First-order magnetostructural transitions underpin the functionality of many magnetocaloric materials and form the basis of emerging solid-state cooling technologies. However, their time-driven response remains underexplored, despite containing intrinsic kinetic information essential for understanding and further optimizing the transformation dynamics. Here, we developed a unique experimental setup to perform simultaneous measurements of magnetization, strain, and temperature change in the benchmark Heusler-alloy Ni–Mn–In under magnetic fields up to 30 T at sweep rates of 10 T/min. By implementing a kinetic measurement protocol, we access both the field-driven and time-driven evolutions of magnetic and structural order parameters along the forward and reverse transition directions. While magnetization rapidly stabilizes after field halting, the probed strain response continues to evolve over extended timescales, indicating distinct relaxation behavior of the measured properties. Quantitative analysis using an extended Avrami–Hay model reveals a secondary diffusive contribution that is required to describe this slow strain evolution. This long-term kinetic dominance of strain also coincides with the substantial structural entropy change characteristic of the Ni–Mn–X family, relating the primary entropy contributor to the strain’s extended response. These results provide a general framework for probing coupled order parameters in first-order multifunctional materials, offering insights for the development of efficient caloric devices.

This study demonstrates the efficacy of ionic liquid (IL)-assisted vapor deposition in achieving high-quality and distinctive crystal film growth of two organic semiconductors (OSCs): a carbazole derivative (TCB) and a phenylamine derivative (TDAB). ILs with different wetting properties (short-chain [C2C1im][NTf2] and long-chain [C8C1im][NTf2]) and engineered shapes (microdroplets and coalesced film) were utilized as solvents in a vacuum. Through a meticulously designed experimental strategy, encompassing both sequential and simultaneous deposition of the IL and the OSC, this study unveils the pivotal role of ILs in shaping the crystallization behavior of the organic compound. Differential scanning calorimetry, polarized light microscopy, high-resolution scanning electron microscopy, and X-ray diffraction were employed for the films' thermal, morphological, and structural characterization. Thin films of TDAB exhibit crystallinity and a greater tendency to grow tridimensionally, forming giant pillars. However, the typical vertical growth of TDAB on solid substrates is altered when deposition occurs on surfaces coated with ILs. The IL promotes the lateral growth of nanostructures. The experimental results reveal variations in film morphology and coverage influenced by the cation alkyl chain length of the IL. In contrast to TDAB, TCB films are amorphous when thermally evaporated on solid substrates. Notably, IL-assisted vapor deposition induces the crystallization of TCB. Furthermore, TCB films deposited on coalesced IL films exhibit enhanced crystallinity and homogeneous horizontal growth, representing a significant finding in the context of thin film deposition and semiconductor device fabrication.

This work studies the influence of an Erbium-Doped Fiber Amplifier (EDFA) on the phase variation of light in an optical fiber. To this end, the state of polarization (SOP) was measured as a function of optical power by adjusting the EDFA amplification, for two different laser output powers (2 dBm and 5 dBm). Results show that phase variation correlates with changes in optical power in both cases.

Extensive research has focused on films formed by pure ionic liquids (ILs). However, growing interest in IL mixtures and their synergistic properties presents new opportunities for targeted applications and fundamental scientific investigations. This study explores the morphology of films composed of mixtures of two ILs, [C2C1im][OTf] and [C8C1im][OTf], co-deposited via physical vapor deposition (PVD)/vacuum thermal evaporation. The primary objective was understanding how varying the IL ratio influences droplet formation, surface coverage, and overall film structure. Thin-film growth was examined on glass substrates coated with indium tin oxide (ITO) and ITO/glass surfaces coated with metallic films (Au and Ag). Film morphology was characterized using optical and high-resolution scanning electron microscopy (SEM), while elemental composition was analyzed via X-ray photoelectron spectroscopy (XPS). The results show that IL mixture morphology is strongly influenced by both IL composition and substrate type. Increasing [C8C1im][OTf] content led to larger microstructures due to improved wetting, particularly on Au surfaces, resulting in nearly fully coalesced films. Metallic surfaces near ITO significantly impacted droplet behavior, with ILs exhibiting a strong affinity for metals, especially when the long-chain IL dominated the mixture. The IL-assisted crystallization of rubrene, a high-performance organic semiconductor (OSC) that typically exhibits poor crystallinity when deposited via PVD, highlights the potential of IL mixtures to enhance organic film quality. X-ray diffraction (XRD) confirmed that [C2C1im][OTf] and [C8C1im][OTf] mixtures significantly improved rubrene crystallinity, demonstrating their potential to create an optimal environment for OSC solubility and crystallization.

