Nonlinear Electrical Behavior Research Articles

Influence of Sm2O3 on electrical performance of (Nb, Si)-doped TiO2-based varistor

In this work, TiO2-based varistor ceramics doped with Nb2O5, SiO2 and Sm2O3 are prepared by using conventional solid state synthesis. X-ray diffractometry, scanning electron microscopy, energy dispersive spectrometer and direct current electrical measurement are used to study phase composition, microstructure and nonlinear properties. It is found that the second phase emerges at grain boundary, having a great influence on nonlinear electrical behaviors. Breakdown voltage E1mA initially decreases and then increases with increasing of Sm2O3 content. The minimum of breakdown voltage E1mA (9.3 V/mm) occurs at the composition of 99.0 %TiO2–0.5 %Nb2O5–0.3 %SiO2–0.2 %Sm2O3. Relative dielectric constant initially increases and then decreases. When the content of Sm2O3 increases to 0.3 %, the varistor has ultrahigh dielectric constant, which is consistent with its narrowest grain-boundary barriers. The nonlinear coefficient increases from 2.51 to 4.13 with increase of Sm2O3 from 0.0 to 0.4 %, and varistor of 98.8 %TiO2–0.5 %Nb2O5–0.3 %SiO2–0.4 %Sm2O3 owns the highest grain-boundary barriers.

Theoretical and experimental investigation of a nonlinear compressive-mode energy harvester with high power output under weak excitations

Harvesting ambient vibration energy is a promising method for realizing self-powered autonomous operation for low-power electronic devices. Most energy harvesters developed to date employ bending-beam configurations and work around the resonant points. There are two critical problems that have hindered the widespread adoption of energy harvesters: insufficient power output and narrow working bandwidth. To overcome these problems, we proposed a novel energy harvester, called a high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH). The HC-PEH delicately synthesizes the merits of the force amplification effect of the flexural motion and the dynamic properties of elastic beams, and thus is capable of high power output with wide working bandwidth. In this paper, theoretical and experimental studies were performed on the HC-PEH. Taking nonlinear stiffness, nonlinear damping, and nonlinear piezoelectricity into account, we developed an analytical model that provides comprehensive insight into the nonlinear mechanical and electrical behaviors of the system. The analytical results closely render the experimental data and demonstrate great performance enhancement. In the experiment, a maximum power output of 54.7 mW is generated at 26 Hz under an acceleration of 4.9 m s−2, which is over one order of magnitude higher than other state-of-the-art systems.

Design and fabrication of an electrode array sensor for probing the electric potential distribution at the mesoscopic scale in antistatic felts

We present an original voltage probe design for measuring the electric potential distribution at the mesoscopic scale (i.e., 1 mm–1 cm) in antistatic felts. The felts are composed of a mixture of non-conductive and metallic fibers and exhibit complex nonlinear electric behavior—including possibly nonlinearity and hysteresis effects—which may be due to localized electrical or electromechanical phenomena. The sensor consists of an array of 8 × 9 needle electrodes (ϕ 160 µm at the shaft and less than ϕ 50 µm toward the apex), which are mechanically maintained at fixed relative positions while their tips are inserted inside the fabric of the sample. The interelectrode distance is 1.5 mm and the overall active area is 12 × 12 mm2. The electrical insulation resistance for nearest neighbor pairs of electrodes was found to be larger than 860 GΩ, thus making the sensor suitable for measuring antistatic felts with an electric resistance that typically does not exceed a few GΩ. The sensor was successfully used for measuring the distribution of the electric potential in a polyester fabric subjected to voltages of up to 6.2 kV, and in a sample containing 2% in weight of metallic fibers, demonstrating the presence of irreversible changes in that felt sample (i.e., with conductive fibers) at high voltages. It is concluded that the developed probe voltage is a promising technique that could be used for the assessment of the conduction mechanisms in the antistatic materials at the mesoscopic scale.

