WO2014084429A1

WO2014084429A1 - Method for preparing barium titanate, and barium titanate prepared by same

Info

Publication number: WO2014084429A1
Application number: PCT/KR2012/010349
Authority: WO
Inventors: 전보연; 박지호; 최연규
Original assignee: 삼성정밀화학 주식회사
Priority date: 2012-11-30
Filing date: 2012-11-30
Publication date: 2014-06-05
Also published as: CN108675785A; CN104797543A

Abstract

The present invention relates to a method for preparing barium titanyl oxalate, to a method for preparing barium titanate comprising same, and to barium titanyl oxalate and barium titanate prepared by said methods. The present invention is characterized in that synthesis conditions such as the synthesis temperature and the concentration of a material can be adjusted in the process of synthesizing barium titanyl oxalate, wherein the process is performed by the dropwise addition of an aqueous solution of barium chloride and an aqueous solution of titanyl chloride to an aqueous solution of oxalic acid. According to the present invention, barium titanyl oxalate having a large specific surface area can be prepared after the synthesis, and barium titanate having Ba/Ti mole ratio of 0.999 to 1.001 can be prepared.

Description

Method for producing barium titanate, and barium titanate produced thereby

The present invention relates to a method for producing barium titanate, and to barium titanate prepared thereby, and more particularly, to prepare barium titanyl oxalate powder having a high specific surface area by adjusting synthetic conditions such as dropping temperature and concentration of a reactant. And a method for producing barium titanate having a Ba / Ti molar ratio of 0.999 to 1.001.

Barium titanate is widely used as a raw material for multilayer ceramic capacitors, static ceramic capacitors, and piezoelectric materials. Barium titanate was conventionally manufactured by sintering titanium dioxide (TiO ₂ ) and barium carbonate (BaCO ₃ ) at a high temperature by a solid phase reaction, but in recent years, small-capacity large-capacity of MLCC (Multi Layer Ceramic Capacitor), high dielectric constant, dielectric thinning High lamination, low temperature firing, high frequency and high performance, high purity / composition uniformity, fine grain / particle uniformity, non-aggregation / high dispersibility, etc. are required. It is increasing. As the liquid phase synthesis method, for example, hydrothermal synthesis method, coprecipitation method (oxalate method), alkoxide method and the like have been developed, and the use thereof is rapidly increasing.

In the liquid phase synthesis method, the oxalate method is a method of preparing barium titanate powder by adding a mixed solution containing Ba and Ti ions to oxalic acid, precipitating it with a barium titanyl oxalate compound, and drying and calcining it. Barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O) is a precursor of barium titanate (BaTiO ₃ ).

Oxalate process, one of the conventional methods for producing barium titanate, was grown to particles of about 200 μm through aging of barium titanyl oxalate, which is a precursor for the synthesis of barium titanate, in order to stabilize product properties and increase yield. . However, when barium titanyl oxalate having a large particle size is heat-treated to produce barium titanate, there is a problem in that excessive aggregates are formed during the heat treatment to deteriorate the quality of the final product of barium titanate.

According to the present invention, barium titanyl oxalate (3-7 m 2 / g) having a high specific surface area is prepared by adjusting synthesis conditions such as dropping temperature and concentration of raw materials, and barium titanate having a Ba / Ti molar ratio of 0.999 to 1.001 is obtained. It is intended to provide a method of preparation.

A first embodiment of the present invention comprises the steps of preparing a barium chloride (BaCl ₂ ) aqueous solution and titanyl chloride (TiOCl ₂ ) aqueous solution (stock preparation step); Adding an aqueous barium chloride solution and the titanyl chloride solution to an oxalic acid solution to form a barium titanyl oxalate precipitate (dropping step); Aging the solution comprising the barium titanyl oxalate precipitate (aging step); Washing and drying the barium titanyl oxalate precipitate (recovery step); And pulverizing the recovered barium titanyl oxalate precipitate to obtain a barium titanyl oxalate powder (grinding step), wherein the specific surface area of barium titanyl oxalate recovered in the recovery step is controlled by adjusting the synthetic conditions. The Ba / Ti molar ratio of 3 to 7 m 2 / g of barium titanate prepared by calcining barium titanyl oxalate obtained after grinding may be a method for preparing barium titanate of 0.999 to 1.001.

