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In the present study, we report a significant magnetoelectric coupling in lead-free (1-x)Ba0.95Ca0.05Ti0.95Sn0.05O3 - (x)Ni0.7Zn0.3Fe2O4 (x = 0.10, 0.15, 0.20, 0.25 and 0.30) particulate composites prepared by solid-state route. Phase purity and crystal structure of the composites were examined by the X-ray diffraction measurement. With the incorporation of the magnetic NZFO phase, a decrease in the tetragonality of the ferroelectric BTCS lattice was confirmed by the full pattern match of the XRD data using Rietveld analysis. FESEM micrographs revealed improved microstructures with the addition of ferrite concentrations in the composites. Simultaneous presence of ferroic orders in the composites was confirmed from the room-temperature P-E and M-H hysteresis loops. Direct magnetoelectric voltage measurement of the composites established the strain-mediated coupling between the BTCS and NZFO phases. Highest RT first-order magnetoelectric voltage coefficient (α/d = 6.24 mV/cm-Oe) of the x = 0.25 composite is attributed to better individual ferroic properties and improved microstructure of this sample. [ABSTRACT FROM AUTHOR]

We report the effect of Co3+-Ti4+ doped SrFe12-(x–y)CoxTiyO19 (x = y = 0.0, x = 0.225, y = 0.1125) hexaferrite successfully prepared using the conventional ceramic route. The structural, optical, electrical, and magnetic properties were analyzed via X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, complex impedance spectroscopy, and vibrating sample magnetometer. The structural analysis (Rietveld Refinement) revealed that all the samples exhibit magnetoplumbite hexagonal crystal structures with P63/mmc space group. At the same time, their increase in grain size and the bandgap energy showed evidence of dependency on Co3+-Ti4+ content in SrFe12O19. The impedance and modulus spectra showed the suppression of surface charge polarization with substituting Co3+-Ti4+ ions and co-contribution of the grain and grain boundary effect presented by modeling the electrical processes using an equivalent circuit model. Two transition peaks were observed in the temperature-dependent dielectric constant plots, represented as Td and Tm. However, Tm is nearly frequency-independent, and only one transition peak is identified in frequency versus dielectric constant plots. The temperature Td is due to dipole relaxation, whereas Tm is assigned as dielectric phase transition, modeled by modified Curie–Weiss law. Further, the AC conductivity was examined by Jonscher’s powder law and random free energy barrier model, showing that the AC conductivity increases by increasing frequency due to electronic and overlapping large-polaron hopping mechanisms. Finally, in the magnetic measurements, a simple phenomenological model was modeled based on the Lorentzian function model, representing a transition from hard to soft ferrites in the doped Co3+-Ti4+ SrFe12O19 with saturation magnetization of 123.66 emu/g and coercivity of 316.69 Oe. [ABSTRACT FROM AUTHOR]

In this work, effect of sintering temperature on magnetoelectric properties of lead-free [85 wt% Ba0.95Ca0.05Ti0.95Sn0.05O3 (BTCS)–15 wt% Ni0.7Zn0.3Fe2O4 (NZFO)] particulate composite has been studied. The composites were synthesized by solid-state reaction method and sintered at five different temperatures. Structure analysis of constituent phases of the composites has been examined by X-ray diffraction (XRD) technique. Rietveld refinement confirmed that the piezoelectric BTCS comprised two phases (tetragonal and orthorhombic) and inverse spinal NZFO has a cubic phase in the composites. Surface morphology study carried out by Field Emission Scanning Electron Microscope (FESEM) accounted the increase in uniform grain size and connectivity of the constituent phases with the increase of sintering temperature. Dielectric constant vs. temperature (Ɛr–T) graph showed two anomalies corresponding to the ferroelectric transition temperature of BTCS and the magnetic transition temperature of NZFO phase. Enhancement in saturation polarization (PS) and decrease in saturation magnetization (MS) at room temperature were observed with the increase of sintering temperature. The composite, sintered at 1300 °C for 4 h showed maximum change in magnetodielectric value (MD% ∼ 1.94 at 100 kHz frequency) at room temperature. This sample also exhibited the highest first and second order magnetoelectric coefficients (α/d = 2.37 mV/cm-Oe and β/d = 40.69 µV/cm-Oe2) at room temperature which was explained on the basis of sintering temperature-dependent ferroic properties of the individual phases. [ABSTRACT FROM AUTHOR]

