KR20120091688A - A method of preparing barium titanate and barium titanate prepared by the same - Google Patents

Abstract

PURPOSE: A manufacturing method of barium titanate and barium titanate manufactured by the method are provided to obtain high crystalline, uniform particle size of 100 nano meters or less by controlling temperature in an isothermal heat treatment stage. CONSTITUTION: A manufacturing method of barium titanate comprises the following steps: manufacturing gas by heating raw material which includes barium and titanium at a first heating speed; isothermally heat treating the outcome at a first temperature for a first hour in order to manufacture crystal nucleus; heating the outcome at a second heating rate up to a second temperature, and isothermally heat treating at the second temperature for the second hours in order to grow the barium titanate particle and enhance crystallinity of the particle; and cooling the outcome at a first cooling speed up to a third temperature. The second temperature is higher than the first temperature.

Description

Method for preparing barium titanate and barium titanate prepared by the method {A method of preparing barium titanate and barium titanate prepared by the same}

A method of producing barium titanate and barium titanate produced by the method are disclosed. More specifically, a first isothermal heat treatment step of generating crystal nuclei from a raw material containing barium and titanium, and an agent for growing barium titanate particles from the generated crystal nuclei and improving the crystallinity of the particles. Disclosed is a method for producing barium titanate comprising two isothermal heat treatment steps and barium titanate prepared by the method.

The barium titanate powder was conventionally manufactured by a solid phase reaction in which titanium dioxide (TiO ₂ ) and barium carbonate (BaCO ₃ ) were mixed and heat treated at a high temperature. High purity / composition uniformity, fine grain / particle uniformity, non-aggregation / high dispersion, etc. are required according to high dielectric constant composition, dielectric thinning and high lamination), low temperature plasticization, high frequency and high performance. It is manufactured by the synthesis method. In particular, as the multilayer ceramic capacitor becomes thin and highly laminated, there is a demand for barium titanate powder having high crystallinity with uniform particle size distribution even at an average particle size of 200 nm or less.

As a prior art for producing such barium titanate powder, there is a method for preparing barium titanate powder by oxalate process and barium titanate powder prepared by the method of Korean Patent Application No. 2007-0008972. However, the method presented here is a method of preparing a powder having high crystallinity while having a uniform particle size distribution of 200 nm or less, and has a disadvantage in that crystallinity is sharply decreased when preparing titanic acid powder of 100 nm or less.

In one embodiment of the present invention, a first isothermal heat treatment step of generating crystal nuclei from a raw material including barium and titanium, and growth of barium titanate particles from the generated nuclei and at the same time improve the crystallinity of the particles. It provides a method for producing barium titanate comprising a second isothermal heat treatment step.

Another embodiment of the present invention provides barium titanate having high crystallinity, uniform particle size distribution, and an average particle size of 100 nm or less.

According to an aspect of the present invention,

A method of producing barium titanate by heat-treating a raw material containing barium and titanium,

A first isothermal heat treatment step of generating crystal nuclei from the raw material; And

A second isothermal heat treatment step of growing barium titanate particles from the crystal grains thus formed and improving crystallinity of the particles,

It provides a method for producing barium titanate, the temperature of the second isothermal heat treatment step is higher than the temperature of the first isothermal heat treatment step.

Another aspect of the invention,

Heating the raw material comprising barium and titanium to a first temperature at a first heating rate to produce a gas;

Isothermally heat-treating the resultant of the gas generating step at a first temperature for a first time to generate crystal nuclei;

The resultant of the nucleation step is heated to a second temperature higher than the first temperature at a second heating rate, and then isothermally heat treated at the second temperature for a second time to obtain titanic acid from the produced crystal nuclei. Growing barium particles and improving the crystallinity of the particles; And

It provides a method for producing barium titanate comprising the step of cooling the result of the grain growth / crystallinity improvement step to a third temperature at a first cooling rate.

The method of manufacturing barium titanate may further include forcibly discharging the gas generated in the gas generating step.

The method of manufacturing barium titanate may further include cooling the resultant of the nucleation step to a fourth temperature at a second cooling rate between the nucleation step and the grain growth / crystallization improving step. Can be.

The second cooling rate is 3 ~ 10 ℃ / min, the fourth temperature may be 20 ~ 400 ℃.

The raw material may include barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O].

The raw material may include a barium compound and a titanium compound.