In the first aspect of the present embodiment, the dropping step may be performed at a temperature of 30 ~ 50 ℃. In this case, the grinding step may be performed by ball milling. In addition, the grinding step may be performed until the specific surface area of the barium titanyl oxalate powder is 10 m 2 / g.

In a second aspect of the present embodiment, the concentration of the aqueous solution of barium chloride (BaCl ₂ ) is 0.84 to 1.05 mol / l, the concentration of the titanyl chloride (TiOCl ₂ ) is 0.8 to 1.0 mol / l, and the oxalic acid (Oxalic Acid) concentration may be 1.9 ~ 2.3 mol / L. In this case, the grinding step may be performed by ball milling. In addition, the grinding step may be performed until the specific surface area of the barium titanyl oxalate powder is 10 m 2 / g.

The second embodiment of the present invention may be barium titanyl oxalate prepared according to the first embodiment.

The third embodiment of the present invention may be a method for producing barium titanate for calcining barium titanyl oxalate of the second embodiment to produce barium titanate, and the calcination may be performed at 800 to 1000 ° C.

The fourth embodiment of the present invention may be barium titanate prepared according to the third embodiment, and the Ba / Ti molar ratio may be 0.999 to 1.001.

According to the present invention, barium titanyl oxalate powder having a high specific surface area (3 to 7 m 2 / g) can be prepared by adjusting the synthesis conditions such as the dropping temperature and the concentration of the reactant, and the Ba / Ti molar ratio of 0.999 Barium titanate having a particle distribution of 1.00.001 and uniform particle distribution.

1 is a flowchart of a method for producing barium titanyl oxalate powder according to one embodiment of the present invention.

2 is a scanning electron micrograph of the barium titanyl oxalate powder after synthesis according to Example 1. FIG.

3 is a scanning micrograph of the barium titanyl oxalate powder after milling according to Example 1.

4 is an X-ray diffraction pattern for barium titanate according to Example 1. FIG.

5 is a scanning electron micrograph of barium titanate according to Example 1;

6 is a scanning electron micrograph of the barium titanyl oxalate powder after synthesis according to Example 7. FIG.

7 is a scanning electron micrograph of the barium titanyl oxalate powder after synthesis according to Comparative Example 1.

8 is a scanning electron micrograph of the barium titanyl oxalate powder after grinding according to Comparative Example 1.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Embodiment of the present invention can be modified in various other forms, the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

1, the first embodiment of the present invention comprises the steps of preparing a barium chloride (BaCl ₂ ) aqueous solution and titanyl chloride (TiOCl ₂ ) aqueous solution (stock preparation step); Adding an aqueous barium chloride solution and the titanyl chloride solution to an oxalic acid solution to form a barium titanyl oxalate precipitate (dropping step); Aging the solution comprising barium titanyl oxalate precipitate (aging step); Washing and drying the barium titanyl oxalate precipitate (recovery step); And pulverizing the recovered barium titanyl oxalate precipitate to obtain barium titanyl oxalate powder (milling step), wherein the specific surface area of barium titanyl oxalate recovered in the step of recovering by adjusting the synthesis conditions is 3 ˜7 m 2 / g, the Ba / Ti molar ratio of barium titanate prepared by calcining barium titanyl oxalate obtained after pulverization may be a method for producing barium titanate of 0.999 to 1.001.

Hereinafter, first, the first aspect of the present embodiment will be described. The first aspect of this embodiment relates to the range of synthesis temperatures.

First, a barium chloride (BaCl ₂ ) solution and a titanyl chloride (TiOCl ₂ ) solution may be prepared (raw material preparation step). The barium chloride (BaCl ₂ ) solution and titanyl chloride (TiOCl ₂ ) solution may be an aqueous solution using water as a solvent.

Aqueous solution of barium chloride can usually be used by dissolving BaCl ₂ · 2H ₂ O in water. The concentration range may be 0.2 to 2.0 mol / l. When the concentration of the barium chloride solution is less than 0.2 mol / l, the productivity of barium titanate is low relative to the volume of the barium chloride solution, and when the concentration exceeds 2.0 mol / l, barium chloride is out of the solubility range of barium chloride in water. Can be precipitated.

