JP2005213070A - Method of manufacturing oxide powder having perovskite structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing oxide powder having perovskite structure which is a simple manufacturing method and by which the powder having small average particle diameter and uniform particle diameter is obtained to cope with a thin layered element, the content of coarse particles is remarkably decreased and excellent tetragonality and crystallinity are attained. <P>SOLUTION: The method of manufacturing the oxide powder having the perovskite structure has a calcining process for calcining a mixture of at least 2 kinds of main raw material powder. The calcining process has a temperature rising part as a 1st step for gradually raising a calcining temperature, a high temperature keeping part as a 2nd step for keeping a fixed high temperature after temperature rising and a temperature dropping part as a 3rd step for gradually dropping the temperature kept high and is constituted so that carbon dioxide (CO<SB>2</SB>) is introduced into an initial air treatment atmosphere in the temperature-rising part as the 1st step. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an oxide powder (for example, barium titanate powder) having a perovskite structure used as a material for forming a dielectric layer of a multilayer chip capacitor, for example.

  Oxides having a perovskite structure, such as barium titanate, are used as dielectric materials for electronic components such as multilayer chip capacitors (multilayer ceramic capacitors).

  In recent years, when such an oxide having a perovskite structure is used as a dielectric material (dielectric raw material powder), it is a raw material powder having a small particle diameter and high tetragonality and crystallinity. It is requested. This is because in a multilayer chip capacitor, it is necessary to make the thickness of the dielectric layer (dielectric ceramic layer) as thin as possible in order to reduce the size and increase the capacity.

  For example, in order to improve the tetragonality and crystallinity of the barium titanate powder, it is effective to increase the calcining temperature and lengthen the calcining time in the so-called solid phase reaction method. It is said that. That is, after mixing a barium compound such as barium carbonate and a titanium oxide such as titanium dioxide to form a pellet, it is said that an operation of increasing the calcining temperature and extending the calcining time is effective. .

  In addition, proposals have been made to obtain fine and crystallized barium titanate powder by adjusting the pressure of the calcining atmosphere and the partial pressure of oxygen.

  However, under such high-temperature and long-time calcining conditions, the generation of coarse grains due to grain growth and neck growth between grains usually occur, and the resulting barium titanate powder is refined and the grain size is uniform. There has been a problem that it is difficult to make it easier. Further, in the method of adjusting the pressure of the calcining atmosphere and the oxygen partial pressure, there are restrictions on the type of furnace that can be used, the operation becomes extremely complicated, and it can be said that it is difficult to obtain a powder having stable physical properties.

JP 2002-255552 A JP 2001-316114 A

  The present invention has been invented under such circumstances, and its purpose is a simple manufacturing method, in which the average particle size is small and uniform so as to cope with the thinning of the device. It is an object of the present invention to provide a method for producing an oxide powder having a perovskite structure having a diameter, a very small content of coarse particles, and having excellent tetragonality and crystallinity.

  As a result of the inventors' diligent research on the calcining atmosphere of the calcining, it is excellent in tetragonality and crystallinity by positively changing the calcining atmosphere in the temperature raising portion to a carbon dioxide atmosphere. In addition, the inventors have found that an oxide powder having a perovskite structure having a uniform particle size with a small average particle size and a sharp particle size distribution can be obtained, and the present invention has been conceived.

That is, the present invention provides a raw material preparation step of preparing at least two or more main raw material powders when producing an oxide powder having a perovskite structure, and a mixing step of mixing these at least two or more main raw material powders. A calcining step of calcining at least two or more mixed main raw material powders, wherein the calcining step gradually increases the calcining temperature. As a first stage of temperature rise, a high temperature holding part as a second stage for maintaining a constant high temperature after the temperature rise, and as a third stage of gradually lowering the held high temperature And a temperature lowering section, and configured to introduce carbon dioxide (CO ₂ ) into the initial air treatment atmosphere in the temperature raising section as the first stage.

As a preferred embodiment of the present invention, carbon dioxide (CO ₂ ) is introduced only into the treatment atmosphere in the temperature raising section as the first stage, and the high temperature holding section as the second stage and the temperature lowering section as the third stage. In the processing atmosphere, carbon dioxide (CO ₂ ) is not introduced.

