Search

Structural, magnetic, and dielectric properties of x SrFe12O19-(1- x )Ba0.85Ca0.15Ti0.9Zr0.1O3 multiferroic composite prepared by sintering the composite mixture of sol-gel synthesized SrFe12O19 (SrF) and Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) are reported. Structural parameters (lattice parameter, bond length, and lattice strain) of parent phases in their pure and composite forms are correlated to indicate the lattice interaction between the two phases. The magnetic moment per gram of SrF ( M SrF ) in the composite is higher than that in the SrF, related to the changes in the Fe-O-Fe bond angles. The room temperature dielectric response of the composites in the 100 Hz–10 MHz frequency range is modeled by the Cole–Cole relaxation and Jonscher power law equations to mark the different contributions (ferroelectric dipoles, charge carriers). [ABSTRACT FROM AUTHOR]

Hybrid carbon nanostructures based on the sp2 hybridized allotropes of carbon, such as graphene and single-walled carbon nanotubes (SWCNTs), hold vast potential for applications in electronics of various forms. Electronic properties of such hybrid structures are modified due to the interaction between atoms of the components, which can be utilized to tailor the properties of the hybrid structures to suite the application. In this study, we have explored charge (electron) transport through the hybrid structures of single-layer graphene (SLG) and SWCNTs (both metallic and semiconducting) using the nonequilibrium Green's function formalism within the framework of tight-binding density functional theory. Our calculations show that the electronic transport in hybrid nanostructures is affected by the interactions between SWCNT and SLG in comparison to the individual components. The changes in the electronic structure and the transport properties with increasing interaction in hybrids (captured by decreasing the separation between SWCNT and SLG) are discussed, and it is demonstrated from this analysis that the hybrids with semiconducting SWCNTs and metallic SWCNTs show different behavior in the low bias regime while they show similar behavior at higher biases. The difference in the transport properties of hybrids with semiconducting and metallic SWCNTs is explained in terms of changes in the electronic structure, the local density of states, and the energy dispersion for electrons due to the interaction between atoms of the two components. [ABSTRACT FROM AUTHOR]

This communication presents the effect of Yttrium and Strontium doping on structural and electrocaloric characteristics of Bismuth Sodium Titanate. Bi0.25Na0.35Sr0.3Y0.1TiO3 electroceramics was synthesized by traditional solid-state mixed-oxide technique. The crystallographic phase formation was confirmed using the X-ray diffraction technique. Rietveld refinement was carried out to extract the unit cell parameters. Average particle size was estimated from the full-width half maxima of the strong XRD peak using Debye-Scherrer's equation. The temperature dependence of the maximum polarization obtained from P-E loops, the electrocaloric ability of the BNSYT is estimated by calculating the change in the entropy at a field of 6 kV/cm using the standard thermodynamics relation. [ABSTRACT FROM AUTHOR]

Structural and electric characteristics of Gd, Li and Sr modified Bismuth Sodium Titanate i.e. (Bi0.5Na0.5)0.6(Gd0.5Li0.5)0.2Sr0.2TiO3 (BNGLST) composition is demonstrated. BNGLST was synthesized by the solid-state mixed oxide method using the stoichiometrically weighed constituent oxides and carbonates. The homogenously wet mixed powder was calcined at 1000 °C for 12h and compressed pellets were sintered at 1250 °C for 2h. X-ray diffraction was carried out to confirm the phase formation. Crystallographic information was extracted from the Rietveld refinement of the XRD data. Dielectric measurement was carried out from room temperature to 300 °C at 1 kHz − 1 MHz frequencies. The a.c. conductivity associated with oxygen ion conduction is discussed in detail as a function of temperature and frequency. [ABSTRACT FROM AUTHOR]

The structural, dielectric and transport properties of modified Bismuth Sodium Titanate (BNT) are reported. Mn and Sr-modified BNT (Bi0.35Na0.35Sr0.3Ti0.9Mn0.1O3) was synthesized by a solid-state reaction route. Structural analysis based on Rietveld refinement of X-ray diffraction data confirms the single-phase characteristic without change of hexagonal crystal structure with R3C space group of BNT. The dielectric characteristics of the modified BNT are recorded in the frequency range of 20 Hz to 1 MHz at temperatures of 50 °C and 200 °C. Using the frequency-dependent, real and imaginary parts of the dielectric constant, ϵ′(ω)-ϵ″(ω) dipolar and hopping conduction-based carrier polarization properties are discussed. The dipole parameters such as relaxation time, static and high-frequency dielectric constant etc. are estimated by using Cole-Cole relaxation model. [ABSTRACT FROM AUTHOR]

