JP4638767B2 - Method for producing barium titanyl oxalate and method for producing barium titanate - Google Patents

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 barium titanyl oxalate containing an excess of Ti with stable quality and high yield using the oxalate method.

  Accordingly, an object of the present invention is to provide a method for industrially advantageously producing barium titanyl oxalate, which can suppress a change in specific surface area with respect to the calcining temperature, by the oxalate method. Another object of the present invention is to provide a method for producing stable quality barium titanate.

A first invention to be provided by the present invention is characterized in that an aqueous solution (liquid A) containing titanium tetrachloride and barium chloride is added to an aqueous solution (liquid B) prepared from oxalic acid and hydrochloric acid, and the reaction is performed. This is a method for producing barium titanyl oxalate.

In addition, the second 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) prepared from oxalic acid and hydrochloric acid to carry out a reaction to produce barium oxalate. A method for producing barium titanate, characterized in that titanyl is produced and the produced barium titanyl oxalate is calcined.

  According to the present invention, it is possible to obtain barium titanyl oxalate having a low change in specific surface area with respect to the calcining temperature with a stable quality and a 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 at least oxalate ions and chloride ions to carry out the reaction. . 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.

  The liquid A used in the present invention is an aqueous solution containing titanium tetrachloride and barium chloride. In the liquid A, oxalic acid produced when the molar ratio (Ba / Ti) of Ba in barium chloride to Ti in titanium tetrachloride is 1.0 to 1.5, particularly 1.05 to 1.20. Since the composition of barium titanyl becomes stable, it is preferable. In the liquid A, the concentration of barium chloride is 0.5 to 0.7 mol / L as Ba, particularly 0.55 to 0.65 mol / L, and the concentration of titanium tetrachloride is 0.4 as Ti. -0.7 mol / L, especially 0.45-0.65 mol / L is preferred because barium titanyl oxalate is obtained in high yield.

One liquid B is an aqueous solution containing oxalate ions and chloride ions. In the conventional oxalate method, hydrochloric acid is by-produced by the reaction between titanium tetrachloride or barium chloride and oxalic acid, and hydrochloric acid is gradually contained in the reaction solution. On the other hand, in the present invention, in addition to the by-produced hydrochloric acid, a solution obtained by adding hydrochloric acid , which is a compound serving as a chloride ion source, to the liquid B in advance is used.

Hydrochloric acid is used as the chloride ion source that can be used. Sodium chloride was added to the hydrochloric acid, potassium chloride, lithium chloride, the organic compounds containing chloride ions, can be used singly or in combination.

  The amount of chloride ions contained in the liquid B is preferably greater than 0 and 30 or less, and more preferably 0.3 to 3.5, in terms of a molar ratio to oxalate ions. As the amount of chloride ions contained in the liquid B increases, the Ba / Ti molar ratio in the barium titanyl oxalate obtained by the reaction tends to decrease. However, if even a small amount of chloride ions are present, Ba / Ti Barium titanyl oxalate having a molar ratio of less than 1 can be obtained. Therefore, from the viewpoint of obtaining barium titanyl oxalate having a Ba / Ti molar ratio of less than 1, the lower limit value of the chloride ions contained in the liquid B may be larger than 0 in terms of the molar ratio to the oxalate ions. On the other hand, when the amount of chloride ions exceeds 30 in terms of molar ratio to oxalate ions, the Ba / Ti molar ratio in the generated barium titanyl oxalate can be used at least as a raw material for producing dielectric ceramic materials. It becomes smaller than a certain 0.9. In addition, when the Ba / Ti molar ratio in the generated barium titanyl oxalate is preferably 0.990 to 0.999, the barium titanate using the barium titanyl oxalate as a raw material has excellent dielectric properties as a dielectric ceramic material. Properties can be imparted. From this viewpoint, in the present invention, it is preferable to produce barium titanyl oxalate having a Ba / Ti molar ratio in the above range. For this purpose, the content of chloride ions in the B liquid is particularly preferably 0.3 to 3.5 in terms of molar ratio to oxalate ions.

