Abstract: Much of the research on ZnO varistors has concentrated on the explanation of their dc current-voltage characteristics. However, varistors also have unusual ac properties which can be technologically important, and must be described by any comprehensive model. In an ideal varistor with identical grain boundaries throughout, there should be no dispersive capacitance at zero bias. In real varistors this capacitance varies considerably with frequency. This dispersion has two causes, charge trapping in the depletion regions and differing grain boundary barriers. Calculations for each process are given. For voltages well below the varistor breakdown value, the low frequency capacitance increases with applied voltage. At even higher voltages the capacitance turns over and becomes negative. All of these effects can be described with a double depletion layer/thermionic emission model. The anomalous capacitance behavior with bias is due to the modulation of the potential barriers by charge trapping at the grain boundaries. In the varistor breakdown regime minority carriers created by impact ionization are important.

Abstract: An improved varistor-controlled multiplexed liquid crystal display of the type having columns of front electrodes and rows of rear electrodes connected in series with combinations of varistor elements and electrical capacitances, has a capacitance of increased magnitude formed in parallel with the capacitance of the liquid crystal layer in each of the multiplicity of the display cells, for reducing capacitive crosstalk between an addressed and unaddressed cell elements of the display. The increased capacitance is provided by auxiliary data electrodes positioned below, and spaced by a thin film dielectric layer from, the reflective rear cell row electrodes of the display, and spaced from the varistor member by at least one thick film dielectric layer. A pair of thick film layers may support the row scan electrodes therebetween, or the scan electrodes may be formed between a single layer and the varistor surface.

Abstract: A protective circuit for a plurality of series connected thyristors where each thyristor has in parallel with it a resistance, capacitance type snubber circuit and a metal oxide varistor The arrangement of the series connected thyristors, snubber circuits and their metal oxide varistors has in parallel with it a main metal oxide varistor The main varistor is responsive to external transient surges so as to conduct large currents The outer varistors are selected to have values so as to conduct a much smaller or minimal current relative to the current conducted by the main varistor In a preferred arrangement, a tuning inductor is in series with the thyristors, snubber circuits and parallel arranged varistors Also, the main varistor is arranged in parallel with the series connection of thyristor, snubber, varistor combination and inductor, and in series with a bank of capacitors

Abstract: The use of ZnO‐based metal‐oxide‐varistor materials in a transient protection device for communications circuits against the effects of nuclear electromagnetic pulses (NEMP) is discussed. The guidelines for such devices call for subnanosecond response time to NEMP and an insertion loss of less than 0.4 dB at 100 MHz. We have measured the response of varistor materials to ∼500‐ps rise time pulses of various amplitudes and durations. No varistor ’’turn on’’ time is evident in these data indicating that the initiation of the highly nonlinear conduction process takes place in less than 5×10−10 s. The insertion loss is calculated from the known high‐frequency electrical properties and found to agree quite closely with the experimentally determined value of 0.1 dB at 100 MHz for varistor chips of cross section 0.025×0.025 cm and thickness 0.01 cm. A packaging configuration for these chips is also described. We conclude that ZnO varistors have application in an NEMP protective device.

Abstract: A new series capacitor protective system based upon zinc oxide varistor technology has been developed. The new system offers the advantages of instantaneous reinsertion of the series capacitors after an external line section fault and elimination of mechanical action for normal protective operation. This paper describes the general operation of the new system and the equipment and testing of a field prototype.

Abstract: There is disclosed a metal oxide varistor comprising a component of grain bodies composed of zinc oxide and a component of grain boundary layers composed of another metallic oxide, characterized in that at least a portion of these starting materials is a fine particle powder prepared by a co-precipitation method. … The method oxide varistor of the present invention is excellent in varistor characteristics such as non-linearity to voltage, life performances and capability of energy dissipation, is small in a scatter of the above characteristics between manufacture lots or within each lot at the time of manufacture, and has a good quality stability.

Abstract: A free-standing, thick-film varistor is fabricated by screen printing on a smooth aluminum oxide substrate an unfired standard varistor powder mixed with a suitable organic carrier and heating the printed varistor at high temperature (1000° C.-1400° C.). The fabricated varistor adheres lightly to the insulating substrate and may be easily separated therefrom. The insulating substrate may be reused.