The barium compound may include at least one compound selected from the group consisting of barium chloride, barium carbonate and barium hydroxide.

The titanium compound may include at least one compound selected from the group consisting of titanium tetrachloride, titanium dioxide, and titanium oxychloride.

The gas may comprise at least one component selected from the group consisting of water vapor, H ₂ , O ₂ and CO _x .

The first heating rate may be 10 ° C / min or less.

The second heating rate may be 10 ~ 30 ℃ / min.

The first temperature may be 300 to 700 ° C., and the first time may be 1 to 10 hours.

The second temperature may be 800 to 1200 ° C., and the second time may be 0 to 1 hour.

The difference between the second temperature and the first temperature may be 100 ~ 900 ℃.

The first cooling rate is 20 ℃ / min or less, the third temperature may be 20 ~ 100 ℃.

Another aspect of the invention,

It is prepared according to the method for producing barium titanate, and provides barium titanate having a crystallinity of 1.0090 or more and a particle size of 100 nm or less.

According to one embodiment of the present invention, barium titanate having a high crystallinity, uniform particle size distribution, and an average particle size of 100 nm or less, and a method of manufacturing the same may be provided.

1 is a diagram schematically showing a heat treatment process introduced in a method of manufacturing barium titanate according to an embodiment of the present invention on a temperature-time graph.
FIG. 2 is a diagram schematically showing a heat treatment process introduced in a method of manufacturing barium titanate according to another embodiment of the present invention on a temperature-time graph.
3 is a diagram schematically showing a heat treatment process introduced in a method of manufacturing barium titanate according to the prior art on a temperature-time graph.

Hereinafter, a method of preparing barium titanate according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram schematically showing a heat treatment process introduced in the method for producing barium titanate according to an embodiment of the present invention on a temperature-time graph, and FIG. 2 is a method for producing barium titanate according to another embodiment of the present invention. The heat treatment process introduced in the diagram is shown schematically on a temperature-time graph.

Method for producing barium titanate according to an embodiment of the present invention is a method for producing barium titanate by heat-treating the raw material containing barium and titanium, the first isothermal heat treatment step of generating crystal nuclei from the raw material (Fig. 1 and Fig. 2)) and a second isothermal heat treatment step (⑤ of FIGS. 1 and 2) for growing barium titanate particles from the crystal grains and improving the crystallinity of the particles, wherein the second isothermal heat treatment step is performed. The temperature of is higher than the temperature of the first isothermal heat treatment step.

Referring to FIG. 1, in the method of manufacturing barium titanate according to one embodiment of the present invention, a gas is produced by heating a raw material including barium and titanium to a first temperature at a first heating rate (①) and the gas. Generating a crystal nucleus by isothermally heat-treating the resultant product of the producing step at a first temperature for a first time (②), cooling the resultant product of the crystal forming step to a fourth temperature at a second cooling rate (③), The result of the nucleation step is heated to a second temperature higher than the first temperature at a second heating rate (this is called a temperature raising step (④)), and then isothermally heat treated at the second temperature for a second time ( This isothermal heat treatment step (⑤)) to grow the barium titanate particles from the resulting crystal nuclei and to improve the crystallinity of the particles (④ and ⑤) and the result of the particle growth / crystallinity improvement step 1 cooling rate By including the step of cooling to the third temperature (⑥).

The heat treatment (① and ②) of the cooling step (③) and the previous step, and the heat treatment (⑤ and / or ⑥) of the temperature raising step (④) and subsequent steps are performed in different heating facilities (not shown). Can be. In addition, the temperature increase step (④) may proceed immediately after the end of the cooling step (③), or may proceed after a predetermined time elapses.

The raw material may be in the form of a mixture or a composite.

The raw material may include barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O]. In this case, the barium titanyl oxalate may be prepared by a coprecipitation method as disclosed in Korean Patent No. 2007-0008972.

On the other hand, the raw material may include a barium compound and a titanium compound. In this case, the barium compound may include at least one compound selected from the group consisting of barium chloride, barium carbonate and barium hydroxide, and the titanium compound is at least selected from the group consisting of titanium tetrachloride, titanium dioxide and titanium oxychloride. It may include one compound.

In the gas generating step ①, the raw material is heated to a temperature (ie, the first temperature) of the crystal nucleation step ②. This gas generation step (1) evaporates the water contained in the raw material or decomposes the hydroxyl group and / or the carbon-containing compound to remove it in the form of gas such as water vapor, H ₂ O, H ₂ , O ₂ or CO _x . .

