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US4606116A
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Non-linear resistor and method of manufacturing the same
Assignee: US Philips Corp
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Filing: 1985-07-11
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Granted: 1986-08-19
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Expires: 2005-07-11
Abstract
Abstract A non-linear resistor having an operational field strength which optionally is formed as a VDR- or as an NTC-resistor having a ceramic sintered body on the basis of a polycrystalline alkaline earth metal titanate doped with a small quantity of a metal oxide so as to produce an N-type conductivity, in which the sintered body comprises at its grain boundaries insulating layers formed by re-oxidation of the sintered body and consists of an alkaline earth metal titanate having a Perowskite structure of the general formula (A.sub.1-x Ln.sub.x)TiO.sub.3.yTiO.sub.2 or A(Ti.sub.1-x Me x )O 3 .yTio 2 , wherein: A=alkaline earth metal; Ln=rare earth metal; Me=metal having a valency of 5 or more; 0.0005<x<solubility limit in the Perowskite phase; y=0.001 to 0.02. The sintered body becomes adjustable in its non-linear resistance variation by selection of the re-oxidation temperature and of the re-oxidation duration in such manner that an initially present NTC-characteristic gradually is observable only at ever increasing temperatures and changes into a VDR-characteristic in the range of the operating temperature of the resistor. FIG. 1.
Inventors
- 👤 Detlev Hennings
- 👤 Axel Schnell
- 👤 Herbert Schreinemacher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 17:31
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/46; C04B35/462; C04B35/465; C04B35/47; C01; C01G; C01G23/00; C01G23/003; C01G23/006; C04B35/622; C04B35/626; C04B35/62605; C04B35/6261; C04B35/6262; C04B35/62645; C04B35/62675; C04B35/63; C04B35/632; C04B35/634; C04B35/63404; C04B35/63416; H; H01; H01C; H01C7/00; H01C7/10; H01C7/105; H01C7/108; H01C7/115; C01P; C01P2002/00; C01P2002/50; C01P2002/52; C01P2002/54; C04B2235/00; C04B2235/02; C04B2235/30; C04B2235/32; C04B2235/3224; C04B2235/3227; C04B2235/3231; C04B2235/3232; C04B2235/3251; C04B2235/3258; C04B2235/65; C04B2235/656; C04B2235/6567; C04B2235/658; C04B2235/6582; C04B2235/6588; C04B2235/66; C04B2235/661; C04B2235/662; C04B2235/663; C04B2235/70; C04B2235/74; C04B2235/76; C04B2235/768; C04B2235/78; C04B2235/786; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49085
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
207 words
A method of manufacturing a non-linear resistor having a ceramic sintered body consisting of a polycrystalline alkaline titanate doped to n-type conductance with a metal oxide and which body has a Perowskite structure, consists of an alkaline earth metal titanate containing excess TiO 2 , has a formula selected from the group consisting of (Sr 1-x Ln x )TiO 3 .yTiO 2 and Sr(Ti 1-x Me x )O 3 .yTiO 2 wherein Ln is a rare earth metal, Me is a metal having a valence of at least 5, 0.0005<x<solubility limit of the Ln in the Perowskite phase and y=0.001 to 0.02, which sintered body is provided on its grain boundaries with insulating layers produced by re-oxidation, characterized in that the ceramic body is first sintered in a reducing atmosphere and that said sintered body is then re-oxidized in an oxidizing atmosphere, preferably in air, in which the sintered body becomes adjustable in its non-linear resistance variation by a selection of the re-oxidation temperature and the duration of the re-oxidation in such manner that an initially present NTC-characteristic is observable as a function of the oxidation state gradually only at increasing temperatures and in the range of the operating temperature of the resistor changes into a VDR-characteristic.
Claim 2
Independent Claim
207 words
A method of manufacturing a non-linear resistor having a ceramic sintered body consisting of a polycrystalline alkaline titanate doped to n-type conductance with a metal oxide and which body has a Perowskite structure, consists of an alkaline earth metal titanate containing excess TiO 2 , has a formula selected from the group consisting of (Sr 1-x Ln x )TiO 3 .yTiO 2 and Sr(Ti 1-x Me x )O 3 .yTiO 2 wherein Ln is a rare earth metal, Me is a metal having a valence of at least 5, 0.0005<x<solubility limit of the Ln in the Perowskite phase and y=0.001 to 0.02, which sintered body is provided on its grain boundaries with insulating layers produced by re-oxidation, characterized in that the ceramic body is first sintered in a reducing atmosphere and that said sintered body is then re-oxidized in an oxidizing atmosphere, preferably in air, in which the sintered body becomes adjustable in its non-linear resistance variation by a selection of the re-oxidation temperature and the duration of the re-oxidation in such manner that an initially present NTC-characteristic is observable as a function of the oxidation state gradually only at increasing temperatures and in the range of the operating temperature of the resistor changes into a VDR-characteristic.
