Structural, Dielectric, Magnetic and Magneto-Dielectric Properties of (1-x)BiFeO3–(x)CaTiO3 Composites

(1-x) BiFeO3–(x) CaTiO3 [(1-x) BFO – (x) CTO, (x = 0, 0.1, 0.2 and 0.3)] composites were synthesized using sol-gel chemical rout method. X-ray diffraction investigation shows the crystal structure changes from rhombohedral to monoclinic for 0 ≤ x ≤ 0.2, and it changes to orthorhombic at x ≤ 0.3. The Field Emission Scanning Electron Microscope (FESEM) investigation confirms the the microstructure consists of randomly oriented, homogenous, and non-uniform grains. The dielectric permittivity (ε) and tangent loss (tanδ) decreases with increasing frequency and show dielectric anomalies (as a hump) at different temperatures for different compositions. The incorporation of CTO, decreases three order of leakage current (up to x = 0.2) and significantly improve the magnetization and magneto-dielectric coupling. The frequency-dependent ac conductivity obeys Jonscher’s power law with large ac conductivity dispersion for higher frequencies with increasing CTO concentration. The variations of ac conductivity with the inverse of temperature obey the Arrhenius equation and show negative temperature coefficient of resistance (NTCR) behavior. The ferromagnetic (FM) properties in BFO-CTO increases significantly with an increase of the CTO concentration. The coercive field increases with increasing CTO concentration suggesting a competition between the antiferromagnetic and ferromagnetic ordering. At room temperature, all the samples show strong magneto-dielectric coupling.

Enhanced electrical conductivity in Zr-Doped (La0.7Ba0.3)(Mn0.5Fe0.5)O3 solid solutions

The perovskite ([Formula: see text][Formula: see text]([Formula: see text][Formula: see text][Formula: see text]O3, where [Formula: see text] = 0.1, 0.2 and 0.3, ceramics were synthesized by solid-state reaction method. The introductory structural studies were followed through by X-ray diffraction technique and the results have disclosed that all the samples were crystallized into an isolated phase. The Zr substitution in the resulting solid solutions increases the electrical conductivity and the maximum value of ac conductivity has been found to be [Formula: see text]118.8 S [Formula: see text] cm[Formula: see text] for [Formula: see text] = 0.3 at 200[Formula: see text]C (at 1 MHz). The frequency dependence of ac conductivity data follows Jonscher’s power law. The variation of the exponent [Formula: see text] versus temperature follows the nonoverlapping small polaron tunneling (NSPT) model. The dielectric relaxation has been observed to be of non-Debye nature for all measuring temperatures (50–200[Formula: see text]C). The impedance spectroscopy reveals that all the samples exhibit negative temperature coefficient of resistance (NTCR) behavior. The prepared samples (for [Formula: see text] > 1) are supposed to be suitable for cathode materials in SOFCs.

Conductivity, Dielectric and Modulus study of NH4PF6 based Zwitterionic polymer electrolyte

Background and Objective: Zwitterionic polymer electrolyte has been successfully synthesized using NH4PF6 salt. The conductivity of the synthesized polymer membrane is found to be of the order of 10-3Scm-1. Dielectric and Modulus properties of the polymer electrolyte have also been studied which showed well relaxation peaks with both temperature and salt concentrations. Result: This is well depicted with the loss tangent curve. Debye type relaxation behavior has observed from the electric modulus. Conclusion: Frequency dependent conductivity data (fitted with Jonscher's power law equation) confirmed the presence of NCL/SLPL type behavior in the studied frequency range.

