JP2850525B2 - Zinc oxide varistor, method for producing the same, and crystallized glass composition for coating oxide ceramic - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a zinc oxide varistor mainly used in the electric power field, a method for producing the same, and a crystallized glass composition for coating an oxide ceramic.

Conventional technology Zinc oxide varistors containing ZnO as a main component and metal oxides of various types including Bi ₂ O ₃ , CoO, Sb ₂ O ₃ , Cr ₂ O ₃ , and MnO ₂ as sub-components have a large surge withstand capability. It is well known that it has been widely used in recent years as an element for a gapless arrester instead of a conventional silicon carbide varistor.

Conventionally, as a method for manufacturing a zinc oxide varistor, for example, Japanese Patent Application Laid-Open No. 62-101002 has been disclosed. The contents of the above-mentioned prior art are as follows. First, the main component Zn
O is mixed with a raw material powder in which metal oxides such as Bi ₂ O ₃ , Sb ₂ O ₃ , Cr ₂ O ₃ , CoO, and MnO ₂ are added in an amount of 0.01 to 6.0 mol%,
Granulate, press and form this granulated powder into a columnar shape,
Bake at 1200 ° C for 6 hours. Next, a glass paste made of a PbO-based glass frit containing 60% by weight of PbO, 80% by weight of a PbO-based glass frit, 20% by weight of feldspar, and an organic binder was applied to a side surface of the obtained sintered body by a screen printing machine. 5-500 mg / cm ²
After the application, a baking treatment is performed. The both end faces of the element thus obtained are polished in a plane, an aluminum metallikon electrode is formed, and a zinc oxide varistor is obtained.

However, since the zinc oxide varistor according to the conventional manufacturing method uses a screen printing method, the thickness of the side glass layer is uniformly formed, and the zinc oxide varistor has the advantage of having a small variation in discharge capability. Since it is a composite glass of a PbO-based glass frit and feldspar, it has a drawback that the discharge withstand capability is low, the voltage non-linearity is reduced during the glass baking treatment, and the charge life is deteriorated.

An object of the present invention is to provide a highly reliable zinc oxide varistor and a method for producing the same, and a crystallized glass composition for coating generally used for oxide-based ceramics. is there.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned conventional problems, at least Fe ₂ O ₃ is 0.1 to 5.
The structure has a side surface high resistance layer made of crystallized glass containing PbO containing 0% by weight as a main component. Further, P containing at least 0.1 to 5.0% by weight of Fe ₂ O ₃ on the side surface of the sintered body.
A glass paste consisting of crystallized glass and an organic binder mainly comprising bO 10.0~150.0mg / cm ² was applied, 450-60
The baking treatment is performed in a temperature range of 0 ° C. to form a high resistance side surface layer.

Further, at least Fe ₂ O ₃ for the side high resistance layer is 0.1 to
5.0 there is provided a _{PbO-ZnO-B 2 O 3} -SiO 2 -Fe 2 O 3 based oxide crystallized glass composition for a ceramic coating comprising by weight%.

Action According to the present invention, compared to PbO-feldspar-based composite glass, crystallized glass containing PbO as a main component promotes crystallization by addition of Fe ₂ O ₃ and strength of a coating film by addition of SiO _2. And has good adhesion to the sintered body, so it has excellent discharge withstand characteristics, and because of its high insulation properties, it is possible to minimize the decrease in voltage non-linearity during the baking process, and to improve the electrical life. A highly reliable zinc oxide varistor excellent in characteristics can be obtained.

EXAMPLES Hereinafter, the zinc oxide varistor of the present invention, the method for producing the same, and the crystallized glass composition for coating will be described in detail based on examples.

First, 0.5 mol% of Bi ₂ O ₃ and C
o ₂ O ₃ 0.5 mol%, MnO ₂ 0.5 mol%, Sb ₂ O ₃ 1.0 mol%, Cr ₂ O
₃ 0.5 mol%, NiO0.5 mol%, SiO ₂ 0.5 mol% was added, pure water, a binder, thoroughly mixed in with a dispersant such as a ball mill, was pulverized, dried with a spray dryer, and granulated material Powder was obtained. This raw material powder was compression-molded to a size of 40 mm in diameter and 30 mm in thickness and degreased under a temperature condition of 500 ° C. or more. Then, it was fired in a temperature range of 1100 to 1250 ° C. to obtain a sintered body.

