JP2011233567A - Voltage nonlinear resistor, and lightning arrester mounted with voltage nonlinear resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage nonlinear resistor having excellent voltage nonlinearity, voltage-applied life characteristics and thermal stability.SOLUTION: The voltage nonlinear resistor includes a sintered body mainly constituted of zinc oxide particles, spinel particles whose main components are zinc and antimony, and a bismuth oxide phase. In the bismuth oxide phase, at least one kind of alkali metal selected from the group consisting of potassium and sodium is included in the range of 0.036 atom% or more and 0.176 atom% or less. An area ratio (A) of the bismuth oxide phase to the cross section of the sintered body is in the range of 2% or more and 8% or less. Also, a ratio (A/B), which is a ratio of the area ratio (A) of the bismuth oxide phase to the area ratio (B) of the spinel particles, to the cross section of the sintered body is in the range of 0.3 or more and 1.5 or less.

Description

  The present invention relates to a voltage non-linear resistor suitably used for a lightning arrester, a surge absorber, and the like, and a lightning arrester equipped with the voltage non-linear resistor.

  Conventionally, voltage non-linear resistors used for lightning arresters, surge absorbers, etc. are effective additions to zinc oxide (ZnO), the main component, for improving electrical characteristics, including bismuth oxide, which is essential for the expression of voltage non-linearity. It is composed of a sintered body that has been subjected to pulverization, mixing, granulation, molding, firing, and post-heat treatment, and is provided with an electrode and a side high resistance layer on the sintered body. Yes.

  The operation of the voltage non-linear resistor is broadly divided into a standby state where no surge energy is applied and an operation state where surge energy is applied. At present, the voltage non-linear resistor is mainly used in a gapless structure in which a voltage is always applied to both ends during standby. Therefore, it is important that the current (leakage current) flowing through the element during standby does not show an increasing tendency. In order to ensure that the leakage current does not show an increasing tendency, that is, to ensure good electric charge life characteristics, heat treatment after firing is generally indispensable (see, for example, Patent Document 1 and Patent Document 2). This heat treatment after firing prevents the leakage current from increasing, and can prevent thermal runaway caused by an increase in the amount of heat generated by the voltage nonlinear resistor accompanying the increase in leakage current. However, when the heat treatment after firing is performed, the voltage nonlinearity of the voltage nonlinear resistor generally tends to be greatly deteriorated, and a method of performing the heat treatment in two stages is disclosed to prevent this. (For example, see Patent Document 3).

A flat rate is used as an index representing the quality of voltage nonlinearity during operation. The flatness ratio is defined as the ratio of the voltages generated at both ends of the voltage nonlinear resistor when two currents having different sizes are passed through the voltage nonlinear resistor. It depends on the diameter of the linear resistor. For example, the ratio (V _10kA / V _1mA ) of the voltage value (V _10kA ) when energizing 10kA, which is a numerical value that reflects the characteristics of the large current region, and V _1mA when energizing _1mA is used as the flat rate. Technological development for improving the voltage nonlinearity of the resistor, in other words, for reducing the flatness value, has been earnestly advanced.

  Further, improvement of the thermal stability in the operating state is important from the viewpoint of ensuring the reliability of the element. When surge energy is applied to the element, the temperature of the element rises due to Joule heat generation. Due to the nature of the element, the current increases as the element temperature rises. For this reason, if the element heat generation is large and the thermal balance with the element ambient temperature cannot be maintained, the element may cause thermal runaway, so it has excellent thermal stability, in other words, temperature rise An element with a small leakage current is required.

  The performance of the voltage nonlinear resistor during standby and during operation described so far greatly depends on the microstructure of the sintered body. The sintered body is roughly composed of zinc oxide particles, spinel particles mainly composed of zinc and antimony, and a bismuth oxide phase existing in the vicinity of the triple point of the grain boundary. In addition, zinc silicate particles mainly composed of silicon are also observed depending on the additive. It is well known that bismuth, which is an additive essential for the expression of voltage non-linearity, exists not only in the bismuth oxide phase but also in the grain boundary between zinc oxide particles in a slight amount (for example, Non-Patent Document 1). Efforts such as structure elucidation and measurement of interface states at grain boundaries have been carried out.

