TW201520173A - Method of preparing barium titanyl oxalate, and method of preparing barium titanate comprising the same - Google Patents

Abstract

Provided are a method of preparing barium titanyl oxalate and a method of preparing barium titanate. The method of preparing barium titanyl oxalate includes preparing a barium compound solution, a titanium compound solution, and an oxalic acid solution (a raw material solution preparing step); synthesizing BTO (BaTiO(C2O4)2,4H2O) by contacting the barium compound solution and the titanium compound solution with the oxalic acid solution (a BTO synthesis step); and wet-pulverizing the synthesized BTO (a BTO wet-pulverizing step), wherein the BTO wet-pulverizing step includes adding a dispersant to a BTO slurry including the synthesized BTO to reduce a viscosity of the BTO slurry.

Description

Method for preparing oxalate titanate and preparation method of barium titanate

The present invention relates to a method for preparing titanyl oxalate and a method for preparing barium titanate, and more particularly to a method for preparing titanyl oxalate to obtain a titanium oxide oxalate having a uniform particle size and an improved productivity by improving wet pulverization efficiency. A method of ruthenium and a method of preparing barium titanate to obtain barium titanate having high crystallinity and improved productivity.

Conventionally, barium titanate powder is prepared by a solid phase method in which titanium oxide (TiO ₂ ) is mixed with barium carbonate (BaCO ₃ ) to form a mixture and the mixture is heat-treated at a high temperature in a solid phase. However, various synthetic methods such as liquid phase method and gas phase method, and solid phase method are currently used for preparing barium titanate powder because barium titanate powder is required to have high purity/composition uniformity, fine particle/particle size uniformity, And non-condensation/high dispersibility (by high dielectric constant composition and thin layer and multilayer dielectric) according to recent trends in small size/large capacitance, low temperature sintering, high frequency and high performance multilayer ceramic capacitors (MLCC) . However, the coprecipitation method can be used to produce a highly crystalline barium titanate powder in a large amount, which is one of liquid phase methods for obtaining barium titanate powder having low manufacturing cost and chemical uniformity.

When a coprecipitation method is used, a liquid phase material containing barium and titanium is contacted with oxalic acid (H ₂ C ₂ O ₄ ) to form barium titanate oxalate (BaTiO(C ₂ O ₄ ) ₂ .4H ₂ O, hereinafter referred to as "BTO"), then BTO is heat-treated at a high temperature to synthesize barium titanate (BaTiO ₃ ) powder having an appropriate particle size. However, in the coprecipitation method, if the precipitated BTO is not pulverized to an appropriate particle size, the barium titanate (BT) particles formed after the heat treatment are strongly agglomerated with each other, and thus the agglomerated particles are separated from each other during the BT pulverization process. At that time, a large amount of fine powder can be produced, and the particle size distribution of BT can be expanded, and the crystallinity of BT can be made poor. In this regard, the grain refinement particles of BTO are required in the coprecipitation process due to the characteristics of BT as described above. Therefore, in the conventional coprecipitation method, a wet pulverization process having high pulverization efficiency is used, but since the pulverization process is performed, the viscosity of the BTO slurry is increased, and the pulverization efficiency may be lowered.

One embodiment of the present invention provides a method of preparing titanyl oxalate to obtain a titanyl oxalate having a small and uniform particle size and high productivity by improving wet pulverization efficiency.

Another embodiment of the present invention provides a method for preparing a titanyl oxalate to achieve a low viscosity oxalic acid titanate slurry by using a dispersant and improving drying efficiency by reducing the amount of solvent used in the wet pulverization process .

Another embodiment of the present invention provides a method of preparing barium titanate to improve the productivity of barium titanate and to produce barium titanate having no deterioration in properties and high crystallinity.

