JPS6038841B2 - Voltage nonlinear resistance element - Google Patents

Description

[Detailed description of the invention] The present invention relates to a novel voltage nonlinear resistance element.

More specifically, the present invention relates to a voltage nonlinear resistance element containing zinc oxide as a main component and used in lightning arresters, surge absorbers, and the like. BACKGROUND ART Conventionally, silicon carbide (SIC) has been used as a voltage nonlinear resistance element for a lightning arrester that protects electrical equipment from lightning surges and abnormal voltages in the system.

However, this voltage nonlinear resistance element made of silicon carbide has poor voltage nonlinearity, so it is configured to block leakage current by using various discharge gaps against the constantly applied voltage. There are problems such as the use of gaps causing malfunctions due to short waveform lightning surges. Recently, as a voltage non-linear resistance element, in place of silicon carbide, Akatsuki compact, which is made of zinc oxide as a main component and various additives has been used for real sheep.

This exposure voltage non-linear resistance element has features such as excellent voltage non-linearity over a wide current range, and by using this voltage non-linear resistance element, it is possible to create A gapless arrester is obtained which has better response characteristics than conventional arresters. This lack of a discharge gap improves reliability (for example, preventing malfunctions due to lightning surges, gap variations, etc.), but on the other hand, since voltage is always applied, a small amount of leakage current flows, and unintended consequences occur. Leakage current increases due to deterioration of voltage non-linear resistance elements caused by electricity. Therefore, zinc oxide-based voltage non-linear resistance elements made using conventional compositions and manufacturing methods are required to operate under low electrical conductivity conditions in order to maintain long life. There were restrictions on usage, such as the need to use Additionally, there is a strong desire to improve the protection level of earth arresters in order to reduce the insulation performance of electrical equipment from abnormal voltages (switching surges, flea surges).
To meet this demand, it is necessary to have a high conduction rate and flatten the voltage in the large current region, and conventional voltage nonlinear resistance elements do not have sufficient characteristics for these, so it is necessary to reduce the protection level. It's becoming a hindrance. The present inventors have conducted extensive research in order to provide a voltage nonlinear resistance element that eliminates the above-mentioned drawbacks, can be used under severe electrical current conditions, and is capable of flattening the voltage of large currents. As a result of repeated efforts, the present invention was completed.

In other words, the present invention uses zinc oxide as the main component, with a content of 10 to 30% (weight %, the same applies hereinafter) in terms of silver oxide (1).
Bismuth borosilicate glass containing silver of 0.05 to 0.5
% is added, more than 90% of the bismuth oxide (plate) in the retaining structure is a crystalline phase of D-cubic bismuth, and the Akatsuki structure itself has voltage non-linearity. The invention relates to a voltage non-linear resistance element having the above-mentioned specific composition and properties, and by using the voltage non-linear resistance element having the above-mentioned specific composition and properties, high voltage resistance elements that cannot be easily achieved with conventional zinc oxide-based voltage non-linear resistance elements can be achieved. Extremely remarkable effects are achieved in that it is possible to reduce electrical current and flatten the voltage in a large current region.

The voltage nonlinear resistance element of the present invention has zinc oxide (Zn○) as a main component, bismuth oxide (m) (Bi203), cobalt oxide (m) (Co203), and antimony oxide (m).
(Sb203), manganese oxide (W) (Mn02), chromium oxide (m) (Cr203), etc. Analytical observation using (SEM) etc. revealed that there are particles larger than 10 m mainly composed of zinc oxide, spinel particles of several meters, and bismuth oxide (m) that exists between the zinc oxide particles and spinel particles.
) consists of crystals.

The raw material, bismuth oxide (m), usually starts a reaction at 800 to 900 g, incorporates various oxide components, forms a pyrochlore crystal phase, and then decomposes to form a spinel crystal phase and bismuth oxide (m). A liquid phase is generated and the binding of zinc oxide progresses. In a voltage nonlinear resistance element having such a fine structure, voltage nonlinearity is thought to be expressed mainly in the electrical barrier layer existing at the interface between zinc oxide particles. Therefore, voltage nonlinearity, leakage current stability, and deterioration characteristics against external impulses can be changed by controlling the properties of the interface between zinc oxide particles and the state of bismuth oxide (m) existing between zinc oxide particles. sell. According to the research results to date, glass materials (
Many contain various additives such as bismuth glass.
) has been found to be effective by applying it to the compact and thermally diffusing it to the grain boundaries between zinc oxides, or by adding it to the raw material.