The first heating rate may be 10 ° C / min or less, for example 3 ° C / min or less. When the first heating rate is within the above range, gas is discharged to facilitate crystal nucleation and grain growth.

When the gas generated in the gas generating step (1) remains in the heating facility (not shown), further evaporation of water remaining in the raw material or further decomposition of the hydroxyl group and / or the carbon-containing compound are suppressed. It is necessary to discharge continuously. Therefore, the method of manufacturing the barium titanate may further include forcibly discharging the gas generated in the gas generating step (1) to the outside of the heating installation. In this case, as a method of discharging the gas, a method of forcibly discharging the gas by installing an exhaust fan in the heating facility, injecting outside air or a specific gas into the heating facility, and pushing out the gas remaining in the facility, or Combinations of the two methods can be used.

The crystal nucleation step (2) generates crystal nuclei from the result of the gas generating step (1).

The first temperature may be 300 ~ 700 ℃. If the first temperature is within the above range, it is possible to obtain barium titanate having an average particle size of 100 nm or less through further heat treatments ④, ⑤, and ⑥. The first temperature may be, for example, 400 ~ 600 ℃. In addition, the first time may be 1 to 10 hours. If the first time is within the range, it is possible to maximize the yield of crystal nuclei generated from the result of the gas generation step (①). The first time may be, for example, 3-10 hours.

The cooling step ③ is included in consideration of operational convenience and / or performance limitations of the heating installation. This cooling step ③ may be omitted, as shown in FIG. In this case, all the heat treatment processes ①, ②, ④, ⑤ and ⑥ can be performed in the same heating facility.

The second cooling rate is 3 ~ 10 ℃ / min, the fourth temperature may be 20 ~ 400 ℃. When the second cooling rate and the fourth temperature are each within the above ranges, efficient production of barium titanate is possible.

The grain growth / crystallinity improvement steps ④ and ⑤ include a temperature raising step ④ and an isothermal heat treatment step ⑤.

The temperature raising step ④ heats the result of the crystal nucleation step ② or the result of the cooling step ③ to the temperature (ie, the second temperature) of the isothermal heat treatment step ⑤.

The second heating rate may be 10 ~ 30 ℃ / min. When the second heating rate is within the above range, excellent particle size distribution control effect and crystallinity improvement effect can be obtained without applying thermal shock to the heating equipment. The second heating rate may be, for example, 15 to 25 ° C / min.

The second temperature may be 800 ~ 1200 ℃. If the second temperature is within the above range, an excellent crystallinity improving effect can be obtained while maintaining a uniform particle size distribution. In addition, the second time may be 0 to 1 hour. If the second time is within the above range, a crystallinity improving effect can be obtained and particle growth can be limited. The second time may be, for example, 0 to 30 minutes. Here, that the second time is 0 hours or 0 minutes means that cooling is started as soon as the second temperature is reached.

On the other hand, the difference between the second temperature and the first temperature may be 100 ~ 900 ℃. If the temperature difference is within the above range, an effect of improving crystallinity can be expected.

The cooling step (⑥) cools the barium titanate produced through the above-described gas generation step (1) to the grain growth / crystallinity improving step (5) in a furnace or forcibly cools it at a linear cooling rate. The first cooling rate may be 20 ° C / min or less. If the first cooling rate is within the above range, it is advantageous in terms of improving crystallinity of barium titanate.

The third temperature may be 20 ~ 100 ℃. If the third temperature is within the above range, formation of crystal nuclei proceeds smoothly.

In the method of manufacturing barium titanate of FIG. 2, the cooling step ③ is omitted in the method of manufacturing barium titanate of FIG. 1, and the other steps ①, ②, ④, ⑤, and ⑥ correspond to the corresponding steps of FIG. 1. same.

According to the method for producing barium titanate having the above structure, it is possible to obtain barium titanate having a crystallinity of 1.0090 or more, uniform particle size distribution, and a particle size of 100 nm or less.

When barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O] manufactured by coprecipitation is used as the raw material, the temperature during the gas generation step (①) to cooling step (⑥) is performed. The reactions that occur in each section are shown in Table 1 below (Journal of the Ceramic Society of Japan 107 [1] (2008) 27-30 [98]).

