US3689863A - Voltage dependent resistors in a surface barrier type - Google Patents

Voltage dependent resistors in a surface barrier type Download PDF

Info

Publication number
US3689863A
US3689863A US3689863DA US3689863A US 3689863 A US3689863 A US 3689863A US 3689863D A US3689863D A US 3689863DA US 3689863 A US3689863 A US 3689863A
Authority
US
Grant status
Grant
Patent type
Prior art keywords
oxide
voltage
silver
dependent
percent
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
Inventor
Michio Matsuoka
Takeshi Masuyama
Yoshio Iida
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.)
Panasonic Corp
Original Assignee
Panasonic Corp
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
Grant date

Links

Images

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01CRESISTORS
    • H01C7/00Non-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
    • H01C7/10Non-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
    • H01C7/105Varistor cores
    • H01C7/108Metal oxide
    • H01C7/112ZnO type
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H01B1/08Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances oxides

Abstract

A voltage dependent resistor of the surface barrier type. A sintered body consisting essentially of, as a major part, zinc oxide (ZnO) and 0.05 to 10.0 mole percent of, as an additive, beryllium oxide (BeO), has electrodes in contact therewith. At least one of the electrodes is in non-ohmic contact with the body. The body can have minor amounts of further additives such as nickel oxide, titanium oxide, barium oxide, stannic oxide, aluminum oxide, lead oxide, cadmium fluoride and thallium oxide.

Description

United States Patent Matsuoka et al.

1451 Sept. 5, 1972 VOLTAGE DEPENDENT RESISTORS IN A SURFACE BARRIER TYPE Inventors: Michio Matsuoka; Takeshi Masuyarna; Yoshio Iida, all of Osaka-fu, Japan Assignee: Matsushita Electric Industrial Co.,

, Ltd., Osaka, Japan Foreign Application Priority Data Dec. 8, 1969 Japan ..44/98789 Apr. 4, i970 Japan..................45/29908 Filed: Nov. 24, 1970 Appl. No.: 92,380

US. Cl. -3338/20, 317/235 AP, 317/238, 317/235 UA, 252/62.3 ZT Int. Cl. ..H0lc 7/10 Field of Search ..317/235 AP, 238, 234, 235; 338/20; 252/623 ZT [56] References Cited UNITED STATES PATENTS 3,611,073 10/1971 Hamamoto ..317/235 3,570,002 3/1971 Masuyama ..317/238 Primary Examiner-J. D. Miller Assistant Examiner-Harvey Fendelman Attamey-wenderoth, Lind & Ponack ABSTRACT A voltage dependent resistor of the surface barrier type. A sintered body consisting essentially of, as a major part, zinc oxide (ZnO) and 0.05 to 10.0 mole percent of, as an additive, beryllium oxide (BeO), has electrodes in contact therewith. At least one of the electrodes is in non-ohmic contact with the body. The body can have minor amounts of further additives such as nickel oxide, titanium oxide, barium oxide, stannic oxide, aluminum oxide, lead oxide, cadmium fluoride and thallium oxide.

10 Claims, 1 Drawing Figure PATENTEDSEP 51912 MI CHI O MATSUOKA, TAKESHI MASUYAMA and YOSHIO IIDA,

INVENTORS ATTORNEYS VOLTAGE DEPENDENT RESISTORS IN A SURFACE BARRIER TYPE This invention relates to voltage dependent resistors of a surface barrier type and more particularly to varistors comprising zinc oxide and beryllium oxide and having nonohmic electrodes applied thereto.

Various'voltage dependent resistors such as silicon carbide varistors, selenium or cuprous oxide rectifiers and germanium or silicon p-n junction diodes, are known. The electrical characteristics of such a voltage dependent resistor are expressed by the relation:

rent flowing through the resistor, C is a constant equivalent to the voltage at a given current and exponent n is a numerical value greater than 1. The value of n is calculated by the following equation:

n: lO 2/ 1) gic (V2/V1) where V and V are. the voltages at given currents I, and 1,, respectively. Conveniently, I and I are 10 mA and 100 mA, 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 degree to which the resistors depart from ohmic characteristics.

