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Multiferroic composites with enhanced magneto-electric coefficient are suitable candidates for various multifunctional devices. Here, we chose a particulate composite, which is the combination of multiferroic (PbFe0.5Nb0.5O3, PFN) as matrix and magnetostrictive (Co0.6Zn0.4Fe1.7Mn0.3O4, CZFMO) material as the dispersive phase. The X-ray diffraction analysis confirmed the formation of the composite having both perovskite PFN and magnetostrictive CZFMO phases. The scanning electron micrograph (SEM) showed dispersion of the CZFMO phase in the matrix of the PFN phase. The temperature-dependent magnetization curves suggested the transition arising due to PFN and CZFMO phase. The temperature-dependent dielectric study revealed a second-order ferroelectric to the paraelectric phase transition of the PFN phase in the composite with a small change in the transition temperature as compared to pure PFN. The magnetocapacitance (MC%) and magnetoimpedance (MI%) values (obtained from the magneto-dielectric study at room temperature (RT)) at 10 kHz were found to be 0.18% and 0.17% respectively. The intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm-1Oe-1, which is comparable to other typical multiferroic composites in bulk form. The composite PFN-CZFMO exhibited a converse magneto-electric effect with a change in remanent magnetization value of -58.34% after electrical poling of the material. The obtained outcomes from the present study may be utilized in the understanding and development of new technologies of this composite for spintronics applications. [ABSTRACT FROM AUTHOR]

We report systematic studies on crystal structure and magneto-dielectric properties of (1-x) BiFeO3-x DyMnO3 (0.0⩽x⩽0.2) nanoceramics synthesized by auto-combustion method. Rietveld refinement of X-ray diffraction data indicates a structural transition from R3c to R3c + Pn21a at x=0.1. Field emission scanning electron micrographs display a decrease in grain size with increase in x. The presence of dielectric anomalies around antiferromagnetic transition temperature implies the magnetoelectric coupling. Dielectric measurements showed decrease in magnetic ordering temperature with increasing x in agreement with differential scanning calorimetry results. A significant increase in magnetization has been found with increasing DyMnO3 substitution. Magnetoimpedance spectroscopy reveals a significant change (∼18%) in dielectric permittivity at H=2T for x=0.2. [ABSTRACT FROM AUTHOR]

High-pressure synchrotron based angle dispersive x-ray diffraction (ADXRD) studies were carried out on SmGdO3 (SGO) up to 25.7 GPa at room temperature. ADXRD results indicated a reversible pressure-induced phase transition from ambient monoclinic to hexagonal phase at ∼8.9 GPa. The observed pressure-volume data were fitted with the third order Birch-Murnaghan equation of state yielding zero pressure bulk modulus Bo=132(22) and 177(9) GPa for monoclinic (B-type) and hexagonal (A-type) phases, respectively. Pressure dependent micro-Raman spectroscopy further confirmed the monoclinic to hexagonal phase transition at about 5.24 GPa. The mode Grüneisen parameters and pressure coefficients for different Raman modes corresponding to each individual phases of SGO were calculated using pressure dependent Raman mode analysis. [ABSTRACT FROM AUTHOR]

We report the crystal structure, dielectric, transport, and magnetic properties of Ni0.65Zn0.35Fe2O4. Rietveld refinement results of X-ray diffraction patterns confirm the phase formation of the material with cubic crystal structure (Fd3m). The frequency dependent ac conductivity behavior obeys the Jonscher's power law and is explained using the jump relaxation model. The observed behavior of temperature dependent bulk conductivity is attributed to the variable-range hopping of localized polarons. The correlation of polaron conduction and high permittivity behavior of NZFO is established on the basis of long range and short range conduction mechanisms. The complex impedance spectra clearly show the contribution of both grain and grain boundary effect on the electrical properties. [ABSTRACT FROM AUTHOR]

