Type Of Electrical Conductivity Research Articles

Oxidation behavior of multiwall carbon nanotubes with different diameters and morphology

Multiwall carbon nanotubes (MWNT) with three medium diameters (20–22, 9–13, and 6–8nm) and different morphology were chemically oxidized using concentrated nitric acid, mixture of nitric and sulfuric acids (“mélange” solution) and mixture of sulfuric acid and hydrogen peroxide (“piranha” solution). Influence of MWNT type and structure as well as type of oxidizer on the surface composition and structure of nanotubes after oxidation was investigated. Acid–base titration, X-ray photoelectron spectroscopy and thermal gravimetric analysis were used for quantitative and qualitative investigation of surface group composition of initial and oxidized nanotubes. Amount of oxygen-containing groups on the surface of oxidized MWNT depends on the type of initial MWNT. It was found that ratio of different oxygen containing groups is less dependent on the type of oxidizer. Electrophysical properties of initial and oxidized nanotubes were investigated in temperature range 4–293K and main types of electrical conductivity were determined. It was shown that oxidation results in decrease in electrical conductivity of all samples with simultaneous change in the conductivity mechanism. Dispersive behavior of initial and oxidized nanotubes in different commonly used solvents was investigated. It was shown that oxidation leads to the improvement of sedimentation stability of MWNT in polar solvents.

Observation of conductivity type conversion in undoped ZnO films grown by pulsed laser deposition on silicon (100) substrates

We report a conductivity type conversion of ZnO films from n to p-type for films grown on silicon (100) substrates by pulsed laser deposition under low constant oxygen overpressure. Conductivity conversion is attributed to a competition between donor and acceptor-like native defects correlating with growth conditions and surface differences between phosphorus doped n-type and boron doped p-Si substrates. Effects of growth temperature on intrinsic defects including oxygen vacancies, zinc vacancies and hydrogen impurity contamination are discussed. Our results show that the interplay of defect-related centers is critical to the electrical behavior and conductivity type of ZnO grown on Si substrates.

Impedance Spectroscopy of Ba<sub>5</sub>GdTi<sub>3</sub>V<sub>7</sub>O<sub>30</sub>

The polycrystalline sample of Ba5GdTi3V7O30 , a member of tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray diffraction analysis suggests the formation of single-phase compound with orthorhombic structure. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (102- 106 Hz) at different temperatures. The real and imaginary part of complex impedance traces semicircle(s) in the complex plane. The temperature dependent plots reveal the presence of both bulk and grain boundary effects. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The modulus analysis suggests a possible hopping mechanism for electrical transport processes of the material. The nature of variation of dc conductivity suggests Arrhenius type of electrical conductivity.

Irregular Electrical Conduction Types in Tin Oxide Thin Films Induced by Nanoscale Phase Separation

The development of p‐channel tin oxide thin‐film‐transistors spurred the research into microstructural analysis of tin oxide phases and control of conduction type, as it is widely known that tin oxide thin films exhibit both n‐ and p‐type conduction depending on growth conditions. This study reports the relationship between the microstructural properties and the ambiguity of the electrical conduction type observed in nonstoichiometric tin oxides. Nonstoichiometric tin oxide thin films have been produced by RF magnetron sputtering with a dependence on the growth gas atmosphere. The crystal phase of the tin oxide deposited under low ambient oxygen content was mainly SnO1+x with relatively stable p‐type conduction. On the other hand, for deposition under high ambient oxygen content, phase separation with structural modulation in the tin oxide film occurred in SnO‐like and SnO2‐like regions. These phases with different conduction types caused electrically unstable dual conduction types in the tin oxide films, despite their low electrical resistivity.

Phenazineoxonium chloranilatomanganate and chloranilatoferrate: synthesis, structure, magnetic properties, and Mössbauer spectra

Crystalline compounds (H3O)2(phz)3M2(C6O4Cl2)3·(CH3COCH3) n ·(H2O) n (n = 0−2, M = Mn (1), Fe (3)) were obtained in an acetone-water-tetrahydrofuran medium by the reaction of metal sulfates with chloranilic acid and phenazine (phz). The molecular and crystal structure of 1 was studied by X-ray diffraction at 300, 200, and 150 K. The crystal structure is composed of polymeric cationic [(H3O)2(phz)3] n 2n+ and anionic [Mn2(C6O4Cl2)3] n 2n− layers having honeycomb structure and stacked in such a way that open-ended through-going channels accommodating H2O and CH3COCH3 solvent molecules are formed; the H3O+ cations in the crystal structure are disordered. Magnetic studies indicate antiferromagnetic coupling of Mn2+ ions through chloranilate ligands; transition to a magnetically ordered state occurs at T = 5 K. According to powder X-ray diffraction data, complex 3 is isostructural with compound 1 but differs crucially from 1 in the electronic structure. According to Fe57 Mossbauer spectroscopy, complex 3 exists in delocalized mixed-valence Fe2+/Fe3+ state and, as a consequence, shows ferromagnetic character of magnetic correlations and semiconductor type of electrical conductivity. These features were ascribed to the valence tautomerism Fe2+ + (C6O4Cl2)2− → Fe3+ + (C6O4Cl2)·3−, which was observed for the first time for iron in a honeycomb structure.

