Activation Energy Of Electrical Conductivity Research Articles

Multi-scale structural regulation of negative temperature coefficient effect and electrical conduction mechanism of xSm2O3-(1-x) CaCu3Ti4O12 ceramics

In this work, a series of xSm2O3-(1-x) CaCu3Ti4O12 (xSm2O3-(1-x)CCTO, x = 0.00-0.05) negative temperature coefficient (NTC) ceramics were prepared by a solid-state method. The influence of Sm2O3 content on electrical properties was examined using microstructural, band gap, morphological, Direct Current (DC) resistivity, and impedance spectroscopy analysis. The increase in Sm2O3 content resulted in a gradual decrease of the resistivities (ρ25), thermal constants (B25/75), activation energies for electrical conduction (Ea) and activation energies of the relaxation process (Erelax) from 1.16×107 Ω•cm, 6387 K, 0.5456 eV and 0.5592 eV to 3.43×105 Ω•cm, 4149 K, 0.4088 eV and 0.4115 eV respectively. First-principles calculations revealed a reduction in the band gap by adding Sm2O3, partially explaining the decrease in electrical resistivity. In-situ XPS analysis elucidated a relationship between conduction mechanism of Sm2O3-doped CCTO ceramics and electron hopping. Impedance analyses showed that both grains and grain boundaries contributed to the NTC effect of ceramics. The electrical inhomogeneity arose from grains and grain boundaries, while local relaxation was due to the short-range motion of charge carriers.

Manganese dioxide nanoparticles and nanocomposites with carbon black. Synthesis, physical-chemical and electrical properties

In this study, α- and β-MnO2 and composites with carbon black (CB) were chemically synthesized and prepared through mechanical mixing respectively. The samples’ crystal structure, morphology, and electrical properties have been investigated herein. It is found that average particle sizes of 12–15 nm and 18–24 nm for α- and β-MnO2, respectively. The surface area and average pore volume of obtained samples of α- and β-MnO2 are 200 and 70 m2/g, and 3.2 and 5.3 nm, respectively. The electrical conductivity performances and activation energy behavior of samples have been analyzed. The correlation between the CB content in the composites and their electrical conductivity was established based on experimental data. The electrical conductivity of the α-MnO2/C monotonic increase from 1.31 to 18.6 S/m. There was a 7.5-fold increase of conductivity for α-MnO2 with 15 wt.% CB and almost a 30-fold increase for β-MnO2 with the corresponding CB content compared to the pure samples. In composite samples, the activation energy decreases from 0.069 to 0.041 eV and from 0.154 to 0.074 eV for α- and β- MnO2/C, respectively.

DISCUSSION OF THE MECHANISM OF THE ELECTRICAL CONDUCTIVITY OF PURE WATER IN THE FRAMEWORK OF THE BJERRUM MODEL

An alternative mechanism of electrical conductivity and ionization of molecules in pure water is considered. Calculation of the temperature dependence for the activation energy of ionization of water molecules was carried out using data on the value of its ionic product. The calculated activation energies for the ionization and flow processes show the presence of a certain proportionality between them. This suggests that the ionization of water is caused by intermolecular forces rather than intramolecular forces. Accordingly, the electrical conductivity of water is associated with the appearance and movement in it of L and D defects of hydrogen bonds between water molecules, which have significant electrical pseudo charges and are considered in the Bjerrum model for ice. This work proposes a new interpretation of the mechanism of ionization (pseudoionization) of molecules and generation of L and D defects in water. Rotation is considered not for one, but for two of its molecules in opposite directions with partial compensation of their angular momentum, and the breaking of not three bonds for one molecule, but four bonds with neighbors for two molecules. Moreover, these four neighbors do not include molecules from water clusters that have stronger bonds, since neighboring molecules with weaker bonds can be found for the process of rotation activation. Accordingly, the exponential contribution made by molecules from water clusters is absent or small in the ionization activation energy. In this way, the activation energy for the flow, which occurs throughout the entire volume of the liquid and automatically includes molecules from clusters, differs from the activation energy of electrical conductivity, which occurs for individual molecules in chains of bonds. The presence of a maximum in the ionic product of water near 250 ⁰C can be explained by the rapid decrease in the lifetime of L and D defects with heating, which prevents the use of the standard equation for accurate calculation of the ionization activation energy above 100...200 ⁰C. However, the presence of this maximum contradicts the generally accepted model of proton hopping between neighboring hydronium and water molecules in the mechanism of its electrical conductivity.

