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Magnetoelectric (ME) coupling properties of La0.7Ba0.3MnO3 (LBMO)/P (VDF-TrFE) (0–3) nano-composite films were investigated for device-oriented application like magnetic sensors, actuators, energy harvesting devices etc., The LBMO nanoparticles were prepared by sol–gel auto combustion method. LBMO/P (VDF-TrFE) nanocomposite film was prepared by solution casting method for 0.5% volume fraction of LBMO nanoparticles in P (VDF-TrFE) matrix. This nanocomposite film shows ferromagnetic and ferroelectric properties simultaneously at room temperature. The ME properties of these composite films were studied extensively. The ME coupling coefficient is highly dependent on the angle between ferroelectric polarization and applied magnetic field. The maximum measured in plane ME voltage coefficient α 31 V is found to be 121.5 mV cm−1 Oe−1with application 25 Oe at 10 kHz by lock-in technique. The α 31 V is maximum at the angles 90° and 270° between ferroelectric polarization and applied magnetic field. The hysteresis of α 31 V confirms the existence of electric polarized domain formed with the decrease in magnetic field and the process is irreversible. [ABSTRACT FROM AUTHOR]

Structure, microstructure, complex impedance spectroscopy, and dielectric relaxation studies were carried out on La-substituted Bi4−xLaxTi3O12 lead-free ceramics (x = 0 to 1.5), which were synthesized by solid-state reaction method. Structural and microstructural analysis depicted orthorhombic (O) to tetragonal (T) transformation and decrease of average grain size from 20 to 2 μm with increasing "x." Complex impedance spectroscopy studies showed contribution of grain boundary, plate boundary, and grain interior of Bi4−xLaxTi3O12 ceramics to its overall electrical properties. The results revealed substitutional site preference of the La3+-ions to the Bi ions of the (Bi2Ti3O12)2−perovskite unit for x < 1 and at the Bi-site of the Bi2O22+ layer for x ≥ 1. The temperature-dependent dielectric studies revealed ferroelectric to relaxor crossover for x = 1.5 implying reduction in interaction within the polar regions. The observed relaxor-like dielectric behavior analysis suggests generation of small-sized polar regions because of random fields generation by diminishing charge compensating role of Bi2O22+layer with high La3+-doping. Random weakly interaction between the small polar regions leads to critical slowing down of polar regions dynamics below 119 K. [ABSTRACT FROM AUTHOR]

La0.7Sr0.3MnO3 (LSMO)/poly(vinylidenefluoride-co-trifluoroethylene)(P(VDF-TrFE) particulate nanocomposite films prepared to produce large magnetoelectric (ME) voltage at room temperature for multifunctional device applications. LSMO nanoparticles (NPs) were prepared by sol–gel auto-combustion method and these NPs belong to space group R-3c. LSMO/P(VDF-TrFE) (0–3) nanocomposite (NC) films were prepared by solution casting method for different volume percentage of LSMO in P(VDF-TrFE). Dielectric and DC leakage current density(J) analysis of these NCs reveal very small loss tangents (~ 0.01) and very small leakage current density J ~ 10−7 A/mm2 respectively, which further demonstrate the uniform distribution of NPs in P(VDF-TrFE) matrix. Room temperature M-H and low temperature M-T analysis of LSMO NPs confirm ferromagnetic nature with Curie temperature at ~ 368 K. LSMO/P(VDF-TrFE) NC films exhibit multiferroic properties up to 5% volume percentage of LSMO at room temperature. A maximum ME voltage 11.68 mV is produced corresponding to giant transverse ME voltage coefficient ( α 31 V) = 155.74 mVOe−1 cm−1 at DC magnetic field (Hdc) = 2.57 kOe and AC magnetic fileld(Hac) = 25Oe for 0.5% LSMO volume percentage NC films. A self bias ME voltage 11.3175 mV is observed at zero Hdc for 0.5% LSMO volume percentage NC films, which can be used inpotential ME devices.The variation of ME voltage coefficient α V at different angles between P and applied magnetic field(Hdc) for 0.5% LSMO NC films is also reported which shows α V is maximum at the angles 90º and 270º. [ABSTRACT FROM AUTHOR]

Lead‐free (Ba1–xCax)(Zr0.05Ti0.95)O3 (x = 0.03, 0.05, 0.08, 0.10, 0.12, and 0.15) (BCZTx) ceramics are fabricated using the solid state reaction method. The ionic conductivity of the ceramic samples is investigated by complex impedance spectroscopy. The impedance measurements suggest that doubly charged oxygen vacancies (VO··) are responsible for conduction and relaxation. The impedance measurements show that with increase in calcium content the ionic conductivity increases till x = 0.10 and thereafter it decreases gradually. This anomaly in the conductivity is discussed on the basis of structural parameters such as lattice free volume, tolerance factors, and number of equivalent oxygen sites. The presence of the anomaly at x = 0.10 is attributed to a balance between the number of equivalent oxygen sites increasing and the lattice free volume reducing with calcium content. [ABSTRACT FROM AUTHOR]

