JP2001155908A - Zinc oxide porcelain composition, manufacturing method therefor and zinc oxide varistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zinc oxide porcelain composition and its manufacturing method, where zinc oxide varistor which has superior electrical characteristics and high reliability with respect to DC load and surge load, and is stable with respect to heat treatment and can be baked at 750-1,200 deg.C, especially at a low temperature at or lower than 1,000 deg.C. SOLUTION: A mixture, containing at least bismuth oxide and antimony oxide, is subjected to high-temperature heat treatment of sintering or melting, cooled and smashed, and oxide synthetic is obtained. Oxide synthetic is added in zinc oxide powder together with at least two kinds of oxides selected from among boron oxide, bismuth oxide, cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide and yttrium oxide, and aluminum oxide, are mixed and pressure-molded into a disk shape and sintered, to obtain a zinc oxide porcelain composition. Electrodes are formed on both the surfaces of the disk, lead wires are attached to the electrodes, and the varistor of a disk type is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a porcelain composition for a zinc oxide varistor used for absorbing surges in an electric circuit, a method for producing the same, and a zinc oxide varistor.

[0002]

2. Description of the Related Art A zinc oxide varistor is formed by molding a zinc oxide raw material powder containing ZnO, basic additives Bi ₂ O ₃ , MnO and CoO, and various oxides added for improving the performance. It is manufactured by forming electrodes on a zinc oxide-based porcelain composition obtained by firing. The current-voltage (IV) characteristic of a zinc oxide varistor is often expressed by an approximate expression of I = (V / C) α. In this equation, C and α are element constants,
When the nonlinear resistance index α has a large value, the applied voltage
It shows that the current I increases rapidly when V exceeds the value of C. α takes different values depending on the current range, and does not always take a constant value for one element. Therefore, for each current range, for example, _0.1mA α _1mA
And so on. The rising voltage of a varistor refers to a voltage between both terminals when a current of 1 mA flows through the varistor, and is often expressed as V _{1 mA} . The voltage between both terminals when a current of 1 mA flows through a sample having a thickness of 1 mm is defined as one of the constants of this material, and is expressed as V _{1 mA} / mm.
It is known that the rising voltage of the zinc oxide varistor increases almost in proportion to the number of grain boundaries between zinc oxide and zinc oxide in the zinc oxide sintered body existing between the electrodes. That is, the rise voltage per grain boundary increases by 3 to 4 volts. Therefore, in order to manufacture a zinc oxide varistor for a high voltage of about 300 to 400 V per 1 mm in thickness, it is necessary to manufacture a sintered body having ZnO particles having a small average particle diameter of about 5 to 20 μm. It is. Therefore, conventionally, zinc oxide varistors for high voltage use a small amount of Bi ₂
O ₃ , Cr ₂ O ₃ , CoO, MnO, NiO and other oxide powders are added, and ZnO particles such as Sb ₂ O ₃ powder are added and a grain growth inhibitor is added and calcined. Manufactured using methods that inhibit growth. Sb ₂ O ₃ also plays an important role in stabilizing the nonlinear resistance characteristics of zinc oxide varistors. Conventionally, high-performance, high-performance zinc oxide varistors
It was fired at a high sintering temperature of 150 ° C. to 1300 ° C. and had considerably excellent electrical properties.

[0003] In addition, a zinc oxide varistor has excellent electrical characteristics, for example, when it has a nonlinear resistance index of _{0.1 mAα.
It} has excellent non-linear resistance, such as a high value of _{1 mA,} so that the terminal voltage does not increase rapidly even when a high current flows. It is also important that the leakage current when applying a voltage is small. For this purpose, the nonlinear resistance characteristics are excellent in the low current range, and V _{1 mA} / V
_0.01mA takes a value of 1.045 to 1.15 close for example 1, and the like. In addition, excellent reliability means that a DC voltage is applied for a long time, an AC voltage is applied, a power load is applied for a long time at a high temperature, and a pulse is applied. In addition, there is such a problem that the electric characteristics are hardly lowered and the original electric characteristics are maintained.

[0004]

Problems to be solved by the present invention
High performance zinc oxide varistors are 1150 ° C to 1300
It was fired at a high sintering temperature of ° C. There are two major problems to be solved in the ZnO varistor obtained at such a high temperature. One of the problems is that the firing temperature is high, and there is a problem that the firing temperature is lowered. Another problem is that the electrical characteristics of the varistor tend to fluctuate and become unstable due to voltage application or heat treatment, so that the varistor is stabilized.