ОЦІНКА СТРУКТУРИ ШЛАКОВИХ РОЗПЛАВІВ НА ПІДСТАВІ АНАЛІЗУ ТЕМПЕРАТУРНИХ ЗАЛЕЖНОСТЕЙ В’ЯЗКОСТІ ТА ЕЛЕКТРОПРОВІДНОСТІ З ВИКОРИСТАННЯМ АДАПТИВНОЇ СЕГМЕНТНОЇ РЕГРЕСІЙНОЇ МОДЕЛІ

The expediency of using an adaptive segmented regression model for the analysis of logarithmic dependences of viscosity and electrical conductivity on temperature to assess the structure of slag melts is shown. Calculated values of the activation energies of viscosity ( ) and electrical conductivity ( ) in different temperature ranges. The obtained calculation results confirm that the viscosity and electrical conductivity of slag melts characterize the interaction of various structural particles (ions and/or their groups) and can be used in the study of the structure of slag melts. It was established that the activation energy of viscosity and electrical conductivity decreases as the temperature of slag melts increases. The performed calculations of the indicator n=En/Ex indicate that it can be a criterion for evaluating the structure of the slag melt, when n >1, the slag melt is a heterogeneous system, and when n < 1, it is a homogeneous system. Viscosity and electrical conductivity are interdependent properties and can be predicted if there is data on one of the properties, provided the value of n is known.

Физико-химические свойства растворов перхлората и тетрафторбората лития в смеси сульфолана и сернистого ангидрида

The temperature dependencies of physical and chemical properties (viscosity, density, electrical conductivity) and the melting temperature of 1M solutions of lithium salts (LiClO4 and LiBF4) in the mixture of sulfolane and sulfurous anhydride (∼1M) were studied. It was shown that the introduction of 1M (5% wt.) of sulfurous anhydride into 1M solutions of LiClO4 and LiBF4 in sulfolane increased the specific and corrected electrical conductivity, densities, activation energy of electrical conductivity and viscous flow of electrolyte solutions; and reduced viscosity and melting temperatures.

Non-isothermal crystallization kinetics and memory switching properties of Tl-Se-Ge-Sb chalcogenide semiconductor alloy for thermally stable phase change memory applications

Quaternary (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass was synthesized using melt-quenching and thermal evaporation techniques for bulk and thin film samples, and its amorphous character was confirmed by XRD. Based on different models of non-isothermal crystallization kinetics, the average values of the glass transition and the crystallization activation energies are 121.33 and 82.94 kJ mol−1, respectively. The crystallization mechanism in the examined composition is 2D nucleation growth, according to Avrami exponent Thermal parameters of the studied quaternary glass, like fragility fluctuation free volume reduced glass transition temperature thermal stability and glass formation ability were investigated and indicated that the (Tl20Se70Ge10)0.85Sb0.15 ChG exhibits a good ability of glass formation and thermal stability. The obtained results of the dc electrical conductivity are found to increase with temperature and decrease with film thickness. The electrical conduction activation energy (0.583 ± 0.004 eV) is thickness independent and the predominant conduction mechanism is the hopping of charge carriers in the band tail localized states. The () curves of (Tl20Se70Ge10)0.85Sb0.15 chalcogenide glass film samples were analyzed and shown to be appropriate for a memory switch. The mean value of the threshold voltage decreases exponentially as temperature increases, whereas it increases linearly as film thickness increases. The values of threshold voltage and threshold resistance activation energies are 0.282 ± 0.003 and 0.521 ± 0.004 eV, respectively. The obtained switching characteristics data were discussed in view of the electrothermal model motivated by current channel Joule heating. These findings highlight the suitability of the investigated composition for various optoelectronic applications, such as memory switching devices, optical data storage, phase-change memories and optical fibres sensing devices.

