KR101441237B1 - Vanadium-based zinc oxide varistor and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a vanadium-based zinc oxide (ZnO-V2O5) varistor and to a new vanadium-based zinc oxide varistor and a manufacturing method thereof. The varistor obtains excellent non-linearity as well as stability during prolonged use by further adding an appropriate amount of bismuth oxide (Bi2O3) in the vanadium-based zinc oxide varistor (ZnO-V2O5-MnO2-Nb2O5) capable of co-firing with a silver (Ag) internal electrode.

Description

Technical Field The present invention relates to a vanadium-based zinc oxide varistor and a manufacturing method thereof,

The present invention relates to a vanadium-based zinc oxide (ZnO-V ₂ O ₅ ) varistor, and more particularly, to a vanadium-based zinc oxide varistor (ZnO-V ₂ O ₅ -MnO ₂ -Nb ₂ O (Bi ₂ O ₃ ) is added to an amorphous zirconium oxide (ZnO) ₅ in order to ensure excellent nonlinearity and to ensure the stability of the varistor even in prolonged use, and a method for producing the same will be.

Transient overvoltages (such as surges) can seriously affect all electronic systems, especially semiconductor devices such as diodes, transistors, and integrated circuits, resulting in malfunction or circuit breakdown.

Since it is virtually impossible to eliminate internal or external transient overvoltages in a system configuration, it is common to overcome transient overvoltage as a simple alternative to improve the insulation strength of the device and system.

However, since mobile electronic devices such as a tablet PC, a smart phone, and a digital camera have a strong demand for miniaturization, the method of improving the insulation strength is not suitable. Therefore, the resistance is automatically changed in response to the voltage applied to the system It is desirable to apply other alternatives for applying the varistor element.

The varistor element is a nonlinear resistor whose resistance varies according to the voltage. The varistor element is connected in parallel with the protection device and operates as an insulator which exhibits high impedance in normal times. When the transient overvoltage is invaded, the resistance is rapidly reduced, And means for protecting the subject to be protected by discharging the overvoltage.

In recent years, zinc oxide varistors, which are sintered by mixing non-linearity with zinc oxide (ZnO) and enhancing stability, are in the spotlight. Almost all commercially available zinc oxide varistors have a nonlinearity- Depending on the type, it is not an exaggeration to say that it is a bismuth-based (ZnO-Bi ₂ O ₃ ) varistor or a praseodymium-based (ZnO-Pr ₆ O ₁₁ ) varistor.

However, these two kinds of zinc oxide varistors have excellent performance as a varistor element, but they have one disadvantage. That is, when the multilayer chip varistor is laminated, silver (Ag) can not be applied to the internal electrodes. This is because of the limitations of the process that the bismuth-based varistor and the praseodymium-based varistor must be sintered at a temperature of 1000 ° C. or higher, which is higher than the melting point of the silver (Ag), which is 961 ° C. Thus, palladium (Pd) Is used as the material of the internal electrode.

In recent years, a vanadium-based (ZnO-V ₂ O ₅ ) varistor has attracted attention as an alternative to this. Since vanadium oxide has a melting point of only 690 ° C., liquid phase sintering is possible at a relatively low temperature near 900 ° C. This is because simultaneous firing can be performed using silver (Ag), which is cheaper than expensive metals such as palladium (Pd) and platinum (Pt), as internal electrodes of multilayer chip varistors.

However, studies on vanadium-based zinc oxide varistors have remained at an early stage, and it is reported that appropriate additives are required to obtain high nonlinearity, and MnO ₂ and Nb ₂ O ₅ have been introduced as additives . Therefore, in-depth study on the composition and sintering temperature that can secure high nonlinearity and stability is still insufficient.

The present invention aims to provide a vanadium-based zinc oxide varistor, which is a new vanadium-based zinc oxide varistor different in composition from the vanadium-based zinc oxide varistor as reported so far, and a method for producing the same.

The vanadium-based zinc oxide varistor according to the present invention is a vanadium-based zinc oxide varistor comprising zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ) and niobium oxide (Nb ₂ O ₅ ) Oxide (Bi ₂ O ₃ ) is added.

In an embodiment of the present invention, the bismuth oxide is added in an amount of 0.1 mol% or less.

More preferably, the bismuth oxide may be added in an amount of 0.025 mol% or less.