The titanyl chloride aqueous solution is prepared by diluting titanium tetrachloride (TiCl ₄ ) in water and then stabilizing by adding hydrochloric acid (HCl), and the concentration range may be 0.2 to 2.0 mol / l. At this time, if the temperature is higher than 40 ℃ titanyl chloride may be precipitated as a solid titanium oxide to reduce the Ba / Ti molar ratio of barium titanate should be maintained at a temperature lower than 40 ℃.

Next, a barium chloride (BaCl ₂ ) solution and a titanyl chloride (TiOCl ₂ ) solution were added dropwise to the oxalic acid solution to form barium titanyl oxalate (BTO: BaTiO (C ₂ O ₄ ) ₂ 4H ₂ O) May form precipitates. In this process, barium titanyl oxalate, a precursor of barium titanate, may be synthesized. The barium chloride solution and titanylchloride solution can be added dropwise to the oxalic acid solution simultaneously. Specifically, a mixed solution of an aqueous barium chloride solution and a titanyl chloride solution may be added dropwise to an aqueous oxalic acid (H ₂ C ₂ O ₄ ) solution using a high-speed jet nozzle. The raw material solution can be mixed, for example, in a batch reactor. The solution may continue to stir during the dropping step. Through agitation, barium chloride and titanyl chloride can be induced to react uniformly with oxalic acid.

The dropping step may be performed at a temperature of 30 ° C ~ 50 ° C. Here, the dropping temperature means the temperature of the oxalic acid aqueous solution. When the dropping temperature is lower than 30 ° C., the reaction of barium chloride and titanyl chloride with oxalic acid may not be performed. When the dropping temperature is higher than 50 ° C., the oxalic acid is decomposed, rather barium chloride and titanyl The reaction of chloride with oxalic acid may be lowered. At this time, the mixed solution of the barium chloride solution and titanyl chloride solution should be kept below 30 ℃ to prevent precipitation.

Synthesis time can be controlled by adjusting the rate at which the raw material solution is added to the reactor, for example, the dropwise addition of the barium chloride aqueous solution and titanyl chloride aqueous solution to the oxalic acid aqueous solution. The mixed solution of the barium chloride aqueous solution and the titanyl chloride aqueous solution is nozzle-dropped into the oxalic acid aqueous solution to be added dropwise to 1 to 3 hours. This dropping time can be achieved by adjusting the injection speed of the nozzle.

A process of generating barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O) by dropwise adding an aqueous barium chloride solution and a titanyl chloride solution to an aqueous oxalic acid solution may be represented by the following Scheme 1.

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

According to Scheme 1, the molar ratio of barium chloride, titanyl chloride and oxalic acid is 1: 1: 2, but in practice it is possible to further add amounts of barium chloride and oxalic acid. Barium chloride may be added in consideration of this point because the reaction rate is slow. In the case of oxalic acid, some of the oxalic acid may be decomposed, and thus it may be added in consideration of this. In addition, an aqueous solution of oxalic acid may be used in an amount larger than that of an aqueous solution of barium chloride or an aqueous solution of titanyl chloride.

Next, the mixed solution containing the barium titanyl oxalate precipitate can be aged (aging step).

Barium titanyl oxalate may be formed by reaction of barium ions and titanium ions with oxalic acid. However, there may be barium ions and titanium ions that do not participate in the reaction with oxalic acid. By continuing to stir for a certain time, the ions that do not participate in the reaction may participate in the reaction.

Aging can be carried out at 70 ° C or lower. In general, after the synthesis of barium titanyl oxalate, the temperature may be increased to perform aging, because if the aging temperature is higher than 70 ° C., the oxalic acid may be decomposed and the reaction may be lowered.

On the other hand, the aging time has little effect on the Ba / Ti molar ratio of barium titanate, and therefore, after the aging temperature is determined, it may be advantageous for productivity to carry out aging for as short a time as possible.

The barium titanyl oxalate precipitate can then be washed and dried (recovery step).

The recovery step refers to a process of separating only solid barium titanyl oxalate precipitate. Recovery may be accomplished by separating solid barium titanyl oxalate crystal mass from the barium titanyl oxalate containing slurry using a centrifuge or a filter press. The recovered barium titanyl oxalate precipitate can wash the filtered barium titanyl oxalate with excess water.

The washed barium titanyl oxalate may be dried at a temperature of 400 ° C. or lower to remove the washing liquid. There are various methods of drying such as oven drying, vacuum drying and freeze drying, and it may be advantageous to dry for a short time at the lowest temperature possible to obtain a small particle size and uniform particle size distribution.

