The (1 - x)(Bi0.5Na0.5)TiO3-xBaTiO(3) (BNT-BT) system has attracted a great deal of interest because it presents a morphotropic phase boundary (MPB) between the rhombohedral and tetragonal phases for 0.05 < x < 0.08. Identifying the MPB in the BNT-BT system often results in materials exhibiting a high-symmetry (pseudo)cubic x-ray diffraction pattern. However, this singular composition exhibits ferroelectricity, which has been explained as a consequence of a field-induce phase transformation. Here, we demonstrate that the stress release after poling, from the virgin state of the sample, is a crucial phenomenon to obtain piezoelectric response in MPB BNT-BT. The mechanism behind the unusual poling-depoling process in piezoceramics exhibiting high-symmetry MPB is elucidated by combining x-ray diffraction measurements and advanced Raman spectroscopy. This underscores the importance of post-poling stress release from the virgin state as a critical factor in attaining piezoelectric response in lead-free piezoceramics with high-symmetry MPB configurations.

Barium strontium titanate is a well-known perovskite-structured ferroelectric system that has recently gained attention for its energy storage capabilities. Here, fine-grained BaTiO3-SrTiO3 ceramics are obtained by reactive flash sintering of mixed BaTiO3 and SrTiO3 powders, a one-step sintering process that significantly reduces the energy consumption involved. The current control mode is employed here to manage the reactive flash sintering event for a striking refinement of the microstructure. The effect of microstructure on the dielectric, ferroelectric, and energy storage properties of flash-sintered ceramics is discussed through the analysis of impedance spectroscopy data. The quality and electrical homogeneity of the obtained materials are shown to be key factors in optimizing the energy storage properties of dielectric materials. This work highlights the potential of current-controlled flash sintering as a powerful tool for microstructural engineering in dielectric materials, offering new pathways for the development of energy-efficient energy storage systems.

In August 2023, I received a very interesting sample in the laboratory, which after petrographic analysis turned out to be a brachinite-type meteorite. These meteorites are an achondritic type, composed mainly of olivine, and extremely rare itself. It is the first sample of this type that we have identified in our laboratory, which has allowed us to characterize this type of meteorite using polarized light petrographic techniques. After the first analyses, the official classification was carried out, concluding with the inscription of the meteorite ASH SHAQQAH 001.

Optical means instead of electric fields may offer a new pathway for low-power and wireless control of magnetism, holding great potential to design next-generation memory and spintronic devices. Artificial multiferroic materials have shown remarkable suitability as platforms towards the optical control of magnetic properties. However, the practical use of magnetic modulation should be both stable and reversible and, particularly, it should occur at room temperature. Here we show an unprecedented reversible modulation of magnetism using low-intensity visible-light in Fe75Al25/BaTiO3 heterostructures, at room temperature. This is enabled by the existence of highly oriented charged domain walls arranged in arrays of alternating in-plane and out-of-plane ferroelectric domains with stripe morphology. Light actuation yields a net anisotropic stress caused by ferroelectric domain switching, which leads to a 90-degree reorientation of the magnetic easy axis. Significant changes in the coercivity and squareness ratio of the hysteresis loops can be light-modulated, encouraging the development of novel low energy-consumption wireless magneto-optical devices.

Low-consumption ceramics processing routes are expected to replace conventional ones due to environmental concerns. In this context, flash sintering is garnering interest because it allows dense ceramics to be obtained in just a few minutes and at relatively low temperatures. This is particularly interesting for sintering alkaline-based compounds due to the easy volatilization of these elements. In this work, current-controlled flash sintering is used to obtain potassium-sodium niobate (KNN)-based piezoceramics with refined microstructure and suitable stoichiometry, leading to improved functional properties. KNN-based materials are currently outstanding lead-free piezoceramics, with their properties highly sensitive to the proper construction of the polymorphic phase boundary, as in the case of the first promising composition (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3. Results of this work show that sintering parameters may determine the polymorphic behavior of this system, thereby evincing flash sintering allows polymorphic phase boundary to be fine-tuned. It is demonstrated that the convergence of microstructure refinement and compositional control holds the potential for enhancing properties through a proper electric current control during flash sintering.

Controlling the elastic properties of materials is an issue that has been widely investigated because adapting available materials for incoming applications is required. Many efforts have been made in the last decade to make the elastic properties of ferroelectric materials adjustable for their use in high-technology products or processes. Additionally, in this new era of real-time wireless control, wireless devices are expected to replace traditional wired ones. However, there is no published research on visible-light wireless control of the elastic properties of ferroelectric materials. Here, we present the absolute proof the elasticity in polycrystalline BaTiO3 can be reversibly switched and linearly tuned with visible light. Thermal effects are definitively isolated so that the photo-induced phenomenon is unequivocally revealed. The light-induced change of Young’s modulus is originated by the increased screening of the charged domain walls under illumination. These results provide a promising avenue to the development of a new generation of optically driven devices based on elastically photosensitive ferroelectric materials.