Temperature range Main reaction Scheme 25 ~ 180 ℃ -Dehydration reaction BaTiO (C ₂ O ₄ ) ₂ ㆍ 4H ₂ O → BaTiO (C ₂ O ₄ ) ₂ + 4H ₂ O 180 ~ 250 ℃ -Decomposition reaction 2BaTiO (C ₂ O ₄ ) ₂ → Ba ₂ Ti ₂ O ₂ (C ₂ O ₄ ) ₃ ㆍ CO ₃ + CO 250 ~ 450 ℃ -Decomposition reaction Ba ₂ Ti ₂ O ₂ (C ₂ O ₄ ) ₃ ㆍ CO ₃ → Ba ₂ Ti ₂ O ₅ CO ₃ (CO ₂ ) + 2CO ₂ + 3CO 450 ~ 600 ℃ -Decomposition reaction Ba ₂ Ti ₂ O ₅ CO ₃ (CO ₂ ) → Ba ₂ Ti ₂ O ₅ CO ₃ + CO ₂ 600 ~ 750 ℃ -Particle growth / crystallinity improvement reaction Ba ₂ Ti ₂ O ₅ CO ₃ → ₂ BaTiO ₃ + CO ₂

 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example

Example  1-8: Preparation of Barium Titanate by the Heat Treatment Method of FIG.

Barium titanyl oxalate was prepared using the coprecipitation method disclosed in Korean Patent Publication No. 2007-0008972. Next, barium titanate was prepared by the heat treatment method of FIG. 1 using barium titanyl oxalate prepared as a raw material. In this case, an exhaust fan was used to forcibly discharge the gas generated in step ① of FIG. In addition, the heat treatment conditions applied to each step of Figure 1 are shown in Table 2 below.

Comparative example  1: Preparation of barium titanate by the heat treatment method of Figure 3

Barium titanate was prepared in the same manner as in Examples 1 to 8 except that the heat treatment method of FIG. 3 was used instead of the heat treatment method of FIG. 1. In addition, the heat treatment conditions applied to each step of Figure 3 is shown in Table 2 below. However, in step ① of FIG. 3, all reactions occurring in steps ①, ② and ④ of FIG. 1 occur.

division ① of step
First heating rate
(℃ / min) ② Step ③ Step
④ of step
2nd heating rate
(℃ / min) ⑤ step ⑥ Step 1st
Temperature
(℃) 1st
time
(hr) 2nd cooling rate
(℃ / min) 4th
Temperature
(℃) Second temperature
(℃) 2nd time
(min) 1st
Cooling
speed
(℃ /
min) Third temperature (℃) Example 1 3 400 3 3 200 30 900 10 20 25 Example 2 3 400 3 3 200 30 900 10 10 25 Example 3 3 400 3 3 200 30 900 30 Ronin 25 Example 4 10 400 3 3 200 30 900 10 10 25 Example 5 3 400 3 3 200 10 900 10 10 25 Example 6 3 600 3 3 200 30 900 10 10 25 Example 7 3 600 10 3 200 30 900 10 10 25 Example 8 3 400 3 3 200 30 900 0 10 25 Comparative Example 1 3 - - - - - 900 180 10 25

Evaluation example

After analyzing the barium titanate prepared in Examples 1 to 8 and Comparative Example 1, respectively, the crystallinity (c / a), the average particle size and the particle size distribution (D ₁₀ / D ₅₀ , D ₅₀ / D ₉₀ ) was measured, The measurement results are shown in Table 3 below.

The crystallinity (c / a) is a crystal lattice by measuring 2Θ = 44 ~ 46.5 ° at the speed of 2 sec / step and 0.02 step size at 40kV, 200mA using XRD (Rigaku D / Max 2000 series) The d-spacing values of the a-axis and the c-axis of are the indexes for evaluating the crystallinity of barium titanate using these ratios.

The average particle size and D ₁₀ / D ₅₀ and D ₅₀ / D _{90, which} are indicators of the particle size distribution, were obtained by the following method. In other words, SEM images of barium titanate particles were taken 50,000 times using Jeol's JSM-7400F, and the average of the major and minor axis lengths of the barium titanate particles was measured using an image analysis program (ImagePro Plus ver 4.5). The size of the barium titanate particles was calculated, and the number of measured barium titanate particles was 800 or more. Here, the larger the D ₁₀ / D ₅₀ and the D ₅₀ / D ₉₀ , the more uniform the particle size distribution. Here, D _{10 ,} D _{50 ,} D ₉₀ is the particle size of the particles corresponding to the rank of 10%, 50%, 90% respectively of the total particles when the measured particles are arranged in order from smallest to largest it means.

