KR102310618B1 - ZVMNYb-based varistor and manufacturing method for the same - Google Patents

Abstract

The present invention relates to a ZVMNYb-based varistor characterized by excellent nonlinear properties, high interfacial density of states, and high potential barrier height, and a method for manufacturing the same.
Further, it relates to a ZVMNYb-based varistor capable of acting as a donor based on a chemical defect reaction and a method for manufacturing the same.
The present invention can provide a chip varistor using the ZVMNYb-based varistor.

Description

ZVMNYb-based varistor and manufacturing method thereof

The present invention relates to a ZVMNYb-based varistor and a method for manufacturing the same, and more particularly, to a ZVMNYb-based varistor for protecting electronic circuit components used in electronic devices from surge and abnormal voltage, and a method for manufacturing the same.

A varistor refers to a device used to protect electronic circuits and components used in electronic devices such as mobile terminals from abnormal voltages such as surge and pulse noise. It is possible to effectively respond to noise regulations while ensuring the protection and operation stability of the device.

For example, LED TV. Smartphones, cameras, PCs, etc. can be very sensitive and vulnerable to surges, which are transient waveforms of current, voltage, and power in electrical and electronic circuits. At this time, 60-80% of the surge is generated inside the facility, and it can be said that the surge in the semiconductor device causes serious damage.

Such a varistor may mean a voltage-dependent resistor or a non-linear resistor. The resistance of the varistor changes according to the applied voltage, unlike the general resistance. Therefore, materials exhibiting the varistor effect must have microstructures such as pn junctions or active grain boundaries or active interfaces.

On the other hand, zinc oxide varistor containing zinc oxide can be manufactured by adding some additives to zinc oxide and firing at an appropriate temperature. The microstructure of the doped zinc oxide varistor is a polycrystalline structure composed of numerous semiconducting zinc oxide particles and grain boundaries. The grains are semiconductors with a bandgap of about 3.2 eV, and the grain boundaries are electron-active and have a very thin insulating layer. As a result, one semiconductor-insulating layer-semiconductor (SIS) structure constitutes microvaristors, and these microvaristors are randomly distributed throughout the sintered body.

Thus, sintering on zinc oxide doped with certain additives can produce unique microstructure and nonlinear properties in the conduction properties. Due to their excellent nonlinearity, zinc oxide varistors can be effectively applied to various passive and active components, to bypass electrical and electronic equipment from dangerous transient voltages, and electrical installations from lightning.

Commercial multilayer varistors today are broadly classified into three categories: bismuth-based, praseodymium-based, and borosilicate-lead-zinc glass-based. It is obtained by sintering at a temperature of 1000 °C or higher, and the inner electrode in the varistor is expensive palladium (Pd) or platinum (Pt).

Ceramic semiconductors can be sintered at low temperatures by adding _{V 2} O ₅ to ZnO varistors. That is, the ZnO-V ₂ O-based ceramic semiconductor may be sintered at 900° C. or less. This is advantageous because the ZnO-V ₂ O ₅ based ceramic semiconductor can be fired with an Ag electrode instead of expensive Pd or Pt.

However, there is a problem that the current ZnO-V ₂ O ₅ based ceramic semiconductor is not applied to the field due to characteristics and reliability.

(Patent Document 1) KR 10-1948718 B1

It is an object of the present invention to provide a ZVMNYb-based varistor and a method for manufacturing the same.

Another object of the present invention is to exhibit a very high resistance value below the breakdown voltage voltage, but exhibit excellent nonlinear characteristics showing a low resistance value above the breakdown voltage, and exhibit high interfacial state density and potential barrier height, thus improving stability and reliability. To provide a ZVMNYb-based varistor and a method for manufacturing the same.

Another object of the present invention is to provide a ZVMNYb-based varistor capable of acting as a donor based on a chemical-defect reaction and a manufacturing method thereof.

Another object of the present invention is to provide a chip varistor using the ZVMNYb-based varistor.

