JP2012015435A - Method for manufacturing nonlinear voltage resistor and lightning element formed of nonlinear voltage resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a nonlinear voltage resistor which has high sintered density and small crystal grain size, and to provide a lightning element formed of the nonlinear voltage resistor, which has high V/t and excellent electrical characteristics such as V-I characteristics and capacitance.SOLUTION: The nonlinear voltage resistor is manufactured by the steps of: previously preparing a powder of an oxide by mixing at least a powder of zinc oxide (ZnO), a powder of a cobalt (Co) compound and a powder of an antimony (Sb) compound, reacting the mixture at a heating temperature of 950-1,350°C to produce the oxide containing ZnCoSbO(0≤x≤7), which becomes a grain-growth inhibitor, and pulverizing the oxide; adding the powder of the oxide containing the grain-growth inhibitor as an additive to the powder of the zinc oxide (ZnO) that is a main component and a well-known additive powder made of a compound and mixing them; pressure-molding the mixture in a mold; and then sintering the molded body. The lightning element formed of the nonlinear voltage resistor is formed by providing high insulating layers at side faces and electrodes at the upper face and the lower face of the nonlinear voltage resistor.

Description

  The present invention relates to a method for manufacturing a voltage non-linear resistor and a voltage non-linear resistance lightning protection device, and more particularly to a method for manufacturing a voltage non-linear resistance mainly composed of zinc oxide (ZnO) and a voltage non-linear resistance lightning protection device.

  Usually, in the power system, a circuit breaker is installed in the transmission line, and an overvoltage protection device such as a lightning arrester is used to suppress overvoltage such as switching surge generated when the circuit breaker opens and closes, and lightning surge caused by lightning. Is provided. As a lightning protection element, which is a main component of an overvoltage protection device, a ceramic voltage non-linear resistor whose main component is ZnO has been frequently used recently.

This voltage non-linear resistor is large in the ZnO-Bi ₂ O ₃ system containing ZnO and bismuth oxide (Bi ₂ O ₃ ) and in the ZnO—Pr ₆ O ₁₁ system containing ZnO and praseodymium oxide (Pr ₆ O ₁₁ ). Separated. The former voltage non-linear resistor is easy to manufacture and economical because it is easy to obtain a device with high uniformity compared to the latter, and is insensitive to impurities. It is mainly used for lightning arresters.

  Generally, the lightning protection element using the former voltage non-linear resistor is manufactured by using a sintered body as follows. That is, an oxide powder such as bismuth (Bi), antimony (Sb), cobalt (Co), manganese (Mn), chromium (Cr), nickel (Ni), and silicon (Si) is mixed with the main component ZnO. After that, it is molded into a predetermined shape such as a disk shape or a donut shape, and this is sintered in a high-temperature sintering furnace to make a sintered body, and both end faces of this sintered body are polished. In addition, electrodes are provided on both polished surfaces.

In recent years, in order to reduce power loss in transmission lines from the viewpoint of energy saving or CO ₂ emission reduction, ultra high voltage transmission system voltages have been promoted worldwide. For this reason, it is required that the lightning arrester used in the lightning arrester can cope with an ultrahigh voltage.

Since the above-described lightning arrester mainly composed of ZnO uses the grain boundary characteristics of polycrystalline ceramics, the operation start voltage V _XA (the element voltage when a current xA is passed, generally x is 1 mA, or V _{1 mA,} is used) is proportional to the number of grain boundaries present between the electrodes.

In order to make the surge arrester compatible with ultra-high voltage, it is necessary to stack a large number of lightning arresters that are normally manufactured. Therefore, the total number of stacked surge arresters must be increased, and the container to be accommodated must be enlarged. Disappear. Therefore, in order to reduce the overall size of the lightning arrester, a lightning arrester having a large number of grain boundaries per unit thickness, that is, a small grain size and a high V _{1 mA} (V _{1 mA} / t) per unit thickness is required.

Generally, in order to obtain a voltage non-linear resistor having good electrical characteristics and high mechanical strength, it is necessary to produce a sintered body having a uniform crystal grain size and a high density. However, ZnO has a property called abnormal grain growth that tends to grow in a specific direction (c-axis), and the sintered body tends to have non-uniform grain sizes. In addition, in the ZnO—Bi ₂ O ₃ -based voltage nonlinear resistor, Bi ₂ O _3, which is one of the main additives, melts at 825 ° C. or more and becomes a liquid phase. For this reason, remarkable abnormal grain growth accompanying liquid phase sintering occurs, and there is a tendency that the particle size tends to become more non-uniform, and accordingly, there is also a tendency that the sintered density inside the sintered body tends to vary. .

