JP2005067909A - Method for producing oxide powder with perovskite structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily producing oxide powder with a perovskite structure by which uniform particle diameters in which the average particle diameters are small can be obtained so as to correspond to the thinned layer of an element, which has the extremely reduced content of coarse particles, and which further has excellent tetragonality and crystallinity. <P>SOLUTION: This method for producing the oxide powder with the perovskite structure comprises a calcining process where mixed at least two or more main source material powder is calcined. The calcining process is composed of: a temperature rising process as the first stage where the calcining temperature is gradually raised; a high temperature holding process as the second stage where, after the temperature rising, a fixed high temperature is held; and a temperature reducing process as the third stage where the high temperature which has been held is gradually reduced. Carbon dioxide (CO<SB>2</SB>) is introduced into a treatment atmosphere in the temperature rising process as the first stage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００８９】
表１の結果より、実施例サンプルでは全ての測定項目をクリアできており、平均粒径が小さくかつ均一な粒径が得られていることがわかる。正方晶性（テトラゴナリティ）および結晶性もよい。
【００９０】
例えば比較例１−１サンプルでは、ＳＳＡが大きくなっているにもかかわらずＤ_５０の値が実施例１−１サンプルと同程度であり、比較例１−１サンプルのものは、粒子が凝集して擬似１粒子を構成しているものと考えられる。そのためΔＨ（１１１）の値も悪くなっている。なお、粒子群の凝集はＳＥＭ写真で確認されている。
【００９１】
例えば、比較例１−２サンプルおよび比較例１−３サンプルでは、粒径が全体的に大きくなっており、かつ均一性に欠けるために素子の薄層化に対応するには不適である。また、粗大粒子も多く存在していることがＳＥＭ写真で確認されている。粒径そのものが大きいために見かけの結晶性は良好な数値が得られている。
【００９２】
このような実験結果は、バリウム原料粉の構成を変えた実験グループ２〜５についても同様な傾向が見られる。
【００９３】
【発明の効果】
上記の結果より本発明の効果は明らかである。すなわち、本発明は、ペロブスカイト構造を有する酸化物粉末を製造する際の少なくとも２種以上の主原料粉末を準備する原料準備工程と、これらの少なくとも２種以上の主原料粉末を混合する混合工程と、混合された少なくとも２種以上の主原料粉末を仮焼きする仮焼き工程と、を有するペロブスカイト構造を有する酸化物粉末の製造方法であって、前記仮焼き工程は、徐々に仮焼き温度を上げていく第１段階としての昇温部と、昇温した後に一定の高温を保持する第２段階としての高温保持部と、保持されていた高温を徐々に温度降下させていく第３段階としての降温部とを有し、前記第１段階としての昇温部における処理雰囲気中に二酸化炭素（ＣＯ_２）を導入してなるように構成されているので、簡易な製造方法であって、素子の薄層化に対応できるように平均粒径が小さくかつ均一な粒径が得られる。粗大粒子の含有率も極めて少ない。正方晶性（テトラゴナリティ）および結晶性にも優れる。
【図面の簡単な説明】
【図１】図１は、積層型チップコンデンサの一実施形態を示す斜視図である。
【図２】図２は、図１に示される積層型チップコンデンサのＡ−Ａ線矢視断面図である。
【図３】図３は、積層構造の形成過程を分かりやすく説明するための斜視図である。
【符号の説明】
１…積層型チップコンデンサ
２…素子本体
７…誘電体層
１１，１５…外部電極
２３，２８…内部電極層[0001]
BACKGROUND OF THE INVENTION
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.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-255552
[Patent Document 2] Japanese Patent Laid-Open No. 2001-316114
[0003]
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).
[0004]
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.
[0005]
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. .
[0006]
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.
[0007]
[Problems to be solved by the invention]
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.
[0008]
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.
[0009]
[Means for Solving the Problems]
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.
[0010]
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 raises 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 carbon dioxide (CO 2) in the treatment atmosphere in the temperature raising unit as the first stage.₂).