Engineering Nonlinear Electrical Behavior with Asymmetric Multisegmented Polymer–Metal Nanowires

In this paper, we report on novel hybrid nanowires as prototypical building blocks for nanocomponents. Multisegmented hybrid nanowires (HNWs) made of metallic and conjugated polymer (CP) segments were elaborated and the impact of metal/polymer interfaces on the rectifying behavior was determined. Using HNWs integrated into micromachined devices, the relationship between electronic properties and original structure is revealed. By combining transmission electron microscopy (TEM) directly on the symmetric and asymmetric HNWs structures studied by current–voltage (I–V) spectroscopy, we show that rectifying I–V characteristics are observed only for asymmetric HNWs. Moreover, it is shown that the rectification ratio can be improved up to 3 orders of magnitude by a proper selection of the HNW composition. While the rectifying behavior is observed in HNWs after oxidative or acid doping, the charge transport mechanism in as-synthesized HNWs is bulk-limited and independent from their structure. Both symmetric and asymmetric HNWs exhibit Ohmic and nonlinear I–V curves above and below TNL ≈ 120 K, respectively. These electrical behaviors are consistent with a progressive transition from an Ohmic to a non-Ohmic variable-range-hopping (VRH) mechanism. We discuss the origin of these nonlinearities, comparing the two- and four-probe measurements on single HNWs, and we propose a simple model based on dual back-to-back Schottky diodes to explain qualitatively the rectifying properties.

A Comparative Study between the Effects of Oxidizing and Reducing Atmospheres on the Properties of ZnO-Bi<sub>2</sub>O<sub>3</sub>-Mn<sub>2</sub>O<sub>3</sub> Varistor Fabricated from Micro and Nanoparticles Size of ZnO

Zinc oxide-based varistors are semiconductor ceramics. Their excellent nonlinear electrical behaviors are induced from their grain boundaries and depend on their microstructural characteristics. From a theoretical aspect, finer primary particles with narrow size distributions provide better electrical and optical properties. Thus, these properties are related to the morphology and size of ZnO grains. In this study, ZnO-Bi2O3-Mn2O3 varistors fabricated from ZnO micro-and nanoparticle powders are prepared via conventional ceramic processing. The effects of ZnO particle size and different annealing ambients on the properties of ZnO varistors are also investigated. The strong solid-state reaction during sintering may be attributed to the high surface area of the 20 nm ZnO nanoparticles that promote strong surface reaction. The annealing process also improves grain crystallinity, as shown in the decrease in intrinsic compressive stress based on the X-ray diffraction lattice constant and full-width at half-maximum (FWHM) data. The reduced particle size significantly influences the electrical properties, showing a sharp drop in the breakdown voltage. Thus, the ZnO nanoparticles can be used to manufacture of varistors with superior properties and lower breakdown voltage compared with commercial ones.

Quasi-ideal Nonlinear Electrical Behavior of Polycrystalline SnO2 Ceramic Varistors Doped with SiO2

The influence of SiO2 doping on the microstructure and electrical behavior of SnO2 varistors has been studied. The varistor effect was studied over a wide range from 10−9 A to 104 A. It is shown that the J(E) characteristic of SnO2 ceramics exhibits a nonlinear coefficient >100. The SiO2 doping also resulted in a sharp-abrupt upturn region in the I–V characteristic, indicating a single semiconductor junction behavior. The leakage current of the varistors is rather low, on the order of 10−10 S m−1. In the upturn region of operation where the curve departs from the nonlinear relation and approaches the value of the bulk resistivity of the material, the ceramic is characterized by a current density almost independent of the applied voltage. A very small amount of SiO2 causes large perturbations of the conventional thermionic emission observed in varistor ceramic materials.

Advances in fractal germanium micro/nanoclusters induced by gold: microstructures and properties.

Germanium materials are a class of unique semiconductor materials with widespread technological applications because of their valuable semiconducting, electrical, optical, and thermoelectric power properties in the fields of macro/mesoscopic materials and micro/nanodevices. In this review, we describe the efforts toward understanding the microstructures and various properties of the fractal germanium micro/nanoclusters induced by gold prepared by high vacuum thermal evaporation techniques, highlighting contributions from our laboratory. First, we present the integer and non-integer dimensional germanium micro/nanoclusters such as nanoparticles, nanorings, and nanofractals induced by gold and annealing. In particular, the nonlinear electrical behavior of a gold/germanium bilayer film with the interesting nanofractal is discussed in detail. In addition, the third-order optical nonlinearities of the fractal germanium nanocrystals embedded in gold matrix will be summarized by using the sensitive and reliable Z-scan techniques aimed to determine the nonlinear absorption coefficient and nonlinear refractive index. Finally, we emphasize the thermoelectric power properties of the gold/germanium bilayer films. The thermoelectric power measurement is considered to be a more effective method than the conductivity for investigating superlocalization in a percolating system. This research may provide a novel insight to modulate their competent performance and promote rational design of micro/nanodevices. Once mastered, germanium thin films with a variety of fascinating micro/nanoclusters will offer vast and unforeseen opportunities in the semiconductor industry as well as in other fields of science and technology.

