JP6580931B2 - Method for producing barium titanate powder - Google Patents

Description

  The present invention relates to a method for producing perovskite-type barium titanate powder, and a method for producing perovskite-type barium titanate powder useful as a raw material for functional ceramics such as piezoelectrics, optoelectronic materials, dielectrics, semiconductors, and sensors. It is about.

  Perovskite-type barium titanate powder has been conventionally used as a raw material for functional ceramics such as piezoelectric bodies and multilayer ceramic capacitors. However, in recent years, multilayer ceramic capacitors have been required to have an increased number of layers and a higher dielectric constant in order to increase the capacity. For this reason, the perovskite-type barium titanate powder, which is the raw material, is fine and has a high squareness. It is desired to have crystallinity.

  One method for producing a perovskite barium titanate powder is to calcine a complex organic acid salt containing Ba atoms and Ti atoms. For example, an oxalate method in which a solution containing barium chloride and titanium chloride is contacted with an aqueous oxalic acid solution to obtain barium titanyl oxalate, and then the barium titanyl oxalate is calcined and deoxalated. Is representative. This oxalate method has a problem in that it is difficult to obtain a fine and highly tetragonal perovskite barium titanate powder.

For this reason, for example, in the following Patent Document 1, a water-soluble barium salt, a water-soluble titanium salt and an aqueous solution of oxalic acid are mixed at the same time, and the resulting gel is obtained by finely stirring and pulverizing in a short time A method has been proposed in which a crystal of barium titanyl oxalate (BaTiO (C ₂ O ₄ ) · H ₂ O) is calcined at 700 to 900 ° C.

  Patent Documents 2 and 3 below propose a method in which barium titanyl oxalate is wet-pulverized to obtain fine barium titanyl oxalate, and then calcined the barium titanyl oxalate obtained. .

  Further, in Patent Document 4 below, a mixed aqueous solution of a barium chloride aqueous solution and a titanium chloride aqueous solution is added to an oxalic acid aqueous solution to precipitate barium titanate oxalate, which is then aged, washed, filtered and dried to obtain barium titanium. A step of producing an acid oxalate; a step of first calcining the produced barium titanate oxalate, followed by a primary calcining to produce a fine barium titanate powder; and a secondary calcining of the fine barium titanate powder, A method having a step of secondary grinding has been proposed.

  Patent Document 5 below is a method for producing a barium titanate powder in which a titanium compound aqueous solution and a barium compound aqueous solution are contacted to obtain a solid reaction product, and then the solid reaction product is heat-treated while being contacted with water vapor. A method in which the titanate compound and the barium compound are oxalates has been proposed.

  In Patent Document 6 below, a perovskite-type barium titanate having fine and high tetragonal properties is obtained by calcining a complex organic acid salt containing Ba atoms and Ti atoms in the presence of humidified air in a firing furnace. A method for producing a powder has been proposed.

Japanese Patent Publication No. 61-146710 JP 2004-123431 A JP 2002-53320 A JP 2003-212543 A JP 2000-344519 A JP 2009-209002 A

  Various methods for producing perovskite-type barium titanate powders using complex organic acid salts such as the oxalate method using oxalate as in the prior art have been studied. Thus, there has been a demand for a method for producing a fine perovskite-type barium titanate powder having high tetragonal properties.

  Therefore, an object of the present invention is an industrially advantageous method for producing a perovskite-type barium titanate powder for firing a complex organic acid salt having Ba atoms and Ti atoms, and has a fine and high tetragonal property. The object is to provide a method for producing perovskite barium titanate powder.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that when a complex organic acid salt having Ba atoms and Ti atoms is fired, if a large amount of carbon dioxide gas is present in the firing atmosphere, the perovskite-type barium titanate Since barium carbonate is generated on the surface and inside of the powder, the ratio of c-axis to a-axis (c / a), which is an index of tetragonal crystal, is low, and the perovskite type barium titanate powder has low properties as a ferroelectric It is possible to produce a perovskite-type barium titanate powder that is fine and has high tetragonality even at the same firing temperature if the carbon dioxide gas concentration in the atmosphere during firing is reduced. In addition, if baking is performed with a large amount of superheated steam present in the atmosphere, carbon dioxide gas is effectively absorbed by the superheated steam, so that the carbon dioxide concentration in the atmosphere during firing is reduced. Because it reduced, it found that perovskite barium titanate powder with high tetragonality be fine and and the same firing temperature can be obtained, and have completed the present invention.

