JP4441306B2 - Method for producing calcium-doped barium titanate - Google Patents

Description

  The present invention relates to a method for producing calcium-doped barium titanate that is spherical and has an average particle diameter of primary particles of 1 μm or less.

  Barium titanate powder is widely applied as a dielectric material for electronic parts such as piezoelectric elements and PTC thermistors, and is particularly useful for substrates of multi-layer ceramic capacitors. In general, the multi-layer ceramic capacitor is manufactured by alternately laminating ceramic dielectric layers and internal electrode layers in layers and firing and integrating them. The barium titanate powder thus produced is slurried in a binder or the like and then sintered to form a ceramic dielectric layer. Recently, the ceramic dielectric layer has been made thinner to meet the demand for smaller size and larger capacity. In this case, the withstand voltage characteristics are good, the aggregation of particles does not occur at the time of slurrying, the layer density becomes uniform, and the capacitor capacity needs to be sufficiently secured. In addition, the following characteristics are required for the composite oxide forming the dielectric ceramic layer such as barium titanate.

(1) Ultrafine particles with an average particle size of 1 μm or less, spherical shape, and narrow particle size distribution.
(2) Good crystallinity and a perovskite structure.
(3) The Ba / Ti atomic ratio is very close to 1.00 and is controlled by a 1/1000 system.
(4) Excellent dispersibility when slurried or pasted.
(5) Have good sintering characteristics.

  Conventionally, for example, in the case of barium titanate powder, it has been produced by a solid phase reaction in which a titanium compound and a barium compound are mixed and fired. However, since the compound is reacted at a high temperature in such a solid phase reaction, the obtained barium titanate powder has a relatively large particle size of about 0.5 μm, a wide particle size distribution, and a non-constant shape. It was inferior in dispersibility when it was made into a slurry or paste. Further, when the particle diameter of barium titanate is so large, there is a limit to thinning the ceramic dielectric layer.

For this reason, in order to obtain ultrafine barium titanate powder having an average particle size of 1 μm or less, it is known that a liquid phase reaction method such as a hydrolysis method or a hydrothermal synthesis method is preferable (for example, Patent Document 1 and 2). In Patent Document 1, the formula ABO ₃ (wherein A is a metal cation selected from Ba, Sr, Ca, Mg, Pb, and Nd and mixtures thereof, B is Ti, Zr, Nb, Hf, Zn, and A metal cation selected from Sn and a mixture thereof), a compound selected from a hydroxide, chloride, nitride, acetate of metal A and an organic compound of metal B, A method of mixing under high stirring energy conditions is disclosed.

In Patent Document 2, the general formula _{A x (BO 3) y (} A Li +, Na +, K +, Mg 2+, Ca 2+, Sr 2+, selected from ^{Ba 2+} and ^{La 3+,} B is ^{Ti 4+} , Zr ⁴⁺ , Sn ⁴⁺ , Hf ⁴⁺ , Nb ⁵⁺ and Ta ⁵⁺ , where x is equal to the valence of the anion BO ₃ and y is equal to the valence of the cation A) As a method, an inorganic or organic salt or organometallic compound of at least one metal A and an inorganic or organic salt or organometallic compound of at least one metal B and A in the vicinity of a stoichiometric value corresponding to the above general formula are used. An aqueous solution containing a / B ratio, and an aqueous base solution preheated to a temperature of 70 to 100 ° C. containing at least a stoichiometric amount of an inorganic or organic base corresponding to the general formula Discloses a production method comprising contacting with stirring.

JP-A-1-286923 Japanese Patent Laid-Open No. 7-232923

  In the method of Patent Document 1, water and a surfactant are placed in a reaction vessel in advance, and a titanium compound of alkoxy titanium is reacted with an alkali such as barium hydroxide or barium chloride and sodium hydroxide. The barium hydroxide obtained in this way is brought into contact with and reacted under high stirring conditions. In the case of such a method, it is difficult to maintain a high pH during the contact and reaction between the titanium compound and the barium compound, and thus it is difficult to maintain a uniform reaction, and the Ba / Ti atomic ratio of the generated barium titanate There is a problem that it is difficult to control.

