KR20100118803A - A method of preparing barium titanate and barium titanate prepared by same - Google Patents

Abstract

PURPOSE: A manufacturing method of barium titanate, and the barium titanate manufactured therefrom are provided to improve the crystallinity of the barium titanate by heating the barium titanate with the higher temperature than the synthetic temperature. CONSTITUTION: A manufacturing method of barium titanate comprises the following steps: reacting raw materials containing titanium and barium to form the barium titanate after removing impurities from the materials; heating the barium titanate with the higher temperature than the synthetic temperature for improving the crystallinity; and cooling the barium titanate with the improved crystallinity.

Description

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

A method of producing barium titanate and barium titanate produced by the method are disclosed. More specifically, a method for producing barium titanate comprising heating to a temperature higher than the synthesis temperature of barium titanate to increase crystallinity and barium titanate prepared by the method and having high crystallinity are disclosed.

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 while having a uniform particle size distribution even at a particle size of 200 nm or less.

The prior art for producing such barium titanate powder is a method for producing 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 involves two heat treatment steps, thus increasing the process related costs and increasing the molar ratio (Ba / Ti) of barium titanate by adding BaCO ₃ before the second heat treatment step after the first heat treatment step. There is a disadvantage that the sinterability is reduced.

One embodiment of the present invention provides a method for producing barium titanate comprising the step of increasing the crystallinity by heating to a temperature higher than the synthesis temperature of barium titanate.

Another embodiment of the present invention provides a barium titanate prepared by the above production method with good crystallinity or narrow particle size distribution without high internal defects.

One aspect of the invention,

Reacting a raw material including titanium and barium to synthesize barium titanate (synthesis step);

Increasing the crystallinity by heating the synthesized barium titanate to a temperature higher than the temperature of the synthesis step (crystallinity enhancement step); And

It provides a method for producing barium titanate comprising the step (cooling step) of cooling the barium titanate improved crystallinity.

The method for producing barium titanate may further include removing impurities contained in the raw material (impurity removal step) before the synthesis step.

The impurity removing step may include heating the raw material at a linear heating rate.

The impurity may include at least one of moisture, hydroxyl (-OH), and carbon.

The moisture content may be 0.2% by weight or more based on the total weight of the raw material.

The impurity removing step may include removing impurities contained in the raw material in the form of at least one of water vapor, H ₂ , O _2, and COx to forcibly discharge them.

The synthesizing step may include simultaneously adjusting the particle size of the synthesized barium titanate.

The temperature of the crystallinity improving step may be 10 ~ 610 ℃ higher than the temperature of the synthesis step.

The temperature of the synthesis step may be 700 ~ 1300 ℃ and the temperature of the crystallinity improving step may be 710 ~ 1310 ℃.

At least one of the synthesis step and the crystallinity improving step may include an isothermal maintenance step.

The holding time of the synthesis step may be 1 to 5 hours.

The retention time of the crystallinity improving step may be 0 to 1 hour.

The method for producing barium titanate may further include a step of further synthesizing barium titanate by reacting an unreacted raw material between the crystallinity improving step and the cooling step (additional synthesis step).

The temperature of the additional synthesis step may be 10 ~ 610 ℃ lower than the temperature of the crystallinity improving step.

The difference between the temperature of the further synthesis step and the temperature of the synthesis step may be -50 ~ 50 ℃.

The further synthesis step may comprise an isothermal holding step.

The total holding time of the synthesis step and the additional synthesis step may be 1 to 5 hours.

The cooling step may include forced cooling at a natural cooling step or a linear cooling rate.

Another aspect of the invention,

It provides barium titanate prepared by the above production method.

According to one embodiment of the present invention, by heating to a temperature higher than the synthesis temperature of barium titanate to increase the crystallinity can be produced barium titanate having high crystallinity or narrow particle size distribution without internal defects A method for producing barium titanate may be provided.

According to another embodiment of the present invention, barium titanate prepared by the above production method may be provided.

Hereinafter, a method of manufacturing 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 method for producing barium titanate according to an embodiment of the present invention on a temperature-time graph.

Referring to Figure 1, the method for producing barium titanate according to an embodiment of the present invention uses a raw material including titanium and barium, impurities removal step (①), synthesis step (②), temperature rising step (③), It includes crystallinity improvement step (④), temperature reduction step (⑤), additional synthesis step (⑥) and cooling step (⑦).

The raw material may be in the form of a mixture or a composite. For example, the raw material may be a mixture of titanium dioxide (TiO ₂ ) and barium carbonate (BaCO ₃ ).

Impurity removal step (①) is a step of removing the impurities contained in the raw material, it may include the step of heating the raw material at a linear heating rate. The heating rate may be 20 ° C / min or less, for example 3 ° C / min or less. The impurity may include at least one of moisture, hydroxyl (-OH), and carbon, and in particular, the content of moisture may be 0.2% by weight or more relative to the total weight of the raw material. This impurity removal step (①) removes water or gas (H ₂ O, H ₂ , O ₂ , COx) by evaporating the water contained in the raw material or decomposing the hydroxyl group and / or the carbon-containing compound. At this time, if the generated moisture or gas remains in the heating facility (not shown), further evaporation of the moisture remaining in the raw material or further decomposition of the hydroxyl group and / or the carbon-containing compound is suppressed, thereby continuously generating the generated moisture and gas. Need to be discharged. Therefore, the impurity removal step (1) may forcibly discharge the water vapor, H ₂ , O ₂ and / or COx removed from the raw material to the outside of the heating installation by using an exhaust fan and / or an air blower.

