US3836483A - Oxide varistor - Google Patents

Oxide varistor Download PDF

Info

Publication number
US3836483A
US3836483A US00256298A US25629872A US3836483A US 3836483 A US3836483 A US 3836483A US 00256298 A US00256298 A US 00256298A US 25629872 A US25629872 A US 25629872A US 3836483 A US3836483 A US 3836483A
Authority
US
United States
Prior art keywords
varistor
voltage
sic
mol percent
curve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00256298A
Other languages
English (en)
Inventor
N Ichinose
Y Yokomizo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toshiba Corp
Original Assignee
Tokyo Shibaura Electric Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP3475671A external-priority patent/JPS5118076B1/ja
Priority claimed from JP4056371A external-priority patent/JPS5118637B1/ja
Priority claimed from JP47010961A external-priority patent/JPS522119B2/ja
Application filed by Tokyo Shibaura Electric Co Ltd filed Critical Tokyo Shibaura Electric Co Ltd
Application granted granted Critical
Publication of US3836483A publication Critical patent/US3836483A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
    • H01C7/105—Varistor cores
    • H01C7/108—Metal oxide
    • H01C7/112—ZnO type

Definitions

  • NONLINEAR VOLTAGE COEFFICIENT (0Q) N CONTENT OF BizOs (weight United States Patent M U.S. Cl. 252-519 1 Claim ABSTRACT OF THE DISCLOSURE Oxide varistor comprising a basic composition (totaling 100 mol percent) formed of 87 to 12 mol percent of ZnO, l to 30 mol percent of Sb O and 12 to 87 mol percent of at least one metal oxide selected from the group consisting of MgO, CoO, NiO, BaO, SrO, CaO, MnO, FeO and CuO and an additive consisting of 0.5 to by weight of Blgog based on said basic composition.
  • This invention relates to a varistor prepared from an oxide semiconductor.
  • Typical known varistors consisting of a semiconductor are SiC varistors.
  • SiC varistors have nonlinear voltage-current characteristics, namely, are sharply reduced in resistance with higher voltage to permit the passage of current therethro'ugh in amounts increased by that extent and have consequently been widely used for absorbing normally high voltage or for stabilization of voltage.
  • telecommunication apparatus for example, has come to be formed of transistors, resulting in the low operating voltage of circuits. Accordingly, there is growing demand for a low voltage (or low resistance) type of varistor.
  • the voltage-current characteristics of the varistor may be expressed approximately in the following equation:
  • V current flowing through the varistor
  • V- constant
  • u nonlinear voltage coeflicient Therefore, the characteristics of the varistor may be indicated by C and a or two other constants which can replace them. Since accurate determination of C presents extreme difiiculties, C is generally substituted by voltage Vc at a .certain current C ma. With the varistor voltage thus designated as Vc, the voltage current characteristics of the varistor may be indicated by Vc and the nonlinear constant oz.
  • the nonlinearity of the SiC varistor is derived from the voltage sensitivity of the contact resistance of SiC particles.
  • This SiC varistor is generally prepared by mixing SiC powders with porcelain binder material or conductive material like graphite depending on the object intended and sintering the mass at elevated temperatures after it is molded..
  • the varistor is desired to have as large a nonlinear voltage coefiicient a as possible.
  • the aforesaid SiC varistor has a relatively large value (about 3 to 7) of 0c and is stabilized in other electrical properties, so that it may be deemed as adapted for practical application.
  • the SiC varistor has the drawback that it presents ditficulties in being developed into a low voltage type.
  • To obtain a low voltage SiC varistor there have been made attempts to form the varistor into a disc shape in order to reduce its resistance or incorporate conductive material like graphite in order to decrease 3,836,483 Patented Sept. 17, 1974 its specific resistivity.
  • the thinning of the SiC varistor poses problems with its mechanical strength.
  • incorporation of graphite which essentially lacks nonlinearity in connection with resistance will eventually reduce the nonlinear voltage coeflicient of a resultant varistor, thus naturally imposing limits on the formation of a low resistance varistor.
  • the SiC varistor presents difliculties in having its voltage Vc reduced to, for example, less than 10 volts and consequently is unsuitable for low voltage application.
  • the varistor of this invention comprises a basic composition (totaling mol percent) formed of M01 percent ZnO 87 to 12 MeO 12 to 87 SbgO 1 to 30 where:
  • MeO one selected from the group consisting of BaO SrO, CaO, MgO, CoO, NiO, MnO, FeO and CuO and a minor component formed of 0.5 to 10% by weight of Bi O based on said basic composition.
  • FIGS. 1 to 6 indicate the voltage-current characteristics of the basic composition of an oxide varistor according to this invention: FIGS. 1 to 3 are curve diagrams showing the relationship of the content of Sb O defined with respect to the prescribed proportions of ZnO and MeO and the resistance of the varistor; and FIGS. 4 to 6 are curve diagrams showing the relationship of the mol ratio of ZnO to MeO (with the proportion of Sb O fixed) and the resistance of the varistor;
