Activation Energy Of Dc Conductivity Research Articles

Impedance Spectroscopy of Lanthanum-Doped (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 Ceramics

This study examines the effects of La3+ doping on (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3(PBZT) ceramics, which were synthesized using the conventional solid-state reaction method. X-ray diffraction analysis confirmed that the PBZT structure, including PBZT doped with La3+ at concentrations x = 1 at.% and x = 2 at.%, exhibited a rhombohedral (R3c) space group, while higher doping levels of x = 3 at.% and x = 4 at.% led to a dominant cubic (Pm-3m) phase with approximately 30% of a remnant rhombohedral component. Scanning electron microscopy (SEM, JEOL JSM-7100F TTL LV, Jeol Ltd., Tokyo, Japan) and energy dispersive X-ray spectroscopy (EDS) were utilized to investigate the structure and morphology of these ceramics. The findings indicated that the chemical composition of the ceramic samples closely corresponded to the initial stoichiometry of the ceramic powder. An increase in the amount of lanthanum results in a decrease in the average grain size of the ceramics. The electrical properties were further evaluated using complex impedance spectroscopy (IS) over a range of temperatures and frequencies, as well as temperature dependence of DC conductivity. The similarity in the changes in activation energy for DC conductivity and grain boundary conductivity, caused by lanthanum ion modification, allows for the conclusion that grain boundaries are the primary microstructural element responsible for conductivity in these materials.

Na+ conductivity of (100−x)Na3PS4−xCa3N2 glass and glass−ceramics

AbstractThe ionic conductivity of Na3PS4 can be improved via the aliovalent substitution of P and S as well as multivalence cation substitution of Na. Although the enhanced ionic conductivities of tetragonal and cubic Na3PS4 have been theoretically and experimentally studied, the dynamics of sodium ions in these systems have been rarely reported. In this study, (100−x)Na3PS4−xCa3N2 (0 ≤ x ≤ 10) glass samples were synthesizing using high‐energy planetary ball‐milling method. These samples were subjected to heat treatment at 280°C for 1 h in an argon atmosphere to obtain glass–ceramic samples. The structures of these samples were characterized via Raman spectroscopy and X‐ray diffraction analysis. The lattice parameter and cell volume of the glass–ceramic samples strongly depended on the x value in (100−x)Na3PS4−xCa3N2 (0 ≤ x ≤ 10). Their ionic conductivities were determined via alternating current electrochemical impedance spectroscopy (EIS). 92Na3PS4−8Ca3N2 glass–ceramics exhibited an ionic conductivity of 8.14 × 10−4 Scm−1 at 25°C. Charge carrier concentration and hopping rate were extracted from the EIS data to determine the ionic conductivities of the samples. The activation energies of DC conductivity and mobile ion formation and migration were also derived from the EIS data to analyze the effect of Ca3N2 doping on the ionic conductivity of the synthesized samples.

Deciphering the piezoelectric and conductive mechanisms of Nb-doped Bi3Ti1.5W0.5O9 high-temperature piezoelectric ceramics

The study utilizes Bi3Ti(1.5-x)NbxW0.5O9 (BTW-xNb, x=0.00, 0.01, 0.02, 0.04, 0.06) bismuth layered piezoelectric ceramics synthesized via a conventional solid-phase reaction process. This is the study to investigate the impact of B-site Nb ion doping on the structural and electrical properties of BTW-xNb ceramic. The results show that all ceramics have a single bismuth layer structure, with reduced lattice distortion according to Rietveld refinement findings. The presence of oxygen vacancies in the ceramic is the main factor that affects the high temperature conductivity of the samples. The XPS results, the increase in the activation energy of AC and DC conductivity confirm that doping with Nb5+ ions reduces oxygen vacancy concentration. The ceramics with the highest overall electrical performance are the BTW-0.02 Nb ceramics. Notably, the DC resistivity at 500 °C was enhanced from 9.16 × 105 Ω·cm (x = 0.00) to 8.24 × 106 Ω·cm. The TC was enhanced from 730 °C(undoped) to 743 °C. At 500 °C, tanδ decreases from 21.1 % to 8.2 %. The ceramic's increased resistivity increases the polarization voltage, resulting in more complete polarization. The d33 is increased from 7.5 pC/N (undoped) to 13 pC/N. Furthermore, the piezoelectric properties remain stable up to 700°C, suggesting that the material has considerable potential for use at elevated temperatures.