We investigated the anomalous behaviour in the dielectric properties, occurring nearly at room temperature and at elevated temperatures (near the Neel temperature TN) of the polycrystalline samples of YFeO3 (YFO) ceramics. On the prepared YFO ceramics, the magnetic measurements showed the Neel temperature of YFO to be 650 K, below which the compound exhibited the weak ferromagnetic behaviour. X-ray photoelectron spectroscopy (XPS) shows the presence of Fe ions (Fe2+ and Fe3+ states) and also revealed the formation of the oxygen vacancies. The frequency dependence of the complex dielectric constant within the frequency domain of 100 Hz–1 MHz shows the presence of grain dominated dielectric relaxation over the thermal window of 300–373 K. The activation energy E act. ε = 0.611 eV extracted from the imaginary permittivity spectrum indicates the involvement of oxygen vacancies in the relaxation process. Above 493 K, the ac conductivity, complex impedance, and modulus studies revealed appreciable conduction and relaxation processes occurring in YFO ceramics with respective activation energies E a c t. σ = 1.362 eV and E a c t. Z = 1.345 eV , which suggests that the oxygen vacancies are also involved for the anomalous behaviour of the dielectric constant at elevated temperatures. The temperature dependent Raman spectroscopic measurements within the thermal window of 298–698 K showed anomalous variations of the line widths and frequencies of several Raman active modes above 473 K up to the vicinity of TN pointing towards the presence of admixtures of the electron-phonon and spin-phonon coupling in the system. A further study on the thermal variation of the B2g(4) mode frequency with [M(T)/MS]2 shows the occurrence of strong spin–phonon (s-p) coupling, while the line shape shows the presence of the Fano asymmetry, suggesting spin dependent electron-phonon (e-p) coupling in the system below TN. [ABSTRACT FROM AUTHOR]

Polycrystalline (100 − x)BaFe12O19(BaM) − (x)Na0.5Bi0.5TiO3 (NBT) [x in wt% = 10, 20, 30, and 40] magnetoelectric composite systems have been synthesized by solid-state reaction method. The formation of the desired composite systems has been verified by X-ray diffraction. The SEM images have been provided the information about grain size and connectivity of both the phases. Magnetic and magnetoimpedance (MI) studies have been taken at room temperature. From magnetic results it is found that coercive field (Hc) is drastically decreased for composite systems. From the MI study, it is perceived that the spin-polarized electron tunneling at FM–FE interfaces is strongly dependent on the grain size and connectivity of both the phases. [ABSTRACT FROM PUBLISHER]

In this report, we present the structural, electrical, and optical study of layer-structured SrBiTiO (SBT) ceramic prepared by solid-state reaction route. The X-ray diffraction and Rietveld refinement studies show a single-phase orthorhombic structure with space group Aam. The scanning electron micrograph shows plate-like grains. The various Raman peaks originated due to the TiO octahedron confirm the orthorhombic structure. The temperature-dependent dielectric study shows a normal ferroelectric phase transition with a transition temperature at 813 K (540 °C). Impedance studies show a non-Debye-type relaxation and relaxation frequency shift to higher side with increase in temperature. The Nyquist plot shows overlapping semicircles which results the existence of both for grain and grain boundary effect in SBT ceramic. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated and the spectra follow the universal power law. The variation of DC conductivity confirms that the SBT ceramic exhibits negative temperature coefficient of resistance behavior. The Ferroelectric behavior is studied by hysteresis loop. The optical band gap is found to be 2.93 eV from the UV-Visible spectroscopy study. The room-temperature photoluminescence study shows a strong red emission. [ABSTRACT FROM AUTHOR]