On the other hand, the bismuth oxide may be added in such a content that the nonlinear coefficient (?) Exceeds 52.

Further, the bismuth oxide has a nonlinear coefficient (alpha) of 20 or more after the DC accelerated aging stress test performed under the conditions of 0.85E _1mA / 85 ° C / 24h (where E _1mA is the voltage when the current density is 1.0 mA / By weight based on the total weight of the composition.

The method for producing the vanadium-based zinc oxide varistor according to the present invention is characterized in that the zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ), niobium oxide (Nb ₂ O ₅ ) and bismuth oxide ₂ O ₃₎ a first step of weighing; and, after mixing the weighed compositions as ball milling to mix with acetone, and after mixing with polyvinyl butyral (PVB) binder and acetone, a second step of drying; and, A third step of making the dried powder composition into a desired shaped body and sintering and then polishing both surfaces of the sintered body; And a fourth step of applying a silver electrode to the polished sintered body and performing a package treatment.

In the method for producing the vanadium-based zinc oxide varistor of the present invention, the bismuth oxide is added in an amount of 0.1 mol% or less.

More preferably, the bismuth oxide may be added in an amount of 0.025 mol% or less.

On the other hand, the bismuth oxide may be added in such a content that the nonlinear coefficient (?) Exceeds 52.

Further, the bismuth oxide has a nonlinear coefficient (alpha) of 20 or more after the DC accelerated aging stress test performed under the conditions of 0.85E _1mA / 85 ° C / 24h (where E _1mA is the voltage when the current density is 1.0 mA / By weight based on the total weight of the composition.

The vanadium-based zinc oxide varistor according to the present invention can be obtained by appropriately adjusting the content of bismuth oxide (Bi ₂ O ₃ ), and when compared with the case where no bismuth oxide is added, when the transient overvoltage is applied while maintaining the same level of stress tolerance The nonlinear coefficient (?), Which is an index of the varistor performance of the nonlinear device, can achieve a further improved and highly desirable performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a transcriptional scanning micrograph of five specimens of a vanadium-based zinc oxide varistor with different contents of bismuth oxide (Bi ₂ O ₃ ).
2 is an XRD pattern according to a change in the content of bismuth oxide (Bi ₂ O ₃ ).
Figure 3 shows the results of an EDS analysis of the crystallite phase.
4 is a graph showing voltage-current (EJ) characteristics for five specimens according to changes in the content of bismuth oxide (Bi ₂ O ₃ );
5 is a graph showing changes in breakdown field, nonlinear coefficient, and leakage current density with changes in the content of bismuth oxide (Bi ₂ O ₃ );
6 shows the behavior of the leakage current (I _L ) during the DC accelerated aging stress test under the conditions of 0.85E _1mA / 85 ° C / 24h.
7 is a graph showing voltage-current (EJ) characteristics before and after DC accelerated aging stress for five kinds of specimens (a) to (e) with different contents of Bi ₂ O ₃ .

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a process for preparing a vanadium-based zinc oxide varistor according to the present invention and a process for evaluating the electrical and structural characteristics of the vanadium-based zinc oxide varistor will be described in detail.

Production of specimen

The vanadium oxide zinc oxide varistor according to the present invention has a composition of ZnO-V ₂ O ₅ -MnO ₂ -Nb ₂ O ₅ -Bi ₂ O ₃ , and vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ) The composition ratio of niobium oxide (Nb ₂ O ₅ ) was fixed and the contents of zinc oxide (ZnO) and minor amount of bismuth oxide (Bi ₂ O ₃ ) were changed.

Manganese oxide, MnO ₂ most commonly added is 1.0~3.0 mol%, the vanadium oxide is V ₂ O ₅ is 0.2~0.8 mol%, the niobium oxide is Nb ₂ O ₅ may be added in the range of 0.05~0.3 mol%, The content of Bi ₂ O ₃ , which is a bismuth oxide, is 0.0, 0.025. 0.05, 0.1 and 0.25 mol%, respectively. Except for impurities that can not be avoided in the preparation of specimens, all of the components are made of ZnO.

The composition used in the preparation of the actual specimen was ZnO of 97.4-X mol%, V ₂ O ₅ of 0.5 mol%, MnO ₂ of 2.0 mol%, Nb ₂ O ₅ of 0.1 mol%, Bi ₂ O of X mol% ₃ (X = 0.0, 0.025, 0.05, 0.1, 0.25).

