EP1798741A1 - Current/voltage nonlinear resistor - Google Patents
Current/voltage nonlinear resistor Download PDFInfo
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- EP1798741A1 EP1798741A1 EP06025718A EP06025718A EP1798741A1 EP 1798741 A1 EP1798741 A1 EP 1798741A1 EP 06025718 A EP06025718 A EP 06025718A EP 06025718 A EP06025718 A EP 06025718A EP 1798741 A1 EP1798741 A1 EP 1798741A1
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- Prior art keywords
- current
- mol
- voltage nonlinear
- nonlinear resistor
- voltage
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- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims abstract description 53
- UPWOEMHINGJHOB-UHFFFAOYSA-N oxo(oxocobaltiooxy)cobalt Chemical compound O=[Co]O[Co]=O UPWOEMHINGJHOB-UHFFFAOYSA-N 0.000 claims abstract description 46
- WMWLMWRWZQELOS-UHFFFAOYSA-N bismuth(iii) oxide Chemical compound O=[Bi]O[Bi]=O WMWLMWRWZQELOS-UHFFFAOYSA-N 0.000 claims abstract description 41
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052733 gallium Inorganic materials 0.000 claims abstract description 15
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000011572 manganese Substances 0.000 claims abstract description 12
- GHPGOEFPKIHBNM-UHFFFAOYSA-N antimony(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Sb+3].[Sb+3] GHPGOEFPKIHBNM-UHFFFAOYSA-N 0.000 claims abstract description 10
- VASIZKWUTCETSD-UHFFFAOYSA-N manganese(II) oxide Inorganic materials [Mn]=O VASIZKWUTCETSD-UHFFFAOYSA-N 0.000 claims abstract description 10
- GNRSAWUEBMWBQH-UHFFFAOYSA-N nickel(II) oxide Inorganic materials [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052761 rare earth metal Inorganic materials 0.000 claims abstract description 7
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052787 antimony Inorganic materials 0.000 claims abstract description 6
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052797 bismuth Inorganic materials 0.000 claims abstract description 6
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 6
- 239000010941 cobalt Substances 0.000 claims abstract description 6
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 6
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 6
- ADCOVFLJGNWWNZ-UHFFFAOYSA-N antimony trioxide Inorganic materials O=[Sb]O[Sb]=O ADCOVFLJGNWWNZ-UHFFFAOYSA-N 0.000 claims description 13
- YEAUATLBSVJFOY-UHFFFAOYSA-N tetraantimony hexaoxide Chemical compound O1[Sb](O2)O[Sb]3O[Sb]1O[Sb]2O3 YEAUATLBSVJFOY-UHFFFAOYSA-N 0.000 claims description 9
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 8
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 8
- 229910052796 boron Inorganic materials 0.000 claims description 8
- 239000002994 raw material Substances 0.000 claims description 8
- 229910052709 silver Inorganic materials 0.000 claims description 8
- 239000004332 silver Substances 0.000 claims description 8
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 4
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 4
- 229910052691 Erbium Inorganic materials 0.000 claims description 3
- 229910052693 Europium Inorganic materials 0.000 claims description 3
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 3
- 229910052689 Holmium Inorganic materials 0.000 claims description 3
- 229910052775 Thulium Inorganic materials 0.000 claims description 3
- 229910052769 Ytterbium Inorganic materials 0.000 claims description 3
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 3
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 claims description 3
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims description 3
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 claims description 3
- FRNOGLGSGLTDKL-UHFFFAOYSA-N thulium atom Chemical compound [Tm] FRNOGLGSGLTDKL-UHFFFAOYSA-N 0.000 claims description 3
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 claims description 3
- 229910052727 yttrium Inorganic materials 0.000 claims description 3
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 3
- 239000000523 sample Substances 0.000 description 39
- 239000011787 zinc oxide Substances 0.000 description 20
- 239000000203 mixture Substances 0.000 description 16
- 238000000034 method Methods 0.000 description 15
- 230000000694 effects Effects 0.000 description 13
- 239000002245 particle Substances 0.000 description 12
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(III) oxide Inorganic materials O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 description 11
- 229910002651 NO3 Inorganic materials 0.000 description 8
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 238000011156 evaluation Methods 0.000 description 7
- 229910000108 silver(I,III) oxide Inorganic materials 0.000 description 7
- 229910052596 spinel Inorganic materials 0.000 description 7
- 239000011029 spinel Substances 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000006104 solid solution Substances 0.000 description 6
- 230000005540 biological transmission Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- 239000013078 crystal Substances 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- CHPZKNULDCNCBW-UHFFFAOYSA-N gallium nitrate Chemical compound [Ga+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O CHPZKNULDCNCBW-UHFFFAOYSA-N 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- AJNVQOSZGJRYEI-UHFFFAOYSA-N digallium;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Ga+3] AJNVQOSZGJRYEI-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- -1 gallium ions Chemical class 0.000 description 1
- 229940044658 gallium nitrate Drugs 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
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
-
- 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
Definitions
- the present invention relates to a current/voltage nonlinear resistor whose main component is zinc oxide (ZnO), and more particularly relates to a current/voltage nonlinear resistor in which improvements have been made to the composition of sub-components contained in the main component.
- ZnO zinc oxide
- Overvoltage protection devices such as lightning arrestors and surge absorbers are commonly incorporated into power systems or electronic device circuitry. The purpose of these devices is to protect the power system or electronic device circuitry by removing any overvoltage that has been superimposed over the normal voltage.
- Current/voltage nonlinear resistors are frequently used for these overvoltage protection devices.
- a current/voltage nonlinear resistor is a resistor with the property of exhibiting substantially insulating characteristics at ordinary voltage, but exhibiting low resistance when overvoltage is applied.
- a current/voltage nonlinear resistor is a ceramic element whose main component is zinc oxide (ZnO), and the following characteristics are required of such resistors.
- the resistor must have nonlinear resistance characteristics, meaning that the resistance value varies greatly with changes in voltage, but also needs to have a long enough service life that no deterioration occurs when voltage is continuously applied over an extended period, energy capability characteristics that allow it to absorb lightning surges and switching surges without damage, and so forth.
- current/voltage nonlinear resistors are seen to have a property whereby the resistance value drops when the temperature is higher. Consequently, thermal stability with respect to high temperature is also required.
- the procedure for producing a current/voltage nonlinear resistor will now be described (see Japanese Patent Publication H4-25681 ).
- the raw materials of the current/voltage nonlinear resistor are such that zinc oxide (ZnO) is the main component, and Bi 2 O 3 , Co 2 O 3 , MnO, Sb 2 O 3 , and NiO are added as sub-components.
- These raw materials are thoroughly mixed along with water and a binder, then granulated with a spray dryer or the like, and these granules are molded and sintered to obtained a sinter.
- the side faces of the sinter are coated with an insulating substance for preventing surface flashover, and this coating is heat treated to form a side face insulating layer.
- a current/voltage nonlinear resistor is produced by polishing the two end faces of the sinter and forming electrodes.
- a rare earth oxide is added to a current/voltage nonlinear resistor whose main component is zinc oxide (ZnO) and whose sub-components are Bi 2 O 3 , Co 2 O 3 , MnO, Sb 2 O 3 and so forth, the result of which is that the resistance value is raised and characteristics are enhanced.
- ZnO zinc oxide
- a reduction in the size of power transmission and conversion devices extends to reducing the size of a lightning arrestor, of course, and the following problems have been indicated when the resistance of a current/voltage nonlinear resistor was raised due to making a lightning arrestor more compact. Because the amount of surge energy absorbed increases proportionally as the resistance of a current/ voltage nonlinear resistor is raised, the heating temperature is also raised by joule heat of the current/voltage nonlinear resistor when surge energy is absorbed.
- a current/voltage nonlinear resistor has a property whereby its resistance decreases as the temperature rises, if the temperature is too high, a drop in resistance occurs and there is greater current leakage. That is, since the decrease in the resistance of a current/voltage nonlinear resistor with increased resistance is greater when the temperature is raised, it has been indicated that there is a problem with thermal stability.
