Contribution Of Grains Research Articles

Efficient Charge Storage Capability of BiFeO3-Based Bi-Phase Nanocomposites

Here, we report a facile synthesis of bi-phase nanocomposites of the form (1−x)BiFeO3−xPbTiO3 for their efficient utilization in modern day energy storage gadgets. X-ray diffraction confirmed the distorted rhombohedral structure of pure BiFeO3 while PbTiO3 exhibited tetragonal structure and hence confirmed the formation of nanocomposites. Morphological analysis revealed the reduction in particle size, improvement in bulk density and decrease in porosity with the increase of PbTiO3 contents. A wide dispersion in dielectric response was explained on the basis of Maxwell-Wagner model. A significant improvement in dielectric behavior was observed when PbTiO3 was added in the composite. The contribution of grains and grain boundaries in the electrical response of these composites was witnessed through impedance analysis. The nature of charge transport mechanism was established using electric modulus spectroscopy. These kinds of nanocomposites are recommended for the improvement of data storage capacity of devices as compared with phase-pure compounds.

Functional Properties of Donor (Al) and Acceptor (Cu) Codoped High Dielectric Constant ZnO Nanoparticles

In this work, we have synthesized donor‐acceptor (Al‐Cu) codoped ZnO nanoparticles with a doping concentration of 0%, 0.25%, 0.5%, and 0.75% by coprecipitation method. The synthesized samples were then annealed at 350°C and 600°C. All the samples showed wurtzite structure of ZnO with no secondary phase. The increase in doping concentration led to deterioration of crystalline quality, while improved crystallinity was observed at higher annealing temperature. The morphological study of these samples showed good grain‐to‐grain contact with less isolated pores. These samples were further characterized by impedance spectroscopy for analyzing dielectric properties. The values of the real part of dielectric constant and tangent loss showed decreasing trend with frequency. The appearance of semicircular arcs in the impedance complex plane plots indicates contribution of grains and grain boundaries and presence of different relaxation processes. 0.5% Al and Cu codoped ZnO showed the best dielectric response with a high value of dielectric constant and low tangent loss.

Microstructural and impedance studies of 0.72NBT-0.2ST-0.08KNN ceramic

Lead-free ternary 0.72Na0.5Bi0.5TiO3-0.2SrTiO3-0.08K0.5Na0.5NbO3 (NBT-ST-KNN) ferroelectric relaxor is prepared by conventional solid state reaction route. The ceramic with dense microstructure is studied by complex impedance spectroscopy over a temperature range from 400 °C to 650 °C. A clear contribution of grain and grain boundaries to the relaxation mechanism is confirmed from the Nyquist plot as a function of frequency and temperature and are investigated using empirical relations. The relaxation time is evaluated from Im Z* plot using Arrhenius law. Existence of two different activation energy values depicts the presence of two different relaxation processes. This investigation on complex impedance and ac conductivity values will provide useful information about the temperature and frequency dependent relaxation and conduction process.

Dielectric, impedance spectroscopy and hydroelectric phenomena in lanthanum doped bismuth ferrite (Bi0.85La0.15FeO3)

Multiferroic materials are fascinating to discover due to presence of more than two ferroic orderings in the same phase. The lanthanum doped bismuth ferrite (Bi0.85La0.15FeO3) multiferroic nanoparticles are synthesized by sol–gel technique. This 15 % substitution of La in BiFeO3 is chosen due to its improved structural and electrical properties. The structural and impedance properties of Bi0.85La0.15FeO3 has been reported successfully. X-ray diffraction studies and EDX analysis are done to investigate the structural properties. X-ray powder diffraction patterns confirm the formation of single-phase perovskite structure of Bi0.85La0.15FeO3 (BLFO). SEM-EDAX analysis indicates the circular grains in Bi0.85La0.15FeO3 with extensive agglomeration. The dielectric studies display conventional Maxwell-Wagner Polarization in the nanoparticles. Impedance spectroscopy confirms high resistance of BLFO as well as contribution of grains and grain boundaries in BLFO. The hydroelectric cell fabricated using BLFO nanoparticles display improved potential. These properties are owing to improved structural stability and suggest their use in hydroelectric cell application.

