Multilayer ceramic capacitor

Abstract

The present invention provides a multilayer ceramic capacitor comprising an internal electrode that is capable of maintaining relatively high coverage, even when formed into a thin layer.　A multilayer ceramic capacitor (1) is provided with a multilayer body (2) which has a plurality of stacked dielectric layers (3) that are formed of a ceramic, and a plurality of internal electrodes (4, 5) that are respectively arranged along a plurality of interfaces between the dielectric layers (3), wherein the internal electrodes (4, 5) contain silver as a conductive component and also contain at least one selected from among AgTiO3, EuTiO3, and NaTiO3.

Description

Technical Field

[0001] This invention relates to a multilayer ceramic capacitor, and particularly to the composition of internal electrodes provided in the multilayer ceramic capacitor.

Background Art

[0002] A multilayer ceramic capacitor generally includes a laminate having a plurality of stacked dielectric layers made of ceramic and a plurality of internal electrodes respectively disposed along a plurality of interfaces between the dielectric layers, and a plurality of external electrodes provided on the outer surface of the laminate and electrically connected to the internal electrodes. The internal electrodes include a plurality of first internal electrodes and a plurality of second internal electrodes alternately arranged in the stacking direction of the laminate, and the external electrodes include a first external electrode electrically connected to the first internal electrode and a second external electrode electrically connected to the second internal electrode.

[0003] In order to make such a multilayer ceramic capacitor smaller and have a larger capacitance, it is required to make the dielectric layer and the internal electrodes thinner and to increase the coverage (electrode continuity) of the internal electrodes. Generally, in the firing process during the manufacture of a multilayer ceramic capacitor, the temperature at which the conductive metal particles contained in the conductive paste film to be the internal electrode sinter is lower than the temperature at which the ceramic constituting the dielectric layer sinters, so the metal particles contained in the internal electrode sinter first. This causes a reduction in the coverage of the internal electrodes. In particular, for an internal electrode thinned to, for example, a thickness of 1 μm or less, the coverage is likely to decrease, and there is a problem that an increase in capacitance is likely to be inhibited due to such a decrease in coverage.

[0004] Therefore, in order to form a thinned internal electrode with a high coverage, in the firing process during the manufacture of a multilayer ceramic capacitor, it is necessary to raise the temperature at which the conductive metal particles contained in the conductive paste film to be the internal electrode are sintered. As a result, the temperature at which the metal particles contained in the conductive paste film to be the internal electrode are sintered can be brought close to the temperature at which the ceramic constituting the dielectric layer starts sintering, and the shrinkage timing during sintering can be made closer between the internal electrode and the dielectric layer. As a result, the coverage of the internal electrode becomes higher and a large capacitance can be realized.

[0005] In order to increase the coverage of the internal electrode and realize a large capacitance by the method described above, for example, as described in paragraph 0004 of Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2016-31807), it is known to add a ceramic material having a composition similar to the composition of the ceramic constituting the dielectric layer, that is, a co-material, to the conductive paste for forming the internal electrode. By adding the co-material, the sintering timing of the metal particles contained in the conductive paste film to be the internal electrode can be shifted to a higher temperature side, and the temperature at which the metal particles contained in the conductive paste film are sintered can be brought close to the temperature at which the ceramic constituting the dielectric layer is sintered.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, even if a co-material is added to the conductive paste for forming the internal electrodes, it cannot be denied that the temperature at which the metal particles contained in the conductive paste sinter is still lower than the temperature at which the ceramic constituting the dielectric layer sinters, and further improvement is desired. In particular, for an internal electrode thinned to, for example, a thickness of 1 μm or less, an effective solution to the problem of coverage reduction that inhibits an increase in capacitance is strongly demanded.

[0008] Therefore, the present invention has been made in view of such problems, and an object thereof is to provide a multilayer ceramic capacitor including internal electrodes that can maintain a relatively high coverage even when thinned.

Means for Solving the Problems

[0009] The multilayer ceramic capacitor according to the present invention includes a laminate including a plurality of stacked dielectric layers made of ceramic and a plurality of internal electrodes respectively disposed along a plurality of interfaces between the dielectric layers.