For the above reason, a ZnO—Bi ₂ O ₃ system voltage non-linear resistor is usually added with a large amount of silicon oxide (SiO ₂ ) or antimony oxide (Sb ₂ O ₃ ) having a grain growth suppressing action, and at the same time, 1100 It was formed by sintering at a temperature of ℃ or higher. According to this method, a lightning arrester with V _{1 mA} / t = 200 to 400 V / mm is currently commercially available.

As described in Non-Patent Document 1, the chemical reaction mechanism of the sintering process in which Sb ₂ O ₃ acts as a grain growth inhibitor is considered as follows. That is, when a molded body in which ZnO and the above additives are mixed is fired, ZnO and Sb ₂ O ₃ form a spinel particle represented by Zn ₇ Sb ₂ O ₁₂ by the reaction of the following formula (1). And spinel particle | grains precipitate at a grain boundary and prevent a grain boundary movement in a grain growth process, As a result, grain growth is suppressed.
7ZnO + Sb ₂ O ₃ + O ₂ ⇒Zn ₇ Sb ₂ O ₁₂ (1)
On the other hand, the chemical reaction mechanism in which SiO ₂ acts as a grain growth inhibitor is considered as follows. That is, ZnO and SiO ₂ form Zn ₂ SiO ₄ particles by the reaction of the formula (2), and this suppresses grain growth.
2ZnO + SiO ₂ ⇒Zn ₂ SiO ₄ (2)
Zn ₇ Sb ₂ O ₁₂ is produced at a temperature of 950 ° C. or higher through several reaction processes. As one of the reaction processes, there is a process of the following formula (3).
_{2Zn 2 Bi 3 Sb 3 O 14} + 17ZnO⇔3Zn 7 Sb 2 O 12 + 3Bi 2 O 3 (3)
Since this reaction process is a reaction that goes through the liquid phase of Bi ₂ O ₃ , Zn ₇ Sb ₂ O ₁₂ tends to grow. Further, although Zn ₂ SiO ₄ is produced at around 1050 ° C., it becomes amorphous at 1150 ° C., so it is clear that it is not necessarily a thermally stable grain growth inhibitor.

From the above formulas (1) and (2), in order for the reaction to occur completely, 7 moles of ZnO per mole of Sb ₂ O ₃ and 2 moles of ZnO per mole of SiO ₂ , Respectively. Therefore, when a large amount of Sb ₂ O ₃ or SiO ₂ is added in order to enhance the effect of suppressing grain growth, more ZnO than the added amount is consumed for forming Zn ₇ Sb ₂ O ₁₂ and Zn ₂ SiO ₄ . Since these formations are insulators and do not act positively electrically, if they are contained in a large amount in the sintered body, the effective area of the lightning protection element is greatly reduced. Problems such as a decrease in electric capacity also arise.

As is well known, there is a Zener formula as a theoretical formula regarding pinning for suppressing grain growth by inclusions. In this equation, the particle diameter D suppressed by the grain growth inhibitor is represented by D∝ (r / f) from the grain diameter r of the grain growth inhibitor and the addition ratio f of the grain growth inhibitor. According to this theory, when the particle diameter D to be obtained is to be reduced, if the particle diameter r of the grain growth inhibitor increases, a large amount of grain growth inhibitor must be added. Therefore, an effective grain growth inhibitor for a ZnO—Bi ₂ O ₃ system voltage non-linear resistor is a material that is thermally stable during the sintering process and maintains the initial mixed fine particle state. I need it.

As a manufacturing method for obtaining a ZnO—Bi ₂ O ₃ -based voltage non-linear resistor having good electrical characteristics and excellent reliability with respect to a DC load or a surge, methods described in Patent Documents 1 and 2 have been proposed. Patent Document 1 discloses a synthetic powder prepared by heat-treating a mixed powder of at least Bi ₂ O ₃ , titanium oxide (TiO ₂ ), and Sb ₂ O ₃ at 450 to 850 ° C. with respect to ZnO as a main component. It is manufactured by adding.

Also, in Patent Document 2, and ZnO powder were mixed with _Bi 2 _{O 3} and _{Sb 2 O 3, Bi 2 O} 3 of the _Sb 2 _{O 3} obtained by heat treatment in the range of 400 to 700 ° C. A synthetic powder is produced, and at least two or more selected from specific metal oxides as additives are added to the synthetic powder, pressed, sintered, and then manufactured.

Japanese Patent No. 3313533 JP-A-10-308302

Michio Matsuoka “Globally Invented Zinc Oxide Varistor Born in Japan” Ohm Company pp. 43 (2009)

In the production methods described in Patent Documents 1 and 2, Bi ₂ O ₃ , Sb ₂ O ₃ , and TiO ₂ are reacted in advance at 450 to 850 ° C., or Bi ₂ O ₃ and Sb ₂ O ₃ are previously reacted in 400 to 700. ℃ in reacted, to synthesize BiSbO ₄ and _Bi 3 SbO _7, can be densified sintered body at a low temperature. However, since BiSbO ₄ and Bi ₃ SbO ₇ itself used have no effect as a grain growth inhibitor, V _{1 mA} / t is about 380 V / mm in the former and about 440 V / mm in the latter.