The nonlinear electrical behavior of ZnO-based varistor ceramics with CaSiO3 addition

ZnO-based varistor ceramics with various amounts of CaSiO3 have been prepared by the conventional solid-state reaction route, and the phase composition, microstructure and electrical properties have been investigated by XRD, SEM, a V–I source/measure unit and impedance spectroscopy (IS). The XRD analyses show the presence of primary phase ZnO and some minor secondary phases. The electrical properties analysis results show that the nonlinear coefficient of the varistor ceramics is in the range of 14.9–30.9, the breakdown voltage in the range of 57.0–168.8 V/mm, and the leakage current in the range of 1.1–31.5 μA/cm2. A schematic model for the electrical microstructure of ZnO-based varistor ceramics is proposed with an equivalent circuit of Ra (RgCg)(RgbCgb) by IS.

Motion Control of Piezoelectric Positioning Stages: Modeling, Controller Design, and Experimental Evaluation

In this paper, a general skeleton on modeling, controller design, and applications of the piezoelectric positioning stages is presented. Toward this framework, a general model is first proposed to characterize dynamic behaviors of the stage, including frequency response of the stage, voltage-charge hysteresis and nonlinear electric behavior. To illustrate the validity of the proposed general model, a dynamic backlash-like model is adopted as one of hysteresis models to describe the hysteresis effect, which is confirmed by experimental tests. Thus, the developed model provides a general frame for controller design. As an illustration to this aspect, a robust adaptive controller is developed based on a reduced dynamic model under both unknown hysteresis nonlinearities and parameter uncertainties. The proposed control law ensures the boundedness of the closed-loop signals and desired tracking precision. Finally, experimental tests with different motion trajectories are conducted to verify the proposed general model and the robust control law. Experimental results demonstrate the excellent tracking performance, which validates the feasibility and effectiveness of the proposed approach.

Effect of Co3O4 content and compaction pressure on the microstructure and electric properties of SnO2–Sb2O5–Cr2O3 varistor ceramics

Abstract The effect of Co 3 O 4 content (1 and 5 mol%) and powder compaction pressure (55, 110, and 166 MPa) on the microstructure and nonlinear electrical behavior of SnO 2 -based ceramics prepared by high-energy milling was investigated. The results show a correlation between the compaction pressure and Co 3 O 4 content with the electrical properties. At constant oxide concentration and with increase in the compaction pressure, there is a slight decrease in the breakdown electric field and an increase in the nonlinearity coefficient. Conversely, at the highest Co 3 O 4 content the breakdown electric field varies slightly, whilst the nonlinearity coefficient is maintained to be constant. A decrease in grain size with Co 3 O 4 increase is ascribed to the formation of the cobalt/tin oxide spinel (Co 2 SnO 4 ) at the grain boundaries. The best electrical characteristics were achieved with 1 mol% Co 3 O 4 and 166 MPa, that is, nonlinear coefficient of 13.24 and breakdown electric field of 830 V/cm. Based on thermal analyses, possible reactions for Co 2 SnO 4 formation are outlined.

Composite varistors based on epoxy resin/La0.8Sr0.2MnO3

Polymer/perovskite manganese oxide (epoxy resin/La0.8Sr0.2MnO3) composites are prepared using bonded method. There is no reaction between La0.8Sr0.2MnO3 and the polymer. The nonlinear current–voltage property is significantly affected by the content of polymer. The resistivity and nonlinear coefficient increase with the increase of polymer content. The resistivity of the composites is 5–9 orders of magnitude higher than that of the sintering ceramics. The nonlinear electrical behavior is an intrinsic property. Compared with conventional sintered ceramic varistors, the polymer/manganese oxide composite varistors have greater nonlinear coefficient above 45.