[0010] In order to solve the above-described technical problems, in the present invention, the internal electrodes are characterized by containing silver as a conductive component and at least one selected from AgTiO3, EuTiO3, and NaTiO3.

Effects of the Invention

[0011] According to the present invention, at least one selected from AgTiO3, EuTiO3, and NaTiO3 contained in the internal electrodes contributes to increasing the coverage of the internal electrodes containing silver as a conductive component. Therefore, even when the internal electrodes are thinned, the coverage of the internal electrodes does not decrease, and an increase in the capacitance of the multilayer ceramic capacitor can be prevented from being inhibited.

Brief Description of the Drawings

[0012]

Figure 1

Best Mode for Carrying Out the Invention

[0013] Referring to FIG. 1, the structure of a multilayer ceramic capacitor 1 according to an embodiment of the present invention will be described.

[0014] The multilayer ceramic capacitor 1 includes a laminate 2. The laminate 2 includes a plurality of stacked dielectric layers 3 made of ceramic, and a plurality of internal electrodes 4 and 5 disposed along the interfaces between the plurality of dielectric layers 3. The internal electrodes 4 and 5 are classified into a plurality of first internal electrodes 4 and a plurality of second internal electrodes 5 that are alternately arranged in the stacking direction of the laminate 3. On the outer surfaces of the laminate 2, more specifically, on each of the opposing end faces, a first external electrode 6 and a second external electrode 7 are provided, respectively. The first external electrode 6 is electrically connected to the first internal electrode 4, and the second external electrode 7 is electrically connected to the second internal electrode 5.

[0015] The dielectric layer 3 is made of, for example, a ceramic having ABO3 (where A is at least one of Ba, Ca, and Sr, and B is at least one of Ti and Zr) as a main component. Further, the ceramic may have ABO3 as a main component and further contain at least one of Mn, Mg, Si, Y, Dy, and Gd as a sub-component.

[0016] The internal electrodes 4 and 5 contain silver as a conductive component. Further, as a characteristic composition, the internal electrodes 4 and 5 contain at least one selected from AgTiO3, EuTiO3, and NaTiO3. AgTiO3, EuTiO3, and NaTiO3 have an ilmenite crystal structure.

[0017] Note that, as can be seen from the experimental examples described later, in a preferred embodiment, the dielectric layer 3 is made of a ceramic mainly composed of at least one selected from BaTiO3, SrTiO3, and CaZrO3, and the internal electrodes 4 and 5 contain silver as a conductive component, and as a ceramic material, contain at least one selected from AgTiO3, EuTiO3, and NaTiO3, and further contain, if necessary, at least one selected from BaTiO3, SrTiO3, and CaZrO3 contained in the dielectric layer 3.

[0018] The external electrodes 6 and 7 are formed, for example, by applying a conductive paste having Ag or Cu as a main component of the conductive component to the end faces of the laminate 2 and baking it. If necessary, Ni plating and Sn plating thereon may be applied to the thick film formed by baking.

[0019] The multilayer ceramic capacitor 1 is manufactured, for example, through the following steps. First, a ceramic slurry containing raw material powder of ceramic having the above composition is prepared. Next, an appropriate sheet forming method is applied to the ceramic slurry to form a ceramic green sheet. Next, the conductive paste to be each of the internal electrodes 4 and 5 is applied by printing or the like on a predetermined ceramic green sheet among the plurality of ceramic green sheets. Next, after laminating a plurality of ceramic green sheets, they are pressure-bonded to obtain a raw laminate. Next, the raw laminate is fired. In this firing step, the ceramic green sheet becomes the dielectric layer 3. Thereafter, the external electrodes 6 and 7 are formed on the end faces of the laminate 3.

[0020] The conductive paste to be the internal electrodes 4 and 5 used in the manufacture of the above-described multilayer ceramic capacitor 1 is preferably prepared as follows.