Raman, impedance spectroscopy and ferroelectric studies of Sn4+ doped PbZr0.52Ti0.48O3 ceramics

Sn doped Pb(Zr0.52Ti0.48)1-xSnxO3 (x = 0. 0.05, 0.1) were prepared by conventional solid-state reaction method. Raman spectroscopic studies confirm the tetragonal structural of the material. Impedance spectroscopic studies were carried out to understand temperature and frequency dependent properties which shows the non-Debye kind of relaxation process. Cole-Cole plots reveal the contribution of grain and grain boundary to the conduction process. The values of activation energy suggests that conduction is ionic in nature. AC conductivity was found to obey the Johnscher’s power law. Ferroelectric studies were carried out and it was observed that the values of remnant polarization (Pr) increased with Sn substitution.

Superparamagnetic contributions, optical band gap tuning and dominant interfacial resistive mechanisms in ferrites nanostructures

Nanocrystalline Ni-Zn ferrite nanoparticles (NPs) NixZn1−xFe2O4 have been synthesized followed by detailed analysis of compositional effects on morphology, crystalline phase formation, lattice constant, crystallite size, magnetic, optical and dielectric properties describing the underlying physics as well. Cubic spinel structure with (311) preferred orientation and switching trend in crystallite size variation with gradual decrease in lattice parameter (from 8.377 to 8.323 Å) with the increase in nickel content has been observed through calculations. The magnetic behavior of NPs has been investigated at lower temperatures up to 5 K illustrating significantly improved magnetic parameters including Ms = 36.8 emu/g, Mr = 3.61 emu/g, SQ = Mr/Ms = 0.1028, Hc = 115.33 Oe, μB = 1.5664 emu, and K1 = 2122.18 erg/g. This enhancement has been found possibly due to less thermal fluctuations and significant superparamagnetic contributions from the very small fine nanoparticles being in blocking state owing to such a cool environment. Optical band gap for both direct (1.74–1.39 eV) and indirect (1.25–1.16 eV) transitions shows decreasing trend with the increase in Ni contents probably due to the redistribution of Ni or Zn contents from octahedral to tetrahedral site. Dielectric constant (real and imaginary) and tangent loss decreased with the increase of frequency, this refers to the Maxwell-Wagner type of polarization in the material in accordance with Koop’s theory, however, a switching is observed at the stoichiometric ratio of x = 0.25 and 0.75. The impedance (Z′) has maximum value 5539 kΩ at x = 0.75 and a minimum value 682 kΩ at x = 1.0. The Nyquist plot pointed out the contribution of grain boundaries, however the contribution varies with the stoichiometric ratio x. The Cole-Cole plot confirms the contribution of grains in the material for all value of x.

Studies of Structural, Electrical, and Magnetic Characteristics of Double Perovskite Ceramic: La2FeMnO6

Herein, detailed studies of structural, electrical, and magnetic characteristics of a double perovskite lanthanum iron manganate (La2FeMnO6) are reported. From the Rietveld analysis of X‐ray diffraction data and pattern, the orthorhombic structure of the compound is determined. The least‐squares refined lattice parameters of the compound are: a = 5.5370 Å, b = 7.7988 Å, and c = 5.5069 Å. The frequency–temperature dependence of the dielectric parameters is explained by the Maxwell–Wagner model to provide the polarization mechanism. Analysis of temperature dependence of impedance and modulus data of different frequency has shown the contributions of grains and grain boundaries in the electrical characteristics of the material. This analysis also shows the semiconductor characteristics, through a negative temperature coefficient of resistance nature. Based on both impedance and modulus spectroscopy, the dielectric relaxation process is found to be of a non‐Debye type. The study of scaling behavior of impedance and modulus data suggests that relaxation phenomena are nearly independent of temperature. Detailed analysis of the frequency dependence of conductivity data of different temperatures using the Jonscher's power law has shown the existence of different types of conduction mechanisms in the material. The nature of the current–voltage (I–V) curves suggests that the material behaves as a semiconductor diode type to be used for the rectifying purpose. The conduction mechanism follows the space charge‐limited conduction (SCLC) process which is obtained from leakage current analysis. The study of magnetic hysteresis of the material suggests that the material exhibits soft ferromagnetic ordering.

Microstructures and Electrical Conduction Behaviors of Gd/Cr Codoped Bi3TiNbO9 Aurivillius Phase Ceramic.