Therefore, the ZnO—Bi ₂ O ₃ system voltage non-linear resistor manufactured by the manufacturing methods of Patent Documents 1 and 2 is not suitable for V _{1 mA} / t of a lightning arrester for ultra-high voltage as currently required. It was enough.

  The object of the present invention is to obtain a voltage non-linear resistor having a high sintering density and a small crystal grain size even if the amount of oxide as a grain growth inhibitor is reduced relative to the main component ZnO. The object is to provide a method of manufacturing a voltage non-linear resistor.

Another object of the present invention is to provide a voltage non-linear resistance lightning arrester having a high V _{1 mA} / t and good electrical characteristics such as VI characteristics and capacitance.

The method for producing a voltage non-linear resistor according to the present invention comprises mixing at least a zinc oxide (ZnO) powder, a cobalt (Co) compound powder, and an antimony (Sb) compound powder, and heating the mixture at a heating temperature of 950 ° C. to 1350 ° C. To produce an oxide containing Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7), finely pulverize the oxide and prepare in advance, and voltage non-linearity with the main component zinc oxide (ZnO) powder. An oxide powder containing Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7) is mixed as an additive to the additive powder in the form of a compound necessary for expression, and the mixture is pressed with a mold. It is characterized by molding and sintering the molded body.

  Preferably, when the zinc oxide (ZnO) powder, cobalt (Co) compound powder and antimony (Sb) compound powder are mixed, bismuth (Bi) compound powder, silicon (Si) compound powder, boron (B) compound powder It is characterized by adding at least one of them.

  More preferably, a manganese (Mn) compound powder, a chromium (Cr) compound powder, and a nickel (Ni) compound powder are further added to and mixed with the compound powder.

The method for manufacturing a voltage non-linear resistor according to the present invention includes mixing at least zinc oxide (ZnO) powder, cobalt (Co) compound powder, and antimony (Sb) compound powder, and mixing the mixture at 950 ° C. to 1350 ° C. An oxide containing Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7) is prepared by reacting at a heating temperature, the oxide is finely pulverized and prepared in advance, and the main component zinc oxide (ZnO) powder is added to bismuth oxide. (Bi ₂ O ₃ ) powder, cobalt oxide (Co ₃ O ₄ ) powder, manganese oxide (MnO ₂ ) powder, antimony oxide (Sb ₂ O ₃ ) powder, chromium oxide (Cr ₂ O ₃ ) powder, silicon oxide (SiO ₂ ) ₂₎ with powder a voltage nonlinearity added at the mixing ratio necessary for expression, oxide including the weight ratio of these _{Zn 7-x CoxSb2O12 (0 ≦} x ≦ 7) And mixed by adding 0.01 to 0.2, the mixture was pressure-molded at a mold, is characterized by sintering the compact.

Furthermore, the voltage non-linear resistor type lightning arrester of the present invention is manufactured by adding an oxide powder containing Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7). In addition to applying layers, electrodes are provided on the upper and lower surfaces, respectively.

According to the method for producing a voltage nonlinear resistor of the present invention, an oxide containing a grain growth inhibitor (Zn _7-x Co _x Sb _x O ₁₂ ) in an additive powder in the form of a main component ZnO powder and a compound. Therefore, even in the fine particle state, the grain growth inhibitor can be present thermally and stably throughout the firing process. For this reason, the fine particles work as densification of the compact during the sintering of the mixture, and act as particles for suppressing grain boundary migration during the grain growth process, so a sintered compact with a high sintering density and a small crystal grain size can be obtained. Obtainable. In addition, since the oxide containing a grain growth inhibitor prepared in advance is used in the form of fine particles, there is an advantage that the amount of addition to the main component ZnO can be suppressed lower than that conventionally known. .

Further, when a lightning protection element is configured using a voltage nonlinear resistor as in the present invention, the voltage nonlinear resistance lightning protection element has a high V _{1 mA} / t and good electrical characteristics such as VI characteristics and capacitance. And an overvoltage protection device such as a lightning arrester for ultra-high voltage can be reduced in size.

(A) to (b) are process diagrams showing a method for manufacturing a voltage non-linear resistor according to an embodiment of the present invention. It is a schematic longitudinal cross-sectional view which shows the voltage non-linear resistance lightning arrester of one Example of this invention.