- the present invention was proposed in light of these problems, and it is an object thereof to provide a current/voltage nonlinear resistor with which the resistance value, nonlinear resistance characteristics, and thermal stability can be improved by specifying the compositional range of sub-components, and the size of a lightning arrestor can be reduced.
- the present invention was conceived in an effort to achieve the stated object, and is characterized in that zinc oxide (ZnO) is the main component and bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element (R) are contained as sub-components in proportions, calculated as Bi 2 O 3 , Co 2 O 3 , MnO, Sb 2 O 3 , NiO, Ga 3+ , and R 2 O 3 , of 0.3 to 1.5 mol% Bi 2 O 3 , 0.3 to 2.0 mol% Co 2 O 3 , 0.4 to 3.0 mol% MnO, 0.5 to 4.0 mol% Sb 2 O 3 , 0.5 to 4.0 mol% NiO, 0.0005 to 0.02 mol% Ga 3+ , and 0.05 to 1.0 mol% R 2 O 3 .
- ZnO zinc oxide
- Bi bismuth
- Co cobalt
- Mn manganese
- the reason for specifying the sub-components to the above compositional ranges is that the inventors conducted various research into the compositions of current/voltage nonlinear resistors in an effort to achieved the above object, and as a result learned that keeping the proportions within the above ranges yields good resistance, nonlinear resistance characteristics, and thermal stability, and conversely that the above characteristics suffer when the proportions are outside the above ranges. Specifically, if the compositional proportions of the sub-components are kept within the above ranges, high resistance can be ensured and the nonlinear resistance characteristics and thermal stability are improved, and this makes it possible to attain the high level of characteristics required at the current time.
- the present invention provides a current/voltage nonlinear resistor with which the sub-components, namely, bismuth. (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element '(R), are contained in the compositional proportion ranges given above, and this affords excellent resistance, nonlinear resistance characteristics, and thermal stability, which in turn allows a current/voltage nonlinear resistor to be provided that can contribute to making lightning arrestors smaller.
- the sub-components namely, bismuth. (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element '(R)
- Tables 1 to 5 show evaluation indicators and contained amounts of current/voltage nonlinear resistors produced with varying amounts of sub-components contained.
- those marked with an asterisk have sub-components that are outside the compositional ranges pertaining to the present invention, and are comparative samples produced for the sake of comparison.
- those not marked with an asterisk meanwhile, have sub-components within the compositional ranges corresponding to the present invention.
- FIG. 1 is a cross section of the current/voltage nonlinear resistor pertaining to this embodiment.
- zinc oxide (ZnO) was used as the main component.
- Bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), and gallium (Ga), were used as sub-components, and the final amounts in which these were contained, calculated as Bi 2 0 3 , Co 2 O 3 , MnO, Sb 2 0 3 , NiO, and Ga 3+ were within the following ranges.
- the product contained 0.3 to 1.5 mol% Bi 2 0 3 , 0.3 to 2.0 mol% Co 2 O 3 , 0.4 to 3.0 mol% MnO, 0.5 to 4.0 mol% % Sb 2 0 3 , 0.5 to 4.0 mol% NiO, and 0.0005 to 0.02 mol% Ga 3+ .
- At least one type of rare earth oxide (R) selected from about dysprosium (Dy), europium (Eu), erbium (Er), thulium (Tm), gadolinium (Gd), yttrium (Y), holmium (Ho), and ytterbium (Yb) were contained in an amount of 0.05 to 1.0 mol%, calculated as R 2 O 3 .
- Bi 2 O 3 , Co 2 O 3 , MnO, Sb 2 O 3 , NiO, Dy 2 O 3 , and Ga 3+ or Al 3+ were measured out as sub-components in specific amounts with respect to the ZnO main component such that the amounts in which the components were contained in the current/voltage nonlinear resistors ultimately obtained were as indicated for sample numbers 1 to 44 in Tables 1 and 2.
- These raw materials were mixed in a mixer along with water and an organic binder, and each slurry was adjusted to a uniform consistency.
- the Ga 3+ or Al 3+ here was added as a nitrate aqueous solution.
- each of the slurries thus obtained was spray granulated in a spray dryer to produce a granulated powder with a grain size of about 100 ⁇ m.
- the granulated powder thus obtained was put in a metal mold and pressed into a disk with a diameter of 125 mm and a thickness of 30 mm, and this molded disk was heated to 500°C to remove the organic binder that had been added.
- the disk was fired for 2 hours at 1100°C to obtain the sinter 1 shown in FIG. 1.
- the side faces of the sinter 1 were coated with an inorganic insulating substance, and these coatings were heat treated to form side face insulating layers 2.
- the upper and lower end faces of the sinter 1 provided with the side face insulating layers 2 were polished to a specific thickness, after which electrodes 3 were thermal sprayed onto the polished faces of the sinter 1 to produce a current/voltage nonlinear resistor.
- the characteristics of the various current/voltage nonlinear resistors produced by the above procedure were evaluated as follows. First, the resistance of the current/voltage nonlinear resistor was evaluated by measuring the initial operating voltage of the current/voltage nonlinear resistor (the voltage when 1 mA of AC current was applied; V 1mA ). The higher the initial operating voltage, the fewer current/voltage nonlinear resistors that need to be stacked in a lightning arrestor, so this voltage is effective as an index for ascertaining how compact a lightning arrestor can be made.
- V 10kA The voltage when a 10 kA impulse current of 8 x 20 ⁇ s was applied (V 10kA ) was measured, and the ratio of this to the initial operating voltage V 1mA (V 10kA /V 1mA ) was evaluated as a nonlinearity coefficient. The smaller the value of this nonlinearity coefficient, the better the nonlinear resistance characteristics.
- the thermal stability of the current/voltage nonlinear resistor was evaluated by measuring the resistance leakage current when AC voltage that was 90% of the initial operating voltage was applied in a 200°C thermostatic tank. Specifically, the less leakage current at high temperature there is at 200°C, the better the thermal stability.
- the compositions of ten elements with each added component composition were measured, and the average thereof was used for the compositional value. The measurement results are given in Tables 1 and 2.
- the current/voltage nonlinear resistors with sample numbers not marked with an asterisk in Tables 1 and 2 were within the compositional ranges specified in the claims of the present invention, and therefore exhibited excellent results for initial operating voltage, nonlinearity coefficient, and leakage current at high temperature.
- the current/voltage nonlinear resistors pertaining to this embodiment can be considered to have high resistance and excellent nonlinear resistance characteristics and thermal stability.
- Bi 2 O 3 is a component that is present at the boundary of the zinc oxide (ZnO), which is the main component of the sinter, and is responsible for nonlinear resistance characteristics. The role of this component is to promote the growth of ZnO crystal grains. If we compare sample numbers 1 to 6 here, we see that when the amount of Bi 2 O 3 was less than 0.3 mol% (sample number 1), the material was in the liquid phase during sintering, and the amount of Bi 2 0 3 was inadequate to improve sintering.
- ZnO zinc oxide
- Sb 2 O 3 is a component that controls and makes uniform the growth of ZnO crystal grains during sintering by forming spinel (Zn 7 Sb 2 O 12 ) particles along with zinc oxide (ZnO). Its role is to improve nonlinear resistance characteristics and, at the same time, suppress the growth of ZnO crystal grains.
- sample numbers 3 and 7 to 12 A comparison of sample numbers 3 and 7 to 12 reveals that if the Sb 2 O 3 content is less than 0.5 mol% (sample number 7), there will be too few spinel particles capable of suppressing grain growth during sintering, so excellent characteristics cannot be obtained in terms of initial operating voltage and nonlinearity. If the amount of Sb 2 O 3 is over 4 mol% (sample number 12), however, it will act as an insulating component in the sinter, and there will be too many spinel particles, so excellent characteristics cannot be obtained in terms of nonlinearity and leakage current at high temperature.
- MnO is a component that primarily forms a solid solution with spinel particles and improves nonlinear resistance characteristics.