  Further, in the method of Patent Document 2, since a mixed aqueous solution of an acidic titanium compound and a barium salt is used as a starting material, it is difficult to prepare the mixed aqueous solution. In particular, the concentration of the titanium compound and the barium salt in the mixed aqueous solution is reduced. There was a limit. Specifically, when a mixed aqueous solution of titanium tetrachloride and barium chloride was prepared, the total concentration of metal ions had a limit of about 1.2 mol / l, and there was a problem in productivity. In addition, when carbonate is mixed in the starting raw material liquid, it is difficult to control the Ba / Ti atomic ratio, and carbonate is mixed in the powder salt as a reaction product, resulting in a decrease in quality. Has a problem that the relative dielectric constant does not increase unless it is fired. Furthermore, although the barium titanate obtained by the above prior art has fine particles, it has poor dispersibility when slurried and eventually aggregates, making it difficult to thin the ceramic dielectric layer. Was left.

  Furthermore, it is generally known that barium titanate improves the reduction resistance and DC bias characteristics of barium titanate by replacing barium sites with calcium to form calcium-doped barium titanate. As a method for producing calcium-doped barium titanate, the examples of Patent Document 1 and Patent Document 2 described above are also disclosed, but as described above, since the uniform reaction is not maintained in the methods of these Patent Documents, Ba, There is a problem that it is difficult to control the atomic ratio of Ca and Ti. For this reason, the manufactured calcium-doped barium titanate has a low dielectric constant, and improvement of the dielectric constant is required.

  Therefore, the present invention provides the above characteristics (1) to (5), that is, ultrafine particles having an average particle size of 1 μm or less, spherical shape, narrow particle size distribution, good crystallinity, and [Ca + Ba] / Ti atomic ratio is stable, and the content of each atom of Ca, Ba and Ti can be stably controlled at a high concentration, excellent dispersibility when slurried or pasted, and good sintering characteristics It is an object of the present invention to provide a method for producing calcium-doped barium titanate that sufficiently satisfies the properties of having a ferroelectric property.

  As a result of intensive studies on the calcium-doped barium titanate powder that can achieve the above object, the present inventors prepared a titanium compound aqueous solution, a barium compound aqueous solution, and a calcium compound aqueous solution as starting materials, respectively. It has been found that by continuously contacting the aqueous solution, the atomic ratio of Ca, Ba and Ti can be easily controlled, and the intended titanium-based composite oxide powder can be obtained, and the present invention has been completed.

Therefore, the method for producing calcium-doped barium titanate of the present invention has been made based on such knowledge, and in an alkaline aqueous solution, halide, hydroxide, nitrate, sulfate, acetate, perchlorate 1 or 2 or more types of titanium compound aqueous solutions selected from acid salts and oxalates, 1 type or 2 or more types selected from halides, hydroxides, nitrates, sulfates, acetates and perchlorates Of calcium-doped barium titanate to which an aqueous solution of barium compound is added, and one or more calcium compound aqueous solutions selected from halides, hydroxides, nitrates, sulfates, acetates and perchlorates are added and contacted In the production method, the barium compound aqueous solution is added to the titanium compound aqueous solution and the calcium aqueous solution before being added to the alkaline aqueous solution. Without engaged, it was added into the alkaline aqueous solution, an aqueous solution wherein the titanium compound aqueous solution and the calcium compound before mixing with the barium compound aqueous solution is characterized Rukoto contacting a premixed aqueous solution.

  According to the method for producing calcium-doped barium titanate of the present invention, ultrafine particles having an average particle size of 1 μm or less, spherical shape, narrow particle size distribution, good crystallinity, and [Ca + Ba] / Ti atomic ratio are It is stable, and the content of each atom of Ca, Ba and Ti can be stably controlled at a high concentration, has excellent dispersibility when slurried or pasted, and has good sintering characteristics. A calcium-doped barium titanate that is sufficiently satisfied and has ferroelectricity can be obtained.

Hereinafter, more preferred embodiments of the present invention will be described.
The method for producing calcium-doped barium titanate of the present invention comprises preparing a titanium compound aqueous solution, a barium compound aqueous solution, and a calcium compound aqueous solution, respectively, and adding and contacting these compound aqueous solutions in a separately prepared alkaline aqueous solution. Thus, calcium-doped barium titanate having the above characteristics can be produced. Hereafter, each compound aqueous solution in this invention and these contact methods are demonstrated.

