Abstract: The electrical properties of (Nb, Zn)-doped SnO2 ceramics as an new varistor material were investigated. It was found that there exists a correlation between the nonlinearity of the current density versus the electrical field, the frequency properties of relative permittivity and resistivity. Samples doped with 1.0 mol% ZnO and 0.05 mol% Nb2 O5 , which possess a comparatively low dielectric constant and the highest resistivity of all of the samples investigated, exhibits a higher nonlinear coefficient than the other samples. A defect barrier model for ZnO-based varistor has been adapted to explain the nonlinearity of the SnO2 -based varistor.

Abstract: A ferroelectric field effect transistor memory cell (100) includes a thin film varistor (122) located between the gate electrode (120) and the ferroelectric layer (126). The varistor protects the ferroelectric layer from disturb voltage pulses arising from memory read, write and sense operations. A second electrode (124) is located between the thin film varistor and the ferroelectric layer. The thin film ferroelectric is positioned over the channel (128) of a transistor (100) to operate as a ferroelectric gate. For voltages at which disturb voltages are likely to occur, the thin film varistor has a resistance obeying a formula Rd ⊃ 10 X 1/(2πfCF), where Rd is resistivity of the thin film varistor, f is an operating frequency of said memory, and CF is the capacitance of the ferroelectric layer. For voltages at or near the read and write voltage of the memory, the thin film varistor has a resistance obeying a formula Rd ⊃ 0.1 x 1/(2πfCF).

Abstract: A new varistor system of SnO 2 -Bi 2 O 3 -Nb 2 O 5 was reported in this paper. The electrical field-current density characteristics of this system were investigated by doping different amounts of Bi 2 O 3 and sintering the samples at various temperatures. It is found that adding 0.75 mol% Bi 2 O 3 to Nb-doped SnO 2 ceramic resulted in maximum nonlinear coefficient and breakdown voltage with α = 14 and E 0.5 = 19 525 V/cm. To improve the density as well as the nonlinearity of this system, different amounts of Co 2 O 3 were added. The optimal conditions for the best nonlinearity were 1300 °C with 0.03 mol% Co 2 O 3 addition. Deviation from this doping content, toward either higher or lower Co 2 O 3 content, causes the deterioration of I−V characteristics. It can be concluded that the incorporation of cobalt oxides into SnO 2 -based varistors improves the nonlinearity in the low and intermediate current density regions because of the increased barrier height . The experimental results were explained with the defect barrier model for SnO 2 -based varistors.

Abstract: The Sb2O3-doped TiO2 varistors were obtained by conventional ceramic processing. The 0.75 mol% Sb2O399.25 mol% TiO2 varistor has a nonlinear coefficient α = 7 and a minimum breakdown electrical field of 6 V/mm. The nonlinear electrical behaviour of TiO2Sb2O3 ceramics was explained by the introduction of defects in the crystal lattice that are responsible for the formation of Schottky potential barriers at grain boundaries.

Abstract: The invention relates to a low capacity multilayer varistor that consists of a ceramic body (1) and two connections (2, 3) that are applied on the ceramic body (1) at a distance to each other. Said ceramic body (1) is configured as a multilayer structure produced by film techniques and preferably comprises internal electrodes (4, 5) whose ends face each other with a gap (d).

Abstract: In testing and in service, varistors are subjected to very short (μs range) high current pulses. Due to the inertia effects that appear on rapid Joule heating dynamic stress waves are generated, which can cause brittle failure. An analytical solution for the one-dimensional case was presented recently by Vojta and Clarke. In this work a full three-dimensional analysis of an axisymmetrical varistor has been performed using Finite Element Simulation. The reflections of the stress waves from the bases and the shell of a varistor and their interference are analyzed. The resulting stress field and its development with time is much more complex than in the 1D case. The aspect ratio of the varistor has been shown to have a strong influence on the amplitude of the mechanical stresses and can be varied to minimize the maximum stress level reached. Damping has been considered but found to be negligible in realistic cases.

Abstract: A series of zinc oxide based varistors containing 0.5 wt.% Bi 2 O 3 and 0.5 wt.% Mn 2 O 3 were prepared by a conventional mixed oxide route and sintered at temperatures between 950 and 1300°C. All samples showed the varistor effect, although as the sintering temperature was increased above 1000°C, the non-linear coefficient decreased from 22 to 3 at 1300°C. Local grain boundary property measurements were carried out using remote electron beam induced current (REBIC) configuration conductive mode scanning electron microscopy. The proportions of electrically active interfaces and those showing strong resistive contrast were found to increase with sintering temperature.

