JP5853574B2 - Method for producing nickel-coated dielectric particles - Google Patents
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本発明は、ニッケル被覆誘電体粒子の製造方法に関し、詳しくは、高温における焼成に際して収縮開始温度が高く、従って、例えば、積層セラミックコンデンサの内部電極に好適に用いることができるニッケル被覆誘電体粒子の製造方法に関する。 The present invention relates to a method for producing nickel-coated dielectric particles. More specifically, the present invention relates to a method for producing nickel-coated dielectric particles, which has a high shrinkage start temperature upon firing at a high temperature, and can be suitably used, for example, as an internal electrode of a multilayer ceramic capacitor. It relates to a manufacturing method.
ニッケル微粒子は、例えば、積層セラミックコンデンサの内部電極、ニッケル水素二次電池の多孔性電極、燃料電池の中空多孔質電極をはじめ、種々の電極を形成するための材料として注目されている。 Nickel fine particles are attracting attention as materials for forming various electrodes including, for example, internal electrodes of multilayer ceramic capacitors, porous electrodes of nickel metal hydride secondary batteries, and hollow porous electrodes of fuel cells.
従来、積層セラミックコンデンサは、誘電体グリーンシート上にパラジウム、白金等のような内部電極のための貴金属粉末とエチルセルロースのような有機バインダーとターピネオールのような有機溶媒を混練してなる導電ペーストを印刷し、乾燥して、上記誘電体グリーンシート上に内部電極層の前駆体を形成し、これと上記誘電体グリーンシートが交互に重なるように積層し、熱圧着し、次いで、このようにして得られた積層体を所定の寸法に裁断した後、２５０〜４００℃程度に加熱して、上記有機バインダーを燃焼させて除去する脱バインダー処理し、この後、積層体を約１３００℃の温度まで加熱し、焼成して、内部電極層とセラミック誘電体とを焼結させ、この後、銀等の外部電極を形成して、製造される。上記誘電体グリーンシートは、例えば、チタン酸バリウム等のセラミック誘電体粉末とポリビニルブチラールやエチルセルロースのような有機バインダーからなる。 Conventionally, multilayer ceramic capacitors are printed with a conductive paste made by kneading a noble metal powder for internal electrodes such as palladium and platinum, an organic binder such as ethyl cellulose, and an organic solvent such as terpineol on a dielectric green sheet. And drying to form a precursor of the internal electrode layer on the dielectric green sheet, laminating the dielectric green sheet and the dielectric green sheet alternately, thermocompression bonding, and then obtaining in this way The resulting laminate is cut to a predetermined size, heated to about 250 to 400 ° C. to remove the organic binder by burning, and then the laminate is heated to a temperature of about 1300 ° C. Then, firing is performed to sinter the internal electrode layer and the ceramic dielectric, and thereafter, an external electrode made of silver or the like is formed and manufactured. The dielectric green sheet is made of, for example, a ceramic dielectric powder such as barium titanate and an organic binder such as polyvinyl butyral or ethyl cellulose.
このような積層セラミックコンデンサは、最近の電子部品の高性能化に伴って、小型化と高容量化が進んでおり、そのために、セラミック誘電体と内部電極の薄膜化と多層化が一層求められている。他方、コストへの配慮から、電極のための材料は、従来のパラジウム、白金等の貴金属から、より低廉なニッケル等の卑金属が多く用いられるようになってきている。 Such multilayer ceramic capacitors have been increasingly miniaturized and increased in capacity with the recent increase in performance of electronic components. For this reason, the ceramic dielectric and internal electrodes are required to be made thinner and multilayered. ing. On the other hand, in consideration of cost, the base material such as nickel, which is cheaper, is often used as the material for the electrode from the conventional noble metals such as palladium and platinum.
しかし、ニッケル微粒子を含め、一般に、金属からなる内部電極材料は、セラミック誘電体よりも焼結開始温度が低く、しかも、熱収縮が大きい。従って、セラミック誘電体と内部電極とは熱収縮の程度が異なるので、積層セラミックコンデンサの製造において、上述したように、導電性ペーストを印刷したセラミック誘電体グリーンシートを積層し、これを焼成する際に、その間に剥離やクラック等の構造欠陥が発生しやすいという問題がある。このような構造欠陥は、特に、近年の積層セラミックコンデンサの小型化と高容量化と共に顕著に発生する傾向がある。 However, generally, internal electrode materials made of metal, including nickel fine particles, have a lower sintering start temperature and a larger thermal shrinkage than ceramic dielectrics. Therefore, since the degree of thermal shrinkage differs between the ceramic dielectric and the internal electrode, when manufacturing the multilayer ceramic capacitor, as described above, when the ceramic dielectric green sheet printed with the conductive paste is laminated and fired. In addition, there is a problem that structural defects such as peeling and cracking are likely to occur during this period. Such a structural defect tends to be particularly prominent with the recent reduction in size and capacity of multilayer ceramic capacitors.
このような問題に対処するために、一般に、導電ペーストに誘電体グリーンシートにおける誘電体と同じ誘電体の微粒子を配合して、導電ペーストの熱収縮挙動を誘電体グリーンシートのそれに近付けることができることが知られている（特許文献１参照）。しかしながら、近年のニッケル粒子の微粒子化に伴い、誘電体層と内部電極層の収縮特性の差異は大きくなる傾向にある。 In order to cope with such a problem, generally, the conductive paste can be blended with the same fine particles of dielectric as the dielectric in the dielectric green sheet so that the thermal shrinkage behavior of the conductive paste can be brought close to that of the dielectric green sheet. Is known (see Patent Document 1). However, the difference in shrinkage characteristics between the dielectric layer and the internal electrode layer tends to increase as the nickel particles become finer in recent years.
そこで、積層セラミックコンデンサの更なる薄層化を実現するには、内部電極に用いるニッケル微粒子として、高温での焼成において、焼結挙動をセラミック誘電体に近づけて、急激な収縮が始まる温度（以下、単に収縮開始温度という。）の高いものが強く求められている。 Therefore, in order to realize further thinning of the multilayer ceramic capacitor, as the nickel fine particles used for the internal electrode, when firing at a high temperature, the sintering behavior is brought close to the ceramic dielectric, and the temperature at which rapid shrinkage begins (hereinafter referred to as “the fine ceramic particles”). There is a strong demand for a material having a high shrinkage start temperature).
このような要望に応えるために、例えば、ニッケル粒子の表面に酸化チタンやチタン酸バリウム等の酸化物被覆を施して、ニッケル粒子の収縮開始温度を高めることが提案されているが、未だ、その効果は十分とはいい難い（特許文献２参照）。 In order to meet such a demand, for example, it has been proposed to increase the shrinkage start temperature of nickel particles by applying an oxide coating such as titanium oxide or barium titanate on the surface of nickel particles. It is difficult to say that the effect is sufficient (see Patent Document 2).