For example, Japanese Patent Publication No. 52-40440 states that a zinc oxide-based voltage nonlinear resistance element doped with silver-containing bismuth borosilicate glass has improved voltage nonlinearity and excellent high-temperature DC load characteristics. Journal of Applied Physics (Japan), 15
Volume (1976), page 1847 (Japan Jouma
lofApplied Physics 15 (1976)
1) contains tetragonal bismuth oxide (8-Bi203).
) or cubic (face-centered cubic) bismuth oxide (6-
A zinc oxide voltage nonlinear resistance element containing body-centered cubic bismuth oxide (Y-Bi203) has inferior current-voltage characteristics in the low current region, compared to a zinc oxide voltage nonlinear resistance element containing body-centered cubic bismuth oxide (Y-Bi203). It has been stated that only under extremely low electromagnetic conditions, the changes over time of both direct current and alternating current are small. According to the research results of the present inventors, under severe conditions, zinc oxide-based voltage nonlinear resistance elements doped with bismuth borosilicate glass containing silver, tetragonal bismuth oxide (8-Bi203) and cubic In zinc oxide-based voltage nonlinear resistance elements containing bismuth oxide (6-Bi203), leakage current (alternating current power,
The change over time of the resistance component (resistance component) is significantly large, leading to thermal runaway in a short period of time.
Knowledge that in zinc oxide-based voltage nonlinear resistance elements containing a large amount of Bi203), the change in leakage current over time after a long period of time is extremely small even under extremely severe electrical conduction conditions, and moreover, it tends to decrease over time. I got it.

Therefore, the voltage nonlinear resistance element of the present invention has silver-containing bismuth borosilicate glass added thereto, and bismuth oxide (m
) whose crystal system is tetragonal bismuth oxide (3-Bi203)
Alternatively, it exhibits extremely excellent effects that are not provided by box lead oxide voltage nonlinear resistance elements containing cubic bismuth oxide (6-Bi203).

Next, the voltage nonlinear resistance element of the present invention will be explained with reference to Examples and Comparative Examples.

Zn.

(95.5 mol%), Bi203 (0.5 mol%), S
i02 (0.5 mol%), SQ. 3 (1.0 mol%),
Cr203 (0.5 mol%), Ni0 (1.0 mol%)
, Mn02 (0.5 mol%) and Co203 (0.5
0.1% of bismuth borosilicate glass containing 20% A saddle was added to the mixture (mol%), and this mixture was bonded by a normal ceramic manufacturing method to form a porcelain body. Ta.

The obtained sintered body was then polished according to the method disclosed in Japanese Patent Publication No. 52-4044 (mentioned above), and then electrodes such as aluminum metallicon were formed. In addition, the obtained Akatsuki body was refired at 70,000 ℃ in the atmosphere according to the method described in Journal of Applied Physics (Japan), 15 Lid (1976), 184 Towariko, and the same as above. An electrode was formed.

The obtained element was obtained by the former conventional method (hereinafter referred to as B element).

Comparative example 1) is tetragonal bismuth oxide (8-Bi203)
and cubic bismuth oxide (6-Bi203), and the one re-fired by the latter method (hereinafter referred to as A element, Example 1) contains almost 100% body-centered cubic bismuth oxide (y-Bi203). It was a phase change. A magnetic body was formed by sintering in the same manner as above except that the mixture containing 20% Ag20 and no bismuth borosilicate glass was used, and then this sintered body was heated in the atmosphere for 70,000 hours by the latter method. A sintered silk body (hereinafter referred to as C element, Comparative Example 2) containing body-centered cubic bismuth oxide (y-Bi203) was obtained. Subsequently, the current-voltage characteristics of the obtained A element, B element, and C element were measured.

The measurement results are shown in Table 1. V, oK in Table 1
^ and V, m^ are the voltages (KV) across the device when currents of 10 KA and 1 mA are passed through the device, respectively, and V skin ^/V, m^ is the limiting voltage ratio (i.e., the voltage in the large current region). ), and 0.1QI is 0
．． (showing the nonlinear index at 1 mA and lmA). Table 1 From Table 1, the voltage nonlinearity of A element and C element is B
Although the voltage nonlinearity of each element is inferior to that of the other elements, it is clear that it is almost the same as the limiting voltage ratio of the B element and the A element, so in the A element, V, M
This shows that V, oKA decreases (that is, the voltage becomes flat) as the voltage decreases.

