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Dynamic responses of copper titanates to alternating electric fields with different strengths are characterized in terms of dielectric spectrums. This work extends the introduction of quasipolaron surface polarization (QSP). A collective of quasipolarons pinned at grain surfaces is involved in the electric polarization, which is confirmed by the quadratic polarization–permittivity relation. Because electric polarization is a macroscopic quantum effect, the QSP is described in terms of the density of states (DOS). As a sign of reverse ferroelectricity, dielectric hysteresis loops of reverse-S shape reveal that the characteristic remnant polarization is proportional to the DOS ratio of quasipolaron surface excited to ground states. Although the DOS of the surface ground state is dependent on the mole ratio of quasipolaron quantity, both the DOS and the energy levels of surface excited states show the intrinsic angular-frequency dependence in a power function manner. [ABSTRACT FROM AUTHOR]

Composites derived from polyvinylidene fluoride (PVDF) play an important role in advanced dielectric energy storage due to their outstanding characteristics, including remarkable flexibility, low density, high dielectric permittivity, and superior dielectric breakdown strength. The strategically designed composition significantly enhances the energy storage performance, such as discharge energy density (Ue) and charge–discharge energy efficiency (η). Consequently, we employed the solution cast method to create flexible composite films, combining PVDF polymer with strontium tungstate (SrWO4) ceramic. X-ray diffraction analysis revealed the coexistence of α and electroactive β phases in PVDF. These phases have a substantial effect on the dielectric characteristics and energy storage density of composites. Flexible nanocomposites of PVDF and SrWO4 exhibit high dielectric constant and low tangent loss. Micrographs obtained using scanning electron microscopy (SEM) showed that the morphology of the composite varies according to the amount of filler present in the matrix. The impedance spectroscopy method yielded intriguing findings regarding the roles of both grain and grain boundaries in the overall resistance characteristics of the composites. The frequency-dependent behavior of alternating conductivity follows Jonscher's power law. The hysteresis loops indicate that the nanocomposite film maintains favorable ferroelectric properties. The present study suggests some promising applications for advanced dielectric capacitors and energy storage devices. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy assessed dielectric properties of PMN at a single PT concentration. Real and imaginary impedance of (1−x) PMN–xPT materials were analyzed using this technique. Through electrical impedance spectroscopy, the loss tangent factor and electric modulus were determined, leveraging research on semiconductor conduction. The study also presented the synthesis and characterization of solid ceramic lead magnesium nibate-lead titanate (1−x) PbMg1/3Nb2/3-xPbTi3, representing a significant advancement in impedance spectroscopy research. The dielectric behavior was examined by studying the polarization evolution in response to the applied field, aiming to replicate the magnetic phase boundary configuration found in typical ferroelectric behavior. Temperature had a notable impact on the hysteresis loop, with increasing temperature and decreasing applied field resulting in decreased leftover polarization and increased coercive field. The impedance and complex modulus graphs exhibited distinct semicircle patterns attributed to higher grain boundary resistance and capacitance compared to (1−x) PMN-xPT. The Nyquist plot highlighted bulk effects. [ABSTRACT FROM AUTHOR]

Chromium ( C r 3 + ) doped B a T i 1 − x C r x O 3 (x = 0.0, 0.03, 0.06, and 0.09) ceramics were prepared by the solvothermal reflux approach. X-ray diffraction analysis confirmed the development of tetragonal structures with P 4 m m symmetry in the prepared samples. The SEM analysis showed that C r 3 + doping resulted in a microstructure that was dense, uniform, and had smaller grains. Surface chemical information and oxidation states were studied using X-ray photoelectron spectroscopy. The diffuse reflectance spectrum confirmed the effect of C r 3 + content on the direct optical bandgap of B a T i 1 − x C r x O 3 samples which shifts from 3.21 eV to 2.73 eV with increasing C r 3 + content. Dielectric permittivity was found to increase in the low-frequency region with increasing C r 3 + doping content up to x = 0.06, while it decreased in the high-frequency region compared to an undoped sample. The observed behavior of permittivity might be explained in terms of the formation of oxygen vacancy defects and their effects on the polarization dynamics of the material. Moreover, the addition of C r 3 + doping had a strong effect on the ferroelectric characteristics, as seen by the formation of a pinched hysteresis loop, resulting in the improvement of energy storage properties. Based on the obtained results, the sample with x = 0.06 exhibited an enhancement of about 3.3 times in energy discharge density and 26 % in storage efficiency compared to the undoped sample. This might be due to a large difference between the values of maximum and remnant polarizations, reduced tangent loss, and a smaller grain size, which makes this material attractive for use in energy storage devices. [ABSTRACT FROM AUTHOR]

In this article, a comprehensive investigation of structural as well as electrical properties of Sm2O3-modified Bi4Ti3O12 (i.e. Bi3.8Sm0.2Ti3O12), a member of the Aurivillius family has been synthesized by using a mixed-oxide reaction technique. The sample crystallizes in orthorhombic symmetry (space group, B2ab). The electrical behaviors of the pure material, bismuth titanate are improved considerably by substituting a small amount (20%) of trivalent rare-earth (i.e. samarium) ion at its Bi-site. The electrical characteristics of the compound at different temperatures (25–500 °C) over a wide-ranging frequency (1 kHz–1 MHz) have shown several interesting features. The compound displays higher dielectric constant as well as lower tangent loss. The presence of ferroelectricity in the material is established by the P–E hysteresis loop. The J–E characteristics at various temperatures display the Ohmic conduction with a low leakage current that makes the material useful in several electronic industries. [ABSTRACT FROM AUTHOR]

Nickel-doped magnesium cubic spinel ferrite nanoparticles (NPs) were prepared through the microwave combustion method (MCM). The structure of magnesium ferrite normal spinel is obtained from XRD analysis. The average crystallite size is between 26 and 17 nm. The elemental compositions and oxidizing states of Ni2+ doped MgFe2O4 ferrites were evaluated by using XPS analysis. The morphology of spinel nanoparticles was studied using HR-SEM images. The energy dispersive X-ray method is used for ensuring the presence of elements and the band gap value 2.09, 2.02, 1.85, and 1.82 eV have been obtained using the tau'c relation. The magnesium spinel structure is confirmed in the band at 434 and 561 cm−1 which corresponds to the stretching vibration of the octahedral site (Mg2+–O2−) and tetrahedral site (Fe3+–O2−) respectively. From the hysteresis loops the magnetic features viz. Hc, Mr, and Ms were determined. Further dielectric studies and AC conductivity of the prepared samples are performed. [ABSTRACT FROM AUTHOR]

The current communication addresses structural, impedance, conductivity, dielectric permittivity, tangent loss, and ferroelectric hysteresis of selenium doped bismuth titanate (Bi4Ti2.9Se0.1O12) synthesized by a solid-state reaction technique. XRD profile reveals the formation of orthorhombic unit cell structure (B2ab space group) in Bi4Ti2.9Se0.1O12. Partial doping of Se (10%) makes significant modifications in the electrical and dielectric characteristics, which are investigated over discrete frequencies (1 kHz–1 MHz) and temperatures (27–300 °C). The compound exhibits comparatively low value of the tangent loss at 1 MHz frequency. The ferroelectric hysteresis loop of the compound confirms the non-centrosymmetric arrangement of elements at room temperature, and the value of remanent polarization makes the compound suitable for memory applications. [ABSTRACT FROM AUTHOR]