そこで、所謂ポリオール法を用いて、還元剤と反応溶媒を兼ねるエチレングリコールに所定の一次粒子径を有するチタン酸バリウム粒子と共に水酸化ニッケルを懸濁させた懸濁液中において、金属ニッケルを析出させることによって、母相としてのニッケル粒子内に複数のチタン酸バリウム粒子を含有していると共に、一部のチタン酸バリウム粒子が上記ニッケル粒子から突出している構造を有するニッケル粒子が提案されているが、依然として、収縮開始温度を十分に高めることは困難である（特許文献３参照）。 Therefore, by using a so-called polyol method, nickel metal is precipitated in a suspension in which nickel hydroxide is suspended together with barium titanate particles having a predetermined primary particle size in ethylene glycol which also serves as a reducing agent and a reaction solvent. Thus, nickel particles having a structure in which a plurality of barium titanate particles are contained in the nickel particles as a parent phase and some of the barium titanate particles protrude from the nickel particles have been proposed. Still, it is difficult to sufficiently increase the shrinkage start temperature (see Patent Document 3).
本発明は、従来のニッケル微粒子の収縮開始温度に関わる問題を解決するためになされたものであって、高温での焼成に際して、その焼結挙動をセラミック誘電体に近づけて、収縮開始温度を高くしたニッケル被覆誘電体粒子を製造する方法を提供することを目的とする。 The present invention was made to solve the conventional problems related to the shrinkage start temperature of nickel fine particles. When firing at a high temperature, the sintering behavior is brought close to a ceramic dielectric to increase the shrinkage start temperature. It is an object of the present invention to provide a method for producing the nickel-coated dielectric particles.
本発明によれば、表面に貴金属又はその塩を担持させた誘電体粒子とニッケル化合物を含むポリオール中において、上記ニッケル化合物を上記誘電体粒子の表面上でニッケルに還元して析出させることを特徴とするニッケル被覆誘電体粒子の製造方法が提供される。 According to the present invention, in a polyol containing a nickel particle and a dielectric particle carrying a noble metal or a salt thereof on the surface, the nickel compound is reduced to nickel and deposited on the surface of the dielectric particle. method for producing a nickel coating Yuden particles to is provided.
本発明によれば、上記方法における表面に貴金属塩を担持させた誘電体粒子は、誘電体粒子をその懸濁液中、上記貴金属の水溶性塩で処理して、得ることができる。 According to the present invention, dielectric particles having a noble metal salt supported on the surface in the above method can be obtained by treating the dielectric particles with the water-soluble salt of the noble metal in the suspension.
また、本発明によれば、上記方法における表面に貴金属を担持させた誘電体粒子は、誘電体粒子をその懸濁液中、上記貴金属の水溶性塩で処理して、表面に上記貴金属塩を担持させた誘電体粒子を得、次いで、誘電体粒子の表面の上記貴金属塩を還元剤にて貴金属に還元して、得ることができる。 Further, according to the present invention, the dielectric particles having the surface supported with the noble metal in the above method are obtained by treating the dielectric particles with the water-soluble salt of the noble metal in the suspension thereof, and applying the noble metal salt on the surface. Obtained dielectric particles can be obtained, and then the noble metal salt on the surface of the dielectric particles can be reduced to a noble metal with a reducing agent.
本発明によれば、誘電体粒子の１つの好ましい例はチタン酸バリウム粒子であり、貴金属の１つの好ましい例はパラジウムであり、ポリオールの１つの好ましい例はエチレングリコールであり、ニッケル化合物の好ましい具体例は水酸化ニッケルである。 According to the present invention, one preferred example of dielectric particles is barium titanate particles, one preferred example of noble metal is palladium, one preferred example of polyol is ethylene glycol, and a preferred embodiment of nickel compounds. An example is nickel hydroxide.
このような本発明の方法によって得られるニッケル被覆誘電体粒子は、高温での焼成に際して、収縮開始温度が高く、セラミック誘電体の焼結挙動に近いので、例えば、積層セラミックコンデンサの内部電極として好適に用いることができる。 The nickel-coated dielectric particles obtained by the method of the present invention have a high shrinkage start temperature when firing at a high temperature and are close to the sintering behavior of a ceramic dielectric. Can be used.
本発明によるニッケル被覆誘電体粒子の製造方法は、表面に貴金属又はその塩を担持させた誘電体粒子とニッケル化合物を含むポリオール中において、上記ニッケル化合物を上記誘電体粒子の表面上でニッケルに還元して析出させることを特徴とする。 Method for producing a nickel coating Yuden particles according to the present invention is a noble metal or dielectric particles and a polyol containing a nickel compound is supported a salt thereof to the surface, the nickel compound to nickel on the surface of the dielectric particles It is characterized by being reduced and precipitated.
本発明において、誘電体としては、ペロブスカイト構造を有する複合酸化物が好ましく、そのような誘電体として、例えば、チタン酸バリウム（ＢａＴｉＯ3）、チタン酸ストロンチウム（ＳｒＴｉＯ3）、チタン酸ジルコン酸鉛（Ｐｂ（Ｚｒ，Ｔｉ）Ｏ3）、ジルコン酸カルシウム（ＣａＺｒＯ3）、チタン酸カルシウム（ＣａＴｉＯ3）、ジルコン酸バリウム（ＢａＺｒＯ3）、チタン酸ジルコン酸バリウムカルシウム（Ｂａ，Ｃａ）(Ｔｉ，Ｚｒ）Ｏ3等を挙げることができる。これらのなかで、チタン酸バリウムは、本発明において、誘電体として好ましく用いることができる１つである。 In the present invention, the dielectric is preferably a composite oxide having a perovskite structure. Examples of such a dielectric include barium titanate (BaTiO 3 ), strontium titanate (SrTiO 3 ), and lead zirconate titanate ( Pb (Zr, Ti) O 3 ), calcium zirconate (CaZrO 3 ), calcium titanate (CaTiO 3 ), barium zirconate (BaZrO 3 ), barium calcium zirconate titanate (Ba, Ca) (Ti, Zr) O 3 etc. can be mentioned. Among these, barium titanate is one that can be preferably used as a dielectric in the present invention.
上記誘電体粒子は、その平均粒子径が０．０１〜１．０μｍの範囲内にあり、特に、０．０３〜０．２μｍの範囲にあることが好ましい。誘電体粒子の平均粒子径が０．０１μｍよりも小さいときは、その凝集性が強いために誘電体粒子に均一なニッケル被覆を施すことが困難となるおそれがある。 The dielectric particles have an average particle diameter in the range of 0.01 to 1.0 μm, and particularly preferably in the range of 0.03 to 0.2 μm. When the average particle diameter of the dielectric particles is smaller than 0.01 μm, it is difficult to apply a uniform nickel coating on the dielectric particles because of its strong cohesiveness.
一方、誘電体粒子の平均粒子径が１μｍよりも大きいときは、このような誘電体粒子にニッケル被覆を施してなる粒子を用いて積層セラミックコンデンサの内部電極を形成したときに、その表面平滑性が損なわれて、セラミック層との密着性が損なわれるおそれがある。 On the other hand, when the average particle diameter of the dielectric particles is larger than 1 μm, the surface smoothness of the multilayer ceramic capacitor when the internal electrodes of the multilayer ceramic capacitor are formed using particles obtained by coating the dielectric particles with nickel. May be impaired, and the adhesiveness with the ceramic layer may be impaired.