Fabrication of Textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Electrostrictive Ceramics by Templated Grain Growth Using NaNbO3 Templates and Characterization of Their Electrical Properties

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, Smax/Emax (d33*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the “two” law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified.

Dielectric relaxation studies in Sm2O3 doped boro-zinc-vanadate glasses

In this work, the conventional melting procedure was adopted to synthesize glasses with a composition of (ZnO)0.3 – (V2O5)0.3 – (B2O3)0.4-x – (Sm2O3)x, x = 0.002, 0.005, 0.007, 0.01 and 0.02 mol%. The dielectric properties of these glasses were measured. The dielectric constant (εʹ) and dielectric loss (εʹʹ) of glasses are found to vary in the range from 1.9177x102 to 3.9456x103 and from 1.5751 to 6.9095x105 respectively for the temperature range 343 K – 573 K and frequency range 50 Hz to 10 MHz. With increase of frequency, both dielectric constant and loss decreased and increased with increase of temperature. The analysis of dielectric constant and dielectric loss confirmed that the phenomenon of dielectric relaxation is mainly due to the frequency-dependent polarization mechanism. Electric modulus and impedence spectroscopy revealed non-Debye type and a single phase relaxation process. Activation energy for dc conductivity and dielectric relaxation are found to be of same size indicating that the potential barrier encountered by the charge carriers is same in both the processes. The master curves suggested that temperature-independent relaxation is occurring in the present glasses. The high values of measured dielectric parameters suggest that the present glasses are suitable in semiconducting and energy storage applications.

Investigation of dysprosium oxide substitution on physical, electrical and dielectric properties in sodium borosilicate glass system

Dysprosium oxide doped sodium borosilicate glasses were prepared in this study using a usual melt-quenching process. Further XRD, FTIR, density measurements, electrical conductivity, and dielectric properties were utilized to explore the prepared glassy samples. We found that all produced samples exhibit amorphous nature through X-ray diffraction. Increase in density and molar volume were found when dysprosium oxide concentration increased, which was ascribed to dysprosium oxide's greater molecular weight. Density data was used to calculate and explain several physical characteristics, including rare earth ion concentration (N), polaron radius (rp), internuclear distance (ri), and field strength (F).

Electrical conductivity and significant radiation shielding properties of B2O3.Pb3O4.ZnO.Y2O3 glasses

The electrical properties and radiation shielding characteristics are investigated for a glass system of the configuration 60% B2O3-35% Pb3O4-(5-x)%ZnO - x%Y2O3 with x from 0 to 3 mol%. Frequencies from 100 Hz to 5 MHz were applied to measure the ac conductivity in a temperature range between 310 and 700K. The values of ac conductivity (σac) are found in the range from 2×10−9 S.cm−1 to 5×10−2 S.cm−1, while the activation energy for ac conductivity (Eac) is found to fluctuate between 0.4 and 1.43 eV. The dc conductivity (σdc) and dc activation energy (Edc) are discussed according to thermal activation and small polaron hopping mechanisms. An alternation from mainly electronic to mainly ionic conduction mechanism is evidenced for the samples greater than 2% mol of the Y2O3. The radiation shielding characteristics are studied in wise of mass attenuation coefficient, μ/ρ, effective atomic number, Zeff, half value layer (HVL), and mean free path (MFP). The values of μ/ρ are obtained experimentally and theoretically by Phy-X/PSD software. The obtained relative deviation between theoretical and experimental results lies in the range from 0 to 3.8%. All the shielding factors demonstrate an inverse reliance on the Y2O3 content in the glasses. The MFP and HVL magnitudes of the glasses are compared with other traditional shielding materials and presented better attenuation ability. The relation between the shielding parameters and the electrical properties is discussed and it is also found that both properties are strongly affected by the interionic separations between the Pb ions in the glasses.