[0021] In the production of the conductive paste, a first step of preparing a ceramic powder slurry containing a ceramic powder, an organic solvent, and a dispersant, a second step of preparing a metal powder slurry containing a conductive metal powder, an organic solvent, and a dispersant, a third step of preparing an organic vehicle containing an organic resin component and an organic solvent, and a fourth step of mixing the ceramic powder slurry, the metal powder slurry, and the organic vehicle are carried out.

[0022] More specifically, in the first step, a ceramic powder slurry is produced by mixing a ceramic powder and a dispersant into an organic solvent.

[0023] As the above-mentioned ceramic powder, for example, those composed of at least one selected from AgTiO3, EuTiO3, and NaTiO3 as ABO3 oxides are used. Further, in addition to this, those composed of at least one selected from BaTiO3, SrTiO3, and CaZrO3 as co-materials may be used.

[0024] Since the conductive metal powder contained in the metal powder slurry produced in the second step described later contains silver, AgTiO3, EuTiO3, and NaTiO3 as the above-mentioned ABO3 oxides are ABO3-type oxides with a specific ionic radius in which the ratio of the ionic radius of the element at the A site in ABO3 to the ionic radius of silver in the 6-fold coordination is 0.89 or more and 1.02 or less.

[0025] According to a ceramic powder composed of at least one selected from AgTiO3, EuTiO3, and NaTiO3 as ABO3 oxides, the reaction that may occur between the ceramic powder and the silver powder contained in the metal powder slurry produced in the second step during firing can be suppressed. The ceramic powder has the ABO3 oxide as the main component, and may further contain at least one of Mn, Mg, Si, Y, Dy, and Gd as a sub-component. When containing such a sub-component, the grain growth of the ceramic particles may be suppressed, and the sintering of the metal particles can be effectively suppressed.

[0026] As the dispersant mixed with the ceramic powder in the first step, for example, an anionic polymer dispersant can be used. As the organic solvent, for example, dihydroterpineol can be used.

[0027] In the second step, a metal powder slurry is produced by mixing a conductive metal powder and a dispersant in an organic solvent. As the conductive metal powder, a powder made of silver is used. As the dispersant and the organic solvent used in the second step, those similar to those used in the first step can be used.

[0028] In the third step, an organic vehicle is produced by mixing an organic resin component in an organic solvent. As the organic resin component, for example, ethyl cellulose resin can be used. For the organic solvent used in the third step, those similar to those used in the first step can be used.

[0029] In the fourth step, the above-mentioned ceramic powder slurry, metal powder slurry and organic vehicle are mixed. Thereby, a conductive paste to be the internal electrodes 4 and 5 is obtained. This conductive paste contains a ceramic powder slurry, and the ceramic powder slurry contains a ceramic powder composed of at least one selected from AgTiO3, EuTiO3 and NaTiO3 as an ABO3 oxide having a specific ionic radius as described above. Therefore, the internal electrodes 4 and 5 provided in the multilayer ceramic capacitor 1 manufactured through the firing process will contain at least one selected from AgTiO3, EuTiO3 and NaTiO3.

[0030] [Experimental Example] Next, the experimental examples carried out to confirm the effects of this invention will be described.

[0031] In this experimental example, silver powder was prepared as the conductive metal powder contained in the conductive paste for forming the internal electrodes.

[0032] In addition to AgTiO3, EuTiO3, and NaTiO3, CuTiO3, SrTiO3, BaTiO3, and CaZrO3 were prepared as ABO3 oxides with a specific ionic radius that constitutes the ceramic powder contained in the conductive paste for forming internal electrodes. Table 1 shows "crystal structure", "coordination number", "A-site element", and "ionic radius" for these ABO3 oxides. Note that Sr, Ba, and Ca have a 12-fold coordination in the original perovskite structure, but for Sr, Ba, and Ca as well, when they dissolve into the sites of the 6-fold coordinated elements (Ag, Eu, Na) in the ilmenite structure, they have a 6-fold coordination. Therefore, the "ionic radius" in Table 1 indicates the value in the 6-fold coordination.

