JP2005041730A - Production method for dielectric ceramic raw material powder, dielectric ceramic raw material powder, and laminated ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric ceramic raw material powder which hardly allows the segregation of additive components to occur, can ensure good temperature characteristics, and is suitable for producing a laminated ceramic capacitor. <P>SOLUTION: In the method for producing the dielectric ceramic raw material powder, a primary raw material powder for a dielectric ceramic having a composition represented by a general formula ABO<SB>3</SB>is subjected to a grinding step to yield a secondary raw material powder. The grinding step is performed as follows: in a mill with a stirrer installed therein and rotating at a circumferential speed of 3-9 m/sec, the primary raw material powder is stirred together with grinding balls having a particle diameter of 0.5 mm or less and filled in the mill to a filling rate of 70-95 vol.%. The condition of grinding is set so that, when compared with the primary raw material powder, the secondary raw material powder has an H1/H2 ratio increased at least by 10% and a specific surface area increased by 10-50%; here, H1 is the diffraction peak intensity at the (200) plane in an X-ray diffraction analysis and H2 is the minimum value of diffraction intensity appearing in between the diffraction peak of the (002) plane and that of the (200) plane. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４４】
まず、表１に示すような「１次原料粉末のＨ１／Ｈ２比」および「１次原料粉末の比表面積」をそれぞれ有する１次原料粉末を用意した。ここで、１次原料粉末としては、実施例１、３および４ならびに比較例１、３および４では、ＢａＴｉＯ_３ 粉末を用い、実施例２および比較例２では、（Ｂａ_０．９９Ｃａ_０．０１）ＴｉＯ_３ 粉末を用い、実施例５および比較例５では、（Ｂａ_{０．９５２} Ｃａ_{０．０４８} ）（Ｔｉ_０．９９Ｚｒ_０．０１）Ｏ_３ 粉末を用いた。
【００４５】
次に、上記１次原料粉末１０ｋｇをイオン交換水２０リットルでスラリー化した。
【００４６】
次に、上記スラリーを、ビーズミルにて粉砕処理した。ここで、表１に示すような「玉石径」を有するＰＳＺからなる玉石を用い、これを表１に示すような「玉石充填率」をもってビーズミル中に充填し、表１に示すような「周速」によって粉砕処理を行なった。
【００４７】
上記粉砕処理により得られた２次原料粉末は、１次原料粉末に比べて、表１に示すような「Ｈ１／Ｈ２比の減少率」および「比表面積の増加率」をそれぞれ示した。
【００４８】
次に、粉砕処理後の２次原料粉末を含むスラリーに、実施例１、３および４ならびに比較例１、３および４では、ＢａＴｉＯ_３ １００モルに対して、実施例２および比較例２では、（Ｂａ_０．９９Ｃａ_０．０１）ＴｉＯ_３ １００モルに対して、ならびに、実施例５および比較例５では、（Ｂａ_{０．９５２} Ｃａ_{０．０４８} ）（Ｔｉ_０．９９Ｚｒ_０．０１）Ｏ_３ １００モルに対して、Ｍｇ、Ｄｙ、Ｍｎ、ＮｉおよびＳｉを、１．５Ｍｇ−２．５Ｄｙ−０．５Ｍｎ−０．２Ｎｉ−２．０Ｓｉの組成になるように特性調整用元素として加え、乾燥処理を行ない、誘電体セラミック原料粉末を得た。
【００４９】
次に、上述の誘電体セラミック原料粉末を用いて、内部電極間に位置するセラミック層の厚みが３．０μｍであり、内部電極の積層数が５０の積層セラミックコンデンサを作製した。
【００５０】
このようにして得られた実施例１〜５および比較例１〜５の各々に係る積層セラミックコンデンサについて、表２に示すように、「比誘電率」、「容量温度特性」および「平均故障時間」をそれぞれ評価した。
【００５１】
「比誘電率」については、各積層セラミックコンデンサのセラミック層を構成する誘電体セラミックの比誘電率を、温度２５℃、１ｋＨｚ、および０．５Ｖ_ｒｍｓ の条件下で測定したものである。
【００５２】
