Activation Energy Of Electrical Conductivity Research Articles

Impedance Spectroscopic Studies of B2O3-Substituted CeO2-Gd2O3 Systems

In this paper, the change in the conduction mechanism due to B2O3 addition in a ceria-based nanoceramic system is understood by studying the nature of conductivity and the variation of electric modulus function with frequency at different temperatures. The studies revealed that oxide ion conduction in the prepared system is prominent only after 500°C. The activation energy for electrical conduction and oxide ion hopping in the system is found to be 0.26 eV and 0.85 eV, respectively. The discrepancy in the values of the activation energies itself is evidence of a different mechanism other than oxide ion hopping occurring in the present sample. The electric modulus function shows two relaxation peaks at lower temperatures corresponding to short-range and long-range relaxation for the charge carriers. Relaxation energies for the processes are found to be 0.27 eV and 0.95 eV. This is evidence of the occurrence of Maxwell–Wagner relaxation phenomena in the ceramic system. Explicitly, thermally activated oxide ion migration, along with the relaxation of electrons at the site of the bound pair (B–Vo)· is observed in the prepared nanocrystalline system.

Relation Between Resistance Drift and Optical Gap in Phase Change Materials

AbstractThe optical contrast in a phase change material is concomitant with its structural transition. These two are connected by first recognizing that Friedel oscillations couple electrons propagating in opposite directions and supply an additional Coulomb energy. As the crystal switches phase, this energy acquires time dependence and the Landau‐Zener mechanism operates, steering population transfer from the valence to the conduction band and vice versa. Spectroscopy suggests that the oscillator energy E0 dominates the optical properties and a calculation involving the crystalline field and spin–orbit interaction yields good estimates for E0 of both structural phases. Further analysis relates the optical gap with the crystalline‐field energy as well as activation energy for electrical conduction. This last property characterizes the amorphous phase, thereby furnishing a link between the crystalline field and the activation energy and ultimately with the resistance drift exponent. Providing optical means to quantify resistance drift in phase‐change materials (PCMs) could circumvent the need for fabricating expensive devices and performing time consuming measurements.

Study of the reaction of 1,4-benzoquinone with aniline oligomers and benzidine

Polymers and oligomers containing fragments of aniline oligomers and benzidine connected with p-benzoquinone have been synthesized. The UV, NMR and IR spectral data, as well as termal stubilities, of obtained compounds were studied. Some of obtained compounds were oxidized by K2S2O8 using different molar ratio. Electrical conductivities and conductivity activation energies of iodine and hydrochloric acid doped polymers were determined.

Temperature dependence and activation energy of electrical conduction in an engineered cementitious composite

The electrical impedance of an engineered cementitious composite was measured over the temperature range 7-60°c and data are presented over the frequency range 20Hz-1MHz. The work has highlighted that the resistive and reactive components of the complex impedance both displayed an inverse relationship with temperature. When presented in an Arrhenius format, the bulk resistance displayed a linear response over the entire temperature range studied and the activation energy, Ea , for electrical conduction was evaluated as 21.7 kJ/mol (0.22 eV/ion).

Macroscopic and microscopic electrical properties of a ferrofluid in a low frequency field

Using the complex dielectric permittivity measurements, in the frequency range 20 Hz – 2 MHz and at temperatures between (25–70)∘C, the polarizability (α), the electric modulus (M) and the electrical conductivity (σ), of a ferrofluid sample, were determined. The results enabled the computation of the thermal activation energy of electrical conduction, the obtained value being approximately equal, at 0.15 eV. By eliminating the losses arising from electrical conduction, we highlighted the existence of a Schwarz type dielectric relaxation, in the sample, at the frequency above 5 kHz. These results allowed, for the first time, the evaluation of the mechanical mobility, u, of the ions on the particle surface, resulting in a value of, u=3.4⋅108 m/sN. Knowledge of macroscopic and microscopic electrical properties is useful in explaining the dielectric polarization mechanisms and relaxation processes of ferrofluids, and also in the use of ferrofluids in technological and biomedical applications.