Each ingredient was made of reagent grade raw materials with a purity of more than 99.9%, and weighed to an error range of 10 μg with electronic scales according to each composition of 5 specimens. Then, zirconia balls, acetone and weighed samples were put in a polypropylene container and mixed by ball milling for 24 hours.

The mixture slurry was mixed with a 0.8 wt% polyvinyl butyral (PVB) binder and a beaker containing acetone and mixed with a magnetic stir bar, which was dried and assembled with a 100-mesh sieve.

The powder prepared in the above process was molded into a disk shape having a diameter of 10 mm and a thickness of 1.5 mm under a uniaxial pressure of 100 MPa and then sintered at a temperature of 900 캜 for 3 hours in the air. Respectively. Heating and cooling were performed at a rate of 4 ° C / min.

The final specimens were lapped and polished to a diameter of 8 mm and a thickness of 1.0 mm. Silver electrodes with a diameter of 5 mm were heat-treated at 550 ° C for 10 minutes on both sides of each specimen.

Lastly, lead wires were soldered on both silver electrodes, immersed in thermoplastic resin powder, and packaged to complete five different specimens with different contents of bismuth oxide (Bi ₂ O ₃ ).

Microstructure characteristics

The specimens prepared in the above procedure were wrapped with SiC abrasive paper, mirror-polished with 0.3 μm Al ₂ O ₃ powder, chemically etched in a ₁ HClO ₄ : 1000 H ₂ O solution for 25 seconds at 25 ° C., The characteristics were observed with a scanning electron microscope (FESEM, Quanta 200, FEI, Brno, Czech).

The average grain size (d) is calculated from the linear crossing equation d = 1.56L / MN, where L is any test line on the microscope photograph, M is the magnification of the microscope and N is the number of effective crossings with the test line Respectively.

The crystalline phase was analyzed by XDD (X-ray diffractometer, X'pert-Pro MPD, XRD) using CuKα radiation filtered with nickel, Panalytical, Almelo, the Netherland).

The sintered density (rho) was measured using a density measuring kit (238490) attached to an electronic balance (AG 245, Mettler Toledo International Inc., Greifensee, Switzerland).

FIG. 1 is a transcriptional scanning micrograph of five specimens of vanadium-based zinc oxide varistors differing in the content of bismuth oxide (Bi ₂ O ₃ ). The morphology of grains and grain boundaries on all types of specimen surfaces It can be seen clearly.

The average grain size (d) increased significantly from 5.6 ㎛ to 7.2 ㎛ as Bi ₂ O ₃ content increased, suggesting that Bi ₂ O ₃ acted as an enhancer of grain growth.

Sintered density (ρ) are were decreased as the content of Bi ₂ O ₃ increased to 0.05 mol% at 5.51g / cm ³ to 5.37g / cm ^3, even when increasing the content of Bi ₂ O ₃ to 0.25 mol% 5.40 g / cm < ³ > (theoretical density of zinc oxide is 5.78 g / cm < ³ >). Overall, the addition of Bi ₂ O ₃ leads to a reduction in sintering density, which is believed to be due to the influence of BiVO ₄ , a volatile liquid adjuvant associated with Bi ₂ O ₃ . The detailed values of the microstructural parameters such as the average grain size (d) and the sintered density (rho) are summarized in Table 1 together with the respective parameters of the electrical characteristics to be described later.

The XRD pattern according to the content of Bi ₂ O ₃ is shown in FIG. In the case of Bi ₂ O ₃ is not added to the specimen (a), Zn ₃ with a main crystal phase of the hexagonal zinc oxide _{(VO 4) 2, ZnV 2} O 4, V 2 O 5 in some portions crystal phase and a manganese-rich phase (Mn-rich phase). In addition, specimens (b) to (e) to which Bi ₂ O ₃ is added show another additional crystal phase such as BiVO ₄ .

The presence of the sub crystalline phase is also supported by FIG. 3 showing the results of the EDS analysis. According to the EDS analysis of Figure 3 niobium (Nb) and vanadium, manganese, including (V) - rich phase, and some other part is created by the cooperation of Bi ₂ O ₃ is and BiVO ₄ containing niobium (Nb) The presence of a crystal phase is confirmed.