「容量温度特性」については、ＥＩＡ規格のＸ７Ｒ特性を満足するか否かを評価したもので、２５℃での静電容量を基準とした−５５℃での容量変化率および１２５℃での容量変化率を求めた。
【００５３】
「平均故障時間」については、温度１５０℃において６０Ｖの電圧を印加し続け、試料となる積層セラミックコンデンサが故障に至るまでの時間の平均値を求めたものである。
【００５４】
【表２】

【００５５】
実施例１〜５では、表１に示すように、「１次原料粉末のＨ１／Ｈ２比」が３〜１５の範囲にあり、「１次原料粉末の比表面積」が１〜６ｍ^２ ／ｇの範囲にあり、「玉石径」が０．５ｍｍ以下であり、「玉石充填率」が７０〜９５体積％の範囲にあり、「周速」が３〜９ｍ／秒の範囲にある。そして、「Ｈ／Ｈ２比の減少率」は１０％以上であり、「比表面積の増加率」は１０〜５０％の範囲にある。
【００５６】
その結果、実施例１〜５では、表２に示すように、「比誘電率」において満足し、「容量温度特性」がＥＩＡ規格のＸ７Ｒ特性を満足し、「平均故障時間」についても、比較的長い時間を示し、信頼性の高い積層セラミックコンデンサを得ることができた。これらの好ましい特性は、次のようにして得られたものと考えられる。
【００５７】
実施例１〜５では、表１に示すような粉砕条件の下で、１次原料粉末を湿式粉砕することによって、１次原料粉末の粒子表面にダメージが与えられて、粉砕処理後の２次原料粉末において、その結晶性が低下し、そのため、添加成分の固溶が促進される。また、粉砕によって、比表面積が増加し、添加成分との反応性が高まり、固溶が促進される。このように、固溶が促進されることにより、添加成分の偏析が起こりにくくなり、その結果、信頼性が高くなる。また、粉砕における「玉石径」および「周速」を表１に示すように制御することによって、結晶性の低下と比表面積の増加の度合いを調節し、その結果、「容量温度特性」について、ＥＩＡ規格のＸ７Ｒ特性を満足させることができる。
【００５８】
これら実施例１〜５に対して、まず、比較例１では、表１に示すように、「周速」が３ｍ／秒未満であり、粉砕力が弱い。そのため、「Ｈ１／Ｈ２比の減少率」が５％と低く、結晶性の低下の度合いが十分でなく、また、「比表面積の増加率」についても、８％と低く十分でなかった。その結果、添加成分の偏析が起こりやすくなっており、表２に示すように、「平均故障時間」が短く、信頼性が低かった。
【００５９】
比較例２では、表１に示すように、「玉石径」が０．５ｍｍより大きく、粉砕が進みすぎ、「比表面積の増加率」が６０％と高かった。その結果、表２に示すように、「容量温度特性」がＥＩＡ規格のＸ７Ｒ特性を満足しなかった。
【００６０】
比較例３では、表１に示すように、「周速」が９ｍ／秒を超え、粉砕が進みすぎ、「比表面積の増加率」が６５％と高くなった。その結果、表２に示すように、「容量温度特性」がＥＩＡ規格のＸ７Ｒ特性を満足しなかった。
【００６１】
比較例４では、表１に示すように、「１次原料粉末のＨ１／Ｈ２比」が３未満でありかつ「１次原料粉末の比表面積」が６ｍ^２ ／ｇを超えるばかりでなく、「玉石充填率」が１００％と高かった。そのため、粉砕が進みすぎて、「比表面積の増加率」が６０％と高く、表２に示すように、「容量温度特性」がＥＩＡ規格のＸ７Ｒ特性を満足しなかった。
【００６２】
比較例５では、表１に示すように、「１次原料粉末のＨ１／Ｈ２比」が１５を超えかつ「１次原料粉末の比表面積」が１ｍ^２ ／ｇ未満であるばかりでなく、「玉石充填率」が６５体積％と低かった。そのため、「Ｈ１／Ｈ２比の減少率」が７％と低く、結晶性の低下が十分でなく、また、「比表面積の増加率」が９％と低かった。そのため、添加成分の偏析が起こりやすくなっており、表２に示すように、「平均故障時間」が短く、信頼性が低かった。
【００６３】
【発明の効果】
以上のように、この発明に係る誘電体セラミック原料粉末の製造方法によれば、誘電体セラミックのための１次原料粉末を粉砕処理して、２次原料粉末を得るようにするとともに、粉砕処理工程では、３〜９ｍ／秒の周速で回転する攪拌体が内蔵されたミル内において、ミルの有効内容積に対する充填率が７０〜９５体積％になるように充填された粒径０．５ｍｍ以下の玉石とともに、１次原料粉末を攪拌するようにし、それによって、２次原料粉末の回折強度の比であるＨ１／Ｈ２比を１次原料粉末のそれより１０％以上減少させるとともに、２次原料粉末の比表面積を１次原料粉末のそれより１０〜５０％増加させるようにしているので、次のような効果が奏される。
【００６４】
すなわち、粉砕処理工程において、１次原料粉末の粒子表面にダメージが与えられ、粉砕後の２次原料粉末の結晶性が低下し、特性調整用元素のような添加成分の固溶が促進される。また、比表面積が増加し、添加成分との反応性が高まり、これによっても、固溶が促進される。そして、このように固溶が促進されることにより、添加成分の偏析が起こりにくくなり、得られた誘電体セラミック原料粉末をもって構成された積層セラミックコンデンサのような積層セラミック電子部品の信頼性を高くすることができる。
【００６５】
したがって、得ようとする誘電体セラミック原料粉末が、特性調整のための元素を含む場合、このような特性調整用元素を、２次原料粉末に添加するようにすれば、上述した効果をより確実に享受することができる。
【００６６】
また、上述のように粉砕条件を制御することによって、２次原料粉末における結晶性の低下の度合いおよび比表面積の増加の度合いを調節し、良好な温度特性を維持することができる。
【００６７】
このようなことから、この発明に係る製造方法によって製造された誘電体セラミック原料粉末を用いて積層セラミックコンデンサを構成すれば、信頼性が高くかつ良好な容量温度特性が確保された積層セラミックコンデンサを得ることができる。
【００６８】
この発明に係る誘電体セラミック原料粉末の製造方法において、１次原料粉末についてのＨ１／Ｈ２比が３〜１５の範囲にあり、１次原料粉末の比表面積が１〜６ｍ^２ ／ｇの範囲にあると、この発明による粉砕条件を適用して、前述したように、Ｈ１／Ｈ２比の減少率を１０％以上としかつ比表面積の増加率を１０〜５０％としたとき、誘電体セラミック原料粉末にとって適正な結晶性および比表面積を安定して得ることができる。