Synthesis step (②) is a step of synthesizing barium titanate by reacting the raw material from which impurities are removed. The synthesizing step may include simultaneously adjusting the particle size of the synthesized barium titanate. That is, in the synthesis step, the synthesis of barium titanate and the particle size control of the synthesized barium titanate may be simultaneously performed. This synthesis step (②) may include an isothermal maintenance step. In Figure 1, the synthesis step (②) is shown as consisting only of the isothermal maintenance step, but the present invention is not limited thereto. Specifically, the synthesis step (②) may be maintained for 1 to 5 hours, for example 2 to 5 hours at a temperature of 700 ~ 1300 ℃. When the temperature and holding time of the synthesis step (②) are less than 700 ° C. and less than 1 hour, respectively, barium titanate is not synthesized or insufficiently synthesized, and the temperature and holding time of the synthesis step (②) are more than 1300 ° C. and 5 hours, respectively. If it is exceeded, it is not preferable because a problem that the particles are excessively large or the productivity is lowered occurs.

The temperature raising step ③ is a step of raising the temperature of the barium titanate to the temperature of the crystallinity improving step (④) described later at the temperature of the synthesis step (②).

Crystallinity improving step (④) is a step to increase the crystallinity of the barium titanate by heating the synthesized barium titanate to a temperature higher than the temperature of the synthesis step (②). The temperature of the crystallinity improving step (④) may be 10 ~ 600 ℃, for example 40 ~ 100 ℃ higher than the temperature of the synthesis step (②). If the temperature difference (temperature of ④-②) is less than 10 ℃ is not preferable because the effect of improving the crystallinity is not preferable, if it exceeds 600 ℃ it is not only difficult to produce particles of small size but also worsen the particle size distribution This is undesirable. In addition, the crystallinity improvement step (④) may include an isothermal maintenance step. In Figure 1, the crystallinity improving step (④) is shown as consisting only of the isothermal maintenance step, but the present invention is not limited thereto. Specifically, the crystallinity improving step (④) may be maintained for 0 to 1 hour, for example 0 to 30 minutes at a temperature of 710 ~ 1310 ℃. Here, that the holding time of the crystallinity improving step (4) is 0 minutes means that cooling starts immediately after reaching the temperature of the crystallinity improving step (4). When the temperature of the crystallinity improving step (④) is less than 710 ° C, the effect of improving the crystallinity of barium titanate is insignificant, and when the temperature and the holding time of the crystallinity improving step (④) are more than 1310 ° C and more than 1 hour, respectively. The particle size of barium titanate decreases.

The temperature reduction step (⑤) is a step of lowering the temperature of the barium titanate from the temperature of the crystallinity improving step (④) to the temperature of the additional synthesis step (⑥) described later.

An additional synthesis step (⑥) is a step of further synthesis of barium titanate by reacting unreacted raw materials. The temperature of the additional synthesis step (⑥) may be 10 ~ 600 ℃, for example 40 ~ 100 ℃ lower than the temperature of the crystallinity improving step (④). If the temperature difference (temperature of ④-⑥) is less than 10 ℃ because the effect of the temperature difference is insignificant, it is not preferable, if it exceeds 600 ℃ the temperature of the additional synthesis step (⑥) is too low to add the unreacted raw material It is not preferable because synthesis is difficult to expect. In addition, the additional synthesis step (⑥) may include an isothermal maintenance step. In Figure 1, the additional synthesis step (⑥) is shown as consisting only of the isothermal maintenance step, but the present invention is not limited thereto. In addition, the difference between the temperature of the additional synthesis step (⑥) and the temperature of the synthesis step (②) may be -50 ~ 50 ℃. When the temperature difference (temperature of ⑥-② of the temperature) is out of the above range, it is not preferable because it is out of the temperature range for further synthesis of unreacted material or the particle size distribution becomes worse. On the other hand, the total holding time of the synthesis step (②) and the additional synthesis step (⑥) may be 1 to 5 hours. If the total holding time is less than 1 hour, many unreacted substances remain or the particle size distribution decreases, which is not preferable, and if it exceeds 5 hours, the productivity is compared with the advantages (ie, removal of unreacted substances or uniformity of particle size distribution). This is excessively lowered, which is not preferable. In addition, this additional synthesis step 6 may be omitted.

The cooling step (⑦) is manufactured through the above-described impurity removal step (①) to the synthesis step (⑤), and through the additional synthesis step (⑥) to naturally cool or forcibly cool barium titanate at a linear cooling rate. Step. In the case of forced cooling, cooling at a rate of 20 ° C./min or less is advantageous in terms of improving crystallinity of barium titanate.