[0011]
Further, as a preferred embodiment of the present invention, carbon dioxide (CO 2) only in the treatment atmosphere in the temperature raising section as the first stage.₂) Is introduced, and carbon dioxide (CO 2) is contained in the processing atmosphere in the high temperature holding section as the second stage and the cooling section as the third stage.₂) Is not introduced.
[0012]
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 a nitrogen atmosphere.
[0013]
Further, 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.₂) Is introduced to completely replace the furnace atmosphere.
[0014]
In a preferred embodiment of the present invention, the carbon dioxide (CO₂) Is started so that the temperature of the temperature raising portion is in the temperature range of room temperature to 650 ° C.
[0015]
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, and Ca, and B is at least one selected from the group of Ti, Zr) and constitutes an A site of an oxide having a perovskite structure The compound powder and the compound powder constituting the B site are configured.
[0016]
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.
[0017]
As a preferred embodiment of the present invention, the barium compound of the main raw material powder is configured to contain a carbonate.
[0018]
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.
[0019]
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.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0021]
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.
[0022]
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.
[0023]
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.
[0024]
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).
[0025]
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.
[0026]
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).
[0027]
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).
[0028]
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.
[0029]
Hereinafter, the manufacturing method of the oxide powder which has the perovskite structure of this invention is demonstrated according to process order.
[0030]
[Step of preparing at least two kinds of main raw material powders when producing an oxide powder having a perovskite structure]
Main raw material powder is ABO₃It is comprised from the compound powder which comprises the A site of the oxide of the perovskite structure represented, and the compound powder which comprises 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.
[0031]
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.
[0032]
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 (BaCO₃) Can be preferably used. Specific surface area is 5-40m²Those in the range of / g are preferred. Mixed with barium carbonate or instead of barium carbonate, barium chloride (BaCl₂), Barium hydroxide (Ba (OH)₂) May be used.
[0033]
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.
[0034]
Titanium dioxide is prepared as the metal oxide powder. This can be obtained, for example, by thermally decomposing titanium tetrachloride. Specific surface area is 10-50m²Those in the range of / g are preferred.
[0035]
[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.
[0036]
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.
[0037]
The slurry obtained by such mixing is usually dried to form a mixed powder.
[0038]
[Step of calcining mixed main raw material powder]
The mixed powder obtained in the mixing step is usually formed into a pellet-like material by pressure molding. The pressure molding is usually performed after water is added to the mixed powder so as to enable molding.
[0039]
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.
[0040]
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.
[0041]
In the calcining process of the present invention, carbon dioxide (CO2) is contained in the treatment atmosphere in the temperature raising section as the first stage.₂) Is introduced. In particular, carbon dioxide (CO 2) only in the treatment atmosphere in the temperature raising section as the first stage.₂) Is introduced, and carbon dioxide (CO 2) is contained in the processing atmosphere in the high temperature holding section as the second stage and the cooling section as the third stage.₂) Is preferably not introduced.
[0042]
Carbon dioxide (CO2) introduced into the processing atmosphere of the temperature raising section as the first stage₂) Carbon dioxide in the furnace (CO₂) In the range of 4 to 100 Vol%, preferably 20 to 100 Vol%, more preferably 50 to 100 Vol%. In particular, an operation that completely replaces the furnace atmosphere is preferable (that is, carbon dioxide (CO₂) Is 100 Vol%).
[0043]
Carbon dioxide (CO₂The temperature of the temperature riser is at room temperature (synonymous with the start temperature of the temperature raising operation, usually about 25 ° C.) or higher, particularly 400 ° C. or higher, and further within the temperature range of 550 to 650 ° C. Sometimes it is preferred. In addition, once formed carbon dioxide (CO₂) The atmosphere is preferably continued until reaching the high temperature holding part. The temperature raising rate of such a temperature raising part is preferably about 100 to 300 ° C./hr.