Photoelectrochemical water splitting is a promising alternative for sustainable energy production, addressing the growing need for clean energy sources. Hematite is a potential semiconductor for this process due to its abundance, low cost, non-toxicity, and stability. However, bare-hematite-based photoelectrochemical cells face challenges such as low photocurrent density, requiring innovative strategies to improve efficiency. This study explores the combined effects of three key approaches: enhancing crystallinity through high-temperature annealing, increasing specific surface area via nanostructuring, and improving photoanode conductivity through heteroatom doping. Hematite nanowires were synthesized using a hydrothermal method, with Ti-doping introduced during hydrothermal synthesis and subsequent Sn co-doping during an 800 °C annealing process, which also improved crystallinity. The introduction of Ti dopant significantly increased the photocurrent density under simulated solar illumination from 0.03 mA·cm-2 to 0.63 mA·cm-2. Co-doping with Ti and Sn further enhanced performance to 1.27 mA·cm-2. The research explores how heteroatom doping influences the properties of hematite and examines its interaction with high-temperature annealing. These findings are significant for advancing the design of efficient nanostructures for energy conversion applications.

Magnetic calcium phosphate (CaP) nanoparticles have been explored for a wide range of applications, namely biodevices for bone regeneration and local cancer treating through hyperthermia therapy. Numerous shaping techniques to obtain dense and porous ceramic structures are based on colloidal processing principles, in which parameters such as crystallinity, morphology and particle size play an important role in obtaining high solids concentration suspensions to guarantee ceramic structures with high particle packing. With these considerations in mind, this work aims to obtain magnetic and thermo-responsive CaP microparticles, via wet chemical precipitation with the simultaneous addition of Fe2+ and Fe3+. Magnetic microparticles with the ability to preserve their magnetic and magneto-thermal properties have been successfully achieved, due to the presence of well-distributed iron oxide nanocrystallites surrounded by CaP phases. This accomplishment promises great potential for the development of biodevices based on colloidal processing, as some Additive Manufacturing technologies.

Iron-based nanoparticles have emerged as promising candidates for diverse biomedical applications, including cell separation, targeted drug delivery, hyperthermia therapy, and magnetic resonance imaging. This study reports the scalable synthesis of high-magnetization iron-based nanoparticles with controlled anisotropic shapes, achieved via a two-step process. Hematite nanoparticles, featuring nanocube, nanoellipse, and nanoneedle morphologies, were synthesized through the hydrolysis of ferric chloride in the presence of ammonium dihydrogen phosphate, with the morphology precisely tuned by adjusting reagent concentrations. These hematite nanoparticles were subsequently reduced in a hydrogen-based direct reduction at 480 °C, yielding iron-magnetite nanocomposites that retained their anisotropic shapes, exhibited significant porosity, and achieved an exceptional saturation magnetization of 207 emu/g - approximately 150% higher than conventional magnetite nanoparticles. Comprehensive characterization via SQUID magnetometry, Mössbauer spectroscopy, Rietveld refinement of X-ray diffraction data, and XPS for surface analysis confirmed the formation of metallic iron nanoparticles covered by a magnetite shell. Biocompatibility studies demonstrated the biocompatibility of these nanoparticles across a wide concentration range, underscoring their suitability for biomedical applications.

