JP2013139599A - Metal powder, method for producing the same, conductive paste, and method for producing laminated ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, for matching the shrinkage behavior upon co-firing between an internal electrode and a ceramic layer as much as possible, and as metal powder included in conductive paste forming the internal electrode, the one in which the grain thereof is covered with an oxide for thermal shrinkage suppression is frequently used, but the oxide may be peeled when temperature is made high in a firing process.SOLUTION: A particle 1 composing metal powder includes: a core material 2 consisting of a metal as a main component; and an external layer 3 consisting of an oxide which is arranged so as to cover at least a part of the outer surface of the core material 2. Further, the particle 1 includes an intermediate layer 4 formed along the boundary face between the core material 2 and the external layer 3. The intermediate layer 4 has a thickness of ≥0.2 nm and also includes the oxide of the metal used as a main component of the core material 2 formed by subjecting the core material 2 to heat treatment in an oxygen-containing atmosphere, wherein the oxide is different from the oxide composing the external layer 3. The intermediate layer 4 acts so as to suppress the peeling of the external layer 3 from the core material 2.

Description

  The present invention relates to a metal powder, a method for producing the same, a conductive paste, and a method for producing a multilayer ceramic electronic component, and in particular, is composed of particles having a form in which a metal-based core material is covered with an oxide. The present invention relates to a metal powder and a method for manufacturing the same, a conductive paste containing the metal powder, and a method for manufacturing a multilayer ceramic electronic component that is performed using the conductive paste.

  Metal powders of interest for the present invention are described in, for example, JP-A-11-343501 (Patent Document 1) and JP-A-2000-63901 (Patent Document 2).

Patent Document 1 describes a metal powder suitable as a material for an internal electrode of a multilayer ceramic capacitor. That is, Patent Document 1 describes composite nickel fine powder, and this composite nickel fine powder is formed on the surface of nickel fine powder particles by TiO ₂ , MnO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , In the presence of at least one oxide selected from SiO ₂ , Y ₂ O ₃ , ZrO _2, and BaTiO ₃ , the rapid thermal shrinkage start temperature is higher than around 600 to 700 ° C. And the nickel metal in the nickel fine powder particles is hardly oxidized and diffused.

  Patent Document 2 also describes a metal powder suitable as a material for an internal electrode of a multilayer ceramic capacitor. The particles constituting the metal powder described in Patent Document 2 include a core material made of Ni particles, Al, Zr, Ti, Si, Pb, Fe, W, Mn, Bi, Nb, Ta, Mo, alkaline earth And a surface layer made of an oxide of one or more elements selected from rare earth elements and covering the outer surface of the core material.

  The oxides coated with the nickel powder particles described in Patent Documents 1 and 2 suppress the shrinkage of the internal electrode during firing, thereby matching the shrinkage behavior during the simultaneous firing of the internal electrode and the ceramic layer as much as possible. As a result of the firing process, it acts to suppress the occurrence of structural defects such as delamination in the multilayer ceramic capacitor.

  However, the metal powder such as the nickel powder described in Patent Documents 1 and 2 has the following problems to be solved. In the case where the substance that coats the metal powder particles is an oxide, the oxide may be peeled off at a high temperature during the firing process, and thus the thermal shrinkage suppressing effect may be lost. As a result, it may not be possible to suppress the occurrence of structural defects such as delamination in the multilayer ceramic capacitor. Further, when the oxide layer is formed thick in order to enhance the heat shrinkage suppressing effect, the coverage of the internal electrode may be lowered.

  In particular, as the multilayer ceramic capacitor becomes smaller and thinner, the internal electrode has been made thinner. To meet this demand, the metal powder contained in the conductive paste used to form the internal electrode is finer. Must be made. However, when the atomization progresses in this way, the oxide is more easily peeled off, and thus the above problem becomes more serious.

In Patent Document 1, the surface of nickel particles in which oxides such as TiO ₂ , MnO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ , ZrO ₂ , BaTiO ₃ are present on the surface. Is previously lightly oxidized with a suitable oxidizing agent. In this case, it is presumed that the oxide film on the surface of the nickel particles has an effect of improving the bondability with the oxide.

  However, the technique described in Patent Document 1 has the following problems.

