Interface-Driven Multiferroicity in Cubic BaTiO3-SrTiO3 Nanocomposites

Optical characterization and defect-induced behavior in ZnAl1.999Ho0.001O4 spinel: Unraveling novel insights into structure, morphology, and spectroscopic features

The ZnAl1.999Ho0.001O4 phosphor, prepared by the solid-state method, crystallizes in the cubic spinel structure. Morphology and chemical composition homogeneity were determined via Energy Dispersive X-ray and SEM analysis. The (Eg) optical band gap was evaluated from the UV/vis absorption spectrum, confirming direct transition behavior according to Tauc's law. The Urbach energy (Eu) in the ZnAl1.999Ho0.001O4 spinel was higher than that in the ZnAl2O4 spinel, indicating increased disorder and a higher concentration of defects due to Ho3+ ions. The penetration depth (δ(λ)), optical extinction (k(λ)), and refractive index (n(λ)) were assessed across wavelengths (λ). The room temperature absorption spectrum revealed several peaks corresponding to the 4f-4f transitions of Ho3+ ions.

Study of Cation Distribution and Photocatalytic Activity of Nonthermal Plasma-Modified NiZnFe2O4 Magnetic Nanocomposites

In this study, NiZnFe2O4 composite was synthesized using a sol-gel route and subjected to nonthermal plasma treatment for tailoring their cations' distribution and physicochemical, magnetic, and photocatalytic properties. Microwave plasma treatment was given to the composites for 60 min in support of postsynthesis sintering at 700 °C for 5 h. X-ray diffraction (XRD) analysis was conducted on pre- and postplasma-modified ferrite composites to identify phase-pure cubic spinel structure and cations' distribution. The cation distributions were measured from the ratio of XRD intensity peaks corresponding to (220), (311), (422) and (440) planes. The intensity ratio of plasma-treated ferrite composites decreased compared to that of pristine composites. The crystallite size and lattice constant were increased on plasma treatment of the composite. The morphological analysis showed nanoflower-like structures of the particles with an increased surface area in the plasma-treated composites. The plasma oxidation and sputtering effects caused a reduction in the nanoflower size. The energy bandgap increased with a decrease in particle size due to plasma treatment. The rhodamine B dye solution was then irradiated with a light source in the presence of the nanocomposites. The dye degradation efficiency of the composite photocatalyst increased from 80 to 96% after plasma treatment.

Crystal Structure and Molten Salt Environment Cooperatively Controlling the Morphology of the Plate-like CaMnO3 Template through Topochemical Conversion

In the field of oxide thermoelectrics, perovskite CaMnO3 ceramics have drawn plenty of attention due to their chemical stability, low cost, and environmental friendliness. By employing Ruddlesden-Poppe phase Ca3Mn2O7 as a precursor, the plate-like CaMnO3 microcrystals were successfully synthesized by the molten salt method combined with topochemical microcrystal conversion (TMC). The plate-like morphology of CaMnO3 was coordinately optimized by modulating the crystal structure of MnO2 and the molten salt environment. Plate-like microcrystals with an average size of ∼14.55 μm and a thickness of ∼2.89 μm were obtained by TMC reaction, demonstrating an obvious anisotropy. When β-MnO2 was used as the raw material, a length-thickness ratio of 4.77 was obtained, which was attributed to the fact that CaMnO3 inherited the plate-like morphology of the Ca3Mn2O7 precursor during the TMC. The results confirm that the plate-like CaMnO3 microcrystals with obvious anisotropy can provide excellent template seeds for high-quality CaMnO3-based textured ceramics.

Simultaneous improvement of polarization and bandgap by finite solid solution engineering

A narrow-bandgap-induced potential field always results in decreased photovoltaic performance. Here, a finite solid solution was designed to explore the simultaneous improvement of the polarization property and bandgap obtained from the critical effect in which BiMnO3 (BM) enters the Na0.5Bi0.5TiO3 (NBT) crystal lattice, resulting in a strong lattice expansion; by contrast, the incorporation of Mn without a d-orbital weakened the orbital hybridization accompanied by Jahn-Teller (J-T) distortion to reduce the optical bandgap. A narrow bandgap of 2.90 eV and polarization of 65.9 μC cm-2 were achieved by finite solid solution engineering. The open-circuit voltage and the short-circuit current with a BM doping component of 0.04 reached as high as 1.1 V and 0.0132 mA cm-2, respectively. This work provides an optimized strategy for the mutual benefit of the polarization and bandgap by finite solid solution engineering.

