Multilayer ceramic capacitor

Abstract

The present invention provides a multilayer ceramic capacitor comprising an internal electrode that is capable of maintaining coverage relatively high even if formed into a thin layer.　A multilayer ceramic capacitor (1) comprising a multilayer body (2) having a plurality of stacked dielectric layers (3) that are formed from a ceramic, and also having 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 a silver / palladium alloy as an electroconductive component and also contain at least one selected from (Ag0.7, Pd0.3)TiO3, NaTiO3, and EuTiO3.

Description

Technical Field

[0001] This invention relates to a multilayer ceramic capacitor, and particularly to the composition of internal electrodes provided in a 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 an 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 electrode thinner and to increase the coverage (electrode continuity) of the internal electrode. Generally, in the firing process in 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 electrode. In particular, in the case of an internal electrode thinned to a thickness of 1 μm or less, for example, the coverage is likely to decrease, and there is a problem that such a decrease in coverage tends to inhibit an increase in capacitance.

[0004] Therefore, in order to form a thinned internal electrode with a high coverage, it is necessary to increase the temperature at which the conductive metal particles contained in the conductive paste film to be the internal electrode sinter in the firing process during the manufacture of the multilayer ceramic capacitor. As a result, the temperature at which the metal particles contained in the conductive paste film to be the internal electrode sinter can be brought closer to the temperature at which the ceramic constituting the dielectric layer starts to sinter, 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 Patent Application Laid-Open No. 2016-31807), a ceramic material having a composition similar to the composition of the ceramic constituting the dielectric layer, that is, a co-material, is added 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 sinter can be brought closer to the temperature at which the ceramic constituting the dielectric layer sinters.

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 electrode contains a silver / palladium alloy as a conductive component and at least one selected from (Ag 0.7 ,Pd 0.3 )TiO3, NaTiO3, and EuTiO3.

Effects of the Invention

[0011] According to the present invention, at least one selected from (Ag 0.7 ,Pd 0.3 )TiO3, NaTiO3, and EuTiO3 contained in the internal electrode contributes to increasing the coverage of the internal electrode containing a silver / palladium alloy as a conductive component. Therefore, even when the internal electrode is thinned, the coverage of the internal electrode 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

[0013] With reference 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 a silver / palladium alloy as a conductive component. Further, as a characteristic composition, the internal electrodes 4 and 5 contain at least one selected from (Ag 0.7 ,Pd 0.3 )TiO3, NaTiO3, and EuTiO3. (Ag 0.7 ,Pd 0.3 )TiO3, NaTiO3, and EuTiO3 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 a silver / palladium alloy as a conductive component. As the ceramic material, (Ag 0.7 , Pd 0.3 )TiO3, at least one selected from NaTiO3 and EuTiO3, and, if necessary, further contains 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, a 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 a 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 manufacturing 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, the ceramic powder slurry is produced by mixing the ceramic powder and the dispersant into the organic solvent.

[0023] As the above-mentioned ceramic powder, for example, (Ag 0.7 , Pd 0.3 ) TiO3, NaTiO3, and EuTiO3 selected from at least one of them are used. Further, in addition to this, those composed of at least one selected from BaTiO3, SrTiO3, and CaZrO3 as a co-material may be used.

[0024] Since the conductive metal powder contained in the metal powder slurry produced in the second step described later contains a silver / palladium alloy, (Ag as the above-mentioned ABO3 oxide 0.7 , Pd 0.3 ) TiO3, NaTiO3, and EuTiO3 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 at the 6-fold coordination of the silver / palladium alloy is 0.96 or more and 1.10 or less.

[0025] (Ag as the ABO3 oxide 0.7 , Pd 0.3)According to the ceramic powder composed of at least one selected from TiO3, NaTiO3, and EuTiO3, during firing, the reaction that may occur with the conductive metal powder contained in the metal powder slurry produced in the second step 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 such a sub-component is included, the grain growth of the ceramic particles may be suppressed, and the sintering of the metal particles may 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, and as the organic solvent, for example, dihydroterpineol can be used.