On the other hand, the crystallized glass for coating is PbO, ZnO, B ₂ O ₃ , SiO ₂ , Fe
_A predetermined amount of ₂ O ₃ was weighed, mixed and pulverized by, for example, a ball mill, then melted in a platinum crucible at a temperature of 1000 to 1200 ° C., rapidly cooled, and vitrified. After coarsely pulverizing this glass, it was pulverized with a ball mill to obtain a glass frit.
In addition, 70.0% by weight of PbO, ZnO 2
Glass frit 8 consisting of 5.0% by weight and 5.0% by weight of B ₂ O ₃
Feldspar 0.0% by weight (feldspars are KAlSi ₃ O ₈ , NaAlSi ₃ O ₈ , CaAl ₂ Si ₂
A composite glass consisting of 20.0% by weight of a solid solution of O ₈ ) was produced in the same process.

The composition, glass transition point (Tg), linear expansion coefficient (α), and crystallinity of the glass frit prepared as described above are shown in Table 1 below.

In Table 1, the glass transition point Tg and the coefficient of linear expansion α were measured using a thermal analyzer. The crystallinity was observed by observing the surface state of the glass with a metallographic microscope or an electron microscope. Samples with high crystallinity were marked with a circle, and those without any crystal were marked with a cross.

According to Table 1, when the added amount of PbO is large, the linear expansion coefficient (α) becomes high, and when the added amount of ZnO is large, the glass transition point (Tg) becomes low and crystallization becomes easy. Also, B ₂ O ₃
When the addition amount is large, the glass transition point increases, and when the addition amount exceeds 15.0% by weight, crystallization becomes difficult. Further, as the amount of added SiO ₂ increases, the glass transition point tends to increase, and the coefficient of linear expansion tends to decrease.
Then, as the amount of Fe ₂ O ₃ added increased, the crystallization of the glass progressed. Further, in a system containing less PbO and B ₂ O ₃ , a porous glass was easily formed.

Next, 85% by weight of this glass frit and 15% by weight of an organic binder (a mixture of ethyl cellulose and butyl carbitol acetate) were sufficiently mixed, for example, by a three-roll mill to obtain a glass paste for coating. The glass paste for coating is applied to a 125
Printing was performed on the side surface of the sintered body using a screen of 250250 mesh. Here, the application amount of the glass paste for coating was determined from the difference in weight of the sintered body after the paste was applied and dried at 150 ° C. for 30 minutes. The coating amount was adjusted by adding an organic binder and n-butyl acetate to the glass paste for coating. Thereafter, the coating glass paste was baked under a temperature condition of 350 to 700 ° C. to form a high-side resistance layer on the sintered body. Next, both end surfaces of the sintered body were polished to form an aluminum metallikon electrode to obtain a zinc oxide varistor.

FIG. 1 shows a sectional view of the zinc oxide varistor according to the present invention obtained as described above. In FIG. 1, 1 is a sintered body containing zinc oxide as a main component, 2 is an electrode formed on both end surfaces of the sintered body 1, and 3 is a crystallized glass on a side surface of the sintered body 1 by baking crystallized glass. It is a side surface high resistance layer obtained.

Next, Table 2 below shows the appearance, V _{1 mA} / V _{10 μA} , discharge withstand _voltage characteristics, and charging life characteristics of zinc oxide varistors prepared using the coating glass of Table 1. Here, the viscosity of the paste was controlled so that the coating amount of the coating glass paste was 50 mg / cm ² . The baking condition is 55
0 ° C., 1 hour. Here, the number of samples is n = 5 for each lot.
Individual. V _{1 mA} / V _{10 μA} was measured using a DC constant current power supply. The discharge withstand characteristics are as follows. Impulse current of 4 / 10μS is applied twice in the same direction at 5 minute intervals, step up from 40kA, and visually check for abnormalities in appearance. It examined using. Here, ○ in the table
The mark indicates that no abnormality was observed in the sample after applying the predetermined current twice, the mark Δ indicates that abnormality was observed in 1 to 2 pieces, and the cross mark indicates that abnormality was recognized in 3 to 5 pieces. I have. Further, the application life characteristics were performed under the conditions of an ambient temperature of 130 ° C. and an application rate of 95% (AC, peak value), and the time until the leakage current reached 5 mA (peak value) was measured. In addition, V _1mA / V _{10 μA} and the service life are shown by the average value of five _devices .