Density functional theory investigation of activation energy for dc conductivity in rare-earth ion-doped Na2ZnP2O7 glasses

Density functional theory investigation of activation energy for dc conductivity in rare-earth ion-doped Na2ZnP2O7 glasses

The conduction mechanism and dielectric behavior of cadmium bismuth silicate glasses

By using the traditional melt-quench method, cadmium bismuth silicate glasses with composition; 20CdO·(80-x)Bi2O3·xSiO2 (10≤x≤50 mol%) were fabricated. Impedance spectroscopy was used to examine the conduction and relaxation mechanisms in prepared glasses over the range of frequency 10Hz–7MHz and temperature 473–703 K. Values of dc conductivity (σdc), the activation energy for dc conduction (Edc), frequency exponent parameter (s), and relaxation energy (Eτ) were extracted from the experimental impedance data. The conductivity spectra follow Jonscher’s power law and the obtained conductivity values were found to be compositional dependent ascribed to the existence of mixed former effect in understudy glasses. The frequency exponent parameter increases with frequency and approaches unity at higher frequencies. For each glass composition, almost equal values of Eτ and Edc show that the charge carriers have to cross a similar energy barrier in relaxation and conduction processes. The exact overlaying of normalized electrical modulus plots as a single master curve signifies temperature-independent dynamical processes at various frequencies.

Impact of ZnS/Mn on the Structure, Optical, and Electric Properties of PVC Polymer.

The most efficient way to create novel materials that may be used in a variety of optoelectronic applications is thought to be doped mixed polymers with appropriate fillers. Undoped and doped PVC polymers with ZnS/Mn formed at different temperatures were fabricated using the casting method. The Rietveld method was used to discover the structure and microstructure of Zn0.95Mn0.05S prepared at T = 300, 400, and 500 °C. The distribution and existence of the nanofiller over the PVC matrix were determined via XRD, FTIR, EDS, and SEM techniques. The effect of the preparation temperatures of the ZnS/Mn nanofiller on the absorption, transmittance, reflectance, refractive index, extinction coefficient, dielectric constant, AC conductivity, electrical modulus, and DC conductivity activation energy data of the PVC polymer was studied using the diffused reflectance technique. Doping PVC with ZnS/Mn (prepared at 300 °C) lowered the direct and indirect optical band gaps from 5.4 and 4.52 eV to minimum values of 4.55 and 3.63 eV. The fluorescence intensity of pure PVC is greatly enhanced upon loading with ZnS/Mn. The PVC exhibited two near UV peaks, one violet and one blue color, while, in addition, the doped polymers exhibited green and orange colors. The corresponding CIE diagram for all the samples was also determined.

Improvement in the electro-optical and electronic properties of the reduced graphene oxide dispersed in a liquid crystalline material 4’-octyl-4-cyano-biphenyl

ABSTRACT Herein, a small concentration (0.05 wt %) of reduced graphene oxide is dispersed in the liquid crystalline media. Thermodynamic study shows the reduction of the transition temperature, enthalpy and entropy of the reduced graphene oxide dispersed nanocomposite. Optical study suggests the decrease of the optical bandgap of the dispersed nanocomposite as compared to that of the pure sample. Dielectric spectroscopic measurement is done for measuring the permittivity and conductivity of the pure and the dispersed samples. The value of dielectric anisotropy has decreased for the dispersed nanocomposite whereas the value of ionic (DC) conductivity of the dispersed nanocomposite has increased by 3 orders of the magnitude as compared to that of the pristine sample. The activation energy for DC conductivity has reduced in the dispersed nanocomposite which is responsible for the increment in DC conductivity of the system. The cut-off region of DC conductivity has increased in the dispersed nanocomposite. Electro-optical studies suggest the reduction of the threshold voltage for the Freedericksz transition, splay elastic constant and rotational viscosity for the dispersed nanocomposite.

