JP2006348026A - Method for producing barium titanyl oxalate and method for producing barium titanate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-purity barium titanyl oxalate with its specific surface area change for calcining temperature suppressed to low levels in stable quality and in high yield. <P>SOLUTION: A method for producing the barium titanyl oxalate is provided, comprising adding an aqueous solution(A-liquid) containing titanium tetrachloride and barium chloride to an aqueous solution(B-liquid) containing oxalic acid and titanium tetrachloride followed by conducting an aging reaction at 50°C or higher. In the thus obtained barium titanyl oxalate, the molar ratio Ba/Ti is preferably less than 1, more preferably 0.990 to 0.999. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention particularly relates to a method for producing barium titanyl oxalate useful as a raw material for functional ceramics such as piezoelectric materials, optoelectronic materials, dielectric materials, semiconductors, and sensors, and a method for producing barium titanate using the same. .

Conventionally, barium titanate is produced by a wet method such as a solid phase method, a hydrothermal synthesis method, an oxalate method, or an alkoxide method. Among these, in the oxalate method, an aqueous solution of TiCl ₄ and BaCl ₂ is dropped into an aqueous solution of H ₂ C ₂ O _{4 at} about 80 ° C. with stirring to obtain barium titanyl oxalate having a Ba / Ti molar ratio of 1. A method of calcining the barium titanyl oxalate is general. The characteristics of this oxalate method are that the composition of the obtained barium titanyl oxalate is uniform and that the target product can be obtained in a stable molar ratio with a good yield. In many cases, the molar ratio (Ba / Ti) is about 1. However, on the other hand, it is difficult to obtain barium titanyl oxalate having a molar ratio (Ba / Ti) of less than 1 with good yield and stable quality. In addition, when the molar ratio of Ba and Ti is approximately 1, there is a problem that the specific surface area of barium titanate with respect to the calcining temperature is large and it is difficult to stably obtain a fine one.

  For example, a method of dropping an aqueous solution of barium chloride into an aqueous solution containing a mixture of oxalic acid and titanium oxychloride while stirring vigorously at a temperature in the range of 20 to 60 ° C., and calcining the resulting precipitate has been proposed ( Patent Document 1). However, when the barium titanyl oxalate obtained by this method is used as a raw material for producing a barium titanate-based ceramic as a dielectric ceramic material, a particularly preferable range of the molar ratio of Ba to Ti (Ba / Ti) is 0.990. There exists a subject that the thing of -0.999 is hard to be obtained stably.

  In addition, the present applicant has also first prepared a first step of washing barium titanyl oxalate having an average particle size of 50 to 300 μm with water as a method for producing fine barium titanate by the oxalate method, and the barium titanyl oxalate after the washing. After forming the slurry, a wet pulverization process is performed to obtain a barium titanyl oxalate having an average particle diameter of 0.05 to 1 μm, and the barium titanyl oxalate having an average particle diameter of 0.05 to 1 μm is temporarily prepared at 700 to 1200 ° C. The method which has the 3rd process to bake was proposed (refer patent document 2).

JP 63-103827 A JP 2004-123431 A

  Furthermore, the inventors of the present invention are diligently researching a method for producing barium titanate by the oxalate method, and calcining Ti-rich barium titanyl oxalate containing Ti in excess in the molar ratio of Ti to Ba. It was found that the change in specific surface area with respect to the calcining temperature in the process of obtaining barium titanate can be kept small. Conventionally, it has been difficult to obtain a barium titanyl oxalate containing an excessive amount of Ti with a high quality and a high yield by using the oxalate method.

  Accordingly, an object of the present invention is to provide a method for industrially advantageously producing high-purity barium titanyl oxalate capable of suppressing the change in specific surface area with respect to the calcining temperature to a low level by the oxalate method. Another object of the present invention is to provide a method for producing stable quality barium titanate.