In this work, a kind of Gd/Cr codoped Bi3TiNbO9 Aurivillius phase ceramic with the formula of Bi2.8Gd0.2TiNbO9 + 0.2 wt% Cr2O3 (abbreviated as BGTN−0.2Cr) was prepared by a conventional solid-state reaction route. Microstructures and electrical conduction behaviors of the ceramic were investigated. XRD and SEM detection found that the BGTN−0.2Cr ceramic was crystallized in a pure Bi3TiNbO9 phase and composed of plate-like grains. A uniform element distribution involving Bi, Gd, Ti, Nb, Cr, and O was identified in the ceramic by EDS. Because of the frequency dependence of the conductivity between 300 and 650 °C, the electrical conduction mechanisms of the BGTN−0.2Cr ceramic were attributed to the jump of the charge carriers. Based on the correlated barrier hopping (CBH) model, the maximum barrier height WM, dc conduction activation energy Ec, and hopping conduction activation energy Ep were calculated with values of 0.63 eV, 1.09 eV, and 0.73 eV, respectively. Impedance spectrum analysis revealed that the contribution of grains to the conductance increased with rise in temperature; at high temperatures, the conductance behavior of grains deviated from the Debye relaxation model more than that of grain boundaries. Calculation of electrical modulus further suggested that the degree of interaction between charge carriers β tended to grow larger with rising temperature. In view of the approximate relaxation activation energy (~1 eV) calculated from Z″ and M″ peaks, the dielectric relaxation process of the BGTN−0.2Cr ceramic was suggested to be dominated by the thermally activated motion of oxygen vacancies as defect charge carriers. Finally, a high piezoelectricity of d33 = 18 pC/N as well as a high resistivity of ρdc = 1.52 × 105 Ω cm at 600 °C provided the BGTN−0.2Cr ceramic with promising applications in the piezoelectric sensors with operating temperature above 600 °C.

Influence of La doping on structure, AC conductivity and impedance spectroscopy of Ba2SnO4 Ruddlesden Popper oxide

A few compositions of (Ba1-xLax)2SnO4 with 0≤x≤0.10 have prepared via solid-state ceramic route followed by calcination at 1000 °C for 8 h. The preliminary phase of samples has analyzed using XRD and found to be crystallized into tetragonal structure up to 4 atoms %. The solubility limit of La at Ba-site has reconfirmed using FTIR and Raman analysis. The AC conductivity spectra of single-phase samples follow universal Jonscher's power law σac=σdc(1+(ffh)n). Further, the thermal dependence of dc conductivity (σdc) and hopping frequency (fh), indicating the presence of Arrhenius type charge transport in the samples. Ghosh scaling applied to σac of all temperatures found to superimpose on a single master curve, indicates the invariance of conduction mechanism. The impedance spectroscopy studies reflect the major contribution of grain in the conduction and relaxation process of all sample. Based on present study, the present material can be potentially used in semiconductor devices, UV-detector, and mixed ionic and electronic conductor (MIECs) by utilizing absorption states and thermo-curves as metastable state.

Co-ferrite nanostructures prepared by solvothermal route; new ultra-low k dielectrics

Co spinel ferrite nanoparticles were successfully prepared using a solvothermal route. Their structure, morphology and cationic distribution were studied by X-ray diffraction, Transmission Electron Microscopy and 57Fe Mössbauer Spectrometry. Though, their electric conductivity and dielectric relaxation were studied on nanostructured pellets resulting from the compaction of nanoparticles, by complex impedance spectroscopy in the frequency range 1–106 Hz from 25 up to 250 °C. The dielectric properties are investigated in detail. The presence of two thermally activated relaxation peaks in the modulus loss spectra confirms the contribution of grains and grain boundaries to the electrical behavior of the material. The main dielectric relaxation comportment and the conduction process are governed by the grain boundaries. Ac-conductivity, which deviates from the usual Universal Dielectric Response, can be described by a double power-law evidenced by a Nearly Constant Loss trend followed by a Super-Linear Power Law that decreases with increasing temperature. The change in the cationic distribution in CoFe2O4, deduced from the 57Fe Mössbauer spectra, may explain the observed trend in conductivity. The classical dielectric relaxation behavior is observed and very low values of permittivity are estimated. This compound can therefore be classified as an ultra-low-k dielectric.

