conductive paste

Abstract

To provide a conductive paste for an internal electrode of a layered ceramic capacitor, which is capable of maintaining relatively high coverage even if the internal electrode constitutes a thin layer.SOLUTION: Provided is a conductive paste for forming internal electrodes 4 and 5 of a layered ceramic capacitor 1 fabricated through a firing step. The conductive paste includes conductive metal powder, ceramic powder, an organic solvent, and an organic binder. The conductive metal powder contains a silver / palladium alloy. At least a portion of the ceramic powder comprises an ABO3 type oxide having a specific ion radius in which the ratio of the ion radius in the 6-coordination of an element at the A site in ABO3 with respect to the ion radius in the 6-coordination of a metal element contained in the conductive metal powder is 0.96 or more and 1.10 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a conductive paste, and more particularly to a conductive paste for forming internal electrodes in multilayer ceramic capacitors. [Background technology]

[0002] A multilayer ceramic capacitor typically comprises a laminate having a plurality of stacked dielectric layers made of ceramic, and a plurality of internal electrodes arranged 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 consist of a plurality of first internal electrodes and a plurality of second internal electrodes arranged alternately in the stacking direction of the laminate, and the external electrodes consist of a first external electrode electrically connected to the first internal electrodes and a second external electrode electrically connected to the second internal electrodes.

[0003] To miniaturize and increase the capacitance of multilayer ceramic capacitors with this structure, it is necessary to thin the dielectric layer and internal electrodes, as well as to improve the coverage (electrode continuity) of the internal electrodes. Generally, in the firing process during the manufacturing of multilayer ceramic capacitors, the temperature at which the conductive metal particles contained in the conductive paste film that will become the internal electrodes sinter is lower than the temperature at which the ceramic constituting the dielectric layer sintersects. As a result, the metal particles contained in the internal electrodes sinter first. This causes a decrease in the coverage of the internal electrodes. In particular, when the internal electrodes are thinned to a thickness of 1 μm or less, for example, the coverage tends to decrease, and this decrease in coverage easily hinders the increase in capacitance.

[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. By this, 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 close between the internal electrode and the dielectric layer. As a result, the coverage of the internal electrode becomes high and a large capacitance can be realized.

[0005] By the method described above, in order to increase the coverage of the internal electrode and realize a large capacitance, for example, as described in paragraph 0004 of Patent Document 1 (Japanese Unexamined Patent Application Publication No. 201-31807), 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, with respect to internal electrodes 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 conductive paste for forming an internal electrode that can maintain a relatively high coverage even when the internal electrode is thinned.

Means for Solving the Problems

[0009] The present invention is a conductive paste for forming an internal electrode of a multilayer ceramic capacitor, including conductive metal powder, ceramic powder, an organic solvent, and an organic binder. In order to solve the above-described technical problems, the conductive metal powder includes a silver / palladium alloy, and at least a part of the ceramic powder is a powder composed of an ABO3-type oxide having a specific ionic radius such that the ratio of the ionic radius in the 6-fold coordination of the element at the A site in ABO3 to the ionic radius in the 6-fold coordination of the silver / palladium alloy is 0.96 or more and 1.10 or less.

Effects of the Invention

[0010] If an internal electrode of a multilayer ceramic capacitor is formed with the conductive paste according to the present invention, the coverage of the internal electrode can be increased. Therefore, even when the internal electrode is thinned, the coverage of the internal electrode can be maintained high, and an increase in the capacitance of the multilayer ceramic capacitor can be prevented from being inhibited.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing a multilayer ceramic capacitor 1 to which the conductive paste according to the present invention is applied. [Modes for carrying out the invention]

[0012] Referring to Figure 1, the structure of the multilayer ceramic capacitor 1 to which the conductive paste according to this invention is applied will be described.

[0013] The multilayer ceramic capacitor 1 comprises a laminate 2. The laminate 2 comprises a plurality of stacked dielectric layers 3 made of ceramic, and a plurality of internal electrodes 4 and 5 arranged 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, which are alternately arranged in the stacking direction of the laminate 3. The outer surface of the laminate 2, more specifically, each opposing end face, is provided with a first external electrode 6 and a second external electrode 7, 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.

[0014] The dielectric layer 3 is made of a ceramic mainly composed of ABO3 (where A is at least one of Ba, Ca, and Sr, and B is at least one of Ti and Zr). Alternatively, the ceramic may be mainly composed of the above ABO3 and may also contain at least one of Mn, Mg, Si, Y, Dy, and Gd as a minor component.

