Nonlinear Electrical Properties Research Articles

Nonlinear electrical properties and collective transport of strongly correlated carriers in (YbS)1.25CrS2

Abstract This paper presents the nonlinear conduction with a negative differential resistance (NDR) and switching and hysteresis phenomena found in the mixed-valence misfit-layer compound (YbS)1.25CrS2. Nonlinear I–V characteristics are measured at various temperatures. They are accompanied with large voltage fluctuations near the threshold field for the onset of nonlinear conductivity. Switching or abrupt discontinuities in the I–V characteristics may arise from transitions between low and high conductivity states. The transport properties involving hysteretic switching are quite similar to those of charge density waves (CDWs) in NbSe3 and K0.30MoO3 and spin density waves (SDWs) in (TMTSF)2 X (X=PF6, NO3 and ClO4). The upper critical field for hysteretic switching is higher by two or three orders than the threshold fields for the onset of the nonlinear conduction of the latter compounds, although it is comparable to the critical field for drastic delayed switching found in K0.30MoO3 at very low temperatures. Our experimental results strongly suggest that these nonlinear phenomena are associated with the collective nature of charge dynamics for strongly correlated carriers.

소결온도가 ZPCCL계 바리스터의 충격전류 스트레스 특성에 미치는 영향

The nonlinear electrical properties and aging characteristics against surge stress of ZPCCL-based varistors were investigated for different sintering temperatures of the range <TEX>$1240-1300^{\circ}C$</TEX>. As the sintering temperature increased, the varistor voltage decreased from 732.2 to 53.8 V/mm, the nonlinear exponent decreased from 58.5 to 4.1, and the leakage current increased from <TEX>$0.38{\mu}A$</TEX> to <TEX>$46.5{\mu}A$</TEX>. The varistors sintered at <TEX>$1250^{\circ}C$</TEX> and <TEX>$1260^{\circ}C$</TEX> exhibited the high stability against multiple surge, <TEX>$150A/cm^2(8{\times}20{\mu}s)$</TEX>. On the whole, the variation rate of electrical characteristics against impulse current stress was gradually increased in order of varistor voltage<TEX>$\rightarrow$</TEX>nonlinear exponent<TEX>$\rightarrow$</TEX>dissipation facto<TEX>$\rightarrow$</TEX>leakage current.

Effect of cooling rate on electrical properties, impulse surge and dc-accelerated aging behaviors of ZPCCD-based varistors

The effect of cooling rate on nonlinear electrical properties, and stability against impulse surge and dc-accelerated aging stress of ZPCCD-based varistors was investigated. The cooling rate relatively slightly affects the microstructure, whereas it did not significantly modify the densification process. The nonlinear coefficient increased with the increase of cooling rate up to 240 °C/h, whereas the further fast cooling rate caused it to decrease. The samples cooled at 240 °C/h exhibited the highest nonlinearity, in which the nonlinear coefficient is 61.6 and the leakage current density is 6.8 μA/cm2. The aging was not significantly affected by the specified impulse surge stress, whereas it was greatly affected by dc-accelerated aging stress. The samples cooled at 120 °C/h exhibited the highest stability, in which the variation rate of breakdown field is −5.5% and the variation rate of nonlinear coefficient is −29.1% under continuous stress composed of the specified impulse surge and dc-accelerated aging stress of 0.95 E B/150 °C/24 h.

Grain boundary behavior in varistor-capacitor TiO2-rich CaCu3Ti4O12 ceramics

We prepared TiO2-rich CaCu3Ti4O12 (CCTO) ceramics by a solid-state sintering process and observed large nonlinear electrical and high dielectric behaviors. Microstructure and phase composition analyses show that CCTO grain-amorphous/TiO2 nanograin boundary-CCTO grain junction structures exist in these TiO2-rich CCTO ceramics, which leads to the nonlinear electrical and high dielectric properties. The temperature dependence of impedance spectroscopy and relationships between electrical current density versus applied electrical field indicate that the activation energy of the grain boundary for the TiO2-rich CCTO ceramics is almost the same as the potential barrier height and both of them are weakly independent of the doped concentration of TiO2, which supports the internal barrier layer capacitor model of Schottky barriers at the grain boundaries between semiconducting CCTO grains.

Dielectric and nonlinear electrical behaviors observed in Mn-doped CaCu3Ti4O12 ceramic

We present a remarkable effect of Mn doping on the dielectric and nonlinear electric properties of CaCu3Ti4O12 ceramics. The results indicate that only 2.5at.% Mn doping can suppress the dielectric permitivity in CaCu3Ti4O12 by up to two orders of magnitude (from 104 to 102), and the nonlinear varistor characteristics disappear completely, which should be mainly ascribed to the decrease of potential barrier height at the grain boundary and charge compensation for the conduction electrons caused by the Mn doping.