According to one aspect of the present invention, a method for preparing a bismuth oxalate titanate (BTO) comprises preparing a cerium compound solution, a titanium compound solution, and an oxalic acid solution (a raw material solution preparation step); by using the cerium compound solution and the titanium compound solution and The oxalic acid solution is contacted to synthesize BTO (BaTiO(C ₂ O ₄ ) ₂ .4H ₂ O) (BTO synthesis step); and wet-pulverizing the synthesized BTO (BTO wet pulverization step), wherein the BTO wet pulverization step A dispersant is added to the BTO slurry comprising the synthetic BTO to reduce the viscosity of the BTO slurry.

The ruthenium compound solution can be dissolved by dissolving at least one ruthenium compound selected from the group consisting of barium chloride (BaCl ₂ ), barium nitrate (Ba(NO ₃ ) ₂ ), and barium perchlorate (Ba(ClO ₄ ) ₂ ). Prepared in water, the titanium compound solution can be prepared by dissolving at least one titanium compound of titanium oxychloride (TiOCl ₂ ) and titanium tetrachloride (TiCl ₄ ) in water, and the oxalic acid solution can be dissolved by oxalic acid Prepared in water.

The BTO synthesis step can be carried out at a synthesis temperature in the range of 20 to 100 °C.

The amount of the dispersant added to the BTO slurry in the BTO wet pulverization step may be in the range of 0.1 part by weight to 1 part by weight based on 100 parts by weight of the synthesized BTO.

The dispersing agent can include a polymer, a sodium salt of a polymer, an ammonium salt of a polymer, an amine salt of a polymer, or a combination thereof.

The weight average molecular weight of the dispersant may range from 5,000 to 20,000.

The dispersing agent may include a sodium salt of a propylene-based copolymer, an ammonium salt of a polycarboxylic acid, an amine salt of propylene oxide, an amine salt of ethylene oxide, an amine salt of a polyester, an amine salt of a phosphate, or a combination thereof. .

The BTO wet pulverization step may include a first BTO wet pulverization step of pulverizing the synthesized BTO into a first size; and a second BTO wet pulverization step of pulverizing the BTO pulverized into the first size into a first The second size is smaller than the first size.

The BTO wet pulverization step can pulverize the BTO to have a volume average particle diameter (PSA D50) of 1.25 μm or less.

The method of preparing BTO may further include drying the wet pulverized BTO after the BTO wet pulverization step to obtain a BTO powder (BTO drying step).

The method of preparing BTO may further comprise aging the synthesized BTO; separating the aged BTO by filtration; and washing the separated BTO with excess water between the BTO synthesis step and the BTO wet pulverization step.

According to another aspect of the present invention, a method of preparing barium titanate comprises synthesizing barium titanate (BaTiO ₃ , hereinafter referred to as "BT") by calcining BTO at a temperature of 800 ° C to 1000 ° C.

The method of preparing BT may further comprise pulverizing the synthesized BT after the BT synthesis step (BT pulverization step).

One embodiment of the present invention provides a method for preparing titanyl oxalate, wherein the method can change particles to be pulverized into particles having a small particle size and a narrow particle size distribution, because the viscosity of the oxalate titanate slurry is introduced by The powder and the two-step wet pulverization are reduced as appropriate, and the method improves the drying efficiency per unit time by increasing the content of the solid matter.

Another embodiment of the present invention provides a method of preparing barium titanate, wherein the method improves barium titanate productivity and produces barium titanate having no deterioration properties and high crystallinity.

Figure 1 is an XRD pattern of barium titanate used to describe the definition of the k factor.

Best way

Hereinafter, a method for preparing titanyl oxalate and a method for preparing barium titanate according to one or more embodiments of the present invention are described in detail.

The method for preparing titanyl oxalate according to an embodiment of the present invention comprises the steps of preparing a cerium compound solution, a titanium compound solution and an oxalic acid solution (raw material solution preparing step); and using the cerium compound solution and the titanium compound solution with The step of synthesizing an oxalic acid solution to synthesize a titanium oxalate titanate (BaTiO(C ₂ O ₄ ) ₂ .4H ₂ O, hereinafter referred to as "BTO") (BTO synthesis step); and BTO synthesized by wet pulverization (BTO wet type) Smashing step).