The specific surface area of the barium titanyl oxalate precipitate may be 3-7 m 2 / g. Preferably it may be 4-6 m 2 / g. If the specific surface area of the barium titanyl oxalate precipitate is less than 3 m 2 / g, the Ba / Ti mole ratio of barium titanate may be less than 0.999. If the specific surface area is greater than 7 m 2 / g, the Ba / Ti mole ratio of barium titanate is more than 1.001. Can be large. When the Ba / Ti molar ratio of barium titanate is outside the range of 0.999 to 1.001, dielectric properties of electronic products manufactured using barium titanate may be reduced.

Next, the recovered barium titanyl oxalate precipitate may be pulverized to obtain a barium titanyl oxalate powder (milling step). It is possible to obtain a barium titanyl oxalate powder having particles of a desired size by a top down method.

As the grinding method, a wet grinding method can be used. Wet grinding refers to a method in which barium titanyl oxalate is added to a wet mill such as beads mills, ball mills, and attrition mills together with a predetermined medium to grind. The grinding time needs to be appropriately controlled due to the difference in grinding force according to the grinding equipment, and can adjust the particle size by adjusting the grinding time.

As the medium, an organic medium such as alcohol or water such as deionized water may be used. The use of organic media is advantageous in terms of crushing efficiency and particle size, but it can increase costs. The use of water can simplify the process and reduce costs.

When water is used as the medium, the amount of water to be used may be 1 to 10 parts by weight based on 1 part by weight of barium titanyl oxalate. When the amount of water used is less than 1 part by weight, the viscosity may be large and there may be no grinding effect. When the amount of water is greater than 10 parts by weight, the productivity of barium titanyl oxalate may be low compared to the amount of water used.

The wet milled barium titanyl oxalate may be dried at a temperature below 400 ° C. to remove the used medium. There is no particular limitation on the drying temperature, but may be above the boiling point of the medium to evaporate and remove the medium used. Thereby, barium titanyl oxalate powder can be obtained.

The specific surface area of the barium titanyl oxalate powder obtained after the grinding step may be 10 m 2 / g or more.

Below, the 2nd side surface of this embodiment is demonstrated. The first aspect of this embodiment relates to the synthesis temperature range of titanylbarium oxalate, while the second aspect of this embodiment relates to the concentration range of the raw material regardless of the synthesis temperature range.

The concentration of the aqueous solution of barium clath (BaCl ₂ ) is 0.84 ~ 1.05 mol / L, the concentration of the titanyl chloride (TiOCl ₂ ) is 0.8 ~ 1.0 mol / L, the concentration of the oxalic acid (Oxalic Acid) is 1.9 ~ 2.3 mol / l. When the concentration of the raw material is less than the lower limit, as the concentration is lower, the reaction starting point is less formed, which may lower the reaction.

Usually the concentrations of barium chloride, titanyl chloride and oxalic acid may be 0.735 mol / l, 0.7 mol / l and 1.6 mol / l, respectively. However, the present invention is not limited thereto, and the concentration of the raw material may be increased. When the concentration of each raw material is increased, the reaction starting point between the raw materials increases by that much, thereby improving the reaction speed, which has the advantage of shortening the process time. Even so, the concentration of barium clath (BaCl ₂ ) may be 1.05 mol / l or less, the concentration of titanyl chloride (TiOCl ₂ ) may be 1.0 mol / l or less, and the concentration of oxalic acid (Oxalic Acid) may be 2.3 mol / l or less. When the concentration of the raw material is out of the above range, the concentration of the reactant is too high, rather the reaction may be lowered.

Another embodiment of the present invention may be a method for producing barium titanate, which calcinates barium titanyl oxalate powder prepared according to the previous embodiment to produce barium titanate.

Sagger or Tray can be used as a heating furnace for calcining the dried barium titanyl oxalate powder. Here, 'Sagger' means a refractory soil container, and may be, for example, a cube-shaped container having a bottom surface of a square shape.

The calcination temperature may be 800-1000 ° C. Barium titanate is hardly produced when the calcination temperature is lower than 800 ° C., and excessive growth of barium titanate particles may occur when it exceeds 1000 ° C. The temperature increase rate may be 0.5 ~ 10 ℃ / min. If the temperature increase rate is less than 0.5 ℃ / min, the process time is long, the productivity can be lowered, and if it exceeds 10 ℃ / min, the temperature distribution is not uniform depending on the position, which may result in uneven particle size of barium titanate.