In paragraph [0012] of Patent Document 1, regarding the oxidation treatment of the surface of the nickel particles described above, “100 g of hydrogen peroxide solution was added all at once, and then filtered and dried to obtain a surface oxidation-treated nickel fine powder.” There is a description. However, in this oxidation treatment method, oxidation is caused by Ni (OH) ₂ because of oxidation in a pH adjusted solution. Therefore, Ni (OH) ₂ becomes NiO + H ₂ O at a high temperature, and H ₂ O gas is generated, leading to peeling of the oxide coating layer. Therefore, even if the surface of the nickel particles is oxidized, the problem that the heat shrinkage suppressing effect is lost cannot be solved because the oxide is peeled off at a high temperature during the heat treatment. .

Japanese Patent Laid-Open No. 11-343501 JP 2000-63901 A

  Accordingly, an object of the present invention is to provide a metal powder that can solve the above-described problems.

  Another object of the present invention is to provide a preferred method for producing the metal powder described above.

  Still another object of the present invention is to provide a conductive paste containing the above-described metal powder.

  Still another object of the present invention is to provide a method for manufacturing a multilayer ceramic electronic component which is carried out using the above-described conductive paste.

  The present invention is first directed to a metal powder comprising a plurality of particles each having a core material mainly composed of a metal and an outer layer made of an oxide disposed so as to cover at least a part of the outer surface of the core material. In order to solve the technical problem described above, a metal that is an oxide different from the oxide constituting the outer layer along the interface between the core material and the outer layer, and is a main component of the core material The intermediate layer containing an oxide other than the hydroxide is formed with a thickness of 0.2 nm or more.

  If an intermediate layer having a thickness of 0.2 nm or more containing a metal oxide as a main component of the core material is fired under a condition in which the metal is not reduced, the intermediate layer can be separated from the core material even in a high temperature region in the firing step. It acts to suppress peeling of the outer layer.

  The reason why the thickness of the intermediate layer is limited to 0.2 nm or more is to exclude a natural oxide film formed by exposure to the atmosphere.

  In addition, the outer layer and the intermediate layer are differentiated in that the metal that is the main component of the core material is contained in the intermediate layer but not in the outer layer. The metal that is the main component has a concentration distribution with a gradient from the outermost surface of the particles constituting the metal powder to the surface of the core material, and is in a state that shows the highest concentration on the surface of the core material. May be.

  The metal as the main component of the core material is preferably at least one selected from Ni, Cu, Ag and Pd. These metals can be advantageously used as a metal constituting an internal electrode of a multilayer ceramic electronic component such as a multilayer ceramic capacitor.

  When the metal that is the main component of the core material is Ni, the intermediate layer includes Ti, Zr, V, Ta, Cr, W, Mn, in addition to NiO as an oxide of the metal that is the main component of the core material. It is preferable to include an oxide of at least one metal selected from Fe, Co and Cu. A composite oxide is formed by these metal oxides and NiO, and the wettability of the intermediate layer with respect to both the core material and the outer layer can be improved.

  It is preferable that at least one of the intermediate layer and the outer layer covers an area of 30 to 100% of the surface of the core material. This is because the heat shrinkage suppressing effect during firing by the outer layer can be more reliably exhibited.

  The thickness of the outer layer is preferably 0.2 to 50 nm. By setting the thickness of the outer layer to 0.2 nm or more, the heat shrinkage suppressing effect during firing by the outer layer can be more reliably exhibited. On the other hand, by setting the thickness to 50 nm or less, the outer layer was formed using the metal powder. The coverage after firing of the electrode can be increased.

  The thickness of the intermediate layer is preferably 50 nm or less. This is because the coverage after firing of the electrode formed using the metal powder can be increased.

  The core material preferably has a particle size of 5 to 1000 nm. When the particle diameter is in the range of 5 to 1000 nm, the effect of suppressing structural defects of the multilayer ceramic electronic component including the internal electrode formed using the metal powder is enhanced.

  The present invention also includes a core material mainly composed of a metal, and an outer layer made of an oxide disposed so as to cover at least a part of the outer surface of the core material, and the core material and the outer layer Also directed to a method for producing a metal powder, in which an intermediate layer containing an oxide of a metal that is different from the oxide constituting the outer layer along the interface and that is the main component of the core material is formed. It is done.

  The method for producing metal powder according to the present invention includes a step of preparing a core material, and an intermediate layer containing an oxide formed by oxidizing the surface of the core material by heat-treating the core material in an oxygen-containing atmosphere. An intermediate layer forming step of forming with a thickness of 2 nm or more, and an outer layer forming step of forming the outer layer by adding an oxide constituting the outer layer to the core material on which the intermediate layer is formed. It is said.