This communication reports the effect of Iron (Fe) and Lithium (Li) co-doping on the structural, dielectric and electrical properties of Ba0.8Sr0.2TiO3; i.e. (Fe0.5Li0.5)0.1Ba0.7Sr0.2TiO3 (FLBST). The FLBST composite was synthesized by the solid-state mixed oxide method at 1400 °C for 12h. The crystalline phase formation has been confirmed by the X-ray diffraction technique and analyzed through the Rietveld Analysis using X'Pert Highscore plus software. From the XRD analysis, lattice parameters and the average crystallite size was calculated. The electrical properties of sintered (at 1450 °C for 2h) pellets were carried out in the temperature range of 30 °C–350 °C using impedance spectroscopy. Based on the real and imaginary part of the dielectric constant, i) the dipolar contribution which is dominant in 30 °C–150 °C is characterized by Curie-Weiss law and ii) contribution from defects and oxygen vacancies seen beyond 150 °C is described by Arrhenius equation. [ABSTRACT FROM AUTHOR]

Crystal structure and Dielectric properties investigation of lead-free Bi0.35Na0.25Li0.1Sr0.3TiO3 (BNLST) composite is reported. The required solid solution was synthesized using oxides and carbonates via the solid-state reaction method. The stoichiometrically weighed and mixed powder was calcined at 800 °C for 12 h, and the pellets were sintered at 1250 °C for 2 h. XRD measurements confirm the formation of single-phase rhombohedral perovskite structure and the crystal structure was refined using the X'Pert High-score plus software. The full-width half maxima of the XRD peak was used to compute the average crystallite size employing the Debye-Scherrer, Williamson-Hall, and Halder-Wagner techniques. The BNLST's dielectric measurements were performed as a function of temperature at five distinct frequencies in the range of 100 Hz–1 MHz. The phase transition temperatures are shifted toward room temperature with the doping of Li and Sr. The diffuseness parameters of the phase transition, the a.c. electrical conductivity and the activation energy are estimated for the BNLST composite. [ABSTRACT FROM AUTHOR]

Ultrafast nonlinear optical (NLO) characterization of ErFeO3 thin films deposited by the solgel assisted spin coating technique is reported herein. In the present investigation, we have used femtosecond (fs) pulses for studying the nonlinear absorption and refraction properties of ErFeO3 thin films. Intensity dependent open and closed aperture Z-scan experiments were performed on ErFO3 films in the visible and near-infrared wavelengths of 600 nm, 800 nm, and 1200 nm. To explain the observed NLO results, phenomenological models of simultaneous multi-photon and excited sate absorption are developed for three-level model systems suitable for excitation wavelengths with (600 and 800 nm) and without (1200 nm) linear absorption, respectively. Optical limiting (OL) characteristic is shown to exist through the phenomenon of two-photon absorption in a certain intensity range at the three wavelengths and under the simultaneous saturation of linear absorption at 600 nm and 800 nm. The upper limit of the intensity for OL applications is demonstrated by the saturation effect. The non-linear absorption results are correlated with the linear absorption at these wavelengths, which involves electronic transitions between Fe d- and O p-orbitals. [ABSTRACT FROM AUTHOR]

Recently, amorphous oxide semiconductors have gained significant interest due to their low-temperature processability, high mobility, and high areal uniformity for display backplanes and other large area applications. A multication amorphous oxide, amorphous indium gallium zinc oxide (a-IGZO), has been extensively researched and is now being used in commercial applications. It has been proposed that, in a-IGZO semiconductors, overlapping In-5s orbitals form the conduction path and the carrier mobility is limited due to the presence of multiple cations, which creates a potential barrier for the electronic transport. A multianion approach toward amorphous semiconductors has been suggested to overcome this limitation, and has been shown to achieve Hall mobilities up to an order of magnitude higher compared to multication amorphous semiconductors. In the present work, we compare the electronic structure and electronic transport in a multication amorphous semiconductor, a-IGZO, and a multianion amorphous semiconductor, amorphous zinc oxynitride (a-ZnON) using computational methods. Our results show that, in a-IGZO, the carrier transport path is through the overlap of outer s-orbitals of mixed cations, whereas, in a-ZnON, the transport path is through the overlapping Zn-4s orbitals, which is the only type of metal cation present. We also show that for multicomponent ionic amorphous semiconductors, the electron transport can be explained in terms of the orbital overlap integral, which can be calculated simply from the structural information. The orbital overlap integral has a direct correlation with the carrier effective mass, which is calculated using computationally expensive first-principles density functional theory based methods. [ABSTRACT FROM AUTHOR]