The dielectric hysteresis loops of a uniaxial triglycine sulfate (TGS) ferroelectric have been studied in a wide range of switching field frequencies. The experimental dependence of the coercive field on the switching frequency is compared with the Kolmogorov–Avrami domain switching model and the domain nucleation model. It is shown that both switching models agree reasonably well with the experiment and that the character of switched domain motion changes with a change in the switching field frequency. [ABSTRACT FROM AUTHOR]

The current communication addresses structural, impedance, conductivity, dielectric permittivity, tangent loss, and ferroelectric hysteresis of selenium doped bismuth titanate (Bi4Ti2.9Se0.1O12) synthesized by a solid-state reaction technique. XRD profile reveals the formation of orthorhombic unit cell structure (B2ab space group) in Bi4Ti2.9Se0.1O12. Partial doping of Se (10%) makes significant modifications in the electrical and dielectric characteristics, which are investigated over discrete frequencies (1 kHz–1 MHz) and temperatures (27–300 °C). The compound exhibits comparatively low value of the tangent loss at 1 MHz frequency. The ferroelectric hysteresis loop of the compound confirms the non-centrosymmetric arrangement of elements at room temperature, and the value of remanent polarization makes the compound suitable for memory applications. [ABSTRACT FROM AUTHOR]

A new compound of chemical formula (BiBa)(FeMn2)O8 is prepared by a solid‐state reaction method. X‐ray structural studies confirm orthorhombic unit cell of the compound. Room‐temperature magnetic data display ferromagnetic hysteresis loop with high value of effective magnetic moments. The dependence of dielectric constant, loss tangent, impedance, and the conductivity at different frequencies (1 kHz−1 MHz) are measured using LCR meter on rise of temperature from room temperature to 500 °C. The dielectric constant increases on rise of temperature due to Maxell–Wagner polarization, and the loss tangent displays similar behavior. A low value of loss tangent is obtained at higher frequencies, which paves the way for the application of the compound in high‐frequency devices. The real impedance of the compound decreases indicating NTCR (negative temperature coefficient of resistance) behavior, and the imaginary impedance displays relaxor behavior. The Nyquist plot fits to a series combination of two RQC circuits ((RQC)(RQC)) and indicates the presence of non‐Debye relaxation. The frequency variation of conductivity obeys Jonscher's power law and reveals different conduction mechanisms in grain and grain boundary regions. [ABSTRACT FROM AUTHOR]

The research and development of energy storage materials and devices has now become the current hotspot. In this work, we designed high performance (0.93- x)(Bi 0.5 Na 0.5)TiO 3 -0.07BaTiO 3 - x (Sr 0.7 Bi 0.2)TiO 3 (BNT-0.07BT- x SBT) energy storage ceramics with large recoverable energy storage density and high energy efficiency. Results showed that the introduction of SBT into BNT-0.07BT matrix improved the crystal structure symmetry of the material and induced strong relaxation behavior with broadened dielectric peak. The ferroelectric long-term order of the BNT-0.07BT matrix is destructed via SBT modification, yielding the slender P-E hysteresis loop in samples with higher SBT content. Good energy storage performance with large effective energy storage density W rec of 3.26 J/cm3 and high energy storage efficiency η of 90.3% was obtained in 40 mol%SBT -modified sample, under the electric field of 260 kV/cm. The charge-discharge performance test showed that the sample exhibited a short discharge time (t 0.9 = 143 ns) and a relatively high power density (P D = 40.8 MW/cm3) under an electric field of 160 kV/cm. Moreover, sample showed good thermal stability in the temperature range of 30–180 °C and high frequency stability in the frequency range of 1–1000 Hz. As an attractive material for dielectric capacitor, BNT-0.07BT- x SBT energy storage ceramics have potential applications in pulse power systems. [ABSTRACT FROM AUTHOR]

A new compound of chemical formula (BiBa)(FeMn2)O8 is prepared by a solid‐state reaction method. X‐ray structural studies confirm orthorhombic unit cell of the compound. Room‐temperature magnetic data display ferromagnetic hysteresis loop with high value of effective magnetic moments. The dependence of dielectric constant, loss tangent, impedance, and the conductivity at different frequencies (1 kHz−1 MHz) are measured using LCR meter on rise of temperature from room temperature to 500 °C. The dielectric constant increases on rise of temperature due to Maxell–Wagner polarization, and the loss tangent displays similar behavior. A low value of loss tangent is obtained at higher frequencies, which paves the way for the application of the compound in high‐frequency devices. The real impedance of the compound decreases indicating NTCR (negative temperature coefficient of resistance) behavior, and the imaginary impedance displays relaxor behavior. The Nyquist plot fits to a series combination of two RQC circuits ((RQC)(RQC)) and indicates the presence of non‐Debye relaxation. The frequency variation of conductivity obeys Jonscher's power law and reveals different conduction mechanisms in grain and grain boundary regions. [ABSTRACT FROM AUTHOR]

Multiferroic composites offer promising prospects for low-power multifunctional devices. Here, we report the structural, electrical, dielectric, magnetic, and magnetodielectric properties of the multiferroic composite material (1 − x)LiNbO3–xLa0.9Na0.1MnO3 (where x = 0.1, 0.2, and 0.3). Ferroelectric and magnetic phases were synthesized using citrate gel method and the conventional solid-state reaction method was used for the preparation of multiferroic composite material with different mixing percentage values of x. X-ray diffraction was used to confirm the crystalline purity and the crystal structure of the material. The microstructural and elemental composition analyses were done by FE-SEM, X-ray photon spectroscopic (XPS), and EDAX techniques. Dielectric studies and impedance analysis imply the dynamic behavior of charge carriers inside the composites. The maximum value of dielectric constant (5000) was obtained at x = 0.3 for xLa0.9Na0.1MnO3 phase. From impedance analysis method, the equivalent circuit of (1 − x)LiNbO3–xLa0.9Na0.1MnO3 (where x = 0.1, 0.2, and 0.3) composite was found out. The P–E hysteresis loop reveals the ferroelectric nature of the composite. Sample with x = 0.1 of xLa0.9Na0.1MnO3 phase gives the highest values for maximum polarization and remnant polarization. The enhanced magnetic properties of the composite material were substantiated with M–H hysteresis loop measurements. The magnetodielectric and magnetoelectric coupling measurements revealed the presence of ferroelectric and ferromagnetic coupling nature of the composite material. From all these analyses, the multiferroic composites with the composition x = 0.3(La0.9Na0.1MnO3) yields the maximum ferroelectric and magnetic coupling behavior. So, this composite material has wide applications in multifunctional nano devices. [ABSTRACT FROM AUTHOR]

The results of the BiFeO3 nanoparticles, magnetic, dielectric and local electromechanical responses investigation, obtained by hydroxocarbonate coprecipitation are presented. The weak ferromagnetic response was demonstrated by both vibrating sample magnetometry and magnetic force microscopy. The measurements of the local electromechanical response of the individual nanoparticles demonstrate a presence of the hysteresis loops, which indicate its ferroelectric state. [ABSTRACT FROM AUTHOR]

