This study demonstrates a simple and cost-effective route to induce relaxor ferroelectric behavior in BaTiO3 (BTO) ceramics. Sintered pellets prepared from unmilled and milled BTO powders were characterized using Xray diffraction (XRD), dielectric spectroscopy, and P-E measurements. XRD confirmed the retention of the tetragonal P4mm phase in all samples. Dielectric spectra showed a clear evolution from a sharp Curie peak (-120 degrees C) in pellets obtained from unmilled powders to a broad diffuse transition (60 degrees C-180 degrees C) after milling; with the diffuseness coefficients increasing from 0.52 to 1.30. Piezoresponse force microscopy corroborated the formation of polar nanoregions in sintered pellets obtained from milled BTO. P-E loops exhibited the expected relaxor-type slim hysteresis, with reduced Pr (1.32 mu C/cm2) and Ec (5.69 kV/cm). Milling also improved functional performance, the recoverable energy density (Wrec) increased from 0.22 to 0.31 J/cm3, while the energy storage efficiency (eta) increased from 15 % to 85 %.

This study demonstrates the enhancement of dielectric breakdown strength and energy-storage performance in a high-entropy relaxor ferroelectric ATiO3 ceramic achieved by substituting zirconium for titanium sites. In particular, high-energy ball milling followed by controlled sintering is employed to successfully synthesize a high-entropy composition in which Ti4+ is partially substituted by Zr4+. The high configurational entropy of the A-site (ΔSconfig ≈ 1.61 R) induces severe local lattice distortions and chemical disorder that inherently disrupt long-range ferroelectric order and promote polar nanoregion formation. The additional Zr4+ substitution at the B-site further amplifies this effect through local BO6 octahedral distortion, broadening the ferroelectric-to-paraelectric phase transition and reinforcing the relaxor-type response. The resulting material exhibits a significantly reduced remanent polarization (0.67 μC cm−2), an increased recoverable energy density (0.79 J cm−3), and a high energy efficiency (90.73%), outperforming conventional BaTiO3. These findings confirm that cationic addition in high-entropy ceramics provides an effective and environmentally benign pathway to design high-performance ferroelectric materials suitable for fast-charging, high-energy-density storage applications.

This study presents a simple and cost-effective approach to enhance the dielectric and piezoelectric properties of bismuth sodium titanate [Bi0.5Na0.5TiO3 (BNT)] by incorporating barium titanate [BaTiO3 (BT)] via high-energy ball milling. X-ray diffraction results confirmed the formation of BNT-xBT solid solutions and a structural transition from rhombohedral to tetragonal symmetry. Frequency-dependent dielectric measurements showed a notable increase in the relative permittivity (1750) of doped BNT, which is > 2-fold higher than that of pristine BNT, owing to the diminished size of ferroelectric domains, confirmed via piezoresponse force microscopy analysis. Temperature-dependent analysis of permittivity revealed a broad peak and diffuse phase transition after BT incorporation, indicating the presence of small ferroelectric domains. Polarization-electric field loops exhibited a reduced coercive field from similar to 60 kV cm(-1) in pure BNT to similar to 23 kV cm(-1) in BNT-xBT samples, owing to the coexistence of small ferroelectric domains. This facilitated polarization switching, resulting in slim hysteresis loops. The piezoelectric coefficient improved from 50 pC N-1 of pristine BNT to 120, 158, and 165 pC N-1 for BNT-xBT with x values of 0.08 wt%, 0.09 wt%, and 0.10 wt%, respectively. This improvement is attributed to changes in the crystal structure and increased domain mobility. These findings highlight the potential of BNT-xBT, obtained via high-energy ball milling, as a promising lead-free piezoelectric material for advanced electromechanical applications.