【図面の簡単な説明】
【図１】この発明の一実施形態による積層セラミックコンデンサ１を図解的に示す断面図である。
【図２】Ｘ線回折分析における（２００）面の回折ピーク強度Ｈ１、および（００２）面の回折ピークと（２００）面の回折ピーク間に見られる回折強度の極小値Ｈ２を図解する図である。
【符号の説明】
１ 積層セラミックコンデンサ
２ 積層体
３ セラミック層
４，５ 内部電極
８，９ 外部電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric ceramic raw material powder manufacturing method, a dielectric ceramic raw material powder obtained by this manufacturing method, and a multilayer ceramic capacitor constituted by using this dielectric ceramic raw material powder. The present invention relates to an improvement of pulverization conditions for obtaining ceramic raw material powder.
[0002]
[Prior art]
In order to constitute a ceramic layer serving as a dielectric in the multilayer ceramic capacitor, for example, a BaTiO ₃ -based or (Ba, Ca) TiO ₃ -based dielectric ceramic is used.
[0003]
In the raw material powder for such a dielectric ceramic, when aggregated particles and coarse particles are present, there is a problem that the reliability of the multilayer ceramic capacitor is lowered when the multilayer ceramic capacitor is produced using the aggregated particles and coarse particles. In addition, when a raw material powder having high crystallinity is used, the solid solution of the additive component does not proceed smoothly, and the additive component segregates after sintering, and even in this case, the reliability of the multilayer ceramic capacitor decreases. is there.
[0004]
In Japanese Patent Application Laid-Open No. 2001-345230 (Patent Document 1), as a raw material powder for a BaTiO ₃ dielectric ceramic, in X-ray diffraction analysis, the angle of the peak point of the diffraction line on the (002) plane and the diffraction on the (200) plane. A ratio I ₍₂₀₀₎ / Ib of the peak intensity (I ₍₂₀₀₎ ) of the diffraction line on the (200) plane to the intensity (Ib) at an intermediate point with the angle of the peak point of the line is 4 to 16 The use is described. Moreover, in this patent document 1, it is said that it is preferable that the specific surface area of raw material powder is 1.0-8.0 m < ² > / g, and in order to produce such raw material powder, wet grinding is performed. .
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-345230
[Problems to be solved by the invention]
However, Patent Document 1 discloses the crystallinity and specific surface area of the raw material powder as a result of pulverization, but the pulverization conditions for obtaining such preferable crystallinity and specific surface area are specifically defined. Absent.
