Electrical conductivity of (PbO)1−x (SnO) x

Electrical conductivity of lead tin monoxide has been measured as a function of composition (x), temperature and electric field. Heat treatment of samples in vacuum produces an irreversible increase in conductivity and is probably due to chemisorption of oxygen. The thermal activation energies in screen printed layers have been found to be lower than that in pressed pellets and is considered to be due to more grain boundaries being present in the former. The non ohmic electrical conduction in pellets followsJ ∝V ⁿ relationship wheren ranges between 2 and 1·25 for different compositions and temperatures. The theory of space charge limited currents (sclc) in defect insulators has been invoked to explain the observed results.     

Electronic conduction in La-based perovskite-type oxides

Abstract

A systematic study of La-based perovskite-type oxides from the viewpoint of their electronic conduction properties was performed. LaCo_0.5Ni_0.5O_3±δ was found to be a promising candidate as a replacement for standard metals used in oxide electrodes and wiring that are operated at temperatures up to 1173 K in air because of its high electrical conductivity and stability at high temperatures. LaCo_0.5Ni_0.5O_3±δ exhibits a high conductivity of 1.9 × 10³ S cm^?1 at room temperature (R.T.) because of a high carrier concentration n of 2.2 × 10²² cm^?3 and a small effective mass m? of 0.10 m_e. Notably, LaCo_0.5Ni_0.5O_3±δ exhibits this high electrical conductivity from R.T. to 1173 K, and little change in the oxygen content occurs under these conditions. LaCo_0.5Ni_0.5O_3±δ is the most suitable for the fabrication of oxide electrodes and wiring, though La_1?xSr_xCoO_3±δ and La_1?xSr_xMnO_3±δ also exhibit high electronic conductivity at R.T., with maximum electrical conductivities of 4.4 × 10³ S cm^?1 for La_0.5Sr_0.5CoO_3±δ and 1.5 × 10³ S cm^?1 for La_0.6Sr_0.4MnO_3±δ because oxygen release occurs in La_1?xSr_xCoO_3±δ as elevating temperature and the electrical conductivity of La_0.6Sr_0.4MnO_3±δ slightly decreases at temperatures above 400 K.     

Electronic conduction in La-based perovskite-type oxides

A systematic study of La-based perovskite-type oxides from the viewpoint of their electronic conduction properties was performed. LaCo_0.5Ni_0.5O_3±δ was found to be a promising candidate as a replacement for standard metals used in oxide electrodes and wiring that are operated at temperatures up to 1173 K in air because of its high electrical conductivity and stability at high temperatures. LaCo_0.5Ni_0.5O_3±δ exhibits a high conductivity of 1.9 × 10³ S cm⁻¹ at room temperature (R.T.) because of a high carrier concentration n of 2.2 × 10²² cm⁻³ and a small effective mass m∗ of 0.10 m_e. Notably, LaCo_0.5Ni_0.5O_3±δ exhibits this high electrical conductivity from R.T. to 1173 K, and little change in the oxygen content occurs under these conditions. LaCo_0.5Ni_0.5O_3±δ is the most suitable for the fabrication of oxide electrodes and wiring, though La_1−xSr_xCoO_3±δ and La_1−xSr_xMnO_3±δ also exhibit high electronic conductivity at R.T., with maximum electrical conductivities of 4.4 × 10³ S cm⁻¹ for La_0.5Sr_0.5CoO_3±δ and 1.5 × 10³ S cm⁻¹ for La_0.6Sr_0.4MnO_3±δ because oxygen release occurs in La_1−xSr_xCoO_3±δ as elevating temperature and the electrical conductivity of La_0.6Sr_0.4MnO_3±δ slightly decreases at temperatures above 400 K.     