In the conventional production method, a small amount of Bi ₂ O ₃ powder, Cr ₂ O ₃ powder, CoO powder, MnO powder, NiO powder is added to ZnO powder.
In the method of adding powder, oxide powder such as Sb ₂ O ₃ powder and pressing and firing, if the firing temperature is lowered to 1150 ° C. or less, sufficient sintering is not performed and the nonlinear resistance characteristics And the electrical characteristics as a varistor were unstable. There it was fired at a high temperature. The high sintering temperature not only causes an increase in power consumption for firing, but also causes severe scattering of Bi ₂ O _{3 and the} like and corrosion of furnace materials and containers, and thus,
There has been a demand for a lower sintering temperature. That is, when firing at these high temperatures, evaporation of Bi ₂ O _{3 and the} like is active in the atmosphere. Further, Bi ₂ O ₃ easily reacts with many kinds of substances and easily corrodes many substances such as ceramic materials of furnace materials and containers. In addition, in high-temperature sintering, differences in temperature, temperature rising rate, etc. tend to occur depending on the location of the object to be fired in the furnace, and differences in the vapor pressure of Bi ₂ O ₃ and Sb ₂ O ₃ easily occur. However, it is difficult to keep this uniform, and the electrical characteristics and the like tend to vary. When the sintering temperature is lowered to 1150 ° C. or lower by the conventional manufacturing method, the following may be considered as reasons why sufficient sintering is not performed. That is, in the zinc oxide varistor of the system to which Bi ₂ O ₃ is added, Sb ₂ O ₃ is added for the purpose of improving and stabilizing the characteristics, but Sb ₂ O ₃ sublimates at a low temperature in the firing process and ZnO covering the surface of the particles and react with ZnO with heating to form a ZnO-Sb ₂ O ₃ system or _{Bi 2 O 3 -ZnO-Sb 2} O 3 based coating, and ZnO particles
It functions to hinder the contact of ZnO particles and suppress the grain growth of ZnO. When the film containing Sb ₂ O ₃ is heated to a high temperature of about 1150 ° C., it becomes a granular spinel phase and a Bi ₂ O ₃ liquid phase,
For the first time, grain growth is promoted and sintering proceeds. Thus, with the conventional manufacturing method, it has been difficult to manufacture a good sintered body at a temperature of 1150 ° C. or lower.

Next, Zn produced by a high-temperature sintering method
O varistors were inherently accompanied by instability in electrical properties. The following can be considered as the cause. That is, in ZnO particles generated at a high temperature in the atmosphere, interstitial Zn atoms are formed between ZnO crystal lattices, and the interstitial Zn atoms act as donors to supply electrons to the conduction band, and zinc oxide becomes n. -Type semiconductor. Z
It is said that the concentration of interstitial Zn atoms in nO decreases as the oxygen partial pressure in the atmosphere increases, and increases as the atmosphere temperature increases. Such ZnO powder Bi ₂ O _3, CoO, etc. was added MnO, when sintered at a high temperature atmosphere and pressure molding, ZnO varistors are obtained having a very high nonlinear resistance characteristics. At the grain boundaries of these sintered bodies, conduction electrons in ZnO on both sides of the grain boundaries are captured by the grain boundaries, so that a depletion layer is formed on both sides of the grain boundaries, preventing electron transfer on both sides of the grain boundaries A barrier is formed. A so-called double Schottky barrier is formed. Since the main electric conduction of n-type ZnO semiconductor is conduction electrons generated from interstitial Zn atoms, interstitial Zn atoms with positive charge remain in the depletion layer . Even when no voltage is applied to the sintered body from the outside, a strong electric field is acting in the depletion layer, and the positively charged interstitial Zn atoms in the depletion layer exert an attractive force toward the grain boundary. is recieving. When a voltage is applied to such a sintered body from the outside, the voltage is applied only to the thin depletion layer, so that a larger electric field acts in one depletion layer, and the interstitial Zn atom becomes Since it is relatively easy to move, a part thereof moves toward the grain boundary and reaches the grain boundary. Then, the positively charged interstitial Zn atoms combine with the negatively charged oxygen atoms to form neutral ZnO. At the same time, the negative charge trapped at the grain boundaries is reduced, so that the barrier that has provided the varistor characteristics is lowered, and the nonlinear resistance characteristics are reduced. As described above, even when no voltage is applied to the sintered body from the outside, a strong electric field is acting in the depletion layer, and the positively charged interstitial Zn atoms in the depletion layer are It is attracted to grain boundaries. In such a situation, when the element is heated, the interstitial Zn atoms are likely to move due to the heat, and a part of the element moves toward the grain boundary due to the electric field, and has a negative charge at the grain boundary. Neutral Zn bonded to oxygen atom
O is formed to reduce the nonlinear resistance characteristics of the varistor.
As described above, the conversion of ZnO crystal into a semiconductor was mainly caused by interstitial Zn atoms naturally occurring in the manufacturing process, and was accompanied by electrical instability.