(1) Titanium compound aqueous solution
As the titanium compound in the titanium compound aqueous solution in the present invention, one or more selected from halides, hydroxides, nitrates, sulfates, acetates, perchlorates and oxalates are used. Specific examples of the compound include titanium tetrachloride, titanium trichloride, titanium hydroxide, and titanyl sulfate. Among these, titanium tetrachloride is preferably used.

  The titanium ion concentration in the titanium compound aqueous solution is suitably 0.1 mol / l or more, preferably 0.3 mol / l or more, and preferably 0.4 to 3.0 mol / l from the viewpoint of improving purity. When the titanium ion concentration is less than 0.1 mol / l, the reaction rate is extremely reduced, and therefore a higher concentration is preferable for improving productivity. In the present invention, since a single aqueous solution of the titanium compound is prepared and used, the concentration of the aqueous titanium compound solution can be increased, and as a result, the productivity can be improved.

  Furthermore, the temperature of the titanium compound aqueous solution is preferably preheated and maintained at 30 to 90 ° C, preferably 40 to 50 ° C. When this temperature exceeds 60 ° C., the titanium compound is hydrolyzed and a solid is precipitated, making it difficult to obtain a uniform aqueous solution. As a result, it becomes difficult to control the atomic ratio of Ca, Ba, and Ti of the product.

  Moreover, as water which prepares the titanium compound aqueous solution in this invention, it is preferable to use the water deionized with the ion exchange resin etc., and also the water which degassed the destructive gas, such as a carbon dioxide. If the titanium compound aqueous solution is dehydrochlorinated by means such as bubbling argon gas before contacting with the barium compound aqueous solution and the calcium compound aqueous solution, the chlorine content in the calcium-doped barium titanate powder obtained is reduced. Is preferable.

(2) Barium compound aqueous solution
As the barium compound in the present invention, one or more selected from halides, hydroxides, nitrates, sulfates, acetates and perchlorates are used. Specific examples of the compound include barium chloride, barium hydroxide, barium nitrate, barium sulfate, and barium acetate. Among these, barium chloride and barium hydroxide are preferably used. In the case of halides such as barium chloride, nitrates, sulfates, acetates, etc., barium chloride is previously contacted with an alkali metal hydroxide such as NaOH or KOH to generate barium hydroxide and used. And more effective.

  Moreover, 0.05 mol / l or more is suitable for the barium ion concentration of the barium compound aqueous solution in this invention, Preferably it is 0.1-2.0 mol / l. When the barium ion concentration is less than 0.05 mol / l, the reaction rate is extremely reduced, so that a higher concentration is preferable for improving productivity. For example, the solubility of barium chloride is limited to about 1.2 mol / l, but when this is mixed with an aqueous titanium compound solution, the solubility is less than half. If the concentration is too high, the solution becomes non-uniform, and as a result, the reaction becomes non-uniform. Thus, in the present invention, since the barium compound aqueous solution is prepared and used as the raw material aqueous solution separately from the aqueous solution of the titanium compound, similarly to the titanium compound aqueous solution, the barium ion concentration can be further increased. As a result, productivity can be improved.

  In the present invention, when the barium compound is, for example, a halide such as barium chloride, a barium salt such as nitrate, sulfate, acetate, etc., these barium salts are once converted into barium hydroxide, and this is converted into a titanium compound aqueous solution and calcium. When contacted with an aqueous compound solution, the resulting calcium-doped barium titanate powder becomes highly pure and more effective. For example, in a method in which an aqueous solution of titanium tetrachloride, an aqueous solution of calcium chloride and an aqueous solution of barium chloride are simultaneously contacted in an aqueous alkaline solution, or a method in which a mixed aqueous solution of titanium tetrachloride, calcium chloride and barium chloride is added to an aqueous alkaline solution and contacted, Chlorine tends to remain in the calcium-doped barium titanate that is a reaction product. However, by converting the barium compound into an alkaline aqueous solution in advance and converting the barium compound into a hydroxide in advance, the reaction with the titanium compound proceeds more uniformly, and a higher-purity calcium-doped barium titanate with less chlorine content is obtained. Can be manufactured.

  As the alkaline aqueous solution, an aqueous solution of an alkali metal hydroxide such as NaOH or KOH is used. The concentration of such a hydroxide is usually 0.2 to 15 mol / l, and is preferably a concentration sufficient to convert the barium compound into a hydroxide, that is, equal to or higher than the barium ion concentration. .