Specifically, calcination is preferably performed at 950 ° C. for 2 hours.

Through the calcination process, barium titanate may be produced and impurities contained in the barium titanyl oxalate powder may be separated and removed. That is, it is possible to remove excess water and excess carbon dioxide gas as crystal water inside the barium titanyl oxalate crystal, and the barium titanate powder may be formed through the following reaction.

Scheme 2

BaTiO (C ₂ O ₄ ) ₂ 4H ₂ O → BaTiO (C ₂ O ₄ ) ₂ + 4H ₂ O

Scheme 3

BaTiO (C ₂ O ₄ ) ₂ + 1/2 O ₂ → BaCO ₃ + TiO ₂ + 2CO ₂

Scheme 4

BaCO ₃ + TiO ₂ → BaTiO ₃

Barium titanate prepared by calcining may have a Ba / Ti molar ratio of 0.999 to 1.001. If the Ba / Ti molar ratio is less than 0.999 or greater than 1.001, the characteristics of the electronic component such as a laminated ceramic capacitor manufactured using barium titanate may be deteriorated.

Barium titanate prepared by calcining may be present by agglomeration caused by necking between particles. Barium titanate may be milled to separate such aggregated powders. Grinding includes wet grinding using a mill such as beads mills, attrition mills, and ball mills with a predetermined medium, jet mills and disk mills. Dry grinding using the friction between the raw materials or the crusher without using a medium, such as) can be used. The pulverization step is for resolving agglomeration between the particles of barium titanate, and after the wet pulverization, a drying process may be additionally required. If not necessary, the grinding step may be omitted.

Strong grinding is necessary for a long time in order to grind without necking using a precursor of several hundred μm level. At this time, the barium titanate particles may be destroyed to generate a large amount of fine powder, which may lower particle size distribution and crystallinity. However, in the case of barium titanyl oxalate prepared according to the present embodiment, the particle diameter thereof is very small compared to the conventional one, and the amount of aggregates is significantly reduced to lower the grinding strength, thereby making the precursor particles uniform and finely powdered, thereby improving the properties. have.

Another embodiment of the present invention may be barium titanate prepared in the above method, the Ba / Ti molar ratio of barium titanate may be 0.999 ~ 1.001. When the Ba / Ti molar ratio is within the above range, it is possible to meet the performance of the multilayer ceramic capacitor manufactured using barium titanate.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[합성온도의 영향][Influence of Synthetic Temperature]

Synthesis of Barium Titanium Oxalate and Barium Titanate

In order to determine the effects of synthesis temperature, aging temperature and aging time on the specific surface area of barium titanyl oxalate and the Ba / Ti molar ratio of barium titanate after synthesis, the synthesis temperature, aging temperature and Changed the time.

The aqueous barium chloride solution and titanyl chloride solution were mixed well in a 4M ³ glass-lined reactor to prepare a mixed aqueous solution. In addition, an oxalic acid aqueous solution was prepared in a 6M3 reactor.

Thereafter, the mixed aqueous solution was sprayed on the oxalic acid solution at a rate of 2.5 L / min using a nozzle of a full con type. A diaphragm pump was used for the supply of the mixed aqueous solution during the nozzle spraying. At this time, the oxalic acid solution was sprayed while stirring with a stirrer, the stirring speed of the stirrer was maintained at 150rpm. The mixed aqueous solution was added dropwise for 2 hours.

Thereafter, aging was maintained while stirring to obtain a slurry containing barium titanyl oxalate. Thereafter, aging was performed.

The barium titanyl oxalate slurry was then filtered through a centrifuge and washed with excess water to a pH of 4 wash. The barium titanyl oxalate thus obtained was dried in an oven at a temperature of 200 ° C. for 12 hours to obtain a solid barium titanyl oxalate.

The synthesized barium titanyl oxalate was wet milled using a ball mill. The ball was used as a ceramic ball of 3mm, water was used as the medium, the rotation speed is 100rpm, the ball mill was carried out for 24 hours.

The barium titanyl oxalate slurry thus obtained was dried in an oven at a temperature of 200 ° C. for 12 hours to obtain a barium titanyl oxalate powder.

