US3634337A - Barium-modified zinc oxide voltage variable resistor - Google Patents
Barium-modified zinc oxide voltage variable resistor Download PDFInfo
- Publication number
- US3634337A US3634337A US869470A US3634337DA US3634337A US 3634337 A US3634337 A US 3634337A US 869470 A US869470 A US 869470A US 3634337D A US3634337D A US 3634337DA US 3634337 A US3634337 A US 3634337A
- Authority
- US
- United States
- Prior art keywords
- oxide
- voltage variable
- mole percent
- barium
- variable resistor
- 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
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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
- a voltage variable resistor ceramic composition consisting essentially of zinc oxide and, as an additive, barium oxide.
- the barium-modified zinc oxide voltage variable resistor has improved voltage nonlinear properties due to the further addition of strontium oxide, lead oxide, calcium oxide, cobalt oxide and bismuth oxide.
- This invention relates to compositions of voltage variable resistor ceramics having non-ohmic resistance, and more particularly to compositions of varistors comprising zinc oxide having non-ohmic resistance due to the bulk thereof.
- n a numerical value greater than 1. The value of n is calculated by the following equation:
- n lfl 2/ 1) 810 a/ 1) where V and V are the voltages at given currents I and I respectively.
- the desired value of C depends upon the kind of application to which the resistor is to be put. It is ordinarily desirable that the value of n be as large as possible since this exponent determines the extent to which the resistors depart from ohmic characteristics.
- varistors comprising germanium or silicon p-n junction diodes
- it is diificult to control the 0 value over a wide range because the voltage variable property of these varistors is not attributed to the bulk but to the p-n junction.
- silicon carbide varistors have voltage variable properties due to the con: tacts among the individual grains of silicon carbide bonded together by a ceramic binding material, and the C-value is controlled by changing a dimension in a direction in which the current flows through the varistors.
- Silicon carbide varistors however, have a relatively low n-value and are prepared by firing in non-oxidizing atmosphere, especially for the purpose of obtaining a lower C-value.
- An object of the present invention is to provide a composition of a voltage variable resistor having nonohmic properties due to the bulk thereof and having a controllable C-value.
- Another object of the present invention is to provide a composition of a voltage variable resistor characterized by a high n-value.
- reference character 10 designates, as a whole, a voltage variable resistor comprising, as its active element, a sintered body having a pair of electrodes 2 and 3 applied to opposite surfaces thereof.
- Said sintered body 1 is prepared in a manner hereinafter set forth and is in any form such as circular, square or rectangular plate form.
- Wire leads 5 and 6 are attached conductively to the electrodes 2 and 3, respectively, by a connection means 4 such as solder or the like.
- a voltage variable resistor according to the invention comprises a sintered body of a composition consisting essentially of 90.0 to 99.95 mole percent of zinc oxide and 0.05 to 10.0 mole percent of barium oxide.
- Such a voltage variable resistor has non-ohmic resistances due to the bulk itself. Therefore, its C-value can be changed without impairing the n-value by changing the distance between said opposite surfaces. The shorter distance results in the lower C-value.
- n-value can be obtained when said sintered body consisting essentially of 97.0 to 99.9 mole percent of zinc oxide and 0.1 to 3.0 mole percent of barium oxide in accordance with the invention.
- the stability for ambient temperature and the electric load life test can be improved when said sintered body consists essentially of 82.0 to 99.9 mole percent of zinc oxide, 0.05 to 10.0 mole percent of barium oxide and 0.05 to 8.0 mole percent of calcium oxide.
- said sintered body consists essentially of 94.0 to 99.8 mole percent of zinc oxide, 0.1 to 3.0 mole percent of barium oxide and 0.1 to 3.0 mole percent of calcium oxide.
- the n-value is elevated when said sintered body consists essentially of 82.0 to 99.9 mole percent of zinc oxide, 0.05 to 10.0 mole per cent of barium oxide and 0.05 to 8.0 mole percent of one oxide selected from the group consisting of strontium oxide, lead oxide and cobalt oxide.
- n-value is further elevated when said sintered body is of a composition consisting essentially of 94.0 to 99.8 mole percent of zinc oxide, 0.1 to 3.0 mole percent of barium oxide and 0.1 to 3.0 mole percent of one oxide selected from the group consisting of strontium oxide, lead oxide and cobalt oxide.
- a combination of a high n-value and a low C-value can be obtained when said sintered body is of a composition consisting essentially of 74.0 to 99.85 mole percent zinc oxide, 0.05 to 10.0 mole percent of barium oxide, 0.05 to 8.0 mole percent of bismuth oxide and 0.05 to 8.0 mole percent of one oxide selected from the group consisting of strontium oxide and lead oxide.