The cerium compound solution can be dissolved in at least one cerium compound selected from the group consisting of barium chloride (BaCl ₂ ), barium nitrate (Ba(NO ₃ ) ₂ ), and barium perchlorate (Ba(ClO ₄ ) ₂ ). Prepared in water. The concentration of the cerium compound solution may range from 0.2 mol/L to 2.0 mol/L. When the concentration of the cerium compound solution is within this range, the productivity of barium titanate (hereinafter referred to as "BT") (which will be described later in detail) may be high in terms of the volume of the cerium compound solution, and The hydrazine compound does not precipitate.

The titanium compound solution can be prepared by dissolving at least one titanium compound selected from the group consisting of titanium oxychloride (TiOCl ₂ ) and titanium tetrachloride (TiCl ₄ ) in water. The concentration of the titanium compound solution may be from 0.2 mol/L to 2.0 mol/L. When the concentration of the titanium compound solution is within this range, the productivity of BT can be high in terms of the volume of the titanium compound solution, and the titanium compound does not precipitate.

The oxalic acid solution can be prepared by dissolving oxalic acid (H ₂ C ₂ O ₄ ) in water. Here, the amount of the oxalic acid solution used in the method may be greater than the amount of the cerium compound solution or the titanium compound solution used in the method. In particular, the concentration of the oxalic acid solution may range from 0.2 mol/L to 5.0 mol/L. When the concentration of the oxalic acid solution is within this range, the productivity of BT can be high in terms of the volume of the oxalic acid solution, and the oxalic acid can be completely dissolved in water.

The BTO synthesis step can be carried out at a synthesis temperature in the range of 20 to 100 ° C, for example, 50 to 90 ° C. When the synthesis temperature in the BTO synthesis step is within this range, the productivity of the BTO can be high, and the re-decomposition of the synthesized BTO can be prevented.

In the BTO synthesis step, the hydrazine compound solution and the titanium compound solution in the form of a mixture or a separate solution may be contacted simultaneously or sequentially with the oxalic acid solution. The contact can be carried out by nozzle spraying, and the period of contact (i.e., contact time) can be in the range of 1 to 3 hours. The contact time can be achieved by controlling the spray speed of the spray nozzle. The spray nozzle can be a single flow nozzle or a dual flow nozzle, depending on the flow of the fluid, but a single flow nozzle is preferred for ease of use or for uniform precipitation. One type of single flow nozzle can be fully tapered, hollow tapered or flat. For example, it is used to produce BTO (BaTiO(C ₂ O ₄ ) ₂ .4H ₂ O) by contacting an aqueous solution of ruthenium chloride as a solution of a ruthenium compound and an aqueous solution of titanium oxychloride as a solution of a titanium compound with an aqueous oxalic acid solution. The method can be represented by the following Reaction Scheme 1: [Reaction Scheme 1] BaCl ₂ . 2H ₂ O+TiOCl ₂ . +2H ₂ C ₂ O ₄ . 2H ₂ O→BaTiO(C ₂ O ₄ ) ₂ . 4H ₂ O+4HCl

Next, the method may include aging the synthesized BTO (BTO aging step), separating the BTO by filtration (BTO separation step), and washing the separated BTO with water (BTO washing step). The BTO aging step is preferably carried out for 0.5 to 2 hours to increase productivity. Here, the term "filtering" means a process of separating only the solid phase BTO from the BTO slurry containing BTO by using, in particular, a centrifugal separator or a filter press. Thereafter, the separated BTO can be washed with excess water until the pH of the wash solution becomes neutral (about 7).

Next, the washed BTO may be dried at a temperature ranging from 50 ° C to 300 ° C for 12 hours to 48 hours, as the case may be.