[0015] Internal electrodes 4 and 5 contain a silver / palladium alloy as a conductive component. Furthermore, as a characteristic composition, internal electrodes 4 and 5 contain, for example, (Ag 0.7 Pd 0.3 ) Contains at least one selected from TiO3, NaTiO3, and EuTiO3. (Ag 0.7 Pd 0.3 TiO3, NaTiO3, and EuTiO3 have an ilmenite crystal structure.

[0016] 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, and the ceramic material is (Ag 0.7 Pd 0.3 It includes at least one selected from TiO3, NaTiO3, and EuTiO3, and optionally further includes at least one selected from BaTiO3, SrTiO3, and CaZrO3 contained in the dielectric layer 3.

[0017] External electrodes 6 and 7 are formed, for example, by applying a conductive paste, mainly composed of Ag or Cu, to the end face of the laminate 2 and baking it. If necessary, a Ni plating and then a Sn plating may be applied to the thick film formed by baking.

[0018] A multilayer ceramic capacitor 1 is manufactured, for example, through the following process. First, a ceramic slurry containing ceramic raw material powder having the above composition is prepared. Next, a suitable sheet molding method is applied to the ceramic slurry to form a ceramic green sheet. Next, conductive pastes that will become the internal electrodes 4 and 5 are applied to a predetermined ceramic green sheet from among several ceramic green sheets by printing or other means. Next, the multiple ceramic green sheets are laminated and then pressed together to obtain a raw laminate. Next, the raw laminate is fired. In this firing process, the ceramic green sheets become the dielectric layer 3. After that, external electrodes 6 and 7 are formed on the end faces of the laminate 3.

[0019] The conductive paste that will form the internal electrodes 4 and 5 used in the manufacture of the multilayer ceramic capacitor 1 described above is preferably prepared as follows.

[0020] 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.

[0021] More specifically, in the first step, a ceramic powder slurry is produced by mixing a ceramic powder and a dispersant in an organic solvent.

[0022] As the above-mentioned ceramic powder, for example, as an ABO3 oxide, (Ag 0.7 , Pd 0.3 )TiO3, at least one selected from NaTiO3 and EuTiO3 is used. Furthermore, in addition to this, at least one selected from BaTiO3, SrTiO3, and CaZrO3 as a co-material may be used.

[0023] Since the conductive metal powder contained in the metal powder slurry produced in the second step described later contains a silver / palladium alloy, (Ag 0.7 , Pd 0.3 )TiO3, NaTiO3, and EuTiO3 as the above-mentioned ABO3 oxides are ABO3-type oxides with a specific ionic radius such that 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 is 0.96 or more and 1.10 or less.

[0024] As an ABO3 oxide, (Ag 0.7 , Pd 0.3A ceramic powder consisting of at least one selected from TiO3, NaTiO3, and EuTiO3 can suppress reactions that may occur during firing with the conductive metal powder contained in the metal powder slurry produced in the second step. The ceramic powder may mainly consist of the above ABO3 oxide and may also contain at least one of Mn, Mg, Si, Y, Dy, and Gd as a minor component. When such a minor component is included, grain growth of the ceramic particles may be suppressed, and sintering of the metal particles may be effectively suppressed.

[0025] 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.

[0026] In the second step, a metal powder slurry is prepared by mixing conductive metal powder and a dispersant with an organic solvent. As the conductive metal powder, for example, a powder consisting of an alloy of 70 atm% silver and 30 atm% palladium can be used. The dispersant and organic solvent used in the second step can be the same as those used in the first step.

[0027] In the third step, an organic vehicle is prepared by mixing an organic resin component with an organic solvent. For example, ethyl cellulose resin can be used as the organic resin component. The organic solvent used in the third step can be the same as the one used in the first step.

[0028] In the fourth step, the ceramic powder slurry, metal powder slurry, and organic vehicle described above are mixed. This yields a conductive paste that will become the internal electrodes 4 and 5. This conductive paste contains the ceramic powder slurry, and the ceramic powder slurry, as described above, is (Ag) as an ABO3 oxide with a specific ionic radius. 0.7 Pd 0.3Since it contains ceramic powder consisting 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 This will include at least one selected from TiO3, NaTiO3, and EuTiO3.

[0029] [Example of experiment] Next, we will describe experimental examples conducted to confirm the effects of this invention.

[0030] In this experimental example, a silver / palladium alloy powder consisting of an alloy of 70 atm% silver and 30 atm% palladium was prepared as the conductive metal powder to be included in the conductive paste for forming internal electrodes.