- the C-value is lowered and the n-value is extremely elevated when said sintered body is of a composition consisting essentially of 91.0 to 99.7 mole percent of zinc oxide and 0.1 to 3.0 mole percent of barium oxide, 0.1 to 3.0 mole percent of bismuth oxide, and 0.1 to 3.0 mole percent of one oxide selected from the group consisting of strontium oxide and lead oxide.
- the high n-value also can be obtained when said sintered body is of a composition consisting essentially of 74.0 to 99.85 mole percent of zinc oxide, 0.05 to 10.0 mole percent of barium oxide and 0.05 to 8.0 mole percent of lead oxide and 0.05 to 8.0 mole percent of one oxide selected from the group consisting of strontium oxide and cobalt oxide.
- the extremely high n-value can be obtained when said sintered body is of a composition consisting essentially of 91.0 to 99.7 mole percent of zinc oxide and 0.1 to 3.0 mole percent of barium oxide, 0.1 to 3.0 mole percent of lead oxide, and 0.1 to 3.0' mole percent of one oxide selected from the group consisting of strontium oxide and cobalt oxide.
- the sintered body 1 can be prepared by a per se well known ceramic technique.
- the starting materials of the compositions described in the foregoing description are mixed in a wet mill so as to produce homogeneous mixtures.
- the mixtures are dried and pressed in a mold into desired shapes at a pressure from 100 kg./cm. to 1000 kg./cm.
- the pressed bodies are sintered in air at a given temperature for 1 to 3 hours, and then furnacecooled to room temperature (about to about C.).
- the available sintering temperature is determined in view of electrical resistivity, non-linearity and stability and ranges from 1000 to 1450 C.
- the pressed bodies are preferably sintered in nonoxidizing atmosphere such as nitrogen and argon when it is desired to reduce the electrical resistivity.
- the mixtures can be preliminarily calcined at 700 to 1000 C. and pulverized for easy fabrication in the subsequent pressing step.
- the mixture to be pressed can be admixed with a suitable binder such as water, polyvinyl alcohol, etc.
- the sintered body be lapped at the opposite surfaces by abrasive powder such as silicon carbide in a particle size of 300 meshes to 1500 meshes.
- the sintered bodies are provided, at the opposite surfaces thereof, with electrodes in any available and suitable method such as electroplating method, vacuum evaporat tion method, metallizing method by spraying or silver painting method.
- the voltage variable properties are not practically affected by the kinds of electrodes used, but are affected by the thickness of the sintered bodies. Particularly, the C- value varies in proportion to the thickness of the sintered bodies, while the n-value is almost independent of the thickness. This surely means that the voltage variable property is due to the bulk of the body, but not to the electrode.
- Lead wires can be attached to the electrodes in a per se conventional manner by using conventional solder having a low melting point. It is convenient to employ a conductive adhesive comprising silver powder and resin in an or anic solvent in order to connect the lead wires to the V electrodes.
- Voltage variable resistors according to this invention have a high stability to temperature and in the load life test, which is carried out at C. at a rating power for 500 hours. The n.-value and C-value do not change remarkably after heating cycles and load life test. It is advantageous for achievement of a high stability to humidity that the resultant voltage variable resistors are embedded in a humidity proof resin such as epoxy resin and phenol resin in a per se well known manner.
- EXAMPLE 1 A mixture of zinc oxide and barium oxide in a composition of Table 1 are mixed in a wet mill for 3 hours. The mixture is dried and then calcined at 700 C. for 1 hour. The calcined mixture is pulverized by the motordriven ceramic mortar for 30 minutes and then pressed in a mold into a shape of 17.5 mm. in diameter and 2.5 mm. in thickness at a pressure of 500 kg./cm.
- the pressed body is sintered in air at 1350 C. for 1 hour, and then furnace-cooled to room temperature (about 15 to about 30 C.).
- the sintered disc is lapped at the opposite surfaces thereof by silicon carbide in a particle size of 600 meshes. Resulting sintered disc has a size of 14 mm. in diameter and 1.5 mm. in thickness.
- the silver point electrodes commercially available are attached to the opposite surfaces of sintered disc by painting. Then lead wires are attached to the silver electrodes by soldering. The electric characteristics of the resultant resistors are shown in Table 1.
- the zinc oxide sintered body incorporated with barium oxide in an amount of 0.05 to 10.0 mole percent is available for the voltage variable resistor, and particularly the addition of barium oxide in an amount of 0 .1 to 3.0 mole percent makes the voltage nonlinear property more excellent.
- the pressed body is sintered in air at 1350 C. for 1 hour, and then furnace-cooled to room temperature.
- the sintered disc is ground at the opposite surfaces thereof into the thickness shown in Table 2 by silicon carbide in a particle size of 600 meshes.