We report the crystal structure, magnetic, ferroelectric, dielectric, and magneto-dielectric properties of [Pb(Fe0.5Nb0.5)O3](1-x)[Co0.65Zn0.35Fe2O4]x: (x = 0.1, 0.2, 0.3, and 0.4) composites. Rietveld refinement results of X-ray diffraction patterns confirm the formation of these composites for all x values. All the composites show well-saturated ferroelectric and ferromagnetic hysteresis (multiferroic-composite behavior) at room temperature. With increase in Co0.65Zn0.35Fe2O4 (CZFO) content an increase in saturation magnetization, and decrease in saturation polarization, remanent polarization, and dielectric constant are observed. The ferroelectric phase transition temperature increases with increase in CZFO content. All of the compositions undergo second-order ferroelectric phase transitions, which can be explained by Landau-Devonshire theory. The recoverable energy density (∼0.20 to 0.04 J/cm3) and charge-curve energy density (∼0.84 to 0.11 J/cm3) decrease with increase in the CZFO content. The room-temperature magneto-dielectric measurements provide direct evidence of magneto-electric coupling via strain at room temperature. [ABSTRACT FROM AUTHOR]

Ba0.70Ca0.30TiO3-(BCT),Ba(Zr0.2Ti0.8)O3-(BZT) ceramics were fabricated by conventional mixed oxide route to develop inorganic dielectric materials suitable for use as an insulator with high dielectric constant and low energy loss for capacitor applications. The structural phase transition, ferroelectric, dielectric and energy storage properties of BCT, BZT ceramic capacitors were investigated. Room temperature X-ray diffraction (XRD) patterns revealed prominent peaks corresponding to tetragonal perovskite crystal structure for both BCT, BZT solid solutions. Slim ferroelectric hysteresis (P-E) loops were observed for BCT, BZT solid solutions. Temperature dependent dielectric property measurements of BCT, BZT solid solutions have shown a high dielectric constant and low dielectric loss. Room temperature (300K) breakdown field strength and energy densities were obtained from the integral area of P-E loops. For the BCT ceramics, the largest recoverable energy (unreleased energy) density is 1.41 J/cm3with dielectric breakdown strength as high as 150 kV/cm. For the BZT ceramics, the largest recoverable energy (unreleased energy) density is 0.71 J/cm3with dielectric breakdown strength as high as 150 kV/cm. Bulk BCT, BZT ceramics have shown interesting energy densities; these might be the strong candidate materials for capacitor applications. [ABSTRACT FROM AUTHOR]

The room temperature crystal structure of potential high- k dielectric LaGdO3 has been analyzed by X-ray diffraction techniques and its structural evolution with temperature has been probed by Raman spectroscopy. Rietveld refinement of the ambient XRD data established the perfectly layered B-type monoclinic crystal structure with a = 14.43 Å, b = 3.68 Å, c = 8.99 Å, and β = 100.57° which is further validated by the 21 (14 Ag and 7 Bg) Raman-active vibrational modes with centro-symmetric space group [ABSTRACT FROM AUTHOR]

We demonstrated the efficient coupling of BiFeO3 (BFO) ferroelectric material within the carbon–sulfur (C-S) composite cathode, where polysulfides are trapped in BFO mesh, reducing the polysulfide shuttle impact, and thus resulting in an improved cyclic performance and an increase in capacity in Li-S batteries. Here, the built-in internal field due to BFO enhances polysulfide trapping. The observation of a difference in the diffusion behavior of polysulfides in BFO-coupled composites suggests more efficient trapping in BFO-modified C-S electrodes compared to pristine C-S composite cathodes. The X-ray diffraction results of BFO–C-S composite cathodes show an orthorhombic structure, while Raman spectra substantiate efficient coupling of BFO in C-S composites, in agreement with SEM images, showing the interconnected network of submicron-size sulfur composites. Two plateaus were observed at 1.75 V and 2.1 V in the charge/discharge characteristics of BFO–C-S composite cathodes. The observed capacity of ~1600 mAh g−1 in a 1.5–2.5 V operating window for BFO30-C10-S60 composite cathodes, and the high cyclic stability substantiate the superior performance of the designed cathode materials due to the efficient reduction in the polysulfide shuttle effect in these composite cathodes. [ABSTRACT FROM AUTHOR]