  As a preferred embodiment of the present invention, the treatment atmosphere in the high temperature holding section as the second stage and the temperature lowering section as the third stage is configured to be an air atmosphere.

As a preferred embodiment of the present invention, carbon dioxide (CO ₂ ) introduced into the treatment atmosphere in the temperature raising section as the first stage is introduced so as to completely replace the furnace atmosphere.

Moreover, as a preferable aspect of the present invention, the introduction start timing of the carbon dioxide (CO ₂ ) is configured such that the temperature of the temperature raising portion is within a temperature range of room temperature to 650 ° C.

As a preferred embodiment of the present invention, the main raw material powder is ABO ₃ (A is at least one selected from the group of Ba, Sr, Ca, and B is at least one selected from the group of Ti, Zr. The compound powder constituting the A site and the compound powder constituting the B site of the perovskite structure oxide represented by

  As a preferred embodiment of the present invention, the oxide powder having a perovskite structure is a barium titanate powder, and the main raw material powder is a titanium compound and a barium compound.

  As a preferred embodiment of the present invention, the barium compound of the main raw material powder is configured to contain a carbonate.

  As a preferred embodiment of the present invention, the oxide powder having a perovskite structure is used to form a dielectric layer of a multilayer chip capacitor having an element body in which dielectric layers and internal electrode layers are alternately laminated. Configured to be used.

  The multilayer chip capacitor of the present invention is a multilayer chip capacitor having an element body in which dielectric layers and internal electrode layers are alternately laminated, and is an oxide used for forming the dielectric layer. The powder is configured as an oxide powder formed by the above manufacturing method.

The present invention provides a raw material preparation step of preparing at least two kinds of main raw material powders when producing an oxide powder having a perovskite structure, a mixing step of mixing these at least two kinds of main raw material powders, A calcining step of calcining at least two kinds of main raw material powders, wherein the calcining step gradually raises the calcining temperature. A temperature raising unit as a first stage, a high temperature holding part as a second stage for maintaining a constant high temperature after the temperature rise, and a temperature lowering part as a third stage for gradually lowering the held high temperature And is configured to introduce carbon dioxide (CO ₂ ) into the initial air treatment atmosphere in the temperature raising section as the first stage. Thin Average particle size is small and uniform particle diameter is obtained to accommodate the reduction. The content of coarse particles is also very low. Excellent tetragonality and crystallinity.

  Embodiments of the present invention will be described below.

  First, before describing the method for producing an oxide powder having a perovskite structure according to the present invention, a dielectric layer (dielectric ceramic) which is one of preferred applications of the oxide powder produced by the production method of the present invention. A schematic configuration of a general multilayer chip capacitor including a layer will be described with reference to FIGS.

  FIG. 1 is a perspective view showing an embodiment of a multilayer chip capacitor, FIG. 2 is a cross-sectional view of the multilayer chip capacitor shown in FIG. 1, taken along line AA, and FIG. It is the perspective view which showed an example for demonstrating easily the formation process of.

  A multilayer chip capacitor 1 as a preferred example shown in FIGS. 1 to 3 includes an element body 2 in which first internal electrode layers 23 and second internal electrode layers 28 are alternately stacked via dielectric layers 7. And a pair of external electrodes 11 and 15 provided on the opposing end faces of the element body 2. The dielectric layer 7 is one of the preferred applications of the oxide powder produced by the production method of the present invention.

  The element body 2 is usually a rectangular parallelepiped shape, but the shape is not particularly limited. Also, the dimensions of the element body 2 are not particularly limited and can be appropriately set according to the application. For example, (0.6 to 5.6 mm) × (0.3 to 5.0 mm) × (0.3 ˜2.5 mm).

  The internal electrode layers 23 and 28 are constituted by the first internal electrode layers 23 and the second internal electrode layers 28 that are alternately stacked via the dielectric layer 7 as described above. A preferred example for forming such a structure is shown in FIG. 3, according to which a sheet body 73 having a dielectric layer 7 and a first internal electrode layer 23, a dielectric layer 7 and a first layer. The sheet body 78 having the two internal electrode layers 28 is sequentially and repeatedly laminated in multiple layers.