In order to achieve the above object, ZVMNYb-based varistor according to an embodiment of the present invention is zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ) and niobium oxide (Nb ₂ O ₅ ) It includes, and may further include _{ytterbium oxide (Yb 2} 0 _{3 ).}

The varistor comprises (97.4-x) mol% ZnO, 0.5 mol% V ₂ O ₅ , 2.0 mol% MnO ₂ , 0.1 mol% Nb ₂ O ₅ and x mol% Yb ₂ O ₃ , wherein x is from 0.05 to 0.25.

The varistor has a ceramic density (ρ) of 5.50 to 5.54 g/cm ³ .

The varistor has an average particle size of ZnO of 5.3 to 5.6 μm.

The varistor has a diffraction angle (θ) of an XRD pattern of 25.39 to 33.93°.

The varistor has a nonlinearity index (α) of 34.4 to 70.

The varistor has a leakage current density (J _L ) of 56.8 to 262.2 μA/cm ² .

The varistor acts as a donor based on a chemical-defect reaction, and the donor concentration is 2.46 × 10 ¹⁷ cm ^-3 to 7.41 × 10 ¹⁷ cm ^-3 .

The varistor has a barrier height Φb of 0.76 to 1.25 Ev.

In the chip varistor according to another embodiment of the present invention, a plurality of ZVMNYb-based varistors are stacked to form a module, and silver (Ag) internal electrodes are formed therein by co-firing.

The thin film according to another embodiment of the present invention may include the ZVMNYb-based varistor.

A method of manufacturing a ZVMNYb-based varistor according to another embodiment of the present invention is 1) zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ), niobium oxide (Nb ₂ O ₅ ), and oxidation Weighing ytterbium (Yhb ₂ 0 ₃ ); 2) mixing the weighed composition with acetone and ball milling to make a mixture; 3) drying the mixture; 4) preparing granular powder by granulating the dry mixture with a polyvinyl butyral binder; 5) pressing the granular powder and compressing it into a disk shape; 6) sintering after the compression step; 7) after the sintering step, cooling and molding; and 8) printing the silver paste on both sides of the molded pellet, and heating it.

Hereinafter, the present invention will be described in more detail.

The microstructure of zinc oxide varistor sintered using a metal oxide as an additive includes polycrystalline zinc oxide particles and a grain boundary phase between these particles. Zinc oxide varistor exhibits excellent voltage-dependent characteristics, and this phenomenon is called the varistor effect. That is, the grains of zinc oxide have very high electrical conductivity, while other oxides forming the grain interface have very high resistance. The electrical characteristics of metal oxide varistors can be expressed as numerous microvaristors connected in series or in parallel.

For example, increasing the thickness of the varistor increases the breakdown voltage. This is equivalent to a series of microvaristors.

In addition, if the area of the varistor is increased, the surge current withstand capacity is increased. This is equivalent to having microvaristors connected in parallel with each other.

Also, doubling the volume of the varistor almost doubles the energy capacity. This is because the number of zinc oxide particles that absorb energy doubles.

The distribution of the zinc oxide particle size in the microstructure is very important in determining the breakdown voltage voltage of the zinc oxide varistor. That is, the voltage of the varistor changes according to the series number of grain boundaries, and the surge resistance varies according to the parallel number of grain boundaries.

Zinc oxide varistor grain growth is affected by the starting material and sintering conditions. In the zinc oxide varistor to which the oxide additive is added, the liquid phase sintering mechanism is dominant rather than the solid phase sintering, so the content and distribution of the additive affects the particle size and distribution of the sintered body.

The present invention confirmed the dielectric properties in the microstructure, EJ and CV according to the doping _{of Yb 2} O _{3 in} the zinc oxide varistor, and is characterized in that it exhibits excellent non-ohmic properties.

More specifically, the ZVMNYb-based varistor of the present invention includes zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ) and niobium oxide (Nb ₂ O ₅ ), and ytterbium oxide (Yb). ₂ 0 ₃ ) may be further included.

As the varistor of the present invention additionally contains ytterbium oxide, it was confirmed that the microstructure was not significantly affected.

On the other hand, it was confirmed that the addition of ytterbium oxide significantly affected the electrical and dielectric properties of the varistor.

The varistor comprises (97.4-x) mol% ZnO, 0.5 mol% V ₂ O ₅ , 2.0 mol% MnO ₂ , 0.1 mol% Nb ₂ O ₅ and x mol% Yb ₂ O ₃ , wherein x is from 0.05 to 0.25.