Ba0.92Ca0.08Ti0.95Zr0.05O3 (BCZT8-5) ceramic materials have been scarcely studied as lead-free piezo/ferroelectrics despite their enhanced Curie temperature (>100 °C) with respect to most studied BCZT compositions. In this work, homogeneous dense BCZT8-5 ceramics with grain size in the range of 20 μm, and optimum ferroelectric, dielectric, and electromechanical performance, were prepared by the mixed oxides route using moderate synthesis (1250 °C-2 h) and sintering (1400 °C-2 h) conditions. Thickness-poled thin disks and monomodal shear plate resonators were used for the determination of piezoelectric coefficients, coupling factors, elastic, and dielectric permittivity coefficients, including all losses, by iterative analysis of impedance curves at resonance. Furthermore, the thermal evolution of the piezoelectric characteristics at resonance was determined to assess the enhanced working range of the ceramics (≈100 °C). Ferroelectric hysteresis loops and strains vs. electric-field butterfly loops were also measured and showed soft behavior with Ec = 2 kV/cm, Pr = 12 μC/cm2 after a maximum applied field of 3 kV was used. The ceramics showed a high endurance of P-E cycles to electrical fatigue up to 107 cycles. Moreover, dielectric properties as a function of temperature were also accomplished and showed nearly normal ferroelectric behavior, characteristic of samples with low crystallographic disorder. Overall, these ceramics showed high sensitivity and higher stability than other currently studied BCZT compositions. [ABSTRACT FROM AUTHOR]

Studies of the dielectric and ferroelectric properties of c-oriented Ba2NdFeNb4O15 films is carried out at T = −190...200 °C using dielectric spectroscopy methods and ferroelectric hysteresis loops analysis. The films were obtained by RF-cathode sputtering method in an oxygen atmosphere. The PA-FE phase transition region, the features of the dielectric response formation, and the mechanisms responsible for that formation are revealed in the material. It is shown that the studied materials are characterized by high values of energy efficiency parameters. The reasons of the revealed regularities and the prospects of the use of these materials are discussed. [ABSTRACT FROM AUTHOR]

The evolution of the dielectric hysteresis loops shape during heating of PMN-0.28PT single crystals possessing rhombohedral symmetry at room temperature was studied in the temperature range from room temperature to 200 °C. Revealed formation of the triple and double dielectric hysteresis loops in the relaxor phase upon switching by an electric field was explained by the influence of depolarizing fields arising at the interface of non-polar inclusions, and by the ineffective screening of polar clusters forming during transition through a percolation threshold, correspondingly. Further size decrease in the polar clusters due to heating led to their transformation to polar nanoregions. [ABSTRACT FROM AUTHOR]

This article presents the current–voltage (I–V) characteristics, ferroelectric (P–E) and energy density properties of polyvinylidene fluoride (PVDF) film samples synthesized by melt-press and solution-cast techniques. Our earlier work reported the α and γ -PVDF phase stabilization in PVDF film samples processed by melt-pressing and solution-casting respectively. In the present work, the I–V loops of pure PVDF film samples were recorded with variable delay time from 0.0005 to 1 s in order to understand the switching behavior response of molecular dipoles in different PVDF molecular conformations. The hysteresis behavior of I–V loops revealed the dominance of dipolar switching current in both the α and γ-PVDF phases. The slim P–E hysteresis loops with low remnant polarization Pr values ≈0.26 and 0.21 μC/cm2 at an applied electric field of 100 kV/cm for α and γ -PVDF phases respectively were traced. The dielectric energy storage efficiency η as calculated from P–E loop data was found to be ≈37.7% and 38.6%, respectively, for α and γ -phases of PVDF. The low leakage current and slim P–E hysteresis behavior in both the α and γ -phases of PVDF are favorable or desired for their application in dielectric energy storage capacitors. [ABSTRACT FROM AUTHOR]

As a favorable candidate for the next‐generation smart electronic devices, thermo‐responsive dielectric materials are faced with two crucial challenges: insufficient mechanical toughness and lack of the combination of promising dielectric switching properties, desired mechanical properties, and long‐cycle stability. Herein, a new scalable strategy is proposed for designing thermo‐responsive dielectric switching materials that simultaneously integrate the individual features, such as promising dielectric switching properties, outstanding mechanical properties, and great cycle stability, into one gel, based on a new dual dielectric switching mechanism induced by interfacial structure evolution. The ionic gel can readily achieve a superb combination of distinct reversible dielectric bistability, a high dielectric switching ratio above 150, a ≈15 °C wide thermal hysteresis loop, and tunable room‐temperature dielectric transition behavior, impressive high ductility, desirable high mechanical strength, record‐high stability of at least 1000 cycles. Such an all‐in‐one design enhances the adaptability to multiple application scenarios, durability, and a lifetime of the dielectric switching gels. Together with the facile fabrication process and recyclable thermoplastic system, thereby contributing to cost and energy saving, this research provides a feasible and sustainable strategy for constructing highly desirable thermo‐responsive dielectric switching materials. [ABSTRACT FROM AUTHOR]

Soft robots often show overwhelming performances. In the present work, mathematical formulations have been derived for nonlinear dynamic analysis of axial stretch in convex tapered dielectric elastomer considering temperature dependent material properties. The present formulation is based on the Gent model of hyperelasticity and the standard rheological model. The fish tail is modeled as bimorph dielectric elastomer actuator (DEA) for propulsion of soft fish robot. Based on the obtained axial stretch of the active layer, flapping movements of fish tail have been determined. The dependency of frequency, temperature, viscoelasticity, and taper effects on the dynamic performance in the active layer of bimorph DEA is studied. Investigation of time-dependent actuation, phase portraits, Poincare maps, bifurcation diagrams, and hysteresis loop associated in this system is carried out. The results reveal that at lower temperature more actuation is attained. At low frequency, time-dependent data show very small amplitude. With the increase in height taper, it is declared that the actuation increased. Thus, it is also observed that taper effects have significant role on the axial stretch. Subsequently, with the obtained stretch, deflection of bimorph DEA is determined through mathematical formulation in order to predict the bending actuation of fish tail. [ABSTRACT FROM AUTHOR]

Tuning and stabilizing a large imprint in epitaxial relaxor ferroelectric thin films is one of the key factors for designing micro-electromechanical devices with an enhanced figure of merit (FOM). In this work, epitaxial 500 nm-thick 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (PMN–33PT) films, free from secondary phases and with extremely low rocking curves (FWHM < 0.05°), are grown on ScSmO3 (SSO) and DyScO3 (DSO) substrates buffered with SrRuO3 (SRO). The PMN–33PT is observed to grow coherently on SSO substrates (lattice mismatch of −0.7%), which is c-axis oriented and exhibits large tetragonality compared to bulk PMN–33PT, while on DSO substrates (lattice mismatch of −1.9%), the PMN–33PT film is almost completely relaxed and shows reduced tetragonality. Due to the compressive epitaxial strain, the fully strained PMN–33PT film displays typical ferroelectric P–E hysteresis loops, while the relaxed sample shows relaxor-like P–E loops. Samples present large negative imprints of about −88.50 and −49.25 kV/cm for PMN–33PT/SRO/SSO and PMN–33PT/SRO/DSO, respectively, which is more than threefold higher than the coercive field. The imprint is induced by the alignment of defect dipoles with the polarization and is tuned by the epitaxial strain. It permits the stabilization of a robust positive polarization state (Pr ∼ 20 μC/cm2) and low dielectric permittivity (<700). In addition, the relaxed PMN–33PT film shows improved piezoelectric properties, with a 33% enhancement in d33,eff relative to the fully strained sample. The obtained low dielectric permittivity and the high piezoelectric coefficients at zero electric field in the studied PMN–33PT films hold great promise to maximize the FOM toward applications in piezoelectric devices. [ABSTRACT FROM AUTHOR]