That is, in the present invention, a perovskite-type barium titanate powder is obtained by firing a complex organic acid salt having Ba atoms and Ti atoms at 600 to 1200 ° C. while supplying superheated steam at 200 to 1200 ° C. in a firing atmosphere. The present invention provides a method for producing a perovskite-type barium titanate powder, characterized by having a firing step.

  According to the present invention, it is possible to produce a perovskite-type barium titanate powder that is fine and has high tetragonality by an industrially advantageous method. The perovskite-type barium titanate powder produced by the method for producing a perovskite-type barium titanate powder of the present invention is used as a raw material for functional ceramics for electronic parts such as piezoelectrics, optoelectronic materials, dielectrics, semiconductors, and sensors. Useful.

1 is a schematic end view showing a firing furnace for carrying out an embodiment of a method for producing a perovskite-type barium titanate powder of the present invention.

  A method for producing the perovskite barium titanate powder of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing an end view of a firing furnace for carrying out an embodiment of the method for producing the perovskite-type barium titanate powder of the present invention.

  In the embodiment using the firing furnace 1 shown in FIG. 1, first, an alumina container containing a composite organic acid salt 5 containing Ba atoms and Ti atoms is placed in a firing furnace 1 covered with an alumina fiber board, and a lid 2 Close. Next, the inside of the firing furnace 1 is preheated. Next, while supplying the superheated steam 11 from the superheated steam supply pipe 7 into the firing furnace 1, the temperature in the firing furnace 1 is raised to a predetermined firing temperature, and after reaching the predetermined firing temperature, the firing furnace 1. While superheated steam 11 is supplied inside, baking is performed while maintaining the temperature. When the composite organic acid salt 5 having Ba atoms and Ti atoms is baked, barium titanate is generated by pyrolysis and carbon dioxide gas derived from organic acids is generated. The generated carbon dioxide gas is absorbed by surrounding superheated water vapor and becomes superheated water vapor 12 containing carbon dioxide gas, so that the superheated water vapor 12 containing carbon dioxide gas is discharged from the exhaust pipe 4. That is, in the embodiment using the firing furnace 1 shown in FIG. 1, firing is performed while supplying superheated steam 11 to the atmosphere and discharging superheated steam 12 containing carbon dioxide gas from the atmosphere.

  At this time, since the superheated steam 11 is continuously supplied into the firing furnace 1, the atmosphere to which the composite organic acid salt 5 having Ba atoms and Ti atoms is exposed is an atmosphere in which a large amount of superheated steam exists. In the embodiment using the firing furnace 1 shown in FIG. 1, the firing furnace 1 is not hermetically sealed and firing is performed in an open system. Therefore, although there is a little air in the firing atmosphere, superheated steam 11 is used in the firing atmosphere. By continuing to supply, the amount of air in the firing atmosphere can be greatly reduced. Moreover, it can also be set as a perfect superheated steam atmosphere by adjusting the supply amount of superheated steam. That is, by firing while supplying superheated steam to the firing atmosphere, the firing atmosphere of the complex organic acid salt having Ba atoms and Ti atoms can be changed to a superheated steam atmosphere or a completely superheated steam atmosphere with a very small amount of air. Firing can be performed in an atmosphere.

  If the carbon dioxide gas generated by firing is present around the generated barium titanate powder, the tetragonality is adversely affected. However, in the embodiment using the firing furnace 1 shown in FIG. Because of the large amount, carbon dioxide is absorbed by superheated steam. Therefore, in the embodiment using the firing furnace 1 shown in FIG. 1, adverse effects caused by carbon dioxide gas can be prevented. Further, in the embodiment using the firing furnace 1 shown in FIG. 1, since the air present in the firing atmosphere is very small, a side reaction caused by carbon dioxide can be prevented.