[0007]
Moreover, by previously pulverizing the raw material powder, aggregated particles and coarse particles of the raw material powder can be eliminated, but the temperature characteristics of the obtained dielectric ceramic sintered body may not be ensured.
[0008]
Accordingly, there is provided a pulverization condition that can stably obtain a dielectric ceramic raw material powder having a preferable crystallinity and specific surface area capable of ensuring high temperature characteristics and high reliability of the obtained dielectric ceramic sintered body. It is hoped that it can be defined.
[0009]
An object of the present invention is to provide a method for producing a dielectric ceramic raw material powder in which pulverization conditions capable of satisfying the above-described requirements are defined.
[0010]
Another object of the present invention is to provide a dielectric ceramic raw material powder obtained by the manufacturing method as described above, and a multilayer ceramic capacitor configured using the dielectric ceramic raw material powder.
[0011]
[Means for Solving the Problems]
A method for producing a dielectric ceramic raw material powder according to the present invention has a general formula ABO ₃ (where A is at least one of Ba, Ca, Sr and Mg, and B is Ti, Zr and Hf). A step of preparing a primary raw material powder for a dielectric ceramic having a composition represented by the following formula, and a step of pulverizing the primary raw material powder to thereby obtain a secondary raw material powder And.
[0012]
And in order to solve the technical problem mentioned above, the pulverization process is performed in a mill having a built-in stirring body rotating at a peripheral speed of 3 to 9 m / sec. It is characterized by being carried out by stirring the primary raw material powder together with a cobblestone having a particle size of 0.5 mm or less filled so as to be in volume%.
[0013]
In addition, the diffraction peak intensity on the (200) plane in the X-ray diffraction analysis for each of the primary raw material powder and the secondary raw material powder is H1, and the diffraction peak on the (002) plane in the same X-ray diffraction analysis and the (200) plane When the minimum value of the diffraction intensity found between the diffraction peaks of H2 is H2, the H1 / H2 ratio of the secondary raw material powder is reduced by 10% or more compared to the primary raw material powder by the pulverization process, and the ratio The pulverization conditions in the pulverization process are set so that the surface area increases by 10 to 50%.
[0014]
The H1 / H2 ratio of the primary raw material powder is preferably in the range of 3 to 15, and the specific surface area of the primary raw material powder is preferably in the range of 1 to 6 m ² / g.
[0015]
The dielectric ceramic having the composition represented by the general formula ABO ₃ is preferably a BaTiO ₃ -based or (Ba, Ca) TiO ₃ -based dielectric ceramic.
[0016]
When the dielectric ceramic raw material powder to be obtained contains an element for adjusting characteristics, it is preferable that such an element for adjusting characteristics is added to the secondary raw material powder.
[0017]
The present invention is also directed to a dielectric ceramic raw material powder obtained by the manufacturing method as described above.
[0018]
Furthermore, the present invention includes a multilayer body including a plurality of ceramic layers and internal electrodes formed between the ceramic layers, and an external electrode formed on the outer surface of the multilayer body. It is also directed to multilayer ceramic capacitors that are electrically connected. The multilayer ceramic capacitor according to the present invention is characterized in that the ceramic layer is made of a powder sintered body containing the dielectric ceramic raw material powder according to the present invention.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 1 according to one embodiment of the present invention.
[0020]
The multilayer ceramic capacitor 1 includes a multilayer body 2. The multilayer body 2 includes a plurality of laminated ceramic layers 3 and a plurality of internal electrodes 4 and 5 formed along specific interfaces between the plurality of ceramic layers 3. The internal electrodes 4 and 5 are formed so as to reach the outer surface of the laminate 2, but the internal electrode 4 that is drawn to one end face 6 of the laminate 2 and the internal electrode that is drawn to the other end face 7. 5 are alternately arranged inside the stacked body 2.
[0021]
External electrodes 8 and 9 are formed on the outer surface of the laminate 2 on the end surfaces 6 and 7 by applying, for example, a conductive paste and then baking it. Further, first plating layers 10 and 11 are formed on the external electrodes 8 and 9 as necessary, and further, second plating layers 12 and 13 are formed thereon, respectively.
[0022]
In this way, in the multilayer ceramic capacitor 1, the plurality of internal electrodes 4 and 5 are formed so as to overlap each other in the stacking direction of the multilayer body 2, and thereby the capacitance between the adjacent internal electrodes 4 and 5. Form. In addition, the internal electrode and the external electrode 8 are electrically connected, and the internal electrode 5 and the external electrode 9 are electrically connected, whereby the above-described electrostatic electrode is connected via the external electrodes 8 and 9. The capacity is taken out.