本発明によれば、このように、誘電体粒子の表面に貴金属又はその塩を担持させてなる一種の複合体（以下、貴金属（塩）担持誘電体粒子ということがある。）を調製し、これとニッケル化合物を含むポリオール中において、ポリオールを還元剤とする所謂ポリオール法にて上記ニッケル化合物を上記誘電体粒子の表面上でニッケルに還元して析出させ、かくして、ニッケル被覆誘電体粒子を得る。 According to the present invention, in this way, a kind of composite (hereinafter sometimes referred to as noble metal (salt) -supported dielectric particles) in which a surface of dielectric particles is supported with a noble metal or a salt thereof is prepared. in the polyol containing the same and a nickel compound, a polyol of the above nickel compounds are precipitated by reducing the nickel on the surface of the dielectric particles at a so-called polyol method in which a reducing agent, thus, the nickel-coated Yuden particles obtain.
上記ポリオール法とは、金属ナノ粒子の一般的な液相合成法としてよく知られており、還元剤を兼ねるポリオール溶媒中、金属塩を好ましくは加熱することによって、上記金属塩を還元して金属微粒子を得る方法である。 The polyol method is well known as a general liquid phase synthesis method for metal nanoparticles, and the metal salt is reduced to a metal by preferably heating the metal salt in a polyol solvent that also serves as a reducing agent. This is a method for obtaining fine particles.
上記ポリオールとしては、例えば、脂肪族ポリオールが好ましく、例えば、具体例として、エチレングリコール、ジエチレングリコール、トリエチレングリコール、テトラエチレングリコール、１，２−プロパンジオール、ジプロピレングリコール、１，２−ブタンジオール、１，３−ブタンジオール、１，４−ブタンジオール、２，３−ブタンジオール１，５−ペンタンジオール、ポリエチレングリコール等を挙げることができる。本発明においては、これらから選ばれる少なくとも１種が好ましく用いられる。なかでも、エチレングリコールは、比較的沸点が低い常温で液状の物質であるので、取り扱いやすく、好ましく用いられる。
As the polyol, for example, an aliphatic polyol is preferable. For example, as specific examples, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, dipropylene glycol, 1,2-butanediol, Examples include 1,3-butanediol, 1,4-butanediol, 2,3-
本発明によれば、上記貴金属（塩）担持誘電体粒子における貴金属又はその塩は、誘電体粒子表面上でニッケル化合物を還元し、析出させるための触媒であり、従来、ニッケル化合物のニッケル金属への還元に用いられている貴金属触媒又は貴金属塩触媒であれば、いずれでも用いることができる。 According to the present invention, the noble metal or the salt thereof in the noble metal (salt) -supported dielectric particle is a catalyst for reducing and precipitating the nickel compound on the surface of the dielectric particle. Any noble metal catalyst or noble metal salt catalyst used in the reduction can be used.
上記貴金属触媒としては、例えば、パラジウム、銀、白金、金等を挙げることができ、上記貴金属塩触媒としては、上記貴金属の塩を挙げることができる。従って、上記貴金属塩触媒としては、例えば、塩化パラジウム、硝酸パラジウム、酢酸パラジウム、塩化アンモニウムパラジウム等のパラジウム塩、硝酸銀、乳酸銀、酸化銀、硫酸銀、シクロヘキサン酸銀、酢酸銀等の銀塩、塩化白金酸、塩化白金酸カリウム、塩化白金酸ナトリウム等の白金化合物、塩化金酸、塩化金酸ナトリウム等の金化合物を挙げることができる。これらのうち、塩化パラジウムや硝酸パラジウムのような水溶性パラジウム塩は、触媒性能にすぐれるために好ましく用いられる。 Examples of the noble metal catalyst include palladium, silver, platinum, and gold. Examples of the noble metal salt catalyst include salts of the noble metal. Accordingly, examples of the noble metal salt catalyst include palladium salts such as palladium chloride, palladium nitrate, palladium acetate, and ammonium palladium chloride, silver salts such as silver nitrate, silver lactate, silver oxide, silver sulfate, silver cyclohexane acid, and silver acetate. Examples thereof include platinum compounds such as chloroplatinic acid, potassium chloroplatinate, and sodium chloroplatinate, and gold compounds such as chloroauric acid and sodium chloroaurate. Of these, water-soluble palladium salts such as palladium chloride and palladium nitrate are preferably used because of their excellent catalytic performance.
本発明によれば、誘電体粒子の表面にこのような貴金属塩を担持させるには、好ましくは、誘電体粒子をその懸濁液中、上記貴金属の水溶性塩で処理した後、洗浄することによって得ることができる。より具体的には、誘電体粒子を水中に懸濁させ、この懸濁液に上記貴金属の水溶性塩を加え、攪拌した後、水洗すればよく、このようにして、貴金属塩担持誘電体粒子を得ることができる。 According to the present invention, in order to carry such a noble metal salt to the surface of the induction conductor particles, preferably, the suspension in the dielectric particles, after being treated with a water-soluble salt of the noble metal, and washed Can be obtained. More specifically, the dielectric particles are suspended in water, the water-soluble salt of the noble metal is added to the suspension, and the mixture is stirred and then washed with water. Can be obtained.
このような貴金属塩担持誘電体粒子を得るために用いる上記貴金属の水溶性塩としては、上述したように、塩化パラジウム、硝酸パラジウム、酢酸パラジウム、塩化アンモニウムパラジウム等のパラジウム塩、硝酸銀、乳酸銀、酸化銀、硫酸銀、シクロヘキサン酸銀、酢酸銀等の銀塩、塩化白金酸、塩化白金酸カリウム、塩化白金酸ナトリウム等の白金化合物、塩化金酸、塩化金酸ナトリウム等の金化合物を挙げることができる。これらのうち、塩化パラジウムや硝酸パラジウムのような水溶性パラジウム塩は、触媒性能にすぐれるために好ましく用いられる。 Examples of the water-soluble salt of the noble metal used for obtaining such noble metal salt-supported dielectric particles include palladium salts such as palladium chloride, palladium nitrate, palladium acetate, and ammonium palladium chloride, silver nitrate, silver lactate, List silver salts such as silver oxide, silver sulfate, silver cyclohexane acid, silver acetate, platinum compounds such as chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, and gold compounds such as chloroauric acid and sodium chloroaurate. Can do. Of these, water-soluble palladium salts such as palladium chloride and palladium nitrate are preferably used because of their excellent catalytic performance.