  As shown in FIG. 3, the laminated first internal electrode layer 23 has a connection portion 23 a exposed to the first external electrode 11 side, and this connection portion 23 a is connected to the first external electrode 11. . As shown in FIG. 3, the first internal electrode layer 23 is exposed to the dielectric layer 7 so that the portion exposed from the outer peripheral frame of the dielectric layer 7 is only the connection portion 23a (more precisely, the end of the connection portion). Part only).

  On the other hand, the laminated second internal electrode layer 28 has a connection portion 28a exposed to the second external electrode 15 side as shown in FIG. 3, and this connection portion 28a is connected to the second external electrode 15. Has been. As shown in FIG. 3, the second internal electrode layer 28 is in a relationship with the dielectric layer 7 so that the portion exposed from the outer peripheral frame of the dielectric layer 7 is only the connection portion 28a (more precisely, the connection portion 28a End only).

  As described above, the oxide powder having a perovskite structure, which is an object of the production method of the present invention, is preferably used as a material for forming the dielectric layer 7.

  Hereinafter, the manufacturing method of the oxide powder which has the perovskite structure of this invention is demonstrated according to process order.

[Step of preparing at least two kinds of main raw material powders when producing an oxide powder having a perovskite structure]
The main raw material powder is composed of a compound powder constituting the A site of an oxide having a perovskite structure represented by ABO ₃ and a compound powder constituting the B site. A represents at least one selected from the group of Ba, Sr and Ca, and B represents at least one selected from the group of Ti and Zr.

  In general, a metal oxide powder and a metal carbonate powder are often used as the main raw material when producing an oxide powder having a perovskite structure.

  As an oxide powder having a perovskite structure, barium titanate powder is taken as a preferred example and described below.

In order to obtain a barium titanate powder that is an oxide powder having a perovskite structure, first, a barium compound powder that generates barium oxide by thermal decomposition is prepared. As this barium compound, for example, barium carbonate (BaCO ₃ ) can be suitably used. The specific surface area is preferably in the range of 5 to 40 m ² / g. Barium chloride (BaCl ₂ ) or barium hydroxide (Ba (OH) ₂ ) may be used by mixing with barium carbonate or instead of barium carbonate.

  Moreover, when mixing and using 2 or more types of barium compounds containing barium carbonate, it is preferable that the content rate of barium carbonate shall be 50 mol% or more.

Titanium dioxide is prepared as the metal oxide powder. This can be obtained, for example, by thermally decomposing titanium tetrachloride. The specific surface area is preferably in the range of 10 to 50 m ² / g.

[Process of mixing main raw material powder]
The metal oxide powder exemplified by the titanium dioxide and the metal carbonate powder exemplified by the barium carbonate are weighed and mixed so as to have a predetermined molar ratio. The Ba / Ti ratio is about 0.990 to 1.020.

  In mixing, wet mixing is preferably performed by adding water to the raw material powder. As a more specific preferred example, it is desirable that the powder to be mixed is placed in a ball mill together with water and zirconia balls and mixed in a wet manner for 16 hours or more.

  The slurry obtained by such mixing is usually dried to form a mixed powder.

[Step of calcining mixed main raw material powder]
The mixed powder obtained in the mixing step is usually molded into a pellet by pressure molding, but the mixed powder may be used as it is. The pressure molding is usually performed after water or the like is added to the mixed powder so as to enable molding.

  The molded pellets are calcined. The first essential part of the present invention is the processing conditions in the calcining step, which will be described in detail below.

  The temperature operation conditions over time in the calcining step are (1) a temperature raising section as a first stage for gradually raising the calcining temperature, and (2) a second stage for maintaining a constant high temperature after the temperature rise. And (3) a temperature lowering part as a third stage for gradually lowering the held high temperature. Such a series of steps is a step normally operated in the calcining process.

In the calcining step of the present invention, carbon dioxide (CO ₂ ) is introduced into the initial air treatment atmosphere in the temperature raising section as the first stage. In particular, carbon dioxide (CO ₂ ) is introduced only into the processing atmosphere in the temperature raising section as the first stage, and carbon dioxide is introduced into the processing atmosphere in the high temperature holding section as the second stage and the temperature lowering section as the third stage. Desirably, (CO ₂ ) is not introduced.

