JP2001237108A - Voltage nonlinear resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the production of a voltage nonlinear resistor easier by reducing varistor voltage fluctuation among the production lots of the resistor by reducing the diameter variation of sintered zinc oxide particles in the sintered body of the resistor obtained by using a mixed raw material. SOLUTION: In this voltage nonlinear resistor which contains a zinc oxide as the main ingredient and a plurality of accessory ingredients added to the main ingredient by very small amounts, the bismuth oxide added to the zinc oxide as one of the accessory ingredients has a bulk density of <45 ml/100 g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor.

[0002]

2. Description of the Related Art A conventional voltage non-linear resistor includes metal oxides such as bismuth oxide, cobalt oxide, manganese oxide, antimony oxide, nickel oxide, chromium oxide, and germanium oxide as subcomponents in addition to zinc oxide as a main component, and A small amount of aluminum nitrate is added, and the mixed and dispersed slurry is granulated by a spray drier, formed into a predetermined shape, and fired at 1200 to 1300 ° C. in the atmosphere for 2 to 3 hours to produce a sintered body. The obtained sintered body exhibits excellent voltage non-linearity and is widely used as a surge absorbing element and a voltage stabilizing element.

[0003]

In the conventional voltage non-linear resistor described above, the cohesiveness of the raw material powder differs depending on the size of the subcomponent used, and the cohesive force increases as the bulk (larger particle size) increases. Becomes large, that is, the dispersibility decreases. For this reason, the obtained mixed raw material has poor homogeneity, and the sintered body of the voltage non-linear resistor obtained using the mixed raw material has a large variation in the zinc oxide sintered particle diameter, and as a result, the operation start voltage (varistor voltage) Varies from production lot to production lot. Further, as the bulk becomes smaller (the particle size becomes larger), the homodispersibility of the minor component becomes lower, and the same result as described above is obtained. In particular, this has been a serious problem in low-voltage products having a varistor voltage of 100 V / mm or less.

[0004] For this reason, in order to control the variation between production lots to a small extent, the management of the volume of the trace subcomponent has been an important factor. The varistor voltage is a voltage generated between the electrodes when a pair of electrodes are provided on both surfaces of a sintered body of a voltage non-linear resistor and a current of 1 mA flows between the electrodes. Is determined by the number of grain boundaries of the zinc oxide sintered particles. One of zinc oxide-bismuth oxide based voltage non-linear resistors
The varistor voltage per grain boundary is about 3 V. If the number of grain boundaries per unit length increases (ie, if the zinc oxide sintered particle diameter decreases), the varistor voltage increases, and if the number of grain boundaries decreases (ie, zinc oxide decreases). The varistor voltage is lower (if the sintered particle size is larger).

It is an object of the present invention to reduce variations in varistor voltage between production lots of a voltage non-linear resistor, and to provide a low-voltage resistor that is easy to produce.

[0006]

Means for Solving the Problems In order to achieve the above object, the present invention has the following arrangement.

[0007] The invention described in claim 1 of the present invention is, in particular,
In a voltage nonlinear resistor obtained by adding zinc oxide as a main component and a plurality of oxide raw materials as subcomponents, bismuth oxide, which is one of the subcomponents, has a bulk of 45 ml /
A voltage non-linear resistor using a material smaller than 100 g, a composition containing zinc oxide as a main component and bismuth oxide,
In the sintering process, zinc oxide starts sintering at around 700 ° C. in the presence of bismuth oxide,
It is known that the growth of zinc oxide particle size starts around 0 to 950 ° C. It is not so difficult to obtain a sintered body with a particle size of about 10 to 15 μm with a composition of only zinc oxide and bismuth oxide, but in order to obtain other stable electrical properties such as surge absorption, other than bismuth oxide, It is necessary to add an auxiliary component such as an oxide. These sub-components form a spinel compound and segregate at the grain boundaries and hinder the growth of the zinc oxide particle size, so that the particle size variation increases and the varistor voltage fluctuates. In order to solve this, it is necessary to suppress the expression of a spinel compound that inhibits grain growth in the temperature range of zinc oxide particle growth. By using bismuth oxide having a bulk of 45 ml / 100 g or less, relatively coarse bismuth oxide has reduced cohesiveness and improved mixing and dispersibility with zinc oxide, and zinc oxide particles formed via bismuth oxide. The expression of the growth inhibiting spinel (zinc oxide-antimony oxide compound) can be alleviated and controlled. This makes it possible to relatively easily prepare a sintered body having a coarse zinc oxide particle size of 30 μm or more and a small variation width, and it is possible to reduce fluctuations in varistor voltage between manufacturing lots. It has the action of:

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

First, bismuth oxide 0.75 with respect to zinc oxide
mol, cobalt oxide 0.5 mol, manganese oxide 0.
15 mol, antimony oxide 0.5 mol, nickel oxide 0.25 mol, chromium oxide 0.1 mol, germanium oxide 0.05 mol, and aluminum nitrate 0.001
After weighing only 6 mol of each subcomponent, premixing is performed by a ball mill. In addition, the bismuth oxide having a bulk shown in (Table 1) was used. This composition is known as a low-voltage non-linear resistor.

Next, the pre-mixed sub-component composition was mixed with a binder, a dispersant, and pure water together with 97.6964 mol of zinc oxide.
And a slurry is prepared by mixing with a dispersion device.

Next, the slurry is spray-dried with a spray drier to produce granulated powder.

Thereafter, the granulated powder is formed into a disc having a diameter of 14 mm and a thickness of 1.2 mm at a pressure of 800 kg / cm ² .

Next, firing was performed at a temperature of 1290 ° C. in the air to form a sintered body, and silver electrodes were baked on both surfaces of the sintered body to complete a voltage non-linear resistance element having a varistor voltage of 96 V / mm. . The sintered body had a diameter of 11 mmφ and a thickness of 1.
0 mm.

The characteristics of the obtained voltage non-linear resistance element were measured, and the results are shown in Table 1.

[0015]

[Table 1]

As shown in Table 1, the bulk was 45 ml / 1.
The varistor voltage of a lot prepared using a bismuth oxide material controlled to be not more than 100 g is lower than 100 V / mm.
It turns out that it is 5.8-98.2V / mm and is stable. On the other hand, if the bulk of bismuth oxide is higher than 45 ml / 100 g, the operating voltage increases. This is because when the bulk of bismuth oxide increases (the particle size decreases), the spinel that inhibits the growth of sintered particles of zinc oxide is formed in a low temperature stage (900 to 900) of the firing process.
(At 950 ° C. or lower) at the grain boundaries of the zinc oxide particles, which hinders the growth of the zinc oxide particles in the sintered body, so that the zinc oxide particles are small and the number of zinc oxide particles per unit length increases, so that the varistor voltage increases. .

On the other hand, if the bulk of bismuth oxide is reduced, the varistor voltage can be controlled to be low. However, if the bulk of bismuth oxide is reduced to 40 ml / 100 g or less, the production cost of ordinary industrial bismuth oxide increases. Along with
The volume of bismuth oxide is small to some extent (coarse particle size)
As it becomes more difficult to mix and disperse with zinc oxide, it is not preferable. In order to obtain a voltage non-linear resistor having a varistor voltage which is relatively easily available for industrial use, and which is stable and small in variance, a volume of bismuth oxide of 45 ml /
It is clear that using 100 g or less, preferably 40 ml / 100 g or more, is an effective means.

[0018]

As described above, in a voltage nonlinear resistor comprising zinc oxide as a main component and a plurality of trace subcomponent materials added thereto, the bulk of bismuth oxide, one of the subcomponents, increases. By using a material smaller than 45 ml / 100 g, the cohesiveness of bismuth oxide is alleviated, and the dispersibility with zinc oxide is not reduced. The expression of the inhibiting spinel compound can be reduced. Therefore, the obtained voltage non-linear resistor has a stable varistor voltage between production lots, and especially in low-voltage products, the number of zinc oxide particles per unit length of the sintered body is almost constant, and the voltage non-linear voltage variation of the varistor voltage is small. The resistor can be manufactured stably.

Claims (1)

[Claims] 1. A voltage non-linear resistor comprising zinc oxide as a main component and a plurality of trace subcomponent materials added thereto, wherein bismuth oxide, one of the subcomponents, has a bulk of 4%.
A voltage non-linear resistor using a material smaller than 5 ml / 100 g.