  The first invention to be provided by the present invention is the addition of an aqueous solution (solution A) containing titanium tetrachloride and barium chloride to an aqueous solution (solution B) containing oxalic acid and titanium tetrachloride, and the aging reaction is carried out at 50 ° C. or higher. It is a manufacturing method of barium titanyl oxalate characterized by performing.

  In addition, the second invention to be provided by the present invention is that an aqueous solution (solution A) containing titanium tetrachloride and barium chloride is added to an aqueous solution (solution B) containing oxalic acid and titanium tetrachloride and aged at 50 ° C. or higher. It is a method for producing barium titanate, characterized by reacting to produce barium titanyl oxalate and calcining the produced barium titanyl oxalate.

  According to the present invention, it is possible to obtain barium titanyl oxalate having a stable quality with a low change in specific surface area with respect to the calcining temperature with high purity and high yield. Moreover, barium titanate can be industrially advantageously produced by calcining the barium titanyl oxalate thus obtained.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The production method of the present invention is characterized in that an aqueous solution (solution A) containing titanium tetrachloride and barium chloride is added to an aqueous solution (solution B) containing oxalic acid and titanium tetrachloride, and the reaction is carried out. The barium titanyl oxalate produced according to the production method of the present invention preferably has a molar ratio of Ba to Ti (hereinafter referred to as “Ba / Ti molar ratio”) of less than 1.

  In the present invention, barium titanyl oxalate having a low Ba / Ti molar ratio tends to be obtained as the content of titanium tetrachloride contained in the liquid B increases. Basically, the Ba / Ti molar ratio in the reaction liquid after adding the A liquid to the B liquid is in the range of 0.85 to 1.20, preferably “the processes of (1) and (2) described later” The composition of liquid A and liquid B is determined so that the Ba / Ti molar ratio is in an excessive Ba state or an excessive Ti state, and liquid A is added to liquid B so as to satisfy the range. In particular, barium titanyl oxalate useful as a dielectric material is preferable in that it is obtained. The Ba / Ti molar ratio in the reaction liquid after the liquid A was added to the liquid B is the sum of the number of moles of Ti in the liquid A (T1) and the number of moles of Ti in the liquid B (T2). It is calculated from b / (T1 + T2) which is a relational expression with the number of moles of Ba in the middle (b).

An example of a particularly preferred embodiment for obtaining barium titanyl oxalate having a Ba / Ti molar ratio of 0.990 to 0.999 suitable as a raw material for a dielectric ceramic material as described later in the present invention is as follows. And (2).
(1) In obtaining barium titanyl oxalate having a Ba / Ti molar ratio of 0.990 to 0.999, which is useful as a raw material for the dielectric ceramic material, the composition in the B liquid is set to a specific range, This is a method for obtaining the target barium titanyl oxalate by appropriately adjusting the composition. In this case, as the solution A, an aqueous solution containing barium chloride and titanium tetrachloride, having a barium chloride content of “b” as Ba and a titanium tetrachloride content of “T1” as Ti is prepared. As B liquid, an aqueous solution containing succinic acid and titanium tetrachloride, the content of succinic acid being “s” mol, and the content of titanium tetrachloride being “T2” mol as Ti is prepared. The addition of the A liquid to the B liquid is such that the Ba / Ti molar ratio of the reaction liquid after the addition, that is, {b / (T1 + T2)} is in an excess of Ba, preferably 1.02 to 1.20, and further Ba And oxalic acid in a molar ratio (b / s) of 0.34 to 0.54 (hereinafter, abbreviated as “Production method (1)”).

(2) In obtaining barium titanyl oxalate having a Ba / Ti molar ratio of 0.990 to 0.999, which is useful as a raw material for the dielectric ceramic material, the composition in the liquid A is set to a specific range, This is a method of adjusting the composition appropriately to obtain the target barium titanyl oxalate. In this case, the addition of the liquid A to the liquid B is performed in a state where the Ba / Ti molar ratio of the reaction liquid after the addition, that is, {b / (T1 + T2)} is excessive in Ti, preferably 0.85 or more and 0.98 or less. Further, the reaction is performed such that the molar ratio (b / s) of Ba to succinic acid is 0.34 to 0.54 (hereinafter abbreviated as “production method (2)”).

