KR970003330B1 - Ceramics resistor composition & marking method thereof - Google Patents

Abstract

Disclosed are the composition for ceramic resistor and method of fabricating the same which can be sintered in the air and lower the temperature of the combination. The composition is made of V2O5, V2O3, Cr2O3 and vanadium metal. The V2O5, V2O3 and vanadium metal are in the ranges of 26% to 31% by weight, 28% to 54% by weight and 40% to 44% by weight, respectively, and the Cr2O3 is contained 1.5% by weight. The composition is obtained by (a) mixing and grinding the above components using a known method, (b) annealing the components for 2 hours at a temperature of 1000deg. C in the air, (c) grinding the material obtained by the step (b) using the method, and then adding a organic binding material to the grinded material and (d) sintering the material obtained by the step (c) in the air. Thereby, it is possible to obtain the composition in the air and lower the temperature thereof.

Description

V2O3-based ceramic resistor composition and its manufacturing method

1 is a schematic process diagram for producing a composition of the present invention.

2 is a change in electrical resistance with temperature of single crystal VO ₂ .

3 is a change in electrical resistance according to the temperature of Example 3 of the present invention added Cr ₂ O ₃ .

The present invention relates to a composition for a V ₂ O ₃ -based ceramic resistor to which a vanadium metal having a constant resistance temperature coefficient is added, and a method for producing the resistor.

Conventional thermistor material with a constant resistance coefficient was barium titanate as a main component, but this material cannot be manufactured with a resistance value of 10Ω · cm or less at room temperature, so that it has a lower electrical resistance and a relatively high limit current density. A material of ₂ O ₃ thermistors has been developed.

Pure vanadium oxide has various electrical properties according to the valence state and crystal phase of vanadium ions. The electrical conductivity has discontinuity with temperature at 66 ℃, the crystal structure transition temperature of vanadium ions. That is, the electrical resistance decreases rapidly at the transition temperature, so that the semiconductor resistance change has a metal-like characteristic, which is shown in FIG. 2.

By using this phenomenon, vanadium oxide is applied to thermistors, switch elements, heat sources, and thin film devices. On the other hand, when a small amount of Cr, Al, Sc, etc. is added to the vanadium oxide V ₂ O ₃ , a phenomenon in which the electrical resistance increases rapidly is found to be contrary to the above case. Efforts to apply are racing.

However, the synthesis of vanadium oxide is achieved by heat treatment at about 1000 ° C. for a long time. In this case, the vanadium oxide should be formed under a hydrogen atmosphere, which is a powerful reducing atmosphere to prevent oxidation of V ₂ O ₃ . In addition, the material must be sintered in a reducing atmosphere at a high temperature of 1500 ° C. or higher to develop properties of the material.

Therefore, the complexity of the manufacturing process and the risk of explosion and fire are always included, and due to the high sintering temperature of V ₂ O ₃ , the manufacturing cost is high, thus laying a wall for practical use.

Accordingly, the present invention provides a composition for a V ₂ O ₃ -based ceramic resistor that can be sintered in the air and lower the sintering temperature by adding a vanadium metal to the vanadium oxide in order to solve the above demands and problems. There is a purpose.

In addition, the present invention relates to a method for producing a ceramic resistor using the composition.

The present invention to attain the object is a V ₂ O ₅ 26~31 wt%, V ₂ O ₃ 28~54% by weight, Cr ₂ O ₃ 1.5 wt% of V ₂ O ₃ system consisting of vanadium metal 40-44% by weight A composition for ceramic resistors.

It is a method of inhibiting oxidation of vanadium to produce a device having a constant resistance temperature coefficient while maintaining the valence of vanadium ions having various valence states at +3, and instead of heat-treating under a dangerous hydrogen atmosphere, V, a conventional starting material. By substituting part of ₂ O ₅ or V ₂ O ₃ with vanadium metal, even if sintered in air, the vanadium metal reacts with oxygen in the air to have the properties of the constant resistance coefficient in the same manner as the heat treatment effect in the reducing atmosphere. The chemical reaction expected at this time is as follows.

In addition, by adding a vanadium metal having a melting temperature of 270 ° C. lower than that of the melting temperature of V ₂ O ₃ , it is possible to lower the sintering temperature as well as the Cr, Al, Sc, etc. Increasing the diffusion rate for mass transfer makes the distribution of additives uniform.

The present invention is V ₂ O ₅ 26~31% by weight, V ₂ O ₃ 28~54% by weight, Cr ₂ O ₃ and 1.5% by weight vanadium metal V ₂ O 40~44% by weight, consisting of _three series resistors cell hamik As shown in FIG. 1, the composition for (a) is mixed and pulverized in the above composition ratio using a known method, (b) heat treated at 1000 ° C. for 2 hours in air, and (c) a known method. It is characterized in that it is composed of a step of pulverizing, adding and molding the organic binder, and (d) sintering in air at 1350 ℃ to 1450 ℃ for 2 to 10 hours.