On the other hand, the conversion of ZnO crystal into an n-type semiconductor is as follows.
It was also performed by the addition of Al ₂ O ₃ . In particular, Al ₂ O ₃ was added to improve the current-voltage nonlinear resistance in the high current region. Improvement of the current-voltage nonlinear resistance in the high current region can be achieved by lowering the electric resistance in the ZnO particles. The reduction of the electrical resistance in the ZnO particles was performed by doping Al ₂ O ₃ as a donor of the n − type semiconductor ZnO. When Al ₂ O ₃ is added, the nonlinear resistance characteristics in a high current region are improved, but at the same time, the nonlinear resistance characteristics in a low current region are reduced. Even when Al ₂ O ₃ is added, if there is a positively charged interstitial Zn atom in the depletion layer,
As in the case where Al ₂ O ₃ is not added, there is a problem that the barrier is lowered at the time of voltage application or heat treatment, and the wetting current is increased. As described above, an increase in the current value causes a rise in temperature due to heat generation, and the rise in temperature lowers the non-linear resistance characteristics, further increasing the current, and eventually causing a runaway of the varistor. In particular, when heat treatment is performed for electrode baking or side coating, there is a problem that the non-linear resistance characteristic in a low current region is greatly reduced. 500 ° C to 600 ° C beforehand on the sintered body of ZnO varistor
However, this method has been adopted as a measure against deterioration, but it cannot be said that the instability has been sufficiently eliminated. 50
By performing heat treatment at 0 to 600 ° C, interstitial Zn ions in the depletion layer, which caused the deterioration, are reduced, and as a result, the instability of the IV characteristics is reduced. Has not been reached. An object of the present invention is to solve the above two problems.

[0008]

In order to achieve the above object, a zinc oxide porcelain composition of the present invention is obtained by subjecting a mixed powder containing at least bismuth oxide and antimony oxide to a high-temperature sintering or melting heat treatment. After cooling and pulverizing to produce an oxide synthetic powder, at least boron oxide, bismuth oxide, cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide,
Niobium oxide, neodymium oxide, nickel oxide, lead oxide,
Praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide,
A zinc oxide porcelain composition obtained by adding and mixing two or more kinds of oxides selected from yttrium oxide and aluminum oxide together with the above-mentioned oxide synthetic powder to zinc oxide, and firing the mixture. It is.

In order to achieve the above object, the zinc oxide porcelain composition of the present invention comprises at least one oxide selected from the group consisting of zinc oxide, manganese oxide and yttrium oxide in addition to at least bismuth oxide and antimony oxide. A high-temperature heat treatment of sintering or melting is applied to the mixed powder containing more than one kind, and then cooled and pulverized to prepare an oxide synthetic powder.
At least boron oxide, bismuth oxide, cobalt oxide,
Chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide, and It is a zinc oxide porcelain composition obtained by adding and mixing two or more kinds of oxides selected from yttrium oxide and aluminum oxide together with the above-mentioned oxide synthesis powder to zinc oxide, and firing the mixture. is there.

Next, in order to achieve the above object, a method for producing a zinc oxide porcelain composition according to the present invention comprises preparing a mixed powder by mixing at least a powder containing a bismuth oxide powder and an antimony oxide powder. A step of subjecting the mixed powder to a high-temperature heat treatment of sintering or melting to prepare an oxide composite containing at least bismuth oxide and antimony oxide; and grinding the oxide composite to at least bismuth oxide. And a step of preparing an oxide synthetic powder containing antimony oxide and at least boron oxide, bismuth oxide, cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide,
Neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide, and yttrium oxide. A step of preparing a zinc oxide mixed powder by adding and mixing with zinc oxide together with an oxide synthetic powder; a step of forming a zinc oxide formed body by applying pressure molding to the zinc oxide mixed powder; And a step of firing.

Further, in order to achieve the above object, a method for producing a zinc oxide porcelain composition of the present invention is characterized in that at least bismuth oxide and antimony oxide, as well as zinc oxide, manganese oxide and yttrium oxide are selected. Preparing a mixed powder by mixing powders containing at least one or more of the above, and subjecting the mixed powder to sintering or melting high-temperature heat treatment to synthesize an oxide containing at least bismuth oxide and antimony oxide A step of preparing a product; a step of pulverizing the oxide composite to prepare an oxide synthetic powder containing at least bismuth oxide and antimony oxide; at least boron oxide, bismuth oxide, cobalt oxide, chromium oxide, oxide Germanium, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide Two or more kinds of oxides selected from praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide, and yttrium oxide and aluminum oxide together with the above-mentioned oxide synthesis powder to zinc oxide A step of adding and mixing to form a zinc oxide mixed powder, a step of subjecting the zinc oxide mixed powder to pressure molding to form a zinc oxide molded body, and a step of firing the zinc oxide molded body It is provided with a configuration of performing