  The “(1) production method” and “(2) production method” will be described in more detail. In the “production method (1)”, the blending ratio of the amount of titanium tetrachloride contained in the liquid A and the amount of titanium tetrachloride contained in the liquid B is not particularly limited. Basically, barium titanyl oxalate having a low Ba / Ti molar ratio tends to be obtained as the proportion of titanium tetrachloride contained in liquid B increases. When the Ba / Ti molar ratio in the obtained barium titanyl oxalate is from 0.990 to 0.999, the barium titanate obtained using the barium titanyl oxalate as a raw material is imparted with excellent dielectric properties as a dielectric ceramic material. Can do. From this point of view, in the present invention, it is preferable to produce barium titanyl oxalate having a Ba / Ti molar ratio within the above range. Barium titanyl oxalate having a Ba / Ti molar ratio within the above range contains 1 to 50% of reaction equivalent Ti with Ba in the B liquid, and the reaction equivalent is prepared by reacting the remainder of the reaction equivalent with the A liquid. Can be done. In the present invention, the “reaction equivalent Ti with Ba” refers to a Ba / Ti molar ratio of 1.02 to 1.20.

  In order to produce barium titanyl oxalate having a Ba / Ti molar ratio of 0.990 to 0.999, the specific composition of the A liquid is preferably 0.55 to 0.65 mol / L as the Ba as barium chloride. Titanium chloride is 0.25 to 0.60 mol / L as Ti, and the molar ratio of Ba to Ti (Ba / Ti) is preferably 1.02 to 2.30. On the other hand, the specific composition of the liquid B is 1.40 to 1.75 mol / L for oxalic acid, 0.02 to 0.40 mol / L for titanium tetrachloride as Ti, and the molar ratio of Ti to oxalic acid (Ti / Oxalic acid) is 0.01 to 0.25.

  In the “production method (1)”, the molar ratio {b / (T1 + T2)} of barium to titanium in the reaction solution after adding the solution A to the solution B is preferably 1.02 or more and 1.20 or less. What is necessary is just to add A liquid to B liquid so that the molar ratio (b / s) of oxalic acid may be 0.34-0.54, and to react on reaction conditions mentioned later. Unless otherwise specified, the symbols “b”, “T1”, “T2”, and “s” have the same meanings as described above.

  On the other hand, in “Production method (2)”, the amount of titanium tetrachloride contained in the liquid A and the amount of titanium tetrachloride contained in the liquid B are the same as barium in the reaction liquid after adding the liquid A to the liquid B. The molar ratio {b / (T1 + T2)} of titanium and titanium is not particularly limited as long as it is preferably in the range of 0.85 to 0.98. Basically, barium titanyl oxalate having a low Ba / Ti molar ratio tends to be obtained as the proportion of titanium tetrachloride contained in liquid B increases. As described above, when the Ba / Ti molar ratio in the obtained barium titanyl oxalate is 0.990 to 0.999, the barium titanate obtained using the barium titanyl oxalate as a raw material has excellent dielectric properties as a dielectric ceramic material. Can be granted. From this viewpoint, it is preferable to generate barium titanyl oxalate having a Ba / Ti molar ratio in the above range. In order to obtain barium titanyl oxalate having such a molar ratio of Ba and Ti, the composition of the liquid A and the liquid B can be arbitrarily set in the “production method (2)”. Considering the simplicity and operability of the composition preparation, as liquid B, titanium tetrachloride is 0.01 to 0.20 mol / L as Ti, oxalic acid is 1.50 to 1.75 mol / L, Ti and oxalic acid It is preferable to use that having a molar ratio (Ti / oxalic acid) of 0.01 to 0.15 and to contain the Ti necessary for preparing the composition in the liquid A. Usually, the specific composition of the liquid A is 0.55-0.65 mol / L as barium chloride as Ba, and 0.45-0.65 mol / L as titanium tetrachloride as Ti, and the moles of Ba and Ti. The ratio (Ba / Ti) is preferably adjusted to 1.02 to 1.20.

