JP2010202610A - Method for producing barium titanyl oxalate and method for producing barium titanate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide barium titanyl oxalate small in variation of Ba/Ti molar ratio overall particle sizes, and to provide a highly crystalline barium titanate. <P>SOLUTION: This method for producing barium titanyl oxalate includes the following process: a reaction vessel is fed with an aqueous solution (A1-liquid) obtained by mixing oxalic acid and titanium tetrachloride into water, and an aqueous barium chloride solution (B1-liquid); concurrently, while the resultant reaction liquid is discharged from the reaction vessel, and the reaction of forming the objective barium titanyl oxalate is conducted. <P>COPYRIGHT: (C)2010,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. is there.

  Conventionally, barium titanate is produced by a solid phase method, a hydrothermal synthesis method, an alkoxide method, an oxalate method, or the like.

  In the solid phase method, constituent raw material powders and the like are mixed, and the mixture is manufactured by a dry method in which the mixture is heated at a high temperature. Therefore, the obtained powder forms an agglomerate having an irregular shape and has desired characteristics. High temperature firing is necessary to achieve. In addition, the hydrothermal synthesis method has a complicated synthesis process in spite of the advantages of good powder characteristics, and is inferior in productivity because of the use of an autoclave, and the production powder is expensive and not industrially advantageous. Similarly, the alkoxide method is difficult to handle starting materials, is expensive, and is not industrially advantageous.

Barium titanate obtained by the oxalate method can be manufactured at a low cost compared with hydrothermal synthesis method or alkoxide method, and compared with barium titanate manufactured by solid phase method, It has the feature that the composition is uniform. As a conventional oxalate method, an aqueous solution of TiCl ₄ and BaCl ₂ is dropped into an H ₂ C ₂ O ₄ aqueous solution while stirring to obtain barium titanyl oxalate, and the barium titanyl oxalate is baked. Is common (see, for example, Non-Patent Document 1 and Patent Document 1).

JP 2005-500239 A

W. S. Clavaugh et al. , J .; Res. Nat. Bur. Stand. , 56 (5), 289-291 (1956)

  Although barium titanate obtained by the oxalate method exhibits excellent performance as a dielectric ceramic material, further improvement in performance is required due to the recent increase in required performance. It is known that the characteristic of barium titanate as a dielectric ceramic is generally high in crystallinity and has good dielectric characteristics (see, for example, JP-A-2006-117446). In addition, the oxalate method has a problem that it is difficult to obtain a small particle size, and even if it is obtained, it is difficult to obtain a high crystallinity.

  Therefore, the present inventors examined barium titanyl oxalate obtained by a conventional method, and these barium titanyl oxalates had a bulk Ba / Ti molar ratio of about 0.998 to 1.002. Although there is variation in the Ba / Ti molar ratio for each particle size, the smaller the particle size (in other words, the larger the specific surface area), the smaller the Ba / Ti molar ratio, while the particle size is It was found that the larger the ratio (in other words, the smaller the specific surface area), the larger the Ba / Ti molar ratio.

  And if the present inventors use barium titanyl oxalate with small variations in the Ba / Ti molar ratio over the entire particle size, it is possible to produce barium titanate having higher performance and higher crystallinity. I guessed.

  Accordingly, an object of the present invention is to provide barium titanyl oxalate having a small variation in the Ba / Ti molar ratio over the entire particle size. Furthermore, this invention is providing the barium titanate excellent in crystallinity.

  As a result of intensive studies in view of the above circumstances, the present inventors have conducted (1) a reaction while supplying a reaction raw material aqueous solution of barium titanyl oxalate to the reaction vessel and discharging the reaction solution from the reaction vessel. This makes it possible to obtain barium titanyl oxalate with little variation in the Ba / Ti molar ratio over the entire particle size, and (2) the particle size is small by using the barium titanyl oxalate thus obtained. Nevertheless, since barium titanate having high crystallinity can be obtained, it has been found that a dielectric ceramic material having excellent performance can be provided. Furthermore, the conventional barium titanate obtained by calcining barium titanyl oxalate is easily obtained as a tarako-shaped bulk as a result of the particles being joined together by sintering or the like after firing. According to the present invention, since each particle is easily obtained in a dispersed shape, it has been found that the particles are excellent in dispersibility with fewer coarse particles bonded by sintering than the conventional particles, and the present invention is completed. It came to let you.

  That is, in the present invention (1), while supplying an aqueous solution (A1 solution) obtained by mixing oxalic acid and titanium tetrachloride with water and an aqueous barium chloride solution (B1 solution) to the reaction vessel, the reaction solution is added to the reaction vessel. The present invention provides a method for producing barium titanyl oxalate, wherein the production reaction of barium titanyl oxalate is performed while discharging from the reaction vessel.

  In the present invention (2), an oxalic acid aqueous solution (A2 solution) and an aqueous solution (B2 solution) obtained by mixing titanium tetrachloride and barium chloride with water are supplied to the reaction vessel while the reaction solution is supplied. The present invention provides a method for producing barium titanyl oxalate, characterized by carrying out a reaction for producing barium titanyl oxalate while discharging from the reaction vessel.

  Moreover, this invention (3) supplies the reaction container with the oxalic acid aqueous solution (A3 liquid), the barium chloride aqueous solution (B3 liquid), and the aqueous solution (C3 liquid) obtained by mixing titanium tetrachloride with water. However, the present invention provides a method for producing barium titanyl oxalate characterized in that a reaction for producing barium titanyl oxalate is carried out while discharging the reaction solution from the reaction vessel.