In the present work, we synthesized composites (1 − x) Bi0.9La0.1FeO3-(x) BaTiO3 with x = 0.05, 0.10, and 0.15 by solid-state technique. We studied their crystal structure, morphology, optical, electrical, and magnetic behavior. Crystal structure of the constituents of the composites and their presence in the composite was witnessed from the analysis of X-ray diffractograms by Rietveld refinement of the synthesized composites. Micrographs obtained from FESEM characterization technique revealed the non-homogeneous grain and grain boundaries with no foreign impurities. In addition, energy-dispersive X-ray diffraction analysis (EDAX) confirms the presence of all the integral elements of the composite. Optical bandgap of the order of ~ 2.19 eV was estimated from the analysis of diffuse reflectance UV–Vis spectroscopy (DRS). Temperature-dependent dielectric properties of the synthesized samples were measured at different constant frequency values in the temperature range from 100 to 350 °C. A gradual increase in dielectric constant from 180 °C was shown by all the samples. Corresponding to different applied constant field values, the polarizability vs. electric field loop (P–E loop) of all composites displays leakage. This behavior is attributed to the volatile nature of bismuth ferrite. Magnetization vs. magnetic field (M–H) hysteresis loop characteristics obtained at room temperature revealed the anti-ferromagnetic nature for pure Bi0.9La0.1FeO3. Further, weak ferromagnetic property becomes dominant as BaTiO3 content increased in the composite.Article title: Kindly check and confirm the edit made in the title.ok [ABSTRACT FROM AUTHOR]

The thermal, structural, composition and morphology, optical, dielectric, and magnetic behaviors for the Ni0.5Fe0.5Co2O4 spinel cobaltite produced by sol–gel technique were studied in this work. The thermogravimetric analysis was used to investigate the temperature-dependent spinel phase formation of the sample and the percentage weight loss. The sample was well crystallized in the cubic spinel structure ( F d 3 ¯ m space group) according to Rietveld refinement of the XRD pattern. By using the UV optical absorbance, it has been shown that the compound revealed significant visible-light absorption. The estimated optical band gap energy was estimated as Egd = 2.78 eV. The dielectric results reveal that the sample has significantly higher electrical resistivity, making it suitable for microwave device applications. NSPT and CBH are the appropriate models which are used to explain the sample conduction process. The impedance and modulus studies show a dielectric relaxation mechanism in the sample. The interfacial polarization law of Maxwell–Wagner has been used to explain the change in dielectric constants. The Nyquist diagrams are well analyzed using an electrical circuit consisting of a connection of grain and grain-boundary elements. The obtained coercive field from the hysteresis loop is quite low in the present sample which would be suitable for soft magnetic device applications. [ABSTRACT FROM AUTHOR]

A solid-state reaction technique was used to make cerium (Ce) modified strontium manganite SrMn0.9Ce0.1O3 (SMCO). The Goldschmidt's tolerance factor of 0.95 and the Sure Independence Screening and Sparsifying Operator (SISCO) tolerance factor of 4.02, both are within the permissible range. SMCO's average crystallite size and micro-lattice strain were determined to be 59.6 nm and 0.439%, respectively. Analysis of the micrograph captured by the scanning electron microscopy (SEM) technique revealed the average grain size of 19.2 μm of the SMCO. The optical bandgap of the SMCO was found to be 4.53 eV for direct allowed transition for photovoltaic applications. The existence of + 4 oxidation state of both Ce and Mn in the SMCO has been ascertained by the X-ray photoelectron spectroscopic technique. The bulk resistance (Rb) decreases from 1.02 × 105 to 1.09 × 103 Ω on increasing the temperature supports the negative temperature coefficient of resistance (NTCR). The semiconductor nature of the material is further validated by the semicircular pattern of Nyquist and/or Cole–Cole plots. The observed change in activation energy with temperature proposes that the conductivity (σac) behavior of the material is due to the thermal activation phenomenon. The evaluation of the field-dependent polarization (P–E) hysteresis loop was also carried out to obtain the coercivity, remnant polarization, maximum electric field, and maximum (saturation) polarization which support the possibility of ferroelectricity in the material. The leakage–current plots between (log J versus log E) at selected temperatures support the existence of Ohmic conduction in the material at low voltages. [ABSTRACT FROM AUTHOR]

The effect of simultaneous substitution of La3+ and Fe3+ ions on structural, dielectric, ferroelectric and piezoelectric properties of BaTiO3 was studied. Polycrystalline ceramic samples with composition Ba1-xLaxTi1-xFexO3 with x = 0, 0.005, 0.015 and 0.020 were prepared by the solid-state route and sintered at 1325°C. X-ray diffraction (XRD) analysis confirmed the single phase with tetragonal perovskite structure in all the prepared ceramics. Dielectric constant 'ϵ' and tangent loss 'tanδ' was measured as a function of temperature (25–200°C). The value of ϵ increases with an increase in La and Fe contents. A very small value of tanδ (<4%) was observed. The temperature coefficient of capacitance 'Tcc' was found to be around 10% for all the samples. PE hysteresis loops were recorded at room temperature for all samples. The maximum value of ϵ and piezoelectric coefficient 'd33' was found to be 3735 (at 30°C, 100 kHz) and 140pC/N, respectively for x = 0.020. [ABSTRACT FROM AUTHOR]

The dynamic narrow system of ceramic [Na 0.5 Bi 0.5-x Nd x ] 0.94 Ba 0.06 Ti 0.95 Nb 0.05 O 3 (NBBTN: xNd) samples of Morphotropic Phase Boundary (MPB) compositions synthesized by traditional mixed oxide route reaction. A systematic investigation demonstrated that the introduction of Nd3+ ions improves relaxor behavior and decreases the tolerance factor. XPS studies reveal that oxygen vacancies are present and have a role in relaxation processes at elevated temperatures. The compounds' optical emission behavior showed excitation occurring at 785 nm. The infrared emission spectra of the compounds displayed a strong band in the wavelength range of 900 - 1500 nm. Concentration quenching occurs due to interactions between nearby Nd3+ ions, confirmed by the critical energy distance (discovered to be 9.78 Å) and Dexter's theory-based study of the NBBTN: xNd host system. The temperature-dependence dielectric analysis demonstrated the presence of ferroelectric and antiferroelectric transitions in two distinct regions. The ferroelectric hysteresis loop reveals a direct indication of changing ferroelectric character with Nd3+, by becoming ''softer'' with specimens exhibiting a decrease in remanent polarization (P r) and a smaller coercive field (E c). Based on these findings, Nd3+ doped NBBTN ceramics can be successfully applied in optoelectronic or integrated optoelectronic devices. [Display omitted] • The refinement employing dual phases revealed with space groups R3c and P4mm • The less distinct separation between the (002) and (200) diffraction peaks indicates a decrease in depolarization temperature. • The optical bandgap reduces with increasing concentration of Nd3+ RE ions. • The luminescence characteristics of NBBTN:xNd ceramics measured at IR-region with 785 nm pumping wave-length. • High dielectric constant and maximum polarization, reduced dielectric loss and Pr, suitable for battery storage applications. [ABSTRACT FROM AUTHOR]