[0027] In the second step, a metal powder slurry is produced by mixing the conductive metal powder and the dispersant in an organic solvent. As the conductive metal powder, for example, a powder composed of an alloy of 70 atm% silver and 30 atm% palladium is used. As the dispersant and the organic solvent used in the second step, the same ones as those used in the first step can be used.

[0028] In the third step, an organic vehicle is produced by mixing the organic resin component in an organic solvent. As the organic resin component, for example, an ethyl cellulose resin can be used. For the organic solvent used in the third step, the same one as that 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 the ceramic powder slurry, and the ceramic powder slurry is, as described above, (Ag as the ABO3 oxide with a specific ionic radius 0.7 ,Pd 0.3)Since it contains ceramic powder composed of at least one selected from TiO3, NaTiO3, and EuTiO3, the internal electrodes 4 and 5 provided in the multilayer ceramic capacitor 1 manufactured through the firing process are (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 will contain at least one selected from them.

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

[0031] In this experimental example, as the conductive metal powder contained in the conductive paste for forming the internal electrode, a silver / palladium alloy powder composed of an alloy of 70 atm% silver and 30 atm% palladium was prepared.

[0032] On the other hand, as the ABO3 oxide with a specific ionic radius that constitutes the ceramic powder contained in the conductive paste for forming the internal electrode, in addition to (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3, BaTiO3, CaZrO3, and SrTiO3 were prepared. Table 1 shows "crystal structure", "coordination number", "A-site element", and "ionic radius" for these ABO3 oxides. Note that Ba, Ca, and Sr are 12-coordinated in the original perovskite structure, but for Ba, Ca, and Sr as well, when they dissolve into the sites of the 6-coordinated elements (Ag / Pd, Na, Eu) of the ilmenite structure, they are 6-coordinated. Therefore, the "ionic radius" in Table 1 shows the value in 6-coordination.

[0033]

Table 1

[0034] Below, Experimental Example 1, Experimental Example 2, and Experimental Example 3 carried out by changing the ceramic raw material that constitutes 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 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 internal electrode formation The powder of "ABO3 oxide" shown in Table 2 below and the BaTiO3-based ceramic raw material powder for the dielectric layer were used as the ceramic powders contained in the conductive paste for internal electrode formation.

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

[0038] On the other hand, a silver / palladium alloy 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, followed by mixing and dispersion treatment to prepare a conductive paste for internal electrode formation (Step 4).

[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 the silver / palladium alloy in the 6-fold coordination contained in the internal electrode, that is, "ionic radius ratio (A-site element / Ag 0.7 Pd 0.3 Pd alloy)". For Sample 7, the ratio of the ionic radius of the Ba element (1.35 Å) in the 6-fold coordination shown in Table 1 to the ionic radius of the silver / palladium alloy in the 6-fold coordination (1.06 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. Then, the doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Next, the conductive paste for internal electrode formation 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, external electrodes were formed on the end faces of the sintered laminate to fabricate a multilayer 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 multilayer ceramic capacitor as a sample were peeled off from each other by dielectric breakdown.

[0046] Next, the vicinity of the central part of the exposed internal electrode (the position that is 1 / 2 in the width direction and 1 / 2 in the length direction) 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 part was determined as "coverage" shown in Table 2. Those with a "coverage" of 80% or more were judged to be good, and an "○" was entered in the "Evaluation" column. Those with a "coverage" lower than 80% were judged to be defective, and an "×" was entered in the "Evaluation" column.

[0047] 5. Discussion For Samples 1 to 6 in Table 2, the "Evaluation" is "○". In these Samples 1 to 6, the internal electrode contains one of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 as ABO3 oxide. Also, the internal electrode contains a silver / palladium alloy as a conductive component.