Structure, charge carrier conduction, dielectric properties and leakage current density of Dy2CoMnO6 double perovskite

In this study, the structure, charge transport properties, dielectric properties, and leakage current density of Dy2CoMnO6 double perovskite are investigated. The sample is prepared via auto–ignition method. The Rietveld refinement of the X–Ray diffraction pattern of the sintered sample reveals the monoclinic phase with space group P21/n. The crystal structure of the sample is distorted and tilted. The dominant oxidation state of Co and Mn are +3 and +4, which are estimated from the bond valence sum method. The values of activation energy for dc conduction are 0.16 eV (≤ 75 ℃) and 0.37 eV (≥ 100 ℃). The charge carrier conduction follows a correlated barrier hopping mechanism (≤ 75 ℃). Scaling spectra confirms the temperature independence nature of the conduction and relaxation mechanism below 75 ℃. The grain boundary conductivity is higher than the grain interior conductivity due to the low grain boundary blocking factor. The sample exhibits a non–Debye type nature. The value of the tangent of dielectric loss lies from 4.15 to 33.11 in the frequency range from 50 Hz to 500 KHz, and the value of real part of complex dielectric constant lies between 102 and 67608 in the frequency range from 500 Hz to 50 kHz. The analysis of the imaginary part of the complex dielectric constant confirms the predomination of the dc electrical conduction process in the sample. The comparable values of the activation energy for dc conduction, grain interior conductivity, grain boundary conductivity, migration energy, and activation energy confirm the interlinking among these processes. The room temperature leakage current density is 4.36 × 10–4 Acm–2 at 8.05 Vcm–1. The leakage current density follows the Ohmic conduction and has been explained with the Schottky barrier model.

Effect of Ag2S on electrical conductivity and dielectric relaxation in Ag2O-MoO3-P2O5 ionic glassy systems

The influence of Ag2S incorporation on the electrical and dielectric properties of the host Ag2O-MoO3-P2O5 glassy matrix has been systematically studied in the present communication. By applying the well-known Archimedes principle, the density of the samples has been determined. The ionic property for all the as-prepared glassy systems has been explored methodically. The nearly identical obtained values of the crossover frequency and the activation energy for DC and AC conductivity suggest that the same mechanism is responsible for electrical conduction. For the purpose of inspecting the frequency and temperature dependent AC conductivity, the Almond-West formalism model has been used. The observed values of dielectric constant and dielectric loss are found to increase with the temperature rise and drop with rising frequency. The coinciding scaled complex electric modulus spectra suggest a non-Debye type dynamical relaxation mechanism, which also indicates that the relaxation mechanism is temperature independent but composition dependent.

Dielectric, AC Conductivity, and DC Conductivity Behaviours of Sr2CaTeO6 Double Perovskite.

Relatively new double perovskite material, Sr2CaTeO6, has been prepared through conventional solid-state procedures. Structural, dielectric, and optical characteristics of this exquisite solid-state material were analysed in this study. The single-phase monoclinic P21/n structure of this prepared compound was well correlated with the literature review. Good distribution of grain sizes and shapes was observed in the morphological study of this compound. The discussions on its optical and dielectric properties are included in this manuscript. High dielectric real permittivity, low dielectric loss, and good capacitance over a range of temperatures possessed by this compound, as shown in dielectric and electrical modulus studies, indicated good potential values for capacitor applications. The Ro(RgQg)(RgbQgb) circuit fitted well with the impedance and electrical modulus plot of the compound. Its relatively high electrical DC conductivity in grain at high frequencies and its increasing value with the temperature are typical of a semiconductor behaviour. This behaviour might be attributed to the presence of minor oxygen vacancies within its lattice structure and provides a long-range conduction mechanism. A small difference between activation energy and Ea of DC conductivity indicates that the same charge carriers were involved in both grains and the grain boundaries’ long-range conduction. The electrical AC conductivity of this compound was found to contribute to the dielectric loss in grain structure and can be related to Jonscher’s power law. The presence of polarons in this compound was exhibited by non-overlapping small polaron tunnelling (NSPT) and overlapping large polaron tunnelling (OLPT) conduction mechanisms over a range of temperatures. Wide optical band gap and Eopt in the range of 2.6 eV to 3.6 eV were determined by using an indirect and direct allowed mechanism of electrons transitions. These values supported the efficient semiconducting behaviour of the grain in this material and are suitable for applications in the semiconductor industry.