Thermally stimulated current and electrical conduction in metal (1)-ethyl cellulose-metal (1)/(2) systems

Depolarization current characteristics of solution grown pure ethyl cellulose (EC) films of about 20μm thickness have been studied as a function of electrode materials at constant poling field (5 × 10⁴ V/cm) and poling temperature 40°C. Thermally stimulated current (TSC) thermograms of EC consists of two well resolved peaks (located at 60°C and 140°C) for Al-Al system, which are attributed to the deorientation of strongly attached ethoxy groups of glycosidal units and diffusion of space charges either at electrodes or due to their thermal release at higher temperatures from the defect levels. For dissimilar electrode combinations (Al-Ag/Cu/Au/Sn/Pb), an indication of peak of lower magnitude at around (50–70°C) alongwith a higher temperature peak (140–155°C), have been observed. TSC parameters are found to change with the choice of electrode material. The dependence of dark current at 40°C in metal-ethyl cellulose-metal systems on applied voltage in the range (2·0–5·0) × 10⁴V/cm has also been studied. The results of current-voltage measurement on EC have been interpreted to show that the Schottky-Richardson mechanism is the controlling transport mechanism. Zero field current density extrapolated fromI-E ^1/2 plots are found to vary with metal work function.     

Study of the conduction properties of silicon-rich oxide under illumination

Carrier transport in silicon-rich oxide (SRO) was studied under illumination using the standard current versus voltage and capacitance versus voltage measurements. Al/SRO/Si metal-oxide-semiconductor (MOS)-like structures were used, and SRO layers with different thickness and excess Si concentration were deposited by low-pressure chemical vapor deposition (CVD) technique. In reverse bias condition, two conduction regimes were observed. The photocurrent in low-voltage regime is limited by the transport mechanism of carriers; while in the high-voltage regime, it is limited by the density of photogenerated carriers. The Poole-Frenkel conduction mechanism was found to dominate the carrier transport in SRO under illumination. It was also demonstrated that high photosensitivity was achieved in this structure that is a potential visible optical sensor.     

Mixed conduction in charge transfer materials based on aromatic diamines and iodine having different mole ratios

Mixed ionic and electronic conduction in charge transfer materials based on aromatic diamine electron donors (benzidine,o-tolidine (3,3′-dimethyl benzidine) andN,N′-diphenylbenzidine) with iodine in different mole ratios has been reported. The current-voltage and capacitance-voltage curves as a function of time and temperature have been obtained to determine the role of ionic conduction in electronic conductors based on charge transfer complexes. The compositional dependence of ionic transport numbers, diffusion parameters, ionic(σ _i) and electronic(σ _e) conductivities and thermal activation energies has been studied. Temperature and frequency dependence of AC impedance and related parameters have been studied to learn about the electrical conduction behaviour in these non-stoichiometric charge transfer materials. An electrochemical mechanism has been proposed to account for the ionic conduction in some of these complexes.     

Ion conduction and redistribution at grain boundaries in oxide systems

The review provides a comprehensive overview on the major findings regarding ion redistribution at interfaces in oxide systems and its effects on the electrical transport properties. As far as interfaces are concerned, grain boundaries and hence polycrystalline materials are to the fore. Heterocontacts and hence composites are only considered if relevant for the general understanding. Selected examples refer to oxide ceramics but also to composites. As far as the fundamental properties are concerned, major emphasis is laid on the impact on ion conductivity. Purely electronic effects (e.g. interfaces in semiconductors, boundaries in superconductors, or the formation of two-dimensional electron gases at the interface between two insulators) as well as phenomena related with solid/fluid interfaces are not addressed.     

防静电塑料地板电荷衰减机理探讨

本文主要对防静电塑料地板带电后的电荷衰减机理进行了理论分析。文中导出的一些公式和结果可应用于防静电地板的改性,可供生产或使用防静电地板的单位参考。     

Further MN rule for thermally activated high field conduction in bulk samples of glassy Se100−xSbx alloys

In the present paper, we report the observation of the Meyer-Neldel rule (MNR) in thermally activated high field conduction in bulk samples of glassy Se_100−xSb_x alloys. We have investigated Meyer-Neldel rule by two different approaches.In first approach, the temperature dependence of d.c. conductivity is studied at different electric fields without changing the composition of the glassy system. In the second approach, the composition itself varies at a particular electric field.We found that the conductivity obeys the Meyer-Neldel rule as the pre-exponential factor depends on activation energy. We also found a strong correlation between pre-factor σ₀₀ and Meyer-Neldel energy in both cases. The observation of the correlation between pre-factor σ₀₀ and Meyer-Neldel energy can be described by multiple excitations stimulated by phonon energy as described by Yelon and Movaghar.     