[0044]
Further, the treatment atmosphere in the high temperature holding section as the second stage and the temperature lowering section as the third stage is carbon dioxide (CO₂) Is stopped, and a nitrogen atmosphere, an air atmosphere, an oxygen atmosphere, or a mixed atmosphere thereof is preferable. Among these, a nitrogen atmosphere is preferable.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
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.
[0049]
[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.
[0050]
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.
[0051]
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 and ΔH (111) with respect to the specific surface area can be improved.
[0052]
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.
[0053]
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 has an oxygen partial pressure of 10.^-2-10^-15The atmosphere is MPa.
[0054]
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.
[0055]
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.
[0056]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples.
[0057]
(Example 1-1)
Specific surface area 5.8m²/ G barium carbonate powder and a specific surface area of 22.4 m²/ G titanium dioxide powder was prepared. Titanium dioxide powder is produced by thermal decomposition of titanium tetrachloride.
[0058]
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.
[0059]
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.
[0060]
Temporary firing conditions
Temperature riser
The temperature was raised at a rate of temperature increase of 200 ° C./hr from room temperature to 975 ° C. (high temperature holding temperature). Initially nitrogen atmosphere (N₂Gas flow rate = 2 liters / min), the introduction of carbon dioxide was started when the temperature rose to 550 ° C, and the firing atmosphere was immediately replaced with a carbon dioxide atmosphere from the nitrogen atmosphere (CO₂Gas flow rate = 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 a 100 Vol% carbon dioxide atmosphere.
[0061]
High temperature holding part
When reaching 975 ° C. (high temperature holding temperature), the introduction of carbon dioxide was stopped, and instead, the introduction of nitrogen was started, and immediately the firing atmosphere was completely replaced from the carbon dioxide atmosphere to the nitrogen atmosphere (N₂Gas flow rate = 2 liter / min and 100 vol% nitrogen atmosphere). This state was continued for a high temperature of 975 ° C., that is, for 2 hours.
[0062]
Temperature drop part
After the processing in the high temperature holding unit was completed, the temperature was lowered at a cooling rate of 200 ° C./hr. The atmosphere in this case was the same 100 Vol% nitrogen atmosphere as that in the high temperature holding part (N₂Gas flow rate = 2 liter / min).
[0063]
After such a calcination step, the obtained pellet-like material was crushed to obtain barium titanate powder of Example Sample 1-1.
[0064]
(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 set to 100 vol% nitrogen 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.
[0065]
(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% nitrogen 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.
[0066]
(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 portion and the high temperature holding portion were 100 vol% nitrogen atmosphere, and only the temperature lowering portion 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.
[0067]
(Example 2-1)
In the above Example 1-1, barium carbonate (BaCO) used as a raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0068]
(Comparative Example 2-1)
In Comparative Example 1-1, barium carbonate (BaCO) used as the raw material powder.₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0069]
(Comparative Example 2-2)
In the above Comparative Example 1-2, barium carbonate (BaCO) used as a raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0070]
(Comparative Example 2-3)
In Comparative Example 1-3, barium carbonate (BaCO) used as the raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0071]
(Example 3-1)
In the above Example 1-1, barium carbonate (BaCO) used as a raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0072]
(Comparative Example 3-1)
In Comparative Example 1-1, barium carbonate (BaCO) used as the raw material powder.₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0073]
(Comparative Example 3-2)
In the above Comparative Example 1-2, barium carbonate (BaCO) used as a raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0074]
(Comparative Example 3-3)
In Comparative Example 1-3, barium carbonate (BaCO) used as the raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0075]
(Example 4-1)
In the above Example 1-1, barium carbonate (BaCO) used as a raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0076]
(Comparative Example 4-1)
In Comparative Example 1-1, barium carbonate (BaCO) used as the raw material powder.₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0077]
(Comparative Example 4-2)
In the above Comparative Example 1-2, barium carbonate (BaCO) used as a raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0078]
(Comparative Example 4-3)
In Comparative Example 1-3, barium carbonate (BaCO) used as the raw material powder₃) Part of barium chloride (BaCl)₂), (BaCO₃) And (BaCl₂) And the molar ratio (BaCO₃) / (BaCl₂) = 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.