The concept of multiphysics, where materials respond to diverse external stimuli, such as magnetic fields, electric fields, light irradiation, stress, heat, and chemical reactions, plays a fundamental role in the development of innovative devices. Nanomanufacturing, especially in low-dimensional systems, enhances the synergistic interactions taking place on the nanoscale. Light-matter interaction, rather than electric fields, holds great promise for achieving low-power, wireless control over magnetism, solving two major technological problems: the feasibility of electrical contacts at smaller scales and the undesired heating of the devices. Here, we shed light on the remarkable reversible modulation of magnetism using visible light in epitaxial Fe3O4/BaTiO3 heterostructure. This achievement is underpinned by the convergence of two distinct mechanisms. First, the magnetoelastic effect, triggered by ferroelectric domain switching, induces a proportional change in coercivity and remanence upon laser illumination. Second, light-matter interaction induces charged ferroelectric domain walls' electrostatic decompensations, acting intimately on the magnetization of the epitaxial Fe3O4 film by magnetoelectric coupling. Crucially, our experimental results vividly illustrate the capability to manipulate magnetic properties using visible light. This concomitant mechanism provides a promising avenue for low-intensity visible-light manipulation of magnetism, offering potential applications in multiferroic devices.

Abstract Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) stands out among lead‐free ferroelectric oxides under consideration to replace state‐of‐the‐art high‐sensitivity piezoelectric Pb(Zr,Ti)O3, for a range of energy conversion ceramic technologies. However, the best performances have been reported for very coarse‐grained materials, and attempts to refine microstructure below 10 µm grain size consistently result in significant property degradation. Here a comprehensive study of the grain size effects on the properties of BCZT across the micron scale is reported, down to the verge of the submicron one. Results show a distinctive early evolution of properties for grain sizes between 1 and 5 µm. For the larger sizes in this range, an opposite effect is found for the piezoelectric charge coefficient and electric field‐induced strain with respect to the very coarse‐grained material, while very good overall performance is maintained. For the lower sizes, relaxor features appear, yet materials can still be poled indicating their ferroelectric nature. This strongly resembles size effects in the Pb(Mg1/3Nb2/3)O3‐PbTiO3 system, driven by the slowing down of the relaxor to ferroelectric transition with size reduction, though kinetics seem to slow down across much larger grain sizes for BCZT. Concomitant changes in the polymorphic phase coexistence are described and discussed by synchrotron X‐ray diffraction.

The demand to produce clean energy has been increasing over the last years due to the various climate changes, which are strongly afflicting the world. Therefore, it is necessary to implement new and alternative energy sources that contribute for the environment preservation. That is the case, for instance, of novel energy-storage devices, which could contribute for the current demand of clean energies. In fact, most of the system used nowadays are those lead-based materials, which are strongly pollutant and contribute for the environment contamination. In this way, the interest in the development and study of lead-free materials has become a real priority in the scientific community. The objective of the present work is to synthesize and investigate the physical properties of lead-free ferroelectric systems based on BaTiO3 (BT) with technological interest. In particular, the structural and dielectric properties have been investigated as a function of the Sn4+ content, used as a doping element in the BT hosting crystalline structure. The phase transition characteristics have been also analyzed in a wide temperature and frequency range.