  Hereinafter, a method for manufacturing a voltage non-linear resistor and a voltage non-linear resistance lightning arrester according to the present invention will be described with reference to FIGS. In this voltage non-linear resistor manufacturing method, when roughly divided, a step S1 for preparing and preparing the grain growth inhibitor of FIG. 1 (a) and a step S2 for manufacturing the voltage non-linear resistor of FIG. 1 (b). It is made up of.

For production of a grain growth inhibitor, as shown in step S1 of FIG. 1 (a), first, a predetermined proportion of ZnO powder, Sb ₂ O ₃ powder and Co ₃ O ₄ powder is produced for production of a grain growth inhibitor. Are mixed and ground using a mixing and crushing means such as a ball mill (step S1a).

Subsequently, the mixture placed in a reaction vessel such as an alumina crucible is reacted by holding it in a heating furnace at, for example, 950 ° C. for 2 hours, and becomes a grain growth inhibitor Zn _7-x Co _x Sb ₂ O ₁₂ ( Hereinafter, it is referred to as “specific grain growth inhibitor”) (step S1b). The produced oxide containing the specific type grain growth inhibitor is pulverized to a few μm or less by a crushing means, and is preliminarily stored as a powder after drying by, for example, freeze drying (step S1c).

When creating the specific type grain growth inhibitors, other easily produce a glass material _{Bi 2 O 3, SiO 2,} B 2 O may be further added at least one of the _three, or even MnO ₂ , Cr ₂ O ₃ , NiO or the like may be added within the range in which the glass material is vitrified.

In the above steps S1a, but is a mixture with the addition of Co ₃ O ₄ powder and Sb ₂ O ₃ powder, since the mixture is intended to be heat reaction treatment, the oxide in the course of the reaction As long as it is, even Co compounds and Sb compounds in other forms can be used.

  Moreover, although the reaction temperature which the above-mentioned specific type grain growth inhibitor produces is an example of 950 ° C., the reaction temperature can be synthesized in the range of 950 ° C. to 1350 ° C. In addition, the reaction time is not limited to holding for 2 hours, and a holding time capable of producing a specific grain growth inhibitor having a good grain growth inhibiting effect can be selected.

  Of course, the above-mentioned mixing and crushing means can be used not only for a ball mill if it can be sufficiently mixed and pulverized, and if the oxide containing a specific type grain growth inhibitor can also be sufficiently dried, other means can be used. Can be used.

  Then, a voltage nonlinear resistor is manufactured as shown in step S2 of FIG. First, when manufacturing, when mixing the main component ZnO powder and additive powders in the form of compounds such as Bi, Sb, Co, Mn, Cr, Ni, Si, Al, etc., which are generally used, The oxide powder containing the specific type grain growth inhibitor having a weight ratio of 0.01 to 0.2 is added, and water containing the binder is added in the same manner as usual, and sufficiently mixed by the mixing means (step S2a). ). The resulting mixture is put into a mold as usual after drying, pressure-molded into a disk-shaped or donut-shaped predetermined shape (step S2b), and finally the pressure-molded product is baked. A voltage nonlinear resistor is manufactured by performing sintering in order in a sintering furnace (process S2c).

In the voltage non-linear resistor manufactured by adding the oxide containing the specific type grain growth inhibitor as described above, the specific type grain growth inhibitor exists thermally stably during the sintering of the mixture. For this reason, the fine particles of the specific type grain growth inhibitor become denser in the voltage nonlinear resistor and act as particles for suppressing grain boundary migration during the grain growth process, so that the sintered density is high and the crystal grain size is small. A sintered body of a voltage non-linear resistor can be manufactured. Therefore, the produced voltage nonlinear resistor has a high V _{1 mA} / t and good electrical characteristics such as VI characteristics and capacitance.

It has been conventionally known that Zn ₇ Sb ₂ O ₁₂ is produced in the vicinity of 900 ° C. when a ZnO—Bi ₂ O ₃ -based voltage non-linear resistor molded body produced by a general manufacturing method is heated. It is also known that Zn ₇ Sb ₂ O ₁₂ is a grain growth inhibitor. However, according to the study by the present inventors, sintering of the molded body is proceeding near 900 ° C., and the density reaches 50% of the amount of firing shrinkage, resulting in variations in crystal grain size and sintered density. It is estimated that Zn ₇ Sb ₂ O ₁₂ is produced by the reaction of eutectic liquid phase such as Zn ₂ Bi ₃ Sb ₃ O ₁₄ and ZnO.

For this reason, grain growth of Zn ₇ Sb ₂ O ₁₂ is likely to occur. Therefore, unless Zn ₇ Sb ₂ O ₁₂ is produced in a large amount according to the above formula (4), it does not act as a sufficient grain growth inhibitor. Furthermore, Zn ₇ Sb ₂ O ₁₂ is not necessarily thermally stable, and the above-described specific grain growth inhibitor in which Co is dissolved in the Zn site and partially substituted exists stably even at high temperatures. It has been found.