Silicon carbide varistors are most widely used as voltage dependent resistors and are manufactured by mixing fine particles of silicon carbide with water, ceramic binder and/or conductive material such as graphite, pressing the mixture in a mold to the desired shape, and then drying and firing the pressed body in air or nonoxidizing atmosphere. Silicon carbide varistors with conductive materials are characterized by a low electric resistance, i.e., a low value of C and low value of n whereas silicon carbide varistors without conductive materials have a high electric resistance, i.e., a high value of C and a high value of n. It has been difficult to manufacture silicon carbide varistors characterized by a high n and a low C. For example, silicon carbide varistors with graphite have been known to exhibit n values from 2.5 to 3.3 and C-values from 6 to 13 at a given current of 100 mA, and silicon carbide varistors without graphite show n-valves from 4 to 7 and C- values from 30 to 800 at a given current of 1 mA with respect to a given size of varistor, e.g., 30 mm in diameter and 1 mm in thickness.

Conventional rectifiers comprising selenium or cuprous oxide have an n-value less than 3 and a C-value of to 10 at a given current of 100 mA with respect to a specimen 20 mm in diameter. In this case, the thickness of the sample does not affect the C-value.

A germanium or silicon p-n junction resistor has an extremely high value of n but its C-value is constant, e.g., on the order of 0.3 to 0.7 at a given current of 100 mA because its diffusion voltage in the V-I characteristic is constant and cannot be changed very greatly. It is necessary for obtaining a desirable C-value to combine several diodes in series and/or in parallel. Another disadvantage of such diodes is the complicated steps involved in their manufacture, with resultant high cost. As a practical matter, the use of diode resistors is not "age dependent resistor, the C-valueof which can be controlled.

These objects are achieved by providing a voltage dependent resistor of the surface barriertype having a sintered body consisting essentially of, as a major part, zinc oxide (ZnO) and 0.05 to 10.0 mole percent of, as an additive, "beryllium oxide (BeO), and electrodes in contact therewith. At least one of the electrodes is in non-ohmic contact with the body. The body can have minor amounts of further additives such as nickel oxide, titanium oxide, barium oxide stannic oxide, aluminum oxide, lead oxide, cadmium fluoride and thallium oxide.

These and other objects of the invention will become apparent upon consideration of the following description taken together with the accompanying drawing in which the single FIGURE is a partly cross-sectional view through a voltage dependent resistor in accordance with the invention.

Before proceeding with a detailed description of the voltage dependent resistors contemplated by the invention, their construction will be described with reference to the aforesaid figure of the drawing wherein reference character 10 designates, as a whole, a voltage dependent resistor having, as its active element, a sintered wafer l of electrically conductive ceramic material according to the present invention.

Sintered wafer 1 is prepared in a manner hereinafter set forth, and is provided with a pair of electrodes 2 and 3 having specified compositionsand applied in a suitable manner hereinafter set forth, on two opposite surfaces of the wafer.

' The wafer 1 is a sintered plate having any one of various shapes such as circular, square, rectangular, etc. Wire leads 5 and 6 are attached conductively to the electrodes 2 and 3, respectively, by a connection means 4 (solder or the like).

According to the present invention, a voltage dependent resistor with an n-value higher-than 5 can be obtained when the resistor comprises a sintered body consisting essentially of, as a major part, zinc oxide (ZnO) and 0.05 to 10.0 mole percent of, as an additive, beryllium oxide (BeO) and electrodes in contact with said body, at least one of which makes non-ohmic contact.

It has been discovered according to the invention that said sintered body 1 has a superior voltage dependent properties when it is provided with silver electrodes prepared by applying silver paint to opposite surfaces thereof and firing at to 850 C. in an oxidizing atmosphere such as air and oxygen. The n-value and C-value of thus produced voltage dependent'resistors vary with the compositions of the sintered body and electrodes, and their method of preparation. The stability of the resistor with silver paint electrodes is improved when said additive consists essentially of 1.0 to 8.0 mole percent of beryllium oxide (BeO).

Since the voltage dependent property of the novel resistoris attributable to the a non-ohmic property of a barrier formed between said sintered body 1 and electrodes 2 and/or 3, it is necessary for obtaining a desirable C-value and n-value to control the compositions of the sintered body 1 and the electrodes 2 and 3.

It is necessary for achieving a low'value of'C for the resultant voltage dependent resistors that the sintered body have an electrical resistivity less than ohm-cm, said electrical resistivity being measured by a four point method in a per se conventional way.