Subsequently, the BTO obtained by the process as described above may be wet pulverized (BTO wet pulverization step). Here, the term "wet pulverization" refers to a process of pulverizing BTO by adding BTO and a predetermined amount of medium to a wet pulverizer such as a bead mill, a ball mill or an attritor. Here, the term "medium" means an organic medium such as ethanol or water, such as deionized water. When an organic medium is used as the medium, it may be preferable in terms of pulverization efficiency or particle size control, but the cost may increase. Water is preferably used as a medium to simplify the process. And therefore it can reduce costs. When water is used as the medium, the amount of water used in the process may be in the range of 1 to 10 parts by weight based on 1 part by weight of the BTO. When the amount of water used in the process is within this range, the viscosity of the BTO slurry can be adapted to easily perform the pulverization of BTO, and the productivity of BTO can be high in terms of the volume of water. The pulverization time needs to be appropriately controlled because the pulverization power of each pulverizing apparatus can be different, and when the bead mill is used, the pulverization time can be in the range of 10 to 300 minutes. In this regard, the particle size of the BT powder as the final product can be appropriately adjusted by controlling the pulverization time.

A dispersant that reduces the viscosity of the BTO slurry including the synthesized BTO can be added in the BTO wet pulverization step. When a dispersant is added to the BTO slurry, the BTO wet pulverization efficiency can be improved while the chemical uniformity of the synthesized BTO can be maintained, and the physical properties of the BT (final product) are not deteriorated. The BTO slurry can further comprise water as well as BTO. In the present specification, the term "chemical uniformity of BTO" means that the crystal structure of BTO is not destroyed but is maintained in an initial state.

In the BTO wet pulverization step, the amount of the dispersant added to the BTO slurry may be in the range of 0.1 part by weight to 1 part by weight based on 100 parts by weight of the synthesized BTO. When the amount of the dispersant is within this range, a sufficiently high effect (i.e., a decrease in the viscosity of the BTO slurry) can be obtained even by using a small amount of a dispersant.

The dispersing agent can include a polymer, a sodium salt of a polymer, an ammonium salt of a polymer, an amine salt of a polymer, or a combination thereof.

The dispersing agent may include a sodium salt of a propylene-based copolymer, an ammonium salt of a polycarboxylic acid, an amine salt of propylene oxide, an amine salt of ethylene oxide, an amine salt of a polyester, An amine salt of a phosphate or a combination thereof.

The sodium salt of the propylene-based copolymer may be the sodium salt of polyacrylic acid.

The sodium salt of the propylene-based copolymer may be Dispex A40 (BASF), TH-1100 (Thwater) or Agrilan 782 (Akzonobel), which is sold as a dispersion solution.

Ammonium salt of polycarboxylic acid may be SYNTRAN (Interpolymer), Cerasperse5468CF (Sannopco ) or TAMOL ^TM 901 (DOW), sold in the form of a dispersion solution.

Amine salts of the polyester may be ^{Advantex (Taminco), SURFONAMINE ® (} Huntsman) or DISPARLON DA-325 (King Industries) , sold in the form of a dispersion solution.

The weight average molecular weight of the dispersant may range from 5,000 to 20,000.

The BTO wet pulverization step may include a first BTO wet pulverization step and a second wet pulverization step. In the first BTO wet pulverization step, the synthesized BTO is pulverized into a first size (for example, 0.9 μm to 1.0 μm). In the second BTO wet pulverization step, the BTO pulverized into the first size is pulverized into a smaller size, that is, a second size (for example, 0.2 μm to 0.8 μm). In this regard, the synthesized BTO can be uniformly pulverized by dividing the BTO wet pulverization step into two sub-steps.

When the BTO wet pulverization step is carried out by using a bead mill, beads having a size ranging from 0.65 mm to 1.0 mm can be used in the first BTO wet pulverization step, and beads having a size ranging from 0.03 mm to 0.3 mm The granules can be used in the second BTO wet comminution step.