As described above, it was confirmed that, by controlling the content range of ytterbium oxide, the microstructure was not affected, but the characteristics of the varistor, particularly the resistivity coefficient, were greatly affected.

More specifically, the varistor has a ceramic density (ρ) of 5.50 to 5.54 g/cm ³ , an average particle size of ZnO is 5.3 to 5.6 μm, and a diffraction angle (θ) of the XRD pattern is 25.39 to 33.93°.

The average particle size of ZnO was affected by the addition of ytterbium oxide, and the average particle size decreased until the addition of 0.05 to 0.1 mol%, but the average particle size increased when the addition amount was increased from 0.1 mol% to 0.25 mol%. did.

This is because, with the addition of ytterbium oxide, YbVO ₄ was formed, partially limiting the grain growth of ZnO, but conversely, as the added content increased, the effect of increasing the grain growth of ZnO was exhibited.

In addition, the ceramics density (ρ) increased with the addition of ytterbium oxide, which was due to the formation of _{YbVO 4 .}

The diffraction angle (θ) of the XRD pattern of the present invention is due to the formation of _{YbVO 4 as a secondary phase, and ranges from 25.39 to 33.93°.}

In addition, as the amount of ytterbium oxide was increased, _{the peak of YbVO 4} was found to increase.

As described above, when a small amount of ytterbium oxide is added, it is possible to provide a varistor with improved stability and reliability by exhibiting excellent nonlinearity without affecting the average particle size and switching voltage.

Basically, the potential barrier is affected by various defects at grain boundaries (addition defects such as interstitial zinc, interstitial oxygen, and zinc defects). Accordingly, it will be said that the nonlinear index a of the varistor is greatly affected by the Schottky barrier.

In the preparation of the varistor of the present invention, as a small amount of ytterbium oxide is added, YbVO ₄ is formed as a minor phase, and the content of this minor phase affects the nonlinearity index. That is, YbVO YbVO _{4 4} is absent or is more than possible to reduce the non-linear index a.

This means that when ytterbium oxide is added only within the content range of the present invention, a suitable minor phase, YbVO _{4 ,} is formed, and it will be possible to represent an optimal non-linear index value.

The varistor has a nonlinearity index (α) of 34.4 to 70.

Preferably, the varistor of the invention comprises (97.4-x) mol% ZnO, 0.5 mol% V ₂ O ₅ , 2.0 mol% MnO ₂ , 0.1 mol% Nb ₂ O ₅ and x mol% Yb ₂ O ₃ , The x may be 0.1.

As described above, when Yb ₂ O ₃ was 0.1 mol%, the non-ohmic coefficient (a) as a main parameter of the varistor exhibited a maximum value.

A large non-linearity index means that the resistance value is very high below the breakdown voltage voltage, but it shows a low resistance value above the breakdown voltage voltage. it means. By absorbing surge voltage, it is possible to protect electronic circuit components from surge and abnormal voltage.

The varistor of the present invention may have a potential barrier height (Φ _b ) of 0.76 to 1.25 Ev.

When the Yb ₂ O ₃ was included in 0.1 mol%, the potential barrier height (Φ _b ) and the surface state density (N _s ) also exhibited maximum values.

a, Φ _b and N _s showed the same trend of fluctuations. Consequently, the properties of EJ and CV are electrically closely related.

That is, the changes in the interface state density and dislocation barrier height according to the doping degree of ytterbium oxide coincide. It will be said that the higher the interface state density and the higher the dislocation barrier height, the better the nonlinear characteristic.

The electron density (N _d ) increases with _{the doping content of Yb 2} O _{3 .} That is, as the varistor contains ytterbium oxide, it acts as a donor based on a chemical-defect reaction, and the donor concentration is 2.46 × 10 ¹⁷ cm ^-3 to 7.41 × 10 ¹⁷ cm ^-3 , and a leakage current density (J _L ) of 56.8 to 262.2 μA/cm ² .

The _{increase in donor density due to the content of Yb 2} O ₃ is due to the generation of electrons due to partial substitution between Yb and Zn based on the following chemical defect reaction expression:

This means that Yb is added and acts as a donor, and it is assumed that the increase in leakage current due to the doping content of _{Yb 2} O _{3 is due to the increase in electron density.}

Consequently, an increase in the leakage current results in an increase in the dissipation factor (tana).