This research focuses on studying the magnetodielectric coupling at room temperature in lanthanum ferrite induced by cobalt substituting iron sites. The study involved varying cobalt content from 0 to 0.1 mol, with samples synthesized via high-energy ball milling. The evolution of crystal structure, dielectric, and magnetic properties was analyzed. X-ray diffraction (XRD) and Rietveld refinement confirmed the orthorhombic singlephase structure with the Pnma space group in the doped lanthanum ferrite. Vibrating-sample magnetometry results demonstrated that cobalt doping alters the antiferromagnetic order of lanthanum ferrite, inducing ferromagnetism, with a maximum specific magnetization of 1.25 emu/g observed at 0.075 mol cobalt content. Scanning electron microscopy (SEM) analysis revealed an increase in grain size with higher cobalt content, which impacts the material's electrical and dielectric properties. The doped ferrites exhibited lower relative permittivity values compared to pure LaFeO3. Additionally, the presence of cobalt reduced the dielectric dissipation factor, attributed to minor crystal structure distortions. Notably, magnetodielectric coupling was observed in these multiferroic materials for the first time, evidenced by changes in relative permittivity under varying applied fields and frequencies. The highest magnetodielectric coupling was achieved at 0.025 mol cobalt doping, with relative permittivity values ranging from 70 to 26 across frequencies from 50 to 1000 Hz. These findings confirm that cobalt-doped lanthanum ferrites exhibit magnetodielectric coupling at room temperature, suggesting potential for expanded technological applications.

This work presents a systematic investigation of the effects of the crystal structure and cation distribution on the multiferroic properties of the zinc-doped ferrite Ni1-xZnxFe2O4 (0 ≤ x ≤ 1, Δx = 0.1) synthesized via high–energy ball milling followed by heat treatment. X-ray diffraction (XRD) analysis confirmed the successful synthesis of cubic spinel ferrite across all the studied compositions, whereas structural changes, such as lattice size, porosity and crystallite size, exhibited compositional dependence. Scanning electron microscopy (SEM) of the pellet surfaces revealed the dependence of the grain size distribution and porosity on the zinc content. Raman spectroscopy analysis allows the determination of the distribution of cations as a function of the Zn content, revealing the change from an inverse to a mixed spinel structure. X-ray photoelectron spectroscopy (XPS) allows the determination of the cations of Ni2+, Ni3+, Fe2+ and Fe3+ distributed in tetrahedral and octahedral sites, resulting in new magnetic and dielectric interactions in the samples. Magnetic hysteresis loops confirmed the ferromagnetic ordering of the synthesized ferrites, with saturation magnetization values ranging from 40 to 76 emu/g for 0 to 0.5 mol of Zn, respectively. The observed increases in relative permittivity and conductivity with increasing zinc content are attributed to the redistribution of Fe3+ ions within the crystal lattice, which is modulated by the Zn doping level. These findings confirm that bulk zinc-doped nickel ferrites synthesized by high–energy ball milling exhibit improved ferromagnetic and dielectric properties, suggesting potential for expanded technological applications.

This study presents a facile method for synthesizing high-entropy (HE) bulk ceramics with a relaxor ferroelectric behavior. The approach involves high-energy ball milling followed by sintering to obtain perovskite-like ABO3 ceramics (A = Ba, Bi, Zn, Na, and Sr; B = Ti). The crystal structure and electrical properties of these ceramics are investigated. X-ray diffraction analysis demonstrates the formation of a HE perovskite phase, along with the presence of small quantities of secondary phases. The relative permittivity and dielectric losses are 2247 and 0.18, respectively. Ferroelectric loops at 10 Hz demonstrate a relaxor ferroelectric behavior, with maximum polarization, remanent polarization, and coercivity values of 16.7 mu C/cm2, 0.96 mu C/cm2, and 1 kV/cm, respectively. The relative permittivity dispersion factor (gamma) is determined to be 1.8, again confirming the relaxor ferroelectric behavior. Ferroelectric measurements indicate an improved energy storage density of 0.69 J/cm3, which represents enhancement in comparison with barium titanate (BaTiO3 or BTO) ceramics.