  In the above-described intermediate layer forming step, heat treatment in an oxygen-containing atmosphere is applied, so if a core material mainly composed of Ni is taken as an example, a NiO oxide film is reliably formed on the surface of the core material. .

  The present invention is further directed to a conductive paste in which the above-described metal powder is dispersed in an organic vehicle.

  The present invention is further directed to a method for manufacturing a multilayer ceramic electronic component. A method for manufacturing a multilayer ceramic electronic component according to the present invention includes a raw multilayer body including a plurality of laminated ceramic green sheets and internal electrodes formed between the ceramic green sheets using the conductive paste described above. It is characterized by comprising a step of preparing and a step of firing the raw laminate.

In the firing step described above, the logarithmic difference between the oxygen partial pressure PO ₂ in the firing atmosphere and the equilibrium oxygen partial pressure PO _{20 in the} core material: log (PO ₂ / PO ₂₀ ) is selected in the range of 0 to 7.5. Is preferred. Thereby, since the oxide which comprises an intermediate | middle layer can be baked without reduction | restoration, the joining property of a core material and an outer layer does not fall.

  According to the metal powder according to the present invention, since the peeling of the outer layer of the particles constituting the metal powder is suppressed until reaching the high temperature region in the firing step, the effect of suppressing thermal shrinkage by the oxide constituting the outer layer is maintained. .

  Therefore, when the internal electrode of the multilayer ceramic electronic component is formed using the conductive paste containing the metal powder, delamination during firing is suppressed. In addition, in order to enhance the heat shrinkage suppression effect and maintain it more reliably, it is not necessary to form the outer layer so thick, so even if the thickness of the internal electrode is reduced to, for example, 0.5 μm or less, the coverage ratio Is reduced.

Further, according to the metal powder and the method for producing the same according to the present invention, in the intermediate layer forming step, heat treatment in an oxygen-containing atmosphere is applied to the core material, so that the core material contained in the intermediate layer is mainly processed. Since a metal oxide as a component is formed, a hydroxide is not formed, and H ₂ O gas that leads to peeling of the outer layer at a high temperature is not generated.

It is sectional drawing which expands and shows typically the one particle | grains 1 which comprise the metal powder by one Embodiment of this invention. It is sectional drawing which shows the multilayer ceramic capacitor 11 as an example of the multilayer ceramic electronic component manufactured favorably using the metal powder concerning this invention.

  With reference to FIG. 1, the particle | grains 1 which comprise the metal powder by one Embodiment of this invention are demonstrated.

  The particle 1 has a core material 2 mainly composed of a metal and an outer layer 3 made of an oxide disposed so as to cover at least a part of the outer surface of the core material 2. A feature of the present invention is that an intermediate layer 4 is formed along the interface between the core material 2 and the outer layer 3.

  The intermediate layer 4 is an oxide different from the oxide constituting the outer layer 3, and is an oxide of a metal that is a main component of the core material 2 generated by heat-treating the core material 2 in an oxygen-containing atmosphere. The thickness T1 is 0.2 nm or more.

  The metal that is the main component of the core material 1 is preferably at least one selected from Ni, Cu, Ag, and Pd.

  When the metal that is the main component of the core material 1 is Ni, the intermediate layer 4 includes NiO that is an oxide of Ni that is the main component of the core material 1. In this case, the intermediate layer 4 is at least selected from Ti, Zr, V, Ta, Cr, W, Mn, Fe, Co, and Cu in addition to NiO as a metal oxide that is the main component of the core material 1. One kind of metal oxide may be further included. Thus, a composite oxide is formed by the metal oxide and NiO, and the wettability of the intermediate layer 4 with respect to both the core material 2 and the outer layer 3 can be improved. As a result, the core of the outer layer 3 can be improved. Bondability to the material 2 can be improved.

  At least one of the intermediate layer 4 and the outer layer 3 preferably covers an area of 30 to 100% of the surface of the core material 2. This is because, as can be seen from the experimental examples described later, the heat shrinkage suppressing effect during firing by the outer layer 3 can be more reliably exhibited.

  The thickness T2 of the outer layer 3 is preferably 0.2 to 50 nm. As can be seen from the experimental examples to be described later, by setting the thickness T2 of the outer layer 3 to 0.2 nm or more, the heat shrinkage suppressing effect during firing by the outer layer 3 can be more reliably exhibited, while the thickness of the outer layer 3 is increased. By setting T2 to 50 nm or less, the coverage after firing of the electrode formed using the metal powder can be increased.

