Complex lead-based perovskites with the general formula Pb(Bx’B1-x’’)O3, represent an important class of antiferroelectrics beyond the prototypical PbZrO3 and NaNbO3. Depending on the combination of B-site species and the degree of cationic ordering, these materials exhibit a wide range of ferroic behaviors, spanning from antiferroelectric to (relaxor) ferroelectric responses. In this study, we investigate (Pb1-xBax)(Yb1/2Nb1/2)O3 polycrystals synthesized via a two-step processing route. Despite displaying antiferroelectric, ferroelectric, or nearly linear dielectric behavior at room temperature, all compositions exhibit double polarization hysteresis loops in proximity to a lower-temperature dielectric anomaly. This dielectric anomaly originates from the competition between antipolar and nanoscale polar regions, and shifts towards lower temperature with increasing Ba content, reflecting the suppression of long-range antiferroelectric ordering. Notably, a composition-invariant temperature scale, T*, is identified and associated with the onset of static correlations among nanoscale polar entities, consistent with behavior reported in other complex Pb-based relaxor ferroelectrics. Superlattice reflections arising from antiparallel Pb2+ displacements persist above T*, suggesting an intricate cation-ordering landscape requiring further investigation. These findings underscore the coexistence and competition of polar and antipolar instabilities in complex lead-based perovskites, and their pronounced sensitivity to chemical substitution, thermal fluctuations, and external electric fields.

We report the discovery of a geometric pathway for tuning ferroelectric properties through a thermally driven reconfiguration between coexisting polar states in Li-substituted NaNbO_{3}. Using a first-principles density functional theory calculation and ^{7}Li solid-state nuclear magnetic resonance spectroscopy measurement, we reveal that Li substitution creates two distinct polar configurations whose transformation under annealing enhances the Curie temperature and induces piezoelectric hardening. Our findings establish a geometrically driven polar state reconfiguration mechanism, providing a general design principle for ferroics whereby macroscopic functional properties can be engineered via lattice geometry.

Enhancing dielectric energy-storage density (Ue) requires maximizing the difference between maximum and remanent polarizations (ΔP). Improving ΔP remains fundamentally challenging, as existing strategies rarely achieve simultaneous high maximum polarization and low remanent polarization. We introduce a postsynthesis treatment method, cryogenic thermal cycling, in which liquid nitrogen infiltrates the film and then is rapidly cycled to 100°C. This process markedly increases ΔP to 105 microcoulombs per square centimeter in oxide ferroelectric titanate films through oxygen vacancy-mediated nitrogen hybridization. Using this approach, we increased Ue to 261 joules per cubic centimeter with an efficiency approaching 80%. This approach is broadly applicable to diverse film materials with thicknesses spanning the nano- to microscale, offering a facile and cost-effective route to overcoming the critical bottleneck in ΔP and Ue.

Active symmetry control - a central challenge in materials science, particularly in ferroelectrics - is achieved via mechanically assisted poling (MAP) guided by thermodynamics and phase - field modeling. This approach yields extraordinary piezoelectric coefficients (about 5,000 pC/N at 24 degC; 11,700 pC/N at 58 degC) together with about 65% optical transmittance in a classic relaxor ferroelectric, Pb(Mg1/3Nb2/3)O3-PbTiO3. Mechanical suppression of undesirable phases stabilizes a reconstructed symmetry with highly ordered domains, verified by multiple characterization techniques. The strategy is validated across several distinct ferroelectric systems. To demonstrate its practical utility, we fabricate a transparent dual-modal wearable sensor integrating continuous blood pressure monitoring via piezoelectricity with photoplethysmographic SpO2 detection, enabling high-fidelity physiological tracking. This work establishes mechanically assisted symmetry reconstruction as a pathway to multifunctional optoelectronic materials and compact wearable health technologies.

Surface-initiated polymerizations generate thin films ("brushes") consisting of polymer chains that are anchored with one chain end to a solid surface. As they are conducted from initiator-modified solid substrates, these polymerizations allow for unidirectional chain growth and enforce a stretched chain conformation. Using acrylonitrile as an example of a monomer with a dipolar side-chain functional group, this study finds that surface-initiated polymerization not only impacts the alignment and conformation of the polymer main chain but can also influence the orientation of side-chain functional groups. Surface-initiated polymerization of acrylonitrile is found to result in polyacrylonitrile (PAN) brushes that display spontaneous pyro- and piezoelectric behavior. As these properties are not observed in spin-cast PAN films, this indicates that surface-initiated growth of PAN enforces an overall parallel orientation of the dipolar nitrile side-chain functional groups. This is supported by polarized FTIR spectroscopy and NEXAFS experiments, which suggest an overall nonisotropic orientation of nitrile groups in the PAN brush, whereas the nitrile groups in the spin-cast PAN film are more isotropically oriented. Pyro- and piezoelectric polymers are attractive for use in sensors, actuators, and energy-harvesting devices but typically require electrical poling, mechanical stretching, or electrospinning to promote the alignment of molecular dipoles and enhance piezo- and pyroelectric properties. The ability to prepare thin polymer films that display spontaneous pyro- and piezoelectric behavior is significant as it renders these postprocessing steps unnecessary.