Electrical transport mechanisms in a-Se95M5 films (M = Ga, Sb, Bi)

The temperature dependence of direct current (dc) conductivity has been reported in thin films of a-Se₉₅M₅ (where M = Ga, Sb, Bi), in the temperature range 219-375 K, in order to identify the conduction mechanism and to observe the doping effect of different metals on amorphous selenium. It is found that the conduction in high temperature range (314-375 K) is due to thermally activated tunneling of charge carriers in the band tails of localized states; and in the low temperature range (219-314 K) conduction takes place through variable range hopping in the localized states near the Fermi level. Current-voltage (I-V) measurements at high electric fields (the field dependence of dc conductivity) have also been carried out for the samples of present system. The analysis of data shows the existence of space charge limited conduction (SCLC) in these glassy alloys. The density of localized states near the Fermi level is calculated for these alloys using dc conductivity (Mott parameters) and SCLC measurements data. The properties have been found to be highly composition dependent.     

Enhanced electrical and thermal conductivity of modified poly(acrylonitrile-co-butadiene)-based nanofluid containing functional carbon black-graphene oxide

Solution refluxing and high-pressure homogenization technique were reported for synthesizing nanofluids based on modified poly(acrylonitrile-co-butadiene) (M-PANB) as base fluid and carbon black (CB)/carbon black-graphene oxide (CB-GO) as filler. The physiochemical properties were studied to analyze the structure, morphology, thermal and electrical conductivity. FTIR analysis corroborated the structure of CB-GO nanobifiller and nanocomposite. Microstructure analysis of M-PANB/CB-GO revealed good dispersion of CB-GO nanosheets, while CB series showed granular distribution. XRD studies confirmed amorphous structure of M-PANB/CB-GO nanocomposite. Thermal conductivity of nanofluid was found to increase upto 1.41 W/mK for 10 wt.% CB-GO loading and electrical conductivity was increased to 2.5 × 10^?3 Scm^?1.     

绝缘介质中载流子注入与传导的机理

本文分析了与绝缘介质老化、失效过程密切相关的载流子注入与传导机理,包括具有电极限制特性的肖特基效应、具有体限制特性的普尔-弗兰凯尔效应、隧穿效应、离子跳跃传导以及空间电荷限制电流。研究结果表明:由普尔-弗兰凯尔效应引起的势垒降低的高度是由肖特基效应降低的势垒高度的两倍。如果In(I/E2)-1/E特性关系始终是线性的,说明载流子是由隧穿效应注入介质中的。在高电场下,离子跳跃传导的J-E特性曲线是一条斜率为eλ/2kT的直线,并可由此斜率计算得到离子跳跃的距离。由空间电荷限制电流的J-V特性可以确定临界电压,即电流从陷阱限制值迅速跳高至无陷阱的空间电荷限制电流值的电压。     

Studies on electrical conduction in Bi4SrTi4O15

The ferroelectric Bi₄SrTi₄O₁₅ has been synthesized and a study of the electrical (AC) conductivity was made on both poled and unpoled samples in the frequency range from 100 Hz to 1 MHz and from room temperature to 550°C. In the case of unpoled samples the activation energy was found to be 0·54 eV and subsequent to poling it was lowered to 0·39 eV indicating an increased conductivity after poling. Further the conductivity increased with increasing frequency and temperature. DC conductivity measurements were also carried out. Dielectric measurements indicate a peak in the dielectric constant at 530°C.     

La1-xSrxCo0.2Fe0.8O3-δ阴极材料的导电机理研究

La1-xSrxCo1-yFeyO3-δ系(LSCF)钙钛矿结构复合氧化物是一类性能优异的离子-电子混合导体,同时具有良好的化学稳定性和催化活性,是很好的中低温固体氧化物燃料电池(SOFC)阴极材料的候选材料.本文测试了制备出的La1-xSrxCo0.2Fe0.8O3-δ(x=0.1～0.5)系材料电导率并探讨了它们的离子导电、电子导电的微观机制,指出除了小极化子导电机制外,还可能有以下几种机理共同作用:1)热激发引起Co3 离子的电荷歧化;2)高温下氧空位生成导致的离子补偿;3)Fe4 较Co4 优先进行电子补偿.     