  Next, in the “production method (2)”, the molar ratio {b / (T1 + T2)} of barium to titanium in the reaction solution after adding the solution A to the solution B is preferably 0.85 or more and 0.98 or less. Solution A may be added to Solution B so that the molar ratio of oxalic acid to oxalic acid (b / s) is 0.34 to 0.54, and the reaction may be performed under the reaction conditions described below. Among the “production methods (1) and (2)”, in the present invention, the “production method (1)” is particularly advantageously used industrially because the Ti reaction rate is particularly high.

  In the “production methods (1) and (2)”, it is preferable to add the A liquid to the B liquid with stirring. The stirring speed is not particularly limited as long as the slurry containing barium titanyl oxalate generated between the start of addition and the end of the reaction always exhibits fluidity.

  In the “production method of (1) and (2)”, the reaction is such that the average particle diameter of the barium titanyl oxalate particles produced is in the range of 100 to 300 μm, preferably 100 to 200 μm, more preferably 100 to 150 μm. It is preferable to set the conditions as described above. Barium titanyl oxalate having an average particle size in the above range has an advantage that there is little elution of Ba and Ti when washed with water due to the large crystal grains. In addition, there is an advantage that impurities such as chlorine can be efficiently removed. Barium titanyl oxalate having an average particle size of less than 100 μm is difficult to reduce impurities such as chlorine incorporated in the particles to 150 ppm or less even when washed with water. In addition, the composition tends to vary due to the elution of Ba and Ti. Barium titanyl oxalate having an average particle diameter exceeding 300 μm tends to be difficult to disintegrate to the primary diameter in the subsequent calcination and pulverization steps, and the variation in particle diameter tends to increase. In the present invention, the average particle diameter of barium titanyl oxalate refers to a value measured with a laser diffraction / scattering particle size distribution analyzer.

  In the present invention, in the “production methods (1) and (2)”, it is preferable to set each reaction condition so that barium titanyl oxalate having an average particle diameter within the above range is generated. Specifically, in “the production method of (1) and (2)”, oxalic acid produced by increasing the addition time of the liquid A continuously or intermittently supplied to the reaction system or by increasing the addition temperature. The particle size of barium titanyl can be increased. From this point of view, it is preferable that the liquid B is heated in advance until it is usually 50 to 90 ° C., preferably 55 to 70 ° C. Moreover, when the addition time of the A liquid to the B liquid is preferably 0.5 to 5 hours, more preferably 1 to 4 hours, and continuously performed at a constant rate, Ti and Ba in the barium titanyl oxalate obtained are obtained. The variation in the molar ratio is reduced, and the product has a stable quality. Furthermore, highly purified barium titanyl oxalate having an average particle diameter in the above range can be obtained in a short time by performing an aging reaction described later. The temperature of the liquid A is not particularly limited, but it is preferable that the temperature is within the same range as the heating temperature of the liquid B because the reaction operation becomes easy.

  The reaction is continued after the addition of the liquid A (hereinafter referred to as “ripening reaction”). In the present invention, it is also an important requirement to perform this aging reaction at 50 ° C. or higher. That is, when the aging reaction is performed at 50 ° C. or more, the grain growth of the barium titanyl oxalate produced is suppressed and the reaction is completed, so that the average particle size is within the above range, the chlorine content is 150 ppm or less, Ti Desired barium titanyl oxalate with little variation in the molar ratio of Ba to Ba can be obtained.

  The aging conditions are such that the aging temperature is usually 50 ° C. or higher, preferably 50 to 90 ° C., more preferably 55 to 70 ° C. The aging temperature refers to the temperature of the entire reaction solution after addition of solution A. The aging time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours.