Abstract: SiC, preferably in single crystal form, is employed as an IR radiation sensor with high temperature and power capabilities. Applications include sensing the power or energy from an IR radiation source, a contactless temperature sensor for another body heated by IR radiation, and an IR controlled varistor.

Abstract: Said lead-through has a current conductor (1) to which high voltage can be fed. A section of the current conductor (1) is surrounded by a varistor array (9). The lead-through also contains two supply terminals (4, 6), one (6) of which can be connected to high voltage and the other (4) is connected to ground, a lead-through insulator (5) provided between the current conductor (1) and the varistor array, in addition to a clamping device (11) that exerts a contact force on the supply terminals (4, 6) and the varistor array (9) placed in the form of a sandwich between the latter. The clamping device has an insulating part that exerts a contact force on both supply terminals. The lead-through insulator is embodied in the form of a shaped body and has a support element provided with a guide surface for a contact (1a) of a plug-type connector that is connected to a current conductor (1) with a cable or a lead-through of an electrical device.

Abstract: A surge protector is for electrical connection between one or more power lines and one or more loads. The surge protector includes an input for electrical connection to the power line and an output for electrical connection to the load. A circuit electrically interconnects the output with the input for passing power therebetween. A metal oxide varistor protects the load from surges or transients on the power line. A voltage monitoring circuit detects an occurrence of an overvoltage event on the power line. A charged capacitor is shorted by the series combination of a fuse and a MOSFET switch to open the fuse and, thereby, permanently record the occurrence of the overvoltage event.

Abstract: Fast firing of Bi2O3-based ZnO varistor materials, which includes zero minutes soaking at 1100°C with 120°C/min heating and 145°C/min cooling rate, was made possible using millimeter-wave sintering (mS) technique. The overall sintering time of the process is less than 18 minutes, and the varistor characteristics obtained are α = 38, JL = 5.55 × 10−6 A/cm2 and Vbk = 600 V/mm, whereas the intrinsic parameters of the materials are φb = 2.84 eV, Nd = 1.85 × 1024 m−3 and Ns = 7.02 × 1011 cm−2. By contrast, conventional sintering (cS) process needs higher sintering temperature (1200°C), longer soaking time (60 min) and slower ramping rate (30°C/min) to obtain ZnO materials with the same marvelous nonlinear properties as those prepared by mS-process. Moreover, millimeter-wave sintering (24 GHz, mS) process enhances the densification kinetics and grain growth behavior more efficiently than the microwave sintering (2.45 GHz, μS) process, resulting in better varistor characteristics for ZnO materials. However, sintering by millimeter-wave for too long period induces overfiring of the samples, which results in a density reversion phenomenon. Such a phenomenon leads to the decrease in surface state (Ns) and the potential barrier height (φb), which are presumed to be the mechanism leading to the degradation of ZnO materials' nonlinear properties.

Abstract: A method of fabricating a monolithic chip varistor includes the steps of preparing a varistor body including a plurality of varistor layers and at least one pair of internal electrodes; forming a first layer for each of a pair of external electrodes by applying a metal component and a glass component to an exterior portion of the varistor body, followed by heat treatment; forming a second layer for the external electrode on the first layer by applying a glass component, followed by heat treatment; forming a third layer for the external electrode on the second layer by applying a glass component that is different from the glass component used for forming the second layer, followed by heat treatment; forming a fourth layer for the external electrode on the third layer by applying a metal component that is different from the metal component used for forming the first layer, followed by heat treatment under the same heat treatment conditions as those used for the formation of the first layer; and forming a fifth layer for the external electrode by electroplating. During the heat treatment for forming the fourth layer, the metal component contained in the fourth layer is diffused into the second layer and the third layer.

Abstract: A ceramic electronic component comprising external electrodes having first electrode layers containing at least a noble metal, cuprous oxide, and glass ingredient electrically connected to internal electrodes having a noble metal. As the ceramic electronic components, for example, a multi-layer ceramic capacitor, multi-layer varistor, multi-layer dielectric resonator, multi-layer piezoelectric element, etc. may be mentioned.