This paper reports the monolayer characteristics of cationic octadecylamine (ODA) on both distilled water and aqueous Erythrosine B (EB) dye solution at the air-water interface. From the pressure-area isotherms at various pHs, EB anions in the subphase were found to interact with the insoluble monolayer of cationic octadecylamine (ODA). Adsorption kinetics shows that the amount of dye adsorbed depends on the concentration of the dye present in the subphase. It was observed that the adsorption process mainly occurred due to the electrostatic interaction between the cationic amino group of long chain amine and the anionic part of EB. The spectroscopic characteristics of the mixed LB films, solution, have been compared using UV-vis absorption and fluorescence spectroscopic data. These studies indicate the formation of aggregates in the thin films. Scanning electron microscopic study certainly confirms the presence of aggregates of EB dye in the (ODA-EB) mixed LB films. [ABSTRACT FROM PUBLISHER]

Nonamphiphilic 2-aminoanthracene has been incorporated within the Langmuir monolayer and Langmuir–Blodgett (LB) films when mixed with behenic acid (BA). Miscibility of 2-aminoanthracene and BA at the air—water (A–W) interface has been studied by using surface phase rule and excess area criterion. Our studies reveal that repulsive type interactions exist between the component molecules in mixed monolayer and this may facilitate the formation of aggregates. Spectroscopic as well as morphological studies of mixed LB films of 2-aminoanthracene and BA undoubtedly confirms the formation of aggregates. [ABSTRACT FROM PUBLISHER]

Mixed films of a polycylic aromatic hydrocarbon 1-pyrene-carboxaldehyde (PyCHO) and a polymer matrix, viz. isotactic poly(methyl methacrylate) (PMMA) were studied at the air–water interface by surface pressure versus area per molecule (π-A) isotherms. The diagrams obtained by plotting the mean area per molecule as a function of the molar fraction of PyCHO showed positive deviations from ideal conditions with a small exception indicating a repulsive type of interaction between PyCHO and PMMA molecules, resulting in the formation of aggregates. Spectroscopic as well as scanning electron microscopy (SEM) studies revealed that aggregates were present when the mixed film was transferred onto quartz substrates at different mole ratios of PyCHO. [ABSTRACT FROM AUTHOR]

Formation of complex monolayers between a dichain cationic surfactant, namely, dihexadecyldimethylammonium bromide (DHDAB) and deoxyribonucleic acid (DNA) at the air-water interface was first time systematically investigated here. The adsorption of DNA onto DHDAB monolayer was monitored by observing the surface pressure vs. time graph. The polyion-complex monolayers formed in situ through the electrostatic attraction between cationic DHDAB and the phosphate groups of anionic DNA. The organization of the DNA-DHDAB complex at the air-water interface deduced from surface pressure-area (π-A) isotherms was compared with the spectroscopic data in Langmuir-Blodgett films. Study of UV-Vis absorption spectra of pure DNA solution and DNA adsorbed DHDAB complex Langmuir-Blodgett films confirms the successful transfer of the films onto quartz substrates. [ABSTRACT FROM PUBLISHER]

This paper reports the incorporation of an inhibitor of Human Immunodeficiency Virus (HIV), viz. Chicago Sky Blue (CSB) dye within an insoluble cationic octadecylamine (ODA) Langmuir monolayer. A surface pressure-area isotherm study confirmed the strong interaction between long chain amine and CSB dye. At higher surface pressure, CSB molecules tend to squeeze out from the octadecylamine monolayer. SEM study confirms this observation. Adsorption kinetics shows that the amount of dye adsorbed depends on the concentration of the dye present in the subphase. It was observed that the absorption process mainly occurred due to the electrostatic interaction between the cationic amino group of long chain amine and the sulphonate group of CSB dye. UV-Vis absorption spectroscopic study indicates the formation of aggregates of CSB dye in the mixed (ODA-CSB) LB films. [ABSTRACT FROM AUTHOR]

