KR970006621B1 - Method of manufacturing semiconductor magnetic compound of bati03 systems - Google Patents

Abstract

A fabrication method of BaTiO3 semiconductor magnetic composite using a powder by coprecipitation method of chloride is disclosed. The method comprises the steps of: deformation processing a powder of BaTiO3 semiconductor magnetic composite by coprecipitation method at the temperature of 1200-1250 deg. C , for the time of 0.5-1 hours; and cooling the powder by the temperature of 800 deg. C , in 1 deg. C - 3 deg. C per minute. Thereby, it is possible to easily form the BaTiO3 semiconductor magnetic composite having high quality.

Description

Method for manufacturing barium titanate-based semiconductor magnetic composition

1 is a temperature change in the firing process of the present invention.

* Explanation of symbols for main parts of the drawings

1: Temperature rising process 2: Maximum temperature keeping process

3,5 cooling process 4: cooling increase process

The present invention relates to a method for producing a barium titanate-based semiconductor magnetic composition.

Conventionally, when a small amount of rare earth element of BATiO ₃ or its solid solution is added and calcined, a semiconductor magnetic composition having a positive resistance temperature coefficient can be obtained.

When such a static thermistor is used as the current limiting device, it is desired that the resistance temperature coefficient is large, the resistance increase gradient is steep, the room temperature specific resistance is small, and the voltage dependency is small.

It is already known to significantly improve the resistance temperature coefficient by adding Mn oxide to barium titanate-based thermistor materials.

It is also common to add Al ₂ O ₃ , SiO ₂ , TiO ₂ , Li ₂ CO _3, etc. in order to precipitate Mn in the grain boundary layer and to lower the resistance value and improve the resistance value increasing characteristics.

In addition, the larger the particle size of the sintered body, the smaller the resistance value, but the greater the voltage dependence, so that the grain boundary growth can be suppressed by adding CaCO ₃ , Sb ₂ O _3, or the like to lower the voltage dependency.

Therefore, by combining the above components properly, it is possible to produce a current limiting device of excellent characteristics. However, all of the above components are solid oxides, and since the added elements are very small, the mixture should be mixed for a long time of 20 hours or more for uniform mixing, and there is a problem such as mixing of impurities in mixing, and the firing temperature is 1300 to 1400 ° C. Required at high temperatures.

In order to improve in this regard, a method of producing barium titanate, which uses a solid chloride rather than a solid oxide as a starting material and can produce static semiconductor magnets with a short mixing time and a low firing temperature, has been proposed. In this method, there is no mention of the firing temperature for obtaining high-performance static semiconductor magnetism.

Therefore, the present invention can manufacture a high-performance current limiting static thermistor by changing the maximum holding temperature and cooling conditions during the firing process using a powder made by using the chloride as described above to manufacture a high-performance static semiconductor magnetic. It is an object to provide a method.

In order to achieve the above object, the production method of the present invention is a method for producing a barium titanate-based semiconductor magnetic composition using powder by the coprecipitation method of chloride, wherein the maximum holding temperature is 1200 ° C to 1250 ° C and the holding time is 0.5 to It is set as 1 hour, and it is hold | maintained for 1-2 hours in the temperature range of 1050 degreeC-1150 degreeC, cooling to 800 degreeC at 1 degreeC-3 degreeC / min in a cooling stage.

Hereinafter, a method of manufacturing the barium titanate-based semiconductor magnetic composition of the present invention will be described in detail.

96 mol of barium chloride (BaCl ₂ ), 101 mol of carbon tetrachloride (TiCl ₄ ), CaCl ₂ 4 mol, YCl ₃ 0.11 mol, AlCl ₃ 0.2 mol, SiCl ₄ 0.5 mol, LiCl 0.2 mol, SbOCl 0.06 mol, MnCl ₂ 0.08 mol at room temperature After mixing for 30 minutes, 2.0 to 3.0 mol of a small amount of C ₂ H ₂ O ₄ 2H ₂ O solution was added as a coprecipitation agent to prepare a mixed barium titanyl oxalate as an intermediate, and the resulting intermediate was stirred at room temperature for 30 minutes to 1 hour. After the reaction, the result was vacuum filtered, and the excess hydroxyl ions and residual chlorine (Cl) ions were removed by washing with water about 3 to 5 times, dried at about 100 ° C. in a drier for 4 hours, and then heated at a temperature rising rate of 4 ° C./min. Into an alumina crucible in an electric furnace, the temperature was raised to 800 ° C. and maintained for 1 hour, followed by quenching.

After putting vinyl alcohol as a binder into the mixed barium titanate powder obtained in the above process, wet mixing was carried out through a polyethylene-coated ball mill and media, and then assembled and molded by applying a pressure of 1000 kg / ㎠ in a disk shape having a diameter of 24 mm and a thickness of 3 mm. It bakes for 0.5 to 1 hour at 1200-1250 degreeC.

At this time, the present invention is configured to maintain for 1 to 2 hours in the temperature range of 1050 ℃ to 1150 ℃ while cooling to 1 ℃ to 3 ℃ per minute in the cooling step during the firing process.

In the above constitution, when the firing temperature is lower than 1200 ° C., it becomes an insulator, and when it is higher than 1250 ° C., the resistivity is large, and the characteristics of the thermistor are lowered, such as a gradient, R ratio, and withstand voltage drop, and the holding temperature during cooling is lower than 1050 ° C. If it is higher than 1150 ℃, there is no effect of changing the cooling condition. If the holding time is shorter than 1 hour or longer than 2 hours, there is no effect of changing the cooling condition. If the cooling rate is less than 1 ℃ / min, the actual speed is too slow. It is difficult to apply at the time and if it is more than 3 ℃ / min, there is no change effect of cooling condition.