- a comparison of sample numbers 3 and 13 to 18 reveals that if the MnO content is less than 0.4 mol% (sample number 13), the electrical characteristics are unstable at the ZnO grain boundary, so excellent nonlinearity cannot be obtained. If the amount of MnO is over 3 mol% (sample number 18), however, here again it is impossible to obtain excellent nonlinearity characteristics.
- NiO is similar to MnO in that it primarily forms a solid solution with spinel particles and improves nonlinear resistance characteristics.
- a comparison of sample numbers 3 and 19 to 24 reveals that if the NiO content is less than 0.5 mol% (sample number 19), the very little NiO will form a solid solution with the spinel particles, so excellent initial operating voltage and nonlinearity cannot be obtained. If the amount of NiO is over 4 mol% (sample number 24), however, the electrical characteristics are unstable at the ZnO grain boundary, so excellent nonlinearity characteristics and leakage current at high temperature characteristics cannot be obtained.
- Co 2 O 3 also is a component that primarily forms a solid solution with spinel particles and improves nonlinear resistance characteristics.
- a comparison of sample numbers 3 and 25 to 30 reveals that if the Co 2 O 3 content is less than 0.3 mol% (sample number 25), the electrical characteristics are unstable at the ZnO grain boundary, so excellent nonlinearity cannot be obtained, but if the amount of Co 2 O 3 is over 2 mol% (sample number 30), here again the electrical characteristics are unstable at the ZnO grain boundary, making it impossible to obtain excellent nonlinearity characteristics or leakage current at high temperature characteristics.
- Ga 3+ serves to improve nonlinear resistance characteristics by forming a solid solution in the ZnO particles and lowering the electrical resistance of the ZnO particles.
- Aluminum (Al) has often been used in prior art as a component with a similar purpose, but improving nonlinear resistance characteristics by adding gallium gives a current/voltage nonlinear resistor with better thermal stability than by adding aluminum.
- sample numbers 3 and 31 to 38 A comparison of sample numbers 3 and 31 to 38 reveals that if the Ga 3+ content is less than 0.0005 mol% (sample number 31), not enough Ga 3+ will form a solid solution in the ZnO particles in the sinter, so the electrical resistance of the ZnO particles will be high and excellent nonlinearity cannot be obtained.
- Ga 3+ is over 0.02 mol% (sample number 37), however, the Ga 3+ will precipitate at the ZnO grain boundary and adversely affect the electrical characteristics of the ZnO grain boundary, so excellent nonlinearity cannot be obtained. Furthermore, compared to when Al 3+ is added (sample number 38), adding Ga 3+ allows better leakage current at high temperature characteristics to be obtained.
- sample numbers 3 and 39 to 44 A comparison of sample numbers 3 and 39 to 44 reveals that if the Dy 2 O 3 content is less than 0.3 mol% (sample number 39), there will not be enough Dy 2 O 3 to have the effect of suppressing grain growth, so excellent initial operating voltage and nonlinearity cannot be obtained. If the amount of Dy 2 O 3 is over 1.0 mol% (sample number 44), however, the electrical characteristics will be unstable at the ZnO grain boundary, making it impossible to obtain excellent characteristics in terms of nonlinearity or leakage current at high temperature.
- an oxide of dysprosium (Dy) was used as a rare earth oxide in this embodiment, but oxides of other rare earth elements, namely, europium (Eu), erbium (Er), thulium (Tm), gadolinium (Gd), yttrium (Y), holmium (Ho), and ytterbium (Yb), may also be used, and these will have the same effect as an oxide of dysprosium (Dy). Also, as long as the amount in which the various rare earth oxides are contained ends up being within a range of 0.05 to 1.0 mol%, the combination thereof may be selected as desired.
- zinc oxide (ZnO) is the main component and the final amounts of sub-components are within the ranges given above, which makes it possible to obtain a current/voltage nonlinear resistor that has high resistance and excellent thermal stability and nonlinear resistance characteristics. Accordingly, the number of stacked layers of current/voltage nonlinear resistor can be reduced while maintaining high reliability, and this contributes to making a lightning arrestor smaller.
- This embodiment is characterized by being composed of a sinter containing 0.005 to 0.05 wt% silver (Ag), calculated as Ag 2 O.
- Bi 2 O 3 (0.5 mol%), Co 2 O 3 (1.0 mol%), MnO (1.0 mol%), Sb 2 O 3 (2 mol%), NiO (2 mol%), Dy 2 O 3 (0.5 mol%), and Ga 3+ (0.003 mol% as a nitrate aqueous solution) were measured out as sub-components in the final proportions given in parentheses above, and these components were added to the ZnO main component.
- Ag 2 O was further added to this base composition so as to be contained in an amount of 0.001 to 0.1 wt%, and the current/voltage nonlinear resistors of sample numbers 45 to 50 shown in Table 3 were produced by the method described in the first embodiment above.
- the current/voltage nonlinear resistors of sample numbers 45 and 50 which are marked with an asterisk in Table 3, have compositions outside the scope of the claims of the present invention.
- the characteristics of the comparative samples indicate that the percentage change in leakage current is a positive value, and the service life characteristics are low.
- the added amount of silver, calculated as Ag 2 O was less than 0.005 wt%, there was no effect of improving service life characteristics.
- the amount was over 0.05 wt%, though, this had the opposite effect of causing the service life characteristics to deteriorate.
- adding silver in an amount of 0.005 to 0.05 wt%, calculated as Ag 2 O reduces the change over time in leakage current and improves the service life characteristics. Furthermore, in this embodiment, the effect of adding silver on the service life characteristics was only discussed for the base composition given in the Constitution and Production Procedure above, but the same effect will be obtained as long as the composition is within the range of the base composition given in Claim 1.
- This embodiment is characterized by being composed of a sinter containing 0.005 to 0.05 wt% boron (B), calculated as B 2 O 3 .
- B 2 O 3 was further added to this base composition so as to be contained in an amount of 0.001 to 0.1 wt%, and the current/voltage nonlinear resistors of sample numbers 51 to 56 shown in Table 4 were produced by the method described in the first embodiment above. That is, in the third embodiment, B 2 O 3 was contained, instead of the Ag 2 O used in the second embodiment, in amounts between 0.001 and 0.1 wt%.
- Table 4 shows the percentage change in leakage current in this third embodiment.
- Table 4 Sample number B 2 O 3 content (wt%) Percentage change in leakage current (%) 51* 0.0001 9.8 52 0.005 -21 53 0.010 -3.5 54 0.020 -8.2 55. 0.050 -6.9 56* 0.100 12.5
- the current/voltage nonlinear resistors of sample numbers 51 and 56 which are marked with an asterisk in Table 4, have compositions outside the scope of the claims of the present invention. As shown in Table 4, the characteristics of the comparative samples indicate that the percentage change in leakage current is a positive value, and the service life characteristics are low.
- the service life characteristics were low when the added amount of boron, calculated as B 2 O 3 , was less than 0.005 wt%, and when it was more than 0.05 wt%.
- the percentage change in leakage current was a negative value (see Table 4), and current/voltage nonlinear resistors with excellent service life characteristics were obtained.
- adding boron in an amount of 0.005 to 0.05 wt%, calculated as B 2 O 3 improves the service life characteristics, just as in the second embodiment. Furthermore, in this embodiment, the effect of adding boron on the service life characteristics was only discussed for the above-mentioned base composition, but the same effect will be obtained as long as the composition is within the range of the base composition given in Claim 1. Also, instead of adding silver or boron alone, both may be added at the same time, as long as the combined amount is between 0.005 and 0.05 wt%.
- Bi 2 O 3 (0.5 mol%), Co 2 O 3 (1.0 mol%), MnO (1.0 mol%), Sb 2 0 3 (2 mol%), NiO (2 mol%), Dy 2 0 3 (0.5 mol%), and Ga 3+ (0.003 mol%) were measured out as sub-components in the final proportions given in parentheses above, these components were added to the ZnO main component, and current/voltage nonlinear resistors were produced by the method described in the first embodiment above.
- This embodiment is characterized in that Ga 3+ is added as a nitrate aqueous solution.