  In addition, the present invention (4) is characterized by calcining barium titanyl oxalate obtained by performing the method for producing barium titanyl oxalate according to any one of the present inventions (1) to (3). A manufacturing method is provided.

  According to the present invention, it is possible to provide barium titanyl oxalate having a small variation in the Ba / Ti molar ratio over the entire particle diameter. By using such barium titanyl oxalate, a dielectric ceramic material having high crystallinity and excellent performance can be provided.

It is typical sectional drawing of the reaction container of an overflow system. It is a typical graph which shows the particle size of barium titanyl oxalate, and the relationship of Ba / Ti molar ratio. 2 is a SEM photograph of barium titanate obtained in Example 1. 2 is a SEM photograph of barium titanate obtained in Example 2. 4 is a SEM photograph of barium titanate obtained in Example 3. 2 is a SEM photograph of barium titanate obtained in Comparative Example 1.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
Method for producing a barium titanyl oxalate of the present invention include oxalic acid _{(H 2} C _{2 O} 4) and the reaction raw material of the production reaction of barium titanyl oxalate, barium chloride (BaCl ₂₎ and titanium tetrachloride (TiCl ₄₎ This is a method for producing barium titanyl oxalate, in which an aqueous solution is supplied to a reaction vessel and a reaction solution is discharged from the reaction vessel while a barium titanyl oxalate production reaction is performed. And the manufacturing method of the barium titanyl oxalate of this invention has the following forms according to the kind of reaction raw material aqueous solution.

  In the present invention, the reaction liquid is a liquid in a reaction vessel to which an aqueous reaction raw material solution is supplied, and is a liquid in which a barium titanyl oxalate production reaction occurs, and a precipitate of the generated barium titanyl oxalate. It is a liquid containing.

  The method for producing barium titanyl oxalate according to the first aspect of the present invention comprises a reaction vessel comprising an aqueous solution (A1 solution) obtained by mixing oxalic acid and titanium tetrachloride with water and an aqueous barium chloride solution (B1 solution). The barium titanyl oxalate production method in which barium titanyl oxalate is generated while the reaction solution is discharged from the reaction vessel while being supplied to the reactor.

  The method for producing barium titanyl oxalate according to the second aspect of the present invention comprises an aqueous oxalic acid solution (A2 solution) and an aqueous solution (B2 solution) obtained by mixing titanium tetrachloride and barium chloride with water. The barium titanyl oxalate production method in which barium titanyl oxalate is generated while the reaction solution is discharged from the reaction vessel while being supplied to the reactor.

  The method for producing barium titanyl oxalate according to the third aspect of the present invention is an aqueous solution (C3 solution) obtained by mixing an aqueous oxalic acid solution (A3 solution), an aqueous barium chloride solution (B3 solution), and titanium tetrachloride with water. And barium titanyl oxalate for producing barium titanyl oxalate while discharging the reaction solution from the reaction vessel.

  That is, in the method for producing barium titanyl oxalate according to the first aspect of the present invention, an aqueous solution (A1 solution) obtained by mixing oxalic acid and titanium tetrachloride with water as an aqueous reaction raw material solution, and an aqueous barium chloride solution (B1). Liquid).

  The A1 liquid according to the method for producing barium titanyl oxalate according to the first aspect of the present invention is an aqueous solution obtained by mixing oxalic acid and titanium tetrachloride with water. For example, first, titanium tetrachloride is mixed with water. Then, oxalic acid is mixed with the obtained aqueous solution, or titanium tetrachloride is mixed with the oxalic acid aqueous solution. The molar ratio of oxalate ions to Ti elements in the A1 solution (number of moles of oxalate ions / number of moles of Ti elements) is 2.0 to 3.8, preferably 2.8 to 3.8, more preferably It is 3.0-3.3. When the molar ratio of the oxalate ion to the Ti element in the A1 solution is in the above range, approximately 1 barium titanate having a Ba / Ti molar ratio of 0.998 to 1.002 can be easily obtained. The concentration of Ti element in the A1 solution is not particularly limited, but is preferably 0.04 to 3.0 mol / L, particularly preferably 0.2 to 0.6 mol / L. The concentration of oxalate ions in the A1 solution is not particularly limited, but is preferably 0.1 to 7.0 mol / L, particularly preferably 0.6 to 1.4 mol / L.

  B1 liquid which concerns on the manufacturing method of the barium titanyl oxalate of the 1st form of this invention is barium chloride aqueous solution. The concentration of the Ba element in the B1 solution is not particularly limited, but is preferably 0.1 to 6.5 mol / L, and particularly preferably 0.5 to 1.3 mol / L.

  In the method for producing barium titanyl oxalate according to the first aspect of the present invention, the production reaction of barium titanyl oxalate is performed in the reaction vessel by supplying the A1 solution and the B1 solution to the reaction vessel.

  At this time, the ratio of the Ba element supply rate to the Ti element supply rate to the reaction vessel (Ba element supply rate / Ti element supply rate) is 0.5 to 3.0, preferably 1.0 to 1. .5. When the ratio of the supply rate of Ba element to the supply rate of Ti element to the reaction vessel is in the above range, approximately 1 barium titanate having a Ba / Ti molar ratio of 0.998 to 1.002 can be obtained. it can.