[0023]
The ceramic layer 3 is composed of a powder sintered body containing a dielectric ceramic raw material powder produced by the production method according to the present invention. Here, the dielectric ceramic raw material powder is manufactured as follows.
[0024]
First, it is represented by the general formula ABO ₃ (where A is at least one of Ba, Ca, Sr and Mg, and B is at least one of Ti, Zr and Hf). A primary raw material powder for a dielectric ceramic having a composition is prepared.
[0025]
In order to obtain a primary raw material powder, for example, when ABO ₃ is synthesized by a solid phase reaction method, a starting raw material powder preparation step, a uniform mixing step, a drying step, a heat treatment step, and a pulverization step are sequentially performed. In order to synthesize ABO ₃ , a hydrothermal synthesis method or a hydrolysis method may be used in addition to the solid phase reaction method.
[0026]
Next, the primary raw material powder is subjected to wet pulverization. In the present invention, the firing step performed to obtain the multilayer ceramic capacitor 1 is not performed on the primary material powder, but the secondary material powder obtained by pulverizing the primary material powder. It is characterized by being implemented for.
[0027]
The pulverization treatment step for obtaining the secondary raw material powder is carried out by stirring the primary raw material powder together with boulders in a mill having a built-in stirring body such as a rotating disk, rotor or pin. In the mill, the stirring body forcibly vibrates the cobblestone, thereby exerting a dispersing and pulverizing action on the primary raw material powder.
[0028]
In the pulverization process, the stirring body is rotated at a peripheral speed of 3 to 9 m / sec. Here, the peripheral speed refers to the speed of the outermost periphery of a stirring member such as a disk, rotor, or pin.
[0029]
Moreover, as a cobblestone, a thing with a particle size of 0.5 mm or less is used, and a cobblestone is filled so that the filling rate with respect to the effective internal volume of a mill may be 70-95 volume%. Here, the filling rate of cobblestone is the volume that a plurality of cobblestones occupy as a whole when a plurality of cobblestones are put in the mill, that is, there are gaps between cobblestones, but cobblestones placed naturally The volume occupied by the outer surface of the aggregate is divided by the effective internal volume of the mill.
[0030]
As described above, when the primary raw material powder is pulverized to obtain the secondary raw material powder, between the primary raw material powder and the secondary raw material powder, the crystallinity and specific surface area are as follows. Change will be brought about.
[0031]
First, regarding crystallinity, as shown in FIG. 2, the diffraction peak intensity of the (200) plane in the X-ray diffraction analysis for each of the primary raw material powder and the secondary raw material powder is H1, and in the X-ray diffraction analysis ( When the minimum value of the diffraction intensity observed between the diffraction peak of the (002) plane and the diffraction peak of the (200) plane is H2, the secondary raw material powder is H1 / The H2 ratio is reduced by 10% or more.
[0032]
Further, with respect to the specific surface area, the secondary raw material powder is increased by 10 to 50% compared to the primary raw material powder.
[0033]
The H1 / H2 ratio and specific surface area of the primary raw material powder are not particularly limited. However, in the range H2 / H2 ratio is 3 to 15 for the primary material powder, if the specific surface area of the primary raw material powder in the range of 1~6m ² / g, as described above, H1 / H2 ratio When the decrease rate is 10% or more and the increase rate of the specific surface area is 10 to 50%, the appropriate crystallinity and specific surface area for the dielectric ceramic raw material powder can be stably obtained.
[0034]
Examples of the dielectric ceramic having a composition represented by the general formula ABO _{3 to} which the present invention is applied include a BaTiO ₃ -based or (Ba, Ca) TiO ₃ -based dielectric ceramic.
[0035]
The secondary raw material powder manufactured as described above is used as a dielectric ceramic raw material powder for manufacturing the multilayer ceramic capacitor 1. That is, a slurry is prepared by adding an organic binder and a solvent to the dielectric ceramic raw material powder, and adding and mixing elements for characteristic adjustment as necessary, and using this slurry. A ceramic green sheet to be the ceramic layer 3 is formed.
[0036]
Next, a conductive paste film to be the internal electrodes 4 and 5 is formed on the specific ceramic green sheet by, for example, screen printing. This conductive paste film contains, for example, a base metal such as nickel or copper or an alloy thereof as a conductive component.