Abstract: A surge protector for single-phase or multi-phase power lines is disclosed, for permanent connection near the entrance of power lines to a building, that has a basic protector sub-circuit of a metal-oxide varistor (MOV) and a gas-discharge tube (GDT) connected in series between the power line and building ground. Preferably, the gas-discharge tube is a three-element GDT and is connected to two metal-oxide varistors. In a multi-phase implementation, the present invention includes one or more protector sub-circuits connected between each power line and ground, wherein each protector sub-circuit includes two metal-oxide varistors connected to a power line and a gas-discharge tube connected to the building ground.

Abstract: A voltage protective circuit for an electronic device comprises a metal oxide varistor for eliminating spikes above a first level, and a Zener diode and a transistor connected in series through a resistor with the metal oxide varistor for eliminating spikes above a second level. The voltage protective circuit can be utilized in a separate, plug-in voltage protector for a vending machine with a multi-drop bus.

Abstract: A surge arrester includes a stack of components having at least one varistor. Each component has end faces, at least one of which is mechanically bonded to an end face of another component such that the combined components of the stack define a single, monolithic structure that serves as both an electrically-active element and a mechanical support element of the surge arrester. The surge arrester also includes an insulative housing surrounding the stack of components. The stack of components is capable of withstanding current pulses having magnitudes of 65 kA and durations of 4/10 microseconds without significant degradation in operating performance of the stack of components.

Abstract: The use of metal-oxide varistors in surge protection modules for telecommunication systems was evaluated. For this purpose, the definition of the device model and its voltage-current characteristics were defined and analyzed in detail. A high voltage impulse generator was developed to generate double exponential currents, in order to recreate the effects of indirect lightning strikes and switching overvoltages. As a result, an experimental setup was developed to record the time response of different nonlinear protective devices. This paper describes the voltage-current characteristics of small packaged varistors and the relation between numerical simulation results and the data recorded from the actual impulse testing of such devices. Additionally, it is intended to be used by engineers and system designers as an initial approach for selecting the adequate nonlinear protective device for telecommunication systems.

Abstract: A transient voltage surge suppressor (TVSS) having a fuse rated to withstand high transient surge currents is disclosed. The TVSS employs metal oxide varistors (MOV's) in close proximity to the fuse such that heat from failed MOV's is used to reduce the time required to blow the fuse. The fuse may be mounted to the metal bus connection of a MOV within a sand-filled or potted box containing the MOV's. Thus, the TVSS of the present invention utilizes a thermally assisted disconnect method which enhances the performance of the TVSS under unusual fault conditions.

Abstract: A metal oxide varistor comprises a hollow ceramic body having an opening, a first electrode within the body and having a portion extending through the opening, and a second electrode disposed on the exterior surface of the body Voltage applied to the electrodes above the device clamping voltage causes the ceramic body to conduct The geometry of the body, which is optimally a sphere, greatly increases surface area between the electrodes and the ceramic body, and consequently increases the device's current carrying capacity

Abstract: The influences of varistor disk capacitance and its distribution on the voltage distribution along an MOV arrester column were investigated. The numerical computation of voltage (or gradient) distribution of the 110 kV-class arrester with a composite housing (or shell) and a porcelain housing were presented respectively. The finite element method (FEM) was used for this computation. The measurement and statistical analysis of processing varistor disk capacitances were also taken. After rearranging the varistor disks, according to their capacitance, the voltage distribution of the arrester became more uniform. The optimal voltage distribution was described using an adaptive method.

Abstract: Zinc Oxide (ZnO) varistor elements which have non-linear current-voltage characteristic have a number of failure mechanism when ZnO varistor elements absorb surge energy. Failure mode at the edge of the aluminum electrode formed by the thermal spraying process on the ZnO varistor element surface is quite common failure mechanism by high current surges. Such failures take the form of a melt pinhole from the electrode edge to the counter electrode or the edge of the disk element. As a result of the transient finite element analysis for the electric and thermal field distribution and the measurement of the resistively-temperature characteristic at high current region, it was made clear that the failure at the electrode edge was caused by the partial melting by the current concentration and the local thermal runaway at the electrode edge. Moreover, the current concentration was reduced by decreasing of the distance between the electrode edge and the sintered ZnO body edge.We developed the aluminum sprayed electrode manufacturing process which could control the edge margin with accuracy. And using this electrode process, the energy absorption capability of the ZnO elements was improved largely by reducing the current concentration at the electrode edge.