Halogenated benzaldehydes possess unique chemical properties that render them valuable in pharmaceutical synthesis, pesticide formulation, and dye production. However, thorough thermodynamic data for these compounds remain scarce. This study aims to fill this knowledge gap by investigating key physical properties of several halogenated benzaldehydes, namely 4-chlorobenzaldehyde, 4-bromobenzaldehyde, 2,3-dichlorobenzaldehyde, 2,4-dichlorobenzaldehyde, and 2,6-dichlorobenzaldehyde. The physical properties determined in this study include volatility, phase transitions, and water solubility, all of which are crucial for predicting the environmental fate of these compounds. The vapor pressures of both crystalline and liquid phases were measured using a reliable static method, allowing for the determination of standard molar enthalpies, entropies, and Gibbs energies of sublimation and vaporization, as well as their triple points. The melting temperature and molar enthalpy, along with the isobaric molar heat capacity of the crystalline phase, were assessed using differential scanning calorimetry. Water solubility was evaluated at 25 °C through the saturation shake-flask method, complemented by ultra-violet visible spectroscopy. By combining sublimation and solubility data, additional properties such as Gibbs energies of hydration and Henry’s law constants were derived. The experimental results were integrated into existing databases, enhancing the predictive models for properties including melting temperature, vapor pressure, solubility, Gibbs energy of hydration, and Henry’s constant. These findings significantly improve the environmental modeling capabilities, providing valuable insights into the mobility and fate of halogenated benzaldehydes in various environmental contexts.

The electronic properties of the Ca/Sr and Mn site substitution of CaMnGe2O6 and SrMnGe2O6 clinopyroxene systems have been investigated by ab initio calculations within the density functional theory (DFT) framework, using on-site Hubbard U to describe the highly correlated Mn 3d states and a hybrid exchange-correlation functional to obtain the energy band-gap values. Compositions such as (Ca, Sr)1-xCdxMnGe2O6 and (Ca, Sr)Mn1-xCdxGe2O6 (where x = 0.125, 0.25) are predicted to be stable. Also, we proved that implanted Cd impurity could indeed replace either the Ca/Sr or the Mn sites in the crystalline structures. These findings were obtained by combining first principles electric field gradient calculations, using a supercell scheme, with experimental time-differential perturbed angular correlation results. Additionally, DFT calculations showed that Cd substitution is expected to lead to a reduction in the band-gap width. Cd-doped systems were successfully synthesized and experimental results evidencing opportunities for potential band-gap engineering are reported.

We provide deeper insight into the crystal structures, sequential structural phase transitions (I2cm → Cmce → I4/mcm → P4/mmm), thermal expansion, and electronic properties of the n = 2 Dion-Jacobson polar oxide RbNdTa2O7, through X-ray powder diffraction, neutron powder diffraction, Raman studies, and density functional theory calculations. We observed a uniaxial negative thermal expansion (NTE) across the first-order transition, I2cm → Cmce, where the unit cell contracts along the c-axis, which is driven by a contraction of the NdTa2O6 layer. This NTE occurs within the temperature range of the first-order phase transition and contrasts with the corkscrew mechanism typically observed in Ruddlesden-Popper phases. In RbNdTa2O7, the I2cm (hybrid improper ferroelectric) → Cmce (antipolar) transition involves crucial changes in the bond lengths of Nd and Ta polyhedra, coupled with polar to antipolar displacement of the Nd ions, leading to a net contraction in the NdTa2O6 layer along the c-axis, while preserving the overall octahedral tilting magnitude. This transition highlights the intricate interplay between the Nd and Ta coordination and the associated TaO6 distortions. Temperature-dependent Raman spectra analysis further confirms the first-order structural transition and associated NTE, providing evidence for increased bond stiffness across this transition. Additionally, using neutron powder diffraction, we have determined that the transition I4/mcm → P4/mmm occurs at approximately 1150 K. Finally, we have calculated from DFT + U, the partial density of states, the energy bandgaps, and effective masses of the charge carriers of the polar ground structure.