Abstract: Capacitance grading is provided within gas insulated lightning arresters containing stacked zinc oxide varistors by means of a grading ring electrically connected to the line terminal or, for arresters of the higher voltage ratings, by means of a plurality of telescoping external electrostatic shields. The shields are arranged so that the degree of overlap between sequential shields decreases from the line end to the ground end of the varistor stacks. The capacitance grading is provided by the degree of overlap between the sequential shields and the ratio of the radii of the overlapping shields.

Abstract: A highly multiplexed liquid crystal display employs nonlinear varistor elements exhibiting a particularly low capacitance value to effectively drive individual liquid crystal cells. Low varistor capacitance is achieved through controlled addition of Sb 2 O 3 during varistor manufacture.

Abstract: The mains power supply transient protection arrangement for electrical apparatuses having electronic circuits which are operated directly from the mains power supply consists of a series circuit which links the mains power supply poles and comprises an over voltage suppressor (F) and a varistor (V) with a reference resistor (R) arranged in parallel with the varistor (V).

Abstract: The device is used in a system comprising a number of components (1-4) divided into two inter-digitated groups. Each group is connected to a current source (6 or 7) of set voltage (Vcc), and each component is connected to a programme transistor (8) via a threshold switch. The threshold switching device consists of a variable resistance element comprising two parts. The first part corresponds to the passage of current from a first current source (6) through the programme transistor (8) via a single component (1), having a threshold voltage (Vi) less than the voltage (Vcc) of the supply. The second part corresponds to the relooping of current from the first current source (6) to the second current source (7) via two components (1,2) programmed by the same programme transistor (8) having a theshold voltage (V2) greater than the voltage of the current source (Vcc).

Abstract: Solderable, largely based metal electrodes for metal oxide varistors are fabricated by screen printing an electrically conductive, air-fireable base metal composition on a varistor material substrate. A distributed fine noble metal array is screen printed over the screened base metal and the varistor heated in air at a temperature of between approximately 500° C. and 800° C. The varistor leads are easily solderable to the noble metal array.

Abstract: Diffusing boron-containing glass, such as bismuth borosilicate glass, into conventional sintered zinc oxide based varistor material reduces varistor material intrinsic capacitance. In the method, a layer of glass powder is screen-printed, painted, or otherwise applied to the varistor material surface. Upon firing, a portion of the glass diffuses into the material, while the remainder creates an insulating layer on the varistor material surface which may be removed by grinding. The varistor material may then be annealed to restore varistor electrical properties which may have been degraded by mechanical damage caused by the grinding. Device electrodes are attached by conventional means.

Abstract: The present invention relates to an overvoltage protection device designed to protect electronic components against high energy transients. The protection device comprises a varistor, across which there is connected a voltage-dividing unit comprising a resistor and a voltage-limiting element, for example a varistor or a Zener diode. The voltage appearing across the voltage-limiting element controls the output signal of the protection device by being connected to the base of a transistor. The input signal to the transistor consists of the input signal of the circuit or the input signal voltage-divided across an input resistor.

Abstract: A high voltage varistor for DC operation is manufactured by applying a glass collar to the perimeter of a sintered zinc oxide disc and heat treated between about 750° C. and 400° C. for several cycles in air. After heat treating, an organic resin or ceramic coating is applied to the glass collar to further insulate the varistor for high voltage application.

Abstract: A bismuth-free, zinc oxide based varistor exhibits a controllable overshoot/undershoot voltage characteristic. The varistor is composed of zinc oxide as the primary constituent, with smaller quantities of barium, boron, one or more transition elements and aluminum. Varistor voltage versus time response is dependent on the degree of aluminum doping. Typically, more than approximately 0.003 mole percent, but less than approximately 0.1 mole percent aluminum is employed, depending on desired voltage overshoot/undershoot characteristic.

Abstract: An assembly for mechanically protecting and electrically insulating metal oxide varistor disks from the generally cylindrical inner wall of a porcelain housing of a surge arrestor. Each assembly comprising a flat metal disk having a diameter less than that of the inner wall of the housing and a plurality of resilient, electrically non-conductive spacer members mounted around the periphery of the disk for supporting the disk vertically in the housing.

Abstract: A new varistor based on TiO2 ceramic was developed. TiO2 ceramics with the dopant ranges of 0 ≼ Nb ≼ 2% and 0 ≼ Ba ≼ 2% were prepared and their electrical properties were measured. In these dopant ranges, several compositions were discovered to have useful varistor properties with a voltagecurrent nonlinearity index of α ≽ 3. It was found that Ba dopant which segregates at grain boundaries and an oxidizing atmosphere during cooling are necessary to produce varistor properties in (Nb,Ba)-doped TiO2. Nb was introduced to decrease the TiO2 lattice resistivity to a range useful for device applications. Resistivity data were measured as functions of dopant composition and sintering atmospheres. Data were analyzed in terms of the defect structure in TiO2.

Abstract: This invention relates to a composite function element which includes a high resistance thin film layer containing the constitutional elements of a perovskite type oxide and specified impurity elements at the grain boundary of a sintered body, said sintered body comprises an agglomerate of n type semiconductor particles and to a process for producing said composite function element. The composite function element has a composite function such that it acts as a varistor passing high voltages at a high voltage and as a capacitor passing the currents of abnormal frequency zone at a low voltage, so that the functions of two elements, a varistor and a capacitor, can be fulfilled simultaneously with only one element. Therefore, its extensive application in uses such as, for example, prevention of erroneous operation of microcomputer-controlled instruments can be expected.

Abstract: PURPOSE:To facilitate change of setting of detected temperature and also to heighten reliability, by operating open-and-close motions on the basis of voltage- current characteristics based upon the element, the impressed voltage and the temperature. CONSTITUTION:A common electrode 5 and independent electrodes 6A1-6A5, which are facing each other through different intervals toward the common electrode 5, are formed on a heat-resistant and insulating substrate 4. Chip varistors or glaze varistors 1A1-1A5, etc. are attached between the common electrode 5 and all the electrodes 6A1-6A5 as a varistor alley. Because lengths of all the varistors 1A1-1A5 are ranging from l1-l5 and voltages at a temperature are varied among the varistors 1A1-1A5, it is able to function as a multipoint temperature detecting element.

Abstract: The intergranular layer and its microstructure, proposed earlier to behave non-linearly in the ZnO/Bi2O3 varistor ceramic system, has been studied by XPS. Our results clearly indicate the formation of an intergranular layer rich in Bi2O3 separating the semiconducting ZnO grains. With increase in sintering temperature, XPS results show the enrichment of the intergranular layer (Bi2O3 phase) without an additional phase being formed. The non-linear coefficient (α) in the current–voltage characteristic increases smoothly up to 1300°C. Afterwards, there is a loss of Bi ions from the Bi2O3 enriched intergranular phase resulting in the decrease of α, and in the characteristic XPS peak intensity.

Abstract: The conditions leading to thermal runaway in metal oxide varistors are discussed in terms of its power dissipation. An equivalent circuit is used to rationalize the similarities and differences between the DC and 60 Hz ac behavior.

Abstract: A high voltage varistor for DC operation is manufactured by applying a glass collar to the perimeter of a sintered zinc oxide disc and heat treated between about 750° C. and 400° C. for several cycles in air. After heat treating, an organic resin or ceramic coating is applied to the glass collar to further insulate the varistor for high voltage application.

Abstract: The electrical breakdown of gas-filled gaps is currently being used in Lightning Arrestor Connectors. The Lightning Arrestor Connector (LAC) is a combination connector and high-current transient suppressor where an overvoltaged signal is shunted from the connector contacts to the connector shell, thus protecting downstream circuitry. Control of the breakdown voltage is difficult, relying on electrode spacing and surface conditions, and the gas composition and pressure. The breakdown control using solid state devices such as a zener diode or a varistor would be far superior, but the current carrying capacity is greatly reduced. A varistor-initiated gas breakdown gap has been developed which has excellent breakdown control and can handle much higher currents than would be possible from the solid-state conduction of the varistor alone. The varistor-initiated arc concept involves the surface flashover of a doped sintered zinc oxide varistor. The varistor-initiated arc LAC is simple in design and easy to produce.

Abstract: A lead germante phase, (Pb 5 Ge 3 O 11 ) is added to a ceramic sintered body formed from a polycrystalline alkaline earth metal titanate which has been doped with a small quantity of metal oxide to produce a N-type conductivity A thin insulating layer of this germante is formed at the grain boundaries of the polycrystalline semiconducting alkaline earth metal titanate because of the formation of a liquid phase during sintering Thus, the varistor effect is immediately available in the overall volume of the resistance body and need not first be induced by means of a forming procedure, as is the case for known resistors formed from N-doped barium titanate