The electrical properties of thin-film transistors (TFTs) that use polymer-coated networks of single-walled carbon nanotubes (SWNTs) as the semiconductor with source and drain electrodes formed by high-resolution printing techniques. Studies of the scaling of properties with channel length and tube density reveal important information about the operation of the devices.

Combined electron transport and Raman studies on the reaction of u-bromobenzene diazonium tetrafluoroborate directly with singe and networks of SWNT transistors are discussed. It is found that metallic tubes on an average have higher reactivity toward diazonium reagents.

Dielectric and electrocaloric (EC) properties of sol-gel synthesized BaTi0.84Zr0.16O3 (BTZ) and La0.78Sr.0.22MnO3 (LSM) composite in 80:20 molar ratio is reported. We discuss the dielectric analysis based on the electric modulus M*(=1/ϵ*) with the aim to differentiate the orientational and interfacial/carrier contribution and to explain their temperature and frequency dependence. Frequency dependence of imaginary part of M, i.e., M″(ω) of the composite exhibits a broad relaxation peak in MHz range while ϵ″(ω) graph is typical of interfacial/carrier polarization dominated: ϵ″ is as high as 7k at 20 Hz, decreases to 300 at 2 MHz measured at 25°C. M″-max shifts to higher frequencies with the increase in the temperature. The M″-peak, associated with BTZ-dipoles, is fitted using Cole-Cole (CC) equation to estimate the dielectric parameters, static and high-frequency dielectric constants ϵs and ϵꝏ respectively, relaxation time, τ, and the CC parameter, α, which is related to the distribution of relaxation time. Temperature dependence of physical parameters obtained from the fitting reflected the attributes of orientational polarization of the parent BTZ. These analyses indicate that M* is a more suitable parameter to consider for the ferroelectric-ferromagnetic composites. [ABSTRACT FROM AUTHOR]

This article investigates piezoelectric materials for harnessing vibrational energy. A nano hollow cylindrical structure based on various piezoelectric materials was designed and utilised to generate the voltage. An accurate and efficient model is developed here, so as to optimized the efficiency of the piezoelectric energy harvester. This work analyses the piezoelectric actuator deflection and involves the Eigen frequency computation. A measurement methodology for investigating the mechanical and electrical behaviour of vibrational harvester's was modelled and analysed by finite element method using COMSOL software. The energy harvesting structure was developed and tested with different piezoelectric materials to attain appreciable voltage through a small deflection. The Simulated results predicts that for the same pressure range, different piezoelectric materials have the different output voltage and Eigen frequencies. The maximum voltage was observed for Barium Titanate (3.0847 V at 250 µm), along with poled Polyvinylidene fluoride. In addition, a comparison was made with different piezoelectric materials ideally suited to intelligent cantilever structure. For optimizing the performance of the piezoelectric energy harvester an accurate and efficient model is required, which was developed in this simulation study. A high voltage value with a small deflection through a cylindrical hollow structure was designed and tested using various piezoelectric materials in this study. [ABSTRACT FROM AUTHOR]

Mirco-Raman studies were used to examine the doping of individual single-walled carbon nanotubes through noncovalent adsorption of polyethylenimine, which converts p-type semiconducting nanotubes into n-type. Very different spectral responses in metallic SWNTs (namely, the appearance of Fano line shape and the concurrent enhancement of D-band) was found to have important implications on the intrinsic phonon line shape and therefore on the electron-phonon coupling.

Nanoscopic organic multilayers that serve as excellent gate dielectrics for thin film transistors using single-walled carbon nanotubes semiconductors are demonstrated. Results suggest the potential importance of new carbon-based electronic materials for high-performance logic circuit, displays, and other systems.