  In the method for producing barium titanyl oxalate according to the first aspect of the present invention, the concentration of Ti element in the A1 solution, the concentration of Ba element in the B1 solution, the supply rate of the A1 solution (L / hour), and the supply of the B1 solution By appropriately selecting the rate (L / hour), the ratio of the supply rate of Ba element to the supply rate of Ti element to the reaction vessel can be adjusted.

  In the present invention, the supply rate of Ti element to the reaction vessel refers to the number of moles of Ti element supplied per unit time (mol / hour), and the supply rate of Ba element refers to the supply rate per unit time. The Ba element supply mole number (mole / hour) is referred to, and the oxalate ion supply rate refers to the oxalate ion supply mole number per unit time (mole / hour).

  And in the manufacturing method of the barium titanyl oxalate of the 1st form of this invention, reaction liquid containing the deposit of barium titanyl oxalate produced | generated within reaction container, supplying A1 liquid and B1 liquid to reaction container Is discharged from the reaction vessel. At this time, it is preferable that the total amount of the A1 liquid and the B1 liquid supplied to the reaction container and the amount of the reaction liquid discharged from the reaction container are the same in that stable reaction can be performed. For example, while supplying A1 liquid to the reaction container at a supply rate of a1 (L / hour) and B1 liquid at a supply speed of b1 (L / hour), the reaction liquid is discharged from the reaction container at a1 + b1 (L / hour). Is preferably discharged.

  Moreover, the manufacturing method of the barium titanyl oxalate of the 2nd form of this invention is aqueous solution (B2) obtained by mixing oxalic acid aqueous solution (A2 liquid), titanium tetrachloride, and barium chloride with water as reaction raw material aqueous solution. Liquid).

  The A2 liquid which concerns on the manufacturing method of the barium titanyl oxalate of the 2nd form of this invention is oxalic acid aqueous solution. The concentration of oxalate ions in the A2 solution is not particularly limited, but is preferably 0.1 to 7.0 mol / L, particularly preferably 0.6 to 1.4 mol / L.

  The B2 liquid according to the method for producing barium titanyl oxalate according to the second aspect of the present invention is an aqueous solution obtained by mixing titanium tetrachloride and barium chloride with water. For example, first, titanium tetrachloride is mixed with water. Then, it is prepared by mixing barium chloride with the obtained aqueous solution or mixing titanium tetrachloride with the barium chloride aqueous solution. The molar ratio of Ba element to Ti element in the B2 liquid (number of moles of Ba element / number of moles of Ti element) is 0.5 to 3.0, preferably 1.0 to 1.5. When the molar ratio of the Ba element to the Ti element in the B2 liquid is in the above range, approximately 1 barium titanate having a Ba / Ti molar ratio of 0.998 to 1.002 can be obtained. Further, the concentration of Ti element in the B2 liquid is not particularly limited, but is preferably 0.04 to 4.0 mol / L, particularly preferably 0.2 to 0.8 mol / L. The concentration of the Ba element in the B2 solution is not particularly limited, but is preferably 0.08 to 6.5 mol / L, particularly preferably 0.4 to 1.3 mol / L.

  In the method for producing barium titanyl oxalate according to the second aspect of the present invention, the production reaction of barium titanyl oxalate is performed in the reaction vessel by supplying the A2 solution and the B2 solution to the reaction vessel.

  At this time, the ratio of the oxalate ion supply rate to the Ti element supply rate to the reaction vessel (oxalate ion supply rate / Ti element supply rate) is 2.0 to 3.8, preferably 2.8. ˜3.8, particularly preferably 3.0 to 3.3. When the ratio of the supply rate of oxalate ions to the supply rate of Ti element to the reaction vessel is in the above range, approximately 1 barium titanate having a Ba / Ti molar ratio of 0.998 to 1.002 is obtained. Can do.

  In the method for producing barium titanyl oxalate according to the second aspect of the present invention, the concentration of oxalate ions in the A2 solution, the concentration of Ti element in the B2 solution, the supply rate (L / hour) of the A2 solution, and the B2 solution By appropriately selecting the supply rate (L / hour), the ratio of the supply rate of oxalate ions to the supply rate of Ti element to the reaction vessel can be adjusted.

  And in the manufacturing method of the barium titanyl oxalate of the 2nd form of this invention, reaction liquid containing the precipitate of barium titanyl oxalate produced | generated within reaction container, supplying A2 liquid and B2 liquid to reaction container Is discharged from the reaction vessel. At this time, it is preferable that the total amount of the liquid A2 and the liquid B2 supplied to the reaction vessel and the amount of the reaction solution discharged from the reaction vessel are the same in that a stable reaction can be performed. For example, while supplying A2 liquid to the reaction container at a supply rate of a2 (L / hour) and B2 liquid at a supply speed of b2 (L / hour), the reaction liquid is discharged from the reaction container at a2 + b2 (L / hour). Is preferably discharged.

  Moreover, the manufacturing method of the barium titanyl oxalate of the 3rd form of this invention mixes oxalic acid aqueous solution (A3 liquid), barium chloride aqueous solution (B3 liquid), and titanium tetrachloride as water as reaction raw material aqueous solution. An aqueous solution (C3 solution) obtained in this way is used.