JP 52-53295 A Japanese Patent Laid-Open No. 50-131094 JP 58-200508 A

Kei-Iciro Kobayashi, Journal of American Ceramic Society, "Continuous Existence of Bismuth at Grain Boundaries of Zinc Oxide Varistor without Intergranular Phase", 81, [8], 2071-2076 (1998)

In the voltage non-linear resistor, heat treatment at about 500 ° C. is necessary after firing in order to improve the charging life characteristic during standby. However, the conventional technique has a drawback that the voltage nonlinearity is greatly deteriorated, although the electric life characteristic is improved by the heat treatment after firing.
Further, in the prior art, it is difficult to obtain an element having excellent thermal stability, and it is necessary to increase the size of the metal electrode that sandwiches the element in order to improve the heat dissipation of the element. However, a lightning arrester equipped with such a voltage non-linear resistor has a drawback that its internal structure becomes complicated.
As described above, the conventional technique has a problem that a voltage non-linear resistor having excellent voltage non-linearity, electric charging life characteristics and thermal stability cannot be obtained.
Therefore, the present invention has been made to solve the above-described problems, and provides a voltage non-linear resistor having excellent voltage non-linearity, electric charging life characteristics, and thermal stability. Objective.

  The present invention is a voltage non-linear resistor composed of a sintered body mainly composed of zinc oxide particles, spinel particles mainly composed of zinc and antimony, and a bismuth oxide phase, and in the bismuth oxide phase, The area ratio of the bismuth oxide phase occupying in the cross section of the sintered body is contained in the range of 0.036 atomic% or more and 0.176 atomic% or less of at least one alkali metal selected from the group consisting of potassium and sodium (A ) Is in the range of 2% to 8%, and the ratio (A / B) of the area ratio (A) of the bismuth oxide phase to the area ratio (B) of the spinel particles in the cross section of the sintered body is 0.00. The voltage non-linear resistor is in the range of 3 to 1.5.

  ADVANTAGE OF THE INVENTION According to this invention, the voltage non-linear resistor which has the outstanding voltage non-linearity, the electrical charging lifetime characteristic, and thermal stability can be provided. Further, by using the voltage nonlinear resistor according to the present invention, it is possible to realize an overvoltage protection device such as a lightning arrester and surge absorber having excellent protection characteristics and life performance and high reliability.

3 is a schematic diagram of a fine structure of a voltage nonlinear resistor according to Embodiment 1. FIG. It is a schematic cross section of the sample for evaluation used by the Example and the comparative example. It is an example of the reflected electron image of the voltage nonlinear resistor obtained in the Example. It is an example of the reflected electron image of the voltage nonlinear resistor which consists of a sintered compact with small A / B obtained in the Example. It is an example of the backscattered electron image of the voltage nonlinear resistor which consists of a sintered compact with large A / B obtained in the Example. It is a graph which shows the relationship with the area ratio (A) of the bismuth oxide phase which occupies in the cross section of the sintered compact obtained by the Example and the comparative example, and a leakage current (mA). The ratio of the area ratio (A) of the bismuth oxide phase and the area ratio (B) of the spinel particles (A / B) to the leakage current (mA) in the cross sections of the sintered bodies obtained in Examples and Comparative Examples It is a graph which shows a relationship.