  Furthermore, in the present invention, barium hydroxide may be used as an alkali source without using the alkali metal hydroxide as described above. That is, the barium compound aqueous solution may be prepared from only barium hydroxide, or may be prepared from a barium compound other than barium hydroxide such as barium chloride and barium hydroxide.

  Further, the temperature of the barium compound aqueous solution is preferably preheated to 80 to 100 ° C., preferably the same temperature as the actual reaction system, because the reaction with the titanium compound aqueous solution is promoted. Further, during the reaction of the aqueous titanium compound solution, the aqueous barium compound solution, and the aqueous calcium compound solution, it is possible to keep the reaction temperature constant by keeping the temperature change within ± 1 ° C. Ca and Ba of the calcium-doped barium titanate obtained And Ti are preferable because the atomic ratio is stable.

  Furthermore, as water for preparing the barium compound aqueous solution in the present invention, it is preferable to use water deionized with an ion exchange resin or the like, and further water degassed with carbon dioxide or the like.

  Further, in the present invention, the alkaline aqueous solution of barium compound obtained by the above-described method may be used as it is. However, it is easier to control the atomic ratio of Ca, Ba, and Ti by performing filtration before that. Effective for high purity. For example, when NaOH is used as the alkali source, sodium carbonate contained as an impurity in NaOH reacts with the barium compound, and barium carbonate precipitates. Since this causes contamination during the reaction, it is desirable to remove it beforehand by filtration. In this respect, the method of the present invention in which a titanium compound aqueous solution and a barium compound alkali aqueous solution are separately prepared and brought into contact with each other has a purity higher than that of, for example, a method in which a mixed solution of a titanium compound and a barium compound is added to an alkali solution. High barium titanate can be obtained.

  As in the case of the titanium compound aqueous solution, it is desirable that the alkali aqueous solution of the barium compound thus prepared is stored while avoiding contact with the atmosphere. Moreover, it is more preferable that the aqueous alkali solution of the barium compound is degassed before the reaction.

(3) Calcium compound aqueous solution
As the calcium compound in the present invention, one or more selected from halides, hydroxides, nitrates, sulfates, acetates and perchlorates are used. Specifically, halides, hydroxides and the like are used, and among these, calcium chloride is preferably used.

  Moreover, 0.01-1 mol / l is suitable for the calcium ion concentration of the calcium compound aqueous solution in this invention, It is preferable to adjust to 0.03-0.05 mol / l preferably. When the calcium ion concentration is less than 0.01 mol / l, the amount of calcium atoms substituted for the barium site of barium titanate is insufficient, so that the effect of suppressing particle growth is reduced when the generated calcium-doped barium titanate is fired.

  Furthermore, the temperature of the calcium compound aqueous solution is 30 to 90 ° C., preferably 40 to 50, similarly to the temperature of the titanium compound aqueous solution, in order to control the [Ca + Ba] / Ti atomic ratio of the calcium-doped barium titanate obtained. It is desirable to keep it preheated to ℃.

  Moreover, as water which prepares the calcium compound aqueous solution in this invention, it is preferable to use the water deionized with the ion exchange resin etc., and also the water which deaerated the residual gas, such as a carbon dioxide.

(4) Contacting method of titanium compound aqueous solution, barium compound aqueous solution and calcium compound aqueous solution First, barium is maintained so that the pH during contact and reaction is 13 or more, preferably 13.5 or more, more preferably 13.8 or more. The alkali concentration of the compound aqueous solution is adjusted. In order to maintain a predetermined pH during the reaction, it is also possible to supply a necessary amount of an aqueous alkali solution such as an aqueous NaOH solution from another system. Preferably, an aqueous alkali solution prepared in advance at a predetermined concentration is poured into a reaction vessel, and the titanium compound aqueous solution, barium compound aqueous solution and calcium compound aqueous solution are added to and brought into contact with the alkaline aqueous solution. In this case, the alkaline aqueous solution is preferably heated in advance so that the reaction temperature becomes a predetermined reaction temperature after adding the titanium compound aqueous solution, the barium compound aqueous solution and the calcium compound aqueous solution. Thus, by maintaining a constant pH during the reaction, a uniform reaction is maintained, and as a result, a uniform calcium-doped barium titanate with a controlled atomic ratio of Ca, Ba and Ti can be produced.