(PbZr0.53Ti0.47O3)(1-x)-(PbFe0.5Ta0.5O3)x, (PZTFT, x = 0, 0.1, 0.2, 0.3, 0.4, 1) ceramics were prepared by conventional solid state reaction route. X-ray diffraction patterns and Raman spectra revealed the formation of single phase tetragonal crystal structure at ambient temperature. With increase of Pb(Fe0.5Ta0.5)O3 (PFT) composition in PZTFT matrix significant enhancement in the grain size was observed where average grain sizes were in the range of 1-15 μm. Naturally designed PZTFT composites show higher dielectric constant than Pb(Zr0.53Ti0.47)O3 (PZT) but less than PFT. The ferroelectric (FE) to paraelectric (PE) phase transition temperature i.e. Curie temperature (Tc) shifted towards lower temperature side with increase in iron and tantalum compositions. Both polarization and magnetic moment were observed at room temperature in all PZTFT (x ≥ 0.2) composites suggesting multiferroic characteristic in these systems. Significant improvement of the ferroic properties were observed with increase of PFT concentration. [ABSTRACT FROM AUTHOR]

The practical limitations of fully lithium ion insertion and extraction into LiMn2O4 cathode structure without any structural instability make it unsuitable in commercial Li-ion rechargeable batteries. In this work, we showed that those partially substituted by Ni, i.e., LiMn2-xNixO4 (0≤x≤0.5), prepared by sol-gel technique, could be used as a potential candidate for high energy density and high voltage Li-ion battery applications with superior rate capabilities. The improved structural stability of the cathode was probed by x-ray diffraction and micro-Raman spectroscopy. The density-functional theoretical calculations were employed to identify the minimum energy needed for Li+ diffusion pathway and activation energy in the spinel framework with different Ni ion concentrations. Our results showed significant enhancement in the properties with 25 at. % of Ni solid-solution doping in LiMn2O4 host and the experimental results are in line with the theoretical computations. [ABSTRACT FROM AUTHOR]

We describe extensive studies on a family of perovskite oxides that are ferroelectric and ferromagnetic at ambient temperatures. The data include x-ray diffraction, Raman spectroscopy, measurements of ferroelectric and magnetic hysteresis, dielectric constants, Curie temperatures, electron microscopy (both scanning electron microscope and transmission electron microscopy (TEM)) studies, and both longitudinal and transverse magnetoelectric constants α33 and α31. The study extends earlier work to lower Fe, Ta, and Nb concentrations at the B-site (from 15%-20% down to 5%). The magnetoelectric constants increase supralinearly with Fe concentrations, supporting the earlier conclusions of a key role for Fe spin clustering. The room-temperature orthorhombic C2v point group symmetry inferred from earlier x-ray diffraction studies is confirmed via TEM, and the primitive unit cell size is found to be the basic perovskite Z = 1 structure of BaTiO3, also the sequence of phase transitions with increasing temperature from rhombohedral to orthorhombic to tetragonal to cubic mimics barium titanate. [ABSTRACT FROM AUTHOR]

Non-c-axis-oriented SrBi[sub 2]Nb[sub 2]O[sub 9] (SBN) thin films were grown on Pt/TiO[sub 2]/SiO[sub 2]/Si substrates using the pulsed-laser-deposition technique. X-ray diffraction results confirmed the textured growth of SBN thin films along (115) and (200) orientations. The increase in the value of the dielectric permittivity and decrease in the tangential loss of the films with an increase in annealing temperature were attributed to grain size dependence. SBN thin films annealed at 750 °C exhibited a maximum value of the dielectric constant of ∼346 with a dissipation factor of 0.02. Thin films with certain deposition parameters exhibited the highest remanent polarization (P[sub r]) and coercive field, 25.7 µC/cm² and 198 kV/cm, respectively. There was minimal (<20%) degradation in the switchable polarization (P[sup *] - P[sup ˆ]) after 10[sup 10] switching cycles. At lower field, the leakage current follows ohmic behavior, and at higher field, up to 100 kV/cm, the leakage current density was about 5 × 10[sup -7] A/cm². [ABSTRACT FROM AUTHOR]