Investigation of quality and performance of Cu impregnated NiO-GDC as anode for IT-SOFCs

Ni-based cermet as solid oxide fuel cell (SOFC) anodes suffers from redox instability issues when operated with hydrocarbon as fuel. This paper investigates the Cu impregnated NiO-GDC as anode electrode for intermediate temperature (IT-) SOFCs using structural and morphological characterizations along with the dc conductivity measurement in hydrogen and biogas. The bulk of Cu impregnated NiO-GDC composite and its reduced (heat-treated in H2 at 850 °C for 3 h) counterpart samples were analyzed after exposing different layers within the bulk of samples to different characterization tools. Cu particles are observed at all three layers investigated, suggesting the distribution of Cu in the bulk of composite anode samples. Also, the porous morphology of fabricated samples was decreased with increased depth into the sample. The BSE and EDS characterization show that Cu and Ni particles are distributed within the bulk of the reduced composite anode sample while the Cu particles are largely located in the middle layer. Relatively higher (lower) dc conductivity (activation energy) was observed for the reduced composite anode sample in biogas than that of hydrogen and were 9.9 × 10−3 (0.81 eV) and 4.5 × 10−3 S/cm (0.88 eV), respectively.

Structure, small polaron hopping conduction and relaxor behavior of Gd2NiMnO6 double perovskite

In this study, double perovskite Gd2NiMnO6 is prepared via auto–ignition method. Rietveld refinement of the XRD profile confirms the single phase monoclinic structure with space group P21/n. The cation Ni exhibits mixed valence state (+2/+4) and Mn exhibits +4 valence state. Grain, grain boundary and dc conductivity increase with temperature indicating the semi–conductive nature of the material. The grain conductivity is much higher and activation energy for grain conductivity is much lower than the grain boundary. The activation energy for dc conduction and hopping energy are almost identical at different temperature regions. The charge conduction mechanism follows non–overlapping small polaron tunnelling (NSPT) model. Different Mott's parameters confirm small polaron hopping. The polaron hopping mechanism is non–adiabatic in nature. Time–temperature superposition principle confirms the temperature independent nature of hopping mechanism. The value of electron photon coupling constant is 8.27 which confirms the strong electron–phonon coupling in this material. The dielectric relaxor behavior is found to follow modified Curie–Weiss law which becomes more conform with frequency. The value of co–efficient of diffuseness lies in the range 1.69–1.96 which confirms the diffuse behavior of the material.

Investigation of structural and impedance spectroscopic properties of borate glasses with high Li+ concentration

Lithium borate glasses prepared by melt-quench technique have been studied with a view to ascertain their structural and electrical properties. FTIR analysis of the present samples reveals the absence of boroxol rings, presence of structural units of lithium formed with oxygen and increase in the number of Non-Bridging Oxygens (NBOs) in the glass system. The real and imaginary parts of dielectric constant increase with frequency and temperature arises due to interfacial ionic polarization. The non-exponential Kohlrausch-Williams-Watts (KWW) function has been found to follow by the imaginary part of electric modulus, thereby confirming its applicability. The fitting of data of ac conductivity as per Jonscher's universal power law indicates hoppable ion concentration dependent upon temperature and Li2O content. The analysis is further supported by the variations of ac-conductivity as well as the activation energy for dc conductivity. A decrease in impedance and increase in the space charge polarization is observed with increasing Li2O concentration. Further, the electrical behavior of samples has been investigated via an impedance equivalent circuit corresponding to the Nyquist plot.