[0079]
(Example 5-1)
In the above Example 1-1, barium carbonate (BaCO) used as a raw material powder₃) 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.
[0080]
(Comparative Example 5-1)
In Comparative Example 1-1, barium carbonate (BaCO) used as the raw material powder.₃) 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.
[0081]
(Comparative Example 5-2)
In the above Comparative Example 1-2, barium carbonate (BaCO) used as a raw material powder₃) 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.
[0082]
(Comparative Example 5-3)
In Comparative Example 1-3, barium carbonate (BaCO) used as the raw material powder₃) 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.
[0083]
For the samples of Examples and Comparative Examples thus obtained, (1) D₅₀Value of (2) (D₉₀-D₁₀) / D₅₀(3) Specific surface area SSA (m²/ G), (4) the c / a axial ratio of the crystal, and (5) the half-value width ΔH (111) of the (111) plane of the crystal, respectively, were determined as follows.
[0084]
(1) D ₅₀ Value (μm), and (2) (D ₉₀ -D ₁₀ ) / D ₅₀ The value of the
Disperse the sample with an ultrasonic homogenizer and measure the particle size distribution using a laser diffraction particle size distribution analyzer.₅₀And (D₉₀-D₁₀) / D₅₀Each of the values was determined. D₉₀Represents a 90% sieving particle size, D₁₀Represents a 10% sieving particle size, D₅₀Represents a 50% sieving particle size.
[0085]
(3) Specific surface area SSA (m ² / G)
Specific surface area of powder SSA (m²/ G).
[0086]
(4) c / a axial ratio, and (5) ( 111 ) Surface half width ΔH ( 111 )
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.
[0087]
The results are shown in Table 1 below.
Comparative Example 1 is a conventional standard (Standard), and the standard to be cleared for each measurement item in Table 1 is D₅₀Is less than or equal to 0.520 and (D₉₀-D₁₀) / D₅₀Is 0.700 or less, the SSA value is 4.300 or more, the c / a axial ratio is 1.00900 or more, and ΔH (111) is 0.125 or less.
[0088]
[Table 1]

[0089]
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.
[0090]
For example, in the sample of Comparative Example 1-1, D is increased despite the increase in SSA.₅₀Of the sample of Comparative Example 1-1 is considered to be composed of pseudo-particles by aggregation of particles. For this reason, the value of ΔH (111) is also deteriorated. In addition, the aggregation of the particle group is confirmed by the SEM photograph.
[0091]
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.
[0092]
The same tendency is observed in the experimental results 2 to 5 in which the configuration of the barium raw material powder is changed.
[0093]
【The invention's effect】
The effects of the present invention are clear from the above results. 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 raises 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 carbon dioxide (CO 2) in the treatment atmosphere in the temperature raising unit as the first stage.₂) Is a simple manufacturing method, and the average particle size is small and uniform particle size can be obtained so as to cope with the thinning of the device. The content of coarse particles is also very low. Excellent tetragonality and crystallinity.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of a multilayer chip capacitor.
2 is a cross-sectional view taken along line AA of the multilayer chip capacitor shown in FIG. 1. FIG.
FIG. 3 is a perspective view for easily explaining the formation process of the laminated structure.
[Explanation of symbols]
1 ... Multilayer chip capacitor
2. Element 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 a treatment atmosphere in the temperature raising section as the first stage. Carbon dioxide (CO ₂ ) is introduced only into the processing atmosphere in the temperature raising section as the first stage, and carbon dioxide (CO ₂ (in the processing atmosphere in the high temperature holding section as the second stage and the temperature decreasing section as the third stage). The method for producing an oxide powder having a perovskite structure according to claim 1, wherein CO ₂ ) is not introduced. 3. The method for producing an oxide powder having a perovskite structure according to claim 1, wherein a processing atmosphere in the high temperature holding section as the second stage and the cooling section as the third stage is a nitrogen 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 rising 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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