Crystallinity
(c / a) Average particle size
(nm) Particle size distribution D ₁₀ / D ₅₀ D ₅₀ / D ₉₀ Example 1 1.0093 95 0.69 0.62 Example 2 1.0095 98 0.70 0.63 Example 3 1.0090 100 0.65 0.63 Example 4 1.0085 98 0.54 0.58 Example 5 1.0090 98 0.65 0.57 Example 6 1.0085 100 0.55 0.58 Example 7 1.0088 100 0.55 0.54 Example 8 1.0088 95 0.69 0.62 Comparative Example 1 1.0073 90 0.50 0.48

Referring to Table 3, the barium titanate prepared in Examples 1 to 8 was found to have a higher crystallinity and a uniform particle size distribution than the barium titanate prepared in Comparative Example 1. In addition, the barium titanate prepared in Examples 1 to 8 was found to have an average particle size of 100nm or less. Accordingly, the barium titanate prepared in Examples 1 to 8 is suitable for use in a thin and highly laminated multilayer ceramic capacitor.

Although the present invention has been described with reference to the drawings and embodiments, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (17)

A method of producing barium titanate by heat-treating a raw material containing barium and titanium,
A first isothermal heat treatment step of generating crystal nuclei from the raw material; And
A second isothermal heat treatment step of growing barium titanate particles from the crystal grains thus formed and improving crystallinity of the particles,
A method for producing barium titanate, wherein the temperature of the second isothermal heat treatment step is higher than the temperature of the first isothermal heat treatment step. Heating the raw material comprising barium and titanium to a first temperature at a first heating rate to produce a gas;
Isothermally heat-treating the resultant of the gas generating step at a first temperature for a first time to generate crystal nuclei;
The resultant of the nucleation step is heated to a second temperature higher than the first temperature at a second heating rate, and then isothermally heat treated at the second temperature for a second time to obtain titanic acid from the produced crystal nuclei. Growing barium particles and improving the crystallinity of the particles; And
And cooling the resultant of the grain growth / crystallinity improving step to a third temperature at a first cooling rate. The method of claim 2,
And forcibly discharging the gas generated in the gas generating step. The method of claim 2,
Between the crystal nucleation step and the grain growth / crystallinity improvement step, further comprising the step of cooling the product of the crystal nucleation step to a fourth temperature at a second cooling rate. The method of claim 4, wherein
The second cooling rate is 3 ~ 10 ℃ / min, the fourth temperature is 20 ~ 400 ℃ method for producing barium titanate. The method according to claim 1 or 2,
The raw material is a method for producing barium titanate containing barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ 4H ₂ O]. The method according to claim 1 or 2,
The raw material is a method for producing barium titanate containing a barium compound and a titanium compound. The method of claim 7, wherein
The barium compound is a method of producing barium titanate comprising at least one compound selected from the group consisting of barium chloride, barium carbonate and barium hydroxide. The method of claim 7, wherein
The titanium compound is a method of producing barium titanate comprising at least one compound selected from the group consisting of titanium tetrachloride, titanium dioxide and titanium oxychloride. The method of claim 2,
The gas is a method for producing barium titanate comprising at least one component selected from the group consisting of water vapor, H ₂ , O ₂ and CO _x . The method of claim 2,
The first heating rate is a method for producing barium titanate is 10 ℃ / min or less. The method of claim 2,
The second heating rate is a method of producing barium titanate is 10 ~ 30 ℃ / min. The method of claim 2,
The first temperature is 300 ~ 700 ℃, the first time is a method of producing barium titanate 1 ~ 10 hours. The method of claim 2,
The second temperature is 800 ~ 1200 ℃, the second time is a method of producing barium titanate 0 ~ 1 hour. The method of claim 2,
The difference between the second temperature and the first temperature is a method of producing barium titanate is 100 ~ 900 ℃. The method of claim 2,
The first cooling rate is 20 ℃ / min or less, the third temperature is 20 ~ 100 ℃ manufacturing method of barium titanate. Barium titanate prepared according to the method of claim 1 or 2, having a crystallinity of 1.0090 or more and a particle size of 100 nm or less.

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