magnetism and magnetic anisotropy control at the ferromagnet (FM) /antiferromagnet (AF) interface in perovskite transition metal oxides of interest for energy efficient spintronics applications. However, studies of antiferromagnetic interactions at depth are often limited by direct measurements. In this work, we presents linearly polarised RSXR to probe the spin structure at the AF layers of an oxide multilayer with progressive change in strain condition.

(111) pc-La0.7Sr0.3 MnO3/LaFeO3 (LSMO/LFO) multilayers were epitaxially grown on (101) DyScO3 by pulsed laser deposition as our model system in which the antiferromagnetic states at LaFeO3 layers are of interest. REED revealed layer by layered growth, and a progressive change in strain state was seen by reciprocal space map. RSXR data were collected at Advanced Light Source beamline 4.0.2 using linear polarized soft x-ray, with applied magnetic field along LSMO easy and hard axis. Data analysis was carried out with RemagX using magnetic matrix formalism.

Based on unpublished RSXR data on LSMO/LFO/DSO(101)o, fully strained bilayered thin film has a small change in dichroism signal while aligning magnetic field directions to the easy and hard axis of LSMO. Fitted model suggests an interface coupling leads to ferromagnetism in the LFO layer. This model is solely interpreted on fully strained heterostructure with limited asymmetry signal and is restricting the possibility for further elaboration. Hence, a multilayered thin film of LSMO/LFO/DSO(101)o with progressive change in strain state was investigated. From aquired data, we observed significant increase in dichroism features and contrast, in turn provides an more elaborated model on antiferromagnetic spin behaviour that to be presented. In this work, we demonstrated that linearly polarised RSXR presents a unique means of resolving AFM spins at buried interfaces in multistructures which is to be utilised for materials engineering towards spintronic applications.

The powder aerosol deposition (AD) method is promising for depositing thick, dense ceramic films at room temperature. However, AD films exhibit deposition-induced defects such as a nanocrystalline microstructure, internal stress, and oxygen vacancies. Especially the microstructure and, therefore, the grain size has a limiting effect on the functional properties of the as-deposited films, which is shown by grain size-dependent electromechanical measurements and in situ electric field-dependent synchrotron X-ray diffraction. Early results also display the impact of film thickness on the oxygen vacancy recombination by coefficient of thermal expansion measurements. This work aims to improve these properties for lead-free ceramic materials through a combination of different processing approaches such as laser annealing and electric current-assisted annealing. Further, initial results for different processing methods are discussed.

The lead-based perovskite oxides have attracted considerable scientific interest due to their ferroelectric, antiferroelectric, and relaxor properties. Like the other lead-based materials, such as PbTiO3 (PT), PbMg1/3Nb2/3O3 (PMN), PbZn1/3Nb2/3O3 (PZN), which are a soft-mode (displacive) ferroelectrics, PbHf0.92Sn0.08O3 (PHS) exhibit phonon spectra near the center of Brillouin zone that is dominated by a soft transverse optic (TO) mode that reaches a minimum frequency on cooling and then hardens at lower temperatures. Concurrent with the decrease in frequency, the frequency range of this mode broadens in energy until it becomes heavily damped, but only for wave vectors near the zone center.

PbHfO3, a well-known antiferroelectric material, undergoes a first-order structural phase transition from a high-temperature paraelectric phase (PE) to a low-temperature antiferroelectric phase (A). Doping with different elements, such as tin (Sn), has shown promise in modifying the electrical properties and inducing the appearance of new intermediate phases (IM).
The structure of this new intermediate phase can be represented by a superposition of two or multiple polarized sublattices. This superlattice can be treated as an incommensurate phase with a double lattice parameter of the reciprocal lattice.

However, it is worth noting that previous studies have primarily focused on lower frequency ranges, and there remains a need to explore the behavior of materials at higher frequencies with greater detail. In that case, we must deal with a huge gap in dielectric permittivity from 10 GHz to 200 GHz and to trace the whole spectrum we need to have a microwave measurement, which is a challenge, especially in high dielectric permittivity materials.

In this study, we present a comprehensive investigation of the electrical properties of PbHf0.92Sn0.08O3 using dielectric spectroscopy. This work aims to characterize mode softening during the phase transition in the microwave frequency range.