Perturbed angular correlation spectroscopy combined with ab initio electronic structure calculations is used to unravel the structural phase transition path from the low -temperature polar structure to the high -temperature structural phase in Ca 3 Ti 2 O 7 , a hybrid improper ferroelectric. The experimental procedure, conducted at ISOLDE, explores the unique features of a local probe environment approach by monitoring the evolution of the electric field gradient tensor at the calcium sites. The local environments, observed above 1057 K, confirm a structural phase transition from the A 2 1 am symmetry to an orthorhombic Acaa symmetry in the Ca 3 Ti 2 O 7 crystal lattice, disagreeing with the frequently reported avalanche structural transition from the polar A 2 1 am phase to the aristotype I 4 / mmm phase. Moreover, the EFG temperature dependency, within the A 2 1 am temperature stability, is shown to be sensitive to the recently proposed Ca 3 Ti 2 O 7 ferroelectric polarization decrease within the 500-800 K temperature range.

Water pollution is a major environmental challenge. Due to the inefficiency of conventional wastewater treatment plants in degrading many organic complex compounds, these recalcitrant pollutants end up in rivers, lakes, oceans and other bodies of water, affecting the environment and human health. Semiconductor photocatalysis is considered an efficient complement to conventional methods, and the use of various nanomaterials for this purpose has been widely explored, with a particular focus on improving their activity under visible light. This work focuses on developing magnetic and photoactive zinc/magnesium mixed ferrites (Zn0.5Mg0.5Fe2O4) by sol-gel and solvothermal synthesis methods, which are two of the most important and efficient methods used for the synthesis of ferrite nanoparticles. The nanoparticles (NPs) synthesized by the sol-gel method exhibited an average size of 14.7 nm, while those synthesized by the solvothermal method had an average size of 17.4 nm. Both types possessed a predominantly cubic structure and demonstrated superparamagnetic behavior, reaching a magnetization saturation value of 60.2 emu g−1. Due to the high recombination rate of electrons/holes, which is an intrinsic feature of ferrites, surface functionalization with silver was carried out to enhance charge separation. The results demonstrated a strong influence of adsorption and of the deposition of silver. Several optimization steps were performed during synthesis, allowing us to create efficient catalysts, as proved by the almost full removal of the dye malachite green attaining 95.0% (at a rate constant of 0.091 min−1) and 87.6% (at a rate constant of 0.017 min−1) using NPs obtained by the sol-gel and solvothermal methods, respectively. Adsorption in the dark accounted for 89.2% of the dye removal for nanoparticles prepared by sol-gel and 82.8% for the ones obtained by the solvothermal method. These results make mixed zinc/magnesium ferrites highly promising for potential industrial application in effluent photoremediation using visible light.

The effect of Zn addition on cationic distribution, structural and magnetic properties of nanocrystalline Li-Zn ferrites are reported. X-ray diffraction confirms the formation of spinel nanoferrites with an average grain diameter of 34 - 82 nm. The addition of Zn results in a linear increase of lattice parameter and X-ray density. Magnetism in the studied samples is governed by the Yafet-Kittel three-sub-lattice model, shown by a non-zero canting angle. The variation in magnetic properties is correlated with the calculated cationic distribution. A new antistructural modeling explains the changes in the concentration of donor and acceptor surface active centers.

The development of increasingly smaller electronic devices brings on heat dissipation challenges, which can severely hinder their performance. Consequently, there is a critical need to maintain the working temperature of these devices at optimal values. At room temperature, the versatile design and adaptability of fluidic thermal switches makes them an auspicious solution. In this work, the large heat conductivity and magnetic material compatibility of Galinstan motivated the production of a novel ferromagnetic fluid. Through mechanical alloying within an inert atmosphere, we embedded Ni microparticles in a Galinstan matrix, which provided a liquid metal with a ferromagnetic behavior. This fluid is suitable for a wide range of applications in thermal management. Here, we experimentally demonstrate that a Galinstan-based mixture containing 2.6 wt% of Ni can serve as heat exchange medium in a magnetically activated fluidic thermal switch device. This mixture establishes an optimal thermal bridge between heat source and sink, enabling heat dissipation from the source. This effect intensifies with the device operating frequency, reaching a maximum temperature span of 19.8 % and a maximum switching ratio of 1.26. These results demonstrate the potential of the developed fluid to be integrated into fluidic technologies for temperature control of electronic components.