  The thickness T1 of the intermediate layer 4 is preferably 50 nm or less. This is because, as can be seen from the experimental examples described later, the coverage after firing of the electrode formed using the metal powder can be increased.

  The core material 2 preferably has a particle size D of 5 to 1000 nm. As can be seen from the experimental examples described later, the effect of suppressing structural defects in a multilayer ceramic electronic component including an internal electrode formed using the metal powder is enhanced at a particle size D in the range of 5 to 1000 nm.

  The metal powder composed of the plurality of particles 1 as described above is manufactured, for example, as follows.

  First, a core material 2 for the particles 1 is prepared. For example, commercially available Ni powder is prepared.

  Next, the surface of the core material 2 is oxidized by heat-treating the core material 2 in an oxygen-containing atmosphere. Thereby, the intermediate layer 4 containing the metal oxide as the main component of the core material 2 is formed with a thickness T1 of 0.2 nm or more. When the core material 1 contains Ni as a main component, an NiO oxide film is formed on the surface of the core material 2, and the intermediate layer 4 is formed with this NiO film.

Next, the oxide which comprises the outer layer 3 is provided to the core material 2 in which the intermediate layer 4 is formed, whereby the outer layer 3 is formed. For example, when the ceramic layer of a multilayer ceramic electronic component including an internal electrode formed using the metal powder is mainly composed of BaTiO ₃ , the oxide constituting the outer layer 3 is also composed mainly of BaTiO _3. Is preferably used. For example, a sol-gel method is applied to the formation of the outer layer 3 as described below.

  In the case where a material mainly composed of Ni is used as the core material 2, the intermediate layer forming step described above includes Ti, Zr, V, Ta, Cr, W, Mn after the heat treatment for forming the NiO film. Ti, Zr, V, Ta, Cr by hydrolyzing the metal alkoxide with the core material 2 dispersed in a metal alkoxide solution containing at least one metal selected from Fe, Co and Cu , W, Mn, Fe, Co, and at least one metal selected from Cu may be added to the surface of the core material 2.

  In the case described above, when forming the outer layer 3, it is possible to add the metal necessary for generating the oxide constituting the outer layer 3 to the metal alkoxide solution and form the outer layer 3 by a sol-gel method. preferable.

  The metal powder thus obtained is used for the production of a multilayer ceramic electronic component as a conductive paste in a form dispersed in an organic vehicle.

  With reference to FIG. 2, the structure of a multilayer ceramic capacitor 11 as an example of the multilayer ceramic electronic component will be described.

  The multilayer ceramic capacitor 11 includes a multilayer body 12 serving as a component body. The laminated body 12 has a substantially rectangular parallelepiped shape, and a plurality of laminated ceramic layers 13 and a plurality of first and second internal electrodes 14 formed along a plurality of interfaces between the ceramic layers 13 and 15. The first internal electrodes 14 and the second internal electrodes 15 are alternately arranged as viewed in the stacking direction.

  The first internal electrode 14 is drawn out to the first end face 16 of the multilayer body 12, while the second internal electrode 15 is directed to the second end face 17 that faces the first end face 16 of the multilayer body 12. It is pulled out. A first external electrode 18 is formed on the first end face 16, and the first external electrode 18 is electrically connected to the first internal electrode 14. A second external electrode 19 is formed on the second end surface 17, and the second external electrode 19 is electrically connected to the second internal electrode 15.

  In order to manufacture the multilayer ceramic capacitor 11 as described above, first, a plurality of ceramic green sheets to be the ceramic layer 13 are prepared.

  Next, in order to form the internal electrodes 14 and 15 on the ceramic green sheet, a conductive paste obtained by dispersing the above-described metal powder according to the present invention in an organic vehicle is used. That is, by printing a conductive paste, a conductive paste film to be the internal electrodes 14 and 15 is formed on the ceramic green sheet.

  Next, a plurality of ceramic green sheets are laminated. Thereby, the raw material of the laminated body 12 is obtained.

Next, the raw laminate is fired. In this firing step, the oxide constituting the intermediate layer 4 is not reduced in order to ensure that the bondability between the core material 2 and the outer layer 3 in the particles 1 constituting the metal powder is maintained. The Therefore, as will become clear from the experimental examples described later, the logarithmic difference between the oxygen partial pressure PO ₂ in the firing atmosphere and the equilibrium oxygen partial pressure PO _{20 in the} core material: log (PO ₂ / PO ₂₀ ) is 0 to 7. It is preferably selected within the range of 5.