The above-mentioned number of samples, the method of measuring V _{1 mA} / V _{10 μA} , the method of testing the discharge capability, and the method of evaluating the charge life characteristics are the same in each of the following examples unless otherwise specified.

From Tables 1 and 2, when the coefficient of linear expansion of the coating glass is smaller than 65 × 10 ^-7 / ° C (G1, G5 glass), the glass is easily peeled and exceeds 90 × 10 ^-7 / ° C. In the case of (G4 glass), cracks are easily generated. It is considered that the sample in which these cracks and glass peeling have low discharge withstand characteristics because the insulating property of the side high-resistance layer is poor. In addition, the coefficient of linear expansion of the coating glass is 65 to 90 × 10 ⁻⁷ /
Glass with poor crystallinity even in the range of ° C (G8 glass)
With regard to (1), cracks are likely to occur and the discharge withstand characteristics are low. This is presumably because crystalline glass has a higher coating film strength than amorphous glass. Further, the addition of ZnO does not significantly affect the electrical characteristics and reliability of the zinc oxide varistor, and helps to lower the glass transition point even in the physical properties of glass. In addition, PbO-ZnO-B
_In the case of using ₂ O ₃ and feldspar composite glass, it can be seen that the charging service life characteristic is at a practical level but the discharge withstand characteristic is low.

Next, the amount of Fe ₂ O ₃ added will be considered. First, Fe ₂ O ₃
In the composition system containing 0.1% by weight or more, the voltage non-linearity is improved in any of the composition systems, and the charging life property is accordingly improved. It is Fe ₂ O ₃ 0.1% by weight
This is presumably because the above addition causes Fe ₂ O ₃ to slightly diffuse into the sintering resistant surface during the glass baking treatment, thereby increasing the resistance of the ZnO particles. On the other hand, the addition amount of Fe ₂ O ₃ is 5.0% by weight.
If it is larger, the discharge withstand characteristics are low. This is considered to be because the fluidity of the glass during the baking process is poor, and the glass tends to be porous. Accordingly, in the _{PbO-ZnO-B 2 O 3} -SiO 2 -Fe 2 O 3 type crystallized glass for the side surface high-resistivity layer of zinc oxide varistor is a composition system comprising at least a Fe ₂ O ₃ 0.1 to 5.0 wt% Is a necessary condition.

From the above results, the composition of the crystallized glass for coating is PbO
55.0-75.0% by weight, ZnO 10.0-30.0% by weight, B ₂ O ₃
5.0-10.0 wt%, SiO ₂ is 0 to 15.0 wt%, Fe ₂ O ₃ 0.1
It turns out that the range of -5.0% by weight is optimal. Also,
For the side surface high resistance layer of the zinc oxide varistor, the linear expansion coefficient needs to be in the range of 65 to 90 × 10 ⁻⁷ / ° C.

Next, the application amount of the glass paste was examined using the G16 glass of Table 1 which is an example of the present invention. The results are shown in Table 3 below. At this time, the application amount of the glass paste was 1.0
〜300.0 mg / cm ^2, which was controlled by the viscosity of the paste and the number of applications. In this case, if the coating amount is less than 10.0 mg / cm ^2, the strength of the coating film is low, also the coating amount is 150.0m
When the amount is more than g / cm ² , the glass tends to flow and pinholes are easily generated, so that the discharge capability is poor. Therefore, it is understood that the optimal amount of the glass paste applied is in the range of 10.0 to 150.0 mg / cm ² .