Bismuth-layered ferroelectric thin films of Sr[sub 1-x]A[sub x]Bi[sub 2]Ta[sub 2]O[sub 9], with composition x=0 and 0.2, were fabricated by using the pulsed-laser deposition technique. Structural characterization of the films by x-ray diffraction and atomic force microscopy, revealed that the films are polycrystalline in nature with average grain size of 180 nm. The films displayed spherical grains with a surface roughness of 12 nm. The ferroelectric measurements of Sr[sub 0.8]Ba[sub 0.2]Bi[sub 2]Ta[sub 2]O[sub 9], SrBi[sub 2]Ta[sub 2]O[sub 9], and Sr[sub 0.8]Ca[sub 0.2]Bi[sub 2]Ta[sub 2]O[sub 9] showed saturated hysteretic behavior with remanent polarization (2P[sub r]) of 23.5, 17.9, 14 μC/cm[sup 2] and coercive field (E[sub c]) of 31.06, 74.2, 86.3 kV/cm for a maximum applied electric field of 360 kV/cm. Films exhibited minimal (<=17%) degradation of polarization for up to 10[sup 10] switching cycles. It was observed that the coercive field decreased with increase in the ionic size of partially substituted cations. The leakage current density of films were found to be of the order of ∼10[sup -8] A/cm[sup 2] for up to a breakdown field of about 75 kV/cm. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report the crystal structure, dielectric, transport, and magnetic properties of Ni0.65Zn0.35Fe2O4. Rietveld refinement results of X-ray diffraction patterns confirm the phase formation of the material with cubic crystal structure (Fd3m). The frequency dependent ac conductivity behavior obeys the Jonscher's power law and is explained using the jump relaxation model. The observed behavior of temperature dependent bulk conductivity is attributed to the variable-range hopping of localized polarons. The correlation of polaron conduction and high permittivity behavior of NZFO is established on the basis of long range and short range conduction mechanisms. The complex impedance spectra clearly show the contribution of both grain and grain boundary effect on the electrical properties. [ABSTRACT FROM AUTHOR]

Magnetoelectric multiferroic Properties of BTO/CFO/BTO thin films grown on Pt/TiO 2 /SiO 2 /Si. [Display omitted] • Multiferroic thin films were successfully grown using PLD. • Improved magnetoelectric properties for BTO-CFO-BTO. • Interesting multiferroic and magnetoelectric properties. A magnetoelectric multiferroic bi-phase system with robust ferroelectric and ferro/ferri-magnetism response at room temperature would be ideally suitable for microelectronics, memory devices, and for spintronic applications. BaTiO 3 /CoFe 2 O 4 /BaTiO 3 (BTO/CFO/BTO) heterostructured films were pulsed laser deposition grown on Pt(1 1 1)/TiO 2 /SiO 2 /Si substrates. High quality polycrystalline films were grown by thermal annealing at 750 °C, at an oxygen partial pressure of 100 mTorr for 1 h. Crystal quality and phase formation information was monitored using X-ray diffraction (XRD). XRD confirm the growth of polycrystalline heterostructures and the coexistence of both perovskite BTO and spinel CFO phases in heterostructures. In order to obtain robust magnetoelectric coupling, we studied the tri-layer structure as a representative ferroelectric/ferrimagnetic/ferroelectric system. We report the ferroelectric, leakage current behavior, ferrimagnetic, and frequency dependent ME properties of the films. Ferroelectric BTO and ferrimagnetic inverse spinel CFO nature is also confirmed using the piezoresponse force microscopy and magnetic force microscopy measurements. These nanostructures exhibit high saturation polarization (Ps ∼ 99.86 µC/cm2), saturation magnetization (Ms ∼ 51.48 emu/cm3), and a strong ME coupling coefficient of ∼ 274 mV/cm-Oe with a bias magnetic field of + 90 Oe, anda frequency of 1 kHz revealing them as prospective candidates for multifunctional applications. [ABSTRACT FROM AUTHOR]

Core-shell like structured barium zirconium titanate-barium calcium titanate-poly(methyl methacrylate) [(Ba 0.94 Ca 0.06 )(Zr 0.16 Ti 0.84 )O 3 -PMMA] nanocomposites were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate (MMA) from the surface of BZT-BCT nanoparticles. X-ray diffraction patterns of pure polymer and BZT-BCT nanoparticles revealed their amorphous and polycrystalline natures respectively. Fourier transform infrared spectroscopy confirmed the grafting of the PMMA shell on the surface of the BZT-BCT nanoparticles cores. Transmission electron microscopy (TEM) results revealed that BZT-BCT nanoparticles were covered by a very thin layer of PMMA forming a core-shell like structure and thermogravimetric analysis results showed that the grafted BZT-BCT-PMMA nanoparticles consist of ∼80.1% PMMA by weight. Polymer grafted BZT-BCT nanocomposite thick films (∼10 μm) have shown an improved dielectric constant (ε∼56), a high breakdown field strength (∼3 MV/cm) and high-energy storage density ∼22.5 J/cm 3 . The improved electrical properties of core-shell like structured BZT-BCT-PMMA nanocomposites were attributed to improved nanoparticle dispersion and enhanced interfacial polarization due to the covalent linkage between polymer and nanoparticle interface. Mechanically stable and homogeneous composite films were obtained using the surface grafted BZT-BCT ceramic nanoparticles. [ABSTRACT FROM AUTHOR]