一方、誘電体粒子の表面に貴金属を担持させるには、好ましくは、誘電体粒子をその懸濁液中、上記貴金属の水溶性塩で処理した後、洗浄して、表面に上記貴金属塩を担持させた誘電体粒子を得、次いで、誘電体粒子の表面の上記貴金属塩を還元剤にて貴金属に還元して、誘電体粒子の表面に上記貴金属を析出させる。より具体的には、誘電体粒子を水中に懸濁させ、この懸濁液に上記貴金属の水溶性塩を加え、攪拌した後、水洗して、表面に上記貴金属塩を担持させた誘電体粒子を得、次いで、誘電体粒子の表面の上記貴金属塩を還元剤にて貴金属に還元して、誘電体粒子の表面に上記貴金属を析出させた後、水洗すればよい。 On the other hand, in order to support a noble metal on the surface of the induction conductor particles, preferably, the suspension in the dielectric particles, after being treated with a water-soluble salt of the noble metal, is washed, the noble metal salt on the surface The supported dielectric particles are obtained, and then the noble metal salt on the surface of the dielectric particles is reduced to the noble metal with a reducing agent, and the noble metal is deposited on the surface of the dielectric particles. More specifically, dielectric particles are prepared by suspending dielectric particles in water, adding the water-soluble salt of the noble metal to the suspension, stirring, washing with water, and supporting the noble metal salt on the surface. Then, the noble metal salt on the surface of the dielectric particles is reduced to a noble metal with a reducing agent to deposit the noble metal on the surface of the dielectric particles, and then washed with water.
このような貴金属担持誘電体粒子を得るために用いる上記貴金属の水溶性塩としても、上述したと同じく、塩化パラジウム、硝酸パラジウム、酢酸パラジウム、塩化アンモニウムパラジウム等のパラジウム塩、硝酸銀、乳酸銀、酸化銀、硫酸銀、シクロヘキサン酸銀、酢酸銀等の銀塩、塩化白金酸、塩化白金酸カリウム、塩化白金酸ナトリウム等の白金化合物、塩化金酸、塩化金酸ナトリウム等の金化合物等を挙げることができる。これらのうち、塩化パラジウムや硝酸パラジウムのような水溶性パラジウム塩は、触媒性能にすぐれるために好ましく用いられる。 As described above, the water-soluble salt of the noble metal used for obtaining such noble metal-supported dielectric particles is the same as described above, such as palladium chloride, palladium nitrate, palladium acetate, ammonium chloride palladium palladium salt, silver nitrate, silver lactate, oxidation. Examples include silver salts such as silver, silver sulfate, silver cyclohexane acid and silver acetate, platinum compounds such as chloroplatinic acid, potassium chloroplatinate and sodium chloroplatinate, and gold compounds such as chloroauric acid and sodium chloroaurate. Can do. Of these, water-soluble palladium salts such as palladium chloride and palladium nitrate are preferably used because of their excellent catalytic performance.
上記貴金属担持誘電体粒子の調製において用いる前記還元剤には、例えば、ヒドラジン、ヒドラジン水和物、水素化ホウ素塩、次亜リン酸塩等が用いられるが、なかでも、反応後に残渣が生じないこと、比較的安全性が高いこと等から、ヒドラジン水和物の一種であるヒドラジン一水和物が好ましく用いられる。このような還元剤は、上述した貴金属塩、好ましくは、パラジウム塩に対して、通常、等量の割合で用いられる。 As the reducing agent used in the preparation of the noble metal-supported dielectric particles, for example, hydrazine, hydrazine hydrate, borohydride, hypophosphite, etc. are used, and no residue is produced after the reaction. In view of relatively high safety, hydrazine monohydrate, which is a kind of hydrazine hydrate, is preferably used. Such a reducing agent is usually used in an equivalent ratio with respect to the above-mentioned noble metal salt, preferably palladium salt.
このようにして、誘電体粒子の表面に貴金属を担持させた後、得られた懸濁液を固液分離し、水洗して、貴金属担持誘電体粒子を得ることができる。 In this way, after the noble metal is supported on the surface of the dielectric particles, the resulting suspension is subjected to solid-liquid separation and washed with water to obtain noble metal-supported dielectric particles.
本発明によれば、このようにして、貴金属又はその塩を担持した誘電体粒子を調製し、これとニッケル化合物を含むポリオール中において、上記ニッケル化合物を上記誘電体粒子の表面上で還元し、ニッケルを析出させることによって、目的とするニッケル被覆誘電体粒子を得る。 According to the present invention, in this way, dielectric particles carrying a noble metal or a salt thereof are prepared, and in the polyol containing the nickel compound, the nickel compound is reduced on the surface of the dielectric particles, by precipitating the nickel, obtain nickel coating Yuden particles of interest.
本発明の方法において、誘電体粒子をその懸濁液中、水溶性の貴金属塩で処理して、誘電体粒子上に上記貴金属塩を付着、担持させた後、誘電体粒子を水洗しても、おそらくは誘電体粒子と上記貴金属塩の間に強い相互作用が生じる結果であるとみられるが、誘電体粒子上の上記貴金属塩はその表面から殆ど除去されない。同様に、誘電体粒子上に付着担持された貴金属塩をその懸濁液中、還元剤にて貴金属に還元した後、誘電体粒子を水洗しても、誘電体粒子上の上記貴金属は表面から殆ど除去されない。 In the method of the present invention, the dielectric particles are treated with a water-soluble noble metal salt in the suspension, and the dielectric particles are washed with water after the noble metal salt is adhered and supported on the dielectric particles. Perhaps the result is a strong interaction between the dielectric particles and the noble metal salt, but the noble metal salt on the dielectric particles is hardly removed from the surface. Similarly, even if the noble metal salt adhered and supported on the dielectric particles is reduced to the noble metal with a reducing agent in the suspension, and the dielectric particles are washed with water, the noble metal on the dielectric particles is not removed from the surface. Almost no removal.
かくして、本発明によれば、誘電体粒子上にこのようにして付着担持された貴金属又はその塩を核として、ニッケル化合物が還元されるので、誘電体粒子表面には効果的にニッケル被覆が形成され、その結果として、本発明によるニッケル被覆誘電体粒子は、熱収縮温度が大幅に高温側に移動するものとみられる。 Thus, according to the present invention, the nickel compound is reduced using the noble metal or salt thereof deposited and supported on the dielectric particles in this manner as a nucleus, so that a nickel coating is effectively formed on the surface of the dielectric particles. As a result, the nickel-coated dielectric particles according to the present invention are considered to have a heat shrinkage temperature that moves significantly to the high temperature side.
上記貴金属（塩）担持誘電体粒子の調製において用いる上記水溶性の貴金属塩は、後述するように、得られる貴金属（塩）担持誘電体粒子の表面でニッケル化合物を還元し、ニッケルを析出させて、誘電体粒子の表面に所要量のニッケル被覆を形成させることができれば、特に、その使用量は制限されるものではないが、貴金属換算にて、通常、誘電体粒子１００重量部当りに０．００１〜０．１重量部程度であり、好ましくは、０．００２〜０．０５重量部程度である。
As described later, the water-soluble noble metal salt used in the preparation of the noble metal (salt) -carrying dielectric particles is obtained by reducing the nickel compound on the surface of the obtained noble metal (salt) -carrying dielectric particles and depositing nickel. if it is possible to form the required amount of nickel coating on the surface of the dielectric particles, in particular, the amount used but are not limited, 0 in precious metal conversion, usually, in the dielectric particles per 100 parts by weight. The amount is about 001 to 0.1 parts by weight, and preferably about 0.002 to 0.05 parts by weight.