Hopping of oxygen vacancies under an alternating field generates a large and robust electrostrain in lead-free piezoelectrics.

Ferroelectric materials have been widely used in various electromechanical devices, from ultrasonic transducers and actuators to mechanical energy harvesters. The key performance metrics of these devices, such as sensitivity, efficiency, and bandwidth of ultrasonic transducers, are largely determined by the piezoelectric properties. This Review highlights recent research progress in improving the piezoelectricity of ferroelectric materials and offers potential strategies for further enhancement to meet the ever-increasing demands for high-performance piezoelectric devices and systems. It provides insights into the future development of ferroelectrics to address the increasing demands of emerging applications, including photoacoustic imaging and piezoelectric fans and motors in integrated circuit-enabled electronic devices. Additionally, it emphasizes the need to consider environmental impacts across the entire life cycle of ferroelectrics, from sourcing and manufacturing to usage and disposal.

Introducing symmetry breaking in materials enables the emergence of functionalities. This can be microscopically and macroscopically driven by applying external stimuli such as mechanical stress, electric field, temperature, and chemical modification. For instance, non-zero net dipole moments are formed in a material with the presence of local charged defects or their clusters, which can alter the crystal structure, charge states, and electrostatic potential across the material. Here, a conceptual approach is demonstrated to defects-mediated symmetry breaking that allows for built-in polarization in a nominally centrosymmetric defective oxide, GdxCe1-xO2-δ (CGO) films by creating a macroscopic charge asymmetry. These results show that switchable and enduring polarization in CGO films is governed by the electric field-driven redistribution of oxygen vacancies with a critical field strength of ≈0.5 MV cm-1 at room temperature. This leads to notable and persistent pyroelectric effect with a coefficient of ≈180 µC m-2 K-1. These findings highlight the potential to develop high-performance, sustainable, environmentally friendly polar film materials by manipulating ionic defects from their centrosymmetric ground states. This approach provides new opportunities to expand the range of polar materials in current and future energy and electronic applications.

BiFeO3 is a ferroelectric with a Curie temperature of 830 C-degrees, however, its piezoelectric performance at high temperature remains unclear. The current work reveals a disappearance/recovery of piezoelectricity in BiFeO3 at elevated temperature and upon cooling. In particular, that temperature is strongly frequency-dependent and ranges from 280 to 430 C-degrees between 0.5 and 140 Hz, respectively. Meanwhile, in situ and ex situ X-ray diffraction and piezoresponse microscope analysis demonstrate thermally-resistant domain texture to temperatures as high as 750 C-degrees. This demonstrates that the piezoelectricity of BiFeO3 is strongly influenced by its resistance/conductance variations due to charge carrier motion limiting the operational frequency. The investigation enhances the understanding of BiFeO3 complex piezoelectric behavior at various temperatures, offering insights into its potential applications.

PbTiO3-based ferroelectric solid-solution ceramics have been widely used for electromechanical devices. However, it is still challenging to separate and control the contributions to the electromechanical functionalities, mainly as a function of temperature, where thermal anomalies and phase transitions can be observed. This study investigates the ultrasonic velocity and attenuation and the dielectric, ferroelectric and structural features of Pb0.55Ca0.45TiO3 ceramics from low temperatures (10 or 115 K) up to room temperature as an example of A-site isovalent substitution in PbTiO3. Such a combination of information makes possible the phenomenological deconvolution of the effects of ferroelectric domain wall pinning and structural features on spontaneous electric polarization. The room-temperature symmetry was determined as Pna2(1). The results show that this model refined by the Rietveld method for synchrotron X-ray diffraction patterns from 115 K to room temperature can explain the polarization extension features of these materials during heating. This study shows a correlation between structural thermal anomalies and low-temperature electric polarization in PbTiO3-based ferroelectric ceramics.