Table 1 shows optimal compositions of sintered body 1 for producing a voltage dependent resistor having an n-value higher than 7 and a high stability with respect to temperature, humidity and electric load.

Table 2 shows operable and optimal compositions of silver electrodes 2 and/or 3 after heat treatment.

In the Table 2, the sum of the weight percents of all ingredients should be adjusted so as to be 100 weight percent by controlling the weight percent of individual ingredients within operable or optimal weight percents as indicated in the Table.

The sintered body 1 can be prepared by a per se well known ceramic technique. The starting materials in the compositions defined above 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 ml ,000 kg/cm The pressed bodies are sintered in air at 1,000 to l,450 C. for l to 3 hours, and then furnace-cooled to room temperature (about to about 30 C). The pressed bodies are preferably sintered in a non-oxidizing atmosphere such as nitrogen and argon when it is desired to reduce the electrical resistivity. The electrical resistivity also can be reduced by air-quenching from the sintering temperature to room temperature even when the pressed bodies are fired in air.

The mixture may be preliminarily calcined at 700 to 1,000 C. and pulverized for easy fabrication in the subsequent pressing step. The mixture to be pressed may be admixed with a suitable binder such as water, polyvinyl alcohol, etc.

It is advantageous that the sintered body have the opposite surfaces lapped by abrasive powder such as silicon carbide having a particle size of 300 mesh to 1,500 mesh.

The sintered bodies are coated at least on one of the opposite surfaces thereof by a silver electrode paint in a per se conventional manner such as by a spray method, screen printing method or brushing method. It is necessary that the silver electrode paint have a solid ingredient composition as defined in Table 2 after it is fired at 100 to 850 C. in air. Solid ingredients having compositions defined in Table 2 can be prepared in a per se conventional manner by mixing commercially available powders with organic resin such as epoxy, vinyl and phenyl resin in an organic solvent such as butyl acetate, toluene or the like so as to produce silver electrode paints.

The silver powder may be in the form of metallic silver, or in the form of silver carbonate or silver oxide, or in any other form which in firing at the temperatures employed will be converted to metallic silver. Therefore, the term silver" as used throughout this specification and the claims appended hereto in connection with the silver composition before it is fired, is meant to include silver in any form which during firing will be converted to metallic silver. The viscosity of the resultant silver electrode paints can be controlled by the amounts of resin and solvent. Particle sizes of solid ingredients also are required to be in the range of 0.1 p. to 5 11-.

Lead wires can be applied to the silver 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 organic solvent for connecting the lead wires to the silver electrodes.

Voltage dependent resistors according to this invention have a high stability with respect to temperature and in a 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 greatly after heating cycles and the load life test. It is preferable for achieving a high stability with respect to humidity that the resultant voltage dependent resistors be embedded in a humidity proof resin such as epoxy resin and phenol resin in a per se well known manner.

According to the invention, it has been discovered that the method of curing the applied silver electrode paint has'a great effect on the n-value of the resultant voltage dependent resistors. The n-value will not be optimal when the applied silver electrode paint is heated in a non-oxidizing atmosphere such as nitrogen and hydrogen for curing. It is necessary for obtaining a high n-value that the applied silver electrode paint be cured by heating in an oxidizing atmosphere such as air and oxygen.

Silver electrodes prepared by any other method than by silver painting result in a poor n-value. For example, the sintered body does not become a voltage dependent resistor when it is provided with silver electrodes on the opposite surfaces by electroless plating on electrolytic plating in a conventional manner. Silver electrodes prepared by vacuum evaporation or chemical deposition result in an n-value less than 3. i The following examples are given as illustrative of the presently preferred method of proceeding accord ing to the present invention; however, it is not intended that the scope of said invention be limited to the specific examples.

EXAMPLE 1 Respective starting materials according to Table 3 are mixed in a wet mill for 5 hours.

The mixture is dried and pressed in a mold into disc of 13 mm diameter and 2.5mm thickness at a pressure of 340 kg/cm.

Each pressed body is sintered in air at l,350 C. for 1 hour, and then quenched to room temperature (about 15 to about 30 C). Eachsintered disc is lapped at the opposite surfaces thereof lapped by silicon carbide having a particle size of 600 mesh. The resulting sintered disc has a size of 10 mm diameter and 1.5 mm thickness. Each sintered disc is coated on the opposite surfaces thereof with a silver electrode paint by a conventional brushing method. The silver electrode paint employed has a solid ingredient composition according to Table 4 and is prepared by mixing these ingredients with vinyl resin in amyl acetate. Each coated disc is fired at 800 C. for 30 minutes in air.