The tendency of the dielectric constant to change will correlate with the average ZnO grain size.

A method of manufacturing a ZVMNYb-based varistor according to another embodiment of the present invention is 1) zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ), niobium oxide (Nb ₂ O ₅ ), and oxidation Weighing ytterbium (Yhb ₂ 0 ₃ ); 2) mixing the weighed composition with acetone and ball milling to make a mixture; 3) drying the mixture; 4) preparing granular powder by granulating the dry mixture with a polyvinyl butyral binder; 5) pressing the granular powder and compressing it into a disk shape; 6) sintering after the compression step; 7) after the sintering step, cooling and molding; and 8) printing the silver paste on both sides of the molded pellet, and heating it.

More specifically, step 1) is to weigh the ingredients for preparing the ZVMNYb-based varistor of the present invention, and to prepare a composition within the scope of the present invention.

When the weighing of the components in step 1) is completed, the mixture is mixed with acetone and ball milled to prepare a mixture. Through ball milling, the ceramic raw material is pulverized into a fine powder and uniformly mixed.

에서 건조하였다. 건조한 혼합물은 폴리비닐부티랄 바인더로 과립화하여 과립 분말을 제조하였다.After preparing the mixture, 120

dried in The dry mixture was granulated with a polyvinyl butyral binder to prepare a granular powder.

The granular powder was compressed into a disk shape by pressing and sintered.

Thereafter, silver electrodes are coated on both sides of the sintered body, lead wires are soldered, and then packaged to manufacture a ZVMNYb-based varistor.

According to the ZVMNYb-based varistor of the present invention and its manufacturing method, it exhibits a very high resistance value below the breakdown voltage voltage, but has excellent nonlinear characteristics showing a low resistance value above the breakdown voltage, and has a high interfacial state density and potential barrier height. This results in improved stability and reliability.

In addition, it may act as a donor based on a chemical defect reaction.

The present invention may provide a chip varistor using the ZVMNYb-based varistor.

1 is an SEM photograph of a varistor according to an embodiment of the present invention.
2 is a measurement result regarding the average particle size and sintering density of the varistor according to an embodiment of the present invention.
3 is an XRD pattern measurement result according to the content of Yb2O3 according to an embodiment of the present invention.
4 is a measurement result of EJ characteristics of a varistor according to an embodiment of the present invention.
5 is a measurement result of a nonlinear coefficient and a leakage current density of a varistor according to an embodiment of the present invention.
6 is a CV characteristic measurement result of a varistor according to an embodiment of the present invention.
7 is a dielectric characteristic result of a varistor according to an embodiment of the present invention.
8 is a result of dielectric constant and loss coefficient of a varistor according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

Manufacture of ZVMNYb-based varistor

Zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ), niobium oxide (Nb ₂ O ₅ ) and ytterbium oxide (Yb ₂ O ₃ ) were weighed.

The weighed raw powder was ball milled with acetone for 24 hours to produce a mixture, and the mixture was dried at 120°C. The dry mixture was granulated with a polyvinyl butyral (PVB) binder to prepare a granular powder.

A pressure of 100 MPa was applied to the granular powder and compressed into a disk having a diameter of 10 mm and a thickness of 1.5 mm.

로 3 시간 동안 소결하였다. 이후, 4 ℃/분의 속도로 온도를 낮춰주며 냉각하였다.After compression to disk form, 900 in a magnesia plate

was sintered for 3 hours. Thereafter, the temperature was lowered at a rate of 4 °C/min and cooled.

The disk pellets were sintered at 900 °C for 3 h, then cooled at 4 °C/min.

It was lapped and polished so that the final disk shape was 8 mm in diameter and 1.0 mm in thickness. An adhesive was applied to one surface of the conductive silver, and after bonding to the surface of the disk, it was heated at 550° C. for 10 minutes.

The raw material powder is (97.4-x) mol% ZnO, 0.5 mol% V ₂ O ₅ , 2.0 mol% MnO ₂ , 0.1 mol% Nb ₂ O ₅ , x% Yb ₂ O ₃ , where x is 0.0, 0.05, 0.1 and 0.25 mol.