Electrical barriers formation at the grain boundaries of Co-doped SnO 2 varistor ceramics

The nonlinear electrical properties of CoO-doped SnO 2 ceramics were characterized. A second phase is observed at the surface of the microstructure of the specimens. Energy-dispersive X-ray analysis reveals that the second phase is composed of tin, cobalt and oxygen with an approximate atomic ratio estimated for Co and Sn: 2:1. The phase was identified by X-ray diffraction and unambiguously establish the identity of the phase: Co 2SnO 4. Electrical characterization of the binary CoO–SnO 2 was carried out on a very large range of current from 10 −9 up to 100 A cm −2 showing that the doping of CoO increases drastically the resistivity of the ceramic from 10 4 to 10 10 Ω cm. This value appears to be a threshold for which the nonlinear effect appears.

Effect of Ta 2O 5 in (Ca, Si, Ta)-doped TiO 2 ceramic varistors

TiO 2 varistors doped with 0.2 mol% Ca, 0.4 mol% Si and different concentrations of Ta were obtained by ceramic sintering processing at 1350 °C. The effect of Ta on the microstructures, nonlinear electrical behavior and dielectric properties of the (Ca, Si, Ta)-doped TiO 2 ceramics were investigated. The ceramics have nonlinear coefficients of α = 3.0–5.0 and ultrahigh relative dielectric constants which is up to 10 4. Experimental evidence shows that small quantities of Ta 2O 5 improve the nonlinear properties of the samples significantly. It was found that an optimal doping composition of 0.8 mol% Ta 2O 5 leads to a low breakdown voltage of 14.7 V/mm, a high nonlinear constant of 4.8 and an ultrahigh electrical permittivity of 5.0 × 10 4 and tg δ = 0.66 (measured at 1 kHz), which is consistent with the highest and narrowest grain boundary barriers of the ceramics. In view of these electrical characteristics, the TiO 2–0.8 mol% Ta 2O 5 ceramic is a viable candidate for capacitor–varistor functional devices. The characteristics of the ceramics can be explained by the effect and the maximum of the substitution of Ta 5+ for Ti 4+.

Modeling of the Degradation Electromigrational Processes in Structures with Intercrystallite Potential Barriers

The electromigration degradation model of nonlinear electrical properties of non‐uniform structures with intercrystallite potential barriers is developed. It allows connecting the increasing of near surfaces concentration of volume donors by their migration in electrical field at heating up structures by means of electrical current in the process of degradation. It results in experimentally observed deterioration varistoral properties, deterioration and asymmetrical deformation of currentvoltage characteristics during their exploitation.

Nonlinear current–voltage properties and accelerated aging behavior of ZPCCL-based varistors with sintering temperature

The nonlinear electrical properties and accelerated aging behavior of the varistors, which are composed of ZnO–Pr 6O 11–CoO–Cr 2O 3–La 2O 3 (ZPCCL)-based ceramics, were investigated for different sintering temperatures. The increase of sintering temperature led to more densified ceramics, whereas it decreased the nonlinear properties and varistor voltage. The highest nonlinearity of varistors was obtained from sintering temperature of 1240 °C, in which the nonlinear coefficient is 79.4 and the leakage current is 0.3 μA. However, the highest stability of varistors was obtained from sintering temperature of 1260 °C, in which the %Δ V 1 mA is + 1.9%, the %Δ α is − 10.6%, and the %Δ I L is + 20% for stress state of 95 V 1 mA/150 °C/24 h.

Optical and nonlinear electrical properties of SnO 2–polyaniline nanocomposites

Nanostructured tin dioxide (SnO 2) is synthesized in the form of colloidal sol. Aniline monomer is polymerized in colloidal sol of SnO 2 to prepare inorganic–organic hybrid nanocomposites. Optical band gap increases from 3.74 eV to 4.23 eV with increase of polyaniline concentration. The observed nonlinear current–voltage characteristics are satisfactorily explained using the Schottky type barriers. The temperature dependence of conductivity reveals three dimensional Mott's hopping process.