The concentration of carbon dioxide (CO ₂ ) in the furnace by carbon dioxide (CO ₂ ) introduced into the treatment atmosphere of the temperature raising section as the first stage is 4 to 100 Vol%, preferably 20 to 100 Vol%, more preferably Is preferably in the range of 50 to 100 Vol%. In particular, an operation that completely replaces the atmosphere in the furnace is preferable (that is, carbon dioxide (CO ₂ ) is 100 Vol%).

The carbon dioxide (CO ₂ ) introduction start time is such that the temperature of the temperature raising portion is room temperature (synonymous with the temperature at which the temperature raising operation is started and is usually about 25 ° C.) or higher, particularly 400 ° C. or higher, and further 550 to 650 ° C. It is preferable to carry out when the temperature is within the above temperature range. Moreover, it is preferable that the carbon dioxide (CO ₂ ) atmosphere once formed is continued until reaching the high temperature holding portion. The temperature raising rate of such a temperature raising part is preferably about 100 to 300 ° C./hr.

The treatment atmosphere in the high temperature holding section as the second stage and the cooling section as the third stage may be an air atmosphere by stopping the introduction of carbon dioxide (CO ₂ ).

  The temperature of the high temperature holding part as the second stage is 800 to 1200 ° C, particularly 900 to 1100 ° C, particularly preferably 950 to 1000 ° C, and more preferably 950 to 985 ° C. When this temperature value exceeds 1200 ° C., grain growth becomes active, the particle size itself becomes large, and the mixture ratio of coarse grains tends to increase. Moreover, when this temperature value is less than 800 ° C., the crystallinity tends to deteriorate.

  In the high-temperature holding unit as the second stage, normally, long-time holding at a constant temperature is performed, and the holding time is 1 to 10 hr, preferably 2 to 5 hr.

  When the high temperature holding process as the second stage is completed, the temperature lowering process in the temperature lowering section as the third stage is performed. The cooling rate of the temperature lowering portion is about 100 to 300 ° C./hr.

  Moreover, there is no restriction | limiting in particular about the pressure in the process atmosphere in a calcination process, Usually, it is set as atmospheric pressure.

[Step of wet pulverizing oxide having perovskite structure formed by calcining in solution]
The calcined pellets are crushed by, for example, a pulverizer or the like as necessary, and then subjected to wet pulverization.

  The wet pulverization is preferably performed in a solution (solvent) having a pH of 7.0 to 13.0, particularly 8.5 to 12.5 (particularly preferably 9.7 to 12.1). That is, the crushed oxide having a perovskite structure is put in a solvent prepared within the above pH range, and wet pulverized in a ball mill together with zirconia balls. In addition to the ball milling method, a grinding method such as a planetary mill or a vibration mill may be used.

  The pH adjusting means of the solution (solvent) is not particularly limited, but as the adjustment to the alkali side, for example, it is convenient and preferable to employ a method of adjusting by adding aqueous ammonia to water. By optimizing the pH adjustment, the c / a ratio with respect to the specific surface area and ΔH (111) can be improved.

  The slurry concentration (solid content concentration) in wet pulverization is, for example, about 10-30 wt%, and the pulverization time is, for example, about 12-60 hr.

The oxide powder (barium titanate powder) having a perovskite structure thus obtained is made into a sintered body through a firing step, for example, the dielectric layer (dielectric ceramic) of the multilayer chip capacitor described above, for example. ) Can be suitably used. As an example of firing conditions in the firing step, the firing temperature is 1100 to 1400 ° C., the firing time is 1 to 5 hours, and the firing atmosphere is an atmosphere having an oxygen partial pressure of 10 ⁻² to 10 ⁻¹⁵ MPa.

  When forming the dielectric layer (dielectric ceramic), additives such as Ca, rare earth elements including Sc, Y, Zr, Mn, Mg, and Si may be added to the oxide powder having the perovskite structure. it can.

  In the above description, barium titanate synthesized using titanium dioxide and barium carbonate is shown as a preferred example as an oxide powder having a perovskite structure. It can also be applied to methods for producing oxide powders having other perovskite structures such as strontium oxide, lead titanate, lead zirconate, barium zirconate, calcium zirconate, strontium zirconate, and complex oxides thereof. It is.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

(Example 1-1)
Was prepared titanium dioxide powder having a specific surface area of 5.7 m ² / g barium carbonate powder and a specific surface area of 22.3 m ² / g. Titanium dioxide powder is produced by thermal decomposition of titanium tetrachloride.