[0031] On the other hand, as an ABO3 oxide with a specific ionic radius that constitutes the ceramic powder contained in the conductive paste for forming internal electrodes, (Ag 0.7 Pd 0.3 In addition to TiO3, NaTiO3, and EuTiO3, BaTiO3, CaZrO3, and SrTiO3 were also prepared. Table 1 shows the "crystal structure," "coordination number," "A-site element," and "ionic radius" for these ABO3 oxides. Note that while Ba, Ca, and Sr are 12-coordinate in the original perovskite structure, they also become 6-coordinate when dissolved in the 6-coordinate elements (Ag / Pd, Na, Eu) of the ilmenite structure. Therefore, the "ionic radius" in Table 1 shows the value for 6-coordination.

[0032] [Table 1]

[0033] Below, we describe Experimental Examples 1, 2, and 3, which were conducted by changing the ceramic raw materials that make up the dielectric layer.

[0034] (Experimental Example 1) Main component of the ceramic constituting the dielectric layer: BaTiO3 1. Fabrication of BaTiO3-based ceramic raw materials for the dielectric layer As starting materials, the main components BaCO3 and TiO2 powders were weighed and mixed in a ball mill for 72 hours, then heat-treated at a top temperature of 1000°C for 2 hours to obtain heat-treated powder. On the other hand, as minor components, powders of MnO, Dy2O3, MgO, SiO2, and BaCO3 were prepared. The minor component powders were weighed to the heat-treated powder so that the composition ratio was 100BaTiO3 + 0.5Mn + 1.0Dy + 1.0Mg + 1.0Si + 2.0Ba. These minor component powders were added to the heat-treated powder and mixed in a ball mill for 24 hours, then dried to obtain BaTiO3-based ceramic raw material powder.

[0035] 2. Preparation of conductive paste for internal electrode formation The "ABO3 oxide" powder shown in Table 2 below, along with the BaTiO3-based ceramic raw material powder for the dielectric layer, were used as ceramic powders included in the conductive paste for forming the internal electrodes.

[0036] These "ABO3 oxide" powders and BaTiO3-based ceramic raw material powders were weighed to the "addition ratios" shown in Table 2. These powders, along with dihydroterpineol as an organic solvent and an anionic polymer dispersant as a dispersant, were pre-mixed in a medium-free stirring mill, and then dispersed in a medium-stirring mill to produce a ceramic powder slurry (Step 1).

[0037] On the other hand, a metal powder slurry was prepared by dispersing silver / palladium alloy powder as a conductive metal powder, dihydroterpineol as an organic solvent, and an anionic polymer dispersant as a dispersant using a three-roll mill (second step).

[0038] Furthermore, an organic vehicle was obtained by mixing ethylcellulose resin, which is an organic resin component, with dihydroterpineol, which is an organic solvent (third step).

[0039] Subsequently, the above-mentioned metal powder slurry and ceramic powder slurry were added to the above-mentioned organic vehicle and mixed and dispersed to prepare a conductive paste for forming internal electrodes (Step 4).

[0040] Table 2 shows the ratio of the ionic radius of the A-site element in 6-coordinate to the ionic radius of the silver / palladium alloy that should be included in the internal electrode, i.e., "ionic radius ratio (A-site element / Ag 0.7 Pd 0.3 The term "alloy)" is indicated. For sample 7, the ratio of the ionic radius of the silver / palladium alloy in 6-coordinate state (1.06 Å) to the ionic radius of the Ba element in 6-coordinate state (1.35 Å), as shown in Table 1, is indicated.

[0041] 3. Fabrication of multilayer ceramic capacitors A ceramic slurry containing the BaTiO3-based ceramic raw material powder prepared in step 1 above was prepared, and then a doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Next, the conductive paste for forming internal electrodes, prepared in step 2 above, was applied to a predetermined ceramic green sheet from among several ceramic green sheets by screen printing. Then, the multiple ceramic green sheets were stacked and pressed together to obtain a raw laminate. Next, the raw laminate was fired. After that, external electrodes were formed on the end faces of the sintered laminate to produce a multilayer ceramic capacitor sample.

[0042] 4. Evaluation

[0043] [Table 2]

[0044] The internal electrode and dielectric layer located in the central part of the laminate in the height direction of the multilayer ceramic capacitor sample were separated from each other by field delamination.