Embodiments of the present invention will be described below.
Embodiment 1 FIG.
As shown in FIG. 1, the voltage nonlinear resistor according to the embodiment of the present invention is mainly composed of zinc oxide particles 1, spinel particles 2 mainly composed of zinc and antimony, and a bismuth oxide phase 3. It consists of a sintered body in which twin boundaries 4 exist in the zinc crystal particles. Furthermore, the microstructure analysis shows that the bismuth oxide phase contains at least one alkali metal selected from the group consisting of potassium and sodium in the range of 0.036 atomic% to 0.176 atomic%. It is known that the alkali metal present in the bismuth oxide phase at a certain ratio is considered to contribute greatly to the improvement of the electric charge lifetime characteristics and the suppression of the deterioration of the voltage nonlinearity due to the post heat treatment. The area ratio (A) of the bismuth oxide phase 3 occupying in the cross section of the sintered body is in the range of 2% to 8%, and the area of the bismuth oxide phase 3 occupying in the cross section of the sintered body. The ratio (A / B) between the ratio (A) and the area ratio (B) of the spinel particles 2 is in the range of 0.3 to 1.5. When the area ratio (A) of the bismuth oxide phase 3 and the ratio (A / B) of the area ratio (A) of the bismuth oxide phase 3 to the area ratio (B) of the spinel particles 2 are outside the above ranges, The leakage current increases significantly. The ratio of the area ratio A of the bismuth oxide phase 3 and the area ratio A of the bismuth oxide phase 3 to the area ratio B of the spinel particles 2 is appropriately changed by changing the composition of the raw material composition to be fired, the firing temperature, and the firing time. The predetermined range can be adjusted.
Such a voltage non-linear resistor comprises a raw material composition containing at least one alkali metal selected from the group consisting of zinc oxide as a main component, bismuth, antimony, and potassium and sodium at 900 ° C. or more. After being fired, a heat treatment (hereinafter referred to as post-heat treatment) at 400 ° C. or more and 600 ° C. or less is obtained.

  Zinc oxide is contained in the raw material composition in the range of 90 mol% or more and 98 mol% or less from the comprehensive viewpoints of improvement of voltage nonlinearity, improvement of thermal stability, improvement of energy resistance and extension of life. It is desirable that it is contained in the range of 95 mol% or more and 98 mol% or less. As zinc oxide, it is usually preferable to use a powder having an average particle diameter of 1 μm or less.

  Bismuth and antimony are preferably contained in the raw material composition in the range of 0.5 mol% or more and 2 mol% or less in total from the viewpoint of improving voltage nonlinearity and improving thermal stability. More preferably, it is contained in the range of 6 mol% or more and 1.5 mol% or less. Bismuth and antimony can be used in the form of oxides, chlorides, etc. Usually, it is preferable to use powder having an average particle diameter of 1 μm or less.

In the raw material composition, at least one alkali metal selected from the group consisting of potassium and sodium is contained in the raw material composition in an amount of 0.013 from the viewpoint of improving the voltage non-linearity and improving the electric charging life characteristics. It is added in a range of from mol% to 0.026 mol%. When the addition amount of the alkali metal is less than 0.013 mol%, the voltage nonlinearity and the electric charging life characteristic after the post-heat treatment are remarkably deteriorated, and when it exceeds 0.026 mol%, the electric charging life characteristic is reduced. It becomes insufficient. This alkali metal is usually preferably blended as an Na ₂ CO ₃ powder and K ₂ CO ₃ powder having an average particle size of 1 μm or less, or as an aqueous solution in which these are dissolved. If an alkali metal is added to the raw material composition in this range, at least one alkali metal selected from the group consisting of potassium and sodium is 0.036 atomic% or more in the bismuth oxide phase of the obtained sintered body. It can exist in the range of 0.176 atomic% or less. Conventionally, it has been recognized that as the amount of sodium or potassium in the voltage nonlinear resistor increases, the electrical characteristics deteriorate, and it is attempted to achieve excellent voltage nonlinearity by reducing the amount of contamination as much as possible. Attempts have been made. However, as a result of various studies on the composition and firing temperature of a composition containing zinc oxide as a main component and containing bismuth and antimony, the present inventors have surprisingly found that an alkali metal such as sodium is 0.013 mol% or more. By firing the raw material composition added in the range of 0.026 mol% or less at 900 ° C. or higher, preferably 900 ° C. or higher and 1000 ° C. or lower, deterioration of voltage non-linearity due to post-heat treatment at about 500 ° C. after baking is reduced. It has been found that it can be significantly suppressed.