Analysis method

(1) Microstructure analysis

For microstructure analysis, samples were wrapped and polished using _{SiC paper and Al 2} O ₃ powder and then chemically etched using _{HClO 4} -H _{2 O solution.}

The surface was analyzed using a field emission scanning electron microscope (FE-SEM Model Quanta 200, Czech). The average particle size (d) was analyzed by the linear intercept method.

The resulting ceramic phase was analyzed by X-ray diffraction (XRD Model X'pert-PRO MPD) using CuKa radiation.

The ceramic density (α) was measured using a density measurement kit (238490).

(2) Measurement of electrical and dielectric properties

The V-I measurement of the varistor was performed using a high-voltage source measurement unit (Model Keithley 237, USA).

The switching voltage (V _{1 mA} ) was measured at a current density of 1.0 mA/cm ² , and the leakage current density (J _L ) was measured at _{0.80 V 1 mA.}

In addition, the resistivity coefficient (a) was calculated by the following formula:

a = 1/(logV ₂ -logV ₁ )

Here, V1 is a switching voltage corresponding to ^{1.0mA/cm 2} and V2 is 10mA/cm ^{2 .}

CV measurement of the varistor was measured using an LCR meter (Model QuadTech 7600, USA) and an electrometer (Model Keithley 617, USA). Donor density (N _d ), dislocation barrier height (Φ _b ), and interfacial state density (N _s ) were determined using the method presented in M. Mukae et al.

The f-CAPP' relationship and dielectric coefficient (tanδ) were measured with an LCR meter (Model QuadTech 7600, USA).

Analysis

(1) Varistor microstructure analysis result

The SEM image of the varistor according to the added content of Yb ₂ O _{3 is shown in FIG. 1 .} According to FIG. 1 ㅐ, the microstructure of a typical varistor is shown regardless of the content of _{Yb 2} O _{3 .}

The changes in the average ZnO particle size and ceramics density (ρ) according to the content of Yb ₂ O _{3 are shown in FIG. 2 .}

When _{the content of Yb 2} O ₃ was added to 0 to 0.1 mol%, the average ZnO particle size decreased from 5.5 to 5.3 μm, but then, when Yb ₂ O ₃ was further added to 0.25 mol%, it increased to 5.6 μm. did.

According to FIG. 3 , the YbVO ₄ phase generally limits the growth of other grains, but if the YbVO ₄ phase is formed too much, it may promote the growth of other grains.

On the other hand, the ceramics density (ρ) was increased to ^{5.50 to 5.54 g/cm 3 .}

In accordance with the addition of Yb ₂ O _3, it is that the ceramic density is increased, because the addition of Yb ₂ O _3, to increase the content of YbVO _4.

(2) XRD pattern analysis, electrical and dielectric properties measurement results

The XRD profile of the varistor with respect to the content of Yb ₂ O _{3 is shown in FIG. 3 .}

The XRD pattern shows that ZnO particles appear as a major phase, and minor phases such as _{Zn 3} (VO ₄ ) ₂ , ZnV ₂ O ₄ and VO _{2 exist.}

In addition, the presence _{of YbVO 4} as a secondary phase was indicated by showing diffraction peaks at diffraction angles θ = 25.39 and 33.93 of the varistor containing _{Yb 2} O _{3 .} As the content of Yb ₂ O ₃ increased, the peak of _{YbVO 4 gradually increased.}

YbVO ₄ phase can significantly affect V-1 properties as shown in Table 1. The estimated microstructure characteristic parameters are shown in Table 1.

Yb ₂ O ₃ content
(mol%) d
(μm) ρ
(g/cm ³ ) V _{1 mA}
(V/cm) v _gb
(V/gb) a J _L
(μA/cm ² ) 0.0 5.5 5.50 4874 2.7 51.0 56.8 0.05 5.4 5.51 5145 2.8 61.3 60.6 0.1 5.3 5.52 5494 2.9 70.0 84.1 0.25 5.6 5.54 4574 2.6 34.4 262.2

The VI characteristic (EJ) of the varistor according to the added content of Yb ₂ O _{3 is shown in FIG. 4 .}

Varistor has the function of blocking or passing current through resistivity or resistance. Current blocking is performed in the pre-breakdown region and current passing is performed in the breakdown region.