Multifunctional thick-film structures based on spinel ceramics for environment sensors

Temperature sensitive thick films based on spinel-type NiMn2O4-CuMn2O4-MnCo2O4 manganites with p- and p+-types of electrical conductivity and their multilayer p+-p structures were studied. These thick-film elements possess good electrophysical characteristics before and after long-term ageing test at 170 °C. It is shown that degradation processes connected with diffusion of metallic Ag into film grain boundaries occur in one-layer p-and p+-conductive films. Some part of the p+-p structures were of high stability, the relative electrical drift being no more than 1 %.

Low-temperature magnetic and electrical transport properties of some ternary Ce–Rh–Si compounds

Five novel cerium-based ternaries Ce 2Rh 3.1Si 0.9, Ce 4Rh 12Si, Ce 8Rh 21.9Si 3.1, CeRh 1.82Si 0.18 and CeRh 3Si 0.125 were studied by means of magnetic susceptibility and electrical resistivity measurements. All these phases were found to be Pauli paramagnets with metallic type of electrical conductivity.

Unipolar resistive switching in insulating niobium oxide film and probing electroforming induced metallic components

We have observed unipolar-type resistance switching in an ultrathin niobium oxide film. An analysis of the temperature dependence of the resistance switching transport revealed that low-resistance state showed a type of electrical conduction typically observed in metals. The modification in chemical binding states of the film in different resistance states was studied using x-ray photoelectron spectroscopy. The analysis of XPS showed that metallic suboxides NbOδ (δ ≪ 2), decomposed from some of Nb2O5 and NbO2 components of the film, were created after electroforming process, suggesting that the metallic suboxides are constituting elements of metallic channels in the low resistance state.

Nanocrystalline p-type-cuprous oxide thin films by room temperature chemical bath deposition method

Nanocrystalline cuprous oxide (Cu 2O) thin films were synthesized on amorphous glass substrate by using simple room temperature chemical route namely, chemical bath deposition (CBD) method. The deposition kinetics played important role to get good quality nanocrystalline films with uniform thickness. The structural, surface morphological, optical and electrical properties of the films were investigated. Crystallization and growth processes obtained micro-spherical shaped grains of Cu 2O due to agglomeration of smaller nanoparticles. An optical and electrical characterization was performed to study the optical band gap and type of electrical conductivity of the film.

Structural, ferroelectric and impedance spectroscopy properties of Y3+ modified Pb(Fe0.5Nb0.5)O3 ceramics

Some ceramic samples of Pb1−xYx(Fe0.5Nb0.5)1−x/4O3 (PYFN) (0.00≤x≤0.08) were synthesized by a mixed oxide route. X-ray diffraction patterns of all the above samples confirm the formation of single phase material crystallizing in monoclinic structure. Dielectric properties (εr and tanδ) were analyzed in a wide temperature (30–350°C) and frequency range (100Hz–1MHz). Ferroelectric properties of these compounds were confirmed from polarization (P–E hysteresis loop) measurements at room temperature. All the room temperature hysteresis loops of PYFN ceramics were well simulated using the ferroelectric capacitor model. Yttrium substitution resulted in notable enlargement of room temperature remnant polarization (2Pr). The 2Pr of PYFN (x=0.02) reaches to a large value (23μC/cm2), which is nearly 5 times greater than that of PFN ceramic (4.6μC/cm2). All the compounds exhibits negative temperature coefficient of resistivity (NTCR) type behavior as that of semiconductors. Dc conductivity (estimated via bulk resistivity) variation with temperature of all the samples follows Arrhenius type of electrical conductivity.