  A3 liquid which concerns on the manufacturing method of the barium titanyl oxalate of the 3rd form of this invention is oxalic acid aqueous solution. The concentration of the oxalate ion in the A3 solution is not particularly limited, but is preferably 0.1 to 7.0 mol / L, particularly preferably 0.6 to 1.4 mol / L.

  B3 liquid which concerns on the manufacturing method of the barium titanyl oxalate of the 3rd form of this invention is barium chloride aqueous solution. The concentration of the Ba element in the B3 solution is not particularly limited, but is preferably 0.1 to 6.5 mol / L, and particularly preferably 0.5 to 1.3 mol / L.

  C3 liquid which concerns on the manufacturing method of the barium titanyl oxalate of the 3rd form of this invention is aqueous solution obtained by mixing titanium tetrachloride with water. The concentration of the Ti element in the C3 solution is not particularly limited, but is preferably 0.04 to 6.0 mol / L, particularly preferably 0.2 to 3.0 mol / L.

  In the method for producing barium titanyl oxalate according to the third aspect of the present invention, the production reaction of barium titanyl oxalate is performed in the reaction vessel by supplying the A3 solution, the B3 solution and the C3 solution to the reaction vessel.

  At this time, the ratio of the Ba element supply rate to the Ti element supply rate to the reaction vessel (Ba element supply rate / Ti element supply rate) is 0.5 to 3.0, preferably 1.0 to 1. .5. When the ratio of the supply rate of Ba element to the supply rate of Ti element to the reaction vessel is in the above range, approximately 1 barium titanate having a Ba / Ti molar ratio of 0.998 to 1.002 can be obtained. it can. The ratio of the oxalate ion supply rate to the Ti element supply rate to the reaction vessel (oxalate ion supply rate / Ti element supply rate) is 2.0 to 3.8, preferably 2.8 to 2.8 to 3.8. 3.8. When the ratio of the supply rate of oxalate ions to the supply rate of Ti element to the reaction vessel is in the above range, approximately 1 barium titanate having a Ba / Ti molar ratio of 0.998 to 1.002 is obtained. Can do.

  In the method for producing barium titanyl oxalate according to the third aspect of the present invention, the concentration of oxalate ions in the A3 solution, the concentration of the Ba element in the B3 solution, the concentration of the Ti element in the C3 solution, and the supply rate of the A3 solution (L / hour), B3 liquid supply speed (L / hour) and C3 liquid supply speed (L / hour) are appropriately selected, so that the supply speed of the Ba element with respect to the Ti element supply speed to the reaction vessel The ratio and the ratio of the supply rate of oxalate ions to the supply rate of Ti element to the reaction vessel can be adjusted.

  And in the manufacturing method of the barium titanyl oxalate of the 3rd form of this invention, a reaction liquid is discharged | emitted from a reaction container, supplying A3 liquid, B3 liquid, and C3 liquid to a reaction container. At this time, it is preferable that the total amount of the A3 liquid, the B3 liquid, and the C3 liquid supplied to the reaction container is the same as the amount of the reaction liquid discharged from the reaction container. For example, while supplying A3 liquid at a supply speed of a3 (L / hour), B3 liquid at b3 (L / hour), and C3 liquid at c3 (L / hour), the reaction liquid is supplied from the reaction container to the reaction container. Is preferably discharged at a discharge rate of a3 + b3 + c3 (L / hour).

  The method for producing barium titanyl oxalate of the present invention can be carried out, for example, using an overflow type reaction vessel shown in FIG. FIG. 1 is a schematic cross-sectional view of an overflow type reaction vessel. In FIG. 1, an overflow type reaction vessel 1 has an overflow pipe 2 attached to the upper part of the side wall of the reaction vessel. In the overflow type reaction vessel 1, since the overflow pipe 2 serves as a discharge port for the reaction liquid, the height of the liquid surface 4 of the reaction liquid 3 is always the height of the position where the overflow pipe 2 is attached, The reaction solution 3 overflows from the overflow pipe 2 and is discharged from the overflow type reaction vessel 1 by the amount of the aqueous solution supplied. That is, in the overflow type reaction vessel 1, the supply amount of the reaction raw material aqueous solution to the reaction vessel and the discharge amount of the reaction solution from the reaction vessel can always be the same amount. Therefore, if an overflow type reaction vessel is used, the reaction solution can be discharged from the reaction vessel while supplying the reaction raw material aqueous solution to the reaction vessel. In FIG. 1, the overflow type reaction vessel 1 actually has, for example, a stirring device, a heating device, a reaction raw material supply pipe, etc., but only the outline of the reaction vessel is shown for convenience of explanation. Other descriptions are omitted.

  The reaction vessel for carrying out the method for producing barium titanyl oxalate according to the present invention is not limited to the overflow type reaction vessel, but, for example, a stirring device is installed inside, and the supply amount of the reaction raw material aqueous solution is adjusted. A sealed reaction vessel or a stirring device equipped with a supply pipe equipped with a pump and the like and a discharge pipe fitted with a valve capable of adjusting the discharge amount of the reaction solution is installed inside, and the reaction raw material aqueous solution Examples thereof include a sealed reaction vessel equipped with a supply pipe provided with a pump capable of adjusting the supply amount and a discharge pipe for discharging the reaction liquid at a constant speed with a pump.

  In the method for producing barium titanyl oxalate of the present invention, the temperature of the reaction solution, that is, the reaction temperature is 50 to 90 ° C, preferably 50 to 70 ° C.