Barium titanate having a high crystallinity and a narrow particle size distribution can be produced by the method for producing barium titanate having the above structure.

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

Example

Example  1-4: Preparation of Barium Titanate by the Method of FIG.

As shown in Table 1 below, barium titanate was prepared by the method of FIG. 1 using a total of four raw materials including titanium and barium, respectively. In addition, the heat treatment conditions applied to each step of Figure 1 and the forced exhaust conditions in step ① are further shown in Table 1 below.

Comparative example  1-3: Preparation of barium titanate by the method of FIG.

As shown in Table 1 below, barium titanate was prepared by the method of FIG. 2 using three kinds of raw materials including titanium and barium, respectively. In addition, the heat treatment conditions applied to each step of FIG. 2 are further shown in Table 1 below.

TABLE 1

Note 1) Based on the total weight of the raw material.

Evaluation example

For each of the Examples 1 to 4 and Comparative Examples 1 to 3, the type of gas discharged in step ① was analyzed using a gas chromatograph, and the analysis results are shown in Table 2 below. In addition, the barium titanate prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were analyzed to measure average particle size, particle size distribution, crystallinity and internal defects, and the measurement results are further shown in Table 2 below. The average particle diameter and particle size distribution of barium titanate were measured using a scanning electron microscope (SEM), and the crystallinity was measured using XRD. Specifically, the crystallinity is a value calculated by the ratio of the c-axis and a-axis of the barium titanate crystal, the higher the value means that the crystallinity is good. In addition, the particle size distribution was qualitatively evaluated by three criteria ('wide', 'narrow' and 'very narrow' by observing SEM images of the same magnification). In addition, the 'internal defect' was measured using a transmission electron microscope (TEM), and specifically measured based on the extent to which defects such as pores were found in barium titanate particles during TEM analysis.

TABLE 2

Referring to Table 2, the barium titanate prepared in Examples 1 to 4 was found to have a higher crystallinity or a narrower particle size distribution than the barium titanate prepared in Comparative Examples 1 to 3 without internal defects. Therefore, the barium titanate prepared in Examples 1 to 4 is suitable for use in a multilayered and highly laminated multilayer ceramic capacitor.

Although the present invention has been described with reference to the examples, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a diagram schematically showing a method for producing barium titanate according to an embodiment of the present invention on a temperature-time graph.

2 is a diagram schematically showing a method for producing barium titanate according to the prior art on a temperature-time graph.

Claims (19)

Reacting a raw material including titanium and barium to synthesize barium titanate (synthesis step); Increasing the crystallinity by heating the synthesized barium titanate to a temperature higher than the temperature of the synthesis step (crystallinity enhancement step); And The barium titanate manufacturing method comprising the step of cooling the barium titanate improved crystallinity (cooling step). The method of claim 1, A method of producing barium titanate further comprising the step of removing impurities contained in the raw material (step of removing impurities) before the synthesis step. The method of claim 2, The impurity removing step is a method for producing barium titanate comprising the step of heating the raw material at a linear heating rate. The method of claim 2, The impurity is a method of producing barium titanate containing at least one of water, hydroxyl (-OH) and carbon. The method of claim 4, wherein The content of the water is a method of producing barium titanate is 0.2% by weight or more relative to the total weight of the raw material. The method of claim 4, wherein The impurity removing step includes the step of removing the impurities contained in the raw material in the form of at least one of steam, H ₂ , O ₂ and COx forcibly discharging them. The method of claim 1, The synthesizing step comprises the step of controlling the particle size of the synthesized barium titanate at the same time manufacturing method of barium titanate. The method of claim 1, The temperature of the crystallinity improving step is a method for producing barium titanate 10 ~ 600 ℃ higher than the temperature of the synthesis step. The method of claim 1, The temperature of the synthesis step is 700 ~ 1300 ℃, the temperature of the crystallinity improving step is a method of producing barium titanate is 710 ~ 1310 ℃. The method of claim 1, At least one of the synthesis step and the crystallinity improving step is a method for producing barium titanate comprising an isothermal maintenance step. The method of claim 1, The holding time of the synthesis step is a method for producing barium titanate is 1 to 5 hours. The method of claim 1, The holding time of the crystallinity improving step is a method of producing barium titanate is 0 ~ 1 hour. The method of claim 1, A method of producing barium titanate further comprising the step of further synthesizing barium titanate by reacting an unreacted raw material between the crystallinity improving step and the cooling step. The method of claim 13, The temperature of the further synthesis step is a method for producing barium titanate 10 ~ 600 ℃ lower than the temperature of the crystallinity improving step. The method of claim 13, The difference between the temperature of the further synthesis step and the temperature of the synthesis step is -50 ~ 50 ℃ a method for producing barium titanate. The method of claim 13, The further synthesis step is a method for producing barium titanate comprising an isothermal holding step. The method of claim 13, The total holding time of the synthesis step and the additional synthesis step is a method of producing barium titanate is 1 to 5 hours. The method of claim 1, The cooling step is a method of producing barium titanate comprising the step of forced cooling at the natural cooling step or linear cooling rate. Barium titanate produced by the manufacturing method according to any one of claims 1 to 18.

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