Temperature Dependence of Electrical Condutivity in Polycrystalline Tin Oxide

The electrical conductivity of polycrystalline SnO₂ in air was measured between 400° and 1400°C using samples prepared by hot isostatic pressing and normal sintering. The apparent activation energy for conduction above 800°C was 1.3 to 1.4 eV in the hot isostatically pressed sample and 1.9 to 2.0 eV in the normally sintered sample. This difference can be interpreted as a result of the pore contributing an additional blocking effect to conduction. Also we found that the electrical conductivity above 1150°C bent down slightly from the linear regime when using a cumulative slope model.     

Temperature Dependence of Anelastic Deformation in Polycrystalline Silicon Nitride

The influence of grain-boundary sliding on the evaluation of the apparent Young's modulus and plastic-deformation (flow) stress was investigated by bending tests for two types of silicon nitrides sintered with Y₂O₃-based additives The apparent Young's moduli measured at high temperatures are consistent with those predicated from a theory based on polycrystalline anelasticity due to grain-boundary sliding. The temperature dependence of the critical bending stress for the onset of plastic deformation shows viscoplastic properties of the interglanular glass. The ductile-to-brittle transition of fracture is discussed by the bending strengths normalized by the measured Young's modulus.     

Dependence of Electrical Conductivity of ZnO on Degree of Sintering

The electrical resistivity of ZnO doped with Al₂O₃ was measured in air and under reduced pressure (∼0.5 mm Hg) in the range from 30° to 680°C as a function of the degree of sintering. The data obtained were explained in terms of the effects of the microstructure of the sintered body and the chemisorbed oxygen. There are two mechanisms of electrical conduction involved, only one of which is affected by the microstructure.     

Effect of Porosity on the Electrical Properties of Polycrystalline Sodium Niobate: I, Electrical Conductivity

The electrical behavior of NaNbO₃ ceramic samples with different relative densities was investigated by ac impedance spectroscopy in a range of 13 MHz to 10⁻³ Hz between 400° and 800°C in dry air. Measurements were performed during heating and cooling cycles. The Nyquist impedance diagrams of dense sodium niobate exhibit only one semicircle representing the grain contribution with depression angles as small as 1°, indicating a high homogeneity of the specific electrical properties. In the case of porous samples, the data reveal an additional low-frequency semicircle related to microstructure. For all studied samples, the Arrhenius conductivity plots show a change in the activation energy around 640°C, attributed to the tetragonal-cubic phase transition. The electrical conductivity of porous samples appears to be higher than that of dense ones.     

Particle Size Dependence of the Electrical Conductivity of NaCl

The ac and dc conductivities of single-crystal and polycrystalline NaCl were measured as a function of both temperature and particle size. The ac conductivity results for single-crystal NaCl agreed well with the literature: intrinsic activation energy = 1.86 ev; extrinsic, impurity-controlled range = 0.74 ev; extrinsic, association range = 1.16 ev; and the intrinsic-extrinsic knee in the curve was at 10³/ T ∼ 1.4°K⁻¹ and σ₀∼ 6 × 10⁻⁸ ohm⁻¹ cm⁻¹. In the intrinsic range, however, the total conductivity (σ₀) was the sum of two ionic contributions: a steady state, nonblocked contribution (σ_θ and a blocked contribution (σ₀—σ_θ). The activation energy for the dc steady state conductivity was 1.6 ev. When the extrinsic, impurity-controlled contribution to the total conductivity was made insignificant by anion doping, the same 1.6 ev was the activation energy for the intrinsic ac conductivity at low temperatures. The data for the polycrystalline samples showed that ac conductivity increased inversely with particle size and dc steady state conductivity increased only slightly, if any, with decreasing particle size. It is postulated that the steady state conductivity is the result of the nonblocked ionic transport of sodium ions and that the ac portion of the total conductivity is due to the movement of chlorine ions which are blocked, giving rise to the polarization phenomenon. The increase in the ac conductivity with decreasing particle size is correlated with the enhanced movement of Cl⁻ in the subgrain boundary region, as has been previously shown by diffusion measurements.     

Thermal Conductivity: XII, Temperature Dependence of Conductivity for Single-Phase Ceramics

Theoretical relationships and experimental data concerning thermal conductivity for a number of oxide materials have been compared over a wide temperature range. Deviations from the basic proportionality between k and 1/ T are caused by radiant-energy transmission, a high Debye temperature, a low mean free path of the thermoelastic waves, porosity, and in a few cases electronic conductivity. Extrapolation of thermal conductivity data to high temperatures is not reliable.     