Next, using the G16 glass shown in Table 1 as an example of the present invention, the baking conditions of the glass paste were examined. The results are shown in Table 4 below. At this time, the viscosity was controlled so that the application amount of the glass paste was 50.0 mg / cm ² . Further, the baking treatment of the glass paste was performed in air at a temperature range of 350 to 700 ° C. with a holding time of 1 hour. As a result,
When the baking process is performed at a temperature lower than 450 ° C, the glass paste does not melt sufficiently and the discharge withstand capability is low.
When the baking treatment is performed at a higher temperature, the voltage ratio is remarkably reduced, and the charging life characteristic is deteriorated. Therefore, it is understood that the optimal temperature range for the baking treatment of the glass paste is 450 to 600 ° C.

_{Incidentally, PbO-ZnO-B 2 O} 3 -Fe in this embodiment ₂ O _3, PbO-Zn
The crystallized glass for coating of four-component and five-component system of O—B ₂ O ₃ —SiO ₂ —Fe ₂ O ₃ has been described. As the sixth component, a trace additive that further promotes the crystallization of glass, for example, Al ₂ O ₃ , SnO ₂
The effect of the present invention does not change even if such an additive is added. Also,
As the substance that lowers the glass transition point,
ZnO was used, but of course it could be replaced with other substances. Further, in this embodiment,
Representative examples of oxide ceramics, was used _{PbO-ZnO-B 2 O 3} -SiO 2 -Fe 2 O 3 systems covering the crystallized glass of the present invention zinc oxide varistor, of strontium titanate varistors The present invention can be applied to any oxide ceramic such as a barium titanate-based capacitor, a positive temperature coefficient thermistor, and a metal oxide type negative temperature coefficient thermistor.

According to the present invention as described above the effect of the invention, ₂ PbO-ZnO-B comprises at least an Fe ₂ O ₃ 0.1 to 5.0% by weight on the side surfaces of the sintered body containing zinc oxide as the main component O ₃ -SiO ₂ - By baking the crystallized glass for coating Fe ₂ O ₃ -based oxide ceramics at a temperature of 450 to 600 ° C., a zinc oxide varistor having excellent discharge withstand characteristics and charge-life characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zinc oxide varistor according to an embodiment to which the production method of the present invention and the crystallized glass for coating of the present invention are applied. 1 ... sintered body, 2 ... electrode, 3 ... side surface high resistance layer.

Claims (6)

(57) [Claims] 1. A sintered body containing zinc oxide as a main component and having a varistor characteristic on the side surface of the sintered body itself.
A zinc oxide varistor having a lateral high resistance layer made of crystallized glass containing PbO as a main component and containing 0.1 to 5.0% by weight in terms of Fe ₂ O ₃ . 2. A side high-resistance layer is composed of _{PbO-ZnO-B 2 O 3} -Fe 2 O 3 based crystallized glass claim 1 zinc oxide varistor according. 3. A side surface high resistance layer is _{PbO-ZnO-B 2 O 3} -SiO 2 -Fe
_The zinc oxide varistor according to claim 1, wherein the zinc oxide varistor is made of ₂ O ₃ -based crystallized glass. 4. A sintered body having zinc oxide as a main component and having a varistor characteristic, at least iron oxide is formed on a side surface of the sintered body.
Glass paste consisting of crystallized glass containing PbO as a main component containing 0.1 to 5.0% by weight in terms of Fe ₂ O ₃ and organic matter
A method for producing a zinc oxide varistor in which 10.0 to 150.0 mg / cm ^{2 is} applied and baked in a temperature range of 450 to 600 ° C. 5. The crystallized glass has a linear expansion coefficient of 65 to 90 × 10 ^−7.
The method for producing a zinc oxide varistor according to claim 4, wherein the temperature is / C. 6. PbO 55.0 to 75.0 wt%, ZnO 10.0 to 30.0 wt%, B ₂ O ₃ 5.0~15.0 wt%, SiO ₂ 0 to 15.0 wt%, Fe ₂ O ₃ 0.1~5.0 oxide consisting wt% Crystallized glass composition for ceramic coating.