上記ニッケル化合物は、特に、限定されることはなく、例えば、水酸化ニッケル、炭酸ニッケル、硫酸ニッケル、硝酸ニッケル、塩化ニッケル、臭化ニッケル、酢酸ニッケル等を挙げることができるが、これらのなかでは、例えば、水酸化ニッケルが好ましく用いられる。これらのニッケル化合物は、後述するように、得られるニッケル被覆誘電体粒子における誘電体粒子の割合が５〜２０重量％の範囲となるように用いられる。 The nickel compound is not particularly limited, and examples thereof include nickel hydroxide, nickel carbonate, nickel sulfate, nickel nitrate, nickel chloride, nickel bromide, nickel acetate, and the like. For example, nickel hydroxide is preferably used. As described later, these nickel compounds are used so that the ratio of the dielectric particles in the obtained nickel-coated dielectric particles is in the range of 5 to 20% by weight.
本発明において、ポリオール中、ニッケル化合物を還元し、貴金属（塩）担持誘電体粒子の表面にニッケルを析出させるに際して、好ましくは、ポリオール中に貴金属（塩）担持誘電体粒子とニッケル化合物と共に分散剤を存在させることが好ましい。この分散剤としては、有機ポリマーからなるものが好ましく、例えば、ポリビニルピロリドン、ポリエチレンイミン、ポリアクリルアミド、ポリ（２−メチル−２−オキサゾリン）、ポリビニルアルコール等を挙げることができる。例えば、ポリビニルピロリドンは、好ましく用いることができる分散剤の１つである。 In the present invention, when the nickel compound is reduced in the polyol and nickel is deposited on the surface of the noble metal (salt) -carrying dielectric particles, it is preferable that the dispersing agent together with the noble metal (salt) -carrying dielectric particles and the nickel compound in the polyol. Is preferably present. As this dispersing agent, what consists of organic polymers is preferable, For example, polyvinylpyrrolidone, polyethyleneimine, polyacrylamide, poly (2-methyl-2-oxazoline), polyvinyl alcohol, etc. can be mentioned. For example, polyvinylpyrrolidone is one of the dispersants that can be preferably used.
本発明において、前記ポリオールは、還元剤を兼ねる溶媒として用いられる。従って、その使用量は、上記ニッケル化合物の還元剤として足りる量であればよいが、好ましくは、通常、溶媒としての観点から、貴金属（塩）担持誘電体粒子とニッケル化合物と分散剤とポリオールの合計量の５０重量％以上を占める割合にて用いられる。 In the present invention, the polyol is used as a solvent that also serves as a reducing agent. Therefore, the amount used may be an amount sufficient as a reducing agent for the nickel compound, but preferably, from the viewpoint of a solvent, the noble metal (salt) -carrying dielectric particles, the nickel compound, the dispersant, and the polyol are usually used. It is used in a ratio that accounts for 50% by weight or more of the total amount.
上記貴金属（塩）担持誘電体粒子とニッケル化合物と分散剤を含むポリオールを加熱することによって、このポリオールを還元剤として上記ニッケル化合物を効率よく上記誘電体粒子の表面上で還元し、ニッケルを析出させることができる。上記加熱温度、即ち、反応温度は、通常、１５０〜２１０℃の範囲であり、好ましくは、１６０〜２００℃の範囲であり、特に、１８０〜２００℃の範囲である。反応温度が１５０℃よりも低いときは、還元反応が遅すぎて、工業的実用性に乏しい。しかし、反応温度が２１０℃よりも高いときは、望ましくない副反応が起こるようになるため好ましくない。 By heating the noble metal (salt) -carrying dielectric particles, a polyol containing a nickel compound and a dispersant, the nickel compound is efficiently reduced on the surface of the dielectric particles by using the polyol as a reducing agent, and nickel is deposited. Can be made. The heating temperature, that is, the reaction temperature is usually in the range of 150 to 210 ° C, preferably in the range of 160 to 200 ° C, and particularly in the range of 180 to 200 ° C. When the reaction temperature is lower than 150 ° C., the reduction reaction is too slow and the industrial practicality is poor. However, when the reaction temperature is higher than 210 ° C., an undesirable side reaction occurs, which is not preferable.
上記貴金属（塩）担持誘電体粒子とニッケル化合物を含むポリオールを加熱する時間、即ち、反応時間は、用いるポリオールや金属ニッケルの種類、反応温度等によるので、一概に定めることはできないが、通常、１〜１０時間の範囲であり、好ましくは、３〜８時間の範囲である。 The time for heating the polyol containing the noble metal (salt) -carrying dielectric particles and the nickel compound, that is, the reaction time depends on the kind of polyol and metal nickel used, the reaction temperature, etc. The range is 1 to 10 hours, preferably 3 to 8 hours.
このようにして、ポリオール中、貴金属（塩）担持誘電体粒子の表面にニッケルを析出させた後、得られた懸濁液を室温まで降温させ、得られたニッケル被覆誘電体粒子を固液分離し、温水とエタノールでこの順序で洗浄し、例えば、１１０℃で乾燥すれば、本発明によるニッケル被覆誘電体粒子を得ることができる。 In this way, after depositing nickel on the surface of the noble metal (salt) -carrying dielectric particles in the polyol, the resulting suspension is cooled to room temperature, and the resulting nickel-coated dielectric particles are solid-liquid separated. The nickel-coated dielectric particles according to the present invention can be obtained by washing with warm water and ethanol in this order and drying at 110 ° C., for example.
本発明においては、このようにして得られるニッケル被覆誘電体粒子において、誘電体粒子の割合は、通常、５〜２０重量％の範囲である。ニッケル被覆誘電体粒子において、誘電体粒子の割合が５重量％よりも少ないときは、このようなニッケル被覆誘電体粒子を用いて、積層セラミックコンデンサの内部電極を形成すれば、収縮遅延効果が低いために、得られる積層セラミックコンデンサに層間剥離やクラック等の構造欠陥が生じるおそれがある。一方、ニッケル被覆誘電体粒子において、誘電体粒子の割合が２０重量％よりも多いときは、このようなニッケル被覆誘電体粒子を用いて積層セラミックコンデンサの内部電極を形成すれば、電極層の電気抵抗が大きくなって、積層セラミックコンデンサとしての品質のばらつきが大きくなるおそれがある。 In the present invention, in the nickel-coated dielectric particles thus obtained, the ratio of the dielectric particles is usually in the range of 5 to 20% by weight. In the nickel-coated dielectric particles, when the proportion of the dielectric particles is less than 5% by weight, if the internal electrode of the multilayer ceramic capacitor is formed using such nickel-coated dielectric particles, the shrinkage delay effect is low. Therefore, structural defects such as delamination and cracks may occur in the obtained multilayer ceramic capacitor. On the other hand, in the nickel-coated dielectric particles, when the ratio of the dielectric particles is more than 20% by weight, the internal electrode of the multilayer ceramic capacitor can be formed using such nickel-coated dielectric particles. As the resistance increases, there is a risk that variations in quality as a multilayer ceramic capacitor will increase.