The prepared barium titanyl oxalate powder was calcined at 970 ° C. for 7 hours in an air atmosphere to obtain a barium titanate powder.

evaluation

The specific surface area of the prepared barium titanyl oxalate powder was measured, and the molar ratio (Ba / Ti) of the barium atoms to the titanium atoms of the barium titanate powder obtained by calcining the barium titanyl oxalate powder was measured. The results are shown in Table 1.

The specific surface area refers to the surface area per unit weight of barium titanate powder, which was measured by BET method using ASmeri2010 of Micromeritics.

Ba / Ti values were measured using an X-ray fluorescence spectrometer (XRF) from Philips.

Table 1

	BaCl ₂ (mol)	TiOCl ₂ (mol)	Oxalic acid (mol)	Dropping temperature (℃)	Aging temperature (℃)	Aging time (min)	Specific surface area of BaTiO (C ₂ O ₄ ) ₂ (㎡ / g)		Ba / Ti molar ratio of BaTiO ₃
	BaCl ₂ (mol)	TiOCl ₂ (mol)	Oxalic acid (mol)	Dropping temperature (℃)	Aging temperature (℃)	Aging time (min)	After synthesis	After milling	Ba / Ti molar ratio of BaTiO ₃
Comparative Example 1	0.735	0.7	1.6	70	70	30	2.81	7.88	0.9998
Comparative Example 2	0.735	0.7	1.6	20	70	30	6.21	13.35	0.9921
Example 1	0.735	0.7	1.6	30	70	30	5.78	12.43	1.0005
Example 2	0.735	0.7	1.6	40	70	30	4.85	9.87	0.9992
Example 3	0.735	0.7	1.6	50	70	30	3.96	9.54	0.9997
Comparative Example 3	0.735	0.7	1.6	80	80	30	2.68	6.92	0.9884
Example 4	0.735	0.7	1.6	40	40	30	4.03	10.31	0.9994
Example 5	0.735	0.7	1.6	40	40	60	3.99	10.25	0.9993

Referring to Table 1, Comparative Example 1 is a case where the dropping temperature is 70 ° C, and Examples 1 to 3 and Comparative Examples 2 and 3 are cases where the dropping temperature is changed from 20 ° C to 80 ° C. In Examples 1 to 3, the dropping temperature is 30 to 50 ° C., and after synthesis, the specific surface area of barium titanyl oxalate is in the range of 3 to 6 m 2 / g, and the Ba / Ti molar ratio is in the range of 0.999 to 1.001. . On the other hand, in the case of Comparative Example 2 Ba / Ti molar ratio is less than 0.999, because the dropping temperature is too low to 20 ℃ barium and titanium ions and oxalic acid was not properly reacted. In Comparative Example 3, the Ba / Ti molar ratio is less than 0.999, because the dropping temperature is too high to decompose oxalic acid and the reaction of barium ions and titanium ions with oxalic acid is reduced.

Referring to Examples 4 and 5, it can be seen that even if the aging time is changed, the characteristics of barium titanyl oxalate and barium titanate have little effect. In addition, when the specific surface area of the barium titanyl oxalate after grinding (milling) has 10 m 2 / g or more, it can be seen that the Ba / Ti molar ratio of barium titanate exists within the range of 0.999 to 1.001.

2 is a scanning electron micrograph of the barium titanyl oxalate powder after synthesis according to Example 1. FIG. 3 is a scanning electron micrograph of the barium titanyl oxalate powder after milling according to Example 1. FIG. 4 is an X-ray diffraction pattern for barium titanate according to Example 1. FIG. 5 is a scanning electron micrograph of barium titanate according to Example 1; 6 is a scanning electron micrograph of the barium titanyl oxalate powder after synthesis according to Comparative Example 1. 7 is a scanning electron micrograph of the barium titanyl oxalate powder after grinding according to Comparative Example 1.

[Influence of Raw Material Concentration ]

Barium titanyl oxalate and barium titanate were synthesized with varying concentrations of the raw materials (barium chloride, titanyl chloride), and evaluation was carried out as in the case of the influence of the synthesis temperature. Table 2 shows the synthesis conditions and the evaluation results.