Citrate/nitrate combustion synthesis and electrical properties of rare earth co-doped Ce0.8Gd0.2−xNdxO1.90 electrolyte materials

In this study, effects of neodymium doping on the electrical properties of gadolinium-doped ceria were investigated. Ce0.8Gd0.2−xNdxO1.90 (x = 0.0–0.20) powders were prepared by citrate–nitrate combustion. Phase identification and morphology were carried out by XRD and SEM, respectively. All powder samples calcined at 600 °C were found to be ceria-based solid-solutions with a fluorite-type structure. The powders were isostatically cold-pressed and sintered in air at 1400 °C for 6 h to attain a sintered density of about 95% of the theoretical value. Electrical conductivity of the gadolinium-doped ceria pellets in air was studied as a function of temperature in 300–800 °C temperature range, utilizing two-probe electrochemical impedance spectroscopy. Ce0.80Gd0.12Nd0.08O1.90 showed higher electrical conductivity and lower activation energy (0.64 eV) than single element-doped (Gd or Nd-doped) ceria at 700 °C. Thus, it can be indicated as a possible candidate to function as an electrolyte in intermediate temperature solid oxide fuel cells.

Electrical conductivity and breakdown properties of some erbium oxide doped phosphovanadate glasses

Electrical conductivity and breakdown properties have been investigated for 70%V2O5·(30–x)%P2O5·x%Er2O3 glasses with (0 ≤ x ≤ 0.9). The conductivity measurements are carried out at frequency range from 80 to 3 × 106 Hz, and at temperature range from 303 to 463. The dc electrical conductivity (σdc) and dc activation energy (Edc) are shown to be relatively sensitive to the composition. σdc is found to vary between 3 × 10−4 and 0.024 Ω−1 m−1, and Edc is estimated to be in the range 0.36–0.44 eV. On the other hand, σac is found to vary between 7 × 10−4 and 0.15 Ω−1 m−1. Both σdc and σac are discussed according to the multi phonon hopping process of weak electron-lattice coupling, they are found to be proportional to Tpwith the exponent p between 11.5 and 13.15. All the samples exhibit a threshold type switching with a maximum current of about 3 mA. All the samples are found to present breakdown properties at different critical voltages. The threshold voltage (Vth) values are affected by ambient temperature, sample thickness and composition ratio. Measured surface temperature during the switching cycles and the calculated core temperature confirm the repeatedly switching of the samples without any internal thermal destruction occur.

Dielectric properties of Aurivillius Bi5Ti3Fe0.5Ni0.5O15 ceramics

A new Aurivillius Bi5Ti3Fe0.5Ni0.5O15 compound was prepared using the conventional ceramic technology. The features of the temperature dependences of the dielectric constant ε′ and the dielectric loss tgδ were studied in the temperature range from 300 to 750 K. These dependences indicate a significant conductivity contribution to the ε′ and tgδ as well as the presence of a relaxation process. The ac conductivity was calculated, the hodograph of the impedance of the sample was plotted, and the activation energy of the dielectric relaxation process was estimated. A comparison of the activation energy of the total electrical conductivity and electrical conductivity in the grain bulk showed that the electrical conductivity of the studied compound is mainly due to the electrical conductivity of the grains boundaries.

Lignosulfonates as charge carriers and precursors forthe synthesis of nanoparticles

The conductometry method was used to study the polyelectrolyte behavior of lignosulfonates in an aqueous solution. Electrical conductivity was found to be a complex function of concentration (8.5 ∙ 10–5– 9.0 ∙ 10 –2 mol/dm3), molecular weight of lignosulfonates (Mw 9250, 46,300), cation nature (Na+, Cа2+), as well as association of free counterions with polyion and temperature (288–353 K). It was shown that the molar electrical conductivity in the Kohlrausch coordinates decreases with increasing polymer concentration due to a decrease in the mobility of dissociated counterions under the action of the electrostatic potential of the macroion. In lignosulfonates solutions, an increase in temperature causes an increase in the number of particles capable of charge transfer. An inflection point was found on the temperature dependences of the electrical conductivity of high molecular weight samples, indicating structural changes in macromolecules. The reasons for this behavior of high molecular weight lignosulfonates in an aqueous solution were discussed. The activation energy of electrical conductivity was calculated, the average value of which is 14.24 kJ/mol for low molecular weight samples, and 12.17 kJ/mol for high molecular weight samples up to the inflection point and 16.49 kJ/mol after. It was found that a bimodal distribution of particles, as well as the formation of a double electric layer on their surface, is characteristic of lignosulfonates obtained. Solvent replacement (nanoprecipitation) yielded lignosulfonate nanoparticles ranging in size from 40 to 90 nm. The shape of the obtained particles is determined by the nature of organic solvent and is independent of lignosulfonates molecular weight. When using ethyl alcohol as a co-solvent, spherical nanoparticles were obtained, and pyramidal lignosulfonate nanoparticles were prepared when using acetone.