Bajo la premisa de que la permineralización inducida por sílice durante la formación de fósiles silicatados comporta la estabilización de fases intermedias de estructura zeolítica, planteamos la reproducción de este proceso natural mediante la síntesis de materiales zeolíticos en un sistema reactivo hidrotermal isotérmico (140 ºC), con NaOH, a partir de caolín como fuente de aluminosilicato. El resultado es la obtención de diversas mezclas de las fases hidroxicancrinita, hidroxisodalita, zeolita tipo NaP 1 y analcima, en un rango de tiempo de reacción que va de 7 a 9 horas. El análisis de estas mezclas se ha llevado a cabo mediante difracción de Rayos-X en muestra polvo y representa una guía útil para identificar mezclas complejas de estructuras zeolíticas sódicas, reportando tablas (hkl)/dhkl para cada una de las fases. El estudio incorpora dos hallazgos inéditos: i) la transición de fase de hidroxisodalita a hidroxicancrinita se muestra por primera vez en condiciones isotérmicas sin carbonatos, y ii) la elucidación del grupo de simetría espacial para la hidroxisodalita da como resultado el grupo cúbico quiral P4332 (o P4132).

This study demonstrates that high-energy ball milling induces a transition from diamagnetic to weak ferromagnetism order in BaTiO3. In addition, combining mechanical milling with niobium doping enhances its dielectric and ferroelectric properties, yielding a room-temperature multiferroic material. To achieve this, niobium-doped BaTiO3 powders with dopant concentrations of 0.0-0.1 wt% were prepared by high-energy ball milling for 5 h. The effect of Nb5 + incorporation on the crystal structure and electrical properties was analyzed. X-ray diffraction with Rietveld refinements confirmed that all samples retained a tetragonal phase. Electrical analyses revealed that low Nb concentrations (0.025 and 0.050 wt%) improved the ferroelectric and dielectric behavior of the samples, achieving a maximum polarization of 7.6 mu C/cm2 and a relative permittivity of 1700, outperforming undoped BaTiO3. Finally, magnetic hysteresis loops confirmed weak ferromagnetism in all samples. This process converted Ti4+ into Ti3+ with unpaired spins, generating a nonzero magnetic moment, as corroborated by X-ray photoelectron spectroscopy analysis.

This work reports a detailed study of the crystal structure and electrical properties of a potential lead-free piezoelectric Bi0.5Na0.5TiO3 co-doped with Ba2+ and Fe3+ sintered at relatively low temperature (900 degrees C). The effect that co-dopants have over the electric properties in (Bi0.5Na0.5)(1-x)Ba(x)Ti(1-y)FeyO(3-0.5y), varying x from 0 to 0.075, Delta x = 0.025, and y from 0 to 0.075, Delta y = 0.025, was evaluated. XRD analysis showed a successful synthesis of co-doped BNT ceramics with a rhombohedral structure for samples with x < 0.075. In contrast, the sample with x = 0.075 exhibited the coexistence of the rhombohedral and tetragonal structures, confirmed by Rietveld refinement. The co-doping promotes the grain size growth and increase the pellets' density from 93 % to 98 %. Dielectric spectroscopy analysis, conducted in the range from 25 to 500 degrees C, showed an increase in the relative permittivity with the dopant concentration, specifically at high temperatures. Electric analysis validate the piezoelectric behavior and the electric polarization of the co-doped BNT ceramics, unveiling a maximum remnant polarization (P-r) of 25.6 mu C/cm(2) and, a maximum piezoelectricity coefficient of 53 pC/N, which varied depending on the composition. The obtained results demonstrate that co-doping BNT ceramics with Ba2+ and Fe3+ cations lower the sintering temperature typically used in the solid-state reaction to obtain pure BNT, showing similar properties compared to those of the same material sintered at higher temperatures and longer times.

In this research, LaFeO3 doped with different concentrations of Ni2+ at Fe sites, ranging from 0.1 to 0.5 with a Δx of 0.1, was studied. The synthesis process involved high-energy milling followed by heat treatment at a low temperature, 1073 K, to induce ferromagnetic order (FM). Moreover, the effects of cation doping on the crystal structure and multiferroic properties were determined. X-ray diffraction analysis and Rietveld refinement confirmed that doped lanthanum ferrite with an orthorhombic structure (Pnma) was obtained for all the studied dopant levels. The magnetic hysteresis loops change from antiferromagnetic (AFM) to weakly ferromagnetic at room temperature when Ni2+ is introduced into the LaFeO3 crystal structure, which is attributed to spin canting due to the difference in ionic radius between the Fe3+ and Ni2+ cations and to the frustration of the magnetic cycloid due to the existence of uncompensated ions. Regarding the dielectric properties, the doped ferrites show semiconductor behavior with high values of relative permittivity as the doping concentration increases. XPS spectra confirmed the existence of adsorbed oxygen associated with oxygen affinity as a mechanism of charge compensation due to vacancies and oxidation from Fe3+ to Fe4+.