Therefore, the specific type grain growth inhibitor is prepared in advance as described above, and further added as a part of the additive of the ZnO-Bi ₂ O ₃ system voltage non-linear resistor, thereby producing the voltage non-linear resistor. It can be used as an ideal grain growth inhibitor.

In the production of the specific grain growth inhibitor described above, ZnO, Sb ₂ O ₃ , and Co ₃ O ₄ are further added to ZnO—Bi ₂ O ₃ system voltage non-linear resistor as an additive to vitrification. At least one of Bi ₂ O ₃ , SiO ₂ , and B ₂ O ₃ powders, which are easy substances, may be added. Further, manganese oxide MnO ₂ , Cr ₂ O ₃ , and NiO powders may be added and mixed. Can also be produced.

When the oxide vitrified in this way and the specific grain growth inhibitor coexist, the particles of the specific grain growth inhibitor are deposited on the glass-forming substance contained in the oxide. If a glass-forming substance is allowed to coexist as in this case, the preparation of the specific grain growth inhibitor is easier than when only ZnO, Sb ₂ O ₃ , and Co ₃ O ₄ powders are mixed. When the specific type grain growth inhibitor produced in this way is used as an additive during the production of the non-linear resistor, there is an advantage that a sintered body having a high density can be produced at a lower temperature by the action of the glass substance.

  The voltage non-linear resistance lightning protection element 1 is manufactured using the manufactured voltage non-linear resistance as shown in FIG. That is, the voltage non-linear resistor 2 sintered in a predetermined shape such as a disk shape or a donut shape is provided with an insulating coating of the high resistance layer 4 on the entire circumference of its side surface. Further, after polishing both end surfaces of the voltage non-linear resistor 2, electrodes 3a and 3b are formed by spraying, for example, aluminum on the polished surface.

  The voltage non-linear resistance lightning protection element 1 manufactured as described above forms an element column by stacking a plurality of sintered elements in series via the electrodes 3a and 3b in accordance with the system voltage, and this element column is used as a container. It is housed in an overvoltage protection device such as a lightning arrester.

  In the description of the following examples, the composition before adding the specific grain growth inhibitor is simply referred to as a base composition, and the weight ratio between the specific grain growth inhibitor and the base composition is simplified. Used as a grain growth inhibitor / base ratio. The voltage non-linear resistance lightning protection elements used in each example are all adjusted to have a diameter of 33 mm, an electrode diameter of 30 mm, and an element thickness of 4.0 mm.

Hereinafter, the production of a specific type grain growth inhibitor (Zn _7-x Co _x Sb ₂ O ₁₂ ) using Examples 1 to 4 and the voltage nonlinear resistor added with the powder of the specific type grain growth inhibitor These manufacturing methods will be described in order.

In the present invention, x = 3.5, which is a typical composition of the specific type grain growth inhibitor satisfying 0 ≦ x ≦ 7, that is, Zn _3.5 Co _3.5 Sb ₂ O ₁₂ (hereinafter referred to as “x3.5 specific type”). "Grain growth inhibitor") was synthesized in the following procedure and then pre-fabricated into fine particles.

Powder material weighed so that the total amount of ZnO powder was 61.8 mol%, Co ₃ O ₄ powder was 20.6 mol%, Sb ₂ O ₃ powder was 17.6 mol%, and the total amount was 20 g. Was added to a monomalon pot with a capacity of 2 L together with 1 L of pure water, and mixed and pulverized in a ball mill for 20 hours. As the grinding balls, yttria partially stabilized zirconia balls having a diameter of 5 mm were used. From the slurry after mixing and pulverization, a dry powder was obtained by freeze drying. This powder was packed in an alumina crucible, heated to 1100 ° C. at a heating rate of 600 ° C./hour in an electric furnace, and held for 2 hours. Thereafter, the heater was turned off, cooled to 300 ° C. by natural cooling, and the crucible was taken out from the electric furnace. The average particle size determined by electron microscope (SEM) observation of the obtained powder was approximately 0.5 μm.

Next, a method for producing a ZnO—Bi ₂ O ₂ -based voltage nonlinear resistor to which powder of a specific type grain growth inhibitor is prepared and added will be described.