As can be seen from the curve shape of FIG. 4 , _{the doping of Yb 2} O ₃ greatly affects the non-ohmic characteristics of the varistor.

When _{the doping content of Yb 2} O ₃ is less than 0.1 mol%, the switching voltage (V _{1 mA} ) increases from 4874 to 5494 V/cm, whereas when 0.25 mol% is added, the V _{1 mA} value increases up to 4574 V/cm decreased.

The fluctuation trend of the V _{1 mA-} value depends on the first particle size of the single particle boundary and the second switching voltage (vgb).

Consequently, _{it can be said that the V 1 mA} value is more affected by the microstructure.

The variation trend of the resistivity coefficient according to the content of Yb ₂ O ₃ and the leakage current density of the varistor are shown in FIG. 5 .

The _{a-value significantly increased from 51 to 70 until the doping content of Yb 2} O ₃ reached 0.1 mol %, while the a-value decreased to 34.4 when 0.25 mol % was added. The above result means that _{the doping of Yb 2} O ₃ clearly affects the non-ohmic properties.

The varistor to which Yb ₂ O ₃ was added at 0.1 mol% showed the highest a value (70) compared to the conventional ZnO-V ₂ O _{5 based varistor.}

As a result, it can be said that superior resistivity can be obtained from ZVMN-Yb ₂ O _{3 varistors compared to ZnO-V 2} O _{5 based varistors.}

Yb ₂ O ₃ 0.25 The reason that the varistor is added to represent the mol% exhibit lower than Yb ₂ O ₃ -free is the result of the formation of the over-YbVO ₄ As mentioned in the XRD analysis.

_{The YbVO 4} phase produced in excess as above has a significant impact on the potential barrier height at grain boundaries.

As a result, the potential barrier height decreases and the α-value decreases.

On the other hand, as _{the added content of Yb 2} O ₃ increased, the leakage current density (J _L ) increased from 56.8 to 262.2 μA/cm ^{2 .}

Overall, the resistivity coefficient was high, but the leakage current of the sample was measured to be high. The leakage current is related to the pre-breakdown region of three regions: a pre-breaking region (ohmic), a breakdown region (non-ohmic), and a rising region (ohmic).

The high leakage current in the pre-breakdown region is due to recombination between holes and electrons at grain boundaries. In addition, the J _L- value is independent of the electron density, and the estimated EJ characteristic parameters are shown in Table 1 above.

The CV characteristics of the samples for various doping contents of Yb ₂ O _{3 are shown in FIG. 6 .} Table 2 shows the _{CV characteristic parameters (N s} ) such as grain boundary density (N _d ), dislocation barrier height (Φ _b ), and density of interfacial states at grain boundary interfaces.

Yb ₂ O ₃ content
(mol%) N _d
(10 ¹⁷ cm ^-3 ) Φ _b
(eV) N _s
(10 ¹² cm ^-2 ) e _APP'
(1 kHz) tanδ
(1 kHz) 0.0 2.46 1.01 1.53 592.7 0.209 0.05 4.09 1.09 2.05 536.0 0.210 0.1 5.75 1.25 2.60 501.4 0.221 0.25 7.41 0.76 2.30 715.9 0.268

The N _d- value increased from 2.46 × 10 ¹⁷ to 7.41 × 10 ¹⁷ cm ^-3 as the content of Yb ₂ O ₃ increased.

The potential barrier height (Φ _b ) formed at the grain boundary increased from 1.01 to 1.25 eV until the content of Yb ₂ O ₃ reached 0.1 mol %, whereas when 0.25 mol % was added, the Φ _b value slightly decreased to 0.76 eV did.

The fluctuation trend _{of the N s-} value according to the content of Yb ₂ O ₃ is similar to that _{of the Φ b-value.} a, Φ _b and N _s showed the same trend of fluctuations. Consequently, the EJ and CV characteristics are electrically correlated.

The dielectric properties of the varistor according to the content of Yb ₂ O _{3 are shown in FIG. 7 .}

Overall, the dielectric constant εAPP' did not decrease monotonically with increasing frequency, but decreased. The above result is directly related to the rotation of the electric dipole, which induces the interfacial polarization and the frequency-dependent oriental polarization.