Photoelectrochemical (PEC) water splitting offers a sustainable route for hydrogen production, leveraging noncritical semiconductor materials. This study introduces a seed layer-free hydrothermal synthesis approach for semiconductor photoanodes based on tungsten trioxide (WO3) nanoplatelets. Aiming to boost the efficiency of photoelectrochemical water splitting through optimization of the synthesis parameters of bare WO3, focusing on temperature, time, and layer thickness, we systematically explored their effects on the morphological, structural, and optical characteristics of WO3 photoanodes. Combining a low-temperature regime (90 °C for 12 h) with a multilayer strategy (up to six-layers) resulted in significant improvements in photocurrent. Particularly, the five-layer sample exhibited a remarkable increase of over 70% compared to the single-layer photoanode. Morphological aspects, particularly the fractal dimension of nanoplatelets and the emergence of the (220) crystalline orientation, usually neglected, were found to play pivotal roles in modulating the PEC response. Rietveld refinement of X-ray diffraction patterns further underscored the importance of crystallographic facets, volume unit cell expansion, and microstrain in influencing photocurrent outcomes. Furthermore, we adapted the Mott-Schottky equation to incorporate the fractal dimension reflecting the nanostructures' nature, usually set to a planar interface. Our findings highlight the interchange between nanoplatelet morphology and structural parameters in determining the PEC efficiency of WO3 photoanodes.

Lead-free ceramic powder with composition 0.8BaTiO3-0.2Bi(Mg0.5Ti0.5)O3 [BT-BMT] was synthesized by sol–gel method. Two separate sets of free-standing polymer composite films were prepared by the simple and affordable solution casting method. The BT-BMT particles were dispersed into the individual polymer matrix: P(VDF-TrFE-CFE) terpolymer (TP) and P(VDF-TrFE) copolymer (CP). The filler content in both cases was maintained as 7 wt%. The synthesized ceramic powder, the raw polymer powder and the prepared polymer composite films were characterized by X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared(ATR-FTIR) and Raman spectroscopy techniques at room temperature.XRD results confirmed the phase formation in the polymer composite films, that exhibited the peaks from the two phases: perovskite phase (from the filler particles) with a strong (110) preferential orientation and the peaks associated with the respective polymer.The FTIR and Raman spectra revealed the polar β- and γ-phases of the PVDF. Besides, highly diffused peak associated with the nonpolar-α-phase was also observed.Dielectric and ferroelectric properties were studied that revealed relaxor behavior in the terpolymer based films.This research suggests a successful method to include oxide nanoparticles in the polymer matrix, which while maintaining the properties of the polymer and the fillers can lead to high-quality flexible free-standing polymer composite films that have the potential to be used in various applications such as energy storage, electrocaloric cooling, energy harvesting applications.

Climate change and the increasing demand for energy globally have motivated the search for a more sustainable heat-pumping technology. Magnetic refrigeration stands as one of the most promising alternative technologies for clean and efficient heat pumps of the future. The rotating magnetocaloric effect (RMCE) has previously been studied in materials with magnetocrystalline anisotropy due to its potential to improve devices by requiring only a single magnetic field region, but these materials are fragile and costly to obtain, making them inviable for applications. It has been shown that by exploiting the demagnetizing effect, an RMCE is, in fact, attainable in any polycrystalline magnetocaloric sample with an asymmetric shape, without requiring magnetocrystalline anisotropy. Using gadolinium as a case study, we provide a theoretical framework for computing the demagnetizing field-based RMCE and present thorough experimental verification for different magnetic field intensities and a wide temperature range. Direct measurements of the RMCE in gadolinium reveal that a significant adiabatic temperature difference (1.2 K) and refrigerant capacity (7.44 J kg ^−1 ) can be attained within low magnetic field amplitudes (0.4 T). Utilizing lower magnetic field intensities in a magnetocaloric heat pump can significantly diminish the need for permanent magnet materials, thus reducing the overall device cost, size, and weight, ultimately enhancing the feasibility of mass-producing such devices.