Bi ₂ O ₂ is 0.5 mol%, Co ₃ O ₄ is 0.33 mol%, and MnO ₂ is 0 mol, which is one of the typical compositions of ZnO—Bi ₂ O ₂ voltage non-linear resistance lightning arresters. A composition of 0.5 mol%, 0.5 mol% of NiO, 0.5 mol% of Cr ₂ O ₃ , 0.25 mol% of B ₂ O ₃ and 0.5 mol% of SiO ₂ at 1300 ° C. The mixture was heat-treated for 2 hours to be completely crowed, and pulverized and dried in the same manner as described above to obtain an additive powder other than the x3.5 specific type grain growth inhibitor. A voltage non-linear resistance lightning arrester was prepared by adding an additive of this seven-component composition and an x3.5 specific grain growth inhibitor prepared by the above-described method to ZnO.

表１の各試料に示したベース組成の配合比で、これらの総量が１ｋｇになるように秤量したＺｎＯ粉末及び特定型粒成長抑制剤以外の添加物粉末に、ベース組成に対して表１の粒成長抑制剤／ベース比（重量比）になるように秤量したｘ３.５特定型粒成長抑制剤の粉末を準備した。

In the mixing ratio of the base composition shown in each sample of Table 1, the additive powder other than the ZnO powder and the specific type grain growth inhibitor weighed so that the total amount thereof becomes 1 kg was added to the base composition in Table 1. A powder of x3.5 specific type grain growth inhibitor weighed so as to have a grain growth inhibitor / base ratio (weight ratio) was prepared.

  The base composition powder and the powder of the x3.5 specific type grain growth inhibitor were charged together with 1 L of pure water in which an appropriate amount of binder was mixed in a 2 L capacity monomalon pot, and mixed and pulverized by a ball mill for 20 hours. As the grinding balls, yttria partially stabilized zirconia balls having a diameter of 10 mm were used. A dry powder was obtained from the slurry after mixing and grinding by freeze drying. This powder was molded into a disk shape using a mold having a diameter of 30 mm, and then heated to the sintering temperature shown in Table 1 at a heating rate of 100 ° C./hour in an electric furnace, and held for 2 hours. Thereafter, the heater was turned off and cooled to 300 ° C. by natural cooling, and then the sintered voltage nonlinear resistor was taken out of the electric furnace.

Table 1 shows the measured electrical characteristics of each sample of the voltage non-linear resistance lightning arrester when the grain growth inhibitor / base ratio and the sintering temperature are changed. The electrical characteristics of the voltage non-linear resistance lightning protection device are as follows: an operation start voltage V _{1 mA} / t per element thickness of 1.0 mm, a device voltage V _{10 μA} when a direct current 10 μA is passed, and a voltage V when a current 1 mA is passed. _{1 mA} ratio V _{10 μA} / V _{1 mA} , 8/20 μs impulse current 2.5 kA flowing element voltage V _{2.5 kA} to V _{1 mA} ratio V _{2.5 kA} / V _{1 mA} , capacitance Cap and voltage V1 _mA The product Cap · V _{1 mA} is shown.

Note that the ratios V _{10 μA} / V _{1 mA} and V _{2.5 kA} / V _{1 mA} represent voltage / current nonlinearity in the low current region and the large current region, respectively, and the closer to 1, the better the characteristics. . Cap · V _{1 mA} is a value obtained by standardizing the capacitance with V _{1 mA} . As this value increases, the voltage sharing ratio between the elements due to the capacitive component approaches 1 when the lightning protection elements are stacked, and the voltage load of the lightning protection elements Is alleviated and the service life is extended.

  In addition, the sintered density, which is an indicator of whether the sintered body has been burned successfully, is shown in Table 1. 1 to sample no. No. 9 and the case where the grain growth inhibitor by the conventional method is not added, the sample No. From R1, sample no. Indicated by R5.

Sample No. manufactured by adding the specific type grain growth inhibitor of the present invention. 1 to Sample No. In No. 9, a high-density sintered body having a sintering density of 5.6 to 5.7 g / cm ₂ is obtained even at a relatively low sintering temperature of 1000 to 1100 ° C. On the other hand, the sample No. in the conventional method without adding a grain growth inhibitor. From R1, sample no. R3 is not sufficiently sintered at a sintering temperature of 1000 to 1100 ° C., and has a low sintering density of about 5.0 to 5.2 g / cm ₂ . Therefore, although V _{1 mA} / t is high, V _{10 μA} / V _{1 mA} and V _{2.5 kA} / V _{1 mA} are bad values.

In order to obtain a voltage non-linear resistor having a high sintering density by the conventional method, sample No. As indicated by R4, a high temperature of about 1250 ° C. is necessary. In this case, grain growth proceeds, and as a result, V _{1 mA} / t decreases to about 200 V / mm. Sample No. As shown by R5, among the additives of the base composition, when the added amount of Sb ₂ O ₃ or SiO ₂ having a grain growth inhibiting action is increased, for example, sintering at 1150 ° C. can provide a good sintered density. However, since a large amount of insulating material can be formed in the sintered body by the reactions shown in the above formulas (1) and (2), a lightning arrester with a low Cap · V _{1 mA} value that is not desirable in terms of characteristics can be formed. become.

