JPS6046006A - Voltage nonlinear resistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Part W3 to which the invention pertains] The present invention relates to a voltage non-linear resistor, and more particularly to a voltage non-linear resistor containing zinc oxide (ZnO) as a main component and used as an overvoltage protection element. .

[Prior art and its drawbacks]

Conventionally, varistors containing silicon carbide (SiC), selenium (Se), silicon (Sl), or Zoo as main components have been used for the purpose of overvoltage protection of electronic and electrical equipment. Among them, a varistor containing ZnO as a main component generally has characteristics such as a low limiting voltage and a large voltage nonlinear coefficient. For this reason, it is suitable for protecting against overvoltage in equipment made of semiconductor elements with low overcurrent resistance, and has come to be widely used in place of varistors made of SIC.

Also, ZnO is the main component, and rare earth elements, cobalt (CO) and magnesium (Mg) are subcomponents.

At least one of calcium (Ca), potassium (K), cesium (Cs), and rubidium (Rb)
It is known that a voltage nonlinear resistor manufactured by adding at least one of these and chromium (Cr) in the form of an element or a compound and firing it has excellent voltage nonlinearity.

However, this voltage nonlinear resistor has a limiting voltage ratio characteristic (the voltage between the electrodes when a current of 1 m is passed through the voltage nonlinear resistor V = 8, and the interelectrode voltage Vx when a current of X^ is passed through the voltage nonlinear resistor) The ability to improve the ratio (vx8/V, v%) and the charging life characteristics at the same time was the key to improvement.

Conventionally, in order to improve the charging life characteristics, for example, a method has been adopted in which the amount of a specific additive component is increased or decreased. However, a voltage nonlinear resistor whose composition is changed to improve the energized life characteristic has a drawback that the limiting voltage ratio characteristic is deteriorated.

[Object of the Invention] An object of the present invention is to provide a voltage nonlinear resistor that has improved energization life characteristics while maintaining excellent limiting voltage ratio characteristics.

[Summary of the Invention] Here, the present inventor has discovered that 2r+O is the main component, and as subcomponents, in addition to rare earth elements and Co, at least one of L Ca, at least one of K, Cs, and Rh, and Cr. By further adding tellurium (Te) as a subcomponent to the conventional voltage nonlinear resistor, the energization life characteristics are improved while maintaining the excellent limiting voltage ratio characteristics. It was discovered that a voltage nonlinear resistor with good nonlinear characteristics could be obtained, and the present invention was completed.

According to the present invention, however, the voltage non-conductor contains ZnO as a main component, and contains at least one of Mg and Ca in addition to rare earth elements and Co, at least one of K, Cs, and Rh, and Cr as subcomponents. A voltage non-linear resistor is provided which is characterized in that Te is further added as a subcomponent in the linear resistor.The voltage non-linear resistor according to the present invention generally contains a mixture of metals or compounds as an additive component. Manufactured by firing and sintering at high temperatures in an oxygen-containing atmosphere.

The additive components are usually added in the form of metal oxides, but compounds that can become oxides during the firing process, such as carbonates, hydroxides, fluorides, etc., can also be used, or they can be used in the form of single elements and fired.・Can also be converted into oxide during the formation process.

According to a particularly preferred method, the voltage nonlinear resistor of the present invention is prepared by thoroughly mixing ZnO powder and additive metal or compound powder thereof, and calcining the mixture in air at 500 to 1000° C. for several hours before firing. It is manufactured by thoroughly crushing the calcined material, molding it into a predetermined shape, and then firing it in air at a temperature of about 1100 to 1450° C. for several hours. 1100℃
At lower firing temperatures, sintering is insufficient and the properties are unstable. Moreover, at temperatures higher than 1450 t, it becomes difficult to obtain a homogeneous sintered body, nonlinearity decreases, and there are difficulties in reproducibility such as control of characteristics, making it difficult to obtain a product for practical use.

[Embodiments of the invention] Examples are now presented to further illustrate the invention.

Urashiki Takumi ZnO powder Ni Pr60. , CO3%+, CO3+Cr
1.03. MgO, CaO, and TeO powders were added in amounts corresponding to the predetermined atomic percent listed in Table 1, mixed thoroughly, and then calcined at 500 to 1000°C for several hours.Then, the calcined product was thoroughly pulverized. A sintered body was obtained by molding into a 17-diameter steel disc using a mold and firing in air at 1100 to 1450°C for 1 hour. The sintered body thus obtained was polished into a sample with a thickness of 2 cm, and electrodes were baked on both sides of the sample to form a device, and its electrical characteristics were measured.