以下に実施例と比較例を挙げて本発明を説明するが、本発明はこれら実施例によって何ら限定されるものではない。尚、以下の実施例及び比較例において、出発物質チタン酸バリウム粒子と得られたニッケル被覆誘電体粒子の平均粒子径と、得られたニッケル被覆誘電体粒子の粉末Ｘ線回折と、得られたニッケル被覆誘電体粒子における誘電体の割合と収縮特性は次のようにして求め、又は評価した。 Hereinafter, the present invention will be described with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the average particle diameter of the starting material barium titanate particles and the obtained nickel-coated dielectric particles, and the powder X-ray diffraction of the obtained nickel-coated dielectric particles were obtained. The ratio of the dielectric and the shrinkage characteristics in the nickel-coated dielectric particles were determined or evaluated as follows.
（出発物質チタン酸バリウム粒子およびニッケル被覆誘電体粒子の平均粒子径）
日本電子（株）製走査電子顕微鏡ＪＳＭ−７０００Ｆを用いて撮影したＳＥＭ写真像から平均粒子径を算出した。
（ニッケル被覆誘電体粒子の粉末Ｘ線回折）
（株）リガク製Ｘ線回折装置ＲＩＮＴ−ＴＴＲ IIIを用いて測定した。
（ニッケル被覆誘電体粒子における誘電体の割合）
（株）リガク製蛍光Ｘ線分析装置Ｐｒｉｍｕｓ IIを用いて求めた。
（ニッケル被覆誘電体粒子の収縮特性）
得られたニッケル被覆チタン酸バリウム粒子を２Ｔ／ｃｍ2で圧縮して、ペレットに成形し、このペレットを熱分析装置（（株）リガク製ＴＭＡ８３１０）を用いて、水素２％、残部窒素の雰囲気中、昇温速度５℃／分で加熱したときの収縮特性を測定した。
(Average particle size of starting material barium titanate particles and nickel-coated dielectric particles)
The average particle diameter was calculated from SEM photograph images taken using a scanning electron microscope JSM-7000F manufactured by JEOL Ltd.
(Powder X-ray diffraction of nickel-coated dielectric particles)
It measured using Rigaku Co., Ltd. X-ray-diffraction apparatus RINT-TTRIII.
(Percentage of dielectric in nickel-coated dielectric particles)
It calculated | required using Rigaku Co., Ltd. product fluorescent X-ray-analysis apparatus Primus II.
(Shrinkage characteristics of nickel-coated dielectric particles)
The obtained nickel-coated barium titanate particles were compressed at 2 T / cm 2 and formed into pellets, and the pellets were subjected to an atmosphere of 2% hydrogen and the balance nitrogen using a thermal analyzer (TMA8310 manufactured by Rigaku Corporation). The shrinkage characteristics when heated at a heating rate of 5 ° C./min were measured.
実施例１
１００ｍＬ容量の広口のポリエチレン製の瓶に平均粒子径０．１μｍのチタン酸バリウム (堺化学工業（株）製ＢＴ０１) ２０ｇとイオン交換水を入れて総量４０ｍＬの懸濁液とした。この懸濁液に直径１．５ｍｍのジルコニアビーズ４０ｍＬを加え、２００ｒｐｍにて１５分間遊星ミルにて粉砕処理した。この粉砕処理の後、懸濁液から上記ビーズを分離し、得られた懸濁液を攪拌機にて３００ｒｐｍで攪拌しながら、塩化パラジウム水溶液をパラジウム換算でチタン酸バリウム１ｇ当り０．４ｍｇとなるように１０ｍＬ／分の割合で滴下した。塩化パラジウム水溶液の滴下終了後、６０分間攪拌し、この後、水洗した。
Example 1
20 g of barium titanate having an average particle size of 0.1 μm (BT01 manufactured by Sakai Chemical Industry Co., Ltd.) and ion-exchanged water were put into a 100 mL capacity wide-mouth polyethylene bottle to make a total suspension of 40 mL. To this suspension, 40 mL of zirconia beads having a diameter of 1.5 mm was added, and pulverized with a planetary mill at 200 rpm for 15 minutes. After this pulverization treatment, the beads were separated from the suspension, and the resulting suspension was stirred at 300 rpm with a stirrer so that the palladium chloride aqueous solution was 0.4 mg per 1 g of barium titanate in terms of palladium. Was added dropwise at a rate of 10 mL / min. After completion of the dropwise addition of the palladium chloride aqueous solution, the mixture was stirred for 60 minutes and then washed with water.
次いで、得られたチタン酸バリウム粒子の懸濁液を攪拌しながら、これに８０重量％濃度のヒドラジン水溶液をパラジウム量に対して当量滴下し、撹拌した後、水洗して、パラジウムを担持させたチタン酸バリウム粒子の懸濁液を得た。 Next, while stirring the obtained suspension of barium titanate particles, an 80% by weight aqueous hydrazine solution was added dropwise to the amount of palladium, and the mixture was stirred and washed with water to support palladium. A suspension of barium titanate particles was obtained.
ゲル状の水酸化ニッケルの懸濁液（水酸化ニッケルとして５．２６ｇ）にエチレングリコール１００ｍＬとポリビニルピロリドン水溶液２０ｍＬ（ポリビニルピロリドンとして４ｇ）を加え、攪拌した後、これに前記パラジウムを担持させたチタン酸バリウム粒子の懸濁液 （チタン酸バリウムとして０．５ｇ）とエチレングリコール１００ｍＬを加え、１８５℃で４時間加熱して、水酸化ニッケルをチタン酸バリウム粒子上で還元し、かくして、ニッケル被覆チタン酸バリウム粒子を含む懸濁液を得た。 To a gel-like nickel hydroxide suspension (5.26 g as nickel hydroxide), 100 mL of ethylene glycol and 20 mL of polyvinylpyrrolidone aqueous solution (4 g as polyvinylpyrrolidone) were added and stirred, and then titanium on which the palladium was supported was added. Add a suspension of barium acid particles (0.5 g as barium titanate) and 100 mL of ethylene glycol and heat at 185 ° C. for 4 hours to reduce nickel hydroxide on the barium titanate particles, thus nickel coated titanium A suspension containing barium acid particles was obtained.
ニッケル被覆チタン酸バリウム粒子を含む懸濁液を室温まで降温し、ニッケル被覆チタン酸バリウム粒子を濾過によって集め、温水とエタノールでこの順序で洗浄した後、１１０℃で一晩乾燥した。 The suspension containing nickel-coated barium titanate particles was cooled to room temperature, and the nickel-coated barium titanate particles were collected by filtration, washed in this order with warm water and ethanol, and then dried at 110 ° C. overnight.
このようにして得られたニッケル被覆チタン酸バリウム粒子の平均粒子径は０．２μｍであり、得られたニッケル被覆チタン酸バリウム粒子は、その粉末X線回折パターンを図１に示すように、ニッケル金属とチタン酸バリウムの回折線が観測された。更に、得られたニッケル被覆チタン酸バリウム粒子におけるチタン酸バリウム量は１３重量％であった。得られたニッケル被覆チタン酸バリウム粒子の収縮特性を図２に示す。 The nickel-coated barium titanate particles thus obtained had an average particle size of 0.2 μm, and the obtained nickel-coated barium titanate particles had a powder X-ray diffraction pattern as shown in FIG. Metal and barium titanate diffraction lines were observed. Furthermore, the amount of barium titanate in the nickel-coated barium titanate particles obtained was 13% by weight. The shrinkage characteristics of the nickel-coated barium titanate particles obtained are shown in FIG.