Electrical characteristic measurement

The electrical properties of each specimen were evaluated using voltage-current (E-J) characteristics, which were measured using a High Voltage Source-Measure Unit (Keithley 237, Keithley Instruments Inc., Cleveland, OH, USA).

Here, the breakdown field (E _{1 mA} ) was defined as the voltage at a current density of 1.0 mA / cm 2 and the leakage current density (J _L ) at a current of 0.80 E _{1 mA} .

The nonlinear coefficient α is defined by the empirical formula J = K · E ^α where J is the current density, E is the applied electric field, and K is a constant, and is calculated by the following equation (1).

_{α = (logJ 2 -logJ 1)} / (logE 2 -logE 1) ....................... Eq. (1)

(Where J ₁ = 1.0 mA / cm ² , J ₂ = 10 mA / cm ² , E ₁ and E ₂ are electric fields corresponding to J ₁ and J ₂ , respectively)

FIG. 4 shows voltage-current (EJ) characteristics for five specimens according to changes in the content of Bi ₂ O ₃ .

The voltage-current (E-J) characteristic curve of the varistor is divided into two distinct regions. One is the extremely low impedance (low state) region of the extremely high impedance before the breakdown field, and the other is the remarkably high current region (the on state) of the extremely low impedance after the breakdown field. Sharpness indicates that the characteristics of the varistor are even better.

The best varistor effect was obtained for the specimen with a Bi ₂ O ₃ content of 0.025 mol% and the voltage-current (EJ) characteristic parameter fmf of each specimen was summarized together with the microstructural parameters in Table 1 below.

Microstructure and voltage-current (E-J) characteristic parameters for the five specimens of the present invention Bi ₂ O ₃ content
(mol%) d
(탆) ρ
(g / cm3) E _1mA
(V / cm) v _gb
(V / gb) alpha J _L
(㎂ / ㎠)      0 5.6 5.51 4874 2.7 51.0 56.8      0.025 5.9 5.43 4355 2.6 60.0 20.0      0.05 6.3 5.37 3917 2.5 51.1 41.9      0.1 6.9 5.39 2972 2.0 38.9 55.4      0.25 7.2 5.40 2205 1.6 31.2 45.3

5 (a) shows the functional relationship of the breakdown field (E _{1 mA} ) to the Bi ₂ O ₃ content. The breakdown field (E _1mA ) decreased from 4874 V / ㎝ to 2205 V / ㎝ as Bi ₂ O ₃ content increased.

The reduction of the breakdown field (E _1mA ) with increasing Bi ₂ O ₃ content can be explained from the equation E _1mA = v _gb / d, where d is the grain size and v _gb is the breakdown voltage per grain. The above equation _{(E 1mA = v gb / d} ) As the size (d) of the average crystal grain, even if the mouth gyedang breakdown voltage (v _gb) predetermined by taking the number of decrease in the grain boundary breakdown field (E _1mA) . Referring to Table 1, the decrease in the breakdown field (E _1mA ) with increasing Bi ₂ O ₃ content is due to the increase in the average grain size (d) as well as the decrease in breakdown voltage (v _gb ) per grain Able to know.

The nonlinearity of the varistor is better as the value of the nonlinear coefficient (α) representing the tangential slope of the yield region is larger, and the functional relationship of the nonlinear coefficient (α) to the content of Bi ₂ O ₃ is shown in FIG. 5 (b).

5 (b), when the content of Bi ₂ O ₃ is increased to 0.025 mol%, the nonlinear coefficient increases from 51.0 to 60.0, but when the content of Bi ₂ O ₃ is further increased to 0.25 mol% The nonlinear coefficient (α) is decreasing to 31.2. It is considered that the reason why the nonlinear coefficient (?) Decreases when the Bi ₂ O ₃ content exceeds 0.025 mol% is due to the decrease of the potential barrier height due to the abrupt change of the electron state at the grain boundaries.

The relationship between the content of Bi ₂ O ₃ and the leakage current density (J _L ) is shown in FIG. 5 (c). The leakage current density is the represent the amplitude, 0.025 mol% of Bi ₂ O ₃ is the specimen (J _L) is very low leakage current density, among ever reported vanadium zinc oxide varistor addition levels depending on the contents in the Bi ₂ O ₃ 20 [micro] A / cm < 2 >. In addition, such low leakage current density (J _L ) is comparable to conventional bismuth-based zinc oxide varistors and praseodymium-based zinc varistors.