From the above, the voltage non-linear resistance lightning arrester prepared by adding the powder of the x3.5 specific grain growth inhibitor according to the present invention to the base composition has a high sintered density even when sintered at a low temperature. Therefore, V _{10 μA} / V _{1 mA} and V _{2.5 kA} / V _{1 mA} are both good, and the Cap · V _{1 mA} value is also large, so that V _{1 mA} / t can be increased. Therefore, it is possible to obtain a voltage non-linear resistance lightning arrester that can be expected to reduce the size of the lightning arrester corresponding to the ultrahigh voltage of the transmission system voltage.

Instead of the x3.5 specific type grain growth inhibitor shown in Example 1, a specific type grain growth inhibitor of x = 0, 2, 5, and 7 was prepared, and this was converted into a powder having a base composition with the inhibitory particle / base. A voltage non-linear resistance lightning protection element was prepared by adding a ratio of 0.1. The sintering temperature at this time is 1050 ° C. The specific grain growth inhibitor was prepared by changing the ZnO, Co ₃ O ₄ , and Sb ₂ O ₃ mixing ratio to a mixing ratio corresponding to the value of x.

  Table 2 shows the electrical characteristics and the sintered density corresponding to each value of x.

この表２には、ｘ＝３．５としたｘ３.５特定型粒成長抑制剤を用いた表１の試料Ｎｏ．８も再掲載している。表２から明らかなように、各試料ではｘの値が０から７のどの範囲でも、実施例１で説明したものと同様に高焼結密度にでき、同様な効果が達成できた。

Table 2 shows the sample No. in Table 1 using x3.5 specific grain growth inhibitor with x = 3.5. 8 is also reprinted. As is clear from Table 2, in each sample, the value of x was in any range from 0 to 7, and as in the case described in Example 1, it was possible to achieve a high sintered density and achieve the same effect.

In this example, instead of the x3.5 specific type grain growth inhibitor shown in Examples 1 and 2, a specific type grain growth inhibitor was produced by the method described below. That is, ZnO, Co ₃ O ₄ , Sb ₂ O ₃ mol%, SiO ₂ , B ₂ O ₃ %, and Bi ₂ O ₂ were weighed so that the total amount thereof was 1 kg at the blending ratio shown in Table 3. These powders were put into a monomalon pot with a capacity of 2 L together with 1 L of pure water, and mixed and pulverized in a ball mill for 20 hours. As the pulverizing balls, yttria partially stabilized zirconia balls having a diameter of 5 mm were used, and the slurry after mixing and pulverization was dried by freeze drying to obtain a dry powder.

  This powder was formed into a cylindrical shape having a diameter of 50 mm and a thickness of 50 mm, placed in an alumina sheath, heated to 1300 ° C. at a heating rate of 100 ° C./hour in an electric furnace, and held at this temperature for 2 hours. Thereafter, the heater was turned off, cooled to 300 ° C. by natural cooling, and the alumina sheath was taken out from the electric furnace. When this powder was examined by X-ray diffraction (XRD), only the component peak of the specific type grain growth inhibitor was observed.

  The x3.5 specific grain growth inhibitor and glass oxide obtained by the above procedure were pulverized again by the above-described ball mill and dried by freeze drying. The average particle size determined by electron microscope (SEM) observation of the obtained powder was approximately 0.5 μm. A lightning arrester was prepared by the method shown in Example 1 by blending at a grain growth inhibitor / base ratio of 0.10. The sintering temperature was 1050 ° C.

表３に、ＺｎＯ、Ｓｂ_２Ｏ_３、Ｃｏ_３Ｏ_４、ＳｉＯ_２、Ｂ_２Ｏ_３、Ｂｉ_２Ｏ_３の表中記載の組成（モル％）で、作成する酸化物中にガラス化酸化物と特定型粒成長抑制剤を共存させて製造した試料Ｎｏ．１４から試料Ｎｏ．３１について、測定した電気的特性及び焼結密度を示している。これから、ガラス酸化物が共存する場合でも、本発明の効果が得られることは明らかである。

Table 3 shows the composition (mol%) described in the table of ZnO, Sb ₂ O ₃ , Co ₃ O ₄ , SiO ₂ , B ₂ O ₃ , Bi ₂ O ₃ , and a vitrified oxide in the prepared oxide. Sample No. manufactured by coexisting with a specific grain growth inhibitor. 14 to sample no. About 31, the measured electrical property and sintered density are shown. From this, it is clear that the effects of the present invention can be obtained even when glass oxide coexists.