Structural, micro-structural, morphological, electrical spectroscopy and optical analysis of lithium-titanium oxide electronic material

In this paper, we perform a thorough analysis into the electrical properties of high-purity, thick Li2TiO3 discs generated by the mixed oxide process, covering a wide range of frequencies and temperatures. Li2TiO3 samples are calcined and sintered at 920 °C and 940 °C. X-ray diffraction shows a monoclinic crystal structure with a space group of C2/c(15), matching JCPDS card (00-033-0831). The Scherrer and W-H plot methods provide consistent crystallite sizes of 51.23 and 49.34 nm. SEM and EDAX at room temperature reveal the material's structure and chemistry. The microstructure has well-defined porosity and homogeneous grain dispersion, with an average grain size of 2.82 µm. We studied frequencies from 1 kHz to 1 MHz and temperatures from 30 °C to 450 °C. Measure dielectric constant, tangent loss, and electrical conductivity. Above 350 °C, the dielectric constant increases significantly. Between 400 °C and 450 °C, electrical conductivity activation energy ranges from 0.431 to 0.624 eV. UV–Visible spectroscopy shows maximal absorption at 201 nm, indicating a band gap value of 3.78 eV. Its residual, saturation, and coercivity values were 0.00286 µc/cm2, 0.0267 µc/cm2, and 0.974 kV/cm, respectively, from the hysteresis loop. The UV spectrum shows Li2TiO3 absorbs most light at 201 nm and has a 3.82 eV band gap. Its composition and chemical processes are confirmed by FTIR peaks at various wavenumbers. Based on these results Li2TiO3 might have the potential applications in electronic devices such as capacitors, insulators, and electrochemical sensors as well as humidity and gas monitoring devices.

ELECTROCONDUCTIVITY OF MOLTEN FLiNaK AND FLiNaK–CeF<sub>3</sub>

The eutectic mixture LiF–NaF–KF (FLiNaK) is promising as a carrier salt for molten-salt reactors. Cerium fluoride CeF3 can be considered as a simulant of plutonium fluoride PuF3. In this work, the temperature dependence of the electrical conductivity of the molten ternary eutectic LiF–KF–NaF containing from 0 to 25 mol % cerium fluoride in the temperature range 480–777°C. FliNaK–CeF3 mixtures containing up to 25 mol. % of cerium fluoride were prepared directly in the experimental cell, dropping the required amount of CeF3 into the melt and keeping mixtures of a given composition for 12 h at temperatures exceeding the liquidus temperatures of the studied compositions. The electrolyte resistance was determined from impedance hodographs, which were taken using the Z-1500J impedance meter. A two-electrode cell with Pt electrodes was used. Analysis of the experimental values of the electrical conductivity of double and triple fluoride melts KF–LiF available in the literature; KF–NaF; LiF–NaF–KF shows that our data on the electrical conductivity of the LiF–NaF–KF (FLiNaK) eutectic mixture are consistent with the general trend in electrical conductivity with increasing KF concentration in the melt. A significant decrease in the specific electrical conductivity of the molten system and a slight increase in the activation energy of electrical conductivity with an increase in the concentration of cerium fluoride are shown. The temperature dependences of the electrical conductivity of the molten system were approximated by second-order polynomials. The formation of the \({\text{CeF}}_{6}^{{3 - }}\) complex ion in the melt was confirmed by spectral studies. The Raman spectra of molten FLiNaK and FliNaK–CeF3 mixtures containing 8 and 15 mol. % of cerium fluoride were recorded. With an increase in the concentration of CeF3 in the melt, the amount of \({\text{CeF}}_{6}^{{3 - }}\) complex ions increases, which leads to an increase in the intensity of the observed vibrational bands.