The BTO wet pulverization step may pulverize the BTO to have a volume average particle diameter (PSA D50) of 1.25 μm or less (for example, 1.0 μm or less). The volume average particle size (PSA D50) was measured by using a particle size analyzer (Mastersizer 2000, Malvern).

In the BTO wet pulverization step, the wet pulverization efficiency of the BTO can be improved and the BTO can be uniformly pulverized by adding a dispersant and optionally dividing the wet pulverization step into two sub-steps. Therefore, BT having high crystallinity without deterioration in properties can be obtained, and therefore, since the concentration of the solid matter in the BTO slurry is increased, the productivity of BTO and BT can be improved.

Next, the wet pulverized BTO can be dried at 400 ° C or less to remove the medium used (BTO drying step). Thus, a dried BTO powder was obtained. In this case, in order to remove the medium used by evaporation, the drying temperature needs to be at least the boiling point of the medium or higher.

Subsequently, the BTO powder is filled in a heating furnace and then calcined at a temperature in the range of 800 ° C to 1000 ° C to synthesize barium titanate (BaTiO ₃ , hereinafter referred to as "BT") (BT synthesis step). In the BT synthesis step, when the calcination temperature is within this range, BT having a desired particle size (i.e., PSAD50 in the range of 0.08 μm to 0.5 μm) can be obtained. In the BT synthesis step, impurities, including moisture and/or carbon, may be removed. The rate at which the furnace temperature is increased from the drying temperature in the BTO drying step to the calcining temperature in the BT synthesis step may range from 0.5 ° C/min to 10 ° C/min, for example from 1 ° C/min to 5 ° C/min. When the rate of increasing the temperature is within this range, the productivity of BT is high, the temperature distribution may be uniform, and thus the particle diameter of the BT powder may be uniform. The moisture present as crystal water in the BTO crystal and the excess carbonic acid gas can be removed by performing the BT synthesis step in the manner as described above, and thus having BT particles having a particle diameter of several tens of nm to several hundreds of nm. The BT powder can be obtained by the process described in Reaction Schemes 2 to 4.

[Reaction Scheme 2] BaTiO(C ₂ O ₄ ) ₂ . 4H ₂ O → BaTiO(C ₂ O ₄ ) ₂ +4H ₂ O

[Reaction Scheme 3] BaTiO(C ₂ O ₄ ) ₂ + 1/2 O ₂ → BaCO ₃ + TiO ₂ + 2CO ₂

[Reaction Scheme 4] BaCO ₃ + TiO ₂ → BaTiO ₃

For the heat treatment of the dried BTO powder, a ceramic basin or tray can be used as a heating furnace. Here, the pottery basin represents a refractory clay container. The pottery basin may be, for example, a container having a hexahedral shape, having a reference plane, and having a square shape.

Hereinafter, the BT powder is obtained by pulverizing the BT generated through the BT synthesis step (BT pulverization step). However, the BT pulverization step can be omitted. The BT pulverizing step may be carried out by wet pulverization with a predetermined medium using a pulverizer such as a bead mill, an attritor or a ball mill or by using a collision between raw materials or when a medium is not used, such as a jet mill or The friction of the disc mill is carried out by dry pulverization. The BT comminution step is carried out for de-agglomeration of BT particles and requires additional drying treatment after wet comminution, but particularly limited equipment is not necessary for drying treatment. When a device having extremely high pulverization efficiency is used in the BT pulverization step, a large amount of fine powder can be generated as the BT particles are destroyed, and thus the particle size distribution and crystallinity of the BT particles can be made inferior. Therefore, only the necking between the BT particles can be achieved by Reduce the comminution force to divide without damaging the BT particles.

According to another aspect of the present invention, BT is prepared by using a method of preparing BT, which comprises a method of preparing BTO.

Hereinafter, the present invention will be described in further detail with reference to the following examples of the examples. The examples are for illustrative purposes only and are not intended to limit the scope of the invention.