[0037]
Next, a plurality of ceramic green sheets on which a conductive paste film is formed as described above are laminated, and a ceramic green sheet on which no conductive paste film is formed is laminated so as to sandwich these ceramic green sheets. After being done, the raw laminated body which should become the laminated body 2 is obtained by cutting as needed.
[0038]
Next, the raw laminate is fired, for example, in a reducing atmosphere. Thereby, the laminated body 2 after sintering as shown in FIG. 1 is obtained.
[0039]
Next, external electrodes 8 and 9 are formed on the end surfaces 6 and 7 of the multilayer body 2 so as to be electrically connected to the exposed edges of the internal electrodes 4 and 5, respectively. The external electrodes 8 and 9 are formed, for example, by applying and baking a conductive paste containing nickel, copper, silver, palladium, or an alloy thereof as a conductive component.
[0040]
Thereafter, if necessary, first plating layers 10 and 11 made of, for example, nickel or copper are formed on external electrodes 8 and 9, and second plating layer 12 made of, for example, solder or tin is further formed thereon. 13 is formed, and the multilayer ceramic capacitor 1 is completed.
[0041]
Next, experimental examples carried out to confirm the effects of the present invention will be described.
[0042]
Dielectric ceramic raw material powder according to each of Examples 1 to 5 and Comparative Examples 1 to 5 was produced as follows.
[0043]
[Table 1]

[0044]
First, primary raw material powders having “H1 / H2 ratio of primary raw material powder” and “specific surface area of primary raw material powder” as shown in Table 1 were prepared. Here, as the primary raw material powder, BaTiO ₃ powder was used in Examples 1, 3 and 4 and Comparative Examples 1, 3 and 4, and (Ba _0.99 Ca _{0. 5)} was used in Example 2 and Comparative Example 2 _{. 01} ) TiO ₃ powder was used, and in Example 5 and Comparative Example 5, (Ba _0.952 Ca _0.048 ) (Ti _0.99 Zr _0.01 ) O ₃ powder was used.
[0045]
Next, 10 kg of the primary raw material powder was slurried with 20 liters of ion-exchanged water.
[0046]
Next, the slurry was pulverized by a bead mill. Here, a cobblestone made of PSZ having a “cobble diameter” as shown in Table 1 is used, and this is filled in a bead mill with a “cobble filling ratio” as shown in Table 1, The pulverization process was carried out according to “speed”.
[0047]
The secondary raw material powder obtained by the above pulverization treatment exhibited “decrease rate of H1 / H2 ratio” and “increase rate of specific surface area” as shown in Table 1 as compared with the primary raw material powder.
[0048]
Next, in the slurry containing the secondary raw material powder after the pulverization treatment, in Examples 1, 3 and 4 and Comparative Examples 1, 3 and 4, with respect to 100 mol of BaTiO ₃ , in Example 2 and Comparative Example 2, For (Ba _0.99 Ca _0.01 ) TiO ₃ 100 mol, and in Example 5 and Comparative Example 5, (Ba _0.952 Ca _0.048 ) (Ti _0.99 Zr _0.01 ) O _{3 With} respect to 100 moles, Mg, Dy, Mn, Ni and Si are added as element for property adjustment so as to have a composition of 1.5Mg-2.5Dy-0.5Mn-0.2Ni-2.0Si, Drying was performed to obtain a dielectric ceramic raw material powder.
[0049]
Next, using the above dielectric ceramic raw material powder, a multilayer ceramic capacitor in which the thickness of the ceramic layer located between the internal electrodes was 3.0 μm and the number of stacked internal electrodes was 50 was produced.
[0050]
Regarding the multilayer ceramic capacitors according to each of Examples 1 to 5 and Comparative Examples 1 to 5 thus obtained, as shown in Table 2, “relative permittivity”, “capacitance temperature characteristic”, and “average failure time” Was evaluated.
[0051]
The “relative dielectric constant” is a value obtained by measuring the relative dielectric constant of the dielectric ceramic constituting the ceramic layer of each multilayer ceramic capacitor under the conditions of a temperature of 25 ° C., 1 kHz, and 0.5 V _rms .
[0052]
“Capacitance-temperature characteristic” was evaluated whether or not the X7R characteristic of the EIA standard was satisfied. The capacitance change rate at −55 ° C. and the capacitance at 125 ° C. based on the capacitance at 25 ° C. The rate of change was determined.
[0053]
The “average failure time” is the average value of the time until the multilayer ceramic capacitor as a sample fails until a voltage of 60 V is continuously applied at a temperature of 150 ° C.