  Further, before the calcium compound aqueous solution is brought into contact with the titanium compound aqueous solution and the barium compound aqueous solution, the calcium compound aqueous solution is previously mixed with the titanium compound aqueous solution to prepare a mixed aqueous solution of the titanium compound and the calcium compound, and this mixed aqueous solution is used as the alkaline aqueous solution of the barium compound. May be contacted.

  In addition, when the titanium compound aqueous solution, barium compound aqueous solution and calcium compound aqueous solution are brought into contact and reacted, it is necessary to control the molar ratio of the titanium compound, barium compound and calcium compound. In order to carry out a uniform reaction, it is also preferable to keep the absolute concentration of the compound, barium compound or calcium compound in the reaction system as constant as possible from the beginning of the reaction to the end of the reaction. For this purpose, in the method of previously injecting an alkaline aqueous solution into the reaction vessel as described above, and adding the titanium compound aqueous solution, barium compound aqueous solution and calcium compound aqueous solution therein, in the initial stage of the reaction, the titanium compound, barium compound and Since the concentration of the calcium compound is diluted and reacted in a diluted state, calcium-doped barium titanate having a predetermined atomic ratio of Ca, Ba, and Ti is not generated. Therefore, the barium compound previously used for the barium compound aqueous solution in the alkaline aqueous solution in the reaction vessel, the titanium compound used for the titanium compound aqueous solution, or the mixture of the titanium compound used in the titanium compound aqueous solution and the calcium compound used in the calcium compound aqueous solution. Add it. Among these, since the concentration of the barium compound affects the atomic ratio of Ca, Ba and Ti of the calcium-doped barium titanate produced, it is desirable to add the barium compound to the alkaline aqueous solution in the reaction vessel.

  Next, a titanium compound aqueous solution, a barium compound aqueous solution and a calcium compound aqueous solution, or a mixed aqueous solution of a titanium compound aqueous solution and a calcium compound aqueous solution and a barium compound aqueous solution are instantaneously and continuously at a constant flow rate through piping from each storage container. To be fed into the reaction vessel and brought into contact. Here, the temperature at which the titanium compound aqueous solution, the barium compound aqueous solution and the calcium compound aqueous solution are brought into contact is set to 80 to 200 ° C., preferably 80 to 100 ° C., more preferably 85 to 95 ° C. Make it almost constant to be ± 1 ° C.

  Then, by bringing the titanium compound aqueous solution, barium compound aqueous solution and calcium compound aqueous solution into contact with each other in the reaction vessel and reacting for a sufficient time, particulate calcium-doped barium titanate is generated. The produced calcium-doped barium titanate can be extracted by a method of continuously extracting it in a slurry state during the reaction (continuous reaction) or a method of extracting (batch reaction) once the reaction is completed in the reaction vessel.

  The calcium-doped barium titanate thus produced is preferably subjected to heat treatment in a slurry state after the reaction (aging reaction). The temperature of this heat treatment is usually 80 to 100 ° C. or higher than the above reaction temperature, for example, 100 to 200 ° C. The heat treatment time is usually 1 minute to 30 hours, preferably 1 minute to 1 hour. By this heat treatment, the unreacted titanium compound, barium compound and calcium compound are completely reacted, and the crystallinity of the particles can be improved by heat-treating the produced particles. As a specific method, the produced slurry containing calcium-doped barium titanate is transferred into a reaction vessel or from a reaction vessel to an aging tank, and is treated at a predetermined temperature for a predetermined time.

  After the heat treatment, the calcium-doped barium titanate is washed to sufficiently remove unreacted compounds and alkali components, duplicated alkali salts, and the like, thereby separating the calcium-doped barium titanate. For this washing and separation, a general method such as decantation, centrifugation or filtration can be employed. After separation, it is dried by heating at 50 to 300 ° C. in air or in an inert gas, or by heating at 20 to 300 ° C. in a vacuum, finally removing alkali components, and calcium-doped barium titanate Purify the powder. Furthermore, in this invention, the calcium dope barium titanate powder obtained by the above-mentioned method can be heated at 1000-1300 degreeC, and crystallinity can also be improved.

  The calcium-doped barium titanate powder produced as described above has a certain spherical shape, ultrafine particles having an average particle size of 0.05 to 0.5 μm, a narrow particle size distribution, and good crystallinity. It is. Further, this calcium-doped barium titanate powder has a stable [Ca + Ba] / Ti atomic ratio at a high concentration and can stably control the content of each atom of Ca, Ba and Ti at a high concentration. It has excellent dispersibility when formed into a slurry or paste and has good sintering characteristics. Furthermore, this calcium-doped barium titanate powder has ferroelectricity.