The molten salt technique was employed to prepare the Aurivillius phases SrBi 2 Ta 2 O 9 (SBT) and Sr 0.9 La 0.1 Bi 2 Ta 1.9 Ti 0.1 O 9 (SLBTT). The XRD data and the Le Bail refinement approach demonstrate that both samples formed the double-layer Aurivillius phase with the orthorhombic A 2 1 am structure successfully. The SLBTT cell volume is smaller compared to SBT with the substitution of smaller La3+ and Ti4+ ions and the increased size of the plate-like grains. FTIR analysis indicates the two local arrangements of Ti4+ at the B -site to form Ti–O–Ti and Ti–O–Ta bonds. Changes in the structural properties due to La3+ and Ti4+ substitution are reflected in the electrical properties. The higher ferroelectric transition temperature (T c) of 455°C with the diffused phase transition behavior (DPT) was obtained in SLBTT. The unsaturated hysteresis loop of SLBTT obtained the ferroelectric remnant polarization (P r) of 0.43 μC/cm2 and the coercive field (E c) of 110.6 kV/cm, respectively. The enhanced ferroelectric characteristic as well as a higher bandgap (E g) that is driven by the substitution of variable smaller cations. [ABSTRACT FROM AUTHOR]

In this work, A series of nanocrystalline Ca–Ba–Co-based Y-type hexaferrite having general chemical formula CaBaCo2-xZnxNdyFe12-yO22 where x = 0.00 to1.0 and y = 0.00 to 0.1 were prepared using the sol–gel autocombustion technique. Prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), vibrating sample magnetometer (VSM), and dielectric measurements. XRD analysis of samples having various dopants concentrations in powder system matrix revealed that there was a single-phase pattern of Y-type hexaferrite. The measured structural parameters via lattice constants (a, c), unit cell volume Vcell, X-ray density (dx), bulk density (db), and porosity (P) were calculated through XRD data. FTIR (Fourier transform infrared) spectroscopy analysis showed the locations of ions including their corresponding bonds in the structure of the lattice matrix. It was observed that with increasing the Zn–Nd concentration the values of the dielectric parameters were decreased. At low frequency, due to surface charge polarization, the measurements of dielectric constant and dielectric loss were observed to be higher. Resonance peaks for all examined samples were also observed. Dielectric parameters consisting of impedance and modulus study attributed the presence of grains, while the grain boundaries might play a significant role in conduction mechanism. Magnetic characteristics measured from M–H (Hysteresis loop) curve that was measured from VSM represents that the prepared sample exhibits typical characteristics associated with the ferromagnetic substances. The calculated values for saturation magnetization and coercivity were found in the range from 25.8 to 51.1 emu/g and 0.061–0.063Oe. The increasing Ms and Hc values revealed that the prepared sample powder could be a leading candidate for PMR (perpendicular recording media) applications. Because of suppression of magnetic super exchange interaction anomalous behavior in magnetic parameters of Zn–Nd-doped was observed. The prepared samples with superb structural and magnetic characteristics are capable for high-frequency applications. [ABSTRACT FROM AUTHOR]

0.9Bi1-xNdxFeO3 − 0.1PbTiO3 solid solution with x = 0.05, 0.10, 0.15 and 0.20 were success fully synthesized by the standard solid-state reaction method. The effect of Nd3+ion substitution on structural, micro structural, ferroelectric, magnetic and dielectric properties of 0.9BiFeO3-0.1PbTiO3 have been investigated. The XRD analysis for the samples under study revealed distorted rhombohedral structure with R3C space group. 0.9Bi1-xNdxFeO3 − 0.1PbTiO3 i.e. (BNFPT)x with x = 0.05, 0.10, 0.15 and 0.20 compounds crystallized as single-phase materials with the same structure as the parent BiFeO3 compound. The SEM study revealed the uniform grain scattering for all prepared samples. Raman spectroscopy showed disappearance of some Raman modes indicated a structural phase transition with substitution of Nd dopants at Bi site and also confirmed the distorted rhombohedral perovskite structure of (BNFPT)x compounds with R3c symmetry. Dielectric measurements reveals that, around Neel temperature, all the samples exhibit magneto-electric coupling and also improved dielectric properties with addition of dopants in BiFeO3(BFO) compound. All the prepared samples exhibit weak ferro-magnetic character at room temperature. However, the variation in linear behavior and enhancement in magnetization is found at 5 K which shows gradual increase in remnant magnetization from 0.00785 emu/g to 0.37513 emu/g with increase in Nd doping for all (BNFPT)x samples. Nd doping reduces leakage current by three orders of magnitude, from 10−4 to 10−7. Ferroelectric study revealed the pinning effect in hysteresis loops with low remnant polarization and coercive field which can be related to the energy storage performance of the samples. [ABSTRACT FROM AUTHOR]

In this study, lead-free (Bi0.465Na0.465Ba0.07)1−xNdxTiO3 (x = 0.00, 0.01, 0.02 and 0.03) piezoceramics were prepared via conventional solid state mixed-oxide route. The role of A-site Nd3+ donor doping was investigated through systematic studies of crystal structure, morphology, dielectric, electrical conductivity and ferroelectric properties. The X-ray diffraction data revealed single-phase perovskite structure with pseudocubic symmetry for all samples. The morphology exhibited dense microstructure with the average grain size that tended to decrease with increasing x. Compared to undoped BNBT (x = 0), the dielectric loss (tanδ) at high temperature (> 350 °C) significantly decreased with increasing Nd3+ doping level. With increasing x, the impedance spectroscopy data revealed more electrically homogeneous microstructure with a significant increase in resistivity (ρ) from 3.98 × 10 4 Ω.m (BNBT) to 4.83 × 10 5 Ω.m at x = 0.02. In addition, Nd3+ doping can induce a transition from a square-like to a slant P-E hysteresis loop with a significant drop in coercive field (Ec) (from 25.81 for BNBT to 8.48 kV/cm for x = 0.03) and remanent polarization (Pr) (from 27.93 to 3.67 µC/cm2), corresponding to the ergodic relaxor. These results suggest A-site Nd3+ doped 0.93BNT-0.07 ceramic as a promising candidate for high temperature capacitors and actuator materials. [ABSTRACT FROM AUTHOR]

Solid state reaction was employed to synthesize the Bi1−xSrxFe1−xMnxO3 (x = 0.05, 0.10, 0.20, 0.25) ceramic materials. XRD reveals the single-phase rhombohedral structure with R3c space group of the prepared materials. The FTIR spectra have been used to calculate the Fe–O bond length. The UV–Visible diffuse reflectance spectra was used for the calculations of the band gaps, which are found to decrease from 2.02 to 1.83 eV on increasing the Sr and Mn co-doping in BFO. P-E loops were recorded for the samples to determine ferroelectric nature at various applied fields. M-H hysteresis loops show a significant change in remnant magnetization (Mr), saturated magnetization (Ms) and coercive field, (Hc) with Sr–Mn substitution in BiFeO3. From FESEM images revealed agglomerated particles in the samples investigated and an increase in grain size is observed with increase in co-doping in BiFeO3. Out of all the prepared samples, Bi0.90Sr0.10Fe0.90Mn0.10O3 with modified values of multiferroic parameters among the Bi1−xSrxFe1−xMnxO3 (x = 0.05, 0.10, 0.20, 0.25) may be useful as a promising multiferroic material for applications of actuators, sensors and multistate memory devices. [ABSTRACT FROM AUTHOR]