  In addition to the above-described components, the raw material composition in the present embodiment further improves thermal stability, voltage nonlinearity, and electrical charging life, such as nickel oxide, manganese dioxide, chromium oxide, cobalt oxide, silicon dioxide, etc. May be added. The amount of these components added is usually in the range of 0.1 mol% to 2 mol% in the composition. Moreover, as these oxides, it is usually preferable to use a powder having an average particle diameter of 1 μm or less. In order to further improve the voltage nonlinearity, aluminum nitrate may be added to the composition in the range of 0.001 mol% to 0.01 mol%. Further, in order to further improve the voltage nonlinearity, to reduce the fine pores (pores) in the sintered body and to further improve the energy resistance, the range of 0.01 mol% or more and 0.2 mol% or less in the composition. Boric acid may be added.

Next, a method for manufacturing the voltage nonlinear resistor according to the embodiment of the present invention will be specifically described. After preparing a raw material composition composed of the above-mentioned raw materials, a binder (binder) such as water, a dispersing agent and polyvinyl alcohol is added thereto, and the mixture is sufficiently pulverized and mixed to produce a slurry having a uniform composition. To do. This slurry is dried and granulated with a spray dryer to obtain a granulated product. The obtained granules to obtain a molded body having a predetermined shape by molding, for example, 200 kgf / cm ² or more 500 kgf / cm ² or less of the molding pressure. Next, the molded body is heated to about 450 ° C. in the air or oxygen atmosphere to remove the binder, and subsequently fired at 900 ° C. or higher, preferably 900 ° C. or higher and 1000 ° C. or lower, and then 400 ° C. or higher and 600 ° C. A post-heat treatment is performed at a temperature below ℃ to obtain a sintered body. If necessary, an electrode may be formed on the sintered body by, for example, aluminum spraying, or a side high resistance layer may be formed by baking a glass or introducing a diffusion layer having a high resistance value.

  Furthermore, if the voltage non-linear resistor obtained by this embodiment is mounted on a lightning arrester as a single body or stacked, it is possible to obtain a lightning arrester with excellent protection characteristics and life performance and high reliability.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these.
<Examples 1-5 and Comparative Examples 1-4>
0.5 mol% to 2.5 mol% bismuth oxide (Bi ₂ O ₃ ) powder, 0.3 mol% to 1.0 mol% antimony oxide (Sb ₂ O ₃ ) powder as shown in Table 1 0.5 mol% nickel oxide (NiO) powder, 0.5 mol% manganese dioxide (MnO ₂ ) powder, 0.1 mol% chromium oxide (Cr ₂ O ₃ ) powder, 0.4 mol% Cobalt oxide (Co ₃ O ₄ ) powder, 0.004 mol% aluminum nitrate (Al (NO ₃ ) ₃ .9H ₂ O), 0.16 mol% boric acid (H ₃ BO ₃ ), 0.026 mol % Sodium carbonate (Na ₂ CO ₃ ), and the raw material compositions 1 to 9 with the balance being zinc oxide (ZnO) powder were prepared. In addition, industrial raw materials or reagents were used for the respective raw materials, and all powder raw materials having an average particle diameter of 1 μm or less were used.

Pure water, a dispersant, and a binder (binder) were added to each raw material composition, and pulverization and mixing were sufficiently performed to prepare a slurry having a uniform composition. The produced slurry was granulated with a spray dryer, and the obtained granulated powder was molded at a molding pressure of 500 kgf / cm ² to obtain a disk-shaped molded body having a diameter of about 40 mm and a thickness of about 10 mm.

  The molded body was heat-treated at 450 ° C. for 5 hours in the atmosphere (debinding step), and then fired at a firing temperature of 1000 ° C. for 5 hours (firing step). The temperature increase and decrease rate was 50 ° C./hour. A side high resistance layer 6 (resin) for preventing side flashing when an impulse voltage is applied is applied to the side surface of the sintered body 5 thus obtained, and aluminum electrodes 7 are formed on both sides of the disk by aluminum spraying. A sample for evaluation was used. A schematic cross-sectional view of the sample is shown in FIG.