Enhanced electrical and magnetic functionality of Ni-Zn-co-doped CoFe2O4 rGO nanocomposites

Enhancement in electrical and magnetic functionalities of rGO CoFe2O4 and Co0.7Zn0.3Fe1.7Ni0.3O4 nanocomposites was identified compared to their spinel-type metal oxides. Moreover, changes in morphology that occurred during the formation of the composites were fabricated via a simple in situ hydrothermal route. Electron microscopic investigations confirmed that the microspheres of the metal oxides were constructed by porous nanolamellae comprising nanoparticles interconnected to form highly stable porous microspheres. Conversely, in rGO-CoFe2O4 and rGO-Co0.7Zn0.3Fe1.7Ni0.3O4 composites, distorted spinel-type metal oxide spheres on rGO sheets were observed. Frequency-dependent conductivity increased with an increase in temperature, obeying Jonscher's power law and Koop's phenomenological theory. The resistance of ferrites decreased from ∼1.4 MΩ to 30 KΩ for their respective rGO-based nanocomposites. The hysteresis curves of all the compounds showed them to be isotropic, soft ferrimagnetic in nature. Furthermore, a 30-50% enhancement in the values of magnetic parameters of the ferrites occurred when they were interfaced with rGO sheets. This enhancement was probably due to the interfacial interaction of rGO with ferrites. Such enhancement may afford an advancement in the potential applications of these nanocomposites.

Tunable particle-agglomeration and magnetic coupling in bi-magnetic nanocomposites

A set of non-stoichiometric Zn-Co-ferrite nanoparticles (NPs) was prepared by thermal decomposition of metallic complexes, in the presence of oleic acid, and, after a ligand-exchange process, was coated by a hydrophilic surfactant: these NPs were used as seeds in a sol-gel self-combustion synthesis to prepare nanocomposites (NCs) with a fixed weight ratio. Our focus here is the development of an efficient synthetic approach to control the magnetic coupling between a hard-magnetic matrix (Sr-ferrite) and NPs. The physico-chemical synthetic conditions (temperature, pH, colloidal stability) were optimized in order to tune their effect on the final particles' agglomeration in the matrix. We demonstrate that our synthetic approach is a novel way to produce strongly magnetically coupled NCs, where the final extrinsic properties could be tuned by controlling (i) the agglomeration of seeds in the matrix and (ii) their elemental doping.

Improvement of leakage, magnetic and magnetodielectric properties in cobalt doped gallium ferrite

Gallium ferrite (GFO) is a magnetoelectric (ME) material, capturing growing attention due to its strong ME coupling at room temperature. However, the application of the material in practical use is hindered due to its high leakage. In this work, the effects of cobalt (Co) substitution at the iron (Fe) sites of GaFe1-xCoxO3(0.0 ⩽x⩽ 0.1) polycrystals on the structure, electric and magnetic properties are investigated in detail. 5 at. wt.% substitution (x= 0.05) with cobalt ions achieves a reduction in leakage current density by four orders of magnitude due to reduced hopping between Fe3+and Fe2+ions and suppression of the oxygen vacancy formation. This is supported by higher dielectric constant and lower dielectric loss, as well as a significant difference between grain and grain boundary resistances. Two-phase-like magnetic behavior in magnetic hysteresis loop with enhanced magnetization and two magnetic transition temperatures are observed in the doped samples. All samples exhibited an increase in the magnetodielectric factor, indicating enhanced coupling between magnetic and electrical parameters. By concurrently increasing dielectric, magnetic, and coupling between them, this study describes a viable technique for lowering the most significant impediment to GFO's usage as a ME device.

Effect of High-Entropy Spinel Ferrite (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4 Doping Concentration on the Ferroelectric Properties of PVDF-Based Polymers

Polyvinylidene fluoride (PVDF)-based dielectric energy storage materials have the advantages of environmental friendliness, high power density, high operating voltage, flexibility, and being light weight, and have enormous research value in the energy, aerospace, environmental protection, and medical fields. To investigate the magnetic field and the effect of high-entropy spinel ferrite (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ nanofibers (NFs) on the structural, dielectric, and energy storage properties of PVDF-based polymers, (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ NFs were prepared via the use of electrostatic spinning methods, and (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄/PVDF composite films were prepared via the use of the coating method. The effects of a 0.8 T parallel magnetic field, induced for 3 min, and the content of high-entropy spinel ferrite on the relevant electrical properties of the composite films are discussed. The experimental results show that, structurally, the magnetic field treatment causes the originally agglomerated nanofibers in the PVDF polymer matrix to form a linear fiber chain with different fiber chains parallel to each other along the magnetic field direction. Electrically, the introduction of the magnetic field enhanced the interfacial polarization, and the (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄/PVDF composite film with a doping concentration of 10 vol% had a maximum dielectric constant of 13.9, as well as a low energy loss of 0.068. The high-entropy spinel ferrite (Mn_0.2Zr_0.2Cu_0.2Ca_0.2Ni_0.2)Fe₂O₄ NFs and the magnetic field influenced the phase composition of the PVDF-based polymer. The α-phase and γ-phase of the cohybrid-phase B1 vol% composite films had a maximum discharge energy density of 4.85 J/cm³ and a charge/discharge efficiency of 43%.