[0033]

Table 1

[0034] Hereinafter, Experimental Example 1, Experimental Example 2, and Experimental Example 3, which were carried out by changing the ceramic raw material constituting the dielectric layer, will be described.

[0035] (Experimental Example 1) Main component of the ceramic constituting the dielectric layer: BaTiO3 1. Preparation of BaTiO3-based ceramic raw material for forming the dielectric layer As starting materials, powders of BaCO3 and TiO2 as the main components were weighed and mixed by a ball mill for 72 hours, and then heat-treated at a top temperature of 1000 °C for 2 hours to obtain heat-treated powder. On the other hand, as sub-components, powders of MnO, Dy2O3, MgO, SiO2, and BaCO3 were prepared. For the above heat-treated powder, the sub-component powders were weighed so that the composition ratio was 100BaTiO3 + 0.5Mn + 1.0Dy + 1.0Mg + 1.0Si + 2.0Ba. These sub-component powders were added to the above heat-treated powder and mixed by a ball mill for 24 hours, and then dried to obtain BaTiO3-based ceramic raw material powder.

[0036] 2. Preparation of conductive paste for forming internal electrodes The powder of "ABO3 oxide" shown in Table 2 below and the BaTiO3-based ceramic raw material powder for the above dielectric layer were used as the ceramic powders contained in the conductive paste for forming the internal electrodes.

[0037] These powders of "ABO3 oxide" and the BaTiO3-based ceramic raw material powder were weighed so as to have the "addition ratio" shown in Table 2, and these powders, dihydroterpineol as an organic solvent, and an anionic polymer dispersant as a dispersant were preliminarily mixed in a mediumless stirring mill and then dispersed in a medium stirring mill to prepare a ceramic powder slurry (first step).

[0038] On the other hand, silver powder as a conductive metal powder, dihydroterpineol as an organic solvent, and an anionic polymer dispersant as a dispersant were dispersed in a three-roll mill to prepare a metal powder slurry (second step).

[0039] Furthermore, ethyl cellulose resin as an organic resin component and dihydroterpineol as an organic solvent were mixed to obtain an organic vehicle (third step).

[0040] Thereafter, the above metal powder slurry and the above ceramic powder slurry were added to the above organic vehicle and mixed and dispersed to prepare a conductive paste for forming internal electrodes (fourth step).

[0041] Table 2 shows the ratio of the ionic radius of the A-site element in the 6-fold coordination to the ionic radius of silver in the 6-fold coordination contained in the internal electrode, that is, "ionic radius ratio (A-site element / silver metal)". For sample 8, the ratio of the ionic radius of the Ba element (1.35 Å) shown in Table 1 in the 6-fold coordination to the ionic radius of silver in the 6-fold coordination (1.15 Å) is shown.

[0042] 3. Fabrication of Multilayer Ceramic Capacitor A ceramic slurry containing the BaTiO3-based ceramic raw material powder prepared in 1 above was prepared, and then the doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Next, the conductive paste for forming an internal electrode prepared in 2 above was applied by screen printing onto a predetermined ceramic green sheet among the plurality of ceramic green sheets. Next, after laminating a plurality of ceramic green sheets, they were pressure-bonded to obtain a green laminate. Next, the green laminate was fired. Thereafter, an external electrode was formed on the end face of the sintered laminate to fabricate a laminated ceramic capacitor as a sample.

[0043] 4. Evaluation

[0044]

Table 2

[0045] The internal electrode and the dielectric layer located at the central portion in the height direction of the laminate provided in the laminated ceramic capacitor as a sample were peeled off from each other by dielectric breakdown.

[0046] Next, the vicinity of the central portion (the position that is 1 / 2 in the width direction and 1 / 2 in the length direction) of the exposed internal electrode was observed at a magnification of 100 times using a microscope. Then, by analyzing the obtained image, the ratio of the area occupied by the conductor film as the internal electrode in the exposed portion was determined as "coverage" shown in Table 2. Those with a "coverage" of 80% or more were judged as good, and an "○" was entered in the "Evaluation" column, while those with a "coverage" lower than 80% were judged as defective, and an "×" was entered in the "Evaluation" column.