実施例２
ゲル状の水酸化ニッケルの懸濁液（水酸化ニッケルとして５．２６ｇ）にエチレングリコール１００ｍＬとポリビニルピロリドン水溶液２０ｍＬ（ポリビニルピロリドンとして４ｇ）を加え、攪拌した後、これに実施例１におけると同じパラジウムを担持させたチタン酸バリウム粒子の懸濁液 （チタン酸バリウムとして０．７７ｇ）とエチレングリコール１００ｍＬを加え、１８０℃で５時間加熱して、水酸化ニッケルをチタン酸バリウム粒子上で還元し、かくして、ニッケル被覆チタン酸バリウム粒子を含む懸濁液を得た。
Example 2
100 mL of ethylene glycol and 20 mL of polyvinylpyrrolidone aqueous solution (4 g as polyvinylpyrrolidone) were added to a gel-like nickel hydroxide suspension (5.26 g as nickel hydroxide), stirred, and the same palladium as in Example 1 was added thereto. Suspension of barium titanate particles carrying 0.77 g (0.77 g as barium titanate) and 100 mL of ethylene glycol were added and heated at 180 ° C. for 5 hours to reduce nickel hydroxide on the barium titanate particles, Thus, a suspension containing nickel-coated barium titanate particles was obtained.
ニッケル被覆チタン酸バリウム粒子を含む懸濁液を室温まで降温し、ニッケル被覆チタン酸バリウム粒子を濾過し、温水とエタノールでこの順序で洗浄した後、１１０℃で一晩乾燥した。 The suspension containing the nickel-coated barium titanate particles was cooled to room temperature, the nickel-coated barium titanate particles were filtered, washed with warm water and ethanol in this order, and then dried at 110 ° C. overnight.
このようにして得られたニッケル被覆チタン酸バリウム粒子の平均粒子径は０．２μｍであり、得られたニッケル被覆チタン酸バリウム粒子は、その粉末X線回折パターンを図 ３に示すように、ニッケル金属とチタン酸バリウムの回折線が観測された。更に、得られたニッケル被覆チタン酸バリウム粒子におけるチタン酸バリウム量は１８重量％であった。得られたニッケル被覆チタン酸バリウム粒子の収縮特性を図４に示す。 The nickel-coated barium titanate particles thus obtained had an average particle size of 0.2 μm. The obtained nickel-coated barium titanate particles had a powder X-ray diffraction pattern as shown in FIG. Metal and barium titanate diffraction lines were observed. Furthermore, the amount of barium titanate in the nickel-coated barium titanate particles obtained was 18% by weight. FIG. 4 shows the shrinkage characteristics of the obtained nickel-coated barium titanate particles.
実施例３
１００ｍＬ容量の広口のポリエチレン製の瓶に平均粒子径０．０５μｍのチタン酸バリウム (堺化学工業（株）製ＢＴ００５) ２０ｇとイオン交換水を入れて総量４０ｍＬの懸濁液とした。この懸濁液に直径１．５ｍｍのジルコニアビーズ４０ｍＬを加え、２００ｒｐｍにて１５分間遊星ミルにて粉砕処理した。この粉砕処理の後、懸濁液から上記ビーズを分離し、得られた懸濁液を攪拌機にて３００ｒｐｍで攪拌しながら、塩化パラジウム水溶液をパラジウム換算でチタン酸バリウム１ｇ当り０．４ｍｇとなるように滴下した。塩化パラジウム水溶液の滴下終了後、攪拌し、水洗して、塩化パラジウムを担持させチタン酸バリウム粒子の懸濁液を得た。
Example 3
20 g of barium titanate having a mean particle size of 0.05 μm (BT005 manufactured by Sakai Chemical Industry Co., Ltd.) and ion-exchanged water were put into a 100 mL capacity wide-mouth polyethylene bottle to make a total suspension of 40 mL. To this suspension, 40 mL of zirconia beads having a diameter of 1.5 mm was added, and pulverized with a planetary mill at 200 rpm for 15 minutes. After this pulverization treatment, the beads were separated from the suspension, and the resulting suspension was stirred at 300 rpm with a stirrer so that the palladium chloride aqueous solution was 0.4 mg per 1 g of barium titanate in terms of palladium. It was dripped in. After completion of the dropwise addition of the palladium chloride aqueous solution, the mixture was stirred and washed with water to carry palladium chloride and obtain a suspension of barium titanate particles.
ゲル状の水酸化ニッケルの懸濁液（水酸化ニッケルとして５．２６ｇ）にエチレングリコール１００ｍＬとポリビニルピロリドン水溶液２０ｍＬ（ポリビニルピロリドンとして４ｇ）を加え、攪拌した後、これに前記塩化パラジウムを担持させたチタン酸バリウム粒子の懸濁液 （チタン酸バリウムとして０．５ｇ）とエチレングリコール１００ｍＬを加え、１８５℃で４時間加熱して、水酸化ニッケルをチタン酸バリウム粒子上で還元し、かくして、ニッケル被覆チタン酸バリウム粒子を含む懸濁液を得た。 100 mL of ethylene glycol and 20 mL of polyvinylpyrrolidone aqueous solution (4 g as polyvinylpyrrolidone) were added to a gelled nickel hydroxide suspension (5.26 g as nickel hydroxide) and stirred, and then the palladium chloride was supported thereon. Add suspension of barium titanate particles (0.5 g as barium titanate) and 100 mL of ethylene glycol and heat at 185 ° C. for 4 hours to reduce nickel hydroxide on barium titanate particles, thus nickel coated A suspension containing barium titanate particles was obtained.
ニッケル被覆チタン酸バリウム粒子を含む懸濁液を室温まで降温し、ニッケル被覆チタン酸バリウム粒子を濾過し、温水とエタノールでこの順序で洗浄した後、１１０℃で一晩乾燥した。 The suspension containing the nickel-coated barium titanate particles was cooled to room temperature, the nickel-coated barium titanate particles were filtered, washed with warm water and ethanol in this order, and then dried at 110 ° C. overnight.
このようにして得られたニッケル被覆チタン酸バリウム粒子の平均粒子径は０．１５μｍであり、得られたニッケル被覆チタン酸バリウム粒子は、その粉末X線回折パターンを図５に示すように、ニッケル金属とチタン酸バリウムの回折線が観測された。更に、得られたニッケル被覆チタン酸バリウム粒子におけるチタン酸バリウム量は１３重量％であった。得られたニッケル被覆チタン酸バリウム粒子の収縮特性を図６に示す。 The nickel-coated barium titanate particles thus obtained had an average particle size of 0.15 μm, and the obtained nickel-coated barium titanate particles had a powder X-ray diffraction pattern as shown in FIG. Metal and barium titanate diffraction lines were observed. Furthermore, the amount of barium titanate in the nickel-coated barium titanate particles obtained was 13% by weight. FIG. 6 shows the shrinkage characteristics of the obtained nickel-coated barium titanate particles.