Effect of V2O5 on electrical and microstructural properties of ZnOceramics

ZnO ceramics with small amounts of V2O5 as a varistor-former ranging from 1–5mol% were prepared by conventional powder processing route and sintered at 700, 800 and 900°C for 2h. It was observed that the grain growth behavior in ZnO ceramics was strongly influenced by doping with V2O5. Morever, lower temperatures about 900°C could be used for sintering. The microstructure of the samples consists of ZnO grains as a main phase and Zn3(VO4)2 as a secondary phase. All of the prepared ceramics showed characteristic of non-ohmic current–voltage behavior. Non-linear coefficient increased with increase in V2O5 content and sintering temperature. Activation energy of the ceramics lies in the range of 0.071–0.402eV which decreased with increase in V2O5 content and sintering temperature. The origin of the non-linear electrical behavior was explained by considering the solid state reactions and formation of the potential barriers at grain boundaries.

Giant dielectric permittivity and non-linear electrical behavior in CaCu 3 Ti 4 O 12 varistors from the molten-salt synthesized powder

Abstract CaCu 3 Ti 4 O 12 (CCTO) powder has been prepared by a molten salt method using the NaCl–KCl mixture. Crystal structure and microstructure of the powder and the resulting ceramics have been characterized by using X-ray diffraction (XRD) and scanning electron microcopy (SEM). Impedance analyzer and current–voltage meter were employed to analyze dielectric and nonlinear ( I – V ) properties of the CCTO ceramics with different sintering durations and subsequent cooling rates. The values of dielectric permittivity and nonlinear coefficient of the quenched sample were found to be higher than those of the slowly cooled sample. More specifically, the cooling methods (quenching and furnace-cooling) have allowed to adjust; (і) the breakdown voltage within a rather low range of 0.3–4.4 kV cm −1 ; (іі) the nonlinear coefficient between 2 and 6 and (ііі) the giant dielectric permittivity for the ceramics within a range from 5000 to 20000. A double Schottky barrier can be evidenced from the linear behavior between the ln J and E 1/2 in grain boundary regions. The relationship between the electrical current density and the applied electrical field indicates that the potential barrier height Φ B is holding time dependent.

Preparation and Breakdown Property of Aluminum Oxide Thin Films Deposited onto Anodized Aluminum Substrate

Aluminum oxide thin films prepared from wet chemistry were deposited onto anodized aluminum substrates, where aluminum iso-propylate was used as the precursor to prepare the aluminum oxide films. Barrier-type anodized aluminum oxide film with different thickness was deposited in an aqueous solution of ammonium pentaborate under selected anodizing voltages. The electro-transport characteristics (I–V) are used to identify their dielectric behaviors. The FESEM micrographs and metallographic photographs were used to analyze the physical variation after the breakdown. The nonlinear electrical transport behavior and the breakdown phenomenon of the aluminum oxide thin films are studied.

Dielectric and varistor properties of rare-earth-doped ZnO and CaCu3Ti4O12 composite ceramics

To investigate the multi-functional ceramics with both high permittivity and large nonlinear coefficient, we have prepared rare-earth Tb -and- Co doped ZnO and TiO 2-rich CaCu3Ti4O12 (TCCTO) powders by chemical co-precipitation and sol–gel methods respectively, and then obtained the TCCTO/ ZnO composite ceramics, sintered at 1100°C for 3 h in air. Analyzing the composite ceramics of the microstructure and phase composition indicated that the composite ceramics were composed of the main phases of ZnO and CaCu3Ti4O12 (CCTO). Our results revealed that the TCCTO/ ZnO composite ceramics showed both high dielectric and good nonlinear electrical behaviors. The composite ceramic of TCCTO: ZnO = 0.3 exhibited a high dielectric constant of ~210(1 kHz) with a nonlinear coefficient of ~11. The dielectric behavior of TCCTO/ ZnO composite could be explained by the mixture rule. With the high dielectric permittivity and tunable varistor behaviors, the composite ceramics has a potential application for the higher voltage transportation devices.

Effects of Y<sub>2</sub>O<sub>3</sub> and In<sub>2</sub>O<sub>3</sub> on the Electrical Properties of SnO<sub>2</sub>-Based Varistors

The effects of Y2O3 and In2O3 on the microstructure and electrical properties of SnO2-based varistors were investigated. It was observed that the grain size of the samples decreased with doping Y2O3 and In2O3 and accordingly, the breakdown electrical field EB increased greatly. The measurements of barrier height and grain size reveal that the variation of grain size was not the only reason for the change of electrical properties of the sample doped with In2O3 and, the improvement of nonlinear coefficient α may mainly attribute to the increase of barrier height. Some energy levels of different state defects on the grain boundary were obtained and the energy about 0.15 eV detected here of all the samples may be attributed to the activation of . The different effects of doping Y2O3 and In2O3 indicate that In2O3 is more effective to improve nonlinear electrical behavior and breakdown electrical field of SnO2-based varistors.