In the method for producing barium titanyl oxalate of the present invention, the residence time of the generated barium titanyl oxalate is preferably 1 to 60 minutes, particularly preferably 10 to 30 minutes. When the residence time of the generated barium titanyl oxalate is within the above range, the effect that the variation in the Ba / Ti molar ratio is small over the entire particle diameter can be advantageously increased industrially. On the other hand, if the residence time is less than the above range, it becomes difficult to control the molar ratio of Ba / Ti in the obtained barium titanyl oxalate, and the molar ratio of Ba / Ti is about 0.998 to 1.002. If the residence time exceeds the above range, the production rate of barium titanyl oxalate becomes slow, which is not industrially advantageous.
In the present invention, the residence time of the generated barium titanyl oxalate is a value obtained by dividing the volume (L) of the reaction solution in the reaction vessel by the discharge rate (L / hour) of the reaction solution from the reaction vessel ( Reaction liquid volume / reaction liquid discharge speed).

  In the method for producing barium titanyl oxalate of the present invention, the reaction solution discharged from the reaction vessel is subjected to solid-liquid separation to obtain a precipitate, and then washed and dried as necessary to obtain barium titanyl oxalate. Obtainable. Moreover, you may grind | pulverize the obtained barium titanyl oxalate as needed.

  Thus, the barium titanyl oxalate obtained by carrying out the method for producing barium titanyl oxalate of the present invention has a small variation in the Ba / Ti molar ratio over the entire particle size. And, by firing barium titanyl oxalate with a small variation in the Ba / Ti molar ratio over the entire particle size, barium titanate with high crystallinity can be obtained despite its small particle size, so it has excellent performance A dielectric ceramic material is obtained.

  The relationship between the particle diameter of the generated barium titanyl oxalate and the variation in the Ba / Ti molar ratio will be described. Using a sieve, barium titanyl oxalate produced by reaction of reaction raw materials is, for example, 10 μm or more and less than 50 μm (first group), 50 μm or more and less than 90 μm (second group), 90 μm or more and less than 130 μm (third group), The particle size ranges from 130 μm to less than 170 μm (fourth group) and from 170 μm to less than 210 μm (fifth group). Next, the Ba / Ti molar ratio of each group is determined. Then, the median value of the particle size of each group is used as the particle size of the group (for example, the median value of the particle size of the first group is 30 μm, the median value of the particle size of the second group is 70 μm, the particle size of the third group The median value of the fourth group is 110 μm, the median value of the particle size of the fourth group is 150 μm, the median value of the particle size of the fifth group is 190 μm), the horizontal axis is plotted, and the Ba / Ti molar ratio of each group is plotted on the vertical axis Then, a graph showing the relationship between the particle diameter of the generated barium titanyl oxalate and the Ba / Ti molar ratio is prepared.

  FIG. 2 is a schematic graph showing the relationship between the particle diameter of barium titanyl oxalate prepared as described above and the Ba / Ti molar ratio. In FIG. 2, symbol 11 is a graph of barium titanyl oxalate produced by the method for producing barium titanyl oxalate according to the present invention, and symbol 12 is produced by a conventional batch-type method for producing barium titanyl oxalate. 1 is a graph of barium titanyl oxalate. As shown in FIG. 2, the barium titanyl oxalate produced by the conventional production method has a smaller Ba / Ti molar ratio as the particle size is smaller, while a larger Ba / Ti molar ratio as the particle size is larger. Yes. In contrast, the barium titanyl oxalate produced by the method for producing barium titanyl oxalate of the present invention has a constant Ba / Ti molar ratio over the entire particle size range, that is, Ba / Ti over the entire particle size range. The variation in Ti molar ratio is small.

  The bulk Ba / Ti molar ratio of barium titanyl oxalate obtained by carrying out the method for producing barium titanyl oxalate of the present invention is 0.998 to 1.002, more preferably closer to 1. The bulk Ba / Ti molar ratio of barium titanyl oxalate refers to the average value of the Ba / Ti molar ratio of the entire barium titanyl oxalate. That is, it is the Ba / Ti molar ratio obtained by directly analyzing the generated barium titanyl oxalate without sieving.

  The method for producing barium titanate of the present invention is a method for producing barium titanate to obtain barium titanate by firing barium titanyl oxalate obtained by performing the method for producing barium titanyl oxalate of the present invention. The method for producing barium titanyl oxalate of the present invention to obtain barium titanyl oxalate is as described above.

That is, in the method for producing barium titanate of the present invention, an aqueous solution (A1 solution) obtained by mixing oxalic acid and titanium tetrachloride with water and an aqueous barium chloride solution (B1 solution) are supplied to the reaction vessel. This is a method for producing barium titanate to obtain barium titanate by firing barium titanyl oxalate obtained by performing a reaction for producing barium titanyl oxalate while discharging the reaction liquid from the reaction vessel.
Moreover, the manufacturing method of the barium titanate of this invention is supplying the reaction container with the oxalic acid aqueous solution (A2 liquid) and the aqueous solution (B2 liquid) obtained by mixing titanium tetrachloride and barium chloride with water. This is a method for producing barium titanate to obtain barium titanate by firing barium titanyl oxalate obtained by performing a reaction for producing barium titanyl oxalate while discharging the reaction liquid from the reaction vessel.
The method for producing barium titanate of the present invention comprises an oxalic acid aqueous solution (A3 solution), a barium chloride aqueous solution (B3 solution), and an aqueous solution (C3 solution) obtained by mixing titanium tetrachloride with water. Production of barium titanate to obtain barium titanate by firing barium titanyl oxalate obtained by performing a reaction for producing barium titanyl oxalate while supplying the reaction liquid to the reaction container and discharging the reaction liquid from the reaction container. Is the method.