  The laminated body 12 shown in FIG. 2 is obtained by the above baking. Next, the external electrodes 18 and 19 are formed on the end faces 16 and 17 of the multilayer body 12 by, for example, baking a conductive paste, and plated as necessary, whereby the multilayer ceramic capacitor 11 is completed.

  In the manufacturing method of the multilayer ceramic capacitor 11 as described above, peeling of the outer layer 3 of the particles 1 is suppressed until the metal powder contained in the conductive paste to be the internal electrodes 14 and 15 reaches the high temperature region in the firing process. Therefore, the heat shrinkage suppression effect by the oxide constituting the outer layer 3 is maintained. Therefore, in the multilayer ceramic capacitor 11, delamination during firing is suppressed. In addition, in order to enhance the heat shrinkage suppressing effect and maintain it more reliably, it is not necessary to form the outer layer 3 so thickly, so that even if the thickness of the internal electrode is reduced to 0.5 μm or less, for example, Reduction in rate is suppressed.

  The multilayer ceramic electronic component that is advantageously manufactured using the metal powder according to the present invention may be other than the multilayer ceramic capacitor 1 described above.

[Experimental example]
Below, the experiment example implemented in order to confirm the effect by this invention is demonstrated. In this experimental example, a conductive paste was produced using metal powder, and a multilayer ceramic capacitor was produced using this conductive paste.

1. Production of metal powder As a core material, a metal powder having a particle size shown in the column of “core material particle size” in Tables 1 and 2 below and made of a metal shown in the column of “core material element” Prepared. Here, the “core particle diameter” is an average value of the particle diameters extracted from an FE-SEM photograph (20 k times) using analysis software for extracting circular particles. The “core material element” is obtained by measurement by IPC-AES.

  Next, the said core material was heat-processed in air at 200 degreeC, and the oxide film was formed in each particle | grain surface which comprises metal powder. Here, in samples 1 to 15 and 26 to 42 in which the same element as the element displayed in the “core material element” column is displayed in the “intermediate layer-containing element” column of Tables 1 and 2, The above-mentioned oxide film itself gave an oxide constituting the intermediate layer, and the heat treatment time was controlled to obtain the thicknesses shown in the column “intermediate layer thickness” in Tables 1 and 2. For reference, the heat treatment time was 2 hours when the “intermediate layer thickness” was 10 nm.

  On the other hand, in addition to the elements displayed in the “core material element” column, for example, “Ni, Ti” in the “intermediate layer-containing element” column of Tables 1 and 2, enter other elements than the element concerned. Samples 16 to 25 were processed as follows.

  As a representative example, the sample 20 in which the “intermediate layer-containing element” is “Ni, Cr” will be described. In the sample 20, the metal nickel powder having the oxide film (NiO) formed therein is dispersed in isopropyl alcohol. After adding and stirring the chromium alkoxide, pure water was added to obtain a state in which the core material nickel was the main component and the chromium-containing intermediate layer adhered to the core material surface.

  The other samples 16 to 19 and 21 to 25 were subjected to the same treatment using the corresponding metal alkoxide.

  The “intermediate layer thickness” in Tables 1 and 2 was determined as the length measured from the core material surface to the inner side of the outer layer described later by FE-TEM mapping. The “intermediate layer-containing element” was measured by FE-TEM mapping.

Next, an outer layer was formed. “BT” in the column of “Outer layer-containing element” in Tables 1 and 2 indicates that Ba and Ti constituting BaTiO ₃ are contained. For Samples 1 to 25 and 30 to 43 whose “outer layer-containing element” is “BT”, in order to form the outer layer, the metal powder having the intermediate layer formed therein was dispersed in isopropyl alcohol as described above. Titanium alkoxide is added, heated to 60 ° C., barium hydroxide is added thereto, and reacted with titanium oxide to attach BaTiO ₃ as an oxide constituting the outer layer to the surface of the intermediate layer. The slurry was dried. In this way, a metal powder comprising particles in which an outer layer made of BaTiO ₃ formed by the sol-gel method was formed on the intermediate layer was obtained.

In addition, among the samples 1 to 25 and 30 to 43, in addition to the elements displayed in the “core element” column of Tables 1 and 2, elements other than the element are also included in the “intermediate layer-containing element” column. For the filled samples 16 to 25, after finishing the formation of the intermediate layer, the above-described titanium alkoxide was added to the metal alkoxide solution containing the additive element to the intermediate layer, and thereafter, similarly to 60 ° C. After heating, barium hydroxide was added thereto and reacted with titanium oxide to obtain a metal powder comprising particles in which an outer layer made of BaTiO ₃ was formed on the intermediate layer.