Growth mechanism and transport properties of chemically deposited PbxCd1-xS thin film’s photoelectrochemical (PEC) solar cell

The dc conductivity and thermoelectric power of PbxCd1-xS (0 ≤ x ≤ 1) thin films were fabricated and investigated for the solar cell efficiency. The deposition parameters such as time, concentration, temperature, and pH of the solution were optimized to get superior quality thin films. The optical properties revealed that the band gap of the films decreased as the composition parameter ‘x’ increased. XRD results show the films are polycrystalline with an individual hexagonal (CdS) and cubic (PbS) structure. FESEM revealed that the films have uniform surface morphology over the entire substrate. The crystallite size measured by XRD and FESEM studies was found to be varied with composition ‘x’. EDXS shows a compositional analysis of prepared films.The four probe technique is used to estimates the electrical conductivity (σ) and thermal activation energy at room temperature. The TEP data are analyzed to calculate electron carrier density (n) and mobility (μ) of PbxCd1-xS thin films at a temperature of 45 °C to 110 °C. In the photoconduction study, it is observed that dark current rises linearly with applied voltage and photocurrent varies with applied voltage. PbxCd1-xS thin film’s PEC solar cell was characterized by determining the open-circuit voltage (Voc), short circuit current (Isc), maximum power (Pmax), fill factor (ff) and efficiency (ɳ %). The area 0.2 cm2 is selected for the sample cell and was illuminated by a 90 mW/cm2 solar radiation. From the I–V higher magnitudes fill factor 37.02% and conversion efficiency 0.10940% is obtained for composition Pb0.2Cd0.8S.

Influence of cation interdiffusion on electrical properties of doped ceria/lanthanum silicate composite

La-doped ceria (LDC)/lanthanum silicate (LS) and Ga-doped ceria (GDC)/LS composites were prepared, and the influence of cation interdiffusion during co-firing on the electrical properties of composites was investigated. The electrical conductivity of GDC/LS was lower than that of LDC/LS despite the higher conductivity of GDC compared to LDC. The crystal phases of LDC/LS and GDC/LS were detected as fluorite-type cubic ceria (Fm3‾m) and a hexagonal lanthanum silicate (P63/m), respectively, by X-ray diffraction (XRD). From energy dispersive X-ray spectroscopy (EDS) measurements, it was found that the compositions of the ceria and silicate phases in LDC/LS were nearly stoichiometric after co-firing. In contrast, interdiffusion between Gd3+ in the ceria phase and La3+ in the silicate phase was recognized for the GDC/LS. The compositions of the ceria and silicate phases in GDC/LS after co-firing were estimated as Gd0.035La0.065Ce0.9O1.95 and La7.910Gd0.423(SiO4)6O0.5, respectively. The Gd3+ substitution for La3+ in the silicate phase in GDC/LS decreased the amounts of 4f site cations. Then, the lattice parameter of the silicate phase decreased. As a result, the decrease in electrical conductivity of GDC/LS is attributed to the decrease in the oxide anion at the 2a site, which is a conduction carrier. It was found from Raman spectroscopy that cation interdiffusion decreased the symmetry mode of the SiO4 tetrahedra for the silicate phase in GDC/LS and brought about increases in the activation energy of electrical conductivity for GDC/LS.

Pen plotter printing of Co3O4 thin films: features of the microstructure, optical, electrophysical and gas-sensing properties

Abstract Сombining the sol–gel method and pen plotter printing, using the hydrolytically active heteroligand complex [Co(C5H7O2)2-x(C4H9O)x] as a component of a new functional ink, Co3O4 thin films were produced on the surface of substrates of various types. The influence of synthesis conditions and print modes on the microstructure, optical, electrophysical and sensor properties of planar nanomaterials was comprehensively studied. The optical band gap energies associated with charge transfer for transitions O2-→Co3+ and O2-→Co2+ of the obtained thin films were evaluated. Using Kelvin probe force microscopy and impedance spectroscopy, the electrophysical characteristics (the electronic work function of the film surface, the temperature dependence of electrical conductivity, and the activation energy of electrical conductivity) of the obtained Co3O4 films were determined. The sensitivity of printed cobalt(II, III) oxide thin films with respect to various gases (Н2, СН4, СО and NO2) was studied. It was established that the obtained samples demonstrated the highest sensor response when detecting CO and NO2 in the operating temperature range of 150–200°С. The prospects of the proposed synthesis method and printing technology when forming Co3O4 thin-film nanostructures to create electrodes of supercapacitors and receptor components of resistive CO and NO2 gas sensors were shown.