  The barium carbonate powder and the titanium dioxide powder were weighed so that the molar ratio of barium carbonate to titanium dioxide was 1.005: 1.000.

Subsequently, these raw material powders were placed in a ball mill together with water and zirconia balls, and mixed in a wet manner for 16 hours. The obtained slurry (mixture) was put into a dryer and dried at 120 ° C. to obtain a mixed powder. Next, 10 wt% of water was added to the obtained mixed powder, and this was put into a mold and subjected to pressure molding to obtain a pellet (molded product). Next, the pellets were calcined under the conditions shown below. As the calcining furnace for calcining, a 100 mm diameter alumina tubular furnace was used.
Temporary firing conditions

The temperature was raised at a rate of temperature increase of 200 ° C./hr until the temperature rose from room temperature to 975 ° C. (high temperature holding temperature). At first, an air atmosphere (air flow rate = 2 liters / min) is started, and when the temperature rises to 550 ° C., the introduction of carbon dioxide is started, and the firing atmosphere is completely replaced with the carbon dioxide atmosphere from the air atmosphere (CO ₂ gas). The flow rate was 2 liters / min), and this state was continued until reaching 975 ° C. That is, the range of 550 to 975 ° C. in the temperature raising portion was set to 100 Vol% carbon dioxide atmosphere.

When reaching the high temperature holding part 975 ° C. (high temperature holding temperature), the introduction of carbon dioxide was stopped, and instead, the introduction of air was started, and the firing atmosphere was completely replaced from the carbon dioxide atmosphere to the air atmosphere (air) (Flow rate = 2 liter / min and 100 vol% air atmosphere). This state was continued for a high temperature of 975 ° C., that is, for 2 hours.

After completion of the treatment in the temperature- falling portion high-temperature holding portion, the temperature was lowered at a cooling rate of 200 ° C./hr. The atmosphere in this case was the same 100 Vol% air atmosphere as that in the high temperature holding section (air flow rate = 2 liters / min).

  After such a calcination step, the obtained pellet-like material was crushed to obtain barium titanate powder of Example Sample 1-1.

(Comparative Example 1-1)
In Example 1-1, the carbon dioxide was not replaced in the temperature raising portion under the calcining conditions. That is, all the firing atmospheres of the temperature raising portion, the high temperature holding portion, and the temperature lowering portion were 100 vol% air atmosphere. Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of the comparative example sample 1-1.

(Comparative Example 1-2)
In Example 1-1, the carbon dioxide was not replaced in the temperature raising portion under the calcining conditions. Instead, carbon dioxide was replaced in the high temperature holding section. That is, all the firing atmospheres of the temperature raising part and the temperature lowering part were 100 Vol% air atmosphere, and only the firing atmosphere of the high temperature holding part was 100 Vol% carbon dioxide atmosphere. Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of the comparative example sample 1-2.

(Comparative Example 1-3)
In Example 1-1, the carbon dioxide was not replaced in the temperature raising portion under the calcining conditions. Instead, carbon dioxide was replaced in the temperature-lowering part. That is, all the firing atmospheres of the temperature raising part and the high temperature holding part were 100 Vol% air atmosphere, and only the temperature lowering part firing atmosphere was 100 Vol% carbon dioxide atmosphere. Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of the comparative example sample 1-3.

(Example 2-1)
In Example 1-1, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 80/20. Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of Example sample 2-1.

(Comparative Example 2-1)
In Comparative Example 1-1, part of the barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 80/20. Other than that was carried out similarly to the said comparative example 1-1, and obtained the barium titanate powder of the comparative example sample 2-1.

(Comparative Example 2-2)
In Comparative Example 1-2, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 80/20. Other than that was carried out similarly to the said comparative example 1-2, and obtained the barium titanate powder of the comparative example sample 2-2.

(Comparative Example 2-3)
In Comparative Example 1-3, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 80/20. Other than that was carried out similarly to the said comparative example 1-3, and obtained the barium titanate powder of the comparative example sample 2-3.

(Example 3-1)
In Example 1-1, part of the barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 50/50. Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of Example sample 3-1.