La problemática ambiental en la que nos encontramos actualmente está causada por diversos problemas como el cambio climático, el agotamiento de los recursos naturales y la acumulación de desechos, destacándose la alimentación actual como uno de los elementos con mayor impacto en el medio ambiente. De ahí que la “alimentación sostenible” sea una temática de especial interés. Para enseñar sobre alimentación sostenible, un recurso especialmente relevante son los huertos escolares, y dentro de ellos, los huertos ecológicos que se desarrollan en permacultura. Este audiovisual pretende dar visibilidad a este tipo de huertos como alternativa sostenible a la crisis socioambiental existente, ya que visibiliza el metabolismo social circular. La alimentación es una de las actividades humanas que más impacto socioambiental tiene y debemos ser conscientes de ello. Por esta razón, es idóneo explicar en términos sencillos los aspectos clave de un tipo de cultivo ecológico que minimiza el impacto, denominado permacultura, de manera que los centros educativos interesados puedan conocer cómo poner en marcha un huerto escolar de estas características. La permacultura es una corriente que promueve no solo una alternativa para la agricultura ecológica, sino que también se trata de una manera de planificar la tierra y una forma de vida más sostenible, considerando todas las posibilidades de cómo vivir en paz como humanos, guardando respeto a la tierra y a sus recursos limitados. Las prácticas propias de un huerto ecológico en permacultura integran aspectos como: o Un diseño integral del espacio, que permita hacer la circulación de materiales y flujo energético, minimizando la producción de residuos. o La relevancia del ecosistema-suelo y de las técnicas para su mantenimiento. o La forma de crear un bancal agrícola “permanente”, con un “acolchado” que crea un microclima adecuado para los cultivos, reduciendo el consumo de agua y evitando la aparición de “malas hierbas”. o Las técnicas de distribución de las plantas y de rotación de cultivos, basadas en las asociaciones y compatibilidades entre ellas, para aumentar la producción disminuyendo los recursos necesarios. o La superposición de árboles alrededor del bancal, para evitar la desecación producida por el viento. o La creación de “composteros”, donde se introduzca toda la materia orgánica producida por el huerto y se devuelva a la tierra en compost, promoviendo el reciclaje de la materia, un metabolismo circular en el huerto. o La aparición de balsas de decantación para recoger la tierra que es arrastrada por la lluvia y volverla a utilizar.

Optical control of functional properties in ferroic materials is now a highly appealing topic because it may entail different paradigms for future technologies. In ferroelectrics, in particular, controlling the properties with light implies noncontact external control of the material's functionality, thereby opening a pathway for developing the next generation of photocontrolled devices. Recently, experimental obser-vations have demonstrated that the dielectric permittivity of charged-domain-wall ferroelectrics can be easily modulated by visible light. However, because of the wide band gap of ferroelectric materials, the physical origin of this phenomenon is still controversial. Here, the photoinduced electronic reconstruction mechanism is proposed as the primary light-absorption mechanism in charged domain walls, allowing an understanding of the origin of the visible-light control of dielectric permittivity in ferroelectric materials.

Photostrictive materials have a growing interest because of their great potential as light-driven actuators, among other optomechanical applications. In this context, the optical control of macroscopic strain in ferroelectrics has recently attracted remarkable attention as an effective alternative to the conventional electric control of strain. Here, a clear correlation between optical absorption and light-induced strain in polycrystalline BaTiO3 is shown. Specifically, the grain size and the sample thickness dependence of optical absorption when the material is irradiated with energy photons lower than the band gap evidence that light absorption at charged domain walls is the core of the observed photo-response in ferroelectrics. The photoinduced electronic reconstruction phenomenon is proposed as the primary physical mechanism for light absorption at charged domain walls. Results open a new pathway to designing ferroelectric-based devices with new functionalities like thickness gradient-based photo-controlled nanoactuators.

Flash sintering is a novel sintering technique that allows high-density ceramics to be obtained at low temperatures and using short dwell times, thus providing an energy-efficient alternative to conventional sintering. The microstructure of flash-sintered samples can be fine-tuned by a proper control of electrical parameters such as current density, electric field, and current profile, yielding significant improvements of functional properties. The starting powder should also be carefully selected since better sintering results are reported for smaller green grain sizes. However, this work evidences time evolution of electrical properties of flash-sintered BaTiO3 ceramics from submicron powders. The results reveal that these transformations greatly depend on powder grain size and can be further adjusted with an adequate selection of electric power profiles. This work provides new insights into ongoing phenomena during field-assisted sintering, such as grain growth and defect formation dynamics. Although the results focus on BaTiO3, it offers a new pathway to tailor the microstructure of flash-sintered ceramics, which may be extended to other electronic materials. Flash sintering experiments on different-sized BTO powders are performed, and the influence of the conditions over the achieved microstructures and functional properties is shown. For smaller powder sizes a time instability of properties is revealed.

Due to environmental concerns, extensive research has been carried out to develop high-performance lead-free piezoceramics capable of replacing commercial lead-based materials. The lead-free (Ba0.7Ca0.3)TiO3−Ba(Zr0.2Ti0.8)O3 system has emerged as a candidate for room temperature transducer applications because a high piezoelectric charge coefficient is achieved in this system for compositions at the morphotropic phase boundary. However, conventional ceramic processing of these eco-friendly piezoceramics demands high energy consumption because long-lasting, high-temperature heat treatments are needed, which often lead to microstructural degradation that compromises the material reliability. Field-assisted flash sintering has started to be explored since the application of an adequate electric field was shown to significantly reduce the sintering time and temperature, thereby controlling grain growth. In this work, Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics are obtained by current-controlled flash sintering of mechanosynthesized nanopowders. Exhaustive control of the sintering parameters allows tailoring of the microstructure, which allows dense fine-grained flash-sintered ceramics exhibiting a high electric field-induced strain response to be obtained.