Non-linear optical, electrical and magnetic behavior of manganese (II) malonate dihydrate single crystals

Single crystals of manganese malonate dihydrate have been grown by the controlled diffusion of ionic species in hydrosilica gel. The crystals are found to be antiferromagnetic and optically nonlinear. X-ray diffraction studies on single crystals showed that the compound crystallizes in the orthorhombic system with a non centrosymmetric space group Pca21. The unit cell parameters are a=8.309Å, b=9.590Å, c=7.327Å. The UV–vis spectrum indicates good transparency in the visible region. The optical band gap of the material was estimated using diffuse reflectance spectroscopy (DRS). The second harmonic generation (SHG) efficiency of the material, evaluated using Kurtz and Perry powder test, is comparable with that of standard KDP crystals. Electrical and dielectric properties of the material were investigated over wide frequency and temperature range. The optical nonlinearity and SHG efficiency are attributed to the molecular acentricity and intermolecular hydrogen bonding. Distinctive structural features inclusive of acentric space group, intermolecular hydrogen bonding and bridging through anti–syn and anti–anti malonate groups are accountable for the antiferromagnetism exhibited by the material.

Grain size effect on the giant dielectric and nonlinear electrical behaviors of Bi1/2Na1/2Cu3Ti4O12 ceramics

Single phase Bi1/2Na1/2Cu3Ti4O12 (BNCTO) ceramics with different grain sizes (1.4–4.3 μm) are prepared by a modified Pechini method to investigate their giant dielectric and nonlinear electrical behaviors. The results show that the giant dielectric and nonlinear electrical behaviors are strongly dependent on grain size. With the increment of grain size, the dielectric constant increases monotonically from 14110 (for 1.4 μm sample) to 36183 (for 4.3 μm sample) at 1 kHz, in accompaniment with the breakdown voltage reducing from 112.5 to 43.2 V/mm and the nonlinear coefficient reducing from 4.9 to 3.4. On the basis of the internal barrier layer capacitor (IBLC) model and the IBLC model of Schottky-type potential barrier, an interpretation of the grain size effect on the giant dielectric and nonlinear electrical behaviors is presented.

Giant dielectric and low voltage varistor behaviors of Ba-doped Bi1/2Na1/2Cu3Ti4O12 ceramics

Bi1/2−xNa1/2−xBa2xCu3Ti4O12 (x = 0, 0.025, 0.05, 0.075) polycrystalline ceramics are prepared by a modified Pechini method. Effect of Ba doping on the dielectric and nonlinear electrical behaviors are investigated in detail. All the samples exhibit giant dielectric effect and nonlinear electrical behavior. Compared with Bi1/2Na1/2Cu3Ti4O12 ceramics, the permittivity drops down and the nonlinear electrical behavior shifts to low voltage area by Ba doping. The permittivity reduces from 20,004 to 7,006 at 1 kHz. The breakdown voltage and nonlinear coefficient values decrease to 10.8 V/mm and 1.5, respectively. Additionally, the electrostatic barrier height drops down to 0.66 eV. Giant dielectric response and nonlinear electrical behavior can be interpreted in terms of internal barrier layer capacitors model. These results imply that Ba substitution can adjust the dielectric and nonlinear electrical behaviors of Bi1/2Na1/2Cu3Ti4O12 ceramics, which is a promising candidate for low voltage varistor materials.

Magnetoresistance, electroresistance and nonlinear electrical behavior in nanopolycrystalline La2/3Sr1/3MnO3

Nanopolycrtstalline La2/3Sr1/3MnO3 ceramics were prepared using nanosized precursor powders. Highly nonlinear current–voltage characteristics were observed at room temperature and low temperature. The nonlinearity coefficient is in the range of 1.15–53.5. The electroresistance (ER) and magnetoresistance (MR) effects have been investigated. The magnetoresistance of all the samples shows strong dependence on sintering temperature. Magnetoresistance decreases with increasing temperature.