Dielectric elastomer actuators exhibit butterfly-shaped hysteresis effects under unbiased periodic input signals. In comparison with single hysteresis effects, butterfly-shaped hysteresis effects are more complicated, which include two single hysteresis loops, and the directions of both loops are different. Hence, it is a great challenge to build a hysteresis model to describe the butterfly-shaped behavior. To this end, a butterfly-shaped relay operator is newly proposed as an elementary operator to construct the butterfly-shaped Preisach model, and the weighting functions/weights of the developed model are positively defined, which facilitates the construction of the unique inverse model and the controller design. To further improve the modeling accuracy, a piecewise-defined butterfly-shaped Preisach model considering the variation of asymmetric nonlinear hysteresis effects with different input amplitudes is proposed. Experiments with the fabricated elastomer actuator-actuated system are conducted to validate the effectiveness of the developed modeling approach. [ABSTRACT FROM AUTHOR]

Multiferroic composite ceramics xNi0.15Cu0.25Zn0.6Fe2O4-(1-x) Ba0.85Ca0.15Zr0.1Ti0.9O3 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.9 and 1) were prepared by combining chemical co-precipitation method with sol–gel method; the microstructure, dielectric, ferroelectric, magnetic and multiferroic properties were comparatively investigated. XRD results show that all the specimens have obvious bi-phases structure. The grains with larger size are magnetic phase Ni0.15Cu0.25Zn0.6Fe2O4(NCZF), while that of smaller size can be attributed to ferroelectric phase Ba0.85Ca0.15Zr0.1Ti0.9O3(BCZT). The dielectric constant of the sample with x = 0.6 is the largest at low frequency but the specimen x = 0.2 has the highest value of dielectric constant in high-frequency region. When x = 0.9, the ceramic has the largest loss, while it presents the lowest loss value when x = 0.3. The height of the peak decreases with increase in the frequency, and the position of the peak moves to higher temperature range with the decrease in x. The dielectric loss increases sharply with temperature, especially when x = 0.9, when the temperature is higher than 300 °C, the dielectric loss reaches hundreds of times under low frequency. Al samples present apparent ferroelectric hysteresis loops, but further characterization shows that the hysteresis may be attributed to leakage current. The remnant polarization(Pr) and coercive field(Ec) do not monotonically change with x, Pr is 0.1576 μC/cm2 at 2 kHz when x = 0.6. The magnetization monotonically changes with the x, indicating that there is a strong interfacial interaction between the two phases. Under the action of an external magnetic field of 1 mT, the magnetoelectric (ME) coupling is the strongest (relative polarization change 37%) when x = 0.2. [ABSTRACT FROM AUTHOR]

To investigate the nonstoichiometric effect of (Bi 0.5 Na 0.5)TiO 3 (BNT) ceramics on their properties, we propose a novel chemical expression, (Bi 0.5+ x Na 0.5−3 x)TiO 3. The nonstoichiometric effect of BNT can be explored in compounds with this composition without being hampered by the charge imbalance problem. With x ranging from −0.02 to 0.02, we find that the morphological, dielectric, ferroelectric, and electrostrain properties differ considerably between Na-rich and Bi-rich ceramic samples. The average grain size (AGS) increased significantly in Na-rich samples compared to that in stoichiometric BNT, while it decreased slightly in Bi-rich samples. The dielectric characteristics measured from 30 °C to 500 °C indicate that conductivity is activated in Na-rich nonstoichiometric samples but is effectively suppressed in Bi-rich nonstoichiometric samples. The ferroelectric properties also show the same trend. In Na-rich samples, elliptical polarization against electric field (P - E) hysteresis loops were detected, indicating a conductive character induced by high electric field loading. However, saturated P - E loops are observed in Bi-rich samples with well-inhibited conductivity. Furthermore, compared to stoichiometric BNT and nonstoichiometric x = 0.02 Bi-rich samples, (Bi 0.5+ x Na 0.5−3 x)TiO 3 samples with x = 0.01 exhibit higher electrostrain from 30 °C to 150 °C. Based on the assumption of charge balance, our findings indicated that the presence of 1 mol% excess Bi would facilitate significant improvement in the dielectric, ferroelectric, and electrostrain properties of BNT and BNT-based systems. [ABSTRACT FROM AUTHOR]

M-type Hexa-ferrites powders of chemical composition Ba 0.5 Sr 0.1 Zn 0.4 Fe 12 O 19 was prepared by the use of the co-precipitation technique. The heat treatment of this ferrite composition was done at various temperatures (700, 800, 900, 1000, 1100, and 1200 °C) for 6 h. The X-ray diffraction (XRD) analysis of all the prepared powder samples confirmed the emergence of a hexagonal structure. The high-intensity peaks of the samples were indexed and showed a single phase. The size of crystallite was obtained within the range of 21–42 nm. The surface morphology was carried out with a Scanning electron microscope (SEM). The grain size showed the hexagonal shape, and average grain sizes were in the range of ~ 211 nm. Spectral information was found using the Fourier transform infrared (FTIR) spectroscopy to confirm the phase of M-type hexaferrite. The dielectric parameters were measured within the high-frequency range of 5 MHz - 3 GHz. The dielectric constant was increased with an increase in temperature. The dielectric studies were found by the establishment of space charge polarization as per the two-layer model provided by Maxwell-Wagner and the study of phenomena of Koop's theory. The magnetic characteristics including coercivity (HcB) and retentivity (Br) were measured from BH/JH hysteresis loops. The enhancement of coercivity was observed from 1.23 × 10+3 Oe to 1.50 × 10+3 Oe, while the retentivity increased from 1.334 × 10+3 G to 1.598 × 10+3 G with an increase in temperature. Outstanding properties of synthesized materials suggested their use in large-frequency applications, including recording media and permanent magnets. [ABSTRACT FROM AUTHOR]

A simulation-based study of the variability of remnant polarization $({P}_{r})$ in a multigranular 3-D ultrathin ferroelectric (FE) capacitor is presented in this article. The Poisson-Voronoi tessellation (PVT) algorithm is used for the nucleation of grains in the FE region, which corresponds to the physical growth mechanism. The PVT algorithm implemented in MATLAB is coupled with TCAD simulations, to trace the FE hysteresis loop. The impact of both, area and thickness scaling on the variability of ${P}_{r}$ , is considered. It is found that amount of variability in ${P}_{r}$ increases as FE thickness decreases. In addition, FE with the smaller surface area exhibits a higher variability in ${P}_{r}$ compared to a larger surface area FE capacitor. Furthermore, the impact of dielectric content in the FE grains is analyzed. It is seen that the dielectric grains cause a very large amount of variability in the FE hysteresis loop. An increase in the dielectric grains also leads to a loss in the retentivity of the hysteresis loop. [ABSTRACT FROM AUTHOR]