  On the other hand, for samples 26 to 29 whose “outer layer-containing element” is not only “BT”, as in the case of samples 1 to 25 and 30 to 43 described above, using the corresponding metal alkoxide, A metal powder comprising particles obtained by forming an outer layer made of an oxide containing a metal element shown in the column of “Outer layer-containing element” on the intermediate layer by the Lugel method was obtained.

  “Intermediate layer / outer layer coverage” in Table 1 and Table 2 is a circle in which an oxide layer (intermediate layer and / or outer layer) covering the periphery of the particle cross section is covered with FE-TEM. The circumference is obtained, and the ratio with the circumference of the core material is calculated and obtained. In Sample 43, the “intermediate layer / outer layer coverage” was 0%, indicating that no intermediate layer was formed.

  The “outer layer-containing element” was measured by FE-TEM mapping.

  The “outer layer thickness” is obtained by measuring the inner and outer lengths of the outer layer by FE-TEM mapping.

  The “outer layer structure” is identified from the oxide constituting the outer layer.

2. Preparation of conductive paste Next, using the metal powder obtained as described above, a conductive paste was prepared as follows.

  Ethyl cellulose binder: organic vehicle prepared by dissolving 10% by weight in terpineol: 90% by weight: 40% by weight, terpineol: 10% by weight, and the above metal powder: 50% by weight are carefully dispersed by a three-roll mill. By conducting the mixing treatment, a conductive paste having a good dispersion state was obtained.

3. Production of Multilayer Ceramic Capacitor A powder of a barium titanate ceramic composition was prepared, and an organic solvent such as a polyvinyl butyral binder and ethanol was added thereto and wet mixed by a ball mill to obtain a ceramic slurry.

  Next, a ceramic green sheet having a thickness of 5 μm was formed by applying a doctor blade method to the ceramic slurry.

  Next, the conductive paste was screen-printed on the ceramic green sheet to form a conductive paste film serving as an internal electrode. The thickness of the conductive paste was set to 0.8 μm after firing.

  Next, a ceramic green sheet on which a conductive paste film serving as an internal electrode was formed was laminated and pressed to obtain a raw laminate block having 300 internal electrodes. Next, this block was cut into a predetermined size to obtain a laminate chip.

Next, the laminate chip was subjected to a deorganic component treatment and a decarbonization treatment, and then a firing step was performed while the temperature was increased at a temperature increase rate of 10 ° C./min or more. In this firing step, the logarithmic difference: log (PO ₂ / PO ₂₀ ) between the oxygen partial pressure PO ₂ in the firing atmosphere and the equilibrium oxygen partial pressure PO ₂₀ of the core material of each particle of the aforementioned metal powder is shown in Table 1 and Control was performed as shown in the column of “log (PO ₂ / PO ₂₀ )” in Table 2.

  External electrodes were formed on the fired multilayer chip thus obtained, and a multilayer ceramic capacitor as a sample was obtained.

  With respect to the obtained multilayer ceramic capacitor, as shown in Table 1 and Table 2, the “short rate”, “structural defect occurrence rate”, and “electrode coverage rate” were determined. The “short rate”, “structural defect occurrence rate”, and “electrode coverage” shown in Tables 1 and 2 are displayed based on the criteria shown in Table 3.

  Regarding the “short ratio”, the one whose capacitance is less than two digits from the design value is determined as a short, and the ratio of the number of samples determined to be short in each of the 100 samples is obtained. The results are shown in Table 1 and Table 2 according to the criteria shown in the “Short Rate” column of Table 3.

  Regarding the “structural defect occurrence rate”, the ratio of the number of samples in which structural defects occurred in the internal electrode layer or in the vicinity of the internal electrode in 100 samples was obtained. Table 1 and Table 2 show the results according to the criteria shown in the column.

  Regarding the “electrode coverage”, for each sample 100, the photograph obtained by photographing the sample with the internal electrode layer peeled off with a metal microscope was binarized to calculate the occupancy of the electrode part, and this occupancy was The results are shown in Tables 1 and 2 in accordance with the criteria shown in the “electrode coverage” column of Table 3.

  In Table 1, Sample 12 is outside the scope of the present invention in that the “intermediate layer thickness” is 0.1 nm, which is less than 0.2 nm.