A DFT-based model to the interpretation of DC conductivity in transition metals doped zinc phosphate glass

Ternary zinc–sodium–phosphate glasses doped with transition metal of the composition Na2MxZn1−xP2O7(x = 0, 1, 2 and 5 mol %) (where M = Ni, Cu and Co) were prepared by the traditional quenching method. The ac conductivity measurements at different temperatures for the prepared glasses have been investigated, and the activation energy for dc conduction has been determined in each transition metal doped sample. The results showed that the evolution of the activation energy of the conductivity depends on the nature of the dopant ions. A model based on formal density functional theory concept in which the electrical charge exchanged between the transition-metal cations and the surrounding material surface is proposed. The outcome is a “simplified” formula which allows us to explain the evolution of the ionic dc conductivity activation energy as a function of the doped ion in interaction with the cation and the surface.

Immittance Studies of Bi6Fe2Ti3O18 Ceramics.

Results of studies focusing on the electric behavior of Bi6Fe2Ti3O18 (BFTO) ceramics are reported. BFTO ceramics were fabricated by solid state reaction methods. The simple oxides Bi2O3, TiO2, and Fe2O3 were used as starting materials. Immittance spectroscopy was chosen as a method to characterize electric and dielectric properties of polycrystalline ceramics. The experimental data were measured in the frequency range Δν = (10−1–107) Hz and the temperature range ΔT = (−120–200) °C. Analysis of immittance data was performed in terms of complex impedance, electric modulus function, and conductivity. The activation energy corresponding to a non-Debye type of relaxation was found to be EA = 0.573 eV, whereas the activation energy of conductivity relaxation frequency was found to be EA = 0.570 eV. An assumption of a hopping conductivity mechanism for BFTO ceramics was studied by ‘universal’ Jonscher’s law. A value of the exponents was found to be within the “Jonscher’s range” (0.54 ≤ n ≤ 0.72). The dc-conductivity was extracted from the measurements. Activation energy for dc-conductivity was calculated to be EDC = 0.78 eV, whereas the dc hopping activation energy was found to be EH = 0.63 eV. The obtained results were discussed in terms of the jump relaxation model.

Scaling behavior and variable-range-hopping conduction of localized polarons in percolative BaTiO3-Ni0.5Zn0.5Fe2O4 ceramic composite with colossal apparent permittivity

The percolative BaTiO3-Ni0.5Zn0.5Fe2O4 (BTO-NZFO) ceramic composite represents a family of multifunctional materials exhibiting multiferroic properties and colossal apparent permittivity. It is of fundamental interest to investigate the conduction mechanism in such percolative composites from both macroscopic and microscopic perspectives. Herein, three representative systems with the NZFO content locating below the percolation threshold fc, near fc, and above fc, respectively, were investigated, using pure NZFO ceramic as a comparison. The conductivity of the composite as a function of NZFO content agrees well with the McLachlan model, which takes percolation into consideration and essentially equivalent to the Kirkpatrick model. The electrical conductivity of the composite conforms to Mott's variable-range-hopping (VRH) model in the temperature range of 303–573 K, suggesting that VRH conduction of localized polarons dominates the electrical behavior microscopically. Parameters including the most probable hopping range (R); the density of localized states at the Fermi level [N(EF)]; and the activation energies of VRH (W), dc conductivity (Edc), hopping (Eon), and relaxation (Er) were obtained and analyzed. Scaling behaviors of the conductivity and the imaginary part of complex impedance of the composite have been observed, implying that the distribution of relaxation times is temperature independent. The impedance data measured at different temperatures exhibit typical semiconducting behavior, which can be well fitted by an equivalent circuit model considering both grain and grain boundary responses. The correlation between conductivity and colossal apparent permittivity has also been revealed. The discoveries deepen the understanding of the conduction mechanism in such multifunctional composites composed of an insulating phase and a semiconducting phase.