[0047] 5. Discussion For Samples 1 to 3 and 5 to 7 in Table 2, the "Evaluation" is "○". In these Samples 1 to 3 and 5 to 7, the internal electrode contains any one of AgTiO3, EuTiO3, and NaTiO3 as the ABO3 oxide. Also, the internal electrode contains silver as a conductive component.

[0048] Here, regarding the ionic radius, first, as shown in the "AgTiO3" item in Table 1, the ionic radius of silver in 6 coordination is 1.15 Å. On the other hand, the ionic radii of the elements at the A site of each of AgTiO3, EuTiO3, and NaTiO3 as the ABO3 oxides contained in the internal electrodes in Samples 1 to 3 and 5 to 7 are 1.15 Å, 1.17 Å, and 1.02 Å, respectively, as shown in Table 1.

[0049] In Samples 1 to 3 and 5 to 7 evaluated as "○", the ratio of the ionic radius of the element at the A site in ABO3 to the ionic radius of the metal element contained in the conductive metal particles in 6 coordination, that is, the "ionic radius ratio", is 0.89 or more and 1.02 or less.

[0050] Thus, AgTiO3, EuTiO3, and NaTiO3 as the ABO3 oxides in Samples 1 to 3 and 5 to 7 have an ionic radius of the element at the A site in ABO3 equal to or close to the ionic radius of silver in 6 coordination as the conductive metal to be contained in the internal electrode. Therefore, the energy difference from silver in the internal electrode becomes 0 or small, and they remain without being ejected from the internal electrode portion, acting to improve the heat resistance of the internal electrode. As a result, it is presumed that the coverage in Samples 1 to 3 and 5 to 7 became as high as 82% or more.

[0051] Also, like Samples 5 to 7, the addition ratios of AgTiO3, EuTiO3, and NaTiO3 are not necessarily 100%, but if they are 10% or more, an effect of improving the coverage was recognized compared to the case where none of AgTiO3, EuTiO3, and NaTiO3 are contained.

[0052] In contrast, for sample 4 evaluated as "×", SrTiO3 was used as the ABO3 oxide. The ionic radius of Sr in the 6 - coordination of the A - site in ABO3 is 1.18 Å as shown in Table 1. Therefore, the ratio of the ionic radius of Sr in the 6 - coordination to the ionic radius of silver in the 6 - coordination, that is, the "ionic radius ratio" is 1.03. That is, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less, and the coverage is as low as 76%.

[0053] Also, in sample 8, which was also evaluated as "×", only BaTiO3 as a co - material was added to the internal electrode. In this case, Ba, which is the element of the A - site in ABO3 with a perovskite structure, has a 12 - coordination, but when it is dissolved in the A - site of the ilmenite structure, it is necessary to compare with the ionic radius in the 6 - coordination, which is the coordination number of the A - site of the ilmenite structure. The ionic radius of Ba in the 6 - coordination is 1.35 Å as shown in Table 1. Therefore, the ratio of the ionic radius of Ba in the 6 - coordination to the ionic radius of silver in the 6 - coordination, that is, the "ionic radius ratio" is 1.17. Thus, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less, and the coverage is as low as 75%.

[0054] In these samples 4 and 8, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less. It is presumed that BaTiO3 is ejected from the internal electrode part, the heat resistance of the internal electrode is not improved, and the coverage becomes low.

[0055] (Experimental Example 2) Main component of the ceramic constituting the dielectric layer: CaZrO3 1. Preparation of CaZrO3 - based ceramic raw material for forming the dielectric layer As starting materials, powders of CaCO3 and ZrO2 as main components, and powders of MnO, SiO2 and MgO as sub - components were weighed, mixed by a ball mill for 72 hours, and then heat - treated at a top temperature of 1000 °C for 2 hours to obtain CaZrO3 - based ceramic raw material powder.