  Organic substances derived from oxalic acid contained in the final product are preferable because they deteriorate 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 firing to obtain the target barium titanate and to sufficiently remove organic substances derived from oxalic acid.

In the method for producing barium titanate of the present invention, the firing temperature when firing barium titanyl oxalate is 600 to 1300 ° C, preferably 700 to 1200 ° C. When the firing temperature at the time of firing barium titanyl oxalate is in the above range, the variation in particle size is small, and single-phase barium titanate is obtained in X-ray diffraction analysis having high crystallinity. On the other hand, if the firing temperature is less than the above range, it is difficult to obtain single-phase barium titanate in X-ray diffraction analysis, and if it exceeds the above range, the particle size variation of the obtained barium titanate tends to increase. Is not preferable.
The firing time is preferably 2 to 30 hours, particularly preferably 5 to 27 hours. The firing atmosphere is not particularly limited, and may be any of an inert gas atmosphere, a vacuum atmosphere, an oxidizing gas atmosphere, and the air, or firing is performed in the atmosphere while introducing water vapor. May be.

  In the method for producing barium titanate of the present invention, the barium titanyl oxalate may be fired by multi-stage firing with different firing temperatures. Further, for the purpose of making the powder characteristics uniform, the fired material may be pulverized and then refired or reground.

  The barium titanate obtained by carrying out the method for producing barium titanate of the present invention can be pulverized or classified as necessary.

  Thus, the physical property of barium titanate obtained by carrying out the method for producing barium titanate of the present invention is approximately 1 with a Ba / Ti molar ratio of 0.998 to 1.002. Even if it is small, the crystallinity is high.

  Furthermore, the barium titanate obtained by firing conventional barium titanyl oxalate is easily obtained as coarse particles in which each particle is joined by sintering or the like after firing (see FIG. 6). According to the method for producing barium, each particle is easily obtained in a dispersed shape. Therefore, compared to the conventional method, the coarse particles in which the particles are bonded by sintering are less dispersible (see FIG. 3 to FIG. 5).

  Therefore, barium titanate obtained by performing the method for producing barium titanate of the present invention has excellent performance as a dielectric ceramic.

  In addition, the barium titanate obtained by carrying out the method for producing barium titanate of the present invention is prepared by adding the subcomponent element-containing compound to the method for producing barium titanate of the present invention for the purpose of adjusting dielectric characteristics and temperature characteristics as necessary. In addition to the barium titanate obtained, subcomponent elements can be contained. 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 Examples include compounds containing elements.

  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. In the case where 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 or the like. 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, barium titanate and the subcomponent element-containing compound may be uniformly mixed and then fired. Alternatively, baking may be performed after uniformly mixing barium titanyl oxalate and the subcomponent element-containing compound.

  For example, when producing a multilayer ceramic capacitor using the barium titanate obtained by the method for producing barium titanate according to the present invention, first, a known addition of barium titanate powder including subcomponent elements is added. A sheet is formed by mixing and dispersing in an appropriate solvent together with a compounding agent such as an agent, an organic binder, a plasticizer, and a dispersing agent. 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 paste, 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 ceramic capacitor.

  In addition, the barium titanate powder obtained by the method for producing barium titanate of the present invention is blended with a resin such as an epoxy resin, a polyester resin, or a polyimide resin, and a resin sheet, a resin film, an adhesive, and the like. Then, materials for printed wiring boards and multilayer printed wiring boards, co-materials for suppressing shrinkage differences between internal electrodes and dielectric layers, electrode ceramic circuit boards, glass ceramic circuit boards, circuit peripheral materials, and inorganic EL It can be used as a dielectric material.

  Further, the barium titanate obtained by the method for producing barium titanate of the present invention is a catalyst used in reactions such as exhaust gas removal and chemical synthesis, and surface modification of printing toner that imparts antistatic and cleaning effects. It is suitably used as a material.