  The thermal stability of the prepared sample was evaluated by measuring the value of the current that flows when the sample is heated to 120 ° C. and a voltage at which the electric rate is 90% is applied when the temperature becomes constant. The results are shown in Table 2. In addition, the sample after the temperature characteristic evaluation was cut to about 5 mm square to observe the fine structure of the sintered body, the surface was polished, and then etched with hydrochloric acid for about 10 seconds to clarify the grain boundaries. went. After washing with pure water, a carbon film is coated to prevent charge-up, and the area ratio (A) occupied by the bismuth oxide phase and the area ratio (B) occupied by the spinel particles in the observation region are measured using image analysis. Furthermore, A / B was calculated from the results. The results are shown in Table 2. As a result of observation, the obtained sintered body had a fine structure roughly composed of zinc oxide particles, spinel particles, and a bismuth oxide phase existing near the triple point of the grain boundary. In particular, since the baking was performed at 1000 ° C., it was possible to suppress the added bismuth oxide from evaporating during the baking, and many bismuth oxide phases existed in the vicinity of the triple point. An example of the reflected electron image (COMPO image) of the part used for the actual analysis is shown in FIG. The part shining white is the bismuth oxide phase. FIG. 4 shows an example of a reflected electron image (COMPO image) of a voltage non-linear resistor made of a sintered body having a small A / B, and the reflection of the voltage non-linear resistor made of a sintered body having a large A / B. An example of an electronic image (COMPO image) is shown in FIG.

  Further, FIG. 6 shows the relationship between the area ratio A (%) and the leakage current (mA) in Examples 1 to 5 and Comparative Examples 1 to 4, and the relationship between the area ratio A / B and the leakage current (mA). As shown in FIG. As apparent from FIGS. 6 and 7, when either the area ratio A (%) or the area ratio A / B is outside the numerical range defined in the present invention, the leakage current increases and the temperature characteristics deteriorate. It turns out that there is a tendency. When the leakage current at 120 ° C. exceeds 1.5 mA, the amount of heat generated by the element increases, and the leakage current further increases. In order to suppress this, it is necessary to take heat dissipation measures such as heat dissipation fins inside the lightning arrester, which complicates the structure of the lightning arrester. On the other hand, when the area ratio A (%) and the area ratio A / B are within the numerical ranges defined in the present invention, it is considered that the stability of the grain boundary level is increased and the thermal stability at high temperature is increased. It is done.

<Examples 6 to 17 and Comparative Examples 5 to 14>
0.9 mole% of bismuth oxide (Bi ₂ O ₃₎ powder, 0.4 mole% of antimony oxide (Sb ₂ O ₃₎ powder, 0.5 mole% of nickel oxide (NiO) powder, 0.5 mol% Manganese dioxide (MnO ₂ ) powder, 0.1 mol% chromium oxide (Cr ₂ O ₃ ) powder, 0.4 mol% cobalt oxide (Co ₃ O ₄ ) powder, 0.004 mol% aluminum nitrate ( Al (NO ₃ ) ₃ · 9H ₂ O) and 0.16 mol% boric acid (H ₃ BO ₃ ) are used as the basic composition, and Na ₂ CO ₃ or K ₂ CO ₃ is added to the composition shown in Table 3. The raw material composition was prepared. The balance is zinc oxide (ZnO). In addition, industrial raw materials or reagents were used for the respective raw materials, and all powder raw materials having an average particle diameter of 1 μm or less were used.

  Next, a disk-shaped molded body was obtained in the same manner as in Examples 1 to 5, and the molded body was heat-treated in the atmosphere at 450 ° C. for 5 hours (debinding step), and then at the firing temperature shown in Table 3 for 5 hours Firing was performed (firing step). The temperature increase and decrease rate was 50 ° C./hour. Further, the sintered body was heat-treated in the atmosphere at 500 ° C. for 5 hours (post heat treatment step). Using the obtained sintered body, a sample for evaluation was produced in the same manner as in Examples 1-5.