  • FIG. 7 is a curve diagram indicating the relationship of the proportion of Bi O and the nonlinear voltage coefiicient of the oxide varistor of this invention by way of illustrating its properties.
  • FIG. 8(a) is a sectional view schematically showing the arrangement of sintered crystals of the oxide varistor of this invention.
  • FIG. 8(b) is a sectional view schematically showing the arrangement of the sintered SiC crystals of the prior art SiC varistor.
  • the above-mentioned oxide varistor of this invention may by prepared, for example, in the following manner.
  • Raw oxides accurately weighed out to form prescribed proportions are mixed in a ball mill, presintered at relatively low temperatures as 600 to 850C. and later pulverized, for example, in a ball mill into extremely fine powders.
  • the raw materials used may consist of other metal compounds convertible to oxides with heat, for example, hydroxides, carbonates and oxalates of metals.
  • the powders obtained are mixed with a binder, for example, polyvinyl alcohol.
  • the mass is molded at a pressure of 100 to 2000 kg./cm. into a disc about 8 mm. in diameter and about 1 mm. thick, followed by sintering at temperatures of 1000 to 1400 C. in an electric furnace. Said sintering may generally be carried out in the air and a maximum sintering temperature generally has only to be maintained for 1 to hours.
  • FIGS. 1 to 3 present variations in the resistance of a varistor prepared with the mol ratio of ZnO to MeO fixed at 2.0 and the proportion of Sb O varied.
  • the curve (a) denotes the case Where Me represents Ba
  • the curve (b) the case where Me represents Sr
  • the curve (c) the case where Me represents Ca.
  • the voltage-current characteristics of the oxide varistor according to this invention did not vary in any form of its composition, provided the constituents were incorporated in the prescribed proportions, or even when the electrode was formed of silver or In-Ga alloy.
  • This varistor has such a structure as schematically illustrated in FIG. 8(a). Like the SiC varistor whose structure is schematically shown in FIG. 8(b), the varistor of this invention supposedly derives its nonlinear characteristics from the particular phases of the boundaries between the sintered fine crystals of raw materials used and is constituted by innumerable agglomerations of said boundary phases. Referring to FIGS. 8(a) and 8(b), numerals (3) and (3') respectively represent paired electrodes, (1') SiC particles and (2) a binding agent.
  • the varistor of this invention is widely different from the conventional SiC varistor in that the nonlinearty characteristics of the former varistor originate in the boundary zones between individual grains of the sintered materials, that is, in the contacting zones of the grains, in contrast to SiC varistors whose characteristics originate in contact resistance. Said difference may be deemed to have a prominently favorable effect on the voltage-current characteristics of the varistor of this invention.
  • the SiC varistor indeed resembles the present varistor in that the voltage of the SiC varistor can be limited within a considerably broad range, namely, its voltage can be adjusted to any desired level by controlling a number of serially arranged nonlinearity boundaries or the width thereof. But the SiC varistor is distinctly different from the varistor of this invention whose voltagecurrent characteristics and the size of the crystal particle can be relatively freely varied. With the SiC varistor, the.
  • the size of its crystals is primarily determined by the SiC particles constituting the main raw material which do not widely vary even by the sintering process.
  • the powders of start ing raw materials have a particle size ranging preferably approximately between 0.1 and 1 micron.
  • said particle size can be increased by sintering to several or scores of microns.
  • the present varistor has the further advantage that not only the particle size but also the specific resistivity of the fine grains of the raw material can be controlled by varying the composition, the kind of additives or the sintering conditions, thereby rendering the varistor more adapted for practical application.
  • the SiC varistor does not display much desired nonlinearity characteristics, which is supposed to originate from the fact that SiC itself does not have an appreciably low specific resistivity and said resistivity can not be easily controlled.
  • varistor voltage is less than 0.005%, which is much smaller than those known of a Zener diode i.e., about 0.1%, or of SiC varistor i.e., 0.1 to 0.2%. It will be also found that its surge current is very large. It is more than 100 times as high as that for a Zener diode.
  • An oxide varistor having a nonlinear voltage co efficient greater than 7 comprising a basic composition (totaling 100 mol percent) consisting of 87 to 12 mol percent of ZnO, 1 to mol percent of Sb O and 12 to 87 mol percent of at least one metal oxide selected from the group consisting of MgO, CoO, NiO, BaO, SrO, CaO, MnO, FeO and C110, and an additive consisting of 0,5 to 10 percent by weight of Bi O based on said basic composition.
US00256298A 1971-05-24 1972-05-24 Oxide varistor Expired - Lifetime US3836483A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP3475671A JPS5118076B1 (de) 1971-05-24 1971-05-24
JP4056371A JPS5118637B1 (de) 1971-06-10 1971-06-10
JP47010961A JPS522119B2 (de) 1972-02-01 1972-02-01