TABLE 2

	BaCl ₂ (mol)	TiOCl ₂ (mol)	Oxalic acid (mol)	Dropping temperature (℃)	Aging temperature (℃)	Aging time (min)	Specific surface area of BaTiO (C ₂ O ₄ ) ₂ (㎡ / g)		Ba / Ti molar ratio of BaTiO ₃
	BaCl ₂ (mol)	TiOCl ₂ (mol)	Oxalic acid (mol)	Dropping temperature (℃)	Aging temperature (℃)	Aging time (min)	After synthesis	After milling	Ba / Ti molar ratio of BaTiO ₃
Comparative Example 1	0.735	0.7	1.6	70	70	30	2.81	7.88	0.9998
Comparative Example 4	0.368	0.35	0.8	70	70	30	2.11	6.95	0.9990
Comparative Example 5	0.525	0.5	1.15	70	70	30	2.35	7.21	0.9993
Example 6	0.848	0.8	1.92	70	70	30	6.85	11.98	0.9992
Example 7	1.050	1.0	2.30	70	70	30	6.90	12.41	1.0007
Comparative Example 6	1.260	1.2	2.76	70	70	30	8.53	12.95	1.0031

Referring to Table 2, Comparative Examples 4 and 5 have lower concentrations of barium chloride and titanyl chloride compared to Comparative Example 1, and have a specific surface area of barium titanyl oxalate smaller than 3 m 2 / g after synthesis. This is because barium ions and titanium ions do not react properly with oxalic acid.

Examples 6 and 7 show a case where the concentration of barium chloride is 0.84 to 1.05 mol, the concentration of titanyl chloride is 0.8 to 1.0 mol, and the concentration of oxalic acid is 1.9 to 2.3 mol, and after the synthesis of barium titanyl oxalate The specific surface area is in the range of 3 to 7 m 2 / g, and the Ba / Ti molar ratio of barium titanate is in the range of 0.999 to 1.001. 8 is a scanning electron micrograph of the barium titanyl oxalate powder after synthesis according to Example 7. FIG.

In Comparative Example 6, the Ba / Ti molar ratio of barium titanate is larger than 1.001, because the concentration of the reactant is too high, rather the reaction is lowered.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions should be considered to include plural meanings unless the context clearly dictates them. The terms “comprise” or “have” and the like mean that there is a feature, number, step, operation, component, or combination thereof described in the specification, but not intended to exclude it. The present invention is not limited by the above-described embodiment and the accompanying drawings, but is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

Claims

Preparing an aqueous solution of barium chloride (BaCl 2 ) and an aqueous solution of titanyl chloride (TiOCl 2 ) (raw material preparation step);

Adding an aqueous barium chloride solution and the titanyl chloride solution to an oxalic acid solution to form a barium titanyl oxalate precipitate (dropping step);

Aging the solution comprising the barium titanyl oxalate precipitate (aging step);

Washing and drying the barium titanyl oxalate precipitate (recovery step); And

Pulverizing the recovered barium titanyl oxalate precipitate to obtain a barium titanyl oxalate powder (milling step),

A method for producing barium titanate, wherein the specific surface area of barium titanyl oxalate recovered in the recovery step is 3 to 7 m 2 / g, and the Ba / Ti molar ratio of barium titanate prepared therefrom is 0.999 to 1.001.
The method of claim 1,

The dropping step is a method for producing barium titanate is carried out at a temperature of 30 ~ 50 ℃.
The method of claim 1,

The concentration of the aqueous solution of barium clath (BaCl 2 ) is 0.84 ~ 1.05 mol / L, the concentration of the titanyl chloride (TiOCl 2 ) is 0.8 ~ 1.0 mol / L, the concentration of the oxalic acid (Oxalic Acid) is 1.9 ~ Method for producing barium titanate of 2.3 mol / L.
The method according to claim 2 or 3,

The grinding step is a method for producing barium titanate is carried out by ball milling.
The method according to claim 2 or 3,

The grinding step is a method for producing barium titanate is carried out until the specific surface area of the barium titanyl oxalate powder is 10 m 2 / g.
A method for producing barium titanate further comprising calcining the barium titanyl oxalate powder of claim 1.
The method of claim 6,

The calcination is a method for producing barium titanate is carried out at 800 ~ 1000 ℃.
Barium titanate prepared according to the method of any one of claims 1 to 7.
The method of claim 8,

Barium titanate having a Ba / Ti molar ratio of 0.999 to 1.001.