Claims (9)

  1. 2. A voltage dependent resistor as claimed in claim 1, wherein said at least one of electrodes consists of a silver paint electrode which is in non-ohmic contact with said body.
  2. 3. A voltage dependent resistor as claimed in claim 2, wherein said additive consists essentially of 1.0 to 8.0 mole percent of beryllium oxide (BeO).
  3. 4. A voltage dependent resistor as claimed in claim 3, wherein said additive further includes at least one member selected from the group consisting of 0.1 to 3.0 mole percent of nickel oxide (NiO) and 0.1 to 3.0 mole percent of titanium oxide (TiO2).
  4. 5. A voltage dependent resistor according to claim 3, wherein said additive further includes 0.1 to 3.0 mole percent of nickel oxide (NiO), 0.1 to 3.0 mole percent of titanium oxide TiO2) and 0.02 to 1.0 mole percent of barium oxide (BaO).
  5. 6. A voltage dependent resistor according to claim 3, wherein said additive further includes 0.1 to 3.0 mole percent of nickel oxide (NiO), 0.1 to 3.0 mole percent of titanium oxide (TiO2), 0.02 to 1.0 mole percent of barium oxide (BaO) and 0.1 to 3.0 mole percent of stannic oxide (SnO2).
  6. 7. A voltage dependent resistor according to claim 3, wherein said additive further includes 0.1 to 3.0 mole percent of nickel oxide (NiO), 0.1 to 3.0 mole percent of aluminum oxide (Al2O3), 0.1 to 3.0 mole percent of lead oxide (PbO) and 0.1 to 3.0 mole percent of cadmium fluoride (CdF2).
  7. 8. A voltage dependent resistor according to claim 3, wherein said additive further includes 0.1 to 3.0 mole percent of thallium oxide (Tl2O3) and 0.1 to 3.0 mole percent of titanium oxide (TiO2).
  8. 9. A voltage dependent resistor according to claim 2, wherein said silver electrode has a composition comprising 70 to 99.5 percent by weight of silver, 0.3 to 27 percent by weight of bismuth oxide (Bi2O3), 0.1 to 15 percent by weight of silicon dioxide (SiO2) and 0.1 to 15 percent by weight of boron trioxide (B2O3).
  9. 10. A voltage dependent resistor according to claim 2, wherein said silver electrode has a composition comprising 70 to 99.45 percent by weight of silver, 0.3 to 27 percent by weight of bismuth oxide (Bi2O3), 0.1 to 15 percent by weight of silicon dioxide (SiO2), 0.1 to 15 percent by weight of boron trioxide (B2O3) and 0.05 to 6.0 percent by weight of cobalt oxide (CoO).
US3689863A 1969-12-08 1970-11-24 Voltage dependent resistors in a surface barrier type Expired - Lifetime US3689863A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP9878969 1969-12-08
JP2990870A JPS5031636B1 (en) 1970-04-06 1970-04-06

Publications (1)

Publication Number Publication Date
US3689863A true US3689863A (en) 1972-09-05

Family

ID=26368160

Family Applications (1)

Application Number Title Priority Date Filing Date
US3689863A Expired - Lifetime US3689863A (en) 1969-12-08 1970-11-24 Voltage dependent resistors in a surface barrier type

Country Status (5)