Piezoelectric materials produce a linear deformation in response to an applied electric field and are essential for precision-control devices. The conventional view is that polymers must be crystalline and possess remanent polarization after artificial poling to gain piezoelectricity. For the ferroelectric polymer poly(vinylidene difluoride), the required poling field is exceptionally high, up to 150-200 kV mm-1. Here, we circumvent this limitation by utilizing the elastic displacement of electric dipoles and creating a net polarization. We find that a subcoercive field of 49 kV mm-1 can induce a high piezoelectric coefficient, d33, of -33 pm V-1 in an unpoled poly(vinylidene fluoride-trifluoroethylene) film. In this case, the dielectric acts as a piezoelectric, as long as a bias electric field is applied, with its piezoelectric coefficient increasing proportionally to the strength of the electric field until polarization saturation sets in. The proposed methodology is further extended to amorphous polymers, providing an opportunity to discover alternative piezoelectrics within the dielectric family.

Piezo- and pyroelectric materials are of interest, for example, for energy harvesting applications, for the development of tactile sensors, as well as neuromorphic computing. This study reports the observation of pyro- and piezoelectricity in thin surface-attached polymer brushes containing zwitterionic and electrolytic side groups that are prepared via surface-initiated polymerization. The pyro- and piezoelectric properties of the surface-grafted polyelectrolyte brushes are found to sensitively depend on and can be tuned by variation of the counterion. The observed piezo- and pyroelectric properties reflect the structural complexity of polymer brushes, and are attributed to a complex interplay of the non-uniform segment density within these films, together with a non-uniform distribution of counterions and specific ion effects. The fabrication of thin pyroelectric films by surface-initiated polymerization is an important addition to the existing strategies toward such materials. Surface-initiated polymerization, in particular, allows for facile grafting of polar thin polymer films from a wide range of substrates via a straightforward two-step protocol that obviates the need for multistep laborious synthetic procedures or thin film deposition protocols. The ability to produce polymer brushes with piezo- and pyroelectric properties opens up new avenues of application of these materials, for example, in energy harvesting or biosensing.

Matthew Rampley, Markian Prokopovych, and Nóra Veszprémi. The Museum Age in Austria-Hungary: Art and Empire in the Long Nineteenth Century University Park, PA: Pennsylvania State University Press, 2020. Pp. 300. - Volume 54

The railway station complex in Karlovac represents a valuable segment of the industrial and transport heritage of Croatia from the second half of the 19th century and the beginning of the 20th. In addition to the station building itself, it also consists of a whole series of various utilitarian, industrial, warehousing, residential and office buildings. These have lost their original functions, partly due to the deindustrialization of Karlovac and to changes that have occurred in the way trains are run and maintained. The construction of the oldest railway infrastructure in Croatia and Karlovac is linked to the political position of the Triune Kingdom of Croatia, Slavonia and Dalmatia in the second half of the 19th century and the beginning of the 20th within the Habsburg Monarchy and, after 1867/1868, the Austro-Hungarian Empire. Before the Austro-Hungarian Compromise of 1867, the construction of railways was a reflection of the interests of the economic and political elite of Vienna, the capital of the Monarchy. The first railways in Croatia were built by the Imperial Royal Privileged Austrian Southern Railway Company (Die k.k. privilegierte Sudbahn-Gesellschaft). After connecting Zagreb by rail with the rest of the Monarchy via Zidani Most and Ljubljana in 1862, it built a railway to Karlovac that opened on 1 June 1865. The buildings of the Southern Railway Company in Karlovac were built immediately after the construction of the Karlovac-Zagreb railway line. These were mostly temporary wooden structures that no longer exist. They were designed by Wilhelm von Flattich, the chief designer of the Southern Railway Company. After the Croatian-Hungarian settlement in 1868, the construction of the railway infrastructure in Croatia was mostly controlled and led by the state-owned Budapest company Royal Hungarian State Railways (Magyar Allamvasutak, abbreviated MAV). In 1873, it completed the railway line between Budapest, the capital of Hungary, and Rijeka, the largest export port of the same country, via Zagreb and Karlovac. The Hungarian railway infrastructure on that route, as well as in the rest of western Croatia, was managed by the Transport Administration of the Royal Hungarian State Railways in Zagreb. The construction of the Rijeka railway was not initially followed by the construction of the rest of the modern railway infrastructure in Croatia. In Karlovac, the old station of the Southern Railway Company was used for almost four decades (from 1865 to 1900). The situation was no better in other parts of Croatia until the 1890s when Budapest started investing in construction projects on the territory of Croatia. The construction of the Zagreb Glavni Kolodvor building (1890-1892) can be seen as the beginning of the investment cycle. The station in Karlovac would be built almost a full decade later. The designer of the new building of the Karlovac railway station was the Hungarian architect, Ferenc Pfaff, one of the main architects of MAV, who, among others, was entrusted with the design of the stations in Debrecen (1894), Timisoara (1898-1899), Pecs (18981899) and Szeged (1902), and, within Croatia, stations in Zagreb (1890-1892), Rijeka (1892), Osijek (18981899) and finally Karlovac ( 1900-1903). The station in Karlovac, although more modest than those in Zagreb and Rijeka in terms of size and facade, far surpasses most of the other stations built by the Hungarian State Railways in Croatia. This is primarily the result of the fact that it was built on the most important traffic route in Hungary at the time. Simplified Neo-Renaissance, the style chosen for the facade, dominated public architecture of (central) Europe at the time, and especially the architecture of the Royal Hungarian Railways. At the time, most of the stations were built in the neo-Renaissance style. The decision to choose facade brick as the basic material for the facade is probably Pfaff 's reaction to events in Hungarian architecture of the period when this material began to be used more and more frequently for the design of facades on both historicist and Art Nouveau buildings. The white, plastered horizontal lines, profiled cornice and corner 'stones' of the window openings contribute to the special elegance of the station's facade. The facade of the Karlovac station is not unique in Pfaff's work. Although he often plastered the facades of his station buildings and covered them with rich stucco decoration, as can be seen on the Rijeka and Zagreb railway stations, numerous other Pfaff station buildings, for example in Miskolc, Cegled, Jimbolia, Vrsac and elsewhere, very closely resemble the Karlovac station both because of the use of facade brick and because of the specific spatial and stylistic solution. The station in Karlovac is almost identical to the station in Leopoldov (Hungarian Lipotvar, now in Slovakia), designed in 1908. The central part of the Leopoldov station is identical to the central part of the Karlovac station. The only difference in the basic spatial organization and design of the facade occurs at either end. Of the stations in Croatia, it is the most similar to Osijek due to the use of facade bricks.