Ferroelectrics and high temperature superconductors are two promising materials for future electronic devices. Both being perovskite ceramic structures with similar crystal chemistry a set of samples were prepared from the composite of (1− x)YBa2Cu307− δ −( x)BaTiO3 (YBCO/BT). These samples were investigated with temperature dependent resistance, FTIR, X-ray diffraction and SEM-EDX analysis. It has been found that the critical exponent in the T c0 ( R = 0) region is in agreement with the percolation theory. A long-range superconducting order results from thermally assisted percolation process through weak-links between the grains. The connectivity in the coherent transition region can be explained by a power law. [ABSTRACT FROM AUTHOR]

In this work, BaFe12O19 (BaM) and its modified systems (by substitution of Ni and Ti) have been synthesized by solid-state reaction method. From Rietveld refinement of X-ray diffraction pattern, it is found that volume of unit cell increased slightly in case of modified systems. SEM images provided the information about the microstructure of BaM and its modified systems. The electric, magnetic and optical properties have been carried out with the help of complex impedance spectroscopy, VSM and UV spectrum, respectively. From electrical analysis, it is perceived that Ni-substitution system has shown co-contribution of grain and grain boundary effect due to increases of grain size. The M-H loops are explored that, with substitution of Ni and Ti both Ms and Hc are decreased. From the variation of band gap (Eg), it is observed that Eg has been significantly decreased with substitution (least for Ni-substitution). [ABSTRACT FROM AUTHOR]

In this report, we present the electrical and optical properties of four-layered perovskite ferroelectric A Bi 4 Ti 4 O 15 (with A  = Sr, Ba, Ca), prepared by solid-state reaction route. The X-ray diffraction study asserts single-phase orthorhombic structure with A2 1 am space group. Scanning electron microscopy observation shows plate-like grains in all the samples. Notably orthorhombic distortion (b/a) decreases with increase in ionic radius of A- site cation, which was explained by tolerance factor. Additionally, good ferroelectric, piezoelectric, optical and thermal stability obtained in SBT system. [ABSTRACT FROM AUTHOR]

We report improved electrical properties in Sr 1−x Gd 2x/3 Bi 4 Ti 4 O 15 (SGBT-x, 0 ≤ x ≤ 0.1) ceramics prepared by solid state reaction route. The X-ray diffraction pattern suggested that the substitution lead to the formation of layered structure. Plate-like morphologies with decreasing grain size were clearly observed for all the samples. The temperature dependent dielectric analysis reveals that dielectric constant increases with increasing Gd 3+ content up to x ≤ 0.08. Even excellent electrical properties (e.g., piezoelectric constant (d 33 ) ∼19 pC/N, remanent polarization (2P r ) ∼0.38 µC/cm 2 and Curie temperature (T C ) ∼550 °C) are simultaneously obtained in the ceramic with x = 0.08. Additionally, thermal annealing studies indicated that the piezoelectric constant (d 33 ) of the SGBT ceramics remains almost unchanged up to the transition temperature in all compositions. [ABSTRACT FROM AUTHOR]

Polycrystalline (1-x) Na 0.5 Bi 0.5 TiO 3 – (x) BaFe 12 O 19 [x in wt% = 10, 20, 30 and 40] novel magnetoelectric composites are synthesized by solid state reaction method. The formation of composites is confirmed by Rietveld refinements of XRD patterns. The connectivity of both phases and grain size are verified from SEM images. Room temperature (RT) multiferroism has been verified by PE loop, MH loop, magnetocapacitance (MC%) and magnetoloss (ML%) studies. From results it is found that, P s and P r increases with BaM wt% up to certain wt% and then decreases, however, M s increases & H c decreases continuously. Highest MC% and ML% are observed in S1(NBT90). From analysis it is perceived that, connectivity of BaM-BaM & BaM-NBT interfaces have significant role on multiferroic behaviour. [ABSTRACT FROM AUTHOR]