Spin–state transition in the layered barium cobaltite derivatives and their thermoelectric properties

Ba1.9Me0.1Co9O14 (Me = Ba, Sr, Ca) (BCO) layered cobaltites were prepared by means of solid-state reactions method. Crystal structure, microstructure, thermal expansion, electrical conductivity, and thermo-EMF for the obtained oxides were studied; the values of their linear thermal expansion coefficient, activation energy of electrical transport, and power factor values were calculated. It was found that BCO are p-type semiconductors, in which the spin-state transition occurs within 460-700 K temperature interval due to change in spin state of cobalt ions, which accompanied the sharp increase in electrical conductivity, activation energy of electrical conductivity, and linear thermal expansion coefficient, while thermo-EMF coefficient decreased. Partial substitution of barium by strontium or calcium in BCO leads to the increase in spin-state transition temperature and electrical conductivity of the samples, and, at the same time, thermo-EMF coefficient; consequently, their power factor values decrease.

Electrical conductivities and microstructures of LSM, LSM-YSZ and LSM-YSZ/LSM cathodes fabricated on YSZ electrolyte hollow fibres by dip-coating

Lanthanum strontium manganite – La0.80Sr0.20MnO3 (LSM), LSM-Yttria stabilised zirconia (LSM-YSZ) composite and LSM-YSZ/LSM double-layer cathodes were separately fabricated on Yttria stabilised zirconia (YSZ) electrolyte hollow fibres by dip coating; their electrical conductivities and microstructures were then determined by the direct current four-probe method and scanning electron microscopy (SEM), respectively. Excellent cathode-electrolyte and cathode-cathode adhesion without delamination were achieved by the dip-coating fabrication method. The apparent electrical conductivities of porous LSM, LSM-YSZ and LSM-YSZ/LSM cathodes manufactured on YSZ hollow fibre by dip-coating and sintered at various temperatures in the range 1273–1473 K for 3 h, were 1.8 × 103–5.5 × 103 S/m, 0.32–209 S/m and 1.3 × 103–5.5 × 103 S/m, respectively, at measurement temperatures of 673–1073 K. The operating temperature dependence of the apparent electrical conductivity of the LSM, LSM-YSZ and LSM-YSZ/LSM cathodes was defined by the Arrhenius equation for electrical conductivity. The activation energies for electrical conductivity were derived as 0.106–0.147 eV, 0.83–0.94 eV, and 0.104–0.146 eV for the LSM, LSM-YSZ and LSM-YSZ/LSM cathodes, respectively. The LSM-YSZ and LSM-YSZ/LSM cathodes were strongly influenced by the YSZ and LSM phases, respectively.

Mechanical and electrical parameters of a-Ge-Se-Sn glasses

The present work reports the effect of Sn addition on the electrical and mechanical properties of the GeSe2 glass. The measured ultrasonic velocities are used to estimate the elastic moduli and Debye temperature (TD) of the (GeSe2)1−xSnx glasses. The temperature dependence of the electrical parameters and thermo-electrical power of the studied glasses was determined over the temperature range of 300–450 K. The Young's modulus (Y) and bulk modulus (K) as well as the activation energy for the dark electrical conduction (ΔEdc) were correlated with the glass transition temperature (Tg). The observed changes were explained in terms of the distribution of the formed chemical bonds in each glass sample. ΔEdc values decrease while Y and K increase with the increase of Sn content, i.e. the addition of Sn content to the GeSe2 glass enhances both the electrical conductivity and mechanical moduli of Ge-Se-Sn glassy films.

Quercetin and rutin mixtures with alcohols: Spectroscopic and conductometric studies

The interactions of flavonoids quercetin and its glycoside, rutin with the short chain alcohols (methanol, ethanol, propanol) were investigated by means of the fluorescence spectroscopy, UV–Visible spectrometry and conductivity measurements. From the experimental data the quantities such as Stern-Volmer quenching constant, bimolecular quenching constant, modified Stern-Volmer constant, effective quenching constant, apparent association constant, activation Energy for electrical conduction were determined. The obtained results show that the mixtures of quercetin with propanol and rutin with ethanol are characterized by their strongest interactions.