Conventionally, voltage nonlinear resistance elements with large voltage nonlinearity were considered to have extremely small leakage current for the same voltage and good stability.

Therefore, relatively high electrical conductivity (applied voltage and V, m^ ratio)
It was thought that the leakage current would be small even when a voltage of Here, the following life measurement example shows that the life of the crab pressure nonlinear resistance element is not simply due to large voltage nonlinearity.

FIG. 1 shows the time-dependent changes in current at direct current conductivity in elements A, B, and C.

The conditions for the conspiracy are shown in Table 2. From Table 2 and Figure 1, it is clear that element A has very good characteristics with little change in current over time, and has remarkable characteristics not seen in elements B and C.

In other words, in the A element, the current shows a constant decrease over time and remains at this level even after 600 hours, whereas in the B and C elements, the current increases rapidly over a short period of time. It does not exhibit sufficient electromagnetic properties. Therefore, only the A element (that is, the voltage nonlinear resistance element of the present invention) can withstand electrical interference under such severe conditions. The characteristics of the A element under direct current conditions have been described above, but these characteristics can be cured in exactly the same way under alternating current conditions. As mentioned above, the voltage nonlinear resistance element of the present invention contains zinc oxide as a main component and has Ag20
It is made by adding 0.05 to 0.5% of bismuth borosilicate glass containing 10 to 30% silver in terms of silver, but instead of the bismuth borosilicate glass containing silver, the oxide component of the glass As, Bi203, Si02, B20
The Akatsuki compact obtained by adding 3 and Ag20 individually is
It does not show the remarkable effect seen in the above-mentioned A element.

As the Ag20 content in the silver-containing bismuth borosilicate glass, 10 to 30% is adopted from the dissolution range of A&○ in the bismuth borosilicate glass. When the Ag20 content in the bismuth borosilicate glass containing silver is out of the above range, silver will precipitate in the bismuth borosilicate glass, which is not preferable. When the amount of silver-containing bismuth borosilicate glass added is less than 0.05% with respect to raw materials such as zinc oxide, the resulting voltage nonlinear resistance element has characteristics similar to the C element, and 0.5% or less. %, there is no significant effect on extending the life of the voltage nonlinear resistance element, and both are unfavorable. In addition, by examining the heat treatment conditions of the sintered body, we found that the body-centered cubic bismuth oxide (
Although the amount of y-Bi203) can be changed to some extent, the intensity ratio determined by X-ray diffraction indicates that in a voltage nonlinear resistance element containing 90% or more of body-centered cubic bismuth oxide (y-Bi203) and containing silver glass, The characteristics were good.

At present, the role of the crystal phase of bismuth borosilicate glass containing A&○ and cubic bismuth oxide on the change in current over time has not been clarified, but thermally stimulated current (
From the observation of TSC), it is presumed that these two effects work together to reduce and stabilize the traps in the zinc oxide boundary layer.

As already mentioned, by stabilizing the electrical barrier layer at the zinc oxide boundary, V after the application of a lightning impulse.

The rate of change at a small value (voltage value required to cause a current of 10 A to flow through the element) is also extremely small. This indicates a change in the current-voltage characteristics of the voltage nonlinear resistance element during surge absorption, and the rate of change is shown in Table 3. This shows that in a voltage nonlinear resistance element with a large rate of change, the leakage current changes before and after lightning strikes. In conventional voltage non-linear resistance elements, the current-voltage characteristics change, followed by an increase in leakage current, and therefore premature deterioration. Table 3 It is clear from Table 3 that the A element has better deterioration characteristics against lightning surges than the B and C elements.

As described above, the voltage nonlinear resistance element of the present invention can operate stably even under extremely severe conditions, high yield rates, and high temperatures, and is fully useful for improving the protection level of lightning arresters.

[Brief explanation of drawings]

FIG. 1 is a graph showing changes in current over time during electrical conduction of one embodiment of the voltage nonlinear resistance element of the present invention (A element) and the voltage nonlinear resistance elements for comparison (B element and C element). be. O diagram

Claims (1)

[Claims] 1. Bismuth borosilicate glass containing 10-30% by weight of silver (calculated as silver (I) oxide) is added to a material whose main component is zinc oxide, and sintered. 90% by weight or more of bismuth (III) oxide in the body is a body-centered cubic bismuth oxide crystal phase, and the sintered body itself has voltage nonlinearity. Resistance element.