  The method for producing a perovskite barium titanate powder according to the present invention comprises calcining a composite organic acid salt having Ba atoms and Ti atoms at 600 to 1200 ° C. while supplying superheated steam to a firing atmosphere. It is a manufacturing method of the perovskite type barium titanate powder characterized by having a baking process which obtains barium powder.

  The firing step according to the method for producing a perovskite-type barium titanate powder of the present invention is a step of firing a composite organic acid salt having Ba atoms and Ti atoms to obtain a perovskite-type barium titanate powder.

  The complex organic acid salt having Ba atoms and Ti atoms in the firing process (hereinafter also referred to as Ba-Ti complex organic acid salt) is not particularly limited as long as it can form a condensed salt of Ba and Ti. For example, carboxylates such as formate, oxalate, acetate, propionate, succinate, malate, tartrate, citrate, lactate, or formic acid, oxalic acid, acetic acid, Examples include composite salts having two or more carboxylic acids such as propionic acid, succinic acid, malic acid, tartaric acid, citric acid, and lactic acid (see International Publication WO2008 / 102785 pamphlet). Specific examples include barium titanyl oxalate, barium titanyl citrate, and barium titanyl succinate. Among these, as the Ba-Ti complex organic acid salt, oxalate and citrate are preferable, and the oxalate is easy to manufacture with an atomic ratio of Ba / Ti in the vicinity of 1, and the manufacturing cost is low. This is particularly preferable.

  The molar ratio (Ba / Ti) of Ba to Ti in terms of atoms in the Ba-Ti composite organic acid salt is 0.99 to 1.01, preferably 0.995 to 1.005. When the molar ratio of Ba to Ti (Ba / Ti) is less than 0.99, titanium is rich and perovskite-type barium titanate with high tetragonality cannot be obtained. On the other hand, when it exceeds 1.01, it becomes barium-rich and tetragonal. Highly crystalline perovskite barium titanate cannot be obtained.

  The barium titanate obtained by performing the firing step is a perovskite type complex oxide in which the A site element is Ba and the B site element is Ti. The barium titanate obtained by performing the firing step may be a perovskite-type barium titanate in which the A site element is only Ba and the B site element is only Ti, or the Ba atom of the A site element Is partially substituted with either Ca or Sr or both of Ca and Sr, partially substituted Ti atom of B site element with Zr, or partially Ba atom of A site element May be substituted with either Ca or Sr or both of Ca and Sr, and a part of the Ti atom of the B site element may be substituted with Zr.

  In the method for producing perovskite-type barium titanate of the present invention, a perovskite-type titanic acid in which a part of the Ba atom of the A-site element is substituted with Ca or Sr, or a part of the Ti atom of the B-site element is substituted with Zr. In order to obtain barium, the Ba—Ti complex organic acid salt may have a Ca atom or a Sr atom as a partial substitute atom of the Ba atom, or may have a Zr atom as a partial substitute atom of the Ti atom. it can. When a part of Ba atom is substituted with either Ca or Sr or both of Ca and Sr, the content of Ca atom or Sr atom in Ba-Ti complex organic acid salt is not particularly limited, Therefore, the content is preferably such that the total ratio of Ca atoms and Sr atoms to Ba atoms is less than 50 mol%. When substituting a part of Ti atoms with Zr, the content of the compound having Zr atoms in the Ba-Ti complex organic acid salt is not particularly limited, but in terms of atoms, the ratio of Zr atoms to Ti atoms is 50 mol. A content of less than% is preferred. In the Ba-Ti complex organic acid salt, the molar ratio of the total of Ti atoms and Zr atoms as B site elements to the total of Ba atoms, Ca atoms and Sr atoms as A site elements in terms of atoms is 0.99 to 1.01, preferably 0.995 to 1.005.