High-density polycrystalline ferroelectric ceramics having compositional formula Ba0.70Ca0.30Ti1−xFexO3, BCTF (with x = 0.000, 0.010 and 0.015) were prepared by solid-state reaction route. The samples were sintered at 1325 °C for 4 h. The samples were investigated for structural, dielectric, ferroelectric and magnetic properties. Raman and X-ray diffraction analysis confirms the tetragonal phase in all the samples. It can be observed from the dielectric versus temperature curves that all the prepared compositions showed a diffused phase transition. The Curie temperature was observed to be decreasing from 93 °C to 72 °C with the increase in Fe content. PE hysteresis loops were recorded at different electric fields. Pinched hysteresis loops were observed for all the samples, wherein, the pinching increased with the increase in Fe content. The energy density 'Ed' and efficiency 'η' were calculated from the PE loops. A high value of Ed = 0.15 J/cm3 with an efficiency of 67% was observed for the sample with x = 0.015 at 35 kV/cm. MH hysteresis loops were recorded at room temperature for all the prepared samples. The simultaneous observations of PE and MH hysteresis loops confirm the multiferroicity in the prepared samples. [ABSTRACT FROM AUTHOR]

Field effect transistors (FETs) using two-dimensional molybdenum disulfide (MoS2) as the channel material has been considered one of the most potential candidates for future complementary metal-oxide-semiconductor technology with low power consumption. However, the understanding of the correlation between the device performance and material properties, particularly for devices with scaling-down channel lengths, is still insufficient. We report in this paper back-gate FETs with chemical-vapor-deposition grown and transferred MoS2 and Zr doped HfO2 ((Hf,Zr)O2, HZO) high-k dielectric gates with channel lengths ranging from 10 to 30 µm with a step of 5 µm. It has been demonstrated that channels with the length to width ratio of 0.2 lead to the most superior performance of the FETs. The MoS2/HZO hybrid FETs show a stable threshold voltage of ∼1.5 V, current on/off ratio of >104, and field effect mobility in excess of 0.38 cm2 V−1 s−1. The impact of the channel lengths on FET performance is analyzed and discussed in depth. A hysteresis loop has been observed in the Ids − Vgs characteristics of the hybrid FETs, which has been further studied and attributed to the charge effect at the interfaces. The HZO films show a relatively weak ferroelectric orthorhombic phase and thus serve mainly as the high-k dielectric gate. Charge trapping in the HZO layer that might induce hysteresis has been discussed. Our results show that MoS2/HZO hybrid FETs possess great potential in future low power and high-speed integrated circuits, and future work will focus on further improvement of the transistor performances using ferroelectric HZO films and the study of devices with even shorter MoS2 channels. [ABSTRACT FROM AUTHOR]

Relaxor-PbTiO3 (PT-based) ferroelectric single crystals are important for many piezoelectric applications because of their outstanding performances. In order to expand their usage and avoid the failure during application, frequency dependence of coercive fields EC for [001]- and [011]-poled rhombohedral Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals was investigated from the frequency of 1 Hz to 300 kHz by using hysteresis loop measurement (frequency: from 1 Hz to 2 kHz) and a critical value method (frequency: from 5 to 300 kHz). The results showed that the coercive field EC, remnant polarization Pr, and saturation polarization Ps strongly depended on the crystal orientation and frequency. Compared with the [001]-poled crystals, the [011]-poled PIN-PMN-PT single crystals possessed higher EC, Pr, and Ps at the same testing frequencies. With increasing frequency from 1 Hz to 300 kHz, the coercive fields EC of the [001]- and [011]-poled PIN-PMN-PT single crystals increased from 4.0 and 4.8 kV/cm to 11.5 and 14.9 kV/cm, respectively. Moreover, the frequency dependence of the coercive fields was found to be consistent with the growth kinetics model, where the coercive fieldsEC were proportional to ƒβ. This work benefits to the design of piezoelectric devices based on PIN-PMN-PT single crystals operated at high frequencies and high driving fields. [ABSTRACT FROM AUTHOR]

At present, the control capability of dielectric barrier discharge (DBD) plasma actuation covers the flow velocity range of helicopter's retreating blades, so it is necessary to extend it to the dynamic stall control of rotor airfoils. A DBD plasma actuator was adopted to control the dynamic stall of an oscillating CRA309 airfoil in this paper. The effectiveness of alternating current (AC) DBD plasma actuation on reducing the area of lift hysteresis loop of the oscillating airfoil was verified through pressure measurements at a Reynolds number of 5.2 × 105. The influence of actuation parameters on the airfoil's lift and moment coefficients was studied. Both steady and unsteady actuation could effectively reduce the hysteresis loop area of the lift coefficients. The flow control effect of dynamic stall was strongly dependent on the history of angle of attack. Compared with the steady actuation, unsteady actuation had more obvious advantages in dynamic stall control, with reducing the area of lift hysteresis loop by more than 30%. The effects of plasma actuation on the airfoil's flow field at both upward and downward stages were discussed at last. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the magnetic, dielectric, and impedance properties of Ba2 − ySryZn2Fe12O22 (y = 0.0–1.5) hexaferrite prepared by solid-state reaction process. The magnetic hysteresis loop suggested that the prepared hexaferrite exhibits room temperature hard ferromagnetic activity. The saturation magnetization (Ms), remanence (Mr), and magneton number (nB) values are decreased with Sr2+ substitutional dopant at the Ba2+ site. On the other hand, Sr2+ doping enhances the β, Ha, and Ke values. The squareness ratio (Mr/Ms) is calculated to be 0.50, indicating the uniaxial anisotropy of BSZFO (y = 0.0–1.5) hexaferrite. Dielectric constant and dielectric loss values increased from 147 to 290 and 0.058 to 0.94, increasing Sr2+substitution from 0.0 to 1.5 at 1 MHz. This study has supported the rise in AC conductivity and decreases DC conductivity with the Sr2+ substitution. [ABSTRACT FROM AUTHOR]

The first concerned question on the fundamental physics of the resistive switching (RS) effect in metal/Nb-doped SrTiO3 junctions is whether the RS does take place at the whole interface or at some local regions of the interface. Even though several investigations provide the clues of the filamentary nature of the RS, direct evidences are still required. Moreover, there is obvious inconsistency between the possible filamentary feature and the observed capacitance-voltage (C-V) hysteresis loops. Here, we report direct evidences of a filamentary RS effect in Pt/Nb-doped SrTiO3 junctions. The virgin Pt/NSTO junctions show an initial RS effect. The current-voltage (I-V) characteristic of the initial RS and the C-V characteristic in the virgin junctions are interpreted by using the theory of metal/semiconductor contacts. The correspondence between the initial RS and the C-V hysteresis loops is also discussed. The most important is that an electroforming process is observed at a large forward voltage, which is a direct indication of the formation of conductive filaments across the Pt/NSTO interface. Following the electroforming, the Pt/NSTO junctions exhibit a filamentary RS effect. The I-V characteristic of the filamentary RS deviates from the theoretical prediction of metal/semiconductor interfaces. However, the C-V characteristic is almost the same as that of the virgin junctions. This demonstrates that the conductive filaments are formed at local regions of the Pt/NSTO interface and a majority of the interface remains invariant. The results clearly show that a filamentary RS effect occurs in the Pt/NSTO junctions and that the observed C-V hysteresis loops are not correlated to the filamentary RS. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]

Samarium modified SrBi4-xSmxTi4O15 (x = 0, 0.13, 0.43 and 0.78) ferroelectric ceramics of Aurivillius family were prepared by conventional solid state reaction method. X-ray diffraction studies confirm the formation of a single-phase. Microstructural images show randomly oriented palate-like structure. Broad dielectric peaks were found to obey the modified Curie-Weiss law. The overall inherent ferroelectric nature was explained on the basis of the Avrami model. Furthermore, with increasing the Sm3+ content, the grain morphology and diffusive parameters have shown a comprehending impact on the ferroelectric (hysteresis) behavior. [ABSTRACT FROM AUTHOR]