In order to achieve the above object, the zinc oxide varistor according to the present invention is characterized in that a mixed powder containing at least bismuth oxide and antimony oxide is subjected to a high-temperature heat treatment of sintering or melting, followed by cooling and pulverization to obtain an oxide. Product synthetic powder, at least boron oxide, bismuth oxide,
Cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, oxide Tungsten, and two or more oxides selected from yttrium oxide and aluminum oxide are added to and mixed with zinc oxide together with the above-mentioned oxide synthesis powder, and calcined to obtain a zinc oxide porcelain, and an electrode is formed on the zinc oxide porcelain. Is formed.

Further, in order to achieve the above object, the zinc oxide varistor according to the present invention comprises at least one oxide selected from the group consisting of zinc oxide, manganese oxide and yttrium oxide in addition to at least bismuth oxide and antimony oxide. The mixed powder containing the above is subjected to sintering or melting high-temperature heat treatment, and then cooled and pulverized to create an oxide synthetic powder.
At least boron oxide, bismuth oxide, cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide,
Antimony oxide, silicon oxide, tin oxide, tantalum oxide,
Titanium oxide, tungsten oxide, and two or more oxides selected from yttrium oxide and aluminum oxide are added and mixed with zinc oxide together with the oxide synthesis powder,
It has a configuration in which a zinc oxide porcelain is obtained by firing and electrodes are formed on the zinc oxide porcelain.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In a zinc oxide varistor produced by adding bismuth oxide powder and antimony oxide powder together with another oxide, when the antimony oxide powder in the additive is heated, it sublimates at a considerably low temperature. It is known that they adhere to the surface of ZnO particles and react with ZnO to form a strong antimony compound thin film, thereby preventing grain growth of ZnO particles. However, if antimony oxide and other substances are previously melted and reacted, and added to ZnO powder together with other additives, sublimation of antimony oxide at the time of temperature rise is suppressed,
No strong antimony compound thin film was formed on the surface of the ZnO particles, and sintering proceeded even at a low temperature, and it became clear that the ZnO particles grew actively. Conventionally, a method of sintering the mixed powder of the zinc oxide varistor beforehand as a whole beforehand, or a method of sintering the entire amount of the additive to zinc oxide beforehand, and then adding ZnO to the zinc oxide varistor Various attempts have been made, such as adding and sintering, but a zinc oxide varistor having excellent characteristics by low-temperature sintering has not been easily obtained. However, a mixed powder containing at least bismuth oxide and antimony oxide is subjected to high-temperature heat treatment of sintering or melting, and then cooled and pulverized to prepare an oxide synthetic powder, and at least boron oxide, bismuth oxide, cobalt oxide, oxide Chromium, germanium oxide,
Selected from lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide, and yttrium oxide Two or more kinds of oxides and aluminum oxide are added to zinc oxide together with the above-mentioned oxide synthetic powder, mixed, and calcined to form an electrode on the zinc oxide porcelain composition, thereby easily producing an oxide having excellent properties. It was found that a zinc varistor could be obtained.

The zinc oxide porcelain composition of the present invention has the following
The four types are mixed and molded into a predetermined shape under pressure.
It is obtained by firing at a temperature of 800 ° C or higher.
(1) zinc oxide, (2) at least bismuth oxide and oxidation
Heat the mixed powder containing antimony and sinter or
Oxidation obtained by cooling and pulverizing after applying high temperature heat treatment of melting
Synthetic powder, (3) aluminum oxide, (4) other
Additive. Porcelain set obtained by sintering these
When electrodes are formed on the product, electrical characteristics such as nonlinear resistance characteristics
Yield of zinc oxide varistor with excellent performance and reliability
Can be manufactured. In order to increase the homogeneity,
Al as minium component_TwoO _Three Instead of aluminum salt
It is also preferred to add a solution.

[0016]

The present invention will be described more specifically with reference to the following examples. In the following examples, “weight” refers to [wt]
May be displayed.