Li 2 MnO 3 is known to be electrochemically inactive due to Mn in tetravalent oxidation state. Several compositions such as Li 2 MnO 3 , Li 1.5 Al 0.17 MnO 3 , Li 1.0 Al 0.33 MnO 3 and Li 0.5 Al 0.5 MnO 3 were synthesized by a sol–gel Pechini method. All the samples were characterized with XRD, Raman, XPS, SEM, Tap density and BET analyzer. XRD patterns indicated the presence of monoclinic phase for pristine Li 2 MnO 3 and mixed monoclinic/spinel phases (Li 2 − x Mn 1 − y Al x + y O 3 + z ) for Al-substituted Li 2 MnO 3 compounds. The Al substitution seems to occur both at Li and Mn sites, which could explain the presence of spinel phase. XPS analysis for Mn 2p orbital reveals a significant decrease in binding energy for Li 1.0 Al 0.33 MnO 3 and Li 0.5 Al 0.5 MnO 3 compounds. Cyclic voltammetry, charge/discharge cycles and electrochemical impedance spectroscopy were also performed. A discharge capacity of 24 mAh g −1 for Li 2 MnO 3 , 68 mAh g −1 for Li 1.5 Al 0.17 MnO 3 , 58 mAh g −1 for Li 1.0 Al 0.33 MnO 3 and 74 mAh g −1 for Li 0.5 Al 0.5 MnO 3 were obtained. Aluminum substitutions increased the formation of spinel phase which is responsible for cycling. [ABSTRACT FROM AUTHOR]

Novel composite cathode materials, x Li 2 MnO 3 –(1− x )LiNi 2/3 Co 1/6 Mn 1/6 O 2 (where x = 0.3, 0.5, and 0.7), were synthesized by sol–gel route and characterized by advanced techniques for rechargeable Li-ion battery applications. Phase purity of the composites was examined by XRD as well as Raman spectroscopy and the studies revealed good crystallinity and the formation of pure composite phases with monoclinic ( C2/m ) and hexagonal ( R3m ) crystal structures for Li 2 MnO 3 and LiNi 2/3 Co 1/6 Mn 1/6 O 2 , respectively. Polyhedral agglomerates seen in the scanning and transmission electron microscopic images elucidated the better electrochemical properties of the composites. Valence states of transition metals in the composites were examined by X-ray photoelectron spectroscopy and the analysis suggested predominant oxidation states of Ni, Co, and Mn as 2+, 3+, and 4+, respectively. Galvanostatic charge–discharge tests, performed at different C-rates between 2.0 and 4.8 V, indicated high discharge capacity (∼250 mAh g −1 ), good rate capability, and excellent cycleability of the composite with x = 0.5 compared to the composites with x = 0.3 and 0.7. In-situ Raman spectroscopic studies revealed the activation of Li 2 MnO 3 component in all composite cathode materials during the first cycle charging process with structural stability thereby enhancing performance of the composite with x = 0.5. These results demonstrated the feasibility of using 0.5Li 2 MnO 3 -0.5LiNi 2/3 Co 1/6 Mn 1/6 O 2 composite as advanced cathode for high power Li-ion batteries. [ABSTRACT FROM AUTHOR]

The room temperature crystal structure of potential high- k dielectric LaGdO3 has been analyzed by X-ray diffraction techniques and its structural evolution with temperature has been probed by Raman spectroscopy. Rietveld refinement of the ambient XRD data established the perfectly layered B-type monoclinic crystal structure with a = 14.43 Å, b = 3.68 Å, c = 8.99 Å, and β = 100.57° which is further validated by the 21 (14 Ag and 7 Bg) Raman-active vibrational modes with centro-symmetric space group [ABSTRACT FROM AUTHOR]