A series of Pb-free ferroelectric materials Ba 0.9 Sr 0.1 Ti 1-x Sn x O 3 (BSTS-x) with 0 ≤ x ≤ 0.15 was successfully prepared via solid-state reaction method. The effect of Sn substitution on the crystal structure, microstructure, dielectric behavior, ferroelectric and tunable features of BSTS-x ceramics were systematically investigated. Room temperature (RT) x-ray diffraction (XRD) analysis using the Rietveld refinement method reveals that all the synthesized BSTS-x ceramics were well crystallized into single perovskite structure. The results show a tetragonal phase for 0.00 ≤ x ≤ 0.02, which evolves to orthorhombic and tetragonal coexisting phases for 0.05 ≤ x ≤ 0.07. The composition x = 0.10 showed a mixture of tetragonal, orthorhombic and rhombohedral phases at RT, while a single cubic phase is observed for x = 0.15. The crystal phases determined by XRD were confirmed by Raman spectroscopy. Enhanced dielectric permittivity with a maximum value of ε ' ~35000 is observed for x = 0.10 at RT. The ferroelectric behavior of BSTS-x ceramics was investigated through polarization hysteresis loops and tunability measurements. High tunability of 63% at RT and under the low DC-applied electric field of 1.40 kV/cm is achieved for x = 0.10. [ABSTRACT FROM AUTHOR]

We investigate the influence of one-side-flat asymmetric degrees on vortex annihilation behavior in different chirality, clockwise or counterclockwise. The vortex annihilation fields are found to depend not only on the vortex chirality but also strongly on the degrees of asymmetry. The sequence of vortex annihilation from the flat to the round edges is observed in low asymmetric disks, and interestingly, the sequence is reversed in high asymmetric disks. Fast and non-contact vortex chirality detection can be realized in high asymmetric disks by analyzing hysteresis loop of focused magneto-optic Kerr effect on vortex annihilation. The experimental results agree well with the micromagnetic simulations. [ABSTRACT FROM AUTHOR]

We consider a model of a nanocomposite based on noninteracting spherical single-domain ferroelectric nanoparticles (NPs) of various sizes embedded in a dielectric matrix. The size distribution function of these NPs is selected as a part of the truncated Gaussian distribution from minimum to maximum radius. For such nanocomposites, we calculate the dependences of the reversible part of the electric polarization, the electrocaloric (EC) temperature change, and the dielectric permittivity on the external electric field, which have the characteristic form of hysteresis loops. We then analyze the change in the shape of the hysteresis loops relative to the particle size distribution parameters. We demonstrate that the remanent polarization, coercive field, dielectric permittivity maximums, and maximums and minimums of the EC temperature change depend most strongly on the most probable radius, moderately on the dispersion, and have the weakest dependence on the maximum radius of the NP. We calculate and analyze the dependences of pyroelectric figures of merit on the average radius of the NPs in the composite. The dependences confirm the presence of a phase transition induced by the size of the NPs, which is characterized by the presence of a maxima near the critical average radius of the particles, the value of which increases with an increasing dispersion of the distribution function. [ABSTRACT FROM AUTHOR]

(Pb0.89Ba0.08La0.02)(Zr0.50Sn0.40Ti0.10)O3 multi-layer antiferroelectric ceramics with uniform and dense microstructure were fabricated by a rolling process. The nature of AFE was proved by the double hysteresis loops and the double-butterfly C–V curves. High dielectric tunability was observed at low electric flied, as high as 24% at 11 kV/cm, or 2% per kV/cm, together with low dielectric loss. The results demonstrated that the rolling process is a feasible approach to fabricate multi-layer ceramics, and the multi-layer ceramics had a promising potential in tunable devices. [ABSTRACT FROM AUTHOR]

This article presents a systematic investigation on the frequency dependence of the discharge current $J_{g}$ versus the gap voltage $V_{g}$ in the atmospheric-pressure helium dielectric barrier discharges (DBDs) by means of numerical simulation based on a 1-D fluid model. The DBDs are excited by a sinusoidal voltage with frequencies from several tens of kHz to MHz. This article concludes the following. There is a characteristic frequency $f_{c}$ located in a range, smaller than the lower limit of which the $J_{g}$ – $V_{g}$ curve universally behaves as a pinched hysteresis loop, and higher than the upper limit of which it changes to a nonpinched one, and an estimation of $f_{c}$ has been given. Smaller than the lower limit of $f_{c}$ , in spite of its $J_{g}$ – $V_{g}$ pinched hysteresis loop, the discharge plasma part in the DBD cannot be described as a memristor, but exhibits a memory effect. With the increase in frequency, the $J_{g}$ – $V_{g}$ curves display two typical shapes similar to a hockey stick and a quasi-triangle, corresponding to a Townsend discharge and a glow discharge, respectively. Higher than the upper limit of $f_{c}$ , the $J_{g}$ – $V_{g}$ curve is no longer a pinched hysteresis loop, and its evolution with frequency is in a change between symmetry and asymmetry. These evolution behaviors of the $J_{g}$ – $V_{g}$ curves are mainly due to the charges remained in the gap when the frequency is higher. [ABSTRACT FROM AUTHOR]

Precise control of morphology of functional materials, in particular when grown on nanoscale has revolutionized their physio-chemical characteristics for various applications. These nano-dimensional materials serve as basic building blocks for the development of new technological applications. Here in, we synthesized a series of nanorods and nano flakes of Co/Ni spinel ferrites using a hydrothermal method. NH 4 F as a surfactant, assisted to precisely control the morphology and dimension of nanostructures. The transformation of inverse spinel structure of cobalt ferrite to mixed spinel upon Ni substitution remarkably influenced their dielectric and ferroelectric response. The increase of dielectric response with Ni substitution was explained on the basis of Maxwell Wagner model. The impedance investigation probed the activation of different electro-active regions in different frequency range. Ferroelectric behavior along with energy density calculation provided a map to estimate the potential of functional nanostructures for energy storage applications. Magnetic properties were also obtained at room temperature showing high coercive hysteresis loops. [ABSTRACT FROM AUTHOR]

A standard solid-state ceramic technology (i.e., high-temperature solid-state reaction method) was used to fabricate new bismuth layer Aurivillius compound, BiLa2TiVO9. The formation of a single phase with an orthorhombic structure was confirmed by the X-ray diffraction structural analysis. The tangent loss measured at 200 °C is found to be in between 0.03 and 0.05 in the frequency ranging from 1 kHz to 1 MHz. The dielectric constant is found to be around 300 at room temperature. The resistance and reactance parts of complex impedance have been determined by the complex impedance spectroscopy (CIS) techniques. The electric modulus spectroscopy study of the compound confirmed the presence of the short range displacement of charge carriers. Jonscher's power law fitting has been used to verify our experimental data of conductivity spectra. The nature of variation of exponent (n) obtained from the fitting follows the correlated barrier hopping as the predominant conduction mechanism in the sample. Room-temperature polarization loop confirms the ferroelectric nature of the sample. [ABSTRACT FROM AUTHOR]