Example 1 Bi ₂ O ₃ powder and Sb ₂ O ₃ powder (each powder having an average particle diameter of 2 to 3 μm) were mixed while changing the molar ratio. Add this mixed powder under air atmosphere to 1000
After high-temperature heat treatment at 10 ° C. for 10 hours and cooling, the mixture was mechanically pulverized and then finely pulverized by a jet mill to obtain a synthetic powder (average particle size: about 0.5 to 1.5 μm). (Note that the mixed powder of Bi ₂ O ₃ and Sb ₂ O ₃ melted in some compositions but sintered in the other compositions during the high-temperature heat treatment). Below, Bi ₂ O ₃ and S
The thus prepared synthetic powder of b ₂ O ₃ was converted to Bi ₂ O ₃ / Sb
_It is referred to as ₂ O ₃ synthetic powder. ZnO powder and the Bi ₂ O ₃
/ Sb ₂ O ₃ synthetic powder, B ₂ O ₃ powder, Bi ₂ O ₃ powder, Co ₃ O
₄ powder, Cr ₂ O ₃ powder, MnO ₂ powder, and NiO powder,
Weight ratio is 100: 3.50: 0.058: 1.34: 0.954: 0.203: 0.41
4: The compounded powder blended to be 0.383 was mixed and pulverized by a wet method using a monomalon pot and stabilized zirconia balls for 18 hours so as to pass through a 42 mesh. An aqueous solution of aluminum nitrate (0.0002 mol in terms of Al ₂ O ₃ with respect to 1 mol of ZnO) was added to the dried mixed powder, mixed in a mortar, and pressed into a disk. Next, the obtained molded body was kept at 950 ° C. for 10 hours in the atmosphere to obtain a sintered body. The sample size of the sintered body was 2.3 mm in thickness and 14 mm in diameter.

Next, a method for manufacturing a zinc oxide varistor will be described with reference to FIG. FIG. 1 is a schematic perspective view of a disk-type zinc oxide varistor 10 prepared using the zinc oxide-based porcelain composition of the present invention. An aluminum layer (not shown) is formed by spraying aluminum on both surfaces of the sintered body 11 obtained as described above, and then copper is sprayed on the aluminum layer formed on both surfaces. Thus, the electrode 12 was formed. After the lead wire 13 was attached to the electrode 12 with solder, a molded body other than the lead wire was subjected to epoxy grease painting to obtain a zinc oxide varistor. Some porcelains were heat treated at 700 ° C for 1 hour, and varistors were made using this.

The electrical characteristics of the zinc oxide varistor thus obtained were evaluated. The initial electrical characteristics include the rising voltage V _1mA / mm (voltage for 1mm thickness between both terminals when 1mA current is applied) and nonlinear resistance index _0.1mA
It was measured alpha _{1 mA} (a value obtained by using the V _{1 m A} and V _0.1mA) (In the following description, the non-linear resistance index _0.1mA
α _{1 mA} is sometimes simply referred to as α value). V _{1 mA} / mm increased from 180 V to 350 V as the proportion of antimony oxide in the added synthetic powder increased. The larger the nonlinear resistance index, the greater the surge absorbing ability. The α value exceeded 60 in any of the samples before the heat treatment.
The value of 55 or more was maintained in the sample after the heat treatment. The nonlinear resistance characteristic in the low current range is represented by the nonlinear resistance parameter: V
Evaluation was _performed at _{1 mA} / V _{0.01 mA} . This value was 1.15 or less in each of the samples of Examples. Next, the reliability to DC load was evaluated. A DC load of 0.2 watts is applied for 500 hours in a high-temperature atmosphere of 80 ° C, and the varistor rise voltage V
Was measured _1mA rate of change △ V _1mA / V _1mA (DC load change rate). Varistor rising voltage V _1mA change rate △ _V1mA / _V1mA
The smaller the value, the more stable the electrical characteristics of the zinc oxide varistor and the higher the reliability. Heat treatment (700
° C., even varistor subjected also varistor not subjected to 1 hour) the rate of change △ V _1mA / V _1mA (DC load change rate) was 5% or less. Furthermore, the reliability against surge was evaluated. 8x
Variation rate of varistor rise voltage V _1mA by applying 20μsec, 0.5kA pulse 10 times △ V _1mA / V _1mA (pulse change rate)
Was measured. Change rate 変_化 V _1mA / V _1mA (pulse change rate) is 5
% Or less. Table 1 shows the composition of the sample, and Table 2 shows the heat treatment (7
The electrical characteristics of the varistor without (00 ° C, 1 hour) and the varistor with the varistor are shown. 700 varistors by conventional manufacturing method
Although the electrical properties were significantly degraded by the heat treatment at ℃, the varistors of the examples showed excellent electrical properties even after the heat treatment.

[0020]

[Table 1]

[0021]

[Table 2]

From Tables 1 and 2, the zinc oxide varistor using the zinc oxide-based porcelain of this embodiment can be sintered at an extremely low temperature.