  The average particle diameter of the Ba—Ti composite organic acid salt is preferably 200 μm or less, particularly preferably 100 μm or less. When the average particle diameter of the Ba—Ti composite organic acid salt is in the above range, it is easy to obtain a fine perovskite-type barium titanyl titanate having high tetragonal properties. In addition, in this invention, an average particle diameter is calculated | required by scanning electron microscope (SEM) observation, and shows the average value of 1000 samples arbitrarily extracted with the SEM image of scanning electron microscope observation (SEM).

  The manufacturing method in particular of Ba-Ti complex organic acid salt is not restrict | limited, For example, it can obtain by a well-known method. When the Ba-Ti complex organic acid salt is an oxalate, for example, an aqueous solution containing titanium chloride and barium chloride is brought into contact with an aqueous oxalic acid solution to precipitate the oxalate, and if necessary, ripening is performed. The solid and liquid are separated and recovered, and if necessary, washing, drying, pulverization and the like are performed to obtain a complex oxalate of Ba and Ti. Moreover, as a manufacturing method of Ba-Ti composite oxalate, it describes in Unexamined-Japanese-Patent No. 2006-321722, Unexamined-Japanese-Patent No. 2006-321723, Unexamined-Japanese-Patent No. 2006-348026, Unexamined-Japanese-Patent No. 2004-123431, etc. The method is mentioned.

  Further, when the Ba-Ti complex organic acid salt is a citrate, for example, a solution of barium chloride is added to a citric acid solution of titanium, a citrate is precipitated, and aged as necessary. A combined citrate of Ba and Ti can be obtained by solid-liquid separation and recovery, and if necessary, washing, drying, pulverization and the like. Moreover, as a manufacturing method of Ba-Ti composite citrate, the method described in US Patent 3,231,328 etc. is mentioned, for example.

  Further, when the Ba-Ti complex organic acid salt is a carboxylic acid complex salt having both oxalic acid and lactic acid, for example, a solution containing a titanium component, a barium component and a lactic acid component, and a solution containing an oxalic acid component, By making it react by making it contact in the solvent containing alcohol, the complex salt of the oxalic acid and lactic acid containing Ba and Ti can be obtained (for example, international publication WO2008 / 102785 pamphlet).

  After the Ba—Ti composite organic acid salt is produced by the method as mentioned above, the Ba—Ti composite organic acid salt can be pulverized for the purpose of adjusting the particle diameter. As the pulverization method, a wet method is preferable, and for example, a method of pulverizing a slurry containing a Ba—Ti composite organic acid salt using a wet pulverizer can be used. Examples of the wet pulverizer include a ball mill and a bead mill. Examples of the solvent used in the wet method include water, methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methylene chloride, ethyl acetate, dimethylformamide, and diethyl ether. Among these, organic solvents such as methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methylene chloride, ethyl acetate, dimethylformamide, diethyl ether, and the like that have low elution of Ba and Ti are highly crystalline perovskites. Type barium titanate powder is preferred in that it is obtained. In addition, after pulverizing by a wet method, the slurry can be dried by a spray dryer.

  In order to obtain a high-purity perovskite-type barium titanate powder, the Ba-Ti composite organic acid salt is preferably as high as possible.

  And in a baking process, Ba-Ti compound organic acid salt is baked. The firing temperature in the firing step is 600 to 1200 ° C, preferably 700 to 1000 ° C. If the firing temperature is less than the above range, a solid phase reaction that changes to perovskite-type barium titanate does not occur and tends to remain unreacted. On the other hand, if it exceeds the above-mentioned range, the generated perovskite-type barium titanate Because it causes grain growth, it is not possible to obtain a fine one. The firing time in the firing step is 4 hours or more, preferably 6 to 30 hours. Moreover, in a baking process, after baking once at 600-1200 degreeC, Preferably 700-1000 degreeC, after grind | pulverizing a baked material and granulating as needed, it is further 600-1200 degreeC, Preferably it is 700- Firing may be performed at 1000 ° C. Further, in order to make the powder characteristics uniform, once fired ones may be pulverized and fired again.