Bi0.5Na0.5TiO3 (BNT) emerges as a promising ferroelectric and piezoelectric lead-free candidate to substitute the contaminant Pb[TixZr1−x]O3 (PZT). However, to obtain optimal ferroelectric and piezoelectric properties, BNT must be sintered at high temperatures. In this work, the reduction of sintering temperature by using iron added to BNT is demonstrated, without significant detriment to the dielectric properties. BNT-xFe with iron from x = 0 to 0.1 mol (∆x = 0.025) were synthesized using high-energy ball milling followed by sintering at 900 °C. XRD analysis confirmed the presence of rhombohedral BNT together with a new phase of NaFeTiO4 (NFT), which was also corroborated using optical and electronic microscopy. The relative permittivity, in the range of 400 to 500 across all the frequencies, demonstrated the stabilization effect of the iron in BNT. Additionally, the presence of iron elevates the transition from ferroelectric to paraelectric structure, increasing it from 330 °C in the iron-free sample to 370 °C in the sample with the maximum iron concentration (0.1 mol). The dielectric losses maintain constant values lower than 0.1. In this case, low dielectric loss values are ideal for ferroelectric and piezoelectric materials, as they ensure minimal energy dissipation. Likewise, the electrical conductivity maintains a semiconductor behavior across a range of 50 Hz to 1 × 106 Hz, indicating the potential of these materials for applications at different frequencies. Additionally, the piezoelectric constant (d33) values decrease slightly when low concentrations of iron are added, maintaining values between 30 and 48 pC/N for BNT-0.025Fe and BNT-0.05Fe, respectively.

La refrigeración magnética es una tecnología eficiente y de bajo impacto ambiental. Un material económico es el La0.7Ca0.3MnO3 (LCM), pero con una temperatura Curie menor al ambiente y un rango de trabajo estrecho. Se propone utilizar magnetocalóricos bifásicos a partir de mezclas de manganitas de lantano LCM dopada con 0.2 mol de Cr y LCM dopada con 0.1 mol de Sr, en proporciones en peso 50-50. Mediante difracción de rayos X se confirmó la presencia de dos fases, Pbnm y R3c. Mediante magnetometría de muestra vibrante se confirmó orden ferromagnético a temperatura ambiente. La caracterización eléctrica, mostró valores de permitividad relativa entre 1013 y 105 en un rango de frecuencia desde102 hasta 5x106 Hz y pérdidas dieléctricas entre 103 y 1, teniendo un comportamiento de semiconductor. Con un acoplamiento magnetoeléctrico de magnetorresistencia hasta el 3 %.

El bismuto sodio titanato (Bi0.5Na0.5TiO3) es un cerámico que ha captado la atención en los últimos años debido a sus propiedades piezoeléctricas y su composición libre de plomo. Estas características lo han posicionado como alternativa para sustituir materiales piezoeléctricos basados en plomo, los cuales son altamente contaminantes. En este trabajo se analizan las propiedades eléctricas, dieléctricas y estructurales del potencial piezoeléctrico Bi0.5Na0.5TiO3, el cual fue obtenido por molienda de alta energía durante 5 h y sinterizado a baja temperatura (900°C). Los resultados obtenidos por difracción de rayos X confirman la obtención del compuesto monofásico Bi0.5Na0.5TiO3 con estructura rombohedral. En tanto, las propiedades dieléctricas exhiben valores de permitividad (465 a 419) altamente estables a altas frecuencias con bajas perdidas dieléctricas. Las curvas de polarización eléctrica denotan un comportamiento característico de un ferroeléctrico duro, con un campo coercitivo significativamente grande de 50 kV/cm y una polarización de saturación de 25.7 µC/cm2.