  After completion of aging, the solid and liquid are separated by a conventional method and then washed with water. The cleaning method is not particularly limited. Washing with repulp or the like is preferable because the washing efficiency is good. It is then dried and ground if necessary to obtain barium titanyl oxalate.

  As a preferable physical property of the barium titanyl oxalate thus obtained, the average particle size is 100 to 300 μm, preferably 100 to 200 μm, more preferably 100 to 150 μm. The composition of the barium titanyl oxalate is such that the molar ratio of Ba to Ti (Ba / Ti) is less than 1, preferably 0.990 to 0.999.

  Barium titanyl oxalate obtained by the production method of the present invention can be suitably used as a production raw material for a barium titanate-based ceramic of a dielectric ceramic material. The manufacturing method of the barium titanate of this invention is as follows.

  The method for producing barium titanate according to the present invention is characterized in that barium titanyl oxalate obtained by the above-described method is calcined. In the present invention, if necessary, the barium titanyl oxalate is pulverized by a wet method such as a ball mill or a bead mill before the calcination for the purpose of obtaining finer barium titanate, and the average particle size is preferably set to 0. You may grind | pulverize until it becomes 01-1 micrometer, More preferably, it is 0.05-0.8 micrometer. As the solvent used in the wet pulverization treatment, a solvent inert to barium titanyl oxalate is used. For example, water, methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methylene chloride, ethyl acetate, dimethylformamide, diethyl ether and the like can be mentioned. Of these, organic solvents such as methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methylene chloride, ethyl acetate, dimethylformamide, diethyl ether, etc., and those with low elution of Ba and Ti, A high perovskite type barium titanate can be obtained, which is preferable. It is particularly preferable to use ethanol because barium titanate having excellent crystallinity can be produced at a low temperature of about 800 to 950 ° C. at low cost.

  Organic substances derived from oxalic acid contained in the final product are not preferable because they impair the dielectric properties of the material and cause unstable behavior in the thermal process for ceramization. Therefore, in the present invention, it is necessary to thermally decompose barium titanyl oxalate by calcination to obtain the target barium titanate, and to sufficiently remove organic substances derived from oxalic acid. The calcination conditions are such that the calcination temperature is preferably 600 to 1200 ° C, more preferably 800 to 1100 ° C. When the calcining temperature is less than 600 ° C., it is difficult to obtain single-phase barium titanate. On the other hand, when the calcining temperature exceeds 1200 ° C., the variation in the particle size increases. The calcination time is preferably 2 to 30 hours, more preferably 5 to 20 hours. The atmosphere of calcination is not particularly limited, and may be either in the air or in an inert gas atmosphere.

  Calcination may be performed as many times as desired. Alternatively, for the purpose of making the powder characteristics uniform, the temporarily calcined material may be pulverized and then re-calcined.

After calcination, the product is appropriately cooled and pulverized as necessary to obtain barium titanate powder. The pulverization performed as necessary is appropriately performed when the barium titanate obtained by calcination is in a brittle block shape, and the barium titanate particles themselves have the following specific average particle diameter and BET specific surface area. It is what has. That is, the barium titanate powder obtained above preferably has an average particle size determined from a scanning electron micrograph (SEM) of 0.05 to 5 μm, more preferably 0.1 to 2 μm. The BET specific surface area is preferably 1 to 20 m ² / g, more preferably ² to 15 m ² / g. Furthermore, the composition of barium titanate obtained by the production method of the present invention is preferably such that the molar ratio of Ba to Ti (Ba / Ti) is less than 1, particularly 0.990 to 0.999.

  The barium titanate obtained by the production method of the present invention can contain a subcomponent element by adding a subcomponent element-containing compound to the barium titanate for the purpose of adjusting dielectric characteristics and temperature characteristics as necessary. Examples of the subcomponent element-containing compound that can be used include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu rare earth elements. At least one selected from the group consisting of Ba, Li, Bi, Zn, Mn, Al, Si, Ca, Sr, Co, Ni, Cr, Fe, Mg, Ti, V, Nb, Mo, W and Sn Elemental compounds may be mentioned.