[0054]
[Table 2]

[0055]
In Examples 1 to 5, as shown in Table 1, the “H1 / H2 ratio of the primary raw material powder” is in the range of 3 to 15, and the “specific surface area of the primary raw material powder” is 1 to 6 m ² / g. The “cobble diameter” is 0.5 mm or less, the “cobble filling rate” is in the range of 70 to 95% by volume, and the “peripheral speed” is in the range of 3 to 9 m / sec. The “decrease rate of the H / H2 ratio” is 10% or more, and the “increase rate of the specific surface area” is in the range of 10 to 50%.
[0056]
As a result, in Examples 1 to 5, as shown in Table 2, the “relative dielectric constant” is satisfied, the “capacitance temperature characteristic” satisfies the X7R characteristic of the EIA standard, and the “average failure time” is also compared. A highly reliable monolithic ceramic capacitor was obtained with a long time. These preferable characteristics are considered to have been obtained as follows.
[0057]
In Examples 1-5, the primary raw material powder was wet pulverized under the pulverization conditions as shown in Table 1 to damage the particle surface of the primary raw material powder, and the secondary after the pulverization treatment. In the raw material powder, the crystallinity is lowered, so that the solid solution of the additive component is promoted. In addition, the specific surface area is increased by the pulverization, the reactivity with the additive component is increased, and the solid solution is promoted. In this way, by promoting solid solution, segregation of the added component is less likely to occur, and as a result, reliability is increased. Further, by controlling the “cobble diameter” and “peripheral speed” in pulverization as shown in Table 1, the degree of decrease in crystallinity and increase in specific surface area was adjusted. The X7R characteristic of the EIA standard can be satisfied.
[0058]
In contrast to Examples 1-5, first, in Comparative Example 1, as shown in Table 1, the “peripheral speed” is less than 3 m / sec, and the crushing force is weak. Therefore, the “decrease rate of the H1 / H2 ratio” was as low as 5%, the degree of decrease in crystallinity was not sufficient, and the “increase rate of specific surface area” was as low as 8% and was not sufficient. As a result, segregation of the added component was likely to occur, and as shown in Table 2, the “average failure time” was short and the reliability was low.
[0059]
In Comparative Example 2, as shown in Table 1, the “cobble diameter” was larger than 0.5 mm, the pulverization proceeded too much, and the “increase rate of specific surface area” was as high as 60%. As a result, as shown in Table 2, the “capacitance temperature characteristic” did not satisfy the X7R characteristic of the EIA standard.
[0060]
In Comparative Example 3, as shown in Table 1, the “peripheral speed” exceeded 9 m / sec, the pulverization progressed too much, and the “increase rate of specific surface area” was as high as 65%. As a result, as shown in Table 2, the “capacitance temperature characteristic” did not satisfy the X7R characteristic of the EIA standard.
[0061]
In Comparative Example 4, as shown in Table 1, the “H1 / H2 ratio of the primary raw material powder” is less than 3 and the “specific surface area of the primary raw material powder” exceeds 6 m ² / g. The cobblestone filling rate was as high as 100%. Therefore, the pulverization progressed too much, and the “increase rate of specific surface area” was as high as 60%. As shown in Table 2, the “capacitance temperature characteristic” did not satisfy the X7R characteristic of the EIA standard.
[0062]
In Comparative Example 5, as shown in Table 1, the “H1 / H2 ratio of the primary raw material powder” exceeds 15 and the “specific surface area of the primary raw material powder” is less than 1 m ² / g. The cobblestone filling rate was as low as 65% by volume. Therefore, the “decrease rate of H1 / H2 ratio” was as low as 7%, the crystallinity was not sufficiently lowered, and the “increase rate of specific surface area” was as low as 9%. For this reason, segregation of the additive components is likely to occur, and as shown in Table 2, the “average failure time” was short and the reliability was low.
[0063]
【The invention's effect】
As described above, according to the method for producing a dielectric ceramic raw material powder according to the present invention, the primary raw material powder for the dielectric ceramic is pulverized to obtain the secondary raw material powder, and the pulverization treatment is performed. In the process, in a mill with a built-in stirring body rotating at a peripheral speed of 3 to 9 m / sec, a particle diameter of 0.5 mm filled so that the filling rate with respect to the effective internal volume of the mill is 70 to 95 volume%. The primary raw material powder is stirred together with the following boulders, thereby reducing the H1 / H2 ratio, which is the diffraction intensity ratio of the secondary raw material powder, by 10% or more than that of the primary raw material powder, and the secondary Since the specific surface area of the raw material powder is increased by 10 to 50% from that of the primary raw material powder, the following effects are exhibited.