  Examples of the firing furnace used in the firing step include a batch type or continuous type electric furnace and a gas furnace, and examples thereof include a roller hearth kiln, a rotary kiln, and a pusher furnace.

  In the firing step, the Ba—Ti composite organic acid salt is fired at 600 to 1200 ° C., preferably 700 to 1000 ° C., carbon dioxide gas such as carbon dioxide generated by reaction from the firing atmosphere while supplying superheated steam to the firing atmosphere. It is carried out while discharging superheated steam containing water.

Superheated steam refers to colorless and transparent H ₂ O gas obtained by further heating saturated steam at 100 ° C. under normal pressure. Since superheated steam maintains a saturated state of water in air at high temperatures, carbon dioxide generated during the production of barium titanate is effectively superheated by firing while supplying superheated steam to the firing atmosphere. The reaction can proceed without lowering the firing temperature while being absorbed by water vapor. In addition, since most of the fired atmosphere is superheated steam, side reactions due to the presence of carbon dioxide in the air can be suppressed.

  Since superheated steam is obtained by further heating saturated steam at 100 ° C. at normal pressure, the method of firing while supplying superheated steam to the firing atmosphere can perform the reaction under atmospheric pressure, There is no need to carry out in a firing furnace.

  In the firing step, the temperature of the superheated steam supplied to the firing atmosphere is preferably 200 to 1200 ° C, particularly preferably 300 to 1000 ° C. If the temperature of the superheated steam is less than the above range, the firing temperature is difficult to decrease.If the temperature exceeds the above range, the firing temperature can be prevented from decreasing, but the energy for generating the superheated steam increases. Manufacturing cost increases.

  As a method for generating superheated steam, saturated steam obtained by heating water to 100 ° C. or higher is heated directly or indirectly by a fuel such as oil or gas, or heating means such as infrared rays, electromagnetic waves, or microwaves. The method of heating with is mentioned. Examples of such superheated steam generation means include Tokuden Corporation UPSS series, Fuji Electric Co., Ltd. IHSS series, Nippon Thermoelectric Co., Ltd. superheated steam generator, Shinthermal Industry Co., Ltd. Can be mentioned.

  The amount of superheated steam supplied to the firing atmosphere is appropriately selected, but is preferably 5 L / min or more per kg of Ba-Ti complex organic acid salt, more preferably 10 to 200 L per kg of Ba-Ti complex organic acid salt. / Min, particularly preferably 15 to 100 L / min per kg of Ba-Ti complex organic acid salt. By supplying the amount of superheated steam to the firing atmosphere in the above range, it is possible to efficiently absorb the carbon dioxide gas generated in the firing furnace in the reaction and prevent the furnace temperature from being lowered by the superheated steam. it can. Although it is the time to introduce superheated steam into the firing furnace, it is possible to introduce superheated steam into the firing furnace before at least the perovskite-type barium titanate is generated by the reaction of the Ba-Ti composite organic acid salt. This is preferable in that it effectively absorbs carbon dioxide gas generated in the reaction process and can suppress the occurrence of adverse effects due to carbon dioxide gas.

  After performing the firing step, if necessary, the perovskite-type barium titanate powder after firing is washed with an acid solution, washed with water, dried, pulverized, classified, and the like to obtain a product. The drying method is not particularly limited as long as a conventional method is used, but when wet pulverization is performed, for example, a method using a spray dryer can be applied.

The perovskite-type barium titanate powder obtained by carrying out the method for producing the perovskite-type barium titanate powder of the present invention has a high tetragonality and a ratio of the c-axis to the a-axis (c / a) serving as a tetragonal index. However, it is preferably 1.004 or more, and particularly preferably 1.006 to 1.010. The average particle size of the perovskite-type barium titanate powder obtained by performing the production method of the perovskite-type barium titanate powder of the present invention is an average particle size determined by observation with an electron microscope, preferably 0.5 μm or less. The BET specific surface area is preferably 2 m ² / g or more, particularly preferably 3 to ²⁰ m ² / g. The perovskite-type barium titanate powder obtained by carrying out the method for producing the perovskite-type barium titanate powder of the present invention has a very high purity and is used for electronic parts such as piezoelectrics, optoelectronic materials, dielectrics, semiconductors and sensors. It is useful as a raw material for functional ceramics.