  The subcomponent element-containing compound may be either inorganic or organic. Examples thereof include oxides, hydroxides, chlorides, nitrates, oxalates, carboxylates and alkoxides containing the above elements. When the subcomponent element-containing compound is a compound containing Si element, silica sol, sodium silicate, or the like can be used in addition to the oxide. The subcomponent element-containing compounds can be used alone or in combination of two or more. What is necessary is just to perform the combination of the addition amount and an addition compound according to a conventional method.

  In order to contain the subcomponent element in the barium titanate, for example, the barium titanate and the subcomponent element-containing compound may be uniformly mixed and then fired. Alternatively, barium titanyl oxalate and the subcomponent element-containing compound may be uniformly mixed and then calcined.

  For example, when manufacturing a multilayer ceramic capacitor using the barium titanate obtained in accordance with the present invention, first, the barium titanate powder is mixed with a conventionally known additive, organic binder, plastic, A sheet is formed by mixing and dispersing in a suitable solvent together with a compounding agent such as an agent and a dispersant to form a slurry. Thereby, the ceramic sheet used for manufacture of a multilayer ceramic capacitor is obtained. In order to produce a multilayer ceramic capacitor from the ceramic sheet, first, an internal electrode forming conductive paste is printed on one surface of the ceramic sheet. After drying, a plurality of the ceramic sheets are laminated and pressed in the thickness direction to obtain a laminated body. Next, this laminate is heat treated to remove the binder, and fired to obtain a fired body. Further, a Ni capacitor, an Ag paste, a nickel alloy paste, a copper paste, a copper alloy paste or the like is applied to the fired body and baked to obtain a multilayer capacitor.

  In addition, when the barium titanate powder obtained according to the present invention is blended with a resin such as an epoxy resin, a polyester resin, or a polyimide resin to form a resin sheet, a resin film, an adhesive, or the like, a printed wiring board or a multilayer print It can be used as a material such as a wiring board, a co-material for suppressing the shrinkage difference between the internal electrode and the dielectric layer, an electrode ceramic circuit board, a glass ceramic circuit board, a circuit peripheral material, and a dielectric material for inorganic EL. .

  In addition, the barium titanate obtained according to the present invention can be suitably used as a catalyst used in reactions such as exhaust gas removal and chemical synthesis, and as a surface modifier for printing toner that imparts antistatic and cleaning effects. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

[Examples 1-5 and Comparative Examples 1-3: Production of barium titanyl oxalate]
Liquid A and liquid B having the compositions shown in Table 1 were prepared using barium chloride dihydrate, titanium tetrachloride aqueous solution, oxalic acid dihydrate and pure water. Next, the liquid B was kept warm at 60 ° C., and the liquid A was added to the liquid B with stirring at room temperature (25 ° C.) over 120 minutes. The addition amount is as shown in Table 1. The molar ratio of Ti, Ba, and oxalate ions in the reaction solution after completion of addition is as shown in Table 2. After completion of the addition, the mixture was further aged with stirring at 60 ° C. for 1 hour. After cooling, it was filtered to recover barium titanyl oxalate.

[Comparative Example 4: Production of barium titanyl oxalate]
Liquid A and liquid B having the compositions shown in Table 1 were prepared using barium chloride dihydrate, titanium tetrachloride aqueous solution, oxalic acid dihydrate and pure water. Next, the liquid B was kept warm at 30 ° C., and the liquid A was added to the liquid B with stirring at room temperature (25 ° C.) over 120 minutes. The addition amount is as shown in Table 1. The molar ratio of Ti, Ba, and oxalate ions in the reaction solution after completion of addition is as shown in Table 2. After completion of the addition, the mixture was further aged with stirring at 30 ° C. for 1 hour. After cooling, it was filtered to recover barium titanyl oxalate.