Currently, magnetocaloric refrigeration technologies are emerging as ecofriendly and more energy-efficient alternatives to conventional expansion-compression systems. However, major challenges remain. A particular concern is the mechanical properties of magnetocaloric materials, namely, their fatigue under cycling and difficulty in processing and shaping. Nevertheless, in the past few years, using multistimuli thermodynamic cycles with multicaloric refrigerants has led to higher heat-pumping efficiencies. To address simultaneously the challenges and develop a multicaloric material, in this work, we have prepared magnetocaloric-based flexible composite mats composed of micrometric electroactive (EA) polyvinylidene fluoride (PVDF) fibers with embedded magnetocaloric/strictive La(Fe,Si)(13) particles by the simple and cost-effective electrospinning technique. The composite's structural characterization, using X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and measurements of the local-scale piezoresponse, revealed a cubic NaZn13-type structure of the La(Fe,Si)(13) phase and the formation of the dominant polar beta-phase of the PVDF polymer. The PVDF-La(Fe,Si)(13) composite showed an enhancement of the longitudinal piezoelectric coefficient (effective d(33)) (-11.01 pm/V) compared with the single PVDF fiber matrix (-9.36 pm/V). The main magnetic properties of La(Fe,Si)(13) powder were retained in the PVDF-La(Fe,Si)(13) composite, including its giant magnetocaloric effect. By retaining the unique magnetic properties of La(Fe,Si)(13) embedded in the electroactive piezoelectric polymer fiber mats, we have designed a flexible, easily shapeable, and multifunctional composite enabling its potential application in multicaloric heat-pumping devices and other sensing and actuating devices.

Laser ablation was used to successfully fabricate multiferroic bilayer thin films, composed of BaTiO3 (BTO) and CoFe2O4 (CFO), on highly doped (100) Si substrates. This study investigates the influence of BaTiO3 layer thickness (50–220 nm) on the films’ structural, magnetic, and dielectric properties. The dense, polycrystalline films exhibited a tetragonal BaTiO3 phase and a cubic spinel CoFe2O4 layer. Structural analysis revealed compression of the CoFe2O4 unit cell along the growth direction, while the BaTiO3 layer showed a tetragonal distortion, more pronounced in thinner BTO layers. These strain effects, attributed to the mechanical interaction between both layers, induced strain-dependent wasp-waisted behavior in the films’ magnetic hysteresis cycles. The strain effects gradually relaxed with increasing BaTiO3 thickness. Raman spectroscopy and second harmonic generation studies confirmed BTO’s non-centrosymmetric ferroelectric structure at room temperature. The displayed dielectric permittivity dispersion was modeled using the Havriliak–Negami function combined with a conductivity term. This analysis yielded relaxation times, DC conductivities, and activation energies. The observed BTO relaxation time behavior, indicative of small-polaron transport, changed significantly at the BTO ferroelectric Curie temperature (Tc), presenting activation energies Eτ in the 0.1–0.3 eV range for T < Tc and Eτ > 0.3 eV for T > Tc. The BTO thickness-dependent Tc behavior exhibited critical exponents ν ~ 0.82 consistent with the 3D random Ising universality class, suggesting local disorder and inhomogeneities in the films. This was attributed to the composite structure of BTO grains, comprising an inner bulk-like structure, a gradient strained layer, and a disordered surface layer. DC conductivity analysis indicated that CoFe2O4 conduction primarily occurred through hopping in octahedral sites. These findings provide crucial insights into the dynamic dielectric behavior of multiferroic bilayer thin films at the nanoscale, enhancing their potential for application in emerging Si electronics-compatible magneto-electric technologies.