Country Link
US (1) US3689863A (en)
DE (1) DE2061670C3 (en)
FR (1) FR2072991A5 (en)
GB (1) GB1330010A (en)
NL (1) NL7017694A (en)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3795048A (en) * 1972-02-16 1974-03-05 Mitsubishi Mining & Cement Co Method for manufacturing non-linear resistors
US3805022A (en) * 1972-10-10 1974-04-16 Texas Instruments Inc Semiconducting threshold heaters
US3916366A (en) * 1974-10-25 1975-10-28 Dale Electronics Thick film varistor and method of making the same
US4081764A (en) * 1972-10-12 1978-03-28 Minnesota Mining And Manufacturing Company Zinc oxide light emitting diode
US4094061A (en) * 1975-11-12 1978-06-13 Westinghouse Electric Corp. Method of producing homogeneous sintered ZnO non-linear resistors
US4383237A (en) * 1980-05-07 1983-05-10 Matsushita Electric Industrial Co., Ltd. Voltage-dependent resistor
US4400683A (en) * 1981-09-18 1983-08-23 Matsushita Electric Industrial Co., Ltd. Voltage-dependent resistor
US4538347A (en) * 1984-06-18 1985-09-03 Gte Laboratories Incorporated Method for making a varistor package
WO1996035218A2 (en) * 1995-05-03 1996-11-07 Philips Electronics N.V. Degaussing unit comprising one or two thermistors
US20030010960A1 (en) * 2001-07-02 2003-01-16 Felix Greuter Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound
US20100173878A1 (en) * 2006-06-06 2010-07-08 Intra-Cellular Therapies, Inc. Organic compounds
US20100273753A1 (en) * 2007-12-06 2010-10-28 Peng Li Organic compounds
US8697710B2 (en) 2008-12-06 2014-04-15 Intra-Cellular Therapies, Inc. Optionally substituted 3-amino-4-(thioxo or imino)-4,5-dihydro-2H-pyrazolo [3,4-d]pyrimidin-6(7H)-ones
US8859564B2 (en) 2008-12-06 2014-10-14 Intra-Cellular Therapies, Inc. Pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione derivatives useful as inhibitors of phosphodiesterase 1
US8927556B2 (en) 2008-12-06 2015-01-06 Intra-Cellular Therapies, Inc. 1H-pyrrolo[3,4-D]pyrimidin-2(6H)-one compounds
US9371327B2 (en) 2010-05-31 2016-06-21 Intra-Cellular Therapies, Inc. PDE1 inhibitor compounds
US9434730B2 (en) 2010-05-31 2016-09-06 Intra-Cellular Therapies, Inc. PDE1 inhibitor compounds
US9546175B2 (en) 2014-08-07 2017-01-17 Intra-Cellular Therapies, Inc. Organic compounds

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2820118C2 (en) * 1977-06-23 1985-04-11 Kombinat Veb Keramische Werke Hermsdorf, Ddr 6530 Hermsdorf, Dd

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3570002A (en) * 1967-04-26 1971-03-09 Matsushita Electric Ind Co Ltd Non-linear resistor of sintered zinc oxide
US3611073A (en) * 1968-12-02 1971-10-05 Matsushita Electric Ind Co Ltd Diode comprising zinc oxide doped with gallium oxide used as a voltage variable resistor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3570002A (en) * 1967-04-26 1971-03-09 Matsushita Electric Ind Co Ltd Non-linear resistor of sintered zinc oxide
US3611073A (en) * 1968-12-02 1971-10-05 Matsushita Electric Ind Co Ltd Diode comprising zinc oxide doped with gallium oxide used as a voltage variable resistor