Calculation of the Microscopic and Macroscopic Linear and Nonlinear Optical Properties of Liquid Acetonitrile. II. Local Fields and Linear and Nonlinear Susceptibilities in Quadrupolar Approximation

A discrete model based on the multipolar expansion including terms up to hexadecapoles was employed to describe the electrostatic interactions in liquid acetonitrile. Liquid structures obtained form molecular dynamics simulations with different classical, nonpolarizable potentials were used to analyze the electrostatic interactions. The computed average local field was employed for the determination of the environmental effects on the linear and nonlinear electrical molecular properties. Dipole-dipole interactions yield the dominant contribution to the local field, whereas higher multipolar contributions are small but not negligible. Using the effective in-phase properties, macroscopic linear and nonlinear susceptibilities of the liquid were computed. Depending on the partial charges describing the Coulomb interactions of the force field employed, either the linear properties (refractive index and dielectric constant) were reproduced in good agreement with experiment or the nonlinear properties [third-harmonic generation (THG) and electric field induced second-harmonic (EFISH) generation] and the bulk density but never both sets of properties together. It is concluded that the partial charges of the force fields investigated are not suitable for reliable dielectric properties. New methods are probably necessary for the determination of partial charges, which should take into account the collective and long-range nature of electrostatic interactions more precisely.

Grain Size Effects of SnO&lt;sub&gt;2&lt;/sub&gt; Varistor Induced by Doping Pr

The effects of Pr on the microstructure and nonlinear electrical properties of the (Co,Ta)-doped SnO2 varistors were investigated. It was found by characterizing the samples sintered at 1350 oC that the breakdown voltage increases significantly from 500v/mm to 1200v/mm, and the relative permittivity decreased rapidly from 2525 to 1199 with increasing Pr6O11 concentration from 0 to 1.20 mol%. The analysis of samples’ microscopic structure showed that the grain size of SnO2 rapidly decreases from 5.1 to 3.7 µm with increasing Pr6O11 concentration from 0 to 1.20mol% .The significant decrease of SnO2 grain size is the main reason for raising breakdown voltage and reducing permittivity.

Nonlinear Electrical Properties of (Sc, Ta) Doped TiO&lt;sub&gt;2&lt;/sub&gt; Varistor Ceramics

The nonlinear electrical properties of TiO2-based varistor doped with 0.25mol% Ta2O5 and different contents of Sc2O3 were investigated. It was found that the TiO2 varistor ceramic doped with 0.10mol% Sc2O3 exhibited an optimal nonlinear coefficient of 7.8, a breakdown electrical field of 16.0V/mm, and relative dielectric constant of 1.27 × 105 (measured at 1 kHz). In order to analyze the effect of Sc2O3 on TiO2 varistors, studies were made on the capacitance versus voltage characteristics. A Schottky-type barrier, which is assumed as the origin of varistor behavior, was inferred from the C-V measurement. The barrier height and donor concentration were obtained as 0.41eV and 1.21 × 1026cm-3, respectively, for sample doped with 0.10mol% Sc2O3. Analogized to the ZnO varistors, the formation mechanism of Schottky-type barrier was discussed in this paper by the theory of defect in crystal lattice.

(Pr, Co, Cr, La)-doped ZnO 바리스터의 전기적 특성에 미치는 소결온도효과

The microstructure, electrical properties, and its stability of (Pr, Co, Cr, La)-doped ZnO varistors were investigated at different sintering temperatures in the range of <TEX>$1230{\sim}1300^{\circ}C$</TEX>. As the sintering temperature increased, the sintered density increased from 5.50 to <TEX>$5.77g/cm^3$</TEX>, the varistor voltage decreased from 777.9 to 108.0 V/mm, the nonlinear coefficient decreased from 77.0 to 7.1, and the leakage current increased from <TEX>$0.4{\mu}A\;to\;50.6{\mu}A$</TEX>. On the other hand, the donor concentration increased from <TEX>$0.90{\times}10^{18}\;to\;2.59{\times}10^{18}/cm^3$</TEX> and the barrier height decreased from 1.89 to 0.69 eV with increasing temperature. The stability of nonlinear electrical properties was obtained from sintering temperature of <TEX>$1260^{\circ}C$</TEX>. The varistors sintered at <TEX>$1260^{\circ}C$</TEX> marked the high electrical stability, with <TEX>$%{\Delta}V_{1mA}=+1.9%,\;%{\Delta}a=10.6%,\;and\;%{\Delta}I_L=+20%$</TEX> for DC accelerated aging stress state of <TEX>$0.95V_{1mA}/150^{\circ}C/24h$</TEX>.

Identification of nonlinear models of biological membranes using the voltage-clamp method

The method for identification of nonlinear systems proposed in 1952 by Hodgkin and Huxley is mathematically justified. A procedure for the application of this method is developed, including the development of the structure of a mathematical model, carrying out a series of tests with special chosen signals, and determination of unknown parameters. Basic requirements for the admissible sets of input and output signals and to the system operator have been determined. It is shown that this operator should be totally continuous and that the minimum number of unknown parameters and the minimum complexity of the operator structure should give an approximation of the necessary quality. The pros and cons of the Hodgkin-Huxley and Noble mathematical models and the methods used for their development are discussed. A structure for the operator for the identification of mathematical models of excitable membranes with a large number of membrane currents is proposed. It is found that the nonlinear electrical properties of biological membranes can be identified using tests with other types of “clamped” parameters, such as the current, ramp voltage, etc.