Humankind and, in general, all life on earth, face a fundamental sustainability crisis. We have realized many decades ago that both our sources and our sinks on our planet are limited. International treaties have been adopted, panels have been formed and assessments have been published. Yet, almost all nations regularly fail to comply with their goals. Many potential barriers to swift actions exist, and sustainability in its many facets reveals complex interdependencies and rebounds. Humankind relies on an infrastructure in terms of energy supply, housing, and others, which take decades to change. At the same time, we face tipping points, which describe an irreversible acceleration of degradation of our fundamental life’s resources. This concerns not only the climate crisis, which is visible in so many nations with floods and heat waves and a surge of new temperature extremes and costs due to mitigation and adaptation. No, the problem also lies in a set of planetary limits, including a terrifying loss of agricultural soil, an increasing level of acidity in the oceans, enhanced nitridation, and loss of biodiversity and natural habitats. In this situation, it appears obvious, that scientists, meaning all scientists beyond our representatives in international panels, need to respond. We need to inform ourselves across the disciplines and disseminate available information into society. We need to spell out that a transformation of society is required combining technological advances and a change in lifestyle with a reduction in demand for our planet’s sources and sinks.

We report an intrinsic strain engineering, akin to thin filmlike approaches, via irreversible high-temperature plastic deformation of a tetragonal ferroelectric single-crystal BaTiO_{3}. Dislocations well-aligned along the [001] axis and associated strain fields in plane defined by the [110]/[1[over ¯]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.

Članak govori o izgradnji i stilskom rješenju zgrada kompleksa željezničkog kolodvora u Karlovcu. Prvi (provizorni) kolodvor u Karlovcu sagrađen je oko 1865. i podiglo ga je bečko Društvo južnih željeznica, vjerojatno prema projektu arhitekta Wilhelma Flattticha. Nakon 1880. godine pruga s kolodvorom u vlasništvu je Ugarskih kraljevskih državnih željeznica koje su podigle cijeli niz zgrada karlovačkoga kolodvorskog kompleksa. Središnja prijemna kolodvorska zgrada, najmonumentalnija građevina kompleksa, podignuta je 1900. – 1903. godine prema projektu mađarskog arhitekta Ferenca Pfaffa, u neorenesansnom stilu. Riječ je o jednoj od najmonumentalnijih kolodvorskih zgrada podignutih u tom razdoblju u Hrvatskoj.