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

Example 1
An aqueous solution obtained by adding 250 g of oxalic acid dihydrate to 2154 g of water was mixed with 332 g of a titanium tetrachloride aqueous solution having a concentration of Ti of 2.56 mol / L, so that oxalic acid was 0.79 mol / L and Ti was 0.26 mol / L. An aqueous solution (A1 solution) obtained by mixing oxalic acid which is L and titanium tetrachloride with water was prepared. That is, the molar ratio of oxalate ion to Ti element in the A1 solution is 3.1. Further, 195 g of barium chloride was dissolved in 963 g of water to prepare an aqueous barium chloride solution (B1 solution) having Ba of 0.80 mol / L. Next, pure water was added to the reaction vessel and maintained at 55 ° C., and the A1 solution and B1 solution were supplied to the reaction vessel at a rate of 0.9 L / hour and 0.4 L / hour, respectively, with stirring. That is, the ratio of the supply rate of the Ba element to the supply rate of the Ti element to the reaction vessel was 1.3, and the reaction was performed with the residence time of the generated barium titanyl oxalate being 14 minutes.
Solid-liquid separation was performed from the reaction solution discharged from the reaction vessel to obtain a precipitate, which was washed and dried to obtain barium titanyl oxalate.
In order to measure the Ba / Ti molar ratio of the obtained barium titanyl oxalate, the barium titanyl oxalate was calcined and then subjected to fluorescent X-ray analysis. The bulk Ba / Ti molar ratio was 1.001. .
Furthermore, the obtained barium titanyl oxalate was sieved to 45 μm to less than 75 μm (first group), 75 μm to less than 100 μm (second group), 100 μm to less than 150 μm (third group), 150 μm or more (first 4 groups), and the Ba / Ti molar ratios of the first group and the third group were determined in the same manner as the bulk Ba / Ti molar ratio measurement method. The Ba / Ti molar ratios of the first group and the third group were 1.001 and 1.001, respectively.
Of the obtained barium titanyl oxalate, the one before sieving was baked at 1000 ° C. for 21 hours to obtain barium titanate. About the obtained barium titanate, the ratio of the c-axis to a-axis length (c-axis / a-axis ratio), which is an index of crystallinity, was measured by XRD to be 1.011, and the specific surface area by the BET method was It was 1.2 m ² / g when measured. Moreover, the SEM photograph of the obtained barium titanate is shown in FIG.

(Example 2)
250 g of oxalic acid dihydrate was dissolved in 2628 g of water to prepare an aqueous oxalic acid solution (A2 solution) in which oxalic acid was 0.89 mol / L. An aqueous solution obtained by adding 195 g of barium chloride to 963 g of water is mixed with 332 g of a titanium tetrachloride aqueous solution having a concentration of Ti of 2.56 mol / L, and the chloride containing 0.63 mol / L of barium chloride and 0.53 mol / L of Ti. An aqueous solution (B2 solution) obtained by mixing barium and titanium tetrachloride with water was prepared. That is, the molar ratio of Ba element to Ti element in B2 solution is 1.3. Next, pure water was added to the reaction vessel and maintained at 55 ° C., and the A2 solution and B2 solution were supplied to the reaction vessel at a rate of 1.0 L / hour and 0.5 L / hour, respectively, with stirring. That is, the ratio of the supply rate of oxalate ions to the supply rate of Ti element to the reaction vessel was 3.1, and the reaction was performed with the residence time of the generated barium titanyl oxalate being 12 minutes.
Solid-liquid separation was performed from the reaction solution discharged from the reaction vessel to obtain a precipitate, which was washed and dried to obtain barium titanyl oxalate.
When the obtained barium titanyl oxalate was calcined and then subjected to fluorescent X-ray analysis, the bulk Ba / Ti molar ratio was 0.998.
Furthermore, the obtained barium titanyl oxalate was sieved to 45 μm to less than 75 μm (first group), 75 μm to less than 100 μm (second group), 100 μm to less than 150 μm (third group), 150 μm or more (first 4 groups), and the Ba / Ti molar ratios of the first group and the third group were determined in the same manner as the bulk Ba / Ti molar ratio measurement method. The Ba / Ti molar ratios of the first group and the third group were 0.997 and 0.998, respectively.
Of the obtained barium titanyl oxalate, the one before sieving was baked at 1000 ° C. for 21 hours to obtain barium titanate. The c-axis / a-axis ratio by XRD of the obtained barium titanate was 1.010, and the specific surface area by the BET method was 1.5 m ² / g. Moreover, the SEM photograph of the obtained barium titanate is shown in FIG.

(Example 3)
250 g of oxalic acid dihydrate was dissolved in 2628 g of water to prepare an oxalic acid aqueous solution (A3 solution) having an oxalic acid content of 0.89 mol / L. 195 g of barium chloride was dissolved in 963 g of water to prepare an aqueous barium chloride solution (B3 solution) having Ba of 0.80 mol / L. 332 g of titanium tetrachloride aqueous solution (C3 solution) having a concentration of Ti of 2.56 mol / L was prepared. Next, pure water is added to the reaction vessel and maintained at 55 ° C., and the reaction vessel is stirred at a rate of 1.0 L / hour, 0.4 L / hour, and 0.1 L / hour for the A3 solution, B3 solution, and C3 solution, respectively. Supplied to. That is, the ratio of the supply rate of oxalate ions to the supply rate of Ti element to the reaction vessel is 3.1, the ratio of the supply rate of Ba element to the supply rate of Ti element is 1.3, and the oxalic acid produced The reaction was carried out with a barium titanyl residence time of 12 minutes.
Solid-liquid separation was performed from the reaction solution discharged from the reaction vessel to obtain a precipitate, which was washed and dried to obtain barium titanyl oxalate.
When the obtained barium titanyl oxalate was baked and then subjected to fluorescent X-ray analysis, the bulk Ba / Ti molar ratio was 0.999.
Furthermore, the obtained barium titanyl oxalate was sieved to 45 μm to less than 75 μm (first group), 75 μm to less than 100 μm (second group), 100 μm to less than 150 μm (third group), 150 μm or more (first 4 groups), and the Ba / Ti molar ratios of the first group and the third group were determined in the same manner as the bulk Ba / Ti molar ratio measurement method. The Ba / Ti molar ratios of the first group and the third group were 0.998 and 0.999, respectively.
Of the obtained barium titanyl oxalate, the one before sieving was baked at 1000 ° C. for 21 hours to obtain barium titanate. The c-axis / a-axis ratio by XRD of the obtained barium titanate was 1.010, and the specific surface area by the BET method was 1.4 m ² / g. Moreover, the SEM photograph of the obtained barium titanate is shown in FIG.

