US4495482A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Metal oxide varistor with controllable breakdown voltage and capacitance and method of making
Assignee: General Electric Co
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Filing: 1983-06-16
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Granted: 1985-01-22
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Expires: 2003-06-16
Abstract
Abstract A metal oxide varistor with controllable breakdown voltage and capacitance characteristics is fabricated by controlled diffusion of lithium into conventional metal oxide varistor material at elevated temperature. The varistor layer containing lithium exhibits an increased breakdown voltage, lowered capacitance, and low leakage current while maintaining a high coefficient of nonlinearity.
Inventors
- 👤 Herbert R. Philipp
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 19:55
CPC Classifications
H; H01; H01C; H01C7/00; H01C7/10; H01C7/105; H01C7/108; H01C7/112; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49101
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
159 words
A method for controlling the intrinsic capacitance and breakdown voltage of a body of sintered zinc oxide based varistor material, said body possessing at least two substantially planar, parallel surfaces for electrode attachment, said body nonetheless retaining the nonohmic voltage-current properties of said varistor material, said method comprising: diffusing lithium into the bulk of said varistor material by applying, to at least one of said parallel planar surfaces of said varistor body, a composition containing lithium such that the lithium concentration thereon is less than 2 mg/cm 2 , and then heating said varistor material at elevated temperatures for a time sufficient to cause diffusion of at least a portion of said lithium into said varistor body, whereby the intrinsic capacitance of said varistor material decreases and the breakdown voltage of said varistor body increases as the concentration of diffused lithium therein increases; and attaching at least one electrode to said planar surface having said lithium composition applied thereto.
Claim 2
Independent Claim
159 words
A method for controlling the intrinsic capacitance and breakdown voltage of a body of sintered zinc oxide based varistor material, said body possessing at least two substantially planar, parallel surfaces for electrode attachment, said body nonetheless retaining the nonohmic voltage-current properties of said varistor material, said method comprising: diffusing lithium into the bulk of said varistor material by applying, to at least one of said parallel planar surfaces of said varistor body, a composition containing lithium such that the lithium concentration thereon is less than 2 mg/cm 2 , and then heating said varistor material at elevated temperatures for a time sufficient to cause diffusion of at least a portion of said lithium into said varistor body, whereby the intrinsic capacitance of said varistor material decreases and the breakdown voltage of said varistor body increases as the concentration of diffused lithium therein increases; and attaching at least one electrode to said planar surface having said lithium composition applied thereto.
Claim 3
Dependent Claim
28 words
The method of claim 1 wherein said composition comprises a solution of at least one compound selected from the group consisting of LiNO 3 and Li 2 O.
Claim 4
Dependent Claim
22 words
The method of claim 2 further comprising the step of evaporating the solvent in said solution prior to said step of heating.
Claim 5
Dependent Claim
27 words
The method of claim 1 wherein said step of heating comprises heating said varistor material in air at a temperature of between 500° C. and 1100° C.
Claim 6
Dependent Claim
61 words
The method of claim 4 wherein said varistor comprises a composition consisting essentially of 0.5 mole percent each of Bi 2 O 3 , Co 2 O 3 , MnO 2 , and SnO 2 , 0.1 mole percent each of H 3 BO 3 and BaCO 3 , 1 mole percent Sb 2 O 3 , the remainder being ZnO.
Claim 7
Dependent Claim
21 words
The method of claim 5 wherein said step of heating comprises heating said varistor material at 800° C. for one hour.
Claim 8
Dependent Claim
11 words
The varistor produced in accordance with the method of claim 1.
Claim 9
Dependent Claim
11 words
The varistor produced in accordance with the method of claim 4.
Claim 10
Dependent Claim
11 words
The varistor produced in accordance with the method of claim 5.
Claim 11
Independent Claim
141 words
A method for controlling the intrinsic capacitance of a body of sintered zinc oxide based varistor material, said body possessing at least two substantially planar, parallel surfaces for electrode attachment, said body nonetheless retaining the nonohmic voltage-current properties of said varistor material, said method comprising: diffusing lithium into the bulk of said varistor material by applying, to at least one of said parallel, planar surfaces of said varistor body, a composition consisting essentially of lithium as the active constituent, and then by heating said varistor material at elevated temperatures for a time sufficient to cause diffusion of at least a portion of said lithium into said varistor body, whereby the intrinsic capacitance of said varistor material decreases as the concentration of diffused lithium therein increases; and attaching at least one electrode to said planar surface having said lithium composition applied thereto.
Claim 12
Independent Claim
141 words
A method for controlling the intrinsic capacitance of a body of sintered zinc oxide based varistor material, said body possessing at least two substantially planar, parallel surfaces for electrode attachment, said body nonetheless retaining the nonohmic voltage-current properties of said varistor material, said method comprising: diffusing lithium into the bulk of said varistor material by applying, to at least one of said parallel, planar surfaces of said varistor body, a composition consisting essentially of lithium as the active constituent, and then by heating said varistor material at elevated temperatures for a time sufficient to cause diffusion of at least a portion of said lithium into said varistor body, whereby the intrinsic capacitance of said varistor material decreases as the concentration of diffused lithium therein increases; and attaching at least one electrode to said planar surface having said lithium composition applied thereto.
Claim 13
Dependent Claim
28 words
The method of claim 10 wherein said composition comprises a solution of at least one compound selected from the group consisting of LiNO 3 and Li 2 O.
Claim 14
Dependent Claim
22 words
The method of claim 10 further comprising the step of evaporating the solvent in said solution prior to said step of heating.
Claim 15
Dependent Claim
23 words
The method of claim 10 wherein the surface concentration of lithium applied to said varistor material is less than 2 mg/cm 2 .
Claim 16
Dependent Claim
25 words
The method of claim 13 wherein said step of heating comprises heating said varistor material at a temperature of between 500° C. and 1100° C.
Claim 17
Dependent Claim
61 words
The method of claim 14 wherein said varistor comprises a composition consisting essentially of 0.5 mole percent each of Bi 2 O 3 , Co 2 O 3 , MnO 2 , and SnO 2 , 0.1 mole percent each of H 3 BO 3 and BaCO 3 , 1 mole percent Sb 2 O 3 , the remainder being ZnO.
Claim 18
Dependent Claim
21 words
The method of claim 15 wherein said step of heating comprises heating said varistor material at 800° C. for one hour.
Claim 19
Dependent Claim
11 words
The varistor produced in accordance with the method of claim 10.
Claim 20
Dependent Claim
11 words
The varistor produced in accordance with the method of claim 14.
Claim 21
Dependent Claim
11 words
The varistor produced in accordance with the method of claim 15.
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) | 1988-01-22 | 1988-07-23 | 1989-01-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-01-22 | 1992-07-23 | 1993-01-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-01-22 | 1996-07-23 | 1997-01-22 | $7700.00 | Window Closed / Lapsed |