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3795048A (en) * 1972-02-16 1974-03-05 Mitsubishi Mining & Cement Co Method for manufacturing non-linear resistors
US3805022A (en) * 1972-10-10 1974-04-16 Texas Instruments Inc Semiconducting threshold heaters
DE2349485A1 (en) * 1972-10-10 1974-04-25 Texas Instruments Inc heater
US4081764A (en) * 1972-10-12 1978-03-28 Minnesota Mining And Manufacturing Company Zinc oxide light emitting diode
US3916366A (en) * 1974-10-25 1975-10-28 Dale Electronics Thick film varistor and method of making the same
US4094061A (en) * 1975-11-12 1978-06-13 Westinghouse Electric Corp. Method of producing homogeneous sintered ZnO non-linear resistors
US4383237A (en) * 1980-05-07 1983-05-10 Matsushita Electric Industrial Co., Ltd. Voltage-dependent resistor
US4400683A (en) * 1981-09-18 1983-08-23 Matsushita Electric Industrial Co., Ltd. Voltage-dependent resistor
US4538347A (en) * 1984-06-18 1985-09-03 Gte Laboratories Incorporated Method for making a varistor package
WO1996035218A2 (en) * 1995-05-03 1996-11-07 Philips Electronics N.V. Degaussing unit comprising one or two thermistors
WO1996035218A3 (en) * 1995-05-03 1997-01-09 Philips Electronics Nv Degaussing unit comprising one or two thermistors
US20030010960A1 (en) * 2001-07-02 2003-01-16 Felix Greuter Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound
US7320762B2 (en) * 2001-07-02 2008-01-22 Abb Schweiz Ag Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound
US7618550B2 (en) 2001-07-02 2009-11-17 Abb Research Ltd Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound
US20080023678A1 (en) * 2001-07-02 2008-01-31 Abb Research Ltd. Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound
US20100173878A1 (en) * 2006-06-06 2010-07-08 Intra-Cellular Therapies, Inc. Organic compounds
US9255099B2 (en) 2006-06-06 2016-02-09 Intra-Cellular Therapies, Inc. Pyrazolo[3,4-D]pyrimidine-4,6(5H,7H)-diones as phosphodiesterase 1 inhibitors
US20100273753A1 (en) * 2007-12-06 2010-10-28 Peng Li Organic compounds
US8846693B2 (en) 2007-12-06 2014-09-30 Intra-Cellular Therapies, Inc. Optionally substituted pyrazolo[3,4-d]pyrimidine-4,6-diones
US8697710B2 (en) 2008-12-06 2014-04-15 Intra-Cellular Therapies, Inc. Optionally substituted 3-amino-4-(thioxo or imino)-4,5-dihydro-2H-pyrazolo [3,4-d]pyrimidin-6(7H)-ones
US8859564B2 (en) 2008-12-06 2014-10-14 Intra-Cellular Therapies, Inc. Pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione derivatives useful as inhibitors of phosphodiesterase 1
US8927556B2 (en) 2008-12-06 2015-01-06 Intra-Cellular Therapies, Inc. 1H-pyrrolo[3,4-D]pyrimidin-2(6H)-one compounds
US9487527B2 (en) 2008-12-06 2016-11-08 Intra-Cellular Therapies, Inc. Pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-dione derivatives useful as inhibitors of phosphodiesterase I
US9371327B2 (en) 2010-05-31 2016-06-21 Intra-Cellular Therapies, Inc. PDE1 inhibitor compounds
US9434730B2 (en) 2010-05-31 2016-09-06 Intra-Cellular Therapies, Inc. PDE1 inhibitor compounds
US9546175B2 (en) 2014-08-07 2017-01-17 Intra-Cellular Therapies, Inc. Organic compounds

Also Published As

Publication number Publication date Type
DE2061670B2 (en) 1974-05-22 application
FR2072991A5 (en) 1971-09-24 application
GB1330010A (en) 1973-09-12 application
NL7017694A (en) 1971-06-10 application
DE2061670C3 (en) 1975-01-16 grant
DE2061670A1 (en) 1971-09-16 application

Similar Documents

Publication Publication Date Title
US3484284A (en) Electroconductive composition and method
US4729058A (en) Self-limiting capacitor formed using a plurality of thin film semiconductor ceramic layers
US4506285A (en) Substrate made of varistor material having a plurality of electronic components mounted thereon
US2950996A (en) Electrical resistance material and method of making same
US4015230A (en) Humidity sensitive ceramic resistor
US4910389A (en) Conductive polymer compositions
US4980541A (en) Conductive polymer composition
US4046847A (en) Process for improving the stability of sintered zinc oxide varistors
US5369390A (en) Multilayer ZnO varistor
US4140937A (en) Direct current electroluminescent devices
US3553109A (en) Resistor compositions containing pyrochlore-related oxides and noble metal
US5235310A (en) Varistor having interleaved electrodes
US3573229A (en) Cermet resistor composition and method of making same
US4041436A (en) Cermet varistors
US3933668A (en) Intergranular insulation type polycrystalline ceramic semiconductive composition
US3902102A (en) Ceramic capacitor with base metal electrodes
US7320762B2 (en) Polymer compound with nonlinear current-voltage characteristic and process for producing a polymer compound
US2924540A (en) Ceramic composition and article
US3663458A (en) Nonlinear resistors of bulk type
US4286251A (en) Vitreous enamel resistor and method of making the same
US3928242A (en) Metal oxide varistor with discrete bodies of metallic material therein and method for the manufacture thereof
US2950995A (en) Electrical resistance element
US4296002A (en) Metal oxide varistor manufacture
US4675644A (en) Voltage-dependent resistor
US4290041A (en) Voltage dependent nonlinear resistor