  In the method for producing a perovskite-type barium titanate powder according to the present invention, when producing a Ba—Ti composite organic acid salt, if necessary, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu , Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and other rare earth elements, Li, Bi, Zn, Mn, Al, Si, Sr, Co, V, Nb, Ni, Cr, B, Fe and Mg A sub-component element-containing compound containing at least one element selected from the following is mixed with a reaction raw material to obtain a Ba—Ti composite organic acid salt having these sub-component elements, and the resulting Ba—Ti composite organic acid salt is obtained. It is fired in a firing step as a firing raw material, or Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm Rare earth elements such as Yb, Lu A subcomponent element-containing compound containing at least one element selected from Li, Bi, Zn, Mn, Al, Si, Sr, Co, V, Nb, Ni, Cr, B, Fe and Mg, By firing the resulting mixture in the firing step, perovskite-type barium titanate containing an oxide of a subcomponent element can be obtained.

  The kind and mixing amount of these subcomponent element-containing compounds are arbitrarily selected according to the dielectric properties required for the barium titanate powder for production purposes. A specific addition amount of the subcomponent element-containing compound is 0.1 to 5 parts by mass in terms of atoms in the subcomponent element-containing compound with respect to 100 parts by mass of the perovskite-type barium titanate powder. The subcomponent element-containing compound may be either an inorganic substance or an organic substance. Examples thereof include oxides, hydroxides, chlorides, nitrates, oxalates, carboxylates and alkoxides containing the above-mentioned subcomponent elements. When the subcomponent element-containing compound is a compound containing Si element, silica sol, sodium silicate, or the like is also used.

  The perovskite-type barium titanate powder obtained by the method for producing a perovskite-type barium titanate powder of the present invention is used as a raw material for producing a multilayer capacitor. For example, first, a perovskite-type barium titanate powder obtained by the method for producing a perovskite-type barium titanate powder of the present invention is mixed with conventionally known compounding agents such as additives, organic binders, plasticizers, and dispersants. Then, it is dispersed to form a slurry, and a solid material in the resulting slurry is formed to obtain a ceramic sheet. Next, a conductive paste for forming an internal electrode is printed on one surface of the ceramic sheet, and after drying, a plurality of ceramic sheets are laminated, and then pressed in the thickness direction to form a laminate. Furthermore, this laminate is heat treated to remove the binder, and fired to obtain a fired body. Thereafter, an In—Ga paste, Ni paste, Ag paste, nickel alloy paste, copper paste, copper alloy paste or the like is applied to the fired body and baked, whereby a multilayer capacitor can be obtained.

  Further, perovskite-type barium titanate powder obtained by the method for producing a perovskite-type barium titanate powder of the present invention is blended in a resin such as an epoxy resin, a polyester resin, a polyimide resin, etc. As an agent or the like, it can be suitably used for materials such as printed wiring boards and multilayer printed wiring boards. Further, the perovskite-type barium titanate powder is a dielectric material for an EL element, a co-material for suppressing a shrinkage difference between an internal electrode and a dielectric layer, a base material and a circuit for an electrode ceramic circuit board and a glass ceramic circuit board. It is suitably used as a raw material for peripheral materials, a catalyst used in reactions such as exhaust gas removal and chemical synthesis, and a surface modifier for printing toner that imparts an antistatic effect and a cleaning effect.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
In the examples, the average particle diameter was determined as an average value obtained from observation with a scanning electron microscope (SEM) for 1000 samples extracted arbitrarily. The Ba / Ti molar ratio was calculated based on the value obtained by X-ray fluorescence analysis.