- the stability of the resistance value is evaluated in this fourth embodiment. Specifically, the initial operating voltage (V 1mA ) was measured for 100 current/voltage nonlinear resistors in which Ga 3+ had been added as a nitrate aqueous solution, and the standard deviation of this initial operating voltage was calculated. As a comparative example, the initial operating voltage (V 1mA ) was measured for 100 current/voltage nonlinear resistors in which Ga 3+ had been added not as an aqueous solution, but as an oxide, and the standard deviation of this initial operating voltage was calculated.
- the standard deviation was calculated, and as a result the standard deviation of V 1mA when the Ga 3+ was added as a nitrate aqueous solution was 585, while the standard deviation of V 1mA when the Ga 3+ was added as an oxide was 2406. Specifically, a current/voltage nonlinear resistor with vastly less variance in its characteristics could be obtained by adding the Ga 3+ as a nitrate aqueous solution.
- gallium (Ga) was added in an extremely small amount, when gallium oxide (Ga 2 O 3 ), which is an oxide of gallium (Ga), was added, it was difficult to mix uniformly with the other raw materials, and there was a great deal of variance in the characteristics. In contrast, when gallium nitrate (Ga(N0 3 ) 3 ), which is a water-soluble gallium raw material, was added, it mixed as gallium ions with the other raw materials, which is believed to be why the characteristics were so stable.
- Ga 3+ was added as a nitrate, with the added amount varied, and the current/voltage nonlinear resistors of sample numbers 57 to 71 in Table 5 were produced by the method described in the first embodiment above.
- the disk diameter of the current/voltage nonlinear resistors was either 35, 60, or 100 mm, and the added amount of Ga 3+ was varied with the disk diameter.
- the nonlinearity (V 10kA /V 1mA ) of these current/voltage nonlinear resistors was evaluated by the method given in the first embodiment above, and the results are given in Table 5.
- the coefficient A in Table 5 is a coefficient in the following relational formula with the added amount of Ga 3+ .
- FIG. 2 shows the relation between the coefficient A and nonlinearity.
- nonlinearity obviously varies with the amount in which gallium (Ga) is added.
- Ga gallium
- added amount of gallium at which nonlinearity is good varies with the diameter of the disk. This is because the current density in the current/voltage nonlinear resistor varies with the disk diameter, and the optimal added amount of gallium is within the range of the relational formula given above.
- the present invention is not limited to the embodiments given above, and various modifications are possible as long as the sub-components bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element (R), and silver (Ag) and boron (B) are within the compositional range given in the claims.
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Abstract
Description
- The present invention relates to a current/voltage nonlinear resistor whose main component is zinc oxide (ZnO), and more particularly relates to a current/voltage nonlinear resistor in which improvements have been made to the composition of sub-components contained in the main component.
- Overvoltage protection devices such as lightning arrestors and surge absorbers are commonly incorporated into power systems or electronic device circuitry. The purpose of these devices is to protect the power system or electronic device circuitry by removing any overvoltage that has been superimposed over the normal voltage. Current/voltage nonlinear resistors are frequently used for these overvoltage protection devices. A current/voltage nonlinear resistor is a resistor with the property of exhibiting substantially insulating characteristics at ordinary voltage, but exhibiting low resistance when overvoltage is applied.
- A current/voltage nonlinear resistor is a ceramic element whose main component is zinc oxide (ZnO), and the following characteristics are required of such resistors. Naturally, the resistor must have nonlinear resistance characteristics, meaning that the resistance value varies greatly with changes in voltage, but also needs to have a long enough service life that no deterioration occurs when voltage is continuously applied over an extended period, energy capability characteristics that allow it to absorb lightning surges and switching surges without damage, and so forth. Also, current/voltage nonlinear resistors are seen to have a property whereby the resistance value drops when the temperature is higher. Consequently, thermal stability with respect to high temperature is also required.
- The procedure for producing a current/voltage nonlinear resistor will now be described (see
Japanese Patent Publication H4-25681 - As demand for power and the need for stabilization have grown in recent years, reducing the size of power transmission and conversion devices has become a pressing concern. current/voltage nonlinear resistors whose main component is zinc oxide (ZnO) have been used in lightning arrestors (overvoltage protection devices) because of their excellent nonlinear resistance characteristics, but as the resistance value rises, fewer current/voltage nonlinear resistors are stacked in a lightning arrestor. In other words, increasing the resistance of a current/voltage nonlinear resistor is an essential technological key to achieving a lightning arrestor that is more compact. Also, increasing the nonlinear resistance characteristics of a current/voltage nonlinear resistor means lower the insulation layer of a power transmission and conversion system, and is therefore linked to making power transmission and conversion devices more compact.
- A number of current/voltage nonlinear resistors with improved nonlinear resistance characteristics have been proposed in light of this situation. For instance, with the current/voltage nonlinear resistor disclosed in
Japanese Laid-Open Patent Application 2001-307909 - With the technology disclosed in
Japanese Patents 2,933,881 2,940,486 3,165,410 - Today, however, with the larger capacity of substations and the greater demand for underground substations, there is an increasingly great need for making power transmission and conversion devices smaller. Accordingly, the characteristics required of a current/voltage nonlinear resistor are at an even higher level, and with the prior art mentioned above, it is difficult to satisfy these requirements. More specifically, when the charging ratio (the voltage that is ordinarily applied to the current/voltage nonlinear resistor) was set high, a conventional current/voltage nonlinear resistor sometimes suffered severe deterioration, so that the service life was not long enough.
- Also, a reduction in the size of power transmission and conversion devices extends to reducing the size of a lightning arrestor, of course, and the following problems have been indicated when the resistance of a current/voltage nonlinear resistor was raised due to making a lightning arrestor more compact. Because the amount of surge energy absorbed increases proportionally as the resistance of a current/ voltage nonlinear resistor is raised, the heating temperature is also raised by joule heat of the current/voltage nonlinear resistor when surge energy is absorbed.
- As discussed above, because a current/voltage nonlinear resistor has a property whereby its resistance decreases as the temperature rises, if the temperature is too high, a drop in resistance occurs and there is greater current leakage. That is, since the decrease in the resistance of a current/voltage nonlinear resistor with increased resistance is greater when the temperature is raised, it has been indicated that there is a problem with thermal stability.
- As a result, current of commercial frequency after the absorption of surge energy causes thermal runaway, and this increases unevenness of heating in the current/voltage nonlinear resistor. This invites an increase in thermal stress, which can lead to the breakdown of the current/voltage nonlinear resistor. Therefore, unless excellent thermal stability has been ensured, the resistance of the current/ voltage nonlinear resistor cannot be raised high enough, and it is difficult to reduce the size of a lightning arrestor.
- The present invention was proposed in light of these problems, and it is an object thereof to provide a current/voltage nonlinear resistor with which the resistance value, nonlinear resistance characteristics, and thermal stability can be improved by specifying the compositional range of sub-components, and the size of a lightning arrestor can be reduced.
- The present invention was conceived in an effort to achieve the stated object, and is characterized in that zinc oxide (ZnO) is the main component and bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element (R) are contained as sub-components in proportions, calculated as Bi2O3, Co2O3, MnO, Sb2O3, NiO, Ga3+, and R2O3, of 0.3 to 1.5 mol% Bi2O3, 0.3 to 2.0 mol% Co2O3, 0.4 to 3.0 mol% MnO, 0.5 to 4.0 mol% Sb2O3, 0.5 to 4.0 mol% NiO, 0.0005 to 0.02 mol% Ga3+, and 0.05 to 1.0 mol% R2O3.
- With the present invention, the reason for specifying the sub-components to the above compositional ranges is that the inventors conducted various research into the compositions of current/voltage nonlinear resistors in an effort to achieved the above object, and as a result learned that keeping the proportions within the above ranges yields good resistance, nonlinear resistance characteristics, and thermal stability, and conversely that the above characteristics suffer when the proportions are outside the above ranges. Specifically, if the compositional proportions of the sub-components are kept within the above ranges, high resistance can be ensured and the nonlinear resistance characteristics and thermal stability are improved, and this makes it possible to attain the high level of characteristics required at the current time.