Example 2 Bi ₂ O ₃ powder (50 mol part)
ZnO powder (10 mol part) and Sb ₂ O ₃ powder (40 mol part) are mixed, and this mixed powder is melted in a crucible under an air atmosphere,
The melt was poured into cold water, mechanically pulverized, and then finely pulverized with a ball mill of a monomalon pot using stabilized zirconia as a cobblestone to obtain a synthetic powder (average particle size: about 0.5 to 1.5 μm).
Hereinafter referred to as Bi ₂ O _3, and ZnO, and that the synthetic powder to be adjusted in this way of Sb ₂ O ₃ is referred to as _{Bi 2 O 3 / ZnO / Sb} 2 O 3 synthetic powder. In the same manner, Bi ₂ O ₃ powder (50 mol parts), MnO powder (10 mol parts) and Sb ₂ O ₃ powder (40 mol parts) are mixed, melted, cooled and pulverized to obtain Bi ₂ O ₃ / MnO / Sb. ₂ O ₃ synthetic powder and B
i ₂ O ₃ powder (50 mol part), Y ₂ O ₃ powder (20 mol part) and Sb ₂ O
₃ powder (30 mol parts) mixed and melted, cooled and ground to a Bi
₂ O ₃ / Y ₂ O ₃ / Sb ₂ O ₃ synthetic powder was obtained. Next, a sample was prepared in the same manner as in Example 1.

A ZnO powder, the above-mentioned Bi ₂ O ₃ / ZnO / Sb ₂ O ₃ synthetic powder, a B ₂ O ₃ powder, a Bi ₂ O ₃ powder, a CoO powder, a Cr ₂ powder
O ₃ powder, MnO ₂ powder, NiO powder in a weight ratio of 100: 3.
5: 0.058: 1.34: 0.954: 0.203: 0.414: 0.383, and the mixture was pulverized by a wet method for 18 hours. An aqueous solution of aluminum nitrate was added to the obtained blended powder, mixed in a mortar, and fired at 900 ° C. in the same manner as in Example 1 to obtain a zinc oxide varistor. Bi ₂ O ₃ / MnO /
The system using Sb ₂ O ₃ synthetic powder and the above Bi ₂ O ₃ / Y ₂ O ₃ / Sb ₂
A zinc oxide varistor was obtained in a system using O ₃ synthetic powder. Table 3
Table 4 shows the composition of the sample, and Table 4 shows the evaluation results of the electrical characteristics.

[0025]

[Table 3]

[0026]

[Table 4]

According to Tables 3 and 4, the zinc oxide varistor using the zinc oxide-based porcelain of the present embodiment has good non-linear resistance characteristics before and after the heat treatment, and the pulse is applied even when the DC load is applied for a long time. Also the rising voltage V _1mA
The absolute value of the rate of change (ΔV _1mA / V _1mA ) was 5% or less, and the reliability was excellent.

Example 3 Bi ₂ O ₃ powder, ZnO powder, and Sb ₂ O ₃ powder were mixed at a molar ratio of 45:10:45. After baking this mixed powder at 1000 ° C. for 5 hours in an air atmosphere, it is subjected to mechanical pulverization and further finely pulverized by a jet mill to obtain a synthetic powder Bi ₂ O ₃ / ZnO / Sb ₂ O
Got _three . Next, a zinc oxide varistor was obtained in the same manner as in Example 1. That is, the ZnO powder and the Bi ₂ O ₃ / ZnO / Sb ₂
O ₃ synthetic powder, B ₂ O ₃ powder, Bi ₂ O ₃ powder, CoO powder, Cr ₂ O ₃ powder, MnO ₂ powder, and NiO powder, weight ratio of 100: 2.42: 0.058 : 1.48: 0.954: 0.203, 0.414:
It was blended to 0.383 and mixed and pulverized by a wet method for 18 hours. The obtained compounded powder was dried, an aqueous solution of aluminum nitrate was added, mixed in a mortar, and pressed into a disk. Next, the obtained molded body is heated at 800 ° C. to 1200 ° C. in air for 2 hours.
After holding for 0 hour, a sintered body was obtained. Next, a zinc oxide varistor was obtained in the same manner as in Example 1. The electrical characteristics of the zinc oxide varistor thus obtained were evaluated in the same manner as in Example 1. Table 5 shows the composition of the sample, and Table 6 shows the evaluation results of the firing temperature and the electrical characteristics.

[0029]

[Table 5]

[0030]

[Table 6]

As is evident from Tables 5 and 6, the zinc oxide varistor using the zinc oxide-based porcelain of the present embodiment has a rising voltage V _{1 mA} / mm from 900 ° C. to 1200 ° C., and the firing temperature increases. It went down from 460V to 120V. All samples have good non-linear resistance characteristics, and have a rising voltage V for both long-term DC loads and surges.
The absolute value of the rate of change of _1mA (△ _V1mA / _V1mA ) was 5% or less, indicating excellent reliability. # 201 and # 2 with firing temperature of 800 ℃ and 850 ℃
02 was too high to measure.