Nickel Slag/Laterite Soil and Nickel Slag/Iron Sand Nanocomposites: Structural, Optical, and Electromagnetic Absorption Properties

Efforts to produce microwave absorber materials that are inexpensive and environmentally friendly have become a means of greening the environment. The breakthrough can be focused on industrial waste and natural materials for functional purposes and how to enhance their performance. We successfully synthesized nickel slag/laterite soil (NS/LS) and nickel slag/iron sand (NS/IS) nanocomposites using a simple mechanical alloying technique, and the electromagnetic (EM) wave absorption capacities of the nanocomposites were measured using a vector network analyzer. The structural properties of the nanocomposites were analyzed by X-ray diffraction spectroscopy, where the results of the analysis showed that NS/IS has the largest crystallite size (15.69 nm) and the highest EM wave absorption performance. The optical properties of the nanocomposites were determined from their Fourier transform infrared spectra using the Kramers-Kronig relation. As determined through a quantitative analysis of the optical properties, the distance between the longitudinal and transversal optical phonon wavenumber positions (Δ(LO - TO) = 65 cm^-1) is inversely proportional to the reflection loss. The surface morphologies of the nanocomposites were analyzed by scanning electron microscopy, and the particle diameters were observed by binary image and Gaussian distribution analyses. The nanocomposite surface exhibits a graded-like morphology, which indicates multiple reflections of the EM radiation, consequently reducing the EM interference. The best nanocomposite for an attenuated EM wave achieved a reflection loss of -39.14 dB at 5-8 GHz. A low penetration depth has implications for the electrical charge tuning of the storage and composite magnets. Finally, the EM absorption properties of NS/IS and NS/LS indicate a 2-mm-thick environmentally friendly nanocomposite for EM absorption.

A thorough Investigation of Rare-Earth Dy3+ Substituted Cobalt-Chromium Ferrite and Its Magnetoelectric Nanocomposite

The stoichiometric compositions of a ferrite system with a chemical formula CoCr_0.5Dy_xFe_1.5-xO₄ where x = 0.0, 0.025, 0.05, 0.075 and 0.1 were prepared by the sol-gel auto-combustion method. The structural, morphological and magnetic properties were studied by the X-ray diffraction (XRD), infra-red spectroscopy (IR), scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. XRD analysis confirmed the cubic spinel structure of the prepared samples without the presence of any impurity and secondary phases. Selected area electron diffraction and IR measurements gives further confirmation to the XRD observations. Considering that strain mechanism, elastic properties and cation distribution play a major role for controlling the magnetic properties and therefore these properties were precisely evaluated through reliable methodologies such as XRD and IR data. The cation distribution was determined by the X-ray diffraction data which are further supported by the magnetization studies. Magnetoelectric properties of CoCr_0.5Dy_xFe_1.5-xO₄ + BaTiO₃ have also been investigated. The mechanisms involved are discussed in the manuscript.

Colorimetric assay of phosphate using a multicopper laccase-like nanozyme

A new nanozyme (Cu-NADH) is reported composed of Cu-coordinated nicotinamide adenine dinucleotide (NADH) exhibiting laccase-like activity. The Cu-NADH nanozyme had higher heat tolerance and catalytic efficiency than natural laccase, and its catalytic activity can be enhanced by high concentration of Cl ions and it is intensely inhibited by phosphate. Therefore, a colorimetric method based on Cu-NADH and indigo carmine was successfully developed to detect phosphate in water. This method showed an excellent selectivity for phosphate, and it had a linear relationship in the phosphate concentration range 2-50 μM with a detection limit of 0.37 μM. We believe that this example of coordination between metal ions and biomolecules to mimic natural enzymes can inspire more effective and alternative strategies in nanozyme design and expand their use in sensing and determination.