Claim 3
Dependent Claim
226 words
A method as claimed in claim 1, characterized by the following operational steps: (a) grinding a mixture of the starting substances for an alkaline earth metal titanate having a Perowskite structure with an addition of a metal oxide having a doping function so as to produce an N-type conductivity and having a composition defined by one of the formulae (A.sub.1-x Ln.sub.x)TiO.sub.3.yTiO.sub.2 or A(Ti.sub.1-x Me.sub.x)O.sub.3.yTiO.sub.2 wherein: A=alkaline earth metal Ln=rare earth metal including yttrium Me=metal having a valency of 5 or more 0.0005<x<solubility limit in the Perowskite phase y=0.001 to 0.02; (b) pre-sintering the ground product formed by step (a) in a temperature range of 1050° to 1350° C. for 2 to 20 hours in air; (c) grinding and granulating the pre-sintered product formed by step (b) with a suitable binder; (d) compressing the granulated product formed by step (c) to form a moulded body suitable for a resistor; (e) sintering the moulded body formed by step (d) in a reducing atmosphere at a temperature in the range of 1400° to 1500° C. for 1 to 10 hours; (f) re-oxidizing the sintered body formed by step (e) in an oxidizing atmosphere, preferably in air, at a temperature in the range from 900° to 1300° C. for 5 to 240 minutes; (g) providing metal electrodes on oppositely located surfaces of the re-oxidized sintered body formed by step (f).
Claim 4
Dependent Claim
71 words
A method as claimed in claim 2, characterized in that the alkaline earth metal titanate is formed by conversion of SrCO 3 with TiO 2 in the molar ratio from 1:1.001 to 1:1.02 by adding the doping metals in the form of their oxides in a quantity from 0.05 to maximum 60 mol% of the constituent to be substituted after grinding and pre-sintering at 1150° C. in air for 15 hours.
Claim 5
Dependent Claim
21 words
A method as claimed in claim 2, characterized in that La 2 O 3 is used as a doping metal oxide.
Claim 6
Dependent Claim
21 words
A method as claimed in claim 2, characterized in that Nb 2 O 5 is used as a doping metal oxide.
Claim 7
Dependent Claim
19 words
A method as claimed in claim 2, characterized in that WO 3 is used as a doping metal oxide.
Claim 8
Dependent Claim
21 words
A method as claimed in claim 2, characterized in that a 10% aqueous polyvinyl alcohol solution is used as a binder.
Claim 9
Dependent Claim
53 words
A method as claimed in claim 2, characterized in that the moulded body formed by step (d) is sintered at a temperature of 1460° C. in a reducing atmosphere consisting of water vapour-saturated mixed gas consisting of 90% by volume of N 2 and 10% by volume of H 2 for 4 hours.
Claim 10
Dependent Claim
22 words
A method as claimed in claim 8, characterized in that the mixed gas is saturated with H 2 O at ≈25° C.
Claim 11
Dependent Claim
53 words
A method as claimed in claim 2, characterized in that the sintered body formed by step (e) is re-oxidized in air at a temperature of at most 1200° C. for 30 minutes so as to maintain its NTC-characteristic in the operating temperature range about room temperature dependent on the nature of its doping.
Claim 12
Dependent Claim
49 words
A method as claimed in claim 2, characterized in that the sintered body formed by step (e) is re-oxidised in air at a temperature of 1100° C. for at least 5 minutes so as to obtain a VDR-characteristic at the operating temperature, dependent on the nature of its doping.
Claim 13
Dependent Claim
44 words
A method as claimed in claim 10, characterized in that for a resistor having NTC-characteristic a sintered body is chosen of the composition (Sr 0 .99 La 0 .01)TiO 3 .0.01TiO 2 which is re-oxidized at a temperature of 1100° C. for 30 minutes.
Claim 14
Dependent Claim
44 words
A method as claimed in claim 11, characterized in that for a resistor having VDR-characteristic a sintered body of the composition Sr(Ti 0 .996 W 0 .004)O 3 .0.01TiO 2 is chosen which is re-oxidized at a temperature of 1100° C. for 60 minutes.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-08-18 | 1990-02-17 | 1990-08-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-18 | 1994-02-17 | 1994-08-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-18 | 1998-02-17 | 1998-08-19 | $7700.00 | Window Closed / Lapsed |