As for electrical characteristics, when a current of 1 mA is passed through the device at 25°C, the inter-electrode voltage vlyA, 1 mA to 10 o
Nonlinear coefficient α at +^, interelectrode voltage ■ when a 40A 8×20μs wave current flows. The limiting voltage ratio characteristic '40A/''+, A was determined from 8 and V, , Iv, and 8.

In addition, as a charging life characteristic, the change in inter-electrode voltage 'I/JA when a constant DC voltage corresponding to 100% of vlsA was applied for 500 hours and a current of 1 μA was passed before and after was measured. The nonlinear coefficient α is obtained by approximating the change in the current I of the element with respect to the voltage ■ by the following equation.

1-(V/C)'' Here, C is the voltage per element when the current density is 1+wA/c+a.

Table 1 shows the measurement results of electrical characteristics when the composition of the voltage nonlinear resistor was varied. The blended compositions shown in the table are expressed in atomic % calculated from the ratio of the number of atoms of the added element to the total number of atoms of each component metal element in the blended raw materials.

Table 1 Sample 1 shown in Table 1 contains Pr+ CO+ K in Zoo.
It corresponds to a conventional voltage nonlinear resistor manufactured by adding only +Cr and Mg, and its limiting voltage ratio characteristic is 1.45, the applied voltage life characteristic is -32.7%, and the nonlinear coefficient α is 41. 0 A sample that has good applied voltage life characteristics while maintaining excellent limiting voltage ratio characteristics, which is the object of the present invention, that is, the rate of change in V is closer to 0% than -32.7% is In table 1, magnetic 3 to lice 6. Arashi 9-Magnetic 12.翫15〜l1h18
．． N121-Nh23. Na28 to Na29 and positive 32 to 11h36. Accordingly, Pr is 0.08~
5.0 atom%, C.

is 0.1 to 10.0 at%, Plg is 0.01 to 5.0
atomic%, K is 0.01 to 1.0 atomic%, Cr is 0.01
- 1.0 at%, Te needs to be added in the range of 0.001 to 0.5 at%.0 or more As is clear from Table 1, subcomponents include Pr, Co, K, Cr+ M
By further adding Te to the system containing g, the applied voltage life characteristics are significantly improved while maintaining the excellent limiting voltage ratio characteristics.

This is ZnO with Pr, Cot K+ Cr+ ML
This can only be achieved when Te coexists. If these subcomponents are added alone, the voltage nonlinearity is extremely poor and only half-ohmic characteristics are obtained, making it impossible to put them into practical use.

In Table 1, only Pr is illustrated as a rare earth element. Table 2 shows the effects of adding Te on rare earth elements other than Pr or on systems using two or more rare earth elements.Even for rare earth elements other than ePr,
The applied voltage life characteristics are significantly improved while maintaining excellent nonlinearity and 11-limit voltage ratio characteristics.

Table 3 shows the characteristics of the nonlinear resistor produced by adding Ca4-instead of Mg.

Table 4 shows the characteristics of the nonlinear resistor when Rh and Cs are added to Mg, Ca, and Mg.

In either case, the effect of adding Te is that the applied voltage life characteristics are significantly improved while maintaining the excellent nonlinearity and limiting voltage ratio characteristics as in the cases of Mg alone and Mg alone. It is in. In this case as well, the rare earth element is 0.08~
5.0 at%, Co 0.1 to 10.0 at%, ML
At least one type of Ca is 0.01 to 5.0 at%,
At least one of K, C5Jb is o, ot in total amount
~i, o atom%, Cr is 0.01 to 1.0 atom%, Te
needs to be added in a range of 0.001 to 0.5 at%.

In these cases, ZnO contains rare earth elements, Co and Mg,
This is achieved only when at least one of Ca, at least one of K, Cs, and Rh, Cr, and Te coexist; if these subcomponents are added alone, voltage nonlinearity will be extremely poor, and Only oh-mink characteristics can be obtained, and it cannot be put to practical use.

[Effects of the Invention] As described above, the voltage nonlinear resistor of the present invention has significantly improved applied voltage life characteristics while maintaining good nonlinearity and limiting voltage ratio characteristics, and therefore has a voltage nonlinear resistor of the present invention that has a significantly improved applied voltage life characteristic.

Claims (1)

[Claims] Zinc oxide is the main component, and as subcomponents at least one rare earth element is added in a total amount of 0.08 to 5.0 atomic%, cobalt is 0.1 to 10.0 atomic%, and at least one of magnesium and calcium is added. 0.01-5.0 at%
, potassium, cesium, and rubidium in a total amount of 0.01 to 1.0 at%, and chromium in a total amount of 0.01 to 1.0 at%.
O2N2.0 atomic%, TeJL/)Lt from 0.001 to
A voltage nonlinear resistor characterized in that it is made by adding and firing the additive in a range of 0.5 at%.