Study of Charge Transfer Mechanism and Dielectric Relaxation of CsCuCl3 Perovskite Nanoparticles

Non-toxic inorganic metal halide perovskites have commercially established dominance over all the other optoelectronic devices. In this paper, a non-toxic CsCuCl3 metal halide is successfully synthesized through the slow evaporation solution growth technique. The hexagonal phase of the material is checked using the X-ray diffraction measurement. The morphological study indicates the spherical shape of nanoparticles with about 20 nm size. CsCuCl3 demonstrates a semiconducting property with a direct band gap value of approximately 2.18 eV. Over the 10−1–107 Hz frequency range, the dielectric constant, the loss factor, the electric modulus and also the electrical conductivity of CsCuCl3 show strong temperature dependence. The Nyquist plot confirms the various contributions of grains and grain boundaries to the total impedance. In the high-frequency region, the dielectric constant tends to increase with temperature. The modified Cole–Cole plot asserts that while the relaxation time decreases with the rise in temperature, the space charge and free charge conductivity increase the moment the temperature climbs. In accordance with the modified Kohlrausch-Williams-Watts (KWW) equation, an asymmetrical nature corresponding to the non-Debye type of the perovskite is noticed in the electric modulus spectra at different temperatures. Moreover, the imaginary part of the electric modulus spectra is found to shift from the non-Debye toward the Debye type with the increase in temperature despite not getting the exact Debye response and emerging as a semi-conductor material. The alternating current (AC) conductivity of CsCuCl3 is shown based on the non-overlapping small-polaron tunneling (NSPT) mechanism. The fact that the direct current (DC) conductivity matches well with the activation energy which is based on the two modulus spectra indicates that the relaxation behavior and the conduction mechanism are remarkably similar. Additionally, CsCuCl3 is likely to be an energy-harvesting device since it has a high dielectric constant related to its low dielectric loss.

Effect of La/Cr co-doping on dielectric dispersion of phase pure BiFeO3 nanoparticles for high frequency applications

Abstract Energy storage materials play a vital role in modern technology. A single device can perform multifunctions if fabricated using a multifunctional material like BiFeO3. For this purpose, a series of La and Cr doped BiFeO3 was synthesized using sol‒gel auto-combustion technique. A single phase rhombohedral distorted perovskite crystal structure related to bismuth ferrite with space group R3c (161) was confirmed from the X-ray diffraction patterns. Doping of La/Cr at Bi/Fe lattice sites in BiFeO3 did not affect the crystal symmetry of the parent compound. Morphological analysis exhibited homogeneous micro structures showing uniform distribution of multi-shaped grains with decreasing porosity and grain sizes with increasing Cr contents. These materials exhibited the conventional ferrite-like dielectric response, which gradually decreased with increasing frequency and lastly became constant in the high frequency regime. Impedance spectroscopy revealed the contribution of grains, grain boundaries and interfaces in electrical response of the samples. Frequency dependent electric modulus analysis confirmed the non-Debye type relaxation.

Effect of annealing temperature on dielectric properties of iron oxide prepared by sol–gel auto combustion method

In this study, different phases of iron oxide have been synthesized by sol–gel auto combustion route followed by annealing. Temperature and frequency-dependent dielectric properties have been studied in detail which provide the information on the contribution of grain and grain boundary in charge transport. Conductivity and electric modulus spectra have also been analyzed. The scaled coordination of impedance spectrum merges in a single master curve which signifies that the distribution of relaxation time is temperature independent. Complex impedance spectra have been used to evaluate activation energy (Ea ) by using Arrhenius relation. The activation energy calculated for α-Fe2O3 is 1.36 eV.

Abstract P135: Dietary Sources Of Linoleic Acid (LA) Differ By Race/ethnicity In Adults Participating In The National Health And Nutrition Examination Survey (NHANES) Between 2015-2016

Background: Linoleic acid (LA), a primary polyunsaturated fatty acid, is a nutritional quandary as has been associated with diabetes and cardiovascular disease (CVD) protection but may have negative effects in inflammation and cancer. Objective: To determine whether the relative contributions of nine food sources (dairy, eggs, select fats and oils, fish, fruit, grains, meat, nuts, and desserts) to overall LA intake differ by race / ethnicity in the adult US population. Methods: We included all non-pregnant, non-lactating adults (< 20 years, ~50% female) with plausible dietary data (average daily caloric intake ≥600 kcals/day and ≤6000 kcals/day; N=3,884). The percentage of LA calories attributable from each of the nine food groups was calculated. Linear regression models, incorporating survey weights, examined differences by race/ethnicity and included age, gender, income level, highest level of education and daily caloric intake as covariates, with a post-hoc Tukey test applied to group comparison. Significance was set at Bonferroni corrected P≤.006. Results: Across the population as a whole, 7.14% of the overall caloric intake was attributable to LA. Grains contributed to the highest percentage of LA intake (29%) followed by meat (18%), with fish contributing the least (4%). Significant differences in the relative contribution of almost all food sources to overall LA were found across race/ethnic groups (all except dairy; Table 1). Fruits and Grains showed the greatest number of differences by race/ethnicity, with NHBs reporting the greatest intake contribution of fruit to LA intake (14.8%) and MAs the lowest (9.6%; P<.001 for the difference; Table 1). This pattern was reversed when looking at the contribution of grains to overall LA intake (25.9% vs 41.2% respective; P<.001; Table 1). Conclusions: Our findings suggest that the foods contributing to overall LA intake differ across race/ethnic groups. Interventions designed to alter LA intake may benefit from tailoring to a population’s ethnic/race distribution.

Impedance spectroscopy and magneto-dielectric analysis of La3+ substituted Co2Z hexaferrite

Single phase Ba3Co2Fe24O41 (Co2Z) and Ba2.8La0.2Co2Fe24O41 (La-Z) were prepared by solid state ceramic method. The dielectric, impedance and electric modulus were systematically investigated as a function of temperature from 50 °C–250 °C and in the frequency range of 1 Hz–1 MHz. Frequency dependent imaginary impedance and electric modulus implies that La3+ substitution significantly affect hopping and relaxation mechanism of charge carriers. Cole-Cole plots (Z" vs Z') has been fitted with suitable equivalent circuit for both Co2Z & La-Z. The obtained grain and grain boundary resistances confirmed that charge carriers experienced lower resistance in La-Z. Arrhenius plots of relaxation time (τ) vs 1/T showed parallel conduction mechanism in system. Complex electric modulus spectrum distinguished the capacitive contribution of grain, grain boundary and electric effect. A very high magnetodielectric effect at low frequencies has been observed for La-Z.

Electrical and Dielectric Characterization of Bismuth Holmium Nickel Titanate (BiHoNiTiO6)

A lead-free multiferroic double perovskite BiHoNiTiO6 (BHNT) was prepared at high temperature following mixed oxide solid state reaction mechanism. Structural evaluation by X-ray diffractogram suggested monoclinic crystal system for the BHNT. SEM images showed homogeneous morphology with almost similar and uniform grain distribution. The compound possessed low value of tanδ even at a high temperature (400oC) at 100 kHz. Evaluation of the dielectric and electrical plots with frequency and temperature obtained from the impedance spectroscopy revealed that the contributions of grains, grain boundaries and electrode has profound effect on the above properties. These plots are very much helpful to understand the conduction mechanism and microstructure characteristics of the electronic material. The experimental real and imaginary impedance data were modelled by designing an equivalent circuit with the capacitance and resistance parameter. The transport characteristics like σac (ac conductivity), electrical modulus and magneto-electric effect of the material were also reported in this paper.

A green approach for the preparation of nanostructured zinc oxide: Characterization and promising antibacterial behaviour

In the present study, nanostructured zinc oxide (ZnO) films have been successfully synthesized using fruit extract of Viburnum opulus L. (VO) on glass slides by successive ionic layer adsorption and reaction (SILAR) procedure. The impact of VO concentrations on the structural, morphological, optical, electrical, and antibacterial attributes of ZnO films has been investigated in detail. The samples' XRD patterns present a hexagonal crystal structure with a preferential orientation along the (002) plane. The crystallite size values of ZnO samples were found to be in the ranges from 14.88 to 9.23 nm. The supplementation of VO to the synthesis solution remarkably affected the surface morphological features of the ZnO films. The optical results demonstrated that band gap energy values of the ZnO films at room temperature were decreased from 3.20 to 3.07 eV as a function of VO content in the bath solution. The films' electrical properties were determined by impedance analysis in the frequency range of 20 Hz −1 MHz. Impedance-frequency measurements showed VO insertion to ZnO thin films cause an increase in impedance value at the low frequencies. Cole-Cole plots with a single semi-circle confirmed the contribution of grain and grain boundary for the electrical conduction process. The agar disk diffusion method was used to test the antibacterial properties of ZnO/VO inserted ZnO and inhibition zones were measured. VO inserted ZnO showed a stronger inhibitory effect on gram-positive bacteria Staphylococcus aureus (ATCC 25923) and gram-negative bacteria Escherichia coli (ATCC 35218) than ampicillin antibiotic used as a control group. In line with the promising bactericidal results of a new generation, VO inserted ZnO, the nanostructured product with this study, it can also be applied in multidrug-resistant clinical isolates obtained from patients.

Origin of ferroelectricity in multiferroic ErFeO3

ErFeO3 is a centrosymmetric Pnma/Pbnm structure with no ferroelectricity. However, most surprisingly, it shows ferroelectricity and antiferromagnetism at room temperature. Here, the Fe3+-O-Fe3+ bond angles are 143.50 and 159.280 which is deviated from 1800. This Fe3+-O-Fe3+ super-exchange interaction contributes to an AFM ordering with a weak FM component. An antisymmetric DM exchange interaction (Di. Si x Sj) is attributed to the weak FM component between adjacent spins and introduced spin-orbit interaction. As a result an electric polarization P ~ eij x (Si x Sj) is produced due to local crystal anisotropy. To acquire a conception involving the contribution of grain and grain boundary of ErFeO3, we have analyzed complex impedance and modulus spectra and fitted with the equivalent circuit diagram. The imaginary part of electric modulus is fitted by KWW function and the stretched exponent is found to be 0.3<β< 0.48. The conduction mechanism of ErFeO3 is followed CBH model.

Effect of Polaron formation in conduction and dielectric behavior in La0.7Sr0.25K0.05MnO3 oxide

The purpose of this paper is to analyze the dielectric properties of La0.7Sr0.25K0.05MnO3 (LSKM) using impedance spectroscopy over the frequency range of 100 Hz to 1 MHz at different temperatures from 260 to 380 K. In fact, the dielectric analyses of the sample showed two relaxation processes at different relaxation times related to the effect of microstructural inhomogeneities and the contribution of grain and gain boundaries. However, Ac conductivity behavior reveals a metal–semiconductor phase transition at a specific temperature TM-S = 260 K and showed an important impact of the electron–lattice interaction in polaron formation. Also, the conductivity curve is analyzed by Johnscher’s universal power law and the variation of the exponent ‘n’ with temperature suggests the domination of small polaron hopping (SPH) model governed by an activation energy Ea = 0.12 eV. Further investigations using modulus formalism proved the presence of electrical relaxation, which is in good agreement with impedance results. The dielectric poly-dispersive behavior is related to the conduction process and the large value of the dielectric constant $$\varepsilon^{\prime\prime}(\omega )$$ in the order of 106 is correlated to the Maxwell–Wagner relaxation.

Investigation of crystal structure, dielectric response and magnetic properties of Tb3+ substituted Co2 Y-type barium hexaferrites

Y-type hexaferrites powder samples of Ba1·8Sr0·2Co2Fe12-xTbxO22 (with x = 0.0, 0.1, and 0.2) were prepared by the method of sol-gel auto combustion. XRD and Rietveld refinement analysis shows that the prepared Y-type hexaferrites samples exhibit pure crystalline phase with the absence of impurity. FTIR study gives an idea of the formation of Y-type hexaferrites by the appearance of three characteristics bands at 409, 433, and 552 cm−1. FESEM analysis shows plate-like morphology with the presence of all hosts and substituted elements observed in the EDX spectra and mapping. The grain size decreases with increase in the concentration of Tb3+, the particle size was observed to be in the range 56.48–58.54 nm. Typical dielectric response of ferrites was observed in the dielectric analysis. Cole-Cole plot shows that the contribution of grain is negligible compared to grain boundaries contribution. The multi domain magnetic nature of the prepared Y-type hexaferrite samples resulted in domain wall displacement and consequently influences the values of the coercivity.