Se informa sobre el comportamiento magnético y dieléctrico de ferritas de bismuto sintetizadas mediante procesos de molienda y ajustadas mediante la reducción del tamaño de cristalito y la microdeformación generada por la molienda mecánica. Se usaron mezclas estequiométricas de Bi2O3 y Fe2O3. La reducción del tamaño de cristalito se realizó a diferentes tiempos de molienda (0-60 min) con un porcentaje de 5% en peso de metanol. Se evaluaron el tamaño de cristalito y la microdeformación mediante difracción de rayos X. El comportamiento magnético se evaluó con magnetometría de muestra vibrante. Los polvos obtenidos se sinterizaron mediante plasma de chispa a 750 °C. Los resultados muestran una transformación de la fase BiFeO3 a Bi2Fe4O9 con tiempos más largos de reducción del tamaño de cristalito. Se discuten las relaciones entre la transformación microestructural y las reacciones de oxidación-reducción, así como los cambios antiferromagnético-ferromagnético. Las propiedades dieléctricas disminuyeron con tiempos más largos de reducción del tamaño de cristalito.

La contaminación del agua por colorantes representa un serio problema debido a sus efectos perjudiciales en la salud y el entorno, ante esta situación se han desarrollado múltiples métodos para su remediación. En este contexto, los procesos de oxidación avanzada, fundamentados en la fotocatálisis, emergen como uno de los más eficaces. En esta investigación se examinó la capacidad de degradación de la ferrita de lantano con diferentes niveles de dopaje, con Co2+ y Ca2+, sintetizada mediante molienda de alta energía asistida con tratamiento térmico a 800°C, para la eliminación de azul de metileno, como contaminante en medio acuoso. Los resultados de difracción de rayos X confirmaron la síntesis de una fase pura de ferrita de lantano con estructura cristalina ortorrómbica (Pbnm), independiente del nivel de dopaje. Al mismo tiempo, se cuantificó la energía de la banda prohibida de las ferritas, las cuales se encontraron en el rango de la luz visible, 2.10 a 2.30 eV. La capacidad de degradación se evaluó bajo un espectro de luz visible utilizando azul de metileno como contaminante, evidenciando una elevada eficiencia en la degradación, cercana al 65 % en 180 minutos. El comportamiento magnético de las muestras, determinado mediante magnetometría de muestra vibrante, reveló un orden ferromagnético para las muestras dopadas, convirtiendo a este material en un fotocatalizador recuperable magnéticamente.

In this work, the enhancement of the magnetocaloric effect by mixing different alkaline-earth-doped lanthanum manganites is reported. The sintering process of the mixed manganites promotes the unexpected presence of a strontium–calcium-co-doped lanthanum manganite phase that enhances the magnetocaloric properties of the composite. Consistent with this result, the composite shows three Curie temperatures at 263 K, 309 K, and 284 K, attributed to the three different phases found. The transition was identified as a second-order phase transition by the Arrott plots. A maximum entropy change of 11.66 J·(kg·K) −1 was obtained for the composite at 18 kOe. It corresponds to a refrigeration cooling power of 484.98 J·kg −1 near room temperature. The results demonstrated the synergistic contribution to the magnetocaloric properties of individual phases, enhancing the magnetocaloric effect by obtaining a composite.

Multiferroic BaTiO3 exhibiting ferroelectric and ferromagnetic behavior was synthesized via the high-energy ball milling of pure BaTiO3 (BTO) powders for durations ranging from 15 to 60 min, followed by pressing and sintering at 1200 degrees C X-ray diffraction patterns of all synthesized samples predominantly revealed a BTO phase with a tetragonal structure and a secondary Ba12Fe28Ti15O84 (BFTO) phase. The BFTO phase was formed after milling for more than 30 min because of chemical interactions between the BTO powder and milling media. Vibrating sample magnetometry confirmed the ferromagnetic nature of the sintered pellets. The specific magnetization increased with increasing milling duration, reaching a maximum value of 1.15 emu/g after 60 min of milling. This increase can be attributed to the distortion of the crystal structure and presence of a secondary phase, as confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Additionally, electrical characterization revealed the dielectric nature of the materials, with relative permittivity ranging from 500 to 1800, maximum spontaneous polarization from 9.77 to 11.31 mu C/cm2, coercive field from 3.86 to 11.12 kV/cm, and AC conductivity from 1 x 10-6 to 1 x 10-3 S/cm. The method described in this study is a simple and costeffective approach to produce multiferroic materials with ferroelectric and relaxor ferroelectric behavior at room temperature, broadening their potential for technological applications.