  In Table 2, sample 43 is outside the scope of the present invention in that the “intermediate layer thickness” is 0 and no intermediate layer is provided.

  Hereinafter, each sample will be considered with reference to Tables 1 to 3.

<Samples 1-5>
In Samples 1 to 5, the “core particle size” is changed in the range of 1 to 1200 nm. In any of Samples 1 to 5, good results are obtained as compared with Samples 12 and 43 outside the scope of the present invention. In particular, in Samples 2 to 4 in which the “core particle size” is in the range of 5 to 1000 nm, compared to Samples 1 and 5 that are out of the range of 5 to 1000 nm, “Short rate”, “Structural defect occurrence rate” and Excellent results are shown in all aspects of “electrode coverage”.

<Samples 6-8>
In Samples 6 to 8, the “core material element” is different from Ni in other samples. From these samples 6 to 8, it can be seen that the same effect can be obtained even with Cu, Ag and Pd other than Ni.

<Samples 9 to 11>
In Samples 9 to 11, the “intermediate layer / outer layer coverage” is changed. Samples 9 to 11 have better results than samples 12 and 43 outside the scope of the present invention. In particular, according to Samples 10 and 11 having “intermediate layer / outer layer coverage” of 30% or more, “short rate”, “structural defect occurrence rate”, and “electrode coverage” compared to Sample 9 with 20%. In all of the points, excellent results are shown. From this, it can be seen that the sintering suppressing effect by the intermediate layer and the outer layer is more remarkably exhibited.

<Samples 12 to 15>
In Samples 12 to 15, the “intermediate layer thickness” is changed in the range of 0.1 to 70 nm. The intermediate layer contributes to improving the bondability between the outer layer and the core material. Since the bondability is due to the wettability between the intermediate layer and each of the outer layer and the core material, the bondability is expressed by the exchange of atoms at the interface. In each of Samples 12 to 15, good results were obtained as compared with Sample 43 in which the “interlayer thickness” outside the scope of the present invention was zero.

  In particular, Samples 13 to 15 whose “intermediate layer thickness” is 0.2 nm to 70 nm are more short-circuited and “electrode coverage” than Sample 12 that is 0.1 nm less than 0.2 nm. Shows excellent results.

  Further, among the samples 13 to 15, the samples 13 and 14 in which the “intermediate layer thickness” is 50 μm or less are compared with the sample 15 of 70 nm in the “short rate”, “structural defect occurrence rate”, and “electrode coating”. Excellent results are shown in all points of "rate".

  As in Samples 13 to 15, by setting the “intermediate layer thickness” to 0.2 nm or more, it becomes easy to maintain the balance of exchange of atoms at the interface, so that it is easy to obtain the effect of further improving the bondability. It is guessed. In addition, as in Samples 13 and 14, by setting the “intermediate layer thickness” to 50 μm or less, the ratio of the metal of the core material can be sufficiently maintained in the entire internal electrode, and the electrode coverage after firing is improved. It is assumed that it can be made.

<Samples 16 to 25>
In Samples 16 to 25, as the “intermediate layer-containing element”, in addition to Ni, a metal element other than Ni is also contained. Even if Ti, Zr, V, Ta, Cr, W, Mn, Fe, Co, or Cu is contained as an “intermediate layer-containing element” from Samples 16 to 25, “short ratio”, “structure” It can be seen that excellent results are shown in all the points of “defect occurrence rate” and “electrode coverage rate”.

  Although not necessarily recognized from the results shown in Table 1, when a metal such as Ti, Zr, V, Ta, Cr, W, Mn, Fe, Co or Cu is added, the metal of the core material It has been confirmed that a composite oxide is formed with a certain Ni, and the wettability with the core material is further improved.

<Samples 26 to 29>
Samples 26 to 29 contain Zr, Si, Dy, or Y in addition to BT as the “outer layer-containing element”. These elements act to match the sintering timing in relation to the composition of the dielectric ceramic constituting the ceramic layer provided in the multilayer ceramic capacitor. Samples 26 to 29 containing Zr, Si, Dy or Y also show excellent results in all the points of “short rate”, “structural defect occurrence rate” and “electrode coverage”.

<Samples 30 to 33>
In Samples 30 to 33, the “outer layer thickness” is changed in the range of 0.1 to 70 nm. Among the samples 30 to 33, in particular, in the samples 31 and 32 where the “outer layer thickness” is in the range of 0.2 to 50 nm, all of the “short rate”, “structural defect occurrence rate”, and “electrode coverage rate” are Excellent results are shown. The effect of suppressing the sintering by the outer layer can be further increased by setting the “outer layer thickness” to 0.2 nm or more. On the other hand, by setting the “outer layer thickness” to 50 nm or less, This is because the ratio of the metal can be made higher.