<Preparation of barium titanyl oxalate>
A mixed solution in which 600 g (2.456 mol) of barium chloride dihydrate and 444 g (2.342 mol) of titanium tetrachloride were dissolved in 4100 ml of water was prepared. Next, 620 g of oxalic acid was dissolved in 1500 ml of warm water at 70 ° C. to prepare an aqueous oxalic acid solution, which was designated as solution B. The liquid B was added to the liquid A over 120 minutes with stirring while maintaining the liquid at 70 ° C., and further aged with stirring at 70 ° C. for 1 hour. After cooling, it was filtered to recover barium titanyl oxalate. Next, the recovered barium titanyl oxalate was repulped with 4.5 L of distilled water three times and washed. Next, it was dried at 105 ° C. and pulverized to obtain 1000 g of barium titanyl oxalate (BaTiO (C ₂ O ₄ ) · 4H ₂ O). The obtained barium titanyl oxalate had an average particle size of 25 μm and a Ba / Ti molar ratio of 1.00.

(Examples 1-3)
In the firing furnace comprising the electric batch furnace shown in FIG. 1, the barium titanyl oxalate sample 50g was heated to the temperature shown in Table 1 at a heating rate of 2.5 ° C./min in the atmosphere and started firing. did. At the start of firing, superheated steam heated to the temperature shown in Table 1 was introduced into the firing furnace at a rate of 4 L / min and fired for 6 hours. After the completion of firing, the mixture was cooled and pulverized to obtain a barium titanate powder.

(Comparative Examples 1-3)
In the same manner as in Example 1, 50 g of a barium titanyl oxalate sample was heated to the temperature shown in Table 1 at a heating rate of 2.5 / min in an electric batch furnace and fired for 6 hours. Firing was performed in a normal atmosphere without introducing superheated steam into the firing furnace. After the completion of firing, the mixture was cooled and pulverized to obtain a barium titanate powder.

(Comparative Examples 4-6)
In the same manner as in Example 1, 50 g of a barium titanyl oxalate sample was heated to a temperature shown in Table 1 at a heating rate of 2.5 ° C./min in an electric batch furnace, and baked for 6 hours. In addition, it baked, introducing the humidified air (dew point 21 degreeC) humidified through the water heated at 30 degreeC into the baking furnace at the rate of 4 L / min with the start of baking. After the completion of firing, the mixture was cooled and pulverized to obtain a barium titanate powder.

<Evaluation of physical properties of barium titanate samples>
For the barium titanate samples obtained in Examples 1 to 3 and Comparative Examples 1 to 6, the average particle diameter, the BET specific surface area, and the ratio of c axis to a axis (c / a) serving as an index of tetragonal crystal were measured. . The results are shown in Table 2. The ratio of c axis to a axis was determined by X-ray diffraction.

  From Table 2, the barium titanate obtained by carrying out calcination by introducing superheated steam has the same c-axis as a tetragonal index compared to that obtained by calcination without introducing superheated steam at the same calcination temperature. It can be seen that the ratio of c to a axis (c / a) is high and the tetragonality is excellent.

  Since the present invention can produce a perovskite-type barium titanate powder that is fine and has high tetragonal crystallinity, the produced perovskite-type barium titanate powder includes, in particular, piezoelectric materials, optoelectronic materials, dielectric materials, It can be used as a raw material for functional ceramics for electronic parts such as semiconductors and sensors.

DESCRIPTION OF SYMBOLS 1 Firing furnace 2 Lid 4 Exhaust pipe 5 Raw material mixture containing barium carbonate and titanium dioxide 7 Superheated steam supply pipe 11 Superheated steam 12 Superheated steam containing carbon dioxide

Claims (3)

A baking step of obtaining a perovskite-type barium titanate powder by firing a complex organic acid salt having Ba atoms and Ti atoms at 600 to 1200 ° C. while supplying superheated steam at 200 to 1200 ° C. in a firing atmosphere ; A method for producing a perovskite-type barium titanate powder characterized by Method for producing a perovskite-type barium titanate powder of claim 1 Symbol placement, wherein the composite organic acid salt is a carboxylic acid salt. Method for producing a perovskite-type barium titanate powder of claim 1 Symbol placement, wherein the composite organic acid salt is an oxalate salt.