Impact of Sn4+ Substitution at Cr3+ Sites on Thermoelectric and Electronic Properties of p-Type Delafossite CuCrO2

The effects of Sn4+ substitution at Cr3+ sites on the thermoelectric and electronic properties of p-type delafossite CuCrO2 have been studied. CuCr1−xSnxO2 (x = 0.01, 0.03) samples were prepared via conventional solid-state reaction. The Seebeck coefficient results confirmed that all the samples exhibited p-type conduction. X-ray photoelectron spectroscopy verified the presence of Sn4+ ions and the appearance of mixed-state Cr3+/Cr2+ ions. The experimental results revealed that addition of Sn impacted the electrical conductivity due to the mixed Cu1+/Cu2+ states while the Seebeck coefficient was affected by the mixed Cr3+/Sn4+ states. The electrical conductivity was governed by the polaron hopping mechanism, and the large Seebeck coefficient was controlled by the spin and orbital degeneracy of the mixed Cr3+/Sn4+ ions. The electrical conductivity activation energy values were 0.410 eV and 0.407 eV while the thermal activation energy values were 0.208 eV and 0.160 eV, for x = 0.01 and 0.03, respectively. The results confirm that Sn4+ substitution at Cr3+ sites impacted the Seebeck coefficient and electronic behavior of delafossite CuCrO2 oxide even for low dopant levels of x = 0.01 and 0.03, resulting in p-type conduction and optically conducting materials.

Electromechanical losses in carbon- and oxygen-containing bulk AlN single crystals

Bulk single-crystalline aluminum nitride (AlN) is potentially a key component for low-loss high-temperature piezoelectric devices. However, the incorporation of electrically active impurities and defects during growth of AlN may adversely affect the performance of piezoelectric resonators especially at high temperatures. The electrical conductivity and electromechanical losses in bulk AlN single crystals are analyzed in the temperature range of 300–1200 K with respect to various contents of growth-related impurities in them. For AlN with [O]/[C] ≤ 1, an increase of electrical conductivity due to thermal activation of charge carriers in the temperature range of 850–1200 K has been observed and was determined to be a major contribution to electromechanical losses Q−1 rising up to maximum values of about 10−3 at 1200 K. As the oxygen content in AlN increased, the magnitude and the activation energy of high-temperature electrical conductivity increased. In oxygen-dominated AlN, two major thermally activated contributions to electromechanical losses were observed, namely, the anelastic relaxations of point defects at temperatures of 400–800 K and electrical conductivity at T > 800 K.

Impedance spectroscopy study of K+ substituted single crystalline BaTi2O5

K+-ion substituted single crystalline BaTi2O5, Ba1−xKxTi2O5−z (x = 0 to 0.006), was prepared by floating zone method. The effect of K+-ion substitution on the electrical properties of Ba1−xKxTi2O5−z was studied using impedance spectroscopy. Ba1−xKxTi2O5−z showed ferroelectricity and ion/hole mixed conduction in the b-direction. With increasing K+ content from x = 0 to 0.006, the Curie temperature (Tc) decreased from 752 to 722 K, and permittivity decreased from 18,600 to 3970. The ionic conduction behavior (ion blocking at low frequency region) became significant by the K+ substitution showing maximum at x = 0.003. The electrical conductivity of Ba1−xKxTi2O5−z increased with increasing oxygen partial pressure, and was almost 100 times higher than that of BaTi2O5 in the temperature range of 500–650 K. The activation energy of electrical conductivity was 0.8–1.5 eV.

THERMAL EXPANSION, ELECTROTRANSPORT AND DIELECTRICAL PROPERTIES OF Bi4(Ti,Nb,Fe)3O12 SOLID SOLUTIONS

The Bi4Ti3–2xNbxFexO12 (0.05 ≤ x ≤ 0.15) titanates were prepared using ceramic method. Their structure and physicochemical properties were studied. Compounds were p-type semiconductors, which electrical conductivity, Curie temperature, dielectric constant, and dielectric losses decreased, but lattice constants, thermo-EMF coefficient and sinterability did not changed at partial replacing of titanium by niobium and iron. Introduction of niobium and iron oxides into ceramics based on layered Bi4Ti3O12 lead to the sharp decreasing in its grains size. The transition of ceramics from ferroelectric to paraelectric state was accompanied by a stepwise increase in linear thermal expansion coefficient (LTEC) (from (9.63–9.81)·10–6 K–1 to (12.71-14.67)·10–6 K–1 and by decrease in the activation energy of DC electrical conductivity (from 1.13–1.52 eV to 0.72–0.99 eV). Electrical resistivity of ceramics was determined by electrical resistivity of grains, relaxation processes in it were of a non-Debay type, while the activation energy of relaxation for Bi4Ti3–2xNbxFexO12 titanates, found from impedance spectroscopy (1.01–1.05 eV), was close to the value activation energy of their intragrain conductivity (0.85–0.97 eV). The frequency dependences of AC electrical conductivity obeyed Jonscher’s power law σ ~ νn, where n < 1 and increased with temperature, which indicated that charge transfer in the ceramic was accomplished by ions translating over small distances, which was accompanied by small polarons hopping charge transfer.