A variation trend of the dielectric constant εAPP' (1 kHz) according to the content of Yb ₂ O _{3 is shown in FIG. 8 .}

The dielectric constant εAPP' (1 kHz) decreased from 592.7 to 501.4 until the content of _{Yb 2} O _{3 reached 0.1 mol%.} On the other hand, when 0.25 mol% was added, εAPP' was reduced to 715.9. According to _{the content of Yb 2} O ₃ , the behavior of the dielectric constant εAPP' is affected by the behavior of the average ZnO grain size in the microstructure, but the EJ characteristic showed a trend opposite to the switching voltage. Consequently, it will be said that the dielectric properties are influenced by the microstructure.

On the other hand, the loss factor (tanδ) showed similar and unique curves for all varistors with increasing frequency. That is, all varistors exhibited valley *?* points and peak points as the frequency increased.

In general, the above phenomenon can be easily confirmed in the varistor.

The valley point shows the minimum dielectric loss and the εAPP'- value is constant. On the other hand, the peak-point, that is, the absorption peak, shows a loss peak, and the εAPP'- value shows a sharp decrease.

The behavior of the loss coefficient (tanδ, 1 kHz) according to the content of Yb ₂ O _{3 is shown in FIG. 8 .}

The tanδ value increased from 0.209 to 0.268 according to the content _{of Yb 2} O _{3 .} The fluctuation trend of the tanδ- value according to the content of Yb ₂ O ₃ is similar to that _{of the J L-} value and the N _{d- value.}

In view of the fluctuation trends of tanδ, J _{L and Nd, J L-} value is _{affected by N d-} value and tanδ is affected by _{J L-value.}

It will be said that the ZVMN-Yb ₂ O ₃ varistor according to the present invention has electrically and genetically related properties based on the relevant data.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

Claims (12)

including zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ) and niobium oxide (Nb ₂ O ₅ ),
It is a varistor further comprising ytterbium oxide (Yb ₂ 0 _{3 ),}
In the varistor, the average particle size of ZnO is 5.3 to 5.6 μm,
Acts as a donor based on a chemical-defect reaction, with a donor concentration of 2.46 Х 10 ¹⁷ cm ^-3 to 7.41 Х 10 ¹⁷ cm ^-3
ZVMNYb Varistor. According to claim 1,
the varistor comprises (97.4-x) mol% ZnO, 0.5 mol% V ₂ O ₅ , 2.0 mol% MnO ₂ , 0.1 mol% Nb ₂ O ₅ and x mol% Yb ₂ O ₃ ,
wherein x is 0.05 to 0.25
ZVMNYb Varistor. According to claim 1,
The varistor has a ceramics density (ρ) of 5.50 to 5.54 g/cm ³
ZVMNYb Varistor. delete According to claim 1,
The varistor has a diffraction angle (θ) of 25.39 to 33.93° of the XRD pattern.
ZVMNYb Varistor. According to claim 1,
The varistor has a nonlinear index (α) of 34.4 to 70
ZVMNYb Varistor. According to claim 1,
The varistor has a leakage current density (J _L ) of 56.8 to 262.2 μA/cm ²
ZVMNYb Varistor. delete According to claim 1,
The varistor has a potential barrier height (Φ _b ) of 0.76 to 1.25 Ev
ZVMNYb Varistor. delete A ZVMNYb-based varistor according to claim 1
pellicle. 1) Weighing zinc oxide (ZnO), vanadium oxide (V ₂ O ₅ ), manganese oxide (MnO ₂ ), niobium oxide (Nb ₂ O ₅ ) and ytterbium oxide (Yb ₂ 0 ₃ );
2) mixing the weighed composition with acetone and ball milling to make a mixture;
3) drying the mixture;
4) preparing granular powder by granulating the dry mixture with a polyvinyl butyral binder;
5) pressing the granular powder and compressing it into a disk shape;
6) sintering after the compression step;
7) after the sintering step, cooling and molding; and
8) printing a silver paste on both sides of the molded pellet, and heating
A method for manufacturing a ZVMNYb-based varistor.

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