  In this example, the synthesis (sintering) temperature is 1250 ° C. 15, Sample No. As shown by 16, the effect of the present invention can be obtained even if the synthesis temperature is increased to 1350 ° C. When the synthesis temperature is 1250 ° C. or lower, the glass material does not react sufficiently and is likely to be non-uniform. When the synthesis temperature is 1350 ° C. or higher, the entire sintered body is softened and the reaction with the alumina sheath is remarkable. It is not a good idea to synthesize at temperature.

  Sample No. 17 to sample no. As indicated by 31, the same effect can be obtained even when x in the specific grain growth inhibitor is not limited to 3.5, and x = 2 or 5. Combined with this and the results of Example 2 above, the method of the present example also provides the effects of the manufacturing method of the present invention within the range of 0 ≦ x ≦ 7.

  In Example 3 above, as a result of analysis by energy dispersive X-ray fluorescence analysis (EDX), a phenomenon was observed in which the value of x of the inhibitory particles of the blended specific grain growth inhibitor increased, and the glass oxide Zn was detected in it. From this, it was estimated that a part of ZnO mix | blended for grain growth inhibitor formation melt | dissolved in the glass oxide. For this reason, when the experiment was repeated so as to obtain an x value as designed, if the ZnO to be blended is further increased so that the glass oxide is included in the range of 1 to 2 with respect to the saturation amount of Zn, It has been found that a predetermined x can be obtained.

  According to the method of increasing the amount of ZnO, it is possible to obtain a grain growth inhibitor having a desired x value even when glass oxide coexists, and to reduce variation in electrical characteristics of the voltage nonlinear resistor, as described above. The effect of the present invention can be further enhanced.

  Although not shown as examples, the glass oxides shown in examples 3 and 4 are not limited to Si, B, and Bi, and do not impair the electrical characteristics and sinterability of the voltage non-linear resistance lightning arrester. Even if it mixes and manufactures Mn, Ni, Cr, Al, Ag, etc. which form a glass substance in the range, the effect of the present invention can be achieved.

S 1, S 1 a, S 1 b, S 1 c, S 2, S 2 a, S 2 b, S 2 c,..., 1, voltage nonlinear resistance lightning protection element, 2, voltage nonlinear resistor, 3 a, 3 b, electrode, 4, high resistance layer.

Claims (5)

At least zinc oxide (ZnO) powder, cobalt (Co) compound powder and antimony (Sb) compound powder are mixed, and the mixture is reacted at a heating temperature of 950 ° C. to 1300 ° C. to obtain Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7) is prepared, the oxide is finely pulverized, prepared in advance, and additive powder in the form of a compound necessary to develop voltage nonlinearity with the main component zinc oxide (ZnO) powder In addition, an oxide powder containing Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7) is mixed as an additive, the mixture is pressure-molded in a mold, and the molded body is sintered. A method for manufacturing a voltage non-linear resistor.   2. The bismuth (Bi) compound powder, silicon (Si) compound powder, boron (B) when the zinc oxide (ZnO) powder, cobalt (Co) compound powder and antimony (Sb) compound powder are mixed. A method for producing a voltage nonlinear resistor, comprising adding at least one of compound powders.   3. The method of manufacturing a voltage nonlinear resistor according to claim 2, wherein manganese (Mn) compound powder, chromium (Cr) compound powder, and nickel (Ni) compound powder are further added to and mixed with the compound powder. At least zinc oxide (ZnO) powder, cobalt (Co) compound powder and antimony (Sb) compound powder are mixed, and the mixture is reacted at a heating temperature of 950 ° C. to 1300 ° C. to obtain Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7) is prepared, the oxide is finely pulverized and prepared in advance, and the main component zinc oxide (ZnO) powder is added to bismuth oxide (Bi ₂ O ₃ ) powder, cobalt oxide (Co ₃ O _4). ) Powder, manganese oxide (MnO ₂ ) powder, antimony oxide (Sb ₂ O ₃ ) powder, chromium oxide (Cr ₂ O ₃ ) powder, silicon oxide (SiO ₂ ) powder are necessary to develop voltage nonlinearity with added in compounding ratio, the oxide added and mixed 0.2 0.01 including the weight ratio of these _{Zn 7-x CoxSb2O12 (0 ≦} x ≦ 7), the mixed Things were pressure-molded at a mold manufacturing method of the voltage nonlinear resistor, characterized by sintering the compact. The voltage nonlinear resistor manufactured by adding the oxide powder containing Zn _7-x CoxSb 2 O 12 (0 ≦ x ≦ 7) by the manufacturing method according to claim 1 is provided with a high insulating layer on a side surface. In addition, a voltage non-linear resistance type lightning protection element, characterized in that electrodes are provided on the upper and lower surfaces respectively.

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