(Comparative Example 3-1)
In Comparative Example 1-1, part of the barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 50/50. Other than that was carried out similarly to the said comparative example 1-1, and obtained the barium titanate powder of the comparative example sample 3-1.

(Comparative Example 3-2)
In Comparative Example 1-2, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 50/50. Other than that was carried out similarly to the said comparative example 1-2, and obtained the barium titanate powder of the comparative example sample 3-2.

(Comparative Example 3-3)
In Comparative Example 1-3, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 50/50. Other than that was carried out similarly to the said comparative example 1-3, and obtained the barium titanate powder of the comparative example sample 3-3.

(Example 4-1)
In Example 1-1, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 10/90. Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of Example sample 4-1.

(Comparative Example 4-1)
In Comparative Example 1-1, part of the barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 10/90. Other than that was carried out similarly to the said comparative example 1-1, and obtained the barium titanate powder of the comparative example sample 4-1.

(Comparative Example 4-2)
In Comparative Example 1-2, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 10/90. Other than that was carried out similarly to the said comparative example 1-2, and obtained the barium titanate powder of the comparative example sample 4-2.

(Comparative Example 4-3)
In Comparative Example 1-3, a part of barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ), and the molar ratio of (BaCO ₃ ) to (BaCl ₂ ) was changed to (BaCO ₃ ). ) / (BaCl ₂ ) = 10/90. Other than that was carried out similarly to the said comparative example 1-3, and obtained the barium titanate powder of the comparative example sample 4-3.

(Example 5-1)
In Example 1-1, barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ). Other than that was carried out similarly to the said Example 1-1, and obtained the barium titanate powder of Example sample 5-1.

(Comparative Example 5-1)
In Comparative Example 1-1, barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ). Other than that was carried out similarly to the said comparative example 1-1, and obtained the barium titanate powder of the comparative example sample 5-1.

(Comparative Example 5-2)
In Comparative Example 1-2, barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ). Other than that was carried out similarly to the said comparative example 1-2, and obtained the barium titanate powder of the comparative example sample 5-2.

(Comparative Example 5-3)
In Comparative Example 1-3, barium carbonate (BaCO ₃ ) used as the raw material powder was changed to barium chloride (BaCl ₂ ). Other than that was carried out similarly to the said comparative example 1-3, and obtained the barium titanate powder of the comparative example sample 5-3.

For the samples of Examples and Comparative Examples thus obtained, (1) the value of D ₅₀ , (2) the value of (D ₉₀ -D ₁₀ ) / D ₅₀ , (3) the specific surface area SSA (m ² / The values of g), (4) c / a axial ratio of the crystal, and (5) half-value width ΔH (111) of the (111) plane of the crystal were determined as follows.

(1) D ₅₀ value (μm), and (2) (D ₉₀ -D ₁₀ ) / D ₅₀ value samples were dispersed by an ultrasonic homogenizer, and the particle size distribution was measured using a laser diffraction particle size distribution meter. D ₅₀ values and _{(D 90 -D 10) / D} 50 value of was determined, respectively. D ₉₀ represents a 90% sieving particle size, D ₁₀ represents a 10% sieving particle size, and D ₅₀ represents a 50% sieving particle size.

(3) Specific surface area SSA (m ² / g)
The specific surface area SSA (m ² / g) of the powder was determined by the BET method.

(4) c / a axial ratio and (5) half-value width ΔH (111) of (111) plane
X-ray diffraction measurement was performed to determine the c / a axial ratio of the crystal and the half-value width ΔH (111) of the (111) plane.

The results are shown in Table 1 below.
Comparative Example 1 has a conventional standard (Standard), the reference to be cleared for each measurement items in Table 1, the value of D ₅₀ is at 0.550 or _{less, (D 90 -D 10) /} D 50 Is 1.100 or less, the SSA value is 4.100 or more, the c / a axial ratio is 1.00800 or more, and ΔH (111) is 0.132 or less.

  From the results in Table 1, it can be seen that all the measurement items were cleared in the example sample, and the average particle size was small and a uniform particle size was obtained. Tetragonality (tetragonality) and crystallinity are also good.