(5) Other
The present invention includes an aqueous solution of one or more titanium compounds selected from halides, hydroxides, nitrates, sulfates, acetates, perchlorates and oxalates , halides, hydroxides, Select from a mixed aqueous solution of one or more calcium compound aqueous solutions selected from nitrates, sulfates, acetates and perchlorates , and halides, hydroxides, nitrates, sulfates and perchlorates An alkaline aqueous solution comprising one or more kinds of barium compounds and containing at least one of an alkali metal hydroxide and barium hydroxide as an alkali source in an alkaline aqueous solution comprising the alkali metal hydroxide. Also included is calcium-doped barium titanate, which is obtained by adding to and contacting. Moreover, in this calcium dope barium titanate, it is preferable that a calcium content rate is 4 mol or less with respect to 100 mol of barium titanates. Furthermore, the present invention includes a multilayer ceramic capacitor using the calcium-doped barium titanate.

Hereinafter, the present invention will be described by way of examples. In addition, the following aqueous solution was prepared with ion-exchange water.
<Example 1>
A 1.0 mol / l aqueous NaOH solution was poured in advance into a SUS reaction vessel equipped with a stirrer and maintained at 90 ° C. Next, a 0.5 mol / l TiCl ₄ aqueous solution previously maintained at 40 ° C. and a 0.03 mol / l CaCl ₂ aqueous solution were mixed, and this mixed solution was maintained at 40 ° C. In addition, a 3.0 mol / l NaOH aqueous solution having a BaCl ₂ concentration of 0.26 mol / l from which undissolved components had been removed in advance was prepared and heated to 95 ° C.

  Next, the mixed solution of the titanium compound and the calcium compound and the barium compound aqueous solution are reacted at a flow rate of 1 l / min and 2 l / min, respectively, in the reaction vessel in which the NaOH aqueous solution maintained at 90 ° C. is injected. It was continuously fed into the container. Next, the temperature in the reaction vessel during the reaction was kept at 90 ° C. and stirred for 2 minutes to produce calcium-doped barium titanate of Example 1 of the present invention. Thereafter, the produced slurry containing calcium-doped barium titanate was continuously extracted from the reaction vessel into an aging tank maintained at 90 ° C. and stirred for 5 minutes. Subsequently, decantation was performed to separate the supernatant and the precipitate, and centrifugation was performed. Thereafter, the operations of pure water washing, decantation, and centrifugation were performed several times, and the calcium-doped barium titanate powder of Example 1 was obtained. Obtained.

<Comparative Example 1>
A 1.0 mol / l aqueous NaOH solution was poured in advance into a SUS reaction vessel equipped with a stirrer and maintained at 90 ° C. Next, a mixed aqueous solution of a 0.5 mol / l TiCl ₄ aqueous solution, a 0.26 mol / l BaCl ₂ aqueous solution, and a 0.03 mol / l CaCl ₂ aqueous solution was prepared.

  Next, a mixed aqueous solution of the above three types of compounds and a 1.0 mol / l aqueous NaOH solution heated to 90 ° C. were continuously supplied into the reaction vessel at a flow rate of 1 l / min. Next, the temperature in the reaction vessel during the reaction was kept at 90 ° C., and the mixture was stirred for 2 minutes to produce calcium doped barium titanate of Comparative Example 1. Thereafter, the produced calcium-doped barium titanate was aged in the same manner as in Example 1, and then washed, decanted, and centrifuged to collect the calcium-doped barium titanate powder of Comparative Example 1.

<Comparative example 2>
A calcium-doped barium titanate powder of Comparative Example 2 was obtained in the same manner as in Comparative Example 1, except that ion-exchanged water was poured into a SUS reaction vessel equipped with a stirrer.

  For the calcium-doped barium titanate powders of Examples and Comparative Examples obtained as described above, the average particle size, CV value, atomic ratio of Ca, Ba and Ti were measured, and the dielectric properties were evaluated. These results are shown in Table 1 and Table 2. The average particle size, CV value, Ca, Ba and Ti atomic ratio and dielectric properties were measured and evaluated by the following methods.