- The present invention provides a current/voltage nonlinear resistor with which the sub-components, namely, bismuth. (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element '(R), are contained in the compositional proportion ranges given above, and this affords excellent resistance, nonlinear resistance characteristics, and thermal stability, which in turn allows a current/voltage nonlinear resistor to be provided that can contribute to making lightning arrestors smaller.
-
- FIG. 1 is a cross section of the current/voltage nonlinear resistor pertaining to the present invention; and
- FIG. 2 is a graph of nonlinearity and the Ga3+ added amount coefficient A.
- Embodiments of the present invention will now be described in specific terms through reference to FIGS. 1 and 2 and Tables 1 to 5. Tables 1 to 5 show evaluation indicators and contained amounts of current/voltage nonlinear resistors produced with varying amounts of sub-components contained. Of the sample numbers given in the tables, those marked with an asterisk have sub-components that are outside the compositional ranges pertaining to the present invention, and are comparative samples produced for the sake of comparison. Those not marked with an asterisk, meanwhile, have sub-components within the compositional ranges corresponding to the present invention.
- A first embodiment related to the present invention will be described through reference to FIG. 1 and Tables 1 and 2. FIG. 1 is a cross section of the current/voltage nonlinear resistor pertaining to this embodiment.
- In this embodiment, zinc oxide (ZnO) was used as the main component. Bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), and gallium (Ga), were used as sub-components, and the final amounts in which these were contained, calculated as
Bi 203, Co2O3, MnO,Sb 203, NiO, and Ga3+ were within the following ranges. - The product contained 0.3 to 1.5 mol%
Bi 203, 0.3 to 2.0 mol% Co2O3, 0.4 to 3.0 mol% MnO, 0.5 to 4.0 mol% %Sb 203, 0.5 to 4.0 mol% NiO, and 0.0005 to 0.02 mol% Ga3+. - Furthermore, at least one type of rare earth oxide (R) selected from about dysprosium (Dy), europium (Eu), erbium (Er), thulium (Tm), gadolinium (Gd), yttrium (Y), holmium (Ho), and ytterbium (Yb) were contained in an amount of 0.05 to 1.0 mol%, calculated as R2O3.
- The procedure for producing the current/voltage nonlinear resistors pertaining to this embodiment and comparative samples will now be described in specific terms. Bi2O3, Co2O3, MnO, Sb2O3, NiO, Dy2O3, and Ga3+ or Al3+ were measured out as sub-components in specific amounts with respect to the ZnO main component such that the amounts in which the components were contained in the current/voltage nonlinear resistors ultimately obtained were as indicated for
sample numbers 1 to 44 in Tables 1 and 2. These raw materials were mixed in a mixer along with water and an organic binder, and each slurry was adjusted to a uniform consistency. The Ga3+ or Al3+ here was added as a nitrate aqueous solution. - Next, each of the slurries thus obtained was spray granulated in a spray dryer to produce a granulated powder with a grain size of about 100 µm. The granulated powder thus obtained was put in a metal mold and pressed into a disk with a diameter of 125 mm and a thickness of 30 mm, and this molded disk was heated to 500°C to remove the organic binder that had been added.
- After this, the disk was fired for 2 hours at 1100°C to obtain the
sinter 1 shown in FIG. 1. The side faces of thesinter 1 were coated with an inorganic insulating substance, and these coatings were heat treated to form side face insulatinglayers 2. Finally, the upper and lower end faces of thesinter 1 provided with the side face insulatinglayers 2 were polished to a specific thickness, after whichelectrodes 3 were thermal sprayed onto the polished faces of thesinter 1 to produce a current/voltage nonlinear resistor. - The characteristics of the various current/voltage nonlinear resistors produced by the above procedure were evaluated as follows. First, the resistance of the current/voltage nonlinear resistor was evaluated by measuring the initial operating voltage of the current/voltage nonlinear resistor (the voltage when 1 mA of AC current was applied; V1mA). The higher the initial operating voltage, the fewer current/voltage nonlinear resistors that need to be stacked in a lightning arrestor, so this voltage is effective as an index for ascertaining how compact a lightning arrestor can be made.
- The voltage when a 10 kA impulse current of 8 x 20 µs was applied (V10kA) was measured, and the ratio of this to the initial operating voltage V1mA (V10kA/V1mA) was evaluated as a nonlinearity coefficient. The smaller the value of this nonlinearity coefficient, the better the nonlinear resistance characteristics.
- The thermal stability of the current/voltage nonlinear resistor was evaluated by measuring the resistance leakage current when AC voltage that was 90% of the initial operating voltage was applied in a 200°C thermostatic tank. Specifically, the less leakage current at high temperature there is at 200°C, the better the thermal stability. The compositions of ten elements with each added component composition were measured, and the average thereof was used for the compositional value. The measurement results are given in Tables 1 and 2.
Table 1 Sample Amounts of sub-components contained (mol%) Initial operating voltage V1mA (V/mm) Nonlinearity V10kA/V1mA Leakage current at high temperature (mA) Bi2O3 Sb2O3 MnO NiO Co2O3 Ga3+ Al 3+ Dy2O3 1* 0.20 2.00 1.00 2.00 1.00 0.003 0 0.50 813 1.560 25.0 2 0.30 2.00 1.00 2.00 1.00 0.003 0 0.50 625 1.453 13.4 3 0.50 2.00 1.00 2.00 1.00 0.003 0 0.50 552 1.458 10.3 4 1.00 2.00 1.00 2.00 1.00 0.003 0 0.50 498 1.467 9.7 5 1.50 2.00 1.00 2.00 1.00 0.003 0 0.50 405 1.472 8.9 6* 1.80 2.00 1.00 2.00 1.00 0.003 0 0.50 350 1.492 8.0 7* 0.50 0.30 1.00 2.00 1.00 0.003 0 0.50 368 1.502 7.4 8 0.50 0.50 1.00 2.00 1.00 0.003 0 0.50 402 1.475 8.9 9 0.50 1.00 1.00 2.00 1.00 0.003 0 0.50 502 1.462 9.2 10 0.50 3.00 1.00 2.00 1.00 0.003 0 0.50 598 1.468 11.2 11 0.50 4.00 1.00 2.00 1.00 0.003 0 0.50 605 1.487 13.5 12* 0.50 5.00 1.00 2.00 1.00 0.003 0 0.50 698 1.521 16.5 13* 0.50 2.00 0.20 2.00 1.00 0.003 0 0.50 444 1.524 8.7 14 0.50 2.00 0.40 2.00 1.00 0.003 0 0.50 478 1.492 9.1 15 0.50 2.00 0.80 2.00 1.00 0.003 0 0.50 542 1.458 9.2 16 0.50 2.00 2.00 2.00 1.00 0.003 0 0.50 578 1.472 9.1 17 0.50 2.00 3.00 2.00 1.00 0.003 0 0.50 595 1.482 11.5 18* 0.50 2.00 4.00 2.00 1.00 0.003 0 0.50 602 1.542 14.8 19* 0.50 2.00 1.00 0.30 1.00 0.003 0 0.50 395 1.501 9.8 20 0.50 2.00 1.00 0.50 1.00 0.003 0 0.50 448 1.492 8.2 21 0.50 2.00 1.00 1.00 1.00 0.003 0 0.50 502 1.472 9.2 22 0.50 2.00 1.00 3.00 1.00 0.003 0 0.50 580 1.443 11.2 23 0.50 2.00 1.00 4.00 1.00 0.003 0 0.50 602 1.440 13.5 24* 0.50 2.00 1.00 5.00 1.00 0.003 0 0.50 621 1.502 17.9 Table 2 Sample number Amounts of sub-components contained (mol%) Initial operating voltage V1mA (V/mm) Nonlinearity V10KA/V1mAV Leakage current at high temperature (mA) Bi2O3 Sb2O3 MnO NiO Co2O3 Ga3+ Al3+ Dy2O3 25* 0.50 2.00 1.00 2.00 0.20 0.003 0 0.50 458 1.542 12.3 26 0.50 2.00 1.00 2.00 0.30 0.003 0 0.50 498 1.490 9.2 27 0.50 2.00 1.00 2.00 0.50 0.003 0 0.50 524 1.462 9.2 28 0.50 2.00 1.00 2.00 1.50 0.003 0 0.50 575 1.442 11.2 29 0.50 2.00 1.00 2.00 2.00 0.003 0 0.50 592 1.432 13.5 30* 0.50 2.00 1.00 2.00 2.50 0.003 0 0.50 618 1.502 21.5 31* 0.50 2.00 1.00 2.00 1.00 0.0003 0 0.50 645 1.592 13.4 32 0.50 2.00 1.00 2.00 1.00 0.0005 0 0.50 618 1.472 19.9 33 0.50 2.00 1.00 2.00 1.00 0.001 0 0.50 584 1.468 10.9 34 0.50 2.00 1.00 2.00 1.00 0.005 0 0.50 542 1.460 9.9 35 0.50 2.00 1.00 2.00 1.00 0.01 0 0.50 511 1.490 9.7 36 0.50 2.00 1.00 2.00 1.00 0.02 0 0.50 495 1.497 11.2 37* 0.50 2.00 1.00 2.00 1.00 0.03 0 0.50 462 1.582 10.9 38* 0.50 2.00 1.00 2.00 1.00 0 0.003 0.50 552 1.459 18.2 39* 0.50 2.00 1.00 2.00 1.00 0.003 0 0.03 342 1.502 7.2 40 0.50 2.00 1.00 2.00 1.00 0.003 0 0.05 443 1.495 8.1 41 0.50 2.00 1.00 2.00 1.00 0.003 0 0.10 492 1.482 9.2 42 0.50 2.00 1.00 2.00 1.00 0.003 0 0.30 524 1.462 9.9 43 0.50 2.00 1.00 2.00 1.00 0.003 0 1.00 591 1.489 12.5 44* 0.50 2.00 1.00 2.00 1.00 0.003 0 1.50 594 1.524 20.1 - As discussed above, the current/voltage nonlinear resistors with the sample numbers marked with an asterisk in Tables 1 and 2 had compositions outside the ranges of the present invention, and were samples produced for the sake of comparison. As is clear from the results in Tables 1 and 2, the characteristics of the comparative samples do not satisfy the conditions of an excellent current/voltage nonlinear resistor as specified above.
