The effect of non-bridging oxygen on the electrical transport of some lead borate glasses containing cobalt

The effect of reducing oxygen in glass network on the electrical conductivity of system 50 B2O3 − 20 Pb3O4 − 10 Co3O4 − (20 − x)CaO − xCaCl2 (0 ≤ x ≤ 20 mol%) has thoroughly been investigated. This reduction was created by substituting oxygen ions with chloride ions. The measurements were conducted in the temperature range 320–560 K for fixed frequencies 0.1, 1, 10 and 100 kHz. It was found that at low temperatures, the dc conductivity (σ dc) is lower than the measured ac conductivity σ(ω), whereas σ(ω) and σ dc became equal at high temperature for all frequencies. The ac, dc conductivity as well as dc activation energies decrease with the gradual increase of CaCl2 content. The ac conductivity and the frequency exponent data showed that the correlated barrier hopping of electrons between both of oxidation states of cobalt ions (Co2+ and Co3+) is the most probable mechanism. The dielectric constant and the dielectric loss of the present glass system can be fitted to the Cole–Cole equation for all frequencies and temperatures.

AC conductivity and dielectric relaxation of Se80−xTe20Bix (x=6, 12) glasses

The present paper reports the ac conductivity and dielectric relaxation of Se80−xTe20Bix (x=6, 12) glasses at various temperatures and frequencies. It was found that ac conductivity increases on increase of frequency, temperature as well as Bi content. The increase in conductivity is due to the formation of lower energy Se–Bi and Te–Bi bonds which takes the system to a stable lower energy configuration. The values of frequency exponent (s) were calculated and it was found that samples obey CBH model of conduction. Density of states (N(Ef)) near the fermi level were calculated at different temperatures and it was found that addition of Bi increases the number of localised states in the tails which leads to increase in ac conductivity. Further, it was found that dielectric parameters increase with increase in temperature. However, a decrease in both dielectric constant (ε′) and dielectric loss ((ε″) was observed with increase in frequency. Beside this, dielectric relaxation time (τ) and activation energy of relaxation (∆Eτ) were also determined for both the samples under study and was found to be lower for Se68Te20Bi12 glass.

DIELECTRIC STUDIES IN Li2O AND CoO DOPED BOROPHOSPHATE GLASSES

Borophosphate glasses in the compositions, (B2O3)0.2 . (P2O5)0.3 . (Li2O) 0.5-X . (CoO) X, wherex = 0.05, 0.1, 0.15, 0.25, 0.30, 0.35, 0.40 and 0.45 were prepared at 1400K by following melt quenching method. Their amorphous nature was confirmed by XRD studies and was investigated for dielectric properties in the frequency range from 100Hz to 1MHz and temperature range from 300K to 573K. The conductivity was derived from the dielectric spectrum. The frequency exponent, s, dc and ac components of the conductivity were determined. The temperature dependence of conductivity at different frequencies was analyzed using Mott’s small polaron hopping model, and the high temperature activation energy has been estimated and discussed. The variation of conductivity and activation energy with composition revealed a changeover of conduction mechanism from predominantly ionic to electronic regime for mole fractions of CoO between 0.3 and 0.35. This is a new result. Hunt’s model has been employed to analyze frequency dependence of conductivity. Relaxation features of the dielectric properties have been extracted from the analysis of electric moduli with frequency. Activation energy for relaxation mechanism has been determined. Frequency exponent was found to be temperature dependent. Quantum mechanical theory and correlated barrier hopping models were found to be inadequate to explain frequency exponent behavior with temperature.For the first time that borophosphate glasses doped with Li2O and CoO were studied for dielectric properties and ac conductivity as a function of temperature and frequency and the data has been analysed thoroughly.Â

AC CONDUCTION PHENOMENON OF Li2O–WO3–B2O3 GLASSES DOPED WITH V2O5

The glass composition 40 Li 2 O –5 WO 3–(55−x) B 2 O 3: x V 2 O 5 for x = 0.2, 0.4, 0.6 and 0.8 is chosen for the present study. The glass samples were synthesized by conventional melt-quenching technique. The dielectric properties such as constant (ε′), loss (tan δ) and ac conductivity (σac) are carried out as a function of temperature (30–270°C) and frequency (102–105 Hz). The glass sample (at x = 0.6) exhibited highest ac conductivity (σac) and spreading factor (β) among all the samples. All glasses exhibited mixed conduction (both electronic and ionic) at high temperatures. The frequency exponent s denotes the ac conduction mechanism is associated with both QMT model (at low temperatures) and CBH model (at high temperatures).

Electrical and dielectric properties of kevlar - carbon hybrid fiber / epoxy laminated composites

This paper reports a.c., d.c. conductivity and dielectric behavior of Ep-hybrid composite with12 Vol.% Kevlar-Carbon hybrid . D.C. conductivity measurements are conducted on the graded composites by using an electrometer over the temperature range from (293-413) K. It was shown then that conductivity increases by increasing number of Kevlar –Carbon fiber layers (Ep1, Ep2, Ep3), due to the high electrical conductivity of Carbon fiber. To identify the mechanism governing the conduction, the activation energies at low temperature region (LTR) and at high temperature region (HTR) have been calculated. The activation energy values for hybrid composite decrease with increasing number of fiber layers. The a.c. conductivity was measured over frequency range 100 Hz-1MHz. It was found that? ?(?) values increase with increasing frequency according to the relation ? (?)=Aws . The values of frequency exponent (s) were found to increase with number of layers.

Study on 1/f γ Noise Characterization of Metallic Interconnection Electromigration

Metallic interconnection electromigration is a common phenomenon in integral circuit, and it influences circuit reliability seriously as rapid miniaturization of circuit size. Resistance is a traditional electromigration characterization parameter, but it requires strict testing condition, and it is not sensitive to vacancies accumulation at early stage of electromigration. Some recent researches show that noise is very sensitive to metallic thin film electromigration, it can be used as an effective inspect method for electromigration. So noise wais used to characterize damage degree of Al thin film electromigration in this paper., Tthe results showeds both noise amplitude and frequency exponent increased during electromigration process, and when void nucleation occuredhappens, frequency exponent increased sharply. noise can also reflect electromigration degree under different environment temperature. Through comparing with resistance, noise can be proved a better characterization parameter for electromigration

PHONON-INDUCED 1/F NOISE IN MOS TRANSISTORS

Existing experimental data for the temperature dependence of 1/f noise in both n- and p-channel MOS transistors are heuristically compared with either bulk or surface phonon spectra or with both of them. It is found that the noise structure mirrors different van Hove singularities in both bulk and surface phonon spectra. This is thought to be the signature of surface and bulk phonons in the 1/f noise of MOS transistor. For a Debye phonon spectrum, an intriguing 1/τ distribution is obtained. The famous connection between oxide states and 1/f noise can be understood in terms of phonon scattering if the tunneling is inelastic. Striking similarities were found in the temperature dependence of the frequency exponent in different MOS transistors and all of them feature similarities with those of the frequency exponent in silicon on sapphire. This indicates that a common structural factor is controlling the temperature variation in both systems. Starting from the observation that the noise intensity vs. temperature is the image of the phonon density of states, the temperature dependence of the frequency exponent was calculated. It is in a reasonable agreement with the experiments for both n-channel transistors and silicon on sapphire sample.