INVESTIGATION OF THE SPECIFIC ELECTRICAL CONDUCTIVITY OF RHENIUM-CONTAINING SOLUTIONS OF AMMONIUM CARBONATE AND CALCULATION OF ITS ACTIVATION ENERGY

The specific electrical conductivity dependence of aqueous solutions of ammonium carbonate and solutions of the ammonium carbonate—ammonium perrenate system on the reagents content in the range of their concentration of 0.1—1.8 mol/l for (NH4)2CO3, 0.01—0.1 mol/l for NH4ReO4 and solution temperatures in the range of 20-50 °C were investigated by the conductometric method. A linear increase in electrical conductivity with an increase in the temperature of electrolytes and a nonlinear increase with an increase in the concentration of reagents was revealed. The temperature coefficients values of electrical conductivity and the activation energy values of electrical conductivity in the studied range of concentrations and temperatures are calculated. A decrease in the activation energy of electrical conductivity with an increase in the temperature of the solution was noted. The calculated value of the activation energy of electrical conductivity indicates the diffusive nature of charge transfer.

Electrical performance and conductive mechanism of xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 ceramics with NTC effect via chemical modification

xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 (xLCO-(1-x)BCTS) ceramics were manufactured using a solid-phase reaction method. All samples exhibited single cubic perovskite structures and a typical negative temperature coefficient (NTC) effect. The grain sizes increased with increasing LCO doping content. For all samples, the resistivities (ρ25), activation energies for electrical conduction (Ea), thermal constants (B25/75), and activation energies of the relaxation process (Erelax) were in the ranges of 5.93 × 104-9.36 × 108 Ω•cm, 0.3700–0.2951 eV, 3177–3988 K, and 0.3539–0.2890 eV, respectively. Such a combination of ρ and B renders these materials to be potential candidates for NTC thermistors. According to the XPS spectra and due to the difference in ion radius among Co3+, Co4+, Ti3+, and Ti4+, Co3+-O-Co2+ and Ti3+-O-Ti4+ bonds were formed, and the electrons in the continuous bonds generated jumping conduction. The fitted results of the equivalent circuit showed that Rg and Rgb decreased with increasing LCO content, which is consistent with the DC resistivity at 25 °C. The results of the analysis indicate that the conductive mechanism of xLCO-(1-x)BCTS ceramics was electron hopping conduction.

Temperature-dependent electrical resistivity of tungsten oxide thin films

Tungsten oxide (WO3) thin films have been previously investigated for various applications. Optoelectronic and electrochromic applications require detailed knowledge of the electrical properties of such films, whereas gas-sensing applications require understanding the electrical resistivity and its variation with temperature. In numerous studies on the electrical properties of WO3 thin films, the results were widely scattered and critically dependent on deposition and resistivity measurement conditions. This paper presents a systematic investigation of the electrical resistivity of WO3 thin films and its variation with temperature. WO3 thin films were deposited on heated substrates using thermal evaporation both in vacuum and under an oxygen atmosphere. Subsequently, the films were annealed in air or in vacuum. The structural, chemical, optical, and room-temperature electrical properties were measured. The temperature-dependent electrical resistivity was measured at 300–700 K in air or in vacuum. The activation energies for electrical conduction were derived from these measurements and were used to investigate the mechanisms responsible for electrical conduction.

High temperature dielectric properties of calcium zirconate

AbstractThe electrical properties of dense, high purity CaZrO3 discs, sintered at 1380°C with and without added ZrO2, were investigated up to 950°C. Dielectric constant, loss tangent, and electrical conductivity were measured from 25 to 725°C, and the real and imaginary impedances were measured between 800 and 950°C by impedance spectroscopy techniques. Dielectric constant increased by 8% above 300°C and loss tangent increased from .1% at 25°C to ∼2% above 300°C. Activation energy of electrical conductivity determined between 300°C and 950°C by alternative current (AC) and direct current (DC) measurements. These results indicate that CaZrO3 could be a useful dielectric material for capacitor applications up to 500°C. A reported decrease in conductivity due to addition of excess ZrO2 into stoichiometric CaZrO3 could not be confirmed.