[0048] Here, regarding the ionic radius, first, as shown in the item of "(Ag, Pd)TiO3" in Table 1, the ionic radius of the silver / palladium alloy in 6 - coordination is 1.06 Å. On the other hand, the ionic radii of the elements at the A - site of each of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3, which are ABO3 oxides contained in the internal electrodes in Samples 1 to 6, in 6 - coordination are 1.06 Å, 1.02 Å, and 1.17 Å, respectively, as shown in Table 1.

[0049] In Samples 1 to 6 evaluated as "○", the ratio of the ionic radius of the element at the A - site in ABO3 to the ionic radius of the silver / palladium alloy in 6 - coordination, that is, the "ionic radius ratio" is 0.96 or more and 1.10 or less.

[0050] Thus, as the ABO3 oxide in Samples 1 to 6, (Ag 0.7 , Pd 0.3)TiO3, NaTiO3, and EuTiO3 have an ionic radius in the 6-fold coordination of the element at the A-site in ABO3 that is equal to or close to the ionic radius in the 6-fold coordination of the silver / palladium alloy as the conductive metal to be included in the internal electrode. Therefore, the energy difference with the silver / palladium alloy in the internal electrode becomes 0 or small, so it remains without being ejected from the internal electrode portion and acts to improve the heat resistance of the internal electrode. As a result, it is presumed that in Samples 1 to 6, the coverage became as high as 82% or more.

[0051] Also, as in Samples 4 to 6, (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 are not necessarily added at 100%, but if it is 10% or more, compared to the case where none of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 are included, an effect of improving the coverage was recognized.

[0052] In contrast, in Sample 7 evaluated as "×", only BaTiO3 as a co-material is added to the internal electrode. In this case, Ba, which is the element at the A-site in the perovskite structure ABO3, has a 12-fold coordination, but when it solid-solves into the A-site of the ilmenite structure, it is necessary to compare with the ionic radius in the 6-fold coordination, which is the coordination number of the A-site of the ilmenite structure. As shown in Table 1, the ionic radius of Ba in the 6-fold coordination is 1.35 Å. Therefore, the ratio of the ionic radius of Ba in the 6-fold coordination to the ionic radius of the silver / palladium alloy in the 6-fold coordination, that is, the "ionic radius ratio", is 1.27. Thus, the "ionic radius ratio" is outside the range of 0.96 or more and 1.10 or less, and the coverage became as low as 75%.

[0053] In Sample 7, the "ionic radius ratio" is outside the range of 0.96 or more and 1.10 or less, and it is presumed that BaTiO3 was ejected from the internal electrode portion, the heat resistance of the internal electrode was not improved, and the coverage became low.

[0054] (Experimental Example 2) Main component of the ceramic constituting the dielectric layer: CaZrO3 1. Preparation of CaZrO3-based ceramic raw materials for forming a 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.

[0055] 2. Preparation of conductive paste for forming an 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 ceramic powders contained in the conductive paste for forming an internal electrode.

[0056] These powders of "ABO3 oxide" and 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 an internal electrode was prepared through the same process as in the case of Experimental Example 1 above.

[0057] In Table 3, as in the case of Table 2, "ion radius ratio (A-site element / Ag 0.7 Pd 0.3 alloy)" is shown. For Sample 17, the ratio of the ionic radius (1.00 Å) of Ca element in 6 coordination shown in Table 1 to the ionic radius (1.06 Å) of silver / palladium alloy in 6 coordination is shown.

[0058] 3. Preparation 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 prepared through the same process as in the case of Experimental Example 1.

[0059] 4. Evaluation

[0060]

Table 3

[0061] 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.

[0062] 5. Discussion For Samples 11 to 16 in Table 3, the "evaluation" is "○". In these Samples 11 to 16, the internal electrode contains either (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, or EuTiO3 as the ABO3 oxide. Further, the internal electrode contains a silver / palladium alloy as a conductive component.