[0056] 2. Preparation of conductive paste for forming the internal electrode The powder of "ABO3 oxide" shown in Table 3 below and the CaZrO3-based ceramic raw material powder for the dielectric layer were used as the ceramic powders contained in the conductive paste for forming the internal electrodes.

[0057] These powders of "ABO3 oxide" and the CaZrO3-based ceramic raw material powder were weighed so as to have the "addition ratio" shown in Table 3, and a conductive paste for forming internal electrodes was prepared through the same process as in the case of Experimental Example 1 above.

[0058] Table 3 shows the "ionic radius ratio (A-site element / silver metal)" as in the case of Table 2. For Sample 18, the ratio of the ionic radius of Ca element (1.00 Å) shown in Table 1 in the 6-fold coordination to the ionic radius of silver (1.15 Å) in the 6-fold coordination is shown.

[0059] 3. Fabrication of Multilayer Ceramic Capacitor A ceramic slurry containing the CaZrO3-based ceramic raw material powder prepared in 1 above was prepared, and then the doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Thereafter, a multilayer ceramic capacitor as a sample was fabricated through the same process as in the case of Experimental Example 1.

[0060] 4. Evaluation

[0061]

Table 3

[0062] Following the same procedure as in the case of Experimental Example 1, as shown in Table 3, "coverage" was determined and evaluated in the same manner.

[0063] 5. Discussion For Samples 11 to 13 and 15 to 17 in Table 3, the "evaluation" is "○". In these Samples 11 to 13 and 15 to 17, the internal electrodes contain any one of AgTiO3, EuTiO3, and NaTiO3 as the ABO3 oxide. Further, the internal electrodes contain silver as a conductive component.

[0064] Here, regarding the ionic radius, first, as shown in the "AgTiO3" item in Table 1, the ionic radius of silver in 6 coordination is 1.15 Å. On the other hand, the ionic radii of the elements at the A site of each of AgTiO3, EuTiO3, and NaTiO3, which are ABO3 oxides contained in the internal electrodes in Samples 11 to 13 and 15 to 17, are 1.15 Å, 1.17 Å, and 1.02 Å, respectively, as shown in Table 1.

[0065] In Samples 11 to 13 and 15 to 17 evaluated as "○", the ratio of the ionic radius of the element at the A site in ABO3 to the ionic radius of the metal element contained in the conductive metal particles in 6 coordination, that is, the "ionic radius ratio", is 0.89 or more and 1.02 or less.

[0066] Thus, AgTiO3, EuTiO3, and NaTiO3 as ABO3 oxides in Samples 11 to 13 and 15 to 17 have an ionic radius of the element at the A site in ABO3 equal to or close to the ionic radius of silver in 6 coordination as the conductive metal to be contained in the internal electrode. Therefore, the energy difference from silver in the internal electrode becomes 0 or small, so they remain without being ejected from the internal electrode part and act to improve the heat resistance of the internal electrode. As a result, it is presumed that in Samples 11 to 13 and 15 to 17, the coverage became as high as 81% or more.

[0067] Also, like Samples 15 to 17, the addition ratios of AgTiO3, EuTiO3, and NaTiO3 are not necessarily 100%, but if they are 10% or more, an effect of improving the coverage was recognized compared to the case where none of AgTiO3, EuTiO3, and NaTiO3 are contained.

[0068] In contrast, for Sample 14 evaluated as "×", CuTiO3 was used as the ABO3 oxide. As shown in Table 1, the ionic radius of Cu, which is the element at the A site in ABO3, in 6 - coordination is 0.73 Å. Therefore, the ratio of the ionic radius of Cu in 6 - coordination to the ionic radius of silver in 6 - coordination, that is, the "ionic radius ratio", is 0.63. That is, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less, and the coverage is as low as 75%.