Microstructural Morphology and Electrical Properties of Copper- and Niobium-Doped Tin Dioxide Polycrystalline Varistors

The influence of a Nb₂O₅ additive on the densification, microstructural morphology, and nonlinear electrical properties of the CuO-doped SnO₂-based varistors was investigated. It was found that copper oxide significantly improves the densification of the SnO₂ ceramics. The effects of Nb₂O₅ on tin dioxide varistors were analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and capacitance–voltage measurements, as well as impedance spectroscopy. Copper oxide segregates at the grain boundaries and precipitates at triple points, and niobium makes the tin dioxide grain semi-conductive. The copper oxide intergranular insulating layer separates two semi-conductive tin dioxide grains and forms the barriers. The reason for the nonlinearity of SnO₂-based ceramics was explained.     

Composition and Conductivity of Tin Oxide Films Prepared by Pyrohydrolytic Decomposition of Tin(IV) Compounds

The conductivity of thin poly crystalline Sn oxide films prepared by spraying solutions of Sn(IV) compounds onto glass or quartz substrates was studied. Conductivity was decreased by increasing the temperature or prolonging the time of heating after hydrolysis, by substituting SnBr₄ for SnCl₄, and by substituting O₂ for N₂ during spraying. These effects are explained in terms of nonstoichiometry of the sample and the presence of residual halogens in the crystal lattice as detected by ion-probe analysis.     

Temperature Dependence of the Resistivity for Metal-Oxide Semiconductors Based on Tin Dioxide

Polycrystalline films of SnO₂ and films in the SnO₂–In₂O₃ and SnO₂–ZnO systems, which are of interest for use in gas-sensitive sensors, are grown from metal chlorides on a 22-XC ceramic substrate by the hydropyrolytic method. The dependences of the resistivity for metal oxide films based on tin dioxide are measured in the temperature range 200–400°C. The distribution of phases in the samples prepared is examined using electron probe X-ray microanalysis. It is shown that the specific features in the temperature dependences of the resistivity for the semiconducting metal-oxide films grown can be associated with their microstructure and the environmental condition. The temperature dependences of the resistivity for all the metal-oxide films studied exhibit a semiconductive behavior.     

丁腈橡胶导电性与温度特性的研究

对乙炔炭黑填充丁腈橡胶（ＮＢＲ）的导电性及其与温度的关系进行了研究,分析了丁腈橡胶的电阻率与乙炔炭黑（简称：ＣＢ）填充量的关系,并对环境温度变化时电阻率的变化规律提出了相应的关系式,同时对导电丁腈橡胶的通电时间与表面温度的关系进行了研究与测定。     

Effect of Metal Oxide Additions on the High-Temperature Electrical Conductivity of Alumina

Several metal oxide additions were made to typical 99 and 96% alumina compositions to study their effect on the electrical conductivity of alumina from 500° to 1400°C. The metal oxide additions investigated were CO₂O₃, Cr₂O₃, CuO, Fe₂O₃, MnO₂, NiO, and TiO₂. Using a guarded two-probe technique, dc resistivities were measured on nonporous ceramic specimens. Additions of 0.5 to 2 mole % Co₂O₃, 2 mole % CuO, 1 mole % Fe₂O₃, or 2 mole % NiO to either a 96 or a 99% alumina composition increased the electrical resistivity. The addition of 1 mole % Cr₂O₃ to either a 96 or a 99% alumina showed practically no change in the resistivity. All changes in resistivity seemed to be structure dependent.     

Effect of Copper Additive on the Microstructure and Electrical Properties of Polycrystalline Zinc Oxide

Nonohmic behavior is obtained for polycrystalline ZnO with copper as the only additive in the range 0.3 x 1 wt%. The effect of copper on the microstructure and electrical behavior of ZnO:Cu ceramics is investigated. The leakage current decreases and the breakdown electric field increases as the copper concentration increases. The large apparent dielectric constant of ZnO:Cu ceramic ( k > > k _ZnO, k _ZnO is the dielectric constant of pure ZnO) is attributed to the grain boundary barrier layer effect. A Schottky barrier height of 0.27–0.46 eV is obtained for various copper-added samples, depending on sintering temperatures.     

纳米氧化锡在丙烯酸乳液中的吸水性与电性能研究

叙述了丙烯酸乳液涂层中不同含量的纳米氧化锡与普通氧化锡和聚乙烯塑料薄膜之间的吸水性和表面电性能关系,说明在丙烯酸乳液中加入同样含量的氧化锡时,纳米氧化锡和普通氧化锡在PE薄膜表面呈现出的表面电性能和吸水性能有不同的情况和变化规律,由此说明,同种材质的纳米材料与普通材料会有不同的基本物理性能。