[0063] Here, regarding the ionic radius, first, as shown in the item of "(Ag, Pd)TiO3" in Table 1, the ionic radius of the silver / palladium alloy in the 6-fold coordination is 1.06 Å. On the other hand, the ionic radii of the elements at the A site of each of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3, which are included in the internal electrode in Samples 11 to 16 as the ABO3 oxide, are 1.06 Å, 1.02 Å, and 1.17 Å, respectively, as shown in Table 1.

[0064] In Samples 11 to 16 evaluated as "○", the ratio of the ionic radius of the element at the A site in ABO3 to the ionic radius of the silver / palladium alloy in the 6-fold coordination, that is, the "ionic radius ratio", is 0.96 or more and 1.10 or less.

[0065] Thus, as the ABO3 oxide in Samples 11 to 16, (Ag 0.7 , Pd 0.3)TiO3, NaTiO3, and EuTiO3 have an ionic radius in the 6-fold coordination of the element at the A-site in ABO3 that is equal to or close to the ionic radius in the 6-fold coordination of the silver / palladium alloy as the conductive metal to be included in the internal electrode. Therefore, the energy difference from the silver / palladium alloy in the internal electrode is 0 or small, remaining without being ejected from the internal electrode portion and acting to improve the heat resistance of the internal electrode. As a result, it is presumed that in Samples 11 to 16, the coverage became as high as 81% or more.

[0066] Also, like Samples 14 to 16, when the addition ratios of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 are not necessarily 100%, but if they are 10% or more, compared to the case where none of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 are included, an effect of improving the coverage was recognized.

[0067] In contrast, in Sample 17 evaluated as "×", only CaZrO3 as a co-material is added to the internal electrode. In this case, Ca, which is the element at the A-site in the perovskite structure ABO3, has a 12-fold coordination, but when it solid-solves into the A-site of the ilmenite structure, it is necessary to compare with the ionic radius in the 6-fold 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 the 6-fold coordination is 1.00 Å. Therefore, the ratio of the ionic radius of Ca in the 6-fold coordination to the ionic radius of the silver / palladium alloy in the 6-fold coordination, that is, the "ionic radius ratio", is 0.94. Thus, the "ionic radius ratio" is outside the range of 0.96 or more and 1.10 or less, and the coverage became as low as 72%.

[0068] In Sample 17, the "ionic radius ratio" is outside the range of 0.96 or more and 1.10 or less, and it is presumed that CaZrO3 was ejected from the internal electrode portion, the heat resistance of the internal electrode was not improved, and the coverage became low.

[0069] (Experimental Example 3) Main component of the ceramic constituting the dielectric layer: SrTiO3 1. Preparation of SrTiO3-based ceramic raw materials for forming a 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.

[0070] 2. Preparation of conductive paste for forming an 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 ceramic powders contained in the conductive paste for forming an internal electrode.

[0071] These powders of "ABO3 oxide" and 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 an internal electrode was prepared through the same process as in the case of Experimental Example 1 above.

[0072] In Table 4, similar to the case of Table 2, "ion radius ratio (A-site element / Ag 0.7 Pd 0.3 alloy)" is shown. For Sample 27, the ratio of the ionic radius of Sr element (1.18 Å) in 6 coordination shown in Table 1 to the ionic radius (1.06 Å) of silver / palladium alloy in 6 coordination is shown.

[0073] 3. Preparation 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 prepared through the same process as in the case of Experimental Example 1.

[0074] 4. Evaluation

[0075]

Table 4

[0076] Following the same procedure as in the case of Experimental Example 1, "coverage" was determined and evaluated in the same manner as shown in Table 4.

[0077] 5. Discussion For Samples 21 to 26 in Table 4, the "evaluation" is "○". In these Samples 21 to 26, the internal electrode contains either (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, or EuTiO3 as the ABO3 oxide. Further, the internal electrode contains a silver / palladium alloy as a conductive component.