For the samples of Examples 6 to 17 and Comparative Examples 5 to 14, the area ratio (A) occupied by the bismuth oxide phase and the area ratio (B) occupied by the spinel particles were analyzed using image analysis in the same manner as in Examples 1 to 5. Measurement was performed, and A / B was calculated from the results.
The quality of the voltage nonlinearity was evaluated by the flat rate (V _{2.35 kA} / V _{0.46 mA} ). For V _{2.35 kA,} an impulse voltage of 8 × 20 μs was applied to the sample, and the peak value was read as V _{2.35 kA} . V _{0.46 mA} was measured using an AC voltage (sine wave) of 60 Hz. When alternating current is applied, the current flowing through the sample is divided into a resistive component (Ir) and a capacitive component (Ic). Ir was extracted using a resistance leakage current extraction device. Specifically, the applied voltage at which Ir becomes 0.46 mA was read and set to V _{0.46 mA} .
By comparing the flat rate before and after the post heat treatment, the deterioration rate of the flat rate was evaluated. The deterioration rate was calculated according to the following formula.
(Flatness after post-heat treatment-flatness before post-heat treatment) ÷ flatness before post-heat treatment x 100 (%)
The post-heat treatment samples were evaluated for changes in Ir over time under the conditions of 120 ° C. and a charging rate of 90%, and the charging life characteristics were evaluated based on the increase and decrease. The pass / fail judgment of the charging life was determined to pass if the Ir at the time of voltage application did not show an increasing tendency.
The area ratio (A) occupied by these bismuth oxide phases, the ratio (A / B) of the area ratio occupied by the bismuth oxide phase and the area ratio occupied by spinel particles, thermal stability, flatness rate, deterioration rate, and electric charge life characteristics Table 4 shows the evaluation results.

  From Table 4, it can be seen that in the samples to which sodium and potassium are not added (Comparative Examples 5 and 10), the charging life after post-heat treatment is poor and the deterioration rate is large. When the amount of sodium or potassium added is increased to 0.013 mol%, the electric charging life is improved, and the deterioration rate is further reduced. As a result, a good flatness ratio of about 1.6 is obtained after post-heat treatment. You can see that However, it can be seen that when the addition amount of sodium or potassium is further increased to 0.052 mol%, the electric charging life characteristics become poor. That is, by adding at least one alkali metal selected from the group consisting of sodium and potassium in the range of 0.013 mol% or more and 0.026 mol% or less, excellent voltage non-linearity and charging life characteristics are obtained. It can be seen that a voltage non-linear resistor having both of the above can be obtained.

  Sodium and potassium are generally known to be elements that deteriorate the electrical characteristics of the voltage nonlinear resistor. Therefore, a technique for obtaining excellent voltage non-linearity by minimizing the mixing amount has been disclosed so far (for example, JP-A-8-138910). However, since the technique known so far has a firing temperature of at least 1100 ° C., the knowledge obtained in the present invention is considered to be a unique effect with a firing temperature of 1000 ° C. or less.

  In addition, it is known that when lithium, which is an alkali metal, is added to a voltage nonlinear resistor, the resistance of zinc oxide is greatly increased, and the voltage nonlinear resistor is made almost in the state of an insulator. A lithium addition experiment was conducted as in the case of sodium and potassium, but the sample was in a state close to an insulator and the electrical characteristics could not be evaluated. That is, it was confirmed that lithium has an effect of remarkably increasing the resistance of the voltage nonlinear resistor regardless of the firing temperature. From this, the voltage nonlinear resistor having both excellent voltage nonlinearity and charging life characteristic is 0.013 mol% or more of at least one alkali metal selected from the group consisting of sodium and potassium. The effect obtained when added in the range of .026 mol% or less and calcined at 1000 ° C. or less is considered to be a completely unique effect.