[0032]

According to the present invention, a synthetic powder obtained by subjecting a mixed powder containing at least two of bismuth oxide and antimony oxide to a zinc oxide powder to a high-temperature heat treatment of sintering or melting, and then cooling and pulverizing the mixed powder, Boron, bismuth oxide, cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide , Titanium oxide, tungsten oxide, and at least two or more metal oxides selected from each of yttrium oxide, and aluminum oxide added, and pressed and molded at 750 ° C to 1200 ° C, zinc oxide porcelain for varistors The composition can be sintered, and the varistors obtained from this show excellent electrical properties It became. Among these sintering temperatures, especially when the sintering temperature is low, there are various advantages over sintering at a high temperature. That is,
(1) The firing temperature is greatly reduced, and the power consumption is reduced. (2) The stability of electrical characteristics against electrical load and heat treatment is improved. (3) The life of furnace materials and containers is extended.
(4) Pollution is reduced. (5) The yield is improved.
(6) A high-performance laminated zinc oxide varistor using silver as an internal electrode can be manufactured. (7) Research and development are facilitated.

Although the low-temperature sintering method is superior in electrical characteristics and its stability, more specifically,
(A) A zinc oxide varistor having excellent non-linear resistance characteristics over a low current range to a high current range can be obtained. There is no danger of thermal runaway due to low leakage current and excellent stability. (B)
Excellent electrical characteristics with no fluctuation in electrical characteristics due to voltage application. (C) Higher voltage has become easier. A material having a voltage per unit thickness of 300 V to 500 V can be obtained stably.
(D) Deterioration of electrical characteristics due to heating is small. Even if current flows and heat is generated, acceleration of deterioration due to heat is small.
The baking of the side coat material and the electrode material can be easily performed.

When the zinc oxide porcelain composition is formed into a sheet, alternately laminated with an electrode material, sintered, and the electrodes are connected by a predetermined connection method, a laminated varistor is obtained.
In this case, a firing temperature of 1100 ° C. or higher was required in order to obtain good characteristics with a conventional laminated varistor, but it was necessary to use a noble metal such as platinum as an electrode material. However, since the zinc oxide porcelain composition of the present invention includes a material having excellent electrical properties sintered at a temperature of 950 ° C. or less, it is possible to use low-cost silver as an electrode material, This can greatly contribute to the spread of varistors. A laminated varistor can easily be used for low voltages of 20 V or less, and has excellent non-linear resistance characteristics because of the large cross-sectional area through which current flows despite its small size. That is, the ZnO varistors of the present invention can be used in a wide range from small stacked type and disk type small type to large diameter columnar type, and from low voltage electronic circuits to high voltage power transmission and distribution. Can be used for Since the characteristics are extremely stable with respect to application of voltage and heating, baking of a silver electrode at a temperature of around 700 ° C. is easy on the obtained zinc oxide porcelain composition.

In addition, in order to facilitate comparison of data, in the examples, CoO, MnO, and NiO were added while keeping the ratio of the three addition amounts constant. However, the zinc oxide-based porcelain composition of the present invention is: These amounts are not limited. Further, in the examples, data of firing at 900 to 1200 ° C. is shown, but B ₂ O ₃ , C
By adjusting the addition amount of r ₂ O _{3 and the} like, a varistor with good characteristics can be obtained even when the firing temperature is lowered to 750 ° C.
In addition, in a zinc oxide varistor, Al ₂ O ₃ is often added in order to improve the specific linear resistance characteristic in a high current region. In each of the examples, Al ₂ O _{3 and} 0.0026 wt parts are added to 100 wt parts of ZnO. However, the amount of addition depends on the use of the varistor and is not limited to 0.0026 wt part.

The following can be considered as a cause of stabilization of the electrical characteristics of the ZnO varistor of the present invention. That is, it is conceivable that a high oxygen pressure state was generated inside the sintered body by some action during the firing process, and the density of interstitial Zn atoms was reduced. And in that case, it is considered that the conversion of ZnO into a semiconductor is mainly performed by Al.

As described above, the present invention provides a zinc oxide porcelain composition capable of producing a zinc oxide varistor excellent in electrical characteristics such as non-linear resistance characteristics and reliability at low temperature sintering with a high yield. Can be provided. The zinc oxide porcelain composition of the present invention has a firing temperature of 75 when producing the sintered body.
Even if the temperature is lowered to 100 to 1000 ° C., the particles can be sintered uniformly and the particle size important for the varistor can be uniformly grown. In addition, it can withstand high current pulses sufficiently, and can maintain high performance with respect to AC application.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a disk-type zinc oxide varistor prepared using the zinc oxide porcelain composition of Example 1 of the present invention.

