C. Behera

Development of Multiferroism in PVDF with CoFe2O4 Nanoparticles

Thin films of some polymer-ceramic nanomultiferroic composites (in 0–3 connectivity) of compositions (1-x) PVDF-xCoFe2O4 (x = 0.05, 0.1, 0.5) have been fabricated through a solution casting route. Based on X-ray diffraction pattern and data, basic crystal structure and unit cell parameters were obtained. The surface morphology of the materials was studied using a scanning electron microscopy (SEM) technique. Structural investigation confirms the presence of a polymeric electro-active β-phase of matrix (PVDF) and nano filler spinel phase of the incorporated nano-ceramics. The observed SEM micrographs confirm that the nanoparticles are well distributed in the PVDF matrix without any agglomeration with a lesser spherulitic microstructure. The flexible nano-composites fabricated with polymer (PVDF) and CoFe2O4 provide high permittivity (relative dielectric constant) and low loss tangent. An impedance spectroscopy (IS) technique was employed to study the effect of grain and grain boundary in the resistive properties of the composite materials in terms of electric circuit. The study of AC conductivity as a function of frequency follows Jonscher’s power law. The improved conductivity and dielectric, magnetic, and measured first-order magnetoelectric coefficients suggest some promising applications in the embedded capacitors as well as in multifunctional devices.

Structural, dielectric, impedance and magneto-electric properties of mechanically synthesized (Bi0.5Ba0.25Sr0.25) (Fe0.5Ti0.5)O3 nano- electronic system

Structural, electrical, magnetic and magneto-electric properties of (Bi0.5Ba0.25Sr0.25) (Fe0.5Ti0.5) O3 nanoceramic synthesized by the mechanical alloying method were studied. Structural analysis was studied by Rietveld refinement of room temperature XRD data. The temperature and frequency dependent dielectric data were explained using the different mechanism. The grain and grain boundary effect of the material on the electrical properties has been explained using the existed mechanism. The impedance study reveals a semi conducting grain and insulating grain boundary resulting in the formation of surface and internal barrier layer capacitors leading to the high value of dielectric constant. The frequency dependence of AC conductivity at two different regions can be explained on the basis of correlated barrier Hopping model and quantum mechanical tunneling model. The value of the magneto-electric voltage coupling coefficient, α, of (Bi0.5Ba0.25Sr0.25) (Fe0.5Ti0.5)O3 ceramic is obtained as 2.56 mV cm−1 Oe−1.

Structural and dielectric studies of Bi (Ni0.45Ti0.45Fe0.10) O3 ceramics

In the present investigation, a solid solution of BiFeO3 and NiTiO3 i.e., Bi(Ni0.45Ti0.45Fe0.10)O3 (abbreviation is BNTF) have been synthesized using a solid-state reaction technique. Structural and dielectric properties of BNTF ceramics have been studied in details to understand their properties. Preliminary X-ray diffraction analysis confirm the formation of a new system, which is different from that of its parent compounds. Substitution of a small amount of NiTiO3 into BiFeO3 enhances dielectric and ferroelectric properties, and reduces electrical leakage current or tangent loss. It was shown by XRD that at room temperature structure of the compound is of single-phase with tetragonal symmetry. Some electrical characteristics (dielectric constant and loss) studied over a wide frequency (1 kHz–1 MHz) and temperature (25–400°C) ranges have provided many more interesting information useful for devices.