Therefore, it can be seen that the vanadium oxide zinc oxide varistor of the present invention can realize low leakage current density as well as high nonlinearity by appropriately controlling the content of bismuth oxide (Bi ₂ O ₃ ).

DC  Accelerated aging stress measurement

In order to evaluate the stability of the nonlinearity and electrical characteristics of the varistor, the voltage-current (EJ) characteristics before stress application were measured for each specimen and DC accelerated aging stress test was performed at 0.85E _1mA / 85 ° C / 24h (EJ) characteristics were measured at room temperature and compared with each other.

The leakage current density (J _L ) was measured at 1 minute intervals during stress application using a high voltage source measurement unit (Keithley 237, Keithley Instruments Inc., Cleveland, OH, USA).

The degradation rate coefficient changes in the leakage current density (J _L) of the stress time while applying a stress _{(degradation rate coefficient) (K T} ) is _{I L = I L0 + K T} · t 1/2 ( Here, I _L Is the leakage current at time t, and I _L0 is the leakage current at t = 0).

6 is a graph showing the behavior of the leakage current (I _L ) during the DC accelerated aging stress test under the condition of 0.85E _1mA / 85 ° C / 24h. According to FIG. 6, corresponding to the content of Bi ₂ O ₃ , each specimen shows different leakage current (I _L ) behavior depending on stress application time.

The specimen (a) without Bi ₂ O ₃ shows a behavior in which the leakage current gradually saturates to a certain value according to the stress application time. On the other hand, the specimens (b) to (e) to which Bi ₂ O ₃ was added show a behavior in which the leakage current gradually increases as the stress application time increases. This aspect is referred to as a positive creep of the leakage current.

As the amount of Bi ₂ O ₃ added increases, the amount of positive creep of the leakage current gradually changes. Therefore, the increase of the Bi ₂ O ₃ content gradually weakens the stability of the varistor.

Obviously, the stability to stress is affected by the sintering density, the crystallite phase and the leakage current, and generally the low sintered density, the more crystalline phase, and the high leakage current weaken the resistance to stress. This is because the low sintered density and the more crystalline phases reduce the number of conduction paths and eventually increase the current density per grain and the high leakage current is due to the repetitive cycle between Joule heating and leakage current Leading to an increase in carrier generation, thereby degrading stability.

To Bi ₂ O ₃ doped sample (b) ~ (e) of the present invention, Bi ₂ O ₃ is not added to the specimen (a) the leakage current density (J _L) compared to the low (see Table 1) Leakage The positive creep phenomenon of the current is due to the relatively low sintered density and the effect of the more crystalline phase (BiVO ₄ ). In particular, the specimen (d) with 0.1 mol% of Bi ₂ O ₃ showed the worst stability with the lowest sintered density and the highest leakage current density.

The stability of the varistor (specimen) can be approximated by the deterioration factor coefficient (K _T ), which indicates the degree of aging. A relatively low degradation factor can generally be considered to mean better stability, even though the value does not indicate absolute stability. The deterioration rate coefficient (K _T ) is the slope of the leakage current during the stress application time, and the deterioration rate coefficient (K _T ) of each specimen is included in Table 2 since the results of the DC accelerated aging stress test are summarized.

Voltage-current (E-J) characteristics before and after DC accelerated aging stress on the five specimens of the present invention Bi ₂ O ₃ content
(mol%) stress
Condition K _T
(PA.h ^-1/2 ) E _1mA
(V / cm) % △ E _1mA alpha % △ α    0.0 Early - 4874 - 51.0 - After stress 8.1 4593 -5.8 22.6 -55.7    0.025 Early - 4355 - 60.0 - After stress 13.4 4013 -7.8 22.5 -62.5    0.05 Early - 3917 - 51.1 - After stress 16.9 3326 -15.1 12.2 -76.1    0.1 Early - 2972 - 38.9 - After stress 56.3 1617 -45.6 3.8 -90.2    0.25 Early - 2205 - 31.2 - After stress 30.7 1550 -29.7 5.9 -81.1

7 is five types of samples (a) ~ (e) DC accelerated aging stress before and after the voltage for which otherwise the content of Bi ₂ O ₃ - content of geotinde showing a current (EJ) characteristics, Bi ₂ O ₃ (EJ) characteristics after the application of the stress.