[0069] Also, in Sample 18, which was also evaluated as "×", only CaZrO3 as a co - material was added to the internal electrode. In this case, Ca, which is the element at the A site in ABO3 with a perovskite structure, has a 12 - coordination, but when it solid - solves into the A site of the ilmenite structure, it is necessary to compare with the ionic radius in 6 - coordination, which is the coordination number of the A site of the ilmenite structure. As shown in Table 1, the ionic radius of Ca in 6 - coordination is 1.00 Å. Therefore, the ratio of the ionic radius of Ca in 6 - coordination to the ionic radius of silver in 6 - coordination, that is, the "ionic radius ratio", is 0.87. Thus, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less, and the coverage is as low as 72%.

[0070] In these Samples 14 and 18, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less. It is presumed that CaZrO3 was ejected from the internal electrode part, the heat resistance of the internal electrode was not improved, and the coverage became low.

[0071] (Experimental Example 3) Main component of the ceramic constituting the dielectric layer: SrTiO3 1. Preparation of SrTiO3 - based ceramic raw materials for forming the dielectric layer As starting materials, powders of SrCO3 and TiO2 as main components, and powders of MnO, SiO2, and MgO as sub - components were weighed, mixed by a ball mill for 72 hours, and then heat - treated at a top temperature of 1000 °C for 2 hours to obtain SrTiO3 - based ceramic raw material powder.

[0072] 2. Preparation of conductive paste for forming the internal electrode The powder of "ABO3 oxide" shown in Table 4 below and the SrTiO3-based ceramic raw material powder for the dielectric layer were used as the ceramic powders contained in the conductive paste for forming the internal electrodes.

[0073] These powders of "ABO3 oxide" and the SrTiO3-based ceramic raw material powder were weighed so as to have the "addition ratio" shown in Table 4, and a conductive paste for forming internal electrodes was prepared through the same process as in the case of Experimental Example 1 above.

[0074] Table 4 shows the "ionic radius ratio (A-site element / silver metal)" as in the case of Table 2. For Sample 28, the ratio of the ionic radius of Sr element (1.18 Å) shown in Table 1 in the 6-fold coordination to the ionic radius of silver (1.15 Å) in the 6-fold coordination is shown.

[0075] 3. Fabrication of Multilayer Ceramic Capacitor A ceramic slurry containing the SrTiO3-based ceramic raw material powder prepared in 1 above was prepared, and then a doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Thereafter, a multilayer ceramic capacitor as a sample was fabricated through the same process as in the case of Experimental Example 1.

[0076] 4. Evaluation

[0077]

Table 4

[0078] Following the same procedure as in the case of Experimental Example 1, "coverage" was determined as shown in Table 4 and evaluated in the same manner.

[0079] 5. Discussion For Samples 21 to 23 and 25 to 27 in Table 4, the "evaluation" is "○". In these Samples 21 to 23 and 25 to 27, the internal electrodes contain any one of AgTiO3, EuTiO3, and NaTiO3 as the ABO3 oxide. Further, the internal electrodes contain silver as a conductive component.

[0080] Here, regarding the ionic radius, first, as shown in the item of "AgTiO3" in Table 1, the ionic radius of silver in 6 - coordination is 1.15 Å. On the other hand, the ionic radii of the elements at the A - site of each of AgTiO3, EuTiO3, and NaTiO3, which are ABO3 oxides contained in the internal electrodes in Samples 21 - 23 and 25 - 27, in 6 - coordination are 1.15 Å, 1.17 Å, and 1.02 Å, respectively, as shown in Table 1.

[0081] In Samples 21 - 23 and 25 - 27 evaluated as "○", the ratio of the ionic radius of the element at the A - site in ABO3 to the ionic radius of the metal element contained in the conductive metal particles in 6 - coordination, that is, the "ionic radius ratio" is 0.89 or more and 1.02 or less.

[0082] Thus, AgTiO3, EuTiO3, and NaTiO3 as ABO3 oxides in Samples 21 - 23 and 25 - 27 have the ionic radius of the element at the A - site in ABO3 equal to or close to the ionic radius of silver in 6 - coordination as the conductive metal to be contained in the internal electrode. Therefore, the energy difference from silver in the internal electrode becomes 0 or small, so they remain without being ejected from the internal electrode part and act to improve the heat resistance of the internal electrode. As a result, it is presumed that in Samples 21 - 23 and 25 - 27, the coverage became as high as 80% or more.