Example

Examples 1 to 4 and Comparative Examples 1 to 4

(Synthesis and Aging BTO)

1320 L of a 1 mol/L cesium chloride aqueous solution and 1200 L of a 1 mol/L aqueous solution of titanium tetrachloride were mixed in a 4 M ³ glass-lined reaction vessel to prepare an aqueous mixture solution. Next, the aqueous solution of the mixture was sprayed in a 2520 L aqueous solution of oxalic acid having a concentration of 1 mol/L at a rate of 2.5 L/min using a full-cone nozzle, which was previously prepared and filled in a 6 M ³ reactor. When a nozzle spray is performed, a diaphragm pump is used to supply an aqueous mixture solution. Here, the aqueous solution of the mixture was sprayed while stirring the aqueous oxalic acid solution using a stirrer, and the stirring rate of the stirrer was maintained at 150 rpm. The temperature of the aqueous oxalic acid solution was maintained at 70 °C.

After the aqueous mixture solution was added dropwise for 2 hours, the reaction temperature (i.e., the temperature of the aqueous oxalic acid solution) was maintained for 1 hour, and then the contents of the reactor were air-cooled while maintaining stirring for aging for 1 hour. As a result, a BTO slurry containing BTO was obtained.

(Filtering the synthesized BTO slurry and washing the separated BTO)

The thus prepared BTO slurry is separated by using a centrifuge to separate BTO, and the separated BTO is washed with excess water to bring the pH of the waste washing solution to 6 or more, and thus the washed BTO is obtained.

(wet pulverization and drying of washed BTO)

Initial wet pulverization

Add 50 kg of washed BTO, 0.125 kg of dispersant (Cerasperse 5468CF, Sannopco), 250 kg of deionized water, and 0.5 kg of 29 vol% ammonia solution (8.4 moles, based on 100 moles of BTO) to the mixing tank and stir To produce a BTO slurry. Here, the pH of the BTO slurry is 9.3. Next, the BTO was wet-pulverized by using a 20 L horizontal bead mill (medium: deionized water) to have a volume average particle diameter (PSA D50) in the range of 0.9 μm to 1.0 μm, and the bead mill includes a size selection Beads from Table 1. Thus, preliminary wet comminution is performed by recycling the BTO slurry through a horizontal bead mill a plurality of times.

Secondary wet pulverization

The BTO slurry obtained by the preliminary wet pulverization was wet-pulverized by using a 20 L horizontal bead mill (medium: deionized water) to have a volume average particle diameter (PSA D50) in the range of 0.4 μm to 0.5 μm, which The bead mill comprises beads of the size listed in Table 1. The second wet pulverization is carried out by recycling the BTO slurry through a horizontal bead mill a plurality of times. Secondary wet pulverization is carried out as appropriate.

dry

BTO obtained after preliminary wet pulverization or secondary wet pulverization The slurry was dried in an oven at a temperature of 200 ° C for 12 hours to prepare a BTO powder.

(calcined, wet pulverized and dried)

The dried BTO powder was inserted into an electric furnace (RHK, ONEJOON) and heat-treated at a temperature of 970 ± 5 ° C for 3.5 hours. As a result, BT powder was obtained. Next, the BT powder was wet-pulverized by a 20 L horizontal bead mill (medium: deionized water) at a peripheral speed of 5 m/s (i.e., 1500 rpm) for 30 minutes, and the bead mill included a size of 0.65 mm. Beads. The BT slurry prepared by wet pulverization was dried in an oven at a temperature of 150 ° C for 24 hours. As a result, BT powder was obtained.

Evaluation example

Evaluation Example 1: Viscosity Evaluation of BTO Paste

After performing preliminary wet pulverization and optionally secondary wet pulverization on the BTO slurry prepared in one of Examples 1 to 4 and Comparative Examples 1 to 4, the viscosity of the obtained BTO slurry was adjusted by using viscosity. The measurement was performed by DV-III ULTRA, Brookfield, and the results are shown in Table 2.