- Initial operating voltage (V1mA) > 400 V/mm
- Nonlinearity coefficient (V10kA/V1mA) < 1.50
- Leakage current at high temperature (200°C) < 15 mA
- In contrast, the current/voltage nonlinear resistors with sample numbers not marked with an asterisk in Tables 1 and 2 were within the compositional ranges specified in the claims of the present invention, and therefore exhibited excellent results for initial operating voltage, nonlinearity coefficient, and leakage current at high temperature. Specifically, the current/voltage nonlinear resistors pertaining to this embodiment can be considered to have high resistance and excellent nonlinear resistance characteristics and thermal stability.
- Let us now discuss the role of the various sub-components contained in this embodiment, and also mention that the characteristics of this embodiment are not attained with the comparative samples.
- Bi2O3 is a component that is present at the boundary of the zinc oxide (ZnO), which is the main component of the sinter, and is responsible for nonlinear resistance characteristics. The role of this component is to promote the growth of ZnO crystal grains. If we compare
sample numbers 1 to 6 here, we see that when the amount of Bi2O3 was less than 0.3 mol% (sample number 1), the material was in the liquid phase during sintering, and the amount ofBi 203 was inadequate to improve sintering. - Accordingly, excellent characteristics were not obtained in terms of nonlinearity and leakage current at high temperature. Also, when the amount of Bi2O3 was over 1.5 mol% (sample number 6), the growth of ZnO particles proceeded too much during sintering, so a sufficiently high initial operating voltage could not be obtained.
- Sb2O3 is a component that controls and makes uniform the growth of ZnO crystal grains during sintering by forming spinel (Zn7Sb2O12) particles along with zinc oxide (ZnO). Its role is to improve nonlinear resistance characteristics and, at the same time, suppress the growth of ZnO crystal grains.
- A comparison of
sample numbers 3 and 7 to 12 reveals that if the Sb2O3 content is less than 0.5 mol% (sample number 7), there will be too few spinel particles capable of suppressing grain growth during sintering, so excellent characteristics cannot be obtained in terms of initial operating voltage and nonlinearity. If the amount of Sb2O3 is over 4 mol% (sample number 12), however, it will act as an insulating component in the sinter, and there will be too many spinel particles, so excellent characteristics cannot be obtained in terms of nonlinearity and leakage current at high temperature. - MnO is a component that primarily forms a solid solution with spinel particles and improves nonlinear resistance characteristics. A comparison of
sample numbers 3 and 13 to 18 reveals that if the MnO content is less than 0.4 mol% (sample number 13), the electrical characteristics are unstable at the ZnO grain boundary, so excellent nonlinearity cannot be obtained. If the amount of MnO is over 3 mol% (sample number 18), however, here again it is impossible to obtain excellent nonlinearity characteristics. - NiO is similar to MnO in that it primarily forms a solid solution with spinel particles and improves nonlinear resistance characteristics. A comparison of
sample numbers 3 and 19 to 24 reveals that if the NiO content is less than 0.5 mol% (sample number 19), the very little NiO will form a solid solution with the spinel particles, so excellent initial operating voltage and nonlinearity cannot be obtained. If the amount of NiO is over 4 mol% (sample number 24), however, the electrical characteristics are unstable at the ZnO grain boundary, so excellent nonlinearity characteristics and leakage current at high temperature characteristics cannot be obtained. - Co2O3 also is a component that primarily forms a solid solution with spinel particles and improves nonlinear resistance characteristics. A comparison of
sample numbers 3 and 25 to 30 reveals that if the Co2O3 content is less than 0.3 mol% (sample number 25), the electrical characteristics are unstable at the ZnO grain boundary, so excellent nonlinearity cannot be obtained, but if the amount of Co2O3 is over 2 mol% (sample number 30), here again the electrical characteristics are unstable at the ZnO grain boundary, making it impossible to obtain excellent nonlinearity characteristics or leakage current at high temperature characteristics. - Ga3+ serves to improve nonlinear resistance characteristics by forming a solid solution in the ZnO particles and lowering the electrical resistance of the ZnO particles. Aluminum (Al) has often been used in prior art as a component with a similar purpose, but improving nonlinear resistance characteristics by adding gallium gives a current/voltage nonlinear resistor with better thermal stability than by adding aluminum.
- A comparison of
sample numbers 3 and 31 to 38 reveals that if the Ga3+ content is less than 0.0005 mol% (sample number 31), not enough Ga3+ will form a solid solution in the ZnO particles in the sinter, so the electrical resistance of the ZnO particles will be high and excellent nonlinearity cannot be obtained. - If the amount of Ga3+ is over 0.02 mol% (sample number 37), however, the Ga3+ will precipitate at the ZnO grain boundary and adversely affect the electrical characteristics of the ZnO grain boundary, so excellent nonlinearity cannot be obtained. Furthermore, compared to when Al3+ is added (sample number 38), adding Ga3+ allows better leakage current at high temperature characteristics to be obtained.
- If the above-mentioned Sb2O3, Co2O3, NiO, and MnO are added in too large an amount in an effort to raise the resistance of a current/voltage nonlinear resistor, the resistance value will be highly dependent on temperature, so thermal stability will decrease.
- In view of this, in this embodiment, higher resistance is -achieved by adding Dy2O3, which is a rare earth oxide that has the effect of raising resistance, the added amounts of Sb2O3, Co2O3, NiO, and MnO are effectively reduced and the temperature dependence of resistance is thereby lessened, and the thermal stability of the current/voltage nonlinear resistor can be increased.