(Comparative Example 1)
A batch-type reaction vessel was prepared, and 325 g of oxalic acid dihydrate was dissolved in 1400 g of water brought to 55 ° C. to prepare an aqueous oxalic acid solution (A11 solution) in which oxalic acid was 1.73 mol / L. 630 g of titanium tetrachloride aqueous solution having a concentration of 2.6 mol / L Ti is mixed with an aqueous solution obtained by adding 325 g of barium chloride to 1830 g of water, and chloride containing 0.55 mol / L of barium chloride and 0.52 mol / L of Ti. An aqueous solution (B11 solution) obtained by mixing barium and titanium tetrachloride with water was prepared. That is, the molar ratio of Ba element to Ti element in B11 solution is 1.1. Next, the B11 solution was added dropwise to the A11 solution at 55 ° C. with stirring at a rate of 0.7 L / hour and supplied to the reaction vessel. That is, the ratio of oxalate ions to Ti element in the reaction vessel at the time of completion under the B11 droplet is 2.1.
After aging for 0.5 hour, the reaction solution was subjected to solid-liquid separation to obtain a precipitate, washed and dried to obtain barium titanyl oxalate.
When the obtained barium titanyl oxalate was baked and then subjected to fluorescent X-ray analysis, the bulk Ba / Ti molar ratio was 0.999.
Furthermore, the obtained barium titanyl oxalate was sieved to 45 μm to less than 75 μm (first group), 75 μm to less than 100 μm (second group), 100 μm to less than 150 μm (third group), 150 μm or more (first 4 groups), and the Ba / Ti molar ratios of the first group and the third group were determined in the same manner as the bulk Ba / Ti molar ratio measurement method. The Ba / Ti molar ratios of the first group and the third group were 0.997 and 1.000, respectively.
Of the obtained barium titanyl oxalate, the one before sieving was baked at 1000 ° C. for 21 hours to obtain barium titanate. The c-axis / a-axis ratio by XRD of the obtained barium titanate was 1.009, and the specific surface area by the BET method was 1.1 m ² / g. Moreover, the SEM photograph of the obtained barium titanate is shown in FIG.

  From Table 1, it can be seen from Comparative Example 1 that barium titanyl oxalate produced by a conventional production method has a smaller Ba / Ti molar ratio as the particle size is smaller, while a larger Ba / Ti molar ratio as the particle size is larger. It has become. On the other hand, the barium titanyl oxalate produced by the method for producing barium titanyl oxalate of the present invention from Example 1, Example 2 and Example 3 has a Ba / Ti molar ratio over the entire particle size range. The variation in the Ba / Ti molar ratio is small over a certain range, that is, over the entire particle size range.

1) Evaluation of dispersibility in the table is “◯” when the number of particles having a particle diameter of 5 μm in which the particles are bonded by sintering is less than 3 in a 10,000 times SEM photograph. In some cases, it was evaluated as “×”.

  From Table 2, with respect to the obtained barium titanate, in Example 1, Example 2, and Example 3, those having a specific surface area larger than that of Comparative Example 1, that is, having a smaller particle diameter, are obtained. Moreover, in Example 1, Example 2, and Example 3, those having a c-axis / a-axis ratio larger than that of Comparative Example 1, that is, high crystallinity are obtained. That is, from Table 2, the barium titanate obtained in Example 1, Example 2, and Example 3 has a smaller particle size and higher crystallinity than barium titanate produced by a conventional production method. It can be said that Moreover, it turns out that the barium titanate obtained with the manufacturing method of this invention is excellent in powder characteristics, such as a dispersibility with few coarse particles with which the particle | grains were couple | bonded by sintering.

1 Overflow type reaction vessel 2 Overflow tube 3 Reaction solution 4 Liquid surface

Claims (6)

  While supplying an aqueous solution (A1 solution) obtained by mixing oxalic acid and titanium tetrachloride with water and an aqueous barium chloride solution (B1 solution) to the reaction vessel, discharging the reaction solution from the reaction vessel, A method for producing barium titanyl oxalate, characterized by carrying out a reaction for producing barium titanyl acid.   While supplying an aqueous solution of oxalic acid (A2 solution) and an aqueous solution (B2 solution) obtained by mixing titanium tetrachloride and barium chloride with water, while discharging the reaction solution from the reaction vessel, A method for producing barium titanyl oxalate, characterized by carrying out a reaction for producing barium titanyl acid.   While supplying an oxalic acid aqueous solution (A3 solution), a barium chloride aqueous solution (B3 solution), and an aqueous solution (C3 solution) obtained by mixing titanium tetrachloride with water, the reaction solution is supplied to the reaction vessel. A method for producing barium titanyl oxalate, wherein the production reaction of barium titanyl oxalate is performed while discharging from the waste water.   The method for producing barium titanyl oxalate according to any one of claims 1 to 3, wherein the residence time of the generated barium titanyl oxalate in the reaction vessel is 1 to 60 minutes.   The manufacturing method of barium titanate characterized by baking the barium titanyl oxalate obtained by performing the manufacturing method of the barium titanyl oxalate of any one of Claims 1-4.   The method for producing barium titanate according to claim 5, wherein the firing temperature is 600 to 1300 ° C.