Evaluation Example 2: Measurement of average particle size and particle size distribution of BTO

After completely drying the BTO slurry prepared in one of Examples 1 to 4 and Comparative Examples 1 to 4, the volume average particle diameter (PSA D50) and the 80% span value of the obtained BTO were measured, and the results are shown in the table. 2 in. Here, the volume average particle diameter (PSA D50) was measured by using a particle size analyzer (Mastersizer 2000, Malvern). Similarly, the term "80% span value" means an index that defines the particle size distribution. Here, PSA D10 represents a particle size equivalent to 10% by volume, which is equivalent to when the volume of the particles accumulates. By measuring the minimum particle size to the maximum particle size of 10% of the total volume, PSA D50 represents a particle size equivalent to 50% of the total volume, and PSA D90 represents a particle size equivalent to 90% by volume. The 80% span value was obtained by using Equation 1 below.

[Equation 1] 80% span value = (PSA D90-PSA D10) / (PSA D50)

Here, when the 80% span value is small, the particle size distribution is narrow, and when the 80% span value is high, the particle size distribution is wide.

Referring to Tables 1 and 2, the BTO pastes prepared in Examples 1 to 4 had a lower viscosity than the BTO slurry containing the same amount of solid matter prepared in Comparative Example 1. From these results, it was found that the method for producing BTO used in Examples 1 to 4 had higher pulverization efficiency and drying efficiency than the method for preparing BTO used in Comparative Example 1. Further, the PSA D50 and 80% span values of the BTOs prepared in Comparative Examples 2 to 4 were respectively equal to or smaller than the values of the BTOs prepared in Examples 1 to 4. However, the methods for preparing BTO used in Comparative Examples 2 to 4 were compared with the methods for preparing BTO used in Examples 1 to 4 by reducing solid matter. The content in the BTO slurry was used to lower the viscosity of BTO, and thus the method of preparing BTO used in Comparative Examples 2 to 4 can lower the BTO productivity.

Evaluation Example 3: Average particle diameter of BT synthesized

The volume average particle diameter (SEM D50) of the BT particles prepared in the examples and the comparative examples obtained after completion of drying was measured, and the results are shown in Table 3. Here, the image of the dried BT particles was obtained by using SEM (JSM-7400F, Jeol USA, Inc.), and the average particle diameter (each is the average of the longest axis and the shortest axis of each BT particle) Calculated by using an image analysis program (Image-Pro Plus version 4.5, Media Cybernetics), and the BT particle size (SEM D50) is calculated based on the average particle diameter, and the number of BT particles used for measurement is 800 or 800 or more.

Evaluation Example 4: Evaluation of crystallinity (k factor and c/a) of BT synthesized

The crystallinity (k factor and c/a) of BT synthesized in the examples and the comparative examples was measured by using XRD (D/Max 2000 series, Rigaku), and the results are shown in Table 3. In particular, the crystallinity of the synthesized BT is analyzed under the XRD analysis conditions including 2θ=44.5° to 46°: a scanning speed of 2 seconds/step and a step size of 0.02, and the voltage is 40 kV and The current is 200mA. Next, in the XRD pattern as shown in FIG. 1, the k factor of the BT particles is calculated as the ratio of the tetragonal phase fraction (I _t ) to the cubic phase fraction (I _c ) (I _t /I _c ). Similarly, the d-spacing values of the a-axis and the c-axis of the crystal lattice are respectively calculated, and then the c/a of the BT particles is calculated as its ratio. The results are shown in Table 3.

Evaluation Example 5: Evaluation of the specific surface area of the synthesized BT

The specific surface area of BT synthesized in the examples and the comparative examples was analyzed by using a specific surface area measuring instrument (Macsorb HM-1220, Mountech), and the results are shown in Table 3.