- A comparison of
sample numbers 3 and 39 to 44 reveals that if the Dy2O3 content is less than 0.3 mol% (sample number 39), there will not be enough Dy2O3 to have the effect of suppressing grain growth, so excellent initial operating voltage and nonlinearity cannot be obtained. If the amount of Dy2O3 is over 1.0 mol% (sample number 44), however, the electrical characteristics will be unstable at the ZnO grain boundary, making it impossible to obtain excellent characteristics in terms of nonlinearity or leakage current at high temperature. - Furthermore, an oxide of dysprosium (Dy) was used as a rare earth oxide in this embodiment, but oxides of other rare earth elements, namely, europium (Eu), erbium (Er), thulium (Tm), gadolinium (Gd), yttrium (Y), holmium (Ho), and ytterbium (Yb), may also be used, and these will have the same effect as an oxide of dysprosium (Dy). Also, as long as the amount in which the various rare earth oxides are contained ends up being within a range of 0.05 to 1.0 mol%, the combination thereof may be selected as desired.
- As described above, in this embodiment zinc oxide (ZnO) is the main component and the final amounts of sub-components are within the ranges given above, which makes it possible to obtain a current/voltage nonlinear resistor that has high resistance and excellent thermal stability and nonlinear resistance characteristics. Accordingly, the number of stacked layers of current/voltage nonlinear resistor can be reduced while maintaining high reliability, and this contributes to making a lightning arrestor smaller.
- Next, a second embodiment related to the present invention will be described through reference to Table 3. This embodiment is characterized by being composed of a sinter containing 0.005 to 0.05 wt% silver (Ag), calculated as Ag2O.
- Specifically, Bi2O3 (0.5 mol%), Co2O3 (1.0 mol%), MnO (1.0 mol%), Sb2O3 (2 mol%), NiO (2 mol%), Dy2O3 (0.5 mol%), and Ga3+ (0.003 mol% as a nitrate aqueous solution) were measured out as sub-components in the final proportions given in parentheses above, and these components were added to the ZnO main component. Ag2O was further added to this base composition so as to be contained in an amount of 0.001 to 0.1 wt%, and the current/voltage nonlinear resistors of sample numbers 45 to 50 shown in Table 3 were produced by the method described in the first embodiment above.
- The service life characteristics of these current/voltage nonlinear resistors were evaluated. This was accomplished by continuously applying the voltage (V1mA) when a 1 mA current was flowing, in an air atmosphere at 120°C for 3000 hours, and measuring the percentage change in the leakage current (Ir) before and after the application of V1mA. The results are given in Table 3.
-
- If the change in leakage current here is a negative value, this indicates that the current/voltage nonlinear resistor has excellent service life characteristics.
Table 3 Sample number Ag2O content (wt%) Percentage change in leakage, current (%) 45* 0.0001 9.2 46 0.005 -1.2 47 0.010 -5.4 48 0.020 -9.2 49 0.050 -0.6 50* 0.100 4.9 - The current/voltage nonlinear resistors of sample numbers 45 and 50, which are marked with an asterisk in Table 3, have compositions outside the scope of the claims of the present invention. As is clear from the results given in Table 3, the characteristics of the comparative samples indicate that the percentage change in leakage current is a positive value, and the service life characteristics are low. In other words, when the added amount of silver, calculated as Ag2O, was less than 0.005 wt%, there was no effect of improving service life characteristics. When the amount was over 0.05 wt%, though, this had the opposite effect of causing the service life characteristics to deteriorate.
- In contrast, with this embodiment (sample numbers 46 to 49) in which the Ag2O content was from 0.005 to 0.05 wt%, the percentage change in leakage current was a negative value (see Table 3), and it is clear that current/voltage nonlinear resistors with excellent service life characteristics were obtained.
- Specifically, with this embodiment, adding silver in an amount of 0.005 to 0.05 wt%, calculated as Ag2O, reduces the change over time in leakage current and improves the service life characteristics. Furthermore, in this embodiment, the effect of adding silver on the service life characteristics was only discussed for the base composition given in the Constitution and Production Procedure above, but the same effect will be obtained as long as the composition is within the range of the base composition given in
Claim 1. - Next, a third embodiment related to the present invention will be described through reference to Table 4. This embodiment is characterized by being composed of a sinter containing 0.005 to 0.05 wt% boron (B), calculated as B2O3.
- Specifically, Bi2O3 (0.5 mol%), Co2O3 (1.0 mol%), MnO (1.0 mol%), Sb2O3 (2 mol%), NiO (2 mol %), Dy2O3 (0.5 mol %), and Ga3+ (0.003 mol% as a nitrate aqueous solution) were measured out as sub-components in the final proportions given in parentheses above, and these components were added to the ZnO main component. Up to this point this embodiment is the same as the second embodiment above.
- B2O3 was further added to this base composition so as to be contained in an amount of 0.001 to 0.1 wt%, and the current/voltage nonlinear resistors of sample numbers 51 to 56 shown in Table 4 were produced by the method described in the first embodiment above. That is, in the third embodiment, B2O3 was contained, instead of the Ag2O used in the second embodiment, in amounts between 0.001 and 0.1 wt%.
- The service life characteristics of these current/voltage nonlinear resistors were evaluated by the method given in the second embodiment. Table 4 shows the percentage change in leakage current in this third embodiment.
Table 4 Sample number B2O3 content (wt%) Percentage change in leakage current (%) 51* 0.0001 9.8 52 0.005 -21 53 0.010 -3.5 54 0.020 -8.2 55. 0.050 -6.9 56* 0.100 12.5 - The current/voltage nonlinear resistors of sample numbers 51 and 56, which are marked with an asterisk in Table 4, have compositions outside the scope of the claims of the present invention. As shown in Table 4, the characteristics of the comparative samples indicate that the percentage change in leakage current is a positive value, and the service life characteristics are low.
- In other words, the service life characteristics were low when the added amount of boron, calculated as B2O3, was less than 0.005 wt%, and when it was more than 0.05 wt%. In contrast, with this embodiment (sample numbers 52 to 55) in which the B2O3 content was from 0.005 to 0.05 wt%, the percentage change in leakage current was a negative value (see Table 4), and current/voltage nonlinear resistors with excellent service life characteristics were obtained.
- Specifically, with this embodiment, adding boron in an amount of 0.005 to 0.05 wt%, calculated as B2O3, improves the service life characteristics, just as in the second embodiment. Furthermore, in this embodiment, the effect of adding boron on the service life characteristics was only discussed for the above-mentioned base composition, but the same effect will be obtained as long as the composition is within the range of the base composition given in
Claim 1. Also, instead of adding silver or boron alone, both may be added at the same time, as long as the combined amount is between 0.005 and 0.05 wt%. - A fourth embodiment related to the present invention will now be described. In this embodiment, Bi2O3 (0.5 mol%), Co2O3 (1.0 mol%), MnO (1.0 mol%), Sb203 (2 mol%), NiO (2 mol%), Dy203 (0.5 mol%), and Ga3+ (0.003 mol%) were measured out as sub-components in the final proportions given in parentheses above, these components were added to the ZnO main component, and current/voltage nonlinear resistors were produced by the method described in the first embodiment above. This embodiment is characterized in that Ga3+ is added as a nitrate aqueous solution.
- The stability of the resistance value is evaluated in this fourth embodiment. Specifically, the initial operating voltage (V1mA) was measured for 100 current/voltage nonlinear resistors in which Ga3+ had been added as a nitrate aqueous solution, and the standard deviation of this initial operating voltage was calculated. As a comparative example, the initial operating voltage (V1mA) was measured for 100 current/voltage nonlinear resistors in which Ga3+ had been added not as an aqueous solution, but as an oxide, and the standard deviation of this initial operating voltage was calculated.
- In this embodiment and the comparative example, the standard deviation was calculated, and as a result the standard deviation of V1mA when the Ga3+ was added as a nitrate aqueous solution was 585, while the standard deviation of V1mA when the Ga3+ was added as an oxide was 2406. Specifically, a current/voltage nonlinear resistor with vastly less variance in its characteristics could be obtained by adding the Ga3+ as a nitrate aqueous solution.