The effect of sintering temperature on electrical properties and accelerated aging behavior of PCCL-doped ZnO varistors

The nonlinear electrical properties and DC accelerated aging behavior of the varistors, which are composed of Pr–Co–Cr–La (PCCL)-doped ZnO ceramics, were investigated for various sintering temperatures. The increase of sintering temperature led to more densified ceramics, whereas it decreased the nonlinear properties and varistor voltage. The highest nonlinearity was obtained from 1240 °C, with 79.4 in nonlinear coefficient and 0.3 μA in leakage current. As the sintering temperature increased, the donor density increased in the range of 0.96 × 10 18–2.59 × 10 18 cm −3, whereas the barrier height at grain boundaries decreased in the range of 1.90–0.67 eV. The highest stability of varistors was obtained from sintering temperature of 1260 °C, in which the %Δ V 1mA is +1.9%, the %Δ α is −10.6% and the %Δ I L is +20% for stress state of 95 V 1mA/150 °C/24 h. It is assumed that the moderate sintering temperature improves the stability, together with high nonlinear properties.

The study on electrical behavior of Gd 2O 3–WO 3 complex ceramics at high temperature

Gd 2O 3–WO 3 complex ceramics are fabricated by the conventional solid-state reaction process. The electrical characteristics and dielectric properties of the samples were measured at various ambient temperatures in a low electric field ( E < 150 V/mm). As the temperature increases, the dielectric constant and the loss tangent show an obvious change at about 50 °C and 330 °C. When the temperature is above 200 °C, the samples display stable nonlinear electrical properties characterized by semiconductivity, and the nonlinearity increases along with increasing temperature. XRD analysis reveals that Gd 2W 2O 9 is the main phase and Gd 2O 3 is the secondary phase. Based on the phase transition of tungsten trioxide, these electrical properties of Gd 2O 3–WO 3 complex ceramics can be simply explained.

Nonlinear electrical properties of three-terminal junctions

The authors report on room-temperature electrical measurements of three-terminal junctions made from a semiconductor heterostructure. The correlation between the junction size of the devices and the voltages needed to be applied in order to observe the electrical characteristics of three-terminal ballistic junctions is studied. The authors show that the ballistic behavior of electron transport can be observed in a three-terminal junction with a junction size of a few micrometers, much larger than the mean free path of electrons in the material. The results are explained in terms of a bias-induced enhancement of the electron mean free path in the system.

Influence of CoO on stability of nonlinear electrical properties and dielectric characteristics in Pr 6O 11-based ZnO varistor ceramics

The nonlinear electrical properties, dielectric characteristics, and stability of the varistor ceramics of Zn–Pr–Co–Cr–Dy oxide system were investigated at various CoO contents. The sintered density of varistor ceramics increased from 5.25 to 5.55 g cm −3 with increasing CoO contents. The varistor voltage decreased from 235.3 to 86.0 V mm −1 with increasing CoO contents. As the CoO content increased, the nonlinear exponent increased up to 1.0 mol.% CoO, whereas further incorporation decreased the nonlinear exponent. Varistor ceramics containing 1.0 mol.% CoO exhibited the highest nonlinearity, in which the nonlinear exponent was 66.6 and the leakage current was 1.2 μA. Furthermore, varistor ceramics containing 1.0 mol.% CoO exhibited the highest stability, where the variation rate of varistor voltage, nonlinear exponent, and leakage current were −1.9%, −10.9%, and +275%, respectively, under DC accelerated aging stress of 0.95 V 1 mA /150 °C/24 h.

Effect of sintering temperature on nonlinear electrical properties and stability against DC accelerated aging stress of (CoO, Cr 2O 3, La 2O 3)-doped ZnO–Pr 6O 11-based varistors

The microstructure, V– I properties and its stability against DC accelerated aging stress of varistors, which are composed of (CoO, Cr 2O 3, La 2O 3)-doped ZnO–Pr 6O 11-based ceramics, were investigated for different sintering temperatures. The increase of sintering temperature led to more densified ceramics, whereas it decreased the nonlinear properties and varistor voltage. The highest nonlinearity was obtained from the varistors sintered at 1230 °C, with 77.9 in nonlinear exponent and 0.4 μA in leakage current. The varistors sintered at 1260 °C exhibited the highest stability, with %Δ V 1 mA of + 1.9%, %Δ α of − 10.6%, and %Δ I L of + 20%. As a result, the nonlinear properties and stability of ZnO–Pr 6O 11-based varistors can be said to be affected by the sintering temperature.