Abstract: A varistor includes a voltage-nonlinear resistor and varistor electrodes provided on the upper and lower surfaces of the voltage-nonlinear resistor. The voltage-nonlinear resistor is primarily composed of SiC (silicon carbide) particles which are doped with at least one dopant such as N (nitrogen) and P (phosphorus). The varistor electrodes are composed of a metal, e.g., Ag, Pd, Pt, Al, Ni or Cu. The SiC particles of the voltage-nonlinear resistor further contain at least one element of Al (aluminum) and B (boron) in an amount of about 0.01 to 100 parts by weight with respect to 100 parts by weight of the SiC particles.

Abstract: PROBLEM TO BE SOLVED: To provide a temperature fuse built-in varistor which is never deteriorated in varistor function when an excessive surge voltage is applied from a power supply, high in safety, and excellent in reliability. SOLUTION: A temperature fuse built-in varistor is composed of a varistor element 9, a pair of conductive plates 12 and 13 provided and electrically connected to both surfaces of the element 9, a first terminal 26 connected to the conductive plate 12 out of the pair of the electrodes, a second terminal 27 connected to the other conductive plate 13, a temperature fuse 31 connected to the conductive plates 13 coming into contact with it, and a third terminal 25 connected to the temperature fuse 31 all housed in an insulating case 1.

Abstract: Polycrystalline samples of Pb(Mn1/2W1/2)O3 were prepared by the high-temperature solid-state reaction technique. Preliminary crystal structure and microstructure of the compound at room temperature were studied using the X-ray diffraction (XRD) technique and scanning electron microscopy (SEM), respectively. The dielectric permittivity (e) and loss tangent (tanδ) of the compound were obtained both as a function of frequency (0.5×103−104Hz), at room temperature, and temperature (30 °C–320 °C), at 10 kHz. Both the a.c. and d.c. conductivities have been studied over a wide range of temperature. The forbidden energy gap (Eg) and activation energy (Ea) of the compound were calculated from the plot of d.c. resistivity and a.c. conductivity versus inverse absolute temperature, respectively. The current density–field strength (J–E) characteristics of the compound studied at different temperatures reveals that the compound has excellent varistor behavior. The change in magnitude of the current with time was also studied at different voltage.

Abstract: In order to improve the characteristics of multilayer chip varistors, we have investigated the effects of addi tives on the varistor voltage and the nonlinear coefficient of ZnO-based chip varistor, whose fundamental components were ZnO:CoO:Pr6O11:Al2O3=100:1.0:0.1:0.005 (molar ratio). Selected additives were Cr2O3, MoO3, WO3, and Nb2O5, the extent of addition being from 0.05 to 0.1mol%, respectively. Thermal shrinkage and grain-growth rate were observed. The Capacitance-Voltage (C-V) method was applied for evaluating the electrical properties when the sintering temperature was varied from 1120 to 1230•Ž. All the additives remarkably decreased the shrinkage rate above 1000•Ž. While the grain growth was controlled by the addi tion of any of the selected additives. its rate depended on each species. Additives were not soluble but segregated within the grain and/or at grain boundaries, irrespective of the kind of additive. While the varis tor voltage was generally lowered and the nonlinear coefficient became higher with increasing sintering temperature, their absolute values depended on the kind of additive. Addition of Cr2O3 and MoO3 made avail able a high nonlinear coefficient with a relatively high varistor voltage, thus much improved varistor charac teristics. A factor which influenced the increase of the nonlinear coefficient was interpreted by considering a relative increment of the barrier height, based on the double Schottky barrier model. [Received September 20, 1999; Accepted April 17, 2000]

Abstract: The present invention electricity pod controller device includes: (a) in-parallel connection to an incoming power supply of a facility including a hot line and a neutral line, and at least one ground. There are components connected between the hot line and the neutral line in the following order; (b) at least one front metal oxide varistor line transient voltage surge suppressor having a predetermined capability to suppress undesired power spikes; (c) at least one capacitor of predetermined capacitance; (d) at least two chokes in the form of inductor/metal oxide varistor transformers; (e) at least a second capacitor of its own predetermined capacitance; (f) at least one back metal oxide varistor having a predetermined capability. In preferred embodiments, the metal oxide varistor may be a plurality of varistors in parallel.