Study of the Resistive Properties of Lead Silicate Glasses after Chemical Impact

The change in the resistive characteristics of lead silicate glasses (LSGs) after treatment in alkaline and acid solutions is studied. It is established that the chemical treatment of glasses and, accordingly, blanks of microchannel plates (MCPs) affects the high-temperature ionic conductivity at a constant activation energy of electrical conductivity. It is shown that the treatment of glasses in NaOH and HF solutions can significantly change the electrical resistance.

ELECTRICAL CHARACTERISTICS OF BISMUTH-CONTAINING CERIUM OXIDE

Ceramics Ce0.9Bi0.1O2 – ? was obtained by solid-phase synthesis. It is shown that the obtained samples have a cubic fluorite structure with the space symmetry group Fm3m. The electrical properties of the Ce0.9Bi0.1O2 – ? solid solution were studied by ac impedance spectrometry. It has been established that the activation energy of electrical conductivity has two sections 0.51 eV (400 – 680 ?С) and 1.6 eV (680 – 800 ?С), the activation energy of the dielectric relaxation process was 0.88 eV.

Chemical bottom-up approach for inorganic single-atomic layers aiming beyond graphene.

A chemical bottom-up approach for single-atomic-layered materials like graphene is attractive due to the possibility of introducing functions. This article includes the synthesis and properties of borophene-oxide and metalladithiolene layers, which are reported as inorganic materials. They have graphene-like two-dimensional networks that enable conjugated structures. Their atomically thin layers are also available by dissolution or synthetic methods. Their two-dimensional electronic features are evaluated from the activation energies for electrical conduction, focusing on the anisotropic features of borophene-oxide layers and the switching abilities of metalladithiolene layers.

Physical insights into the grain size effect on the electrical properties of nanocrystalline La2Zr2O7 pyrochlores

The role of grain size on the electrical properties of nanocrystalline La2Zr2O7 (LZO) ceramics prepared by chemical co-precipitation is reported. Grain size from 10 to 70 nm was obtained. The XRD and Raman scattering showed a pyrochlore structure of La2Zr2O7. Morphology and chemical analysis were done by SEM and XPS, respectively. Electrical conductivity studies using impedance spectroscopy resolved the conductivity borne to grain and grain boundary with a non-Debye nature of conduction. The activation energy (Ea) for electrical conduction through grain was almost the same for all the grain sizes and equal to 1.20 ± 0.03 eV. However, the Ea of the grain boundary had decreased from 1.17 eV to 0.78 eV with an increase in grain size, and the conduction is due to oxygen ion migration. The conduction mechanism was governed by the non-overlapping small polaron tunneling model. Additionally, ion-ion correlation in conduction is increased with increasing grain size.

Optical and electrical properties of copper alumina nanoparticles reinforced chlorinated polyethylene composites for optoelectronic devices

The incorporation of transition metal oxide fillers into the polymer matrix through solution mixing polymerization imparts enhanced electrical and thermal properties. The present work focused on the optical properties, crystallinity, thermal stability, temperature-dependent conductivity, dielectric constant and modulus of chlorinated polyethylene/copper alumina (CPE/Cu–Al2O3) nanocomposites. Optical absorption measured using an ultraviolet–visible (UV–visible) spectrometer shows enhanced intensity and a blue shift for CPE/Cu–Al2O3 nanocomposites. The bandgap energy of CPE/Cu–Al2O3 nanocomposites was lower than pure CPE and minimum bandgap energy was recorded for a 7 wt% composites. The X-ray diffraction demonstrates that Cu–Al2O3 nanoparticles were uniformly introduced into the CPE matrix. Thermogravimetric analysis (TGA) manifests improved thermal stability of nanocomposites. Dielectric properties decrease with frequency, whereas AC conductivity increases with frequency, and both AC conductivity and dielectric properties increase with temperature. The maximum AC conductivity and dielectric constant were obtained for 7 wt % nanofiller loaded sample. For all systems, the activation energy for electrical conductivity decreases with rising temperatures. The experimental dielectric constant values of CPE nanocomposites were correlated with different theoretical models. The Bruggeman model was in good agreement with the experimental permittivity. The impedance experiments showed a decreasing trend with temperature, indicating the semiconducting nature of prepared nanocomposites.