Room Temperature Magnetoelectric Coupling, Electrical, and Optical Properties of BaFe2O4 – ZnO Nanocomposites

Polycrystalline multiferroic nanocomposites with general formula xBaFe2O4 – (1 – x) ZnO (x = 0.2, 0.3, and 0.5) are prepared by chemical pyrophoric reaction method and solid-state route. The samples are characterized by X-ray diffraction which indicates the formation of both the phases in the composites. The morphological analysis and elemental compositions have been identified by using field emission scanning electron microscope and energy-dispersive X-ray analysis techniques. These micrographs reveal the particle sizes are in the nanometer dimension. The band gap of the nanocomposites is estimated employing UV-Vis spectroscopy. The DC electrical resistivity exhibits a metal-semiconductor transition for all the nanocompositions. Temperature-dependent AC conductivity of the nanocomposites is found to obey the Jonscher’s power law. The room temperature multiferroic behavior of the nanocomposites is confirmed from the detailed magnetoelectric response studies. The coupling coefficient is obtained maximum for x = 0.5 compositions for both in transverse and longitudinal mode due to the more ferrite content i.e., more magnetostrictive behaviour in the nanocompositions.

Electrical properties of 0–3 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.2Ti0.8)O3/PVDF nanocomposites

Lead-free [Formula: see text](0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text]-([Formula: see text]PVDF ceramic–polymer nanocomposites with [Formula: see text], 0.05, 0.10, 0.15, 0.20, 0.25 were prepared using melt-mixing technique. The distribution of nanoceramic filler particles (0.50(Ba[Formula: see text]Ca[Formula: see text]TiO3–0.50Ba(Zr[Formula: see text]Ti[Formula: see text]O[Formula: see text] in the PVDF matrix were examined using scanning electron microscope. Impedance analysis indicated the negative temperature coefficient of resistance character of all the test specimens. Filler concentration-dependent piezoelectric coefficient ([Formula: see text] data followed exponential growth types of variation. The data for ac conductivity were found to obey Jonscher’s power law. The correlated barrier hopping (CBH) model was found to explain the mechanism of charge transport occurring in the system. The low value of loss tangent ([Formula: see text]) along with the high value of [Formula: see text] foreshadowing the prospect of present nanocomposite is a better nonlead option for piezo-sensing/detection applications, especially in bio-medical area.

Dielectric and conducting behavior of gadolinium–terbium fumarate heptahydrate crystals

Gadolinium–terbium fumarate heptahydrate crystals were grown in silica gel by using single gel diffusion technique. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction results showed that the grown material is purely crystalline in nature. Elemental analyses suggested the chemical formula of the compound to be Gd Tb [Formula: see text]. Energy dispersive X-ray analysis confirmed the presence of Gd and Tb in the title compound. The dielectric and conductivity studies of the grown compound were carried as function of frequency of applied field and the temperature. The grown material showed a dielectric anomaly which was correlated with its thermal behavior. The ac conductivity of the material showed Jonscher's power law behavior: [Formula: see text], with a temperature-dependent power exponent [Formula: see text]. The conductivity was found to be a function of temperature and frequency.

Graphene–Epoxy Composites with High Dielectric Constant Prepared by Cryomilling

The microstructure and dielectric properties of the graphene–epoxy composites prepared by cryomilling at liquid nitrogen temperature were studied by SEM and RF impedance material analyzer. The result indicated that both the dielectric constant and conductivity of the composites increased with the increase of the graphene content. The value of the dielectric constant of the composite with about 8 wt % of graphene was as high as 200. Moreover, the frequency dispersion behaviors of the conductivity within a certain frequency range accorded with the Jonscher's power law demonstrating that the conductive mechanism is hopping conduction. The negative reactance decreased with the increase of the testing frequency which indicated a capacitive character

EFFECT OF BARIUM ON DIELECTRIC, FERROELECTRIC, IMPEDANCE AND ELECTRICAL MODULUS PROPERTIES OF Bi0.5Na0.5TiO3 CERAMICS

Perovskite structured ferroelectric ( Na 1/2 Bi 1/2)0.945 Ba 0.055 TiO 3 (BNBT-5.5) material has been synthesized by the conventional sintering technique. X-ray analysis on the material showed a single phase compound with rhombohedral structure with lattice parameters a = 3.89 Åand α = 89.893 Å. Frequency and temperature dependence of dielectric permittivity, impedance, modulus and conductivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595°C, respectively. The observed low frequency dielectric dispersion (LFDD) in the material could be explained by Jonschers power law and evaluated activation energies at different temperature regions. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.