  The recovered barium titanyl oxalate was then repulped with pure water and washed carefully. Thereafter, it was dried at 105 ° C. for 2 hours to obtain barium titanyl oxalate powder. Table 3 shows the physical properties of the obtained barium titanyl oxalate. The molar ratio of Ba and Ti was measured by fluorescent X-ray. The average particle size was measured with a laser diffraction / scattering particle size distribution analyzer. The chlorine content was measured by ion chromatography. Moreover, the reaction rate of Ba and Ti was calculated | required, and the result was written together in Table 3. The reaction rate is measured by ICP for Ba and Ti eluting at the end of the reaction, and the elution amount is defined as the unreacted content. The reaction amount is obtained by subtracting the unreacted content from the charged amount. It is a representation. The higher the reaction rate, the less the unreacted Ba and Ti components, and the higher the reaction efficiency and yield.

  From the results in Table 3, it can be seen that the barium titanyl oxalate obtained using the production method of the present invention has a Ba / Ti molar ratio of 0.990 to 0.999. As described above, barium titanyl oxalate having a Ba / Ti molar ratio of 0.990 to 0.999 is preferable as a raw material for barium titanate useful as a dielectric material. On the other hand, barium titanyl oxalate of Comparative Example 2 in which the required amount of Ti was previously charged into the B solution and reacted, or oxalic acid of Comparative Example 1 in which the required amount of Ti was charged in the A solution and reacted. It can be seen that barium titanyl does not have a Ba / Ti molar ratio of 0.990 to 0.999. Furthermore, it can be seen that in Comparative Example 3, the reaction rate of Ti is lowered. Moreover, it turns out that chlorine content is increasing in the comparative example 4 which made the aging temperature 30 degreeC.

[Examples 6 to 10 and Comparative Examples 5 to 6: Production of barium titanate]
5 g of the barium titanyl oxalate sample obtained in Examples 1 to 6 and Comparative Examples 1 and 4 was calcined in the air at 800 ° C. for 5 hours or 1000 ° C. for 5 hours. After cooling, it was crushed to obtain barium titanate powder. Various physical properties of the obtained barium titanate are shown in Table 4. The molar ratio of Ba and Ti and the average particle diameter were determined by the same method as described above. The specific surface area was determined by the BET method.

From the results of Table 4, barium titanate (Comparative Examples 5 to 6) using barium titanyl oxalate (Comparative Examples 1 and 4) without using the production method according to the present invention has a large change in specific surface area with respect to the calcining temperature. I understand that In contrast, barium titanate (Examples 6 to 10) using barium titanyl oxalate (Examples 1 to 5) using the production method according to the present invention has a low specific surface area change with respect to the calcining temperature. It can be seen that barium titanate having a stable specific surface area can be produced.

Claims (6)

  A method for producing barium titanyl oxalate, comprising adding an aqueous solution (solution A) containing titanium tetrachloride and barium chloride to an aqueous solution (solution B) containing oxalic acid and titanium tetrachloride and performing an aging reaction at 50 ° C or higher.   The method for producing barium titanyl oxalate according to claim 1, wherein the reaction is carried out until the average particle size of barium titanyl oxalate particles produced by the reaction is in the range of 100 to 300 µm.   The liquid A is added to the liquid B so that the molar ratio (Ba / Ti) of Ti and Ba in the reaction liquid after the addition is finished is 0.85 to 0.98 or 1.02 to 1.20. The method for producing barium titanyl oxalate according to claim 1 or 2.   Barium titanyl oxalate produced by the process of claim 1.   The barium titanyl oxalate according to claim 4, wherein the molar ratio of Ba to Ti (Ba / Ti) is 0.990 to 0.999. An aqueous solution containing Titanium Tetrachloride and Barium Chloride (Liquid A) is added to an aqueous solution containing Oxalic Acid and Titanium Tetrachloride (Liquid B) and aged at 50 ° C. to produce barium titanyl oxalate. A method for producing barium titanate, characterized by calcining the material.