The role of Co valence in charge transport in the entropy‐stabilized oxide (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O

AbstractMany of the studies on the entropy‐stabilized oxide (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O have been heavily application‐based. Previous works have studied effects of cation stoichiometry on the entropy‐driven reaction to form a single phase, but a fundamental exploration of the effects of anion stoichiometry and/or redox chemistry on electrical properties is lacking. Using near‐edge X‐ray absorption fine structure (NEXAFS) and electrical measurements, we show that oxidizing thin film samples of (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O affects primarily the valence of Co, leaving the other cations in this high‐entropy system unchanged. This oxidation increases electrical conduction in these thin films, which occurs via small polaron hopping mediated by the Co valence shift from 2+ to a mixed 2+/3+ state. In parallel, we show that bulk samples sintered in an oxygen‐rich atmosphere have a lower activation energy for electrical conduction than those equilibrated in a nitrogen (reducing) atmosphere. Combining feasible defect compensation scenarios with electrical impedance measurements and NEXAFS data, we propose a self‐consistent interpretation of Co redox‐mediated small polaron conduction as the dominant method of charge transfer in this system.

Influence of the Cooling Rate at Thermal Sintering on the Structure and Magnetic Properties of Ferrite Ceramics

The influence of the cooling rate during sintering of lithium-titanium-zinc-manganese spinel ferrite on its structural, magnetic and electric characteristics was studied. The ferrite was sintered in air at 1283 K for 120 min. Cooling rates were 0.06 K/s and 7.8 K/s. It was established that the observed changes in the characteristics when using slow and quenching cooling are due to the different levels of the near-surface ferrite layers oxidation. For quench ferrite, the Curie temperature of 530 K, the activation energy of electrical conductivity of 0.35 eV in the bulk of the samples, and the magnetic anisotropy constant of 2.6·10-3 J/m3 (at 300 K) were obtained. Slowly cooled ferrite was characterized by higher values of Curie temperature (560 K), the magnetic anisotropy constant (2.9·10-3 J/m3), and the activation energy of electrical conductivity (0.80 eV).

Low temperature - Dielectric, impedance, and conductivity - Study for lanthanum nickelate-manganate ceramics

A solid-state reaction was applied to obtain lanthanum nickelate manganate ceramics. This double perovskite was sintered at TS = 1350 °C. An occurrence of monoclinic P21/n major phase of La2NiMnO6 at room temperature was confirmed by X-ray diffraction analysis. The minor phase of cubic Fm-3m of the MnNi6O8 phase was detected. Scanning electron microscopy (SEM) images exhibited agglomerated irregular grains of sizes ranging from ∼1 to 5 μm, separated by voids. The energy dispersion X-ray spectroscopy (EDS) method confirmed the occurrence of La, Mn, Ni, and O elements and the absence of other atoms. The Nyquist plots exhibited overlapped semi-circular-like arcs, attributed to grain and grain boundary effects at low temperature range. The imaginary impedance peak, which shifted when temperature and frequency increased, was attributed to the relaxation process. The activation energy Ea,τ = 0.10 eV and characteristic relaxation time τ0 = 1.49 ps for the relaxation process was estimated. The Bode plot helped to discern different mechanisms involved in the impedance observed in the low-temperature range. The conductivity scaling behavior confirmed the hopping mechanism of the small polarons. The estimated dc electrical conductivity activation energy, Edc, varied from 0.13 eV to 0.17 eV, depending on the temperature range. Variable range hopping of the small polaron model consistent with the structural disorder was appropriate in the low-temperature range. The dielectric loss response was explained in the framework of the conductivity effect. The non-coincidence of the peak positions of impedance Z″ and modulus M″ spectra confirmed the short-range motion of charge carriers. The manifestation of the magneto-dielectric effect was deduced.