(Average particle size, CV value)
The average particle diameter of the calcium-doped barium titanate powder was measured by an electron micrograph (SEM diameter). And based on this measured value, CV value (standard deviation of particle size / d50 (median diameter of particle size distribution)) was determined.

(Atomic ratio of Ca, Ba and Ti)
[Ca + Ba] / Ti atomic ratio and Ca / Ti atomic ratio of the calcium-doped barium titanate powder were determined by quantifying barium, calcium, and titanium by fluorescent X-ray analysis as follows.

(Dielectric properties)
Regarding the dielectric properties of the calcium-doped barium titanate powder, the calcium-doped barium titanate powders of the examples and comparative examples were fired at 1300 ° C. for 2 hours in a reducing atmosphere to produce a molded body having a thickness of 1.14 mm. The calcined formed body was measured for relative permittivity and dielectric loss (tan δ) with an LCR meter (frequency 1 KHz, applied voltage 1 V).

As is apparent from Table 1, the calcium-doped barium titanate of Example 1 has a lower particle size distribution due to its low CV value, and the [Ca + Ba] / Ti atomic ratio and the Ca / Ti atomic ratio are stable at a high concentration. From this, it was shown that the stability of the reaction was excellent. Moreover, Ca content is also contained in a predetermined amount, indicating that the content of each atom can be controlled with high accuracy. Furthermore, as is clear from Table 2, it was shown that the calcium-doped barium titanate of Example 1 has excellent dielectric properties. On the other hand, after the titanium compound aqueous solution, the barium compound aqueous solution and the calcium compound aqueous solution were previously contacted as a mixed aqueous solution, this was supplied into the alkaline aqueous solution, and the titanium compound aqueous solution, the barium compound aqueous solution and the calcium compound In Comparative Example 2 in which the aqueous solution was contacted in advance as a mixed aqueous solution and then supplied into the ion-exchanged water, the average particle size was slightly large and the CV value was high, so the particle size varied, and [Ca + Ba] / Ti The atomic ratio is lower than the example and less than 1, and the Ca / Ti atomic ratio is also lower than the example, indicating that the reaction is not sufficiently stable.

Claims (8)

In an alkaline aqueous solution, one or more titanium compound aqueous solutions selected from halides, hydroxides, nitrates, sulfates, acetates, perchlorates and oxalates , halides, hydroxides, One or more barium compound aqueous solutions selected from nitrates, sulfates, acetates, perchlorates , and halides, hydroxides, nitrates, sulfates, acetates, perchlorates In the method for producing calcium-doped barium titanate in which one or more calcium compound aqueous solutions are added and brought into contact with each other, the barium compound aqueous solution is added to the alkaline aqueous solution before the titanium compound aqueous solution and the calcium aqueous solution. and without mixing, added in the alkali aqueous solution, an aqueous solution wherein the titanium compound aqueous solution and the calcium compound, the barium Prior to mixing with the compound aqueous solution, calcium dope production method of barium titanate, characterized in Rukoto contacting a premixed aqueous solution. The method for producing calcium-doped barium titanate according to claim 1, wherein the barium compound aqueous solution is an alkaline aqueous solution of the barium compound. The aqueous alkali solution, separately from the barium compound in the barium compound aqueous solution, a calcium dope production method of barium titanate according to claim 1 or 2, characterized in that the addition of pre-barium compound. The method for producing calcium-doped barium titanate according to any one of claims 1 to 3, wherein the titanium compound is titanium tetrachloride. The method for producing calcium-doped barium titanate according to any one of claims 1 to 4, wherein the barium compound is at least one selected from barium chloride and barium hydroxide. 6. The calcium dope according to claim 1, wherein a mixed aqueous solution of the aqueous solution of the titanium compound and the aqueous solution of the calcium compound is prepared, and the mixed aqueous solution and the aqueous solution of the barium compound are brought into contact with each other. A method for producing barium titanate. The barium compound is a chloride, nitrate, sulfate, acetate, when a perchlorate, precontacted is a hydroxide of an alkali metal to the barium compounds, characterized in that the alkaline aqueous solution of a barium compound The manufacturing method of the calcium dope barium titanate in any one of Claims 1-6 . The method for producing calcium-doped barium titanate according to any one of claims 1 to 7, wherein the calcium content is 4 mol or less with respect to 100 mol of barium titanate.