比較例１
カルボキシメチルセルロースナトリウム０．０９８ｇを加熱、溶融させ、これに塩化ニッケル５１．８ｇを溶解して、総容量を２５０ｍＬとした。得られた塩化ニッケル溶液を攪拌しながら、８０重量％濃度のヒドラジン水溶液と水酸化ナトリウム水溶液を加えた。これを６０℃に加熱し、塩化ニッケルを還元して、ニッケル粒子を得た。得られたニッケル粒子を洗浄した後、１１０℃で一晩乾燥した。
Comparative Example 1
0.098 g of sodium carboxymethylcellulose was heated and melted, and 51.8 g of nickel chloride was dissolved in it to make a total volume of 250 mL. While stirring the resulting nickel chloride solution, an 80 wt% aqueous hydrazine solution and an aqueous sodium hydroxide solution were added. This was heated to 60 ° C. and nickel chloride was reduced to obtain nickel particles. The obtained nickel particles were washed and dried at 110 ° C. overnight.
このようにして得られた平均一次粒子径０．２μｍのニッケル粒子に平均粒子径０．１μｍのチタン酸バリウム粒子（堺化学工業（株）製ＢＴ０１）１３重量％加え、乳鉢にて混合した。得られた混合粉体を２Ｔ／ｃｍ2で圧縮し、ペレットに成形し、実施例１におけると同様にして、その収縮特性を測定した。結果を図２、図４及び図６に示す。 13% by weight of barium titanate particles (BT01 manufactured by Sakai Chemical Industry Co., Ltd.) having an average particle size of 0.1 μm were added to the nickel particles having an average primary particle size of 0.2 μm thus obtained and mixed in a mortar. The obtained mixed powder was compressed at 2 T / cm 2 , formed into pellets, and the shrinkage characteristics were measured in the same manner as in Example 1. The results are shown in FIG. 2, FIG. 4 and FIG.
実施例１、実施例２及び実施例３によるニッケル被覆チタン酸バリウム粒子の収縮特性と上記比較例１によるニッケル粒子とチタン酸バリウム粒子との混合粉体からなる粒子の収縮特性を比較すれば明らかなように、本発明によるニッケル被覆チタン酸バリウム粒子は、高温での焼成において、収縮開始温度が大幅に高温側に移動しており、セラミック誘電体の焼結挙動に近い。 It is clear when the shrinkage characteristics of the nickel-coated barium titanate particles according to Example 1, Example 2 and Example 3 are compared with the shrinkage characteristics of particles made of a mixed powder of nickel particles and barium titanate particles according to Comparative Example 1 above. As described above, the nickel-coated barium titanate particles according to the present invention have a shrinkage start temperature greatly moved to a high temperature side in firing at a high temperature, which is close to the sintering behavior of a ceramic dielectric.
比較例２
１００ｍＬ容量の広口のポリエチレン製の瓶に平均粒子径０．１μｍのチタン酸バリウム (堺化学工業（株）製ＢＴ０１) ２０ｇとイオン交換水を入れて総量４０ｍＬの懸濁液とした。この懸濁液に直径１．５ｍｍのジルコニアビーズ４０ｍＬを加え、２００ｒｐｍにて１５分間遊星ミルにて粉砕処理した。この粉砕処理の後、懸濁液から上記ビーズを分離して、チタン酸バリウム粒子の懸濁液を得た。
Comparative Example 2
20 g of barium titanate having an average particle size of 0.1 μm (BT01 manufactured by Sakai Chemical Industry Co., Ltd.) and ion-exchanged water were put into a 100 mL capacity wide-mouth polyethylene bottle to make a total suspension of 40 mL. To this suspension, 40 mL of zirconia beads having a diameter of 1.5 mm was added, and pulverized with a planetary mill at 200 rpm for 15 minutes. After the pulverization treatment, the beads were separated from the suspension to obtain a suspension of barium titanate particles.
ゲル状の水酸化ニッケルの懸濁液（水酸化ニッケルとして５．２６ｇ）にエチレングリコール１００ｍＬとポリビニルピロリドン水溶液２０ｍＬ（ポリビニルピロリドンとして４ｇ）を加え、攪拌した後、これに上記チタン酸バリウム粒子の懸濁液（チタン酸バリウムとして０．５ｇ）と塩化パラジウム水溶液（パラジウム換算でチタン酸バリウム１ｇ当り０．４ｍｇ）とエチレングリコール１００ｍＬを加え、１８５℃で４時間加熱して、水酸化ニッケルを還元した。 To a gelled nickel hydroxide suspension (5.26 g as nickel hydroxide), 100 mL of ethylene glycol and 20 mL of polyvinylpyrrolidone aqueous solution (4 g as polyvinylpyrrolidone) were added and stirred, and then the above barium titanate particles were suspended. A suspension (0.5 g as barium titanate), an aqueous palladium chloride solution (0.4 mg per 1 g of barium titanate in terms of palladium) and 100 mL of ethylene glycol were added and heated at 185 ° C. for 4 hours to reduce nickel hydroxide. .
得られた懸濁液を室温まで降温し、このように処理したチタン酸バリウム粒子を濾過して集め、温水とエタノールでこの順序で洗浄した後、１１０℃で一晩乾燥した。このようにして得られた粒子の平均粒子径は０．２μｍであり、また、図７に示すように、得られた粒子の粉末X線回折において、ニッケル金属とチタン酸バリウムの回折線が観測された。更に、蛍光Ｘ線分析によって、得られた粒子におけるチタン酸バリウム量は１３重量％であった。 The obtained suspension was cooled to room temperature, and the barium titanate particles thus treated were collected by filtration, washed in this order with warm water and ethanol, and then dried at 110 ° C. overnight. The average particle diameter of the particles thus obtained is 0.2 μm, and as shown in FIG. 7, diffraction lines of nickel metal and barium titanate are observed in the powder X-ray diffraction of the obtained particles. It was done. Furthermore, the amount of barium titanate in the obtained particles was 13 wt% by fluorescent X-ray analysis.
得られた粒子を２Ｔ／ｃｍ2で圧縮して、ペレットに成形し、実施例１におけると同様にして、その収縮特性を測定した。結果を図８に示す。 The obtained particles were compressed at 2 T / cm 2 and formed into pellets, and the shrinkage characteristics were measured in the same manner as in Example 1. The results are shown in FIG.
実施例１によるニッケル被覆チタン酸バリウム粒子の収縮特性と上記比較例２による粒子の収縮特性を比較すれば明らかなように、本発明によるニッケル被覆チタン酸バリウム粒子は高温での焼成において、収縮開始温度が大幅に高温側に移動しており、セラミック誘電体の焼結挙動に近い。 As is clear from the comparison between the shrinkage characteristics of the nickel-coated barium titanate particles according to Example 1 and the shrinkage characteristics of the particles according to Comparative Example 2, the nickel-coated barium titanate particles according to the present invention start shrinkage when fired at a high temperature. The temperature has moved significantly to the high temperature side, which is close to the sintering behavior of a ceramic dielectric.
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