Preparation and thermoelectric properties of BP films on SOI and sapphire substrates

The chemical vapor deposited (CVD) BP films on Si(100) (190 nm)/SiO x (370 nm)/Si(100) (625 μm) (SOI) and sapphire (R-plane) (600 μm) substrates were prepared by the thermal decomposition of the B2H6–PH3–H2 system in the temperature range of 800–1050 °C for the deposition time of 1.5 h. The BP films were epitaxially grown on the SOI substrate, but a two-step growth method, i.e., a buffer layer at lower temperature and sequent CVD process at 1000 °C for 1.5 h was effective for obtaining a smooth film on the sapphire substrate. The electrical conduction types and electrical properties of these films depended on the growth temperature, gases flow rates and substrates. The thermal conductivity of the film could be replaced by the substrate, so that the calculated thermoelectric figure-of-merit (Z) for the BP films on the SOI substrate was 10−4–10−3/K at 700–1000 K. Those on the sapphire substrate were 10−6–10−5/K for the direct growth and 10−5–10−4/K for the two-step growth at 700–900 K, indicating that the film on a sapphire by two-step growth would reduce the defect concentrations and promote the electrical conductivity.

Effect of deposition time on structural, electrical, and optical properties of SnS thin films deposited by chemical bath deposition

The effect of deposition time on the structural, electrical and optical properties of SnS thin films deposited by chemical bath deposition onto glass substrates with different deposition times (2, 4, 6, 8 and 10 h) at 60 °C were investigated. The obtained films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and optical absorption spectra. All deposited films were polycrystalline and had orthorhombic structure with small crystal grains. Their microstructures had changed with deposition time, and their compositions were nearly stoichiometric. Electrical parameters such as resistivity and type of electrical conduction were determined from the Hall Effect measurements. Hall Effect measurements show that obtained films have p-type conductivity and resistivity values of SnS films have changed with deposition time. For allowed direct, allowed indirect, forbidden direct and forbidden indirect transitions, band gap values varied in the range 1.30–1.97 eV, 0.83–1.36 eV, 0.93–1.49 eV and 0.62–1.23 eV, respectively.

Crystal structure and electrical properties study of 4-aminopyridinium chloridobismuthate (III) (C5N2H7)4.HBi2Cl11

The crystal structure of (C5N2H7)4.HBi2Cl11 has been determined at room temperature by single crystal X-ray diffraction. The compound crystallizes in the triclinic system with Pī space group. The crystal structure consists of two asymmetric inequivalent molecules of 4-aminopyridinium and anionic HBi2Cl11 chains. The HBi2Cl11 anionic chains stacked along the a-axis are formed with Bi2Cl11 dimers connected to each other via hydrogen atoms. The crystal packing is stabilized with N–H...Cl hydrogen bonds connecting aminopyridinium units to the HBi2Cl11 anionic chains. The title compound exhibits an order–disorder phase transition at 338 K. The AC electrical conductivity properties of (C5N2H7)4.HBi2Cl11 compound have been investigated by means of impedance spectroscopy measurements over wide ranges of frequencies and temperatures, 200 Hz to 5 MHz and 303 to 418 K, respectively. Detailed analysis of the impedance spectrum suggests that the electrical properties of the material are strongly temperature dependent. The frequency-dependent conductivity data were fitted in the Jonscher's law: $$ \sigma \left( \omega \right) = \sigma (0) + A{\omega^n} $$ . The nature of variation of DC conductivity suggests Arrhenius type of electrical conductivity.

Growth of CdS Layers to Develop All-Electrodeposited CdS/CdTe Thin-Film Solar Cells

The electrodeposition (ED) of CdS (continuous process) was investigated in detail with the aim of replacing chemical bath deposited (CBD) CdS (batch process) from the solar cell production process. This avoids the daily production of toxic waste and, hence, drastically reduces manufacturing cost. Material studies were carried out using voltammetry, X-ray diffraction, X-ray fluorescence, optical absorption, photoelectrochemical studies, and scanning electron microscopy. The main difference between the two processes is in the structure of material layers: ED-CdS is hexagonal while CBD-CdS is cubic. All other properties, the bandgap (2.42 eV), the electrical conduction type (n-type), and the grain size , remain very similar. The comparison of initial solar cell devices shows that ED-CdS layers have similar or superior performance in thin-film CdS/CdTe solar cells.

Influence of oxygen treatment on transport properties of PbTe:In polycrystalline films

In this work, the oxygen treatment of 1 μm thick n-type PbTe:In films was studied. Two main processes induced during the thermal treatment in oxygen atmosphere were identified. The inversion of the type of electrical conductivity in PbTe:In films from n- to p-type was observed after the thermal treatment in oxygen ( T a=400 °C). This effect is related to indium segregation at the film surface. The photoconductivity demonstrated in PbTe:In films after oxygen treatment is due to oxygen diffusion along the grain boundaries and the creation of potential relief, which separates electron–hole pairs at the boundaries under light illumination.