  The specific composition of solution B is that the oxalate ion concentration is 0.2 to 2 mol / L, particularly 1.05 to 1.65 mol / L, and the chloride ion concentration is 0.1 to 8 mol / L. In particular, 0.5 to 3.7 mol / L is preferable because barium titanyl oxalate having a stable composition can be obtained in a high yield.

  When the addition of solution A to solution B was performed such that the molar ratio of barium to oxalic acid in the reaction solution after addition was 0.3 to 0.6, particularly 0.34 to 0.54, the composition was stable. Since barium titanyl oxalate is obtained in high yield, it is preferable.

  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 reaction, it is preferable to set conditions so that the average particle diameter of the generated barium titanyl oxalate particles is in the range of 20 to 300 μm, particularly in the range of 50 to 200 μm. 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 20 μm is difficult to reduce impurities such as chlorine incorporated into the particles to several hundred ppm level 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, 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, the particle size of the barium titanyl oxalate produced can be increased by increasing the addition time of the liquid A supplied continuously or intermittently to the reaction system or by increasing the addition temperature. From this point of view, it is preferable that the liquid B is preliminarily heated up to usually 50 to 90 ° C., preferably 50 to 70 ° C. in advance. 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”). When this ripening reaction is performed, the grain growth of the barium titanyl oxalate produced is suppressed and the reaction is completed, so that the desired oxalic acid having an average particle diameter within the above range and less variation in the molar ratio of Ti and Ba. Barium titanyl can be obtained.

  The aging condition is that the aging temperature is usually 50 ° C. or higher, preferably 50 to 90 ° 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.

  The preferred physical properties of the barium titanyl oxalate thus obtained have an average particle size of 20 to 300 μm, particularly 50 to 200 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 1-2 and Comparative Examples 1-2: 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, hydrochloric acid, and pure water.
Next, the liquid B was heated to 60 ° C., and the liquid A was added to the liquid B with stirring at room temperature (25 ° C.) over 120 minutes. The amount added is as shown in Table 1. Table 2 shows the molar ratios of Ti, Ba, oxalate ions, and chloride ions in the reaction solution after completion of the addition. 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.

  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 of Table 3, it can be seen that according to the production method of the present invention, barium titanyl oxalate having a Ba / Ti molar ratio in a range particularly useful as a dielectric material can be obtained with a high reaction rate and a high yield. On the other hand, in Comparative Example 1, the Ba / Ti molar ratio in barium titanyl oxalate was 1. In Comparative Example 2, the Ba / Ti molar ratio in barium titanyl oxalate was less than 1, but a high reaction rate and high yield could not be achieved.

[Examples 3 to 4 and Comparative Example 3: Production of Barium Titanate]
5 g of the barium titanyl oxalate sample obtained in Examples 1-2 and Comparative Example 1 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, it can be seen that barium titanate (Comparative Example 3) using barium titanyl oxalate (Comparative Example 1) having a Ba / Ti molar ratio of 1 has a large change in specific surface area with respect to the calcining temperature. I understand. On the other hand, barium titanate (Examples 3 to 4) using barium titanyl oxalate (Examples 1 and 2) of the present invention as a raw material has a low change in specific surface area relative to the calcining temperature.

Claims (4)

A method for producing barium titanyl oxalate, which comprises reacting an aqueous solution (solution A) containing titanium tetrachloride and barium chloride with an aqueous solution ( solution B) prepared from oxalic acid and hydrochloric acid .   2. The method for producing barium titanyl oxalate according to claim 1, wherein the content of chloride ions in the liquid B is greater than 0 and 30 or less in molar ratio to oxalate ions. The method for producing barium titanyl oxalate according to claim 1 or 2 , wherein the reaction is carried out until the average particle diameter of barium titanyl oxalate particles produced by the reaction is in the range of 20 to 300 µm. Adding an aqueous solution (liquid A) containing titanium tetrachloride and barium chloride to an aqueous solution (liquid B) prepared from oxalic acid and hydrochloric acid to produce barium titanyl oxalate, and calcining the generated barium titanyl oxalate A process for producing barium titanate, characterized in that