<Samples 34 to 39>
In samples 34 to 39, the effect when the “outer layer structure” is other than perovskite has been confirmed. All of the oxides employed in the “outer layer structure” of Samples 34 to 39 are known to have high heat resistance. In any of the samples 34 to 39, excellent results were shown for all of the “short rate”, “structural defect occurrence rate”, and “electrode coverage rate”.

<Samples 40 to 42>
In samples 40 to 42, “log (PO ₂ / PO ₂₀ )” which is a logarithmic difference between the oxygen partial pressure PO ₂ in the firing atmosphere and the equilibrium oxygen partial pressure PO _{20 in the} core material is changed. In the samples 40 and 41 in which “log (PO ₂ / PO ₂₀ )” is in the range of 0 to 7.5, excellent results were obtained for all of the “short rate”, “structural defect occurrence rate”, and “electrode coverage rate”. Is shown. On the other hand, in the sample 42 in which “log (PO ₂ / PO ₂₀ )” is 8 exceeding 7.5, “short rate”, “structural defect occurrence rate”, and “electrode coverage rate” are compared with the samples 40 and 41. Tend to be inferior. The reason why the “electrode coverage” tends to be inferior is that when “log (PO ₂ / PO ₂₀ )” exceeds 7.5, the oxidation proceeds more. This is presumably because the amount of the metal element in the core material decreases.

1 Particle 2 Core Material 3 Outer Layer 4 Intermediate Layer T1 Intermediate Layer Thickness T2 Outer Layer Thickness D Core Material Particle Size 11 Multilayer Ceramic Capacitor 12 Laminate 13 Ceramic Layers 14 and 15 Internal Electrode

Claims (11)

A metal powder comprising a plurality of particles having a core material mainly composed of a metal and an outer layer made of an oxide disposed so as to cover at least a part of the outer surface of the core material,
Along the interface between the core material and the outer layer, the oxide is different from the oxide constituting the outer layer, and includes an oxide other than the metal hydroxide which is the main component of the core material. Metal powder in which the intermediate layer is formed with a thickness of 0.2 nm or more.   The metal powder according to claim 1, wherein the metal that is a main component of the core material is at least one selected from Ni, Cu, Ag, and Pd.   The metal that is the main component of the core material is Ni, and the intermediate layer is Ti, Zr, V, Ta, Cr, W, in addition to NiO as an oxide of the metal that is the main component of the core material. The metal powder according to claim 2, comprising an oxide of at least one metal selected from Mn, Fe, Co, and Cu.   The metal powder according to any one of claims 1 to 3, wherein at least one of the intermediate layer and the outer layer covers an area of 30 to 100% of a surface of the core material.   The metal powder according to claim 1, wherein the outer layer has a thickness of 0.2 to 50 nm.   The metal powder according to claim 1, wherein the intermediate layer has a thickness of 50 nm or less.   The metal powder according to claim 1, wherein the core material has a particle diameter of 5 to 1000 nm. A core material mainly composed of a metal, and an outer layer made of an oxide disposed so as to cover at least a part of the outer surface of the core material, and along an interface between the core material and the outer layer In this method, an intermediate layer containing an oxide of the metal that is an oxide different from the oxide constituting the outer layer and that is a main component of the core material is formed. And
Preparing the core material;
An intermediate layer forming step of forming the intermediate layer including an oxide formed by oxidizing the surface of the core material with a thickness of 0.2 nm or more by heat-treating the core material in an oxygen-containing atmosphere;
An outer layer forming step of forming the outer layer by applying an oxide constituting the outer layer to the core member on which the intermediate layer is formed.   A conductive paste comprising the metal powder according to claim 1 dispersed in an organic vehicle. Preparing a raw laminate comprising a plurality of laminated ceramic green sheets and an internal electrode formed between the ceramic green sheets using the conductive paste according to claim 11;
A method for producing a multilayer ceramic electronic component, comprising: firing the raw multilayer body. In the firing step, the logarithmic difference between the oxygen partial pressure PO ₂ in the firing atmosphere and the equilibrium oxygen partial pressure PO _{20 in the} core material: log (PO ₂ / PO ₂₀ ) is selected in the range of 0 to 7.5. A method for manufacturing a multilayer ceramic electronic component according to claim 10.

Images