Electrical conduction in 10-20 nm thick polycrystalline tin oxide thin films deposited by chemical vapor deposition

Electrical properties were studied for chemical vapor deposited fluorine doped tin oxide films that were less than 20 nm thick. The electrical properties of the coatings were found to be affected by the type of additive alcohol used in the deposition process. Conductivity was superior for ethanol or isopropyl alcohol (IPA) compared to methanol. Hall effect measurements showed that mobility and carrier concentration were best for IPA, less for ethanol, and least for methanol. Influence of carrier scattering factors to electrical properties was speculated. Potential barrier for carrier scattering at grain boundaries was estimated to be lower in an IPA-added film compared to methanol-added films. Experimental results suggested electrical properties were influenced by size and density of tin oxide micro-grains. It was concluded that interconnections between the micro-grains increased mobility and carrier concentration of very thin films.     

Dielectric properties and electrical conduction in yttrium iron garnet (YIG)

The dielectric properties (dielectric constant and loss) of a single crystal of yttrium iron garnet (Y₃Fe₅O₁₂) were measured in the temperature range 77–725 K and in the frequency range 100 Hz-1 MHz. AC conductivity was derived from dielectric constant and loss. DC conductivity was measured in the temperature range 30–725 K. Thermoelectric power (TEP) was measured from 77–800 K. On the basis of the results, conduction in this garnet is interpreted as due to small polarons. The nature of conduction at different temperature ranges is discussed in the light of existing reports on defect formation.     

Electrical conduction mechanism in solution grown doped polyvinyl pyrrolidone films

A detailed study of electrical conduction mechanism in bimetallized ferrocene-doped polyvinyl pyrrolidone films was carried out. The measurements were carried out on films of about 20 μm thick, in the field range of (2.0–8.0) x 10⁴ V/cm at temperatures ranging from 363 to 423 K. An investigation of the effect of impurity such as ferrocene in the polymer matrix was undertaken. Lowering of activation energy and increase in current due to doping were observed. The results showed that the charge carriers were generated by field-assisted lowering of coulombic barriers at the traps and were conducted through the bulk of the material by a hopping process between the localized states by a Jonscher-Ansari modified Poole-Frenkel mechanism. The dependence of current and activation energy on the ferrocene concentration is explained on the basis of charge transfer type of interaction between dopant and polymeric material.     

Electrons in Magnetic Structures with Domain Walls: Accumulation of Spin, Charge, and Transport Properties

We present the results of our theoretical analysis of magnetic, electric, and transport properties of domain walls in ferromagnets. The results were obtained within the semiclassical approximation and are valid for smooth domain walls. Taking into account Coulomb interaction between electrons, we calculated spin and charge accumulation at the wall. Local conductivity due to scattering from impurities located in the region of the domain wall was also calculated.     

Charging transient in polyvinyl formal

In the present paper charging and discharging transient currents in polyvinyl formal (PVF) were measured as a function of temperatures (40–80°C), poling fields (90 ×10³−9.0 × 10⁴ V/cm) and electrode combinations (Al-Al, Au-Al, Zn-Al, Bi-Al, Cu-Al and Ag-Al). The current-time characteristics have different values of slope lying between 0.42–0.56 and 1.42–1.63. The polarization is considered to be due to dipolar reorientation associated with structural motions and space charge relaxations due to trapping of injected charge carriers in energetically distributed traps.     

Nonuniform electric fields in pulse heated wires

The influence of nonuniform electric fields on the measurement of the electrical conductivity in pulse-heated wires is studied analytically. Two causes for nonuniformity are considered: switching-on of an external voltage source (transient skin effect) and temperature-dependent change of the electrical conductivity. This problem usually has two strictly different time scales: a short one, on which the transient skin effect takes place, and a long one, on which heat conduction happens. Here, the short time scale is considered.Paper presented at the Third Workshop on Subsecond Thermophysics, September 17–18, 1992, Graz, Austria.