For example, in the sample of Comparative Example 1-1, although the SSA is large, the value of D ₅₀ is almost the same as the sample of Example 1-1, and the sample of Comparative Example 1-1 has coarse particles and fine particles. It is considered that the simple particles are aggregated to constitute one pseudo particle. Therefore, the c / a axial ratio and ΔH (111) are improved. In addition, the aggregation of the particle group is confirmed by the SEM photograph.

  For example, Comparative Example 1-2 sample and Comparative Example 1-3 sample have an overall large particle size and lack uniformity, which is unsuitable for dealing with thinning of the element. Moreover, it is confirmed by the SEM photograph that there are many coarse particles. Since the particle size itself is large, the apparent crystallinity has a good numerical value.

  The same tendency is observed in the experimental results 2 to 5 in which the configuration of the barium raw material powder is changed.

  The present invention can be used, for example, in the field of manufacturing an oxide powder (eg, barium titanate powder) having a perovskite structure used as a material for forming a dielectric layer of a multilayer chip capacitor.

FIG. 1 is a perspective view showing an embodiment of a multilayer chip capacitor. FIG. 2 is a cross-sectional view of the multilayer chip capacitor shown in FIG. FIG. 3 is a perspective view for easily explaining the formation process of the laminated structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer chip capacitor 2 ... Element main body 7 ... Dielectric layer 11, 15 ... External electrode 23, 28 ... Internal electrode layer

Claims (10)

A raw material preparation step of preparing at least two kinds of main raw material powders when producing an oxide powder having a perovskite structure;
A mixing step of mixing at least two of these main raw material powders;
A calcining step of calcining at least two or more mixed main raw material powders, and a method for producing an oxide powder having a perovskite structure,
The calcining step includes a temperature raising section as a first stage for gradually raising the calcining temperature, a high temperature holding section as a second stage for maintaining a constant high temperature after the temperature rise, and a high temperature that has been maintained. And a temperature lowering section as a third stage for gradually lowering the temperature,
The method for producing an oxide powder having a perovskite structure according to claim 1, wherein carbon dioxide (CO ₂ ) is introduced into an initial air treatment atmosphere in the temperature raising section as the first stage. Carbon dioxide (CO ₂ ) is introduced only into the treatment atmosphere in the temperature raising section as the first stage, and carbon dioxide (CO ₂ (in the treatment atmosphere in the high temperature holding section as the second stage and the temperature lowering section as the third stage). method of manufacturing an oxide powder having a perovskite structure according to claim 1, CO ₂₎ is not introduced.   The method for producing an oxide powder having a perovskite structure according to claim 1 or 2, wherein the treatment atmosphere in the high temperature holding section as the second stage and the temperature lowering section as the third stage is an air atmosphere. The carbon dioxide (CO ₂ ) introduced into the processing atmosphere in the temperature raising section as the first stage is introduced so as to completely replace the furnace atmosphere. A method for producing an oxide powder having a perovskite structure. The introduction start time of the carbon dioxide (CO ₂ ) is such that the temperature of the temperature raising portion is within a temperature range of room temperature to 650 ° C. The oxide powder having a perovskite structure according to claim 1. Production method. Oxidation of a perovskite structure in which the main raw material powder is represented by ABO ₃ (A is at least one selected from the group of Ba, Sr, Ca, and B is at least one selected from the group of Ti, Zr). The method for producing an oxide powder having a perovskite structure according to any one of claims 1 to 5, which is a compound powder constituting an A site of a product and a compound powder constituting a B site.   The oxide powder having a perovskite structure according to any one of claims 1 to 6, wherein the oxide powder having a perovskite structure is a barium titanate powder, and the main raw material powder is a titanium compound and a barium compound. Method.   The method for producing an oxide powder having a perovskite structure according to claim 7, wherein the barium compound of the main raw material powder contains a carbonate.   9. The oxide powder having a perovskite structure is used to form a dielectric layer of a multilayer chip capacitor having an element body in which dielectric layers and internal electrode layers are alternately laminated. The manufacturing method of the oxide powder which has the perovskite structure in any one of these.   10. A multilayer chip capacitor having an element body in which dielectric layers and internal electrode layers are alternately laminated, wherein the oxide powder used to form the dielectric layer is any one of claims 1 to 9. A multilayer chip capacitor formed by the manufacturing method described above.

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