- Because gallium (Ga) was added in an extremely small amount, when gallium oxide (Ga2O3), which is an oxide of gallium (Ga), was added, it was difficult to mix uniformly with the other raw materials, and there was a great deal of variance in the characteristics. In contrast, when gallium nitrate (Ga(N03)3), which is a water-soluble gallium raw material, was added, it mixed as gallium ions with the other raw materials, which is believed to be why the characteristics were so stable.
- A fifth embodiment related to the present invention will be described through reference to Table 5. In this embodiment, Bi203 (0.5 mol%), Co2O3 (1.0 mol%), MnO (1.0 mol%), Sb203 (2 mol%), NiO (2 mol%), and Dy2O3 (0.5 mol%) were measured out as sub-components in the final proportions given in parentheses above, and these components were added to the ZnO main component.
- Ga3+ was added as a nitrate, with the added amount varied, and the current/voltage nonlinear resistors of sample numbers 57 to 71 in Table 5 were produced by the method described in the first embodiment above. Here, the disk diameter of the current/voltage nonlinear resistors was either 35, 60, or 100 mm, and the added amount of Ga3+ was varied with the disk diameter.
- The nonlinearity (V10kA/V1mA) of these current/voltage nonlinear resistors was evaluated by the method given in the first embodiment above, and the results are given in Table 5. The coefficient A in Table 5 is a coefficient in the following relational formula with the added amount of Ga3+.
- This embodiment is characterized in that the above-mentioned coefficient A is between 5 and 14.
(A: coefficient; D: disk diameter (mm))Table 5 Sample number D (mm) Ga3+ added amount (mol%) Coefficient A Nonlinearity V10kA/V1mA 57* 35 0.002 3.47 1.742 58 35 0.004 5.47 1.672 59 35 0.008 9.47 1.652 60 35 0.12 13.47 1.672 61* 35 0.015 16.47 1.729 62* 60 0.002 4.52 1.568 63 60 0.003 5.52 1.502 64 60 0.005 7.52 1.492 65 60 0.01 12.52 1.502 66* 60 0.013 15.52 1.584 67* 100 0.0003 4.50 1.542 68 100 0.0008 5.00 1.468 69. 100 0.003 7.20 1.458 70 100 0.008 12.20 1.468 71* 100 0.012 16.20 1.521 - FIG. 2 shows the relation between the coefficient A and nonlinearity. As shown in FIG. 2, nonlinearity obviously varies with the amount in which gallium (Ga) is added. Here, when the current/voltage nonlinear resistor is disk shaped, added amount of gallium at which nonlinearity is good varies with the diameter of the disk. This is because the current density in the current/voltage nonlinear resistor varies with the disk diameter, and the optimal added amount of gallium is within the range of the relational formula given above.
- In other words, as is clear from FIG. 2, if the coefficient A is between 5 and 14, this is the optimal region for obtaining excellent nonlinearity, regardless of the disk diameter of the current/voltage nonlinear resistor. This embodiment, in which Ga3+ is added in an amount at which the coefficient A will be from 5 to 14, allows exceedingly good nonlinear resistance characteristics to be obtained.
- The present invention is not limited to the embodiments given above, and various modifications are possible as long as the sub-components bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element (R), and silver (Ag) and boron (B) are within the compositional range given in the claims.
- It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.
Claims (8)
- A current/voltage nonlinear resistor in which zinc oxide (ZnO) is the main component and bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), gallium (Ga), and a rare earth element (R) are sub-components,
wherein the sub-components, calculated as Bi203, Co2O3, MnO, Sb2O3, NiO, Ga3+, and R2O3, are contained in the following proportions:Bi2O3: 0.3 to 1.5 mol%,Co2O3: 0.3 to 2.0 mol%,MnO: 0.4 to 3.0 mol%,Sb2O3: 0.5 to 4.0 mol%,NiO: 0.5 to .4.0 mol%,Ga3+: 0.0005 to 0.02 mol%, andR2O3: 0.05 to 1.0 mol%. - The current/voltage nonlinear resistor according to Claim 1, composed of a sinter containing 0.005 to 0.05 wt% silver (Ag), calculated as Ag2O3.
- The current/voltage nonlinear resistor according to Claim 1, composed of a sinter containing 0.005 to 0.05 wt% boron (B), calculated as B2O3.
- The current/voltage nonlinear resistor according to Claim 1, containing as the rare earth element (R) at least one member of the group consisting of dysprosium (Dy), europium (Eu), erbium (Er), thulium (Tm), gadolinium (Gd), yttrium (Y), holmium (Ho), and ytterbium (Yb).
- The current/voltage nonlinear resistor according to Claim 4, composed of a sinter containing 0.005 to 0.05 wt% silver (Ag), calculated as Ag2O3.
- The current/voltage nonlinear resistor according to Claim 4, composed of a sinter containing 0.005 to 0.05 wt% boron (B), calculated as B2O3.
- The current/voltage nonlinear resistor according to Claim 1 or 4, wherein a water-soluble raw material is used as a gallium (Ga) addition raw material.
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US10204722B2 (en) | 2014-05-19 | 2019-02-12 | Epcos Ag | Electronic component and method for the production thereof |
US11031159B2 (en) | 2016-03-17 | 2021-06-08 | Tdk Electronics Ag | Ceramic material, varistor and methods of preparing the ceramic material and the varistor |
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KR101300560B1 (en) * | 2009-07-01 | 2013-09-03 | 삼성코닝정밀소재 주식회사 | ZnO-based conductor |
US8729809B2 (en) * | 2009-09-08 | 2014-05-20 | Denovo Lighting, Llc | Voltage regulating devices in LED lamps with multiple power sources |
JP2012038928A (en) * | 2010-08-06 | 2012-02-23 | Toshiba Corp | Lightning arrester |
KR101690720B1 (en) * | 2015-07-31 | 2016-12-28 | 동의대학교 산학협력단 | Mn/Co/Bi/Dy added ZnO-V2O5 based varistor and manufacturing method for the same |
JP6937390B2 (en) * | 2018-01-26 | 2021-09-22 | 株式会社東芝 | Materials for current-voltage non-linear resistors, current-voltage non-linear resistors and their manufacturing methods |
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EP0029749A1 (en) * | 1979-11-27 | 1981-06-03 | Matsushita Electric Industrial Co., Ltd. | Voltage dependent resistor and method of making same |
EP0070468A2 (en) * | 1981-07-16 | 1983-01-26 | Kabushiki Kaisha Toshiba | Metal Oxide varistor |
EP1150306A2 (en) * | 2000-04-25 | 2001-10-31 | Kabushiki Kaisha Toshiba | Current/voltage non-linear resistor and sintered body therefor |
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JPS6182401A (en) * | 1984-09-29 | 1986-04-26 | 株式会社東芝 | Voltage non-linearity resistor and manufacture thereof |
JPH0574606A (en) * | 1991-09-12 | 1993-03-26 | Matsushita Electric Ind Co Ltd | Zinc oxide varistor for low voltage |
JP3830354B2 (en) | 2001-03-28 | 2006-10-04 | 東光電気株式会社 | Method for manufacturing voltage nonlinear resistor |
KR100441863B1 (en) * | 2002-03-28 | 2004-07-27 | 주식회사 에이피케이 | Fabrication of praseodymium-based zinc oxide varistors |
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EP0029749A1 (en) * | 1979-11-27 | 1981-06-03 | Matsushita Electric Industrial Co., Ltd. | Voltage dependent resistor and method of making same |
EP0070468A2 (en) * | 1981-07-16 | 1983-01-26 | Kabushiki Kaisha Toshiba | Metal Oxide varistor |
EP1150306A2 (en) * | 2000-04-25 | 2001-10-31 | Kabushiki Kaisha Toshiba | Current/voltage non-linear resistor and sintered body therefor |
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US10204722B2 (en) | 2014-05-19 | 2019-02-12 | Epcos Ag | Electronic component and method for the production thereof |
US11031159B2 (en) | 2016-03-17 | 2021-06-08 | Tdk Electronics Ag | Ceramic material, varistor and methods of preparing the ceramic material and the varistor |
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KR100812425B1 (en) | 2008-03-10 |
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