The specimen (a) without Bi ₂ O ₃ showed a small change in the voltage-current (EJ) characteristics before and after stress application, while the specimen (d) with Bi ₂ O ₃ added with 0.1 mol% (EJ) characteristics before and after the operation. This is consistent with the change in the leakage current (I _L ) before and after stress application according to the Bi ₂ O ₃ content in FIG.

Table 2 summarizes the rate of change of yielding field (% ΔE _1mA ) and the rate of change of nonlinear coefficient (% Δα) before and after stress application.

Looking at the rate of change of the breakdown electric field _{(% ΔE 1mA), Bi 2} O 3 is not added, the specimens showed the lowest rate of change (-5.8%), Bi ₂ O ₃ is added in the specimen is Bi ₂ O ₃ is 0.025 mol % Added specimen showed the smallest change rate (-7.8%). However, if the rate of change of the specimen to which 0.025 mol% of Bi ₂ O ₃ is added is more than -10% (-15.1%), the rate of change of the breakdown field when the Bi ₂ O _{3 content} is less than 0.025 mol% ΔE _{1 mA} ) can be maintained at almost the same level as when Bi ₂ O ₃ is not added.

On the other hand, the rate of change of the nonlinear coefficient (% Δα) shows that the Bi ₂ O ₃ is dropped by more than 50% in all specimens irrespective of the addition of Bi ₂ O ₃ . In the case where Bi ₂ O ₃ is added in an amount of 0.025 mol% or less, the nonlinear coefficient (α) of at least 20 is maintained even after the stress is applied. Therefore, it can be said that the most favorable result is obtained.

In conclusion, it can be concluded that the vanadium-based zinc oxide varistor according to the present invention, to which Bi ₂ O ₃ is added in an amount of 0.025 mol% or less, exhibits the best performance, and in comparison with the case where Bi ₂ O ₃ is not added The nonlinear coefficient (α), which is an index of the varistor performance when the transient overvoltage is applied while maintaining the same level of stress tolerance, is considered to have improved and highly desirable performance characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the scope of the present invention . Therefore, the true scope of protection of the present invention should be determined by the claims.

Claims (10)

A vanadium oxide zinc oxide varistor containing zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ) and niobium oxide (Nb ₂ O ₅ ) is added to a bismuth oxide (Bi ₂ O ₃ ) is added to the vanadium-based zinc oxide varistor. delete The method according to claim 1,
Wherein the bismuth oxide is added in an amount of 0.025 mol% or less. The method according to claim 1,
Wherein the bismuth oxide is added in such an amount that the nonlinear coefficient (?) Is greater than 52. The method according to claim 1,
The bismuth oxide has a nonlinear coefficient (α) exceeding 20 even after the DC accelerated aging stress test performed under the condition of 0.85E _{1 mA} / 85 ° C./24 h (where E _{1 mA} is the voltage when the current density is 1.0 mA / cm 2) By weight based on the total weight of the vanadium oxide zinc varistor. (Bi ₂ O ₃ ) added in an amount of not more than 0.1 mol% and zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ), niobium oxide (Nb ₂ O ₅ ) ;
A second step of mixing the weighed composition with acetone, ball milling, mixing with a polyvinyl butyral (PVB) binder and acetone, and drying;
A third step of making the dried powder composition into a desired shaped body and sintering and then polishing both surfaces of the sintered body; And
A fourth step of applying a silver electrode to the polished sintered body and performing a package treatment;
Based vanadium oxide varistor. delete The method according to claim 6,
Wherein the bismuth oxide is added in an amount of 0.025 mol% or less. The method according to claim 6,
Wherein the bismuth oxide is added in such an amount that the nonlinear coefficient (?) Is greater than 52. A method for producing a vanadium-based zinc oxide varistor, The method according to claim 6,
The bismuth oxide has a nonlinear coefficient (α) exceeding 20 even after the DC accelerated aging stress test performed under the condition of 0.85E _{1 mA} / 85 ° C./24 h (where E _{1 mA} is the voltage when the current density is 1.0 mA / cm 2) By weight based on the total weight of the vanadium-based zinc oxide varistor.

Images