Gradient in the above is defined by the following formula,

= Curie temperature

T ₂ = 50 ℃ higher than Curie temperature

R ₁ = resistance at temperature T ₁

R ₂ = Resistance value at temperature T ₂

Rmax / Rmin, which is an R ratio, is a ratio between the maximum resistance value and the minimum resistance value.

In FIG. 1, the maximum holding temperature is the part ② of FIG. 1, the maximum temperature holding time is the holding time in the part ②, the holding temperature in the cooling condition is the part ④, and the holding time is the holding time in the part ④, The cooling rate represents the cooling rate in the ③ and ⑤ parts.

As mentioned above, when the coprecipitation powder using chloride is used, the firing temperature is 1200 ° C to 1250 ° C, the holding temperature is 1050 ° C to 1150 ° C during the cooling process, and the holding time is 1 to 2 hours. When the cooling rate is 1 ° C. to 3 ° C./min, a static thermistor having excellent gradient and withstand voltage and excellent reproducibility can be obtained.

Through the following Examples and Comparative Examples will be described in detail with respect to the configuration and operation of the present invention. However, the following examples do not limit the scope of the present invention.

EXAMPLES 1-4

(1) Barium titanate composition preparation

96 mol of barium chloride (BaCl ₂ ), 101 mol of titanium tetrachloride (TiCl ₄ ), CaCl ₂ 4mol, YCl ₃ 0.11mol, AlCl ₃ 0.2mol, SiCl ₄ 0.5mol, LiCl 0.2mol, SbOCl 0.06mol, MnCl ₂ 0.08mol After mixing for about 30 minutes, 2.0 to 3.0 mol of a small amount of C ₂ H ₂ O ₄ 2HO solution was added as a coprecipitation agent to prepare a mixed barium titanyl oxalate as an intermediate, and the resulting intermediate was reacted at room temperature for 30 minutes to 1 hour. After filtration and vacuum filtration, the excess hydroxyl ions and residual chlorine (Cl) ions are removed by washing with water three to five times and dried in a drier at about 100 ° C. for 4 hours, and then heated at an elevated temperature of 4 ° C./min. Into an alumina crucible, the temperature was raised to 800 ° C. and maintained for 1 hour, followed by quenching.

Polyvinyl alcohol was added to the mixed barium titanate powder obtained by the above process as a binder, followed by wet mixing through a polyethylene-coated ball mill and media, followed by molding at a pressure of 1000 kg / cm 2 in a disk shape having a diameter of 24 mm and a thickness of 3 mm.

(2) firing method

As shown in Table 1, the molded product was always maintained at 0.5 or 1 hour at the highest holding temperature, and maintained at 1100 ° C, 1050 ° C or 1150 ° C for 1 hour or 2 hours while cooling to 2 ° C or 3 ° C per minute in the cooling step.

(3) Property measurement method

For the measurement of physical properties, the surface of the prepared final semiconductor magnetic material was ground with abrasive paper (# 100), and then the primary electrode was formed by nickel electroless plating. Then, the secondary electrode was formed by baking silver (Ag). After polishing, the characteristics were measured, and the resistivity was measured using a multimeter. The gradient and R ratio were measured in the same manner as described above, and the breakdown voltage (V _B ) was measured in a conventional breakdown voltage meter and is shown in Table 1.

Comparative Examples 1 to 8

The barium titanate composition prepared in the above Example was calcined by a method outside the scope of the present invention described in Table 1, and the physical properties thereof were measured in the same manner as described in Table 1, which is compared with that of the present invention. As can be seen that the gradient and R ratio are large and the voltage resistance is excellent.

[Reference Example]

This is not a starting material of chloride, but a solid phase reaction of an oxide as starting material. A mixture of 96 mol of barium carbonate (BaCO ₃ ), 101 mol of titanium oxide (TiO ₂ ), and 4 mol of calcium carbonate (CaCO ₃ ) is mixed with polyethylene. After wet mixing through the coated ball mill and media, it was dehydrated and calcined at 1150 ° C., and 0.11 mol Y ₂ O _3, 0.2 mol Al ₂ O _3, 0.5 mol SiO ₂ , 0.1 mol with respect to 100 mol of the calcined blend. Li ₂ CO ₃ , 0.06mol Sb ₂ O ₃ , 0.03mol MnCl ₂ , respectively, polyvinyl alcohol was added as a binder, wet-mixed through polyethylene coated ball mill and media, and then assembled. It was molded by applying a pressure of 1000 kg / cm 2 into a disk shape of and then calcined at 1350 ° C. for 1 hour.

The physical properties of this molded article were measured by the measuring method mentioned in the above examples and listed in Table 1.

Claims (1)

In the method for producing a barium titanate-based semiconductor magnetic composition using a powder by a coprecipitation method of chloride, the maximum holding temperature during firing is 1200 ° C to 1250 ° C, the holding time is 0.5 to 1 hour, and the cooling step is to 800 ° C. A method for producing a barium titanate-based semiconductor magnetic composition, wherein the barium titanate-based semiconductor magnetic composition is maintained at a temperature range of 1050 ° C to 1150 ° C for 1-2 hours while cooling at 1 ° C to 3 ° C / min.

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