Referring to Tables 1 and 3, the BTs prepared in Examples 1 to 4 have a smaller volume average particle diameter (SEM D50) than the BT containing the same amount of solid matter prepared in Comparative Example 1 and Higher k factor and specific surface area. Also, the volume average particle diameter (SEM D50), k factor, c/a, and specific surface area of BT prepared in Comparative Examples 2 to 4 were smaller or larger than those of BT prepared in Examples 1 to 4. . However, the methods for preparing BT used in Comparative Examples 2 to 4 were compared with the methods for preparing BT used in Examples 1 to 4 to reduce BTO slurry by reducing the content of solid matter in the BTO slurry when preparing BTO. The viscosity, and thus the method of preparing BT used in Comparative Examples 2 to 4, can lower the BTO productivity. In this regard, the method of preparing BT used in Comparative Examples 2 to 4 can reduce BT productivity.

Although the present invention has been particularly shown and described with reference to the drawings and exemplary embodiments thereof, those skilled in the art should understand Variations may be made therein without departing from the spirit and scope of the invention as defined by the following claims.

Claims (11)

A method for preparing bismuth oxalate titanate (BTO), comprising: preparing a cerium compound solution, a titanium compound solution, and an oxalic acid solution (preparation step of a raw material solution); contacting the cerium compound solution and the titanium compound solution with the oxalic acid solution To synthesize BTO (BaTiO(C ₂ O ₄ ) ₂ .4H ₂ O) (BTO synthesis step); and wet pulverize the synthesized BTO (BTO wet pulverization step), wherein the BTO wet pulverization step comprises dispersing agent Add to the BTO slurry containing the synthesized BTO to reduce the viscosity of the BTO slurry. The method of claim 1, wherein the hydrazine compound solution is selected from the group consisting of barium chloride (BaCl ₂ ), barium nitrate (Ba(NO ₃ ) ₂ ), and barium perchlorate (Ba(ClO ₄ ) ₂ ). The prepared titanium compound solution is prepared by dissolving at least one cerium compound in water, and the titanium compound solution is prepared by dissolving at least one titanium compound of titanium oxychloride (TiOCl ₂ ) and titanium tetrachloride (TiCl ₄ ) in water, and The oxalic acid solution is prepared by dissolving oxalic acid in water. The method of claim 1, wherein the amount of the dispersant added to the BTO slurry in the BTO wet pulverization step is in the range of 0.1 part by weight to 1 part by weight based on 100 parts by weight of the synthesized BTO. Inside. The method of claim 1, wherein the dispersing agent comprises a polymer, a sodium salt of a polymer, an ammonium salt of a polymer, an amine salt of a polymer, or a combination thereof. The method of claim 4, wherein the dispersing agent comprises a sodium salt of a propylene-based copolymer, an ammonium salt of a polycarboxylic acid, an amine salt of propylene oxide, an amine salt of ethylene oxide, an amine of polyester a salt, an amine salt of a phosphate or a combination thereof. The method of claim 1, wherein the BTO wet pulverization step comprises a first BTO wet pulverization step of pulverizing the synthesized BTO into a first size; and a second BTO wet pulverization step, the step The BTO pulverized into the first size is pulverized into a second size, the second size being smaller than the first size. The method of claim 6, wherein the BTO wet pulverization step pulverizes the BTO to have a volume average particle diameter (PSA D50) of 1.25 μm or less. The method of claim 1, further comprising drying the wet-pulverized BTO after the BTO wet pulverization step to obtain a BTO powder (BTO drying step). The method of claim 1, further comprising: between the BTO synthesis step and the BTO wet pulverization step: aging the synthesized BTO; separating the aged BTO by filtration; and washing the separation with excess water BTO. A method for preparing barium titanate, which comprises synthesizing barium titanate (BaTiO ₃ , hereinafter referred to as "B" by calcining BTO prepared according to any one of claims 1 to 9 at a temperature of 800 ° C to 1000 ° C BT") (BT synthesis step). The method of claim 10, further comprising pulverizing the synthesized BT after the BT synthesis step (BT pulverization step).