[0083] Also, like Samples 25 - 27, the addition ratios of AgTiO3, EuTiO3, and NaTiO3 are not necessarily 100%, but if they are 10% or more, the effect of improving the coverage was recognized compared with the case where none of AgTiO3, EuTiO3, and NaTiO3 is contained.

[0084] In contrast, for sample 24 evaluated as "×", CuTiO3 is used as the ABO3 oxide. The ionic radius of Cu, which is the element at the A site in ABO3, in 6 - coordination is 0.73 Å as shown in Table 1. Therefore, the ratio of the ionic radius of Cu in 6 - coordination to the ionic radius of silver in 6 - coordination, that is, the "ionic radius ratio" is 0.63. That is, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less, and the coverage is as low as 72%.

[0085] Also, in sample 28, which was also evaluated as "×", only SrTiO3 as a co - material is added in the internal electrode. In this case, Sr, which is the element at the A site in the perovskite - structured ABO3, is 12 - coordinated, but when it solid - solves into the A site of the ilmenite structure, it is necessary to compare with the ionic radius in 6 - coordination, which is the coordination number of the A site of the ilmenite structure. The ionic radius of Sr in 6 - coordination is 1.18 Å as shown in Table 1. Therefore, the ratio of the ionic radius of Sr in 6 - coordination to the ionic radius of silver in 6 - coordination, that is, the "ionic radius ratio" is 1.03. Thus, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less, and the coverage is as low as 70%.

[0086] In these samples 24 and 28, the "ionic radius ratio" is outside the range of 0.89 or more and 1.02 or less. It is presumed that SrTiO3 is ejected from the internal electrode part, the heat resistance of the internal electrode is not improved, and the coverage becomes low.

[0087] Embodiments of this invention are as follows.

[0088] <1> A laminate comprising a plurality of laminated dielectric layers made of ceramic and a plurality of internal electrodes respectively arranged along a plurality of interfaces between the dielectric layers. The internal electrode contains silver as a conductive component and at least one selected from AgTiO3, EuTiO3, and NaTiO3. A multilayer ceramic capacitor.

[0089] <2> The internal electrode has a thickness of 1 μm or less, and the multilayer ceramic capacitor according to <1>.

[0090] <3> The internal electrode has a coverage of 80% or more, and the multilayer ceramic capacitor according to <1> or <2>.

[0091] <4> The dielectric layer is made of a ceramic containing at least one selected from BaTiO3, SrTiO3, and CaZrO3 as a main component, and the internal electrode further contains at least one selected from BaTiO3, SrTiO3, and CaZrO3 contained in the dielectric layer, and the multilayer ceramic capacitor according to any one of <1> to <3>.

Explanation of symbols

[0092] 1 Multilayer ceramic capacitor 2 Laminate 3 Dielectric layer 4, 5 Internal electrode 6, 7 External electrode

Claims

Claim 1 A laminate comprising a plurality of stacked dielectric layers made of ceramic and a plurality of internal electrodes respectively disposed along a plurality of interfaces between the dielectric layers, The internal electrode contains silver as a conductive component and at least one selected from AgTiO ３ , EuTiO ３ and NaTiO ３ and includes at least one selected therefrom, wherein at least one selected from AgTiO₃, EuTiO₃, and NaTiO₃ remains without being discharged from the internal electrode portion, a multilayer ceramic capacitor. Claim 2 The multilayer ceramic capacitor according to claim 1, wherein the internal electrode has a thickness of 1 µm or less. Claim 3 The multilayer ceramic capacitor according to claim 1 or 2, wherein the internal electrode has a coverage of 80% or more. Claim 4 The dielectric layer is made of a ceramic containing at least one selected from BaTiO ３ , SrTiO ３ and CaZrO ３ as a main component. The internal electrode further contains at least one selected from BaTiO ３ , SrTiO ３ and CaZrO ３ contained in the dielectric layer. The multilayer ceramic capacitor according to claim 1 or 2.

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