Light-induced ferroelectric domain wall motion turns out to be a promising phenomenon to develop new photocontrolled devices. However, the physical origin of this light-matter coupling when material is irradiated with visible light remains unclear. Here, a phenomenological model predicting the motion of charged domain walls (CDWs) is developed. The photoinduced electronic reconstruction mechanism is proposed as the primary absorption mechanism, leading to a linear dependence for the polarization perturbation with the light intensity. Domain wall motion is then driven by the energetic difference between domains in a CDW array, such that the macroscopic polarization can be easily tuned.

Los problemas socioambientales presentes y futuros, nos obligan a emprender estrategias urgentes para formar a ciudadanas y ciudadanos críticos, responsables y resilientes, de ahí que adquiera relevancia una educación ambiental en y para el decrecimiento. Para la formación ciudadana, consideramos una pieza clave el compromiso del sistema educativo, así como la formación inicial docente, cuya Alfabetización Ambiental parece ser baja.El trabajo presentado, refleja cómo se ha validado mediante juicio de expertos un instrumento que persigue detectar el grado de Alfabetización Ambiental de los futuros docentes de Educación Infantil y Primaria en base a tres dimensiones ambientales: a) conocimientos y habilidades, b) actitudes y emociones y c) comportamientos. Cada una de ellas conformada por categorías y subcategorías.Después de las valoraciones y modificaciones pertinentes, se analizó la confiabilidad estadística del instrumento realizando una prueba piloto con docentes en formación inicial. Finalmente, se ha obtenido un cuestionario validado que incluye 88 ítems, para evaluar el grado de Alfabetización Ambiental en la formación inicial docente en Educación Infantil y Primaria.

Flash sintering is arousing growing interest because high-density ceramics can be obtained at lower temperatures and shorter dwell times than conventional sintering. However, not only temperature and dwell times should be controlled during flash sintering but also parameters such as the electric field and electric current should be considered. Controlling all the parameters during the processing allows comprehensive control of the microstructure and, consequently, functional properties can be improved. In this work, it is evidenced that an exhaustive control of the flash electric current is a crucial factor for tailoring the microstructure of BaTiO3 ceramics. The results reveal that the most suitable way to control the sintering process is by using non-linear current profiles because better densification and improved grain growth is achieved. Although the results focus on BaTiO3, this work offers a new pathway to tailor the microstructure of flash sintered ceramics, which may be extended to other materials.

Powders of the system (1–x)Bi0.5Na0.5TiO3–xBiFeO3 (x = 0, 0.02, 0.08, 0.10) are synthesized by the combustion reaction method. The crystal structure and the particle size of Bi0.5Na0.5TiO3 are modified by the incorporation of BiFeO3, as can be seen from the infrared spectroscopy and X-ray diffraction results. The inclusion of iron and the increase in the molar percentage of bismuth in the BNT matrix generate new bonds with a different force constant. The structural analysis showed that the addition of BFO to the BNT does not induce any structural phase transition, preserving the rhombohedral symmetry of the Bi0.5Na0.5TiO3 system. The electrical measurements show that the incorporation of iron increases the conductivity of the system generated by an increase in the concentration of oxygen vacancies; alternatively, the addition of 10% of BiFeO3 generates ferrimagnetic behavior reflected in the magnetic hysteresis curves obtained at room temperature.

In this work, the 0.67BiFeO(3)-0.33BaTiO(3) ferroelectric ceramic was prepared by Reaction Flash Sintering (RFS). This preparation technique combines synthesis and sintering in a single Flash experiment. The starting oxides reacted during the flash to produce a stoichiometric well-sintered solid solution at a temperature of 858 degrees C by applying a modest field of 35 V cm(-1). The process takes place in a matter of seconds, which allows obtaining a pure perovskite structure without secondary phases. X-ray diffraction (XRD) results show the mixture of rhombohedral and pseudocubic phases expected for a composition that lies within a morphotropic phase boundary (MPB) region, since a significant splitting is observed in the reflections at 2 theta values of 39 degrees and 56.5 degrees. The microstructure exhibit a peculiar bimodal grain size distribution that determines the electrical properties. As compared with previous results, flash-prepared 0.67BiFeO(3)-0.33BaTiO(3) evidences smaller grain size, as well as slightly lower remanent polarization (P-r) and smaller coercive field (E-c) under similar electric fields. It is also demonstrated that the preparation by RFS provides benefits regarding electrical energy consumption.