Basharat Want

Dielectric, ferroelectric and magnetic behavior of BaTiO3–BaFe12O19 composite

BaTiO3–BaFe12O19 composite was prepared by solid state reaction method. Ferroelectric barium titanate and ferrimagnetic barium hexaferrite phases were prepared separately. From morphological studies, the distribution of barium titanate and barium hexaferrite grains was confirmed. The evaluation of densities showed that the composite is denser compared to the individual phases. The polarization versus electric field experiment showed typical hysteresis loops, confirming the presence ferroelectric phase in the composite. Dielectric studies carried on the composite samples showed a diffused type of ferroelectric phase transition. Various magnetic parameters of the composite system were studied and compared to the barium hexaferrite phase. The first order reversal curve method was used to confirm the presence of single and multidomain structures in barium hexaferrite and the composite system.

Electric, Magnetic, and Magnetoelectric Properties of Yttrium-Containing BaY 0.025 Ti 0.9625 O 3 –SrFe 12 O 19 Composite

The physical properties of BaY0.025Ti0.9625O3, SrFe12O19, and 0.90BaY0.025Ti0.9625O3–0.10 SrFe12O19 composite have been studied. The proposed composite was synthesized by solid-state reaction method from yttrium barium titanate processed by solid-state reaction and strontium hexaferrite obtained by a sol–gel process. Microstructural analysis revealed monophasic grains for yttrium barium titanate phase, while loosely packed biphasic structure was observed for the composite. Powder x-ray analysis showed that the individual phases retained their crystal structure in the composite, without formation of any new additional phase. Measurement of magnetic hysteresis loops at room temperature indicated that the magnetic parameters of the composite were diluted by the presence of the ferroelectric phase. The ferroelectric hysteresis of yttrium barium titanate confirmed the ferroelectric transition at 119°C. Meanwhile, the symmetrical ferroelectric loops observed at different fields established the ferroelectric nature of the composite. Improved dielectric properties and low dielectric losses were observed due to yttrium doping in the composite. The diffuseness of the ferroelectric transitions for the composite was confirmed by the Curie–Weiss law. Activation energy calculations revealed the charge-hopping conduction mechanism in the composite. Magnetodielectric studies confirmed that the overall magnetocapacitance in the composite exhibited combined effects of magnetoresistance and magnetoelectric coupling.

Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O]

We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C4H5O6)(C4H4O6)][3H2O]. X-ray crystal structure analyses reveal that it crystallizes in the P41212 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 A). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau– Devonshire phenomenological theory. In addition, the most recent ...

Structural, dielectric and ferroelectric properties of rare earth substituted lead zirconate titanate

Rare-earth (RE) metal (Pr, Yb, Sm) ions doped lead zirconate titanate (PZT) ceramics were synthesized by the sol–gel auto-combustion technique and characterized for their structural, morphological and ferroelectric properties. The results from X-ray diffraction analysis of all these samples confirmed the tetragonal phase and only in the case of Sm doped PZT, there is pyrochlore phase. The surface morphology revealed a decrease in grain size with the RE doping with the lowest value for Yb–PZT. From the dielectric studies, a high value of dielectric constant of 2 × 105 was observed for Yb–PZT and drop in Curie temperature was observed for Pr and Sm doped PZT. The low dielectric loss and an increase in coercivity were found for Pr doped PZT which may have potential applications in memory devices.

Infrared, Raman, electrical and thermal analysis of lithium sulphate monohydrate single crystals

In this work, single crystals of lithium sulphate monohydrate were grown by slow evaporation technique. Structural studies of the grown crystals were carried out by powder X-ray diffraction technique showing a monoclinic structure. Effect of temperature on the vibrational modes of different groups was observed and analyzed by Fourier transform infrared and Raman spectroscopy. The temperature dependent dielectric behaviour and ac conductivity of the grown crystals were also studied. The effect of temperature on the vibrational spectra as observed by Fourier transform infrared and Raman spectroscopy were correlated with the electrical behavior of the crystals. The relaxation studies were also undertaken using the complex-modulus M* formalism which showed a thermally activated relaxation caused by the hopping motion of H+ ions in the crystal. All the observed characteristics were found to be closely related with water loss in the crystal structure. Thermal analysis of the grown crystal was carried out by using differential scanning calorimetric technique yielding various thermodynamic parameters such as ΔH, ΔS and ΔCp. The activation energy for the dehydration step of lithium sulphate monohydrate was also evaluated by using Coats-Redfern integral method.

Optoelectrical Behavior of Ferroelectric Lithium Rubidium Sulfate Crystals

Single crystals of lithium rubidium sulfate with good transparency have been grown from aqueous solution by a slow evaporation technique. Single-crystal x-ray diffraction results revealed that, at room temperature, the crystal belongs to the monoclinic system in space group P21/n. From the transmittance and reflectance spectra, various optoelectrical constants such as the refractive index, extinction coefficient, optical bandgap for direct transition, optical conductivity, electronic polarizability, high-frequency dielectric constant, and optical electronegativity were calculated for the investigated lithium rubidium sulfate crystal. A correlation between the various optical parameters was also observed. The refractive index was fit to a three-term Cauchy dispersion relationship. The single-oscillator Wemple–DiDomenico model was applied to discuss the dispersion of the refractive index. The optical transmittance study revealed transparency of the crystal in the entire visible region with wide optical bandgap. The electronic polarizability values calculated from the Clausius–Mossotti equation and from bandgap analysis were found to be in good agreement.

Effect of Annealing Temperature on Different Physical Properties of Sr0.5la0.5Mg0.5Fe11.5o19 Hexaferrite

The influence of annealing on different physical properties of La0.5Mg0.5Sr0.5Fe11.5O19 hexaferrites prepared by the citrate-precursor method is presented in this study. The effects of temperature on the physical properties properties of the synthesized hexaferrites have been investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Miscroscopy (SEM) and Vibrating Sample Magnetometer (VSM). The XRD study shows the formation of hexagonal structure with grain size lying between 23.86 nm and 56.12 nm. FTIR was used to study functional groups associated with the material. A decrease in saturation magnetization (Ms), and increase in Coercivity (HC) is observed with increase in temperature. Also, anisotropy constant was calculated by using Law of Approach to saturation and is well agreement with the literature.

Dielectric and conducting behaviour of polycrystalline holmium octa-molybdate

Polycrystalline holmium octa-molybdate spherulites have been obtained by using gel diffusion technique and characterized by different physio-chemical techniques. The surfaces of these spherulites are composed of nano-rod with an average diameter of about 80 nm. At room temperature the initial crystal structure is triclinic, space group P1. Thermal studies suggested a phase transition occurring in holmium octa-molybdate crystals at about 793 K. The electrical properties of the system have been studied as a function of frequency and temperature in the ranges of 20 Hz–3 MHz and 290–570 K, respectively. A giant dielectric constant and two loss peaks have been observed in the permittivity formalism. The conducting behaviour of the material is also discussed. The conductivity was found to be 1572 μ Ω−1 m−1 at room temperature and 3 MHz frequency. The conductivity of the polycrystalline material was attributed to the fact that it arises due to the migration of defects on the oxygen sub-lattice. Impedance studies were also performed in the frequency domain to infer the bulk and grain boundary contributions to the overall electric response of the material. The electrical responses have been attributed to the grain, grain-boundary, and interfacial effects.