[0064]
That is, in the pulverization process, the particle surface of the primary raw material powder is damaged, the crystallinity of the secondary raw material powder after pulverization is lowered, and the solid solution of additive components such as the characteristic adjusting element is promoted. . In addition, the specific surface area is increased and the reactivity with the additive component is increased, which also promotes solid solution. Further, by promoting solid solution in this way, segregation of additive components is less likely to occur, and the reliability of multilayer ceramic electronic components such as multilayer ceramic capacitors configured with the obtained dielectric ceramic raw material powder is increased. can do.
[0065]
Therefore, when the dielectric ceramic raw material powder to be obtained contains an element for characteristic adjustment, the effect described above can be more reliably achieved by adding such an element for characteristic adjustment to the secondary raw material powder. Can enjoy.
[0066]
In addition, by controlling the pulverization conditions as described above, the degree of decrease in crystallinity and the degree of increase in specific surface area in the secondary raw material powder can be adjusted, and good temperature characteristics can be maintained.
[0067]
For this reason, if a multilayer ceramic capacitor is constructed using the dielectric ceramic raw material powder produced by the production method according to the present invention, a multilayer ceramic capacitor having high reliability and good capacity-temperature characteristics can be obtained. Obtainable.
[0068]
In the method for producing a dielectric ceramic raw material powder according to the present invention, the H1 / H2 ratio of the primary raw material powder is in the range of 3 to 15, and the specific surface area of the primary raw material powder is in the range of 1 to 6 m ² / g. When the pulverization conditions according to the present invention are applied, the dielectric ceramic raw material powder has a reduction rate of the H1 / H2 ratio of 10% or more and an increase rate of the specific surface area of 10 to 50% as described above. Therefore, it is possible to stably obtain crystallinity and specific surface area suitable for the above.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 1 according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating the diffraction peak intensity H1 on the (200) plane and the minimum value H2 of the diffraction intensity found between the diffraction peak on the (002) plane and the diffraction peak on the (200) plane in X-ray diffraction analysis. is there.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Laminated body 3 Ceramic layers 4, 5 Internal electrode 8, 9 External electrode

Claims (6)

A composition represented by the general formula ABO ₃ (wherein A is at least one of Ba, Ca, Sr and Mg, and B is at least one of Ti, Zr and Hf). Preparing a primary raw material powder for a dielectric ceramic having:
Crushing the primary raw material powder, thereby obtaining a secondary raw material powder,
In the pulverization step, in a mill having a built-in stirrer rotating at a peripheral speed of 3 to 9 m / sec, the particles filled so that the filling rate with respect to the effective internal volume of the mill is 70 to 95% by volume It is carried out by stirring the primary raw material powder together with a cobblestone having a diameter of 0.5 mm or less,
The diffraction peak intensity on the (200) plane in the X-ray diffraction analysis for each of the primary raw material powder and the secondary raw material powder is H1, and the diffraction peak on the (002) plane and the (200) plane in the X-ray diffraction analysis are the same. When the minimum value of the diffraction intensity found between the diffraction peaks is H2, the pulverization process reduces the H1 / H2 ratio by 10% or more compared to the primary raw material powder in the secondary raw material powder. In addition, the pulverization conditions are set so that the specific surface area is increased by 10 to 50%.
A method for producing a dielectric ceramic raw material powder. The dielectric ceramic raw material according to claim 1, wherein the H1 / H2 ratio of the primary raw material powder is in the range of 3 to 15, and the specific surface area of the primary raw material powder is in the range of 1 to 6 m ² / g. Powder manufacturing method. The dielectric ceramic raw material powder according to claim 1 or 2, wherein the dielectric ceramic having a composition represented by the general formula ABO ₃ is a BaTiO ₃ based or (Ba, Ca) TiO ₃ based dielectric ceramic. Method. The method for producing a dielectric ceramic raw material powder according to any one of claims 1 to 3, further comprising a step of adding an element for adjusting characteristics to the secondary raw material powder. A dielectric ceramic raw material powder obtained by the production method according to claim 1. A laminate comprising a plurality of ceramic layers and internal electrodes formed between the ceramic layers, and an external electrode formed on an outer surface of the laminate, wherein the internal electrodes and the external electrodes are electrically A multilayer ceramic capacitor, wherein the ceramic layer is formed of a powder sintered body containing the dielectric ceramic raw material powder according to claim 5.

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