  Thus, since the addition of sodium and potassium has a great influence on the quality of the electric life, sodium and potassium are considered to be contained in the bismuth oxide phase that greatly affects the electric life. Therefore, quantitative analysis of the bismuth oxide phase existing at the triple point of the sample was performed at different locations (2 to 3 locations).

Specifically, the samples of Examples 6 to 11 and Comparative Examples 5 to 9 were cut to about 5 mm square, the surface was polished, and then etched with hydrochloric acid for about 10 seconds in order to clarify the grain boundaries. After washing with pure water, a carbon film was coated by vapor deposition to prevent charge-up, and quantitative analysis of sodium and potassium content was performed using a high performance electron probe microanalyzer (EPMA: Electron Probe Microanalyzer) manufactured by JEOL. . The EPMA used for the analysis is a device equipped with a field emission FE (Field Emission) electron gun, and is equipped with a wavelength dispersive spectrometer (WDS) capable of analyzing trace elements in a minute region.
Table 5 shows the results of quantitative analysis of sodium and potassium in the bismuth oxide phase.

Sodium or potassium was detected in the sample to which 0.013 mol% or more of sodium or potassium was added. When collated with the deterioration rate and charging life characteristics of Table 4, in the samples (Examples 6 to 11) to which sodium or potassium was added at a ratio of 0.013 mol% or more and 0.026 mol% or less, It can be seen that sodium or potassium is detected in the range of 0.036 atomic% or more and 0.176 atomic% or less, and the charging lifetime characteristics are improved and the deterioration rate is reduced. However, in the sample (Comparative Examples 7 and 9) containing 0.052 mol% of sodium or potassium, 0.222 atomic% or more of sodium or potassium is detected in the bismuth oxide phase, and the deterioration rate is greatly increased. The charging life is poor.
From the results of this quantitative analysis, in the sample where the deterioration rate was suppressed and the flatness after post-heat treatment was reduced, and at the same time, good electric charge lifetime characteristics were obtained, the bismuth oxide phase in the microstructure in the sintered body was The results of a series of experiments and analyzes revealed that sodium or potassium was present and the amount was 0.036 atomic% to 0.176 atomic%.

  From the above, a voltage non-linear resistor composed of a sintered body mainly composed of zinc oxide particles, spinel particles mainly composed of zinc and antimony, and a bismuth oxide phase, and in the bismuth oxide phase, The area ratio of the bismuth oxide phase occupying in the cross section of the sintered body is contained in the range of 0.036 atomic% or more and 0.176 atomic% or less of at least one alkali metal selected from the group consisting of potassium and sodium (A ) Is in the range of 2% to 8%, and the ratio (A / B) of the area ratio (A) of the bismuth oxide phase to the area ratio (B) of the spinel particles in the cross section of the sintered body is 0.00. By being in the range of 3 or more and 1.5 or less, the deterioration rate after post-heat treatment is suppressed, and as a result, a voltage nonlinear resistor having excellent voltage nonlinearity, electrical charging life characteristics and thermal stability is obtained. Realized.

  1 zinc oxide particle, 2 spinel particle, 3 bismuth oxide phase, 4 twin boundary, 5 sintered body, 6 side high resistance layer, 7 aluminum electrode.

Claims (2)

  A voltage non-linear resistor composed of a sintered body mainly composed of zinc oxide particles, spinel particles mainly composed of zinc and antimony, and a bismuth oxide phase, and from potassium and sodium in the bismuth oxide phase. At least one alkali metal selected from the group consisting of 0.036 atomic% and 0.176 atomic% is included, and the area ratio (A) of the bismuth oxide phase in the cross section of the sintered body is 2%. The ratio (A / B) of the area ratio (A) of the bismuth oxide phase and the area ratio (B) of the spinel particles in the cross section of the sintered body is in the range of 0.3 to 1. A voltage non-linear resistor having a range of 5 or less.   A lightning arrester comprising the voltage nonlinear resistor according to claim 1.

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