- the ground disc is provided with the electrodes and lead wires at the opposite surface in a manner similar to that of Example 1.
- the electric characteristics of the resultant resistors are shown in Table 2; the C-value varies approximately in proportion to the thickness of the sintered disc while the n-value is essentially independent of the thickness. It will be readily realized that the voltage nonlinear properties of the resistors are attributed to the sintered body itself.
- EXAMPLE 3 Zinc oxide incorporated with barium oxide and calcium oxide in the composition of Table 3 is fabricated into the voltage variable resistors by the same process as that of Example 1. The resulting resistors are tested according to the methods used in the electronic components parts. The load life test is carried out at 70 C. ambient temperature at 0.5 watt rating power for 500 hours. The heating cycle test is carried out by repeating 5 times the cycle in which said resistors are kept at C. ambient temperature for 30 minutes, cooled rapidly to 20 C. and then kept at such temperature for 30 minutes. Table 3 shows a difference in C-values and n-values after the load life test. It can be readily realized that the combination of barium oxide and calcium oxide as additive is effective for the electrical and environmental stability.
- Zinc oxide containing additions of Table 6 is fabricated into the voltage variable resistors by the same process as that of Example 1.
- the electrical properties of the resulting resistors are shown in Table 6. It will be easily realized that the combination of barium oxide and bismuth oxide with lead oxide or strontium oxide as additives results in a remarkably excellent n-value and at the same time in a lower C-value.
- a voltage variable resistor ceramic composition consisting essentially of zinc oxide and 0.05 to 10.0 mole percent of barium oxide.
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Thermistors And Varistors (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Inorganic Insulating Materials (AREA)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP43082128A JPS495557B1 (nl) | 1968-11-08 | 1968-11-08 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3634337A true US3634337A (en) | 1972-01-11 |
Family
ID=13765760
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US869470A Expired - Lifetime US3634337A (en) | 1968-11-08 | 1969-10-27 | Barium-modified zinc oxide voltage variable resistor |
Country Status (6)
Country | Link |
---|---|
US (1) | US3634337A (nl) |
JP (1) | JPS495557B1 (nl) |
DE (1) | DE1954056C3 (nl) |
FR (1) | FR2022907A1 (nl) |
GB (1) | GB1285380A (nl) |
NL (1) | NL150256B (nl) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2500291A1 (de) | 1974-02-20 | 1975-08-21 | Matsushita Electric Ind Co Ltd | Spannungsabhaengiger widerstand |
JPS5385400A (en) * | 1977-01-06 | 1978-07-27 | Tdk Corp | Porcelain composite for voltage non-linear resistor |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3928245A (en) * | 1973-07-09 | 1975-12-23 | Gen Electric | Metal oxide voltage-variable resistor composition |
CH596647A5 (nl) * | 1976-07-01 | 1978-03-15 | Bbc Brown Boveri & Cie | |
JPS6240988U (nl) * | 1985-08-30 | 1987-03-11 |
-
1968
- 1968-11-08 JP JP43082128A patent/JPS495557B1/ja active Pending
-
1969
- 1969-10-22 GB GB51695/69A patent/GB1285380A/en not_active Expired
- 1969-10-22 DE DE1954056A patent/DE1954056C3/de not_active Expired
- 1969-10-27 US US869470A patent/US3634337A/en not_active Expired - Lifetime
- 1969-11-06 NL NL696916779A patent/NL150256B/nl not_active IP Right Cessation
- 1969-11-07 FR FR6938470A patent/FR2022907A1/fr active Pending
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2500291A1 (de) | 1974-02-20 | 1975-08-21 | Matsushita Electric Ind Co Ltd | Spannungsabhaengiger widerstand |
DE2500291B2 (de) | 1974-02-20 | 1977-02-10 | Matsushita Electric Industrial Co., Ltd., Kadotna, Osaka (Japan) | Spannungsabhaengiger widerstand mit einer spannungsabhaengigkeit allein aufgrund der masse seines gesinterten koerpers |
JPS5385400A (en) * | 1977-01-06 | 1978-07-27 | Tdk Corp | Porcelain composite for voltage non-linear resistor |
JPS5615561B2 (nl) * | 1977-01-06 | 1981-04-10 |
Also Published As
Publication number | Publication date |
---|---|
NL150256B (nl) | 1976-07-15 |
DE1954056B2 (de) | 1972-07-20 |
DE1954056C3 (de) | 1975-11-27 |
NL6916779A (nl) | 1970-05-12 |
JPS495557B1 (nl) | 1974-02-07 |
GB1285380A (en) | 1972-08-16 |
FR2022907A1 (nl) | 1970-08-07 |
DE1954056A1 (de) | 1970-07-02 |
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