[Explanation of symbols]

 10 Zinc oxide varistor of disk type 11 Sintered zinc oxide 12 Electrode 13 Lead wire

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Daiki Miyamoto 2-7-1, Ayumino, Izumi-shi, Osaka F-term in Osaka Prefectural Institute of Advanced Industrial Science and Technology (reference) 4G030 AA07 AA11 AA12 AA13 AA16 AA20 AA21 AA22 AA24 AA25 AA28 AA29 AA32 AA34 AA35 AA36 AA37 AA40 AA42 AA43 BA04 5E034 CB01 CC03 DA03 DE01 DE03 DE05 DE07 DE20

Claims (6)

[Claims] Claims 1. At least bismuth oxide (Bi_TwoO_Three) And oxide
Nchimon (Sb_TwoO_ThreeOr Sb_TwoO_FourOr Sb_TwoO_Five) And a mixture containing
After subjecting the powder to high temperature heat treatment of sintering or melting,
Pulverized to produce an oxide synthetic powder, at least
Udine (B_TwoO_Three), Bismuth oxide (Bi_TwoO_Three), Cobalt oxide
(CoO or Co_ThreeO_Four), Chromium oxide (Cr_TwoO _Three), Germanic oxide
Um (GeO_Two), Lanthanum oxide (La_TwoO_Three), Magnesium oxide
(MgO), manganese oxide (MnO or Mn_TwoO_ThreeOr MnO
_Two), Niobium oxide (Nb_TwoO_Five), Neodymium oxide (Nd_TwoO_Three),
Nickel oxide (NiO), lead oxide (PbO), praseo oxide
Um (Pr_TwoO_Three), Antimony oxide (Sb_TwoO_ThreeOr Sb_TwoO_FourOr S
b_TwoO_Five), Silicon oxide (SiO _Two), Tin oxide (SnO_Two), Oxidation
(Ta_TwoO_Five), Titanium oxide (TiO_Two), Oxidized tongue
Ten (WO_Three), And yttrium oxide (Y_TwoO_Three)
Two or more oxides and aluminum oxide (Al_TwoO
_Three) Is added and mixed with zinc oxide together with the above-mentioned oxide synthetic powder.
A zinc oxide porcelain composition obtained by combining and firing. 2. A mixed powder containing at least bismuth oxide and antimony oxide, wherein at least one oxide selected from zinc oxide, manganese oxide, and yttrium oxide in addition to bismuth oxide and antimony oxide The zinc oxide porcelain composition according to claim 1, which is a mixed powder containing: 3. A step of mixing a powder containing at least a bismuth oxide powder and an antimony oxide powder to form a mixed powder, and subjecting the mixed powder to a high-temperature heat treatment of sintering or melting to obtain at least a bismuth oxide powder. A step of preparing an oxide composite containing and antimony oxide, and a step of pulverizing the oxide composite to prepare an oxide composite powder containing at least bismuth oxide and antimony oxide, at least boron oxide, Bismuth oxide, cobalt oxide, chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, oxide Titanium,
A step of adding and mixing two or more kinds of oxides selected from tungsten oxide and yttrium oxide and aluminum oxide together with the oxide synthetic powder to zinc oxide to form a zinc oxide mixed powder; A method for producing a zinc oxide porcelain composition, comprising the steps of: forming a zinc oxide porcelain body by applying pressure molding to the mixture; and sintering the zinc oxide porcelain body to obtain a zinc oxide porcelain composition. 4. A step of preparing a mixed powder by mixing at least a powder containing bismuth oxide powder and antimony oxide powder, wherein at least bismuth oxide and antimony oxide, zinc oxide, manganese oxide, and yttrium oxide are mixed. 4. The method for producing a zinc oxide porcelain composition according to claim 3, wherein the step is a step of mixing powders containing at least one selected from three oxides to prepare a mixed powder. 5. A mixed powder containing at least bismuth oxide and antimony oxide is subjected to sintering or melting high-temperature heat treatment, and then cooled and pulverized to prepare an oxide synthetic powder.
At least boron oxide, bismuth oxide, cobalt oxide,
Chromium oxide, germanium oxide, lanthanum oxide, magnesium oxide, manganese oxide, niobium oxide, neodymium oxide, nickel oxide, lead oxide, praseodymium oxide, antimony oxide, silicon oxide, tin oxide, tantalum oxide, titanium oxide, tungsten oxide, and An oxide formed by adding and mixing two or more kinds of oxides selected from yttrium oxide and aluminum oxide with zinc oxide together with the above-mentioned oxide synthetic powder, and calcining to form an electrode on a zinc oxide porcelain composition obtained. Zinc varistor. 6. A mixed powder containing at least bismuth oxide and antimony oxide, wherein at least one selected from oxides of zinc oxide, manganese oxide and yttrium oxide in addition to bismuth oxide and antimony oxide The zinc oxide varistor according to claim 5, which is a mixed powder containing: