Modulus Spectroscopy Studies Research Articles

Structural, raman, optical and electrical studies of pure and compound crystal of magnesium sulphateheptahydrate and threonine

Pure and compound crystal of magnesium sulphate heptahydrate(MSH) and threonine (THR) is grown from aqueous solution by slow evaporation method at room temperature. The reaction between MSH and THR is confirmed by TLC test. Good quality and transparent crystals are harvested. Pure MSH and THR crystallize in orthorhombic crystal system, while compound crystal shows the presence of both the phases of MSH and THR.The crystallite size is found using the various methods are employed to estimate the crystallite sizes and the lattice strain. The Raman spectra show the presence of characteristic normal modes of vibrations of pure MSH and THR in the compound crystal.The optical band gap is estimated by using K-M function. The various optical parameters such as extinction coefficient, refractive index, optical conductivity and skin depth have been calculated and analyzed with incident photon energy. The dielectric constant and loss of all the grown crystals have exhibited normal behavior over the frequency range considered. The total polarizability of the crystals is calculated by two theoretically methods and matches well with experimental results. The complex impedance and modulus spectroscopy studies suggested the presence of grain effect in all the samples and the same is successfully modelled using R-CPE parallel circuit. Non-debye type relaxation is confirmed from β-parameter. From the Jonscher’s plot, the ideal long range pathways and diffusion limited hopping mechanism is confirmed for all the samples. The results of pure crystal of MSH and THR are compared with the compound crystal and discussed accordingly in detail.

Dynamic electric, dielectric, impedance, and modulus spectroscopy study with Rietveld refinement of Al-substituted NiCuZn bulk ceramics

Dynamic electric, dielectric, impedance, and modulus spectroscopy study with Rietveld refinement of Al-substituted NiCuZn bulk ceramics

Structural and modulus spectroscopy studies of Bi0.5(Na0.8K0.2)0.5TiO3 nano-polycrystalline ceramic

Structural and modulus spectroscopy studies of Bi0.5(Na0.8K0.2)0.5TiO3 nano-polycrystalline ceramic

Impedance and modulus studies of Pb(Fe0.5Nb0.5)O3–Pb(Co0.33Nb0.67)O3 solid solutions

The high quality polycrystalline (1-x)Pb(Fe0.5Nb0.5)O3(PFN)–(x)Pb(Co0.33Nb0.67)O3(PCN) (abbreviated as PFCN) ceramic solid solutions (x = 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized via single-step solid-state reaction technique. The formation of a single-phase, monoclinic structure with Cm symmetry and without any secondary phase was confirmed through the room temperature (RT) X-ray diffraction (XRD). The microstructure of sintered ceramics with well-grown grains having average grain size of 1–2 µm were observed through scanning electron microscopy (SEM). To understand the electrical response of the material impedance and modulus spectroscopy studies were carried out. A detailed temperature (301–481 K) and frequency (100 Hz to 6 MHz) dependent impedance and modulus of PFCN ceramic solid solutions were reported. The impedance spectroscopy reveals the increase of conductivity in the system by the addition of Pb(Co0.33Nb0.67)O3 due to increased number of oxygen vacancies (OVs)/defects created at the grain boundary interface during the synthesis. The Z′ vs. frequency shows the creation of space charges by the participating ionized OVs in the conduction process and Z′′ vs. frequency shows the presence of temperature-dependent relaxation processes in the PFCN solid solutions. The Nyquist plot (Z′′ vs Z′) shows the depressed semicircles suggesting the deviation from Debye type of relaxation behaviour and a decrease in the grain resistance for all compositions with rise in temperature, correlates the NTCR (negative temperature coefficient of resistance) nature. The M′ vs. frequency display the step-like behavior due to dipole contribution to the modulus present in the grain and grain boundary region. Fitted Kohlrausch-Williams-Watts (KWW) function to M′′ vs. frequency demonstrates the non-Debye type relaxation behavior in the PFCN solid solutions. The mismatch of fmax in the Z′′, M′′ vs. frequency indicates the short-range mobility of localized charge carriers.

Rietveld refinement structure, electric, dielectric and ferroelectric properties of lead-free Ba0.985Sr0.015Zr0.10Ti0.90O3 ceramics

Ba0.985Sr0.015Zr0.10Ti0.90O3 (BSZT) compound is prepared using the standard solid-state reaction technique to explore for energy storage applications. Samples prepared from this compound are sintered at various sintering temperatures (Ts) of 1200, 1250 and 1300 °C, respectively. Influences of Ts on the structural, morphological, dielectric and ferroelectric properties are studied in detail. Rietveld refinement is used on the X-ray diffraction pattern to confirm the crystal structure of the BSZT samples and each sample indicates the tetragonal phase with the P4mm space group. Interestingly, with increasing Ts, the tetragonality increases up to 1250 °C, and then decreases for further increasing Ts, suggesting a transformation to the cubic structure. Morphological analysis of the BSZT samples show that a dense microstructure is attained for higher Ts. Temperature-dependent dielectric studies show that the degree of diffuseness increases up to 1250 °C, and then decreases for further increasing Ts, suggesting a weakening of the relaxor ferroelectric behavior. A non-Debye type relaxation process in the complex impedance and the modulus spectroscopy studies confirm the significant contribution of both the grain and grain boundary to the electrical response of the studied sample. The ferroelectric behaviors of the sample are explored from the polarization versus electric field hysteresis loops. Ferroelectric properties are significantly improved with the Ts.

Structural, dielectric, impedance and modulus spectroscopy of BiLa2TiVO9 ceramic

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.

Enhanced magnetoelectricity in bismuth substituted SrFe12O19 hexaferrite

M-type bismuth doped strontium hexaferrite Sr1 − xBixFe12O19 (x = 0, 0.01, and 0.02) is prepared by the sol-gel auto-combustion method and studied for magnetoelectricity. The lattice of the x = 0.01 sample is found to be highly strained compared to the other two compositions. The enhancement of strain is also accompanied by an increase in magnetization by 6%. Impedance and modulus spectroscopy studies suggest a transition in relaxation mechanism from grain dominated (below 150 K) to grain boundary dominated (above 150 K). The grain related capacitance for x = 0.01 is found to be ∼50 nF, and this value is ∼10 times higher than the other two samples. The linear magnetoelectric coefficient α d (in mV c m − 1 O e − 1) for the parent x = 0 sample is found to be 0.33 at 125 K, and this value decreases gradually to 0.27 at 300 K. The x = 0.01 sample displayed the highest (even 10% higher than the x = 0 sample) value of α d at low temperature. Unfortunately, the increased value of α d is also accompanied by a drastic reduction in its magnitude for temperatures higher than 200 K, due to the increased electrical conduction which in x = 0.01 is ∼94% higher than the parent.

Thermal response of dielectric, impedance and modulus spectroscopy study of NCZA bulk ceramics

ABSTRACTThe Ni0.27Cu0.10Zn0.63Fe1.96Al0.04O4 (NCZA) magnetic bulk ceramics is prepared via conventional solid state reaction technique. X-ray diffraction study has confirmed the single phase spinel crystal structure. The surface morphology has been studied and found small grain size distributions that are separated by well-defined grain boundaries. Besides, to understand the thermal and frequency variation of the electrical and dielectric properties, the investigation has done at different selected temperatures (Tm = 300, 323, 373, 423, 473, 523 and 573) over a range of frequency (20 Hz to 2 MHz) throughout a non-destructive impedance spectroscopy technique. It is observed that the dielectric constant has increased with the increase of Tm as well as frequency. The impedance plot showed two semicircular arcs due to the distinguishing relaxation time constant of charge carrier of grain and grain boundaries. Modulus spectroscopy has been carried out to analyze the mechanism of electrical transport process in the ceramics.

Impact of grain size and structural changes on magnetic, dielectric, electrical, impedance and modulus spectroscopic characteristics of CoFe2O4 nanoparticles synthesized by honey mediated sol-gel combustion method

In this work CoFe2O4 spinel ferrite nanoparticles were synthesized by honey mediated sol-gel combustion method and further annealed at higher temperature 500 °C, 700 °C, 900 °C and 1100 °C. The synthesized spinel ferrite nanoparticles is investigated by x-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), field emission scanning electron microscopy, x-ray photoelectron spectroscopy and vibrating sample magnetometer. The x-ray diffraction study reveals face-centered cubic spinel cobalt ferrite crystal phase formation. The crystallite size and lattice parameter are increased with annealing temperature. Raman and Fourier transform infrared spectra also confirm spinel ferrite crystal structure of synthesized nanoparticles. The existence of cation at octahedral and tetrahedral site in cobalt ferrite nanoparticles is confirmed by x-ray photoelectron spectroscopy. Magnetic measurement shows increased saturation magnetization 74.4 emu g−1 at higher annealing temperature 1100 °C, high coercivity 1347.3 Oe at lower annealing temperature 500 °C, and high remanent magnetization 32.3 emu g−1 at 900 °C annealing temperature. The magnetic properties of synthesized ferrite nanoparticles can be tuned by adjusting sizes through annealing temperature. Furthermore, the dielectric constant and ac conductivity shows variation with frequency (1–107 Hz), grain size and cation redistribution. The modulus spectroscopy study reveals the role of bulk grain and grain boundary towards the resistance and capacitance. The cole-cole plots in modulus formalism also well support the electrical response of nanoparticles originated from both grain and grain boundaries. The dielectric, electrical, magnetic, impedance and modulus spectroscopic characteristics of synthesized CoFe2O4 spinel ferrite nanoparticles demonstrate the applicability of these nanoparticles for magnetic recording, memory devices and for microwave applications.

Effect of Mn and Ni codoping on ion dynamics of nanocrystalline cobalt ferrite: A structure property correlation study

Effect of Mn and Ni codoping on structure, optical and electrical properties of cobalt ferrite nanoparticles prepared by coprecipitation route have been investigated in detail. DSC-TGA, XRD and HRTEM studies have been explored to confirm the phase purity and structure. Most possible cation distribution as estimated by Rietveld analysis suggests the formation ofmixed spinel ferrite phase by the migration of Co2+ ions from B site to A site and hence Fe3+ ions from A site to B site in different amounts due to the doping of Mn and Ni ions. UV–vis study reveals a red shift for Mn and Mn-Ni co-doped samples while a blue shift was observed in case of Ni doping. Conductivity spectra follows the double power law and the modulus spectroscopy study indicates the coexistence of two incomplete relaxation processes in the system that arises due to the co-contribution from both grain and grain boundary which were thoroughly confirmed by complex impedance analysis. Improvement in the dielectric properties in the materials due to doping could be beneficial for device applications.

Dielectric and impedance spectroscopic studies of 0.8BaTiO3–0.2Bi0.5K0.5TiO3lead-free ceramics

0.8 BaTiO3–0.2 Bi0.5K0.5TiO3(BT–BKT20) lead-free ceramics were prepared by conventional solid state reaction method followed by high energy ball milling. The formation of a single phase tetragonal structure in the material was confirmed by X-ray diffraction. Frequency and temperature-dependent dielectric studies show relaxor behavior in the BT–BKT20 which was found to obey modified Curie–Weiss law with degree of diffuseness 1.573. Complex impedance and electric modulus spectroscopy studies reveal temperature-dependent relaxation process in the material. The Cole–Cole plots were measured at high temperatures at which grain effect was observed. Impedance and electric modulus spectroscopy studies show non-Debye kind of conductivity relaxation process in the present material. Activation energies were calculated from impedance and electric modulus spectroscopy and the values of activation energy indicated that the conduction is ionic in nature. AC and DC conductivity have been measured and studied at different temperatures.

Characterization of Electrical Behavior of Ba<sub>5</sub>HoTi<sub>3</sub>V<sub>7</sub>O<sub>30</sub> Ceramic Using Impedance Analysis

Polycrystalline sample of Ba5HoTi3V7O30 was prepared using solid-state reaction technique. X-ray structural analysis indicated a single-phase formation with orthorhombic structure. Microstructural study by SEM showed non-uniform distribution of grains over the surface of the sample. Impedance and modulus spectroscopy studies were carried out, as functions of frequency (42 Hz - 5 MHz) and temperature (RT-773K). The Nyquist plots clearly showed the presence of both bulk and grain boundary effect in the compound. Electrical phenomena in the material can appropriately be modeled in terms of an equivalent circuit with R, C and CPE in parallel. The fitting procedure used here allows us to determine the value of R and C with good precision. Here R2 and R3 correspond to the resistance contributed from the grain boundary and bulk, respectively. C1 and C2 correspond to the capacitance contributed from the grain boundary and bulk, respectively. The real part of electrical modulus shows that the material is highly capacitive. The asymmetric peak of the imaginary part of electric modulus M″, predicts a non Debye type relaxation. The activation energy of the compound (calculated both from impedance and modulus spectrum) is same, and hence the relaxation process may be attributed to the same type of charge carriers.

A diffuse phase transition study on Ba 2+ substituted (Na 0.5Bi 0.5)TiO 3 ferroelectric ceramic

Polycrystalline perovskite lead free material (Na 0.5Bi 0.5) 0.91Ba 0.090TiO 3 was prepared by solid state reaction method. The crystal structure examined by X-ray powder diffraction indicates that the material was single phase with tetragonal structure. Dielectric studies exhibit a diffuse phase transition and characterized by a strong temperature and frequency dispersion of permittivity which relates cation disorder at A-site and exhibits relaxor behaviour. The dielectric relaxation has been modeled using the Vogel–Fulcher relationship, the calculated activation energy found to be E a = 0.021 eV. Complex impedance analysis indicates the system undergoing a polydispersive non-Debye type relaxation. Also, used to characterize grain and grain-boundary resistivities of Ba substituted (Na 0.5Bi 0.5)TiO 3 ceramic. The phenomenon was also interpreted by accounting for microstructural differences. The corresponding relaxation times were also used to confirm the interpretation of complex impedance spectra. Overlapping of grain boundary and electrode relaxation processes can be separated above about 4000 C. Electrical modulus spectroscopy studies have been performed. The conductivity parameters such as ion-hopping rate ( ω p) and the charge carrier concentration ( K 1) have been calculated using Almond and West formalism.

Dielectric relaxation in BaTi0.85(Fe1∕2Nb1∕2)0.15O3 perovskite ceramic

A polycrystalline sample of BaTi0.85(Fe1∕2Nb1∕2)0.15O3 is synthesized by high temperature solid state reaction technique. This sample crystallizes in cubic pervoskite structure at room temperature. The dielectric properties have been investigated at temperature range from 80to450K at various frequencies (100–107Hz). Frequency dielectric dispersion phenomena in a BaTi0.85(Fe1∕2Nb1∕2)0.15O3 ceramic has been analyzed by impedance spectroscopy in the temperature range from 250to450K. The Cole-Cole relaxation equation modified by introducing the conductivity was used to describe the experimental dielectric spectra of a high permittivity. Excellent agreement has been obtained in wide frequency domain (100–107Hz) between the measured and calculated permittivities in the 250–450K temperature range. The dielectric relaxation frequency obeys the Arrhenius behavior with activation energy of 0.181eV. A separation of the grain and grain boundary properties has been achieved using an equivalent circuit model. The different parameters of this circuit have been determined using impedance and modulus spectroscopy studies. The inner grain conductivity also obeys the Arrhenius low behavior with activation energy of 0.183eV. The dielectric relaxation and the inner grain conductivity have thus similar activation energies which suggest a link between these two phenomena.

Probing electrical conduction behavior of BaSnO3

The ac conductivity, σac of BaSnO3 has been measured in the temperature range 310–520 K and frequency range 100 Hz–1 MHz. Below 420 K the conductivity is almost independent of temperature while between 420 and 520 K it is temperature dependent. At 100 kHz the activation energy of these two regions is 0.08 and 0.35 eV, respectively. It has been proposed that in the low temperature region conduction is due to hopping of charge carriers among the Sn+2 and Sn+4 sites. In the high temperature region conduction is due to excitation of charge carriers at the edges of the conduction band and hopping at energies close to it. Further impedance and modulus spectroscopy studies show that the conduction mechanism is the same for grains and grain boundaries.