LaFeO3 is a type II multiferroic material which exhibits improper ferroelectricity induced by magnetic order (antiferromagnetism). However, the antiferromagnetic order limits its applications. This study demonstrates the induction of ferromagnetism in LaFeO3 by doping with cobalt, varying the level of cobalt from 0 to 0.5 mol. Moreover, the effects of cobalt on the crystal structure, magnetic and dielectric properties are described. The XRD results show that at doping concentrations lower than 0.3 mol, LaFeO3 maintains its orthorhombic structure (Pnma), while at higher cobalt concentrations the rhombohedral (R-3c) LaCoO3 phase emerges. In addition, cobalt doping induces ferromagnetism because cobalt occupies iron positions until the solubility limit is reached (0.3 mol). All samples present high relative permittivity values, which increase with increasing cobalt content and temperature. Furthermore, the presence of cobalt results in a decrease in the dielectric dissipation factor for cobalt contents lower than 0.3 mol, due to the inhibition in the formation of vacancies. However, the presence of LaCoO3 at high cobalt contents increases the dielectric losses due to the presence of a mixtures of phases. Moreover, the electric polarization curves exhibited weak ferroelectric behavior for ferrites with cobalt contents lower than 0.3 mol, and lossy improper ferroelectric type behavior for samples with higher contents.

This study investigated the effect of neodymium (Nd) on the crystal structure and magnetocaloric properties of lanthanum–strontium manganites (La0.7−xNdxSr0.3MnO3, 0 ≤ x ≤ 0.4), synthesized by assisted high-energy ball milling. Rietveld analysis from X-ray diffraction disclosed that Nd3+ did not promote crystallographic phase transitions. The rhombohedral crystal structure remained in the R-3c space group for all the compositions, with slight changes in lattice parameters. The defect model allowed the quantification of the Mn4+ occupancy, which is in the range from 0.20 to 0.26 mol, for 0.1 and 0.4 mol of Nd3+, respectively. The presence of Mn4+ promoted further ferromagnetic interactions, increasing systematically the saturation magnetization, from 65 A·m2·kg−1 to 73 A·m2·kg−1, and a diminution in the Curie temperature from 364 to 255 K, for 0 and 0.4 mol of Nd3+, respectively, obtained by temperature-dependent magnetization measurements. The doped manganite with 0.35 mol of Nd3+ showed a maximum of entropy change of 3.73 Jkg−1 K−1 at 1.8 T near room temperature, with a relative cooling power of 82 Jkg−1 and temperature-averaged entropy change, TEC(3) and TEC(10), of 3.53 and 3.06 Jkg−1 K−1, respectively. It is demonstrated that the presence of Nd3+ modulates the Curie temperature near room temperature and enhances the magnetocaloric properties at low magnetic fields, making these manganites a promising material for magnetocaloric applications.

Los cerámicos piezoeléctricos de composición Pb[TixZr1-x]O3 (PZT) son ampliamente utilizados por sus excelentes propiedades.Sin embargo, son altamente contaminantes, por su contenido en plomo. En este trabajo se analizan las propiedades dieléctricas del potencial piezoeléctrico libre de plomo, Bi0.5Na0.5TiO3 (BNT) dopado con distintos contenidos de Fe3+, sinterizados a baja temperatura. La síntesis y procesamiento se realizó por medio de molienda mecánica de alta energía y posterior sinterización a 900 °C. Los resultados de difracción de rayos X confirman la síntesis BNT con estructura cristalina romboédrica para todo el rango de sustitución con Fe3+. Adicionalmente, la permitividad relativa de las muestras dopadas se encontraron en un rango de 400 a 500 mostrando mayor estabilidad en todo el rango de frecuencias, en comparación de la BNT sin dopar, se encuentran, sin observar una tendencia clara en función del contenido de Fe3+. Las pérdidas dieléctricas y conductividad eléctrica revelan la obtención de materiales con potencial para materiales piezoeléctricos a bajas frecuencias.