Dielectric and ac impedance studies have been carried out on undoped and Mg (0.5 and 1 mol %) doped near-stoichiometric lithium tantalate (SLT) single crystals. No particularly significant qualitative change is observed in the nature of the ferroelectric phase transition on doping by Mg. However, an anomaly is observed in the ac impedance data: the ac conductivity is found to be low for 0.5 mol % doping of Mg, compared to 1.0 mol % doping. Also, the activation energy, calculated from the Arrehenius equation, is highest for 0.5 mol % doping, which suggests that hopping of Li+ ions becomes more hindered in 0.5 Mg SLT. The Nyquist plot shows a single semicircle above 100 Hz. The electrical behavior of lithium tantalate can be modeled as a resistance parallel to a constant-phase element. The calculated impedance from this equivalent circuit is also found to be high for the 0.5 mol % doping. This feature is explained in terms of a Li-vacancy model. [ABSTRACT FROM AUTHOR]

The dielectric behavior of lithium tantalate (LT) single crystals has been investigated in the vicinity of the ferroelectric phase transition for nonstoichiometric and near-stoichiometric compositions. Fitting of the experimental data to a modified Curie-Weiss equation indicates the occurrence of a mildly relaxor-ferroelectric-like phase transition in congruent LT single crystals (with the Curie-Weiss exponent γ having a value 1.2, rather than the value unity for a regular ferroelectric). As the Li concentration of these crystals approaches the stoichiometric value, the phase transition gets sharper, indicative of an increasing amount of long-range ordering. The bulk concentration of cation vacancies has also been estimated. [ABSTRACT FROM AUTHOR]

Optically polished titanium doped congruent lithium niobate single crystals were implanted with protons of energy of 120 keV (at fluences of 1×1015, 1×1016, and 1×1017 ions/cm2). Some loss of lithium from the surface upon ion implantation was recovered by irradiation with 50 MeV lithium ions (at fluences varying from 1×1011 to 1×1013 ions/cm2). The near surface region defects created in the crystal were analyzed using high resolution x-ray diffraction technique, atomic force microscopy, fourier transform infrared, and optical transmittance (UV-visible) studies. The marked lattice strain induced by the energetic ions was characterized by high resolution x-ray diffraction measurements. Three-dimensional defect clusters were observed from atomic force microscopy with nanoscale resolution. Variations of O–H bond stretching vibrations as a function of fluences were observed. Optical transparency of these samples was found to depend on implantation, irradiation, and combined processes. Correlating the structural information with surface morphology experiments, the existence of a waveguide layer on lithium niobate surface has been ascertained. [ABSTRACT FROM AUTHOR]

In this study, we investigate magnetoelectric (ME) properties in nanocomposite films (P(VDF-TrFe))/SmFeO3 consist of ferroelectric copolymer, poly(vinylindene fluoride-trifluoroethylene) (P(VDF-TrFe)) and magnetic SmFeO3 nanoparticles. Comparative magnetization vs magnetic field hysteresis loops for un-poled and electric field poled (P(VDF-TrFe))/SmFeO3 nanocomposite films demonstrate strong electric filed control of magnetization. The nanocomposite films exhibit large exchange biasing (EB) effects in magnetic measurements near spin switching temperature (~ 100 K) of SmFeO3 and the EB effects were significantly modified under electric field (E) poled conditions (at E = 200 kV/cm), indicating ME coupling. Remarkably, we observe electric field poling induced self biased converse ME effect in the (P(VDF-TrFe))/SmFeO3 nanocomposite films. The maximum magnetoelectric output voltage (α) obtained is 55 mV/cm/Oe at Hbias = 1 kOe and 25 mV/cm/Oe at Hbias = 0, after electric field poling. The discovery of self biasing phenomenon with converse ME effects at room temperature in flexible (P(VDF-TrFe))/SmFeO3 nanocomposite films is highly desirable for device applications such as electrically controlled thin memory devices and ME sensors etc. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Pb1-xLax/2Smx/2Ti1-xFexO3 (x = 0.20 and 0.30) have been prepared by solid state reaction route. The electrical properties of synthesized samples have been investigated using complex impedance spectroscopy as a function of frequency (100 Hz-1 MHz) within the temperature range of (448-573 K). The fitting of the Nyquist plots reveals that both grain and grain boundary contribute to relaxation and the grain boundaries are more resistive and capacitive than the grains. Modulus analysis shows that relaxation in both the samples is of non-Debye type and temperature independent. The Jonscher's power law fit to the ac conductivity data confirms that the conduction in the prepared samples is due to the hopping of charge carriers. Long range conductivity type of relaxation is found in both the samples. [ABSTRACT FROM AUTHOR]