Measurement of electrical conductivity of pore water in saturated sandy soils using time domain reflectometry (TDR) measurements

Studying solute transport in soils is hampered by a lack of technology for continuously monitoring ionic concentration of contaminants. The electrical conductivity of pore water is a strong indicator of ionic concentration of contamination in soil. Using the bulk electrical conductivity of a soil measured by time domain reflectrometry (TDR) to predict the soil pore-water electrical conductivity appears to be a promising technique. This study presents a new method for estimating the pore-water electrical conductivity of saturated sandy soils using a single TDR test. The effects of pore-water electrical conductivity, temperature, porosity, and ionic types on the electrical conductivity of soil were studied. An average value of the exponent in the Archie’s Law was found to be 1.457 for the saturated sandy soils used in this study. A laboratory model infiltration test was also conducted with continuous monitoring of the electrical conductivity of the pore water by TDR. The results showed that TDR is able to provide a reasonably accurate estimation of the electrical conductivity of pore water. Consequently, it may be possible to monitor the in situ ionic contamination in saturated sandy soils using TDR technology.

Temperature Sensitive Spinel-Type Ceramics in Thick-Film Multilayer Performance for Environment Sensors

sition Cu0:1Ni0:1Co1:6Mn1:2O4 (with p + -types of electrical conductivity), Cu0:1Ni0:8Co0:2Mn1:9O4 (with p-types of electrical conductivity) and their multilayer p + -p structures were fabricated and studied. These thick-film elements possess good electrophysical characteristics before and after long-term ageing test at 170 ‐ C. It is shown that degradation processes connected with diusion of metallic Ag into film grain boundaries occur in one-layer p- and p + -conductive thick films. The p + -p structures were of high stability, the relative electrical drift was not greater than 1%.

AC conductivity analysis and dielectric relaxation behavior of [N(C3H7)4]2Cu2Cl6

Abstract The AC electrical conductivity and the dielectric relaxation properties of the [N(C3H7)4]2Cu2Cl6 compound have been investigated by means of impedance spectroscopy measurements over a wide range of frequencies and temperatures, 100 kHz–5 MHz and 303–403 K, respectively. Besides, a detailed analysis of the impedance spectrum suggested that the electrical properties of the material are strongly temperature dependent. Nyquist plots (Z″ versus Z′) are well fitted to an equivalent circuit model which consists of a parallel combination of a bulk resistance Rb and constant phase elements CPE. The frequency-dependent conductivity data were fitted in the modified power law: σ ac ( ω ) = σ ( 0 ) + A ω n 1 + A ω n 2 The nature of variation of DC conductivity suggests Arrhenius type of electrical conductivity. Furthermore, the modulus plots can be characterized by full width at half height or in terms of a non-experiential decay function ϕ(t) = exp(−t/τ)β. Besides, the activation energy responsible for relaxation has been evaluated and found to be close to the DC conductivity.

Structural and impedance spectroscopic studies of samarium modified lead zirconate titanate ceramics

The polycrystalline samples of Pb1−xSmx(Zr0.60Ti0.40)1−x/4O3 (PSZT) where x=0.00, 0.03, 0.06 and 0.09 were prepared by a high-temperature solid-state reaction technique. The preliminary structural analysis using X-ray diffraction (XRD) data collected at room temperature has confirmed the formation of single-phase compounds in tetragonal crystal system. The morphological study of each sample using scanning electron microscope (SEM) has revealed that the grains are uniformly distributed through out the surfaces of the samples. Using complex impedance spectroscopy (CIS) technique, the electrical impedance and modulus properties of the materials were studied in a wide range of temperatures at different frequencies. The impedance analysis indicates the presence of bulk resistive contributions in the materials which is found to decrease on increasing temperature. The nature of variation of resistances with temperature suggests a typical negative temperature coefficient of resistance (NTCR) type behavior of the materials. The complex modulus plots clearly exhibits the presence of grain boundaries along with the bulk contributions in the PSZT materials. The presence of non-Debye type of relaxation has been confirmed by the complex impedance analysis. The variation of dc conductivity (bulk) with temperature demonstrates that the compounds exhibit Arrhenius type of electrical conductivity.

Electrical, thermal, and dielectric properties of PbZr1−xSnxO3 (0 ≤ x ≤ 0.3) single crystals

PbZrO3 and mixed PbZr1-xSnxO3 single crys- tals were grown by means of high temperature solution growth technique. A spontaneous crystallization was car- ried out in a Pt crucible, with PbO as a solvent. Electrical as well as thermal and dielectric properties were investi- gated in terms of Sn concentration. The measurements have been made in the large temperature range between 120 K and 800 K. The temperature dependences of cp for inves- tigated crystals can be approximated by the Einstein function and at high temperatures (cubic phase) cp reaches the classical Dulong-Petit limit value *125 J/mol K. From electrical measurements the ac and dc conductivity and the activation energies have been calculated and attributed to different types of electrical conductivity.