Publications (1)

Publication Number Publication Date
US3836483A true US3836483A (en) 1974-09-17

Family

ID=27279193

Family Applications (1)

Application Number Title Priority Date Filing Date
US00256298A Expired - Lifetime US3836483A (en) 1971-05-24 1972-05-24 Oxide varistor

Country Status (8)

Country Link
US (1) US3836483A (de)
AU (1) AU456931B2 (de)
CA (1) CA973348A (de)
CH (1) CH563652A5 (de)
DE (1) DE2225431C2 (de)
FR (1) FR2138981B1 (de)
GB (1) GB1397782A (de)
SE (1) SE373685B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3991340A (en) * 1973-08-20 1976-11-09 Tokyo Shibaura Electric Co., Ltd. Discharge lamp lighting apparatus including a sintered type oxide negative resistance starting element
US4042535A (en) * 1975-09-25 1977-08-16 General Electric Company Metal oxide varistor with improved electrical properties
US4086189A (en) * 1975-11-14 1978-04-25 Otowa Electric Company, Ltd. Resistive element having voltage non-linearity and method of making same
US4336163A (en) * 1973-07-09 1982-06-22 Tokyo Shibaura Electric Co., Ltd. Oxide negative resistance element

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2286804A1 (fr) * 1974-10-01 1976-04-30 Thomson Csf Materiau et procede de fabrication de pieces en ceramique pour varistances

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4336163A (en) * 1973-07-09 1982-06-22 Tokyo Shibaura Electric Co., Ltd. Oxide negative resistance element
US3991340A (en) * 1973-08-20 1976-11-09 Tokyo Shibaura Electric Co., Ltd. Discharge lamp lighting apparatus including a sintered type oxide negative resistance starting element
US4042535A (en) * 1975-09-25 1977-08-16 General Electric Company Metal oxide varistor with improved electrical properties
US4086189A (en) * 1975-11-14 1978-04-25 Otowa Electric Company, Ltd. Resistive element having voltage non-linearity and method of making same

Also Published As

Publication number Publication date
FR2138981B1 (de) 1980-03-07
DE2225431A1 (de) 1972-11-30
GB1397782A (en) 1975-06-18
FR2138981A1 (de) 1973-01-05
AU456931B2 (en) 1975-01-16
SE373685B (sv) 1975-02-10
CH563652A5 (de) 1975-06-30
CA973348A (en) 1975-08-26
DE2225431C2 (de) 1982-11-25
AU4257972A (en) 1973-12-20

Similar Documents

Publication Publication Date Title
US3903226A (en) Method of making voltage-dependent resistors
US3996168A (en) Ceramic electrical resistor
US3836483A (en) Oxide varistor
US3373120A (en) Semiconductive ceramic compositions with positive temperature coefficient of resistance
US2703354A (en) Alkaline earth manganate ceramics
US3899451A (en) Oxide varistor
US5973589A (en) Zno varistor of low-temperature sintering ability
US3842018A (en) Oxide varistor composition consisting of zno,sb2o3 and/or sb2o5,zro2,tio2 and/or geo2,and bi2o3
US4184984A (en) High breakdown voltage varistor
US3925261A (en) Exponential resistance material and method of manufacturing same
JPS606522B2 (ja) 半導体組成物
US3341473A (en) High beta thermistors
JP2789714B2 (ja) 電圧依存性非直線抵抗体磁器組成物およびバリスタの製造方法
JPH0128481B2 (de)
JPH0142613B2 (de)
JP2985559B2 (ja) バリスタ
JPH0128483B2 (de)
JPH0128486B2 (de)
JPH0128485B2 (de)
JPH03195003A (ja) 電圧非直線抵抗体
JPH0128482B2 (de)
JPH0128487B2 (de)
JPH06120008A (ja) 電圧非直線抵抗体磁器組成物の製造方法
JPH0574608A (ja) 電圧非直線抵抗体の製造方法
JPS6028203A (ja) 電圧非直線抵抗体の製造方法