In the case of 1300 ° C and 10 hours, the ceramic is not sufficiently sintered, so that the mechanical strength is not only weak, and the properties of the positive resistance are not shown. Also, in the case of 1500 ° C and 2 hours, the amount of liquid sand is increased due to melting due to high temperature. It is difficult to maintain the shape. As a result, the optimum sintering conditions were sintering temperature of 1350 ℃ to 1450 ℃, holding time of 4 hours was appropriate.

As described above, the present invention can heat-treat in the air instead of the conventional reducing atmosphere (hydrogen atmosphere), thus simplifying the manufacturing equipment, thereby lowering manufacturing costs, and releasing the risk of other explosions and fires in the use of hydrogen. In addition, by applying the melting of the metal it can be lowered by more than 100 ℃ than the existing heat treatment temperature significantly contributes to the reduction of manufacturing cost.

Hereinafter, the production method of the present invention and its effects through the examples will be described in detail. However, the following examples do not limit the scope of the invention.

Example 1

15.25 g, 14 g, 20 g and 0.75 g of commercially available reagent grade V ₂ O ₅ , V ₂ O ₃ , V and Cr ₂ O ₃ are chilled and mixed and ground under a wet ball for 20 hours. At this time, the average particle size of the powder obtained after pulverization is 0.5㎛, heat treatment at 1000 ℃ in air for 2 hours to produce V ₂ O ₃ and oxidize part of the vanadium metal to induce the formation of V ₂ O ₃ and at the same time Cr ions Substitution at the vanadium metal position provided a constant temperature coefficient. The sample obtained is regrind under a wet ball for 20 hours, dried, and 5% polyvinyl alcohol (PVA), which is an organic binder, is added to the sample in a weight ratio of 5% and mixed. The mixed powder was pressed at 500 kg / cm 3 and then sintered in air at 1400 ° C. for 4 hours.

After polishing the surface of the sintered specimens, the electrode was coated with nickel electroless plating, and various properties were measured using a conventional method, and the results are shown in Table 1 below.

[Examples 2 and 3]

To the composition of Table 1, and prepared in the same manner as in Example 1, the characteristics thereof are shown in Table 1 below. In addition, FIG. ₃ shows the change in the resistance of the jerk according to the temperature of Example 3 in which Cr ₂ O ₃ was added.

[Examples 4 and 5]

Instead of using V ₂ O ₅ as a starting material, only V ₂ O ₃ , V, and Cr ₂ O ₃ were used, and the same ratio as in Examples 4 and 5 of Table 1 was prepared in the same manufacturing process as in Example 1.

The results are shown in Table 1, and the characteristics thereof are shown in Table 1 below. As shown in Table 1, the room temperature resistance value decreased from 0.027 to 0.0015 (ohmcm) as the amount of vanadium metal was 42% by weight and 44% by weight in Examples 2 and 3, respectively. The effect increased from 80 to 91. However, when the amount of vanadium metal is 46% by weight or more, it is difficult to maintain the shape as the amount of molten vanadium metal increases, making it difficult to measure electrical properties. In Examples 4 and 5, the room temperature resistance value was lower than that of Examples 1 and 2, but the resistance increase effect was small. In addition, when the vanadium metal is more than the composition of Examples 4 and 5, it is difficult to maintain the shape of the molded specimen due to the melting of the vanadium metal.

[Table 1] Composition and Properties

* Increased resistance = Maximum resistance ÷ Resistance at room temperature (25 ℃)

Claims (2)

V ₂ O ₅ 26~31% by weight, V ₂ O ₃ 28~54% by weight, Cr ₂ O ₃ 1.5 for V ₂ O ₃ based ceramic resistor, characterized in that consisting of% by weight vanadium metal and 40-44 percent by weight Composition. A composition for a V ₂ O ₃ ceramic resistor composed of _{26 to} 31 weight% of V ₂ O _5, 28 to 54 weight% of V ₂ O ₃ , 1.5 weight% of Cr ₂ O ₃ , and 40 to 44 weight% of vanadium metal is known (a). The mixture was mixed and pulverized at the above composition ratio using the method of (b) and heat-treated at 1000 ° C. for 2 hours in the air, (c) regrind and the organic binder was added and molded by a known method, and (d) 1350-1. A method for producing a V ₂ O ₃ based ceramic resistor characterized by sintering at 1450 ° C. for 2 to 10 hours in air.

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