[0078] Here, regarding the ionic radius, first, as shown in the item of "(Ag, Pd)TiO3" in Table 1, the ionic radius of the silver / palladium alloy in 6 - coordination is 1.06 Å. On the other hand, for each of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 which are ABO3 oxides contained in the internal electrodes in Samples 21 to 26, the ionic radius of the element at the A - site in 6 - coordination is 1.06 Å, 1.02 Å, and 1.17 Å, respectively, as shown in Table 1.

[0079] In Samples 21 to 26 evaluated as "○", the ratio of the ionic radius of the element at the A - site in ABO3 to the ionic radius of the silver / palladium alloy in 6 - coordination, that is, the "ionic radius ratio" is 0.96 or more and 1.10 or less.

[0080] Thus, for (Ag 0.7 , Pd 0.3)TiO3, NaTiO3, and EuTiO3 have an ionic radius in the 6-fold coordination of the element at the A site in ABO3 that is equal to or close to the ionic radius in the 6-fold coordination of the silver / palladium alloy as the conductive metal to be included in the internal electrode. Therefore, the energy difference from the silver / palladium alloy in the internal electrode becomes 0 or small, so it remains without being ejected from the internal electrode portion and acts to improve the heat resistance of the internal electrode. As a result, it is presumed that in Samples 21 to 26, the coverage became as high as 80% or more.

[0081] Also, as in Samples 24 to 26, when the addition ratios of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 are not necessarily 100%, but if they are 10% or more, compared to the case where none of (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 are included, an effect of improving the coverage was recognized.

[0082] On the other hand, in Sample 27 evaluated as "×", only SrTiO3 as a co-material is added to the internal electrode. In this case, Sr, which is the element at the A site in the perovskite structure ABO3, has a 12-fold 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-fold coordination, which is the coordination number of the A site of the ilmenite structure. As shown in Table 1, the ionic radius of Sr in the 6-fold coordination is 1.18 Å. Therefore, the ratio of the ionic radius of Sr in the 6-fold coordination to the ionic radius of the silver / palladium alloy in the 6-fold coordination, that is, the "ionic radius ratio" is 1.11. Thus, the "ionic radius ratio" is outside the range of 0.96 or more and 1.10 or less, and the coverage became as low as 70%.

[0083] In Sample 27, the "ionic radius ratio" is outside the range of 0.96 or more and 1.10 or less, SrTiO3 is ejected from the internal electrode portion, the heat resistance of the internal electrode is not improved, and it is presumed that the coverage became low.

[0084] Embodiments of this invention include the following.

[0085] <1> 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. The internal electrode includes a silver / palladium alloy as a conductive component and contains at least one selected from (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3. A multilayer ceramic capacitor.

[0086] <2> The internal electrode has a thickness of 1 μm or less. The multilayer ceramic capacitor according to <1>.

[0087] <3> The internal electrode has a coverage of 80% or more. The multilayer ceramic capacitor according to <1> or <2>.

[0088] <4> The dielectric layer is made of a ceramic having 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. The multilayer ceramic capacitor according to any one of <1> to <3>.

Explanation of Reference Numerals

[0089] 1 Multilayer ceramic capacitor 2 Laminate 3 Dielectric layer 4, 5 Internal electrode 6, 7 External electrode

Claims

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 a silver / palladium alloy as a conductive component and includes at least one selected from (Ag 0.7 , Pd 0.3 )TiO ３ , NaTiO ３ and EuTiO ３ . wherein at least one selected from (Ag 0.7, Pd 0.3 )TiO 3, NaTiO 3, and EuTiO 3 remains without being discharged from the internal electrodes, a multilayer ceramic capacitor.

2. The multilayer ceramic capacitor according to claim 1, wherein the internal electrode has a thickness of 1 μm or less.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein the internal electrode has a coverage of 80% or more.

4. The dielectric layer is made of a ceramic mainly composed of at least one selected from BaTiO ３ , SrTiO ３ and CaZrO ３ . 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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