[0045] Next, the central part of the exposed internal electrode (at the 1 / 2 point in both the width and length directions) was observed using a microscope at a magnification of 100x. By analyzing the obtained images, the percentage of the area occupied by the conductive film as the internal electrode in the exposed portion was determined as "coverage," as shown in Table 2. Samples with a "coverage" of 80% or more were judged as good and marked with "○" in the "Evaluation" column, while samples with a "coverage" lower than 80% were judged as poor and marked with "×" in the "Evaluation" column.

[0046] 5. Discussion Samples 1-6 in Table 2 have a "○" rating. In these samples 1-6, the internal electrode contains (Ag) as the ABO3 oxide. 0.7 Pd 0.3 It contains one of the following: TiO3, NaTiO3, or EuTiO3. Additionally, the internal electrodes contain a silver / palladium alloy as a conductive component.

[0047] Now, focusing on the ionic radius, first, as shown in the "(Ag,Pd)TiO3" column in Table 1, the ionic radius of the silver / palladium alloy in 6-coordinate is 1.06 Å. On the other hand, the ABO3 oxide contained in the internal electrodes of samples 1-6 is (Ag 0.7 Pd 0.3 The ionic radii of the element at the A site of TiO3, NaTiO3, and EuTiO3 in 6-coordinate configuration are 1.06 Å, 1.02 Å, and 1.17 Å, respectively, as shown in Table 1.

[0048] In samples 1-6, which were evaluated as "○", the ratio of the ionic radius of the element at the A site in ABO3 in a 6-coordinate state to the ionic radius of the metal element contained in the conductive metal particles in a 6-coordinate state, i.e., the "ionic radius ratio", is 0.96 or greater and 1.10 or less.

[0049] Thus, (Ag) is used as an ABO3 oxide in samples 1-6. 0.7 Pd 0.3TiO3, NaTiO3, and EuTiO3 have ionic radii at the A site in ABO3 in a 6-coordinate configuration that are equal to or close to the ionic radii of the silver / palladium alloy, which is the conductive metal to be included in the internal electrode, in a 6-coordinate configuration. As a result, the energy difference with the silver / palladium alloy in the internal electrode becomes zero or small, and they remain without being discharged from the internal electrode, thus improving the heat resistance of the internal electrode. As a result, it is presumed that the coverage was high, exceeding 82%, in samples 1-6.

[0050] Also, as in samples 4-6, (Ag 0.7 Pd 0.3 The addition ratio of TiO3, NaTiO3, and EuTiO3 is not necessarily 100%, but is 10% or more. 0.7 Pd 0.3 Compared to cases that do not contain any of TiO3, NaTiO3, or EuTiO3, an improvement in coverage was observed.

[0051] In contrast to these, in sample 7, which was evaluated as "×", only BaTiO3 as a co-material was added to the internal electrode. In this case, although Ba, the element at the A site in the perovskite structure ABO3, is 12-coordinate, when solid-solubilating into the A site of the ilmenite structure, it is necessary to compare the ionic radius at 6-coordinate, which is the coordination number of the A site in the ilmenite structure. As shown in Table 1, the ionic radius of Ba at 6-coordinate is 1.35 Å. Therefore, the ratio of the ionic radius of Ba at 6-coordinate to the ionic radius of the silver / palladium alloy at 6-coordinate, i.e., the "ionic radius ratio", is 1.27. Thus, the "ionic radius ratio" falls outside the range of 0.96 or more and 1.10 or less, resulting in a low coverage of 75%.

[0052] In sample 7, the "ionic radius ratio" fell outside the range of 0.96 or higher and 1.10 or lower. It is presumed that BaTiO3 was discharged from the internal electrode portion, preventing improvement in the heat resistance of the internal electrode and resulting in low coverage.

[0053] (Experimental Example 2) Main component of the ceramic constituting the dielectric layer: CaZrO3 1. Fabrication of CaZrO3-based ceramic raw materials for the dielectric layer As starting materials, the main components CaCO3 and ZrO2 powders, along with the minor components MnO, SiO2, and MgO powders, were weighed, mixed in 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.

[0054] 2. Preparation of conductive paste for internal electrode formation The "ABO3 oxide" powder shown in Table 3 below and the CaZrO3-based ceramic raw material powder for the dielectric layer were used as ceramic powders included in the conductive paste for forming the internal electrodes.

[0055] These "ABO3 oxide" powders and CaZrO3-based ceramic raw material powders were weighed to the "addition ratios" shown in Table 3, and a conductive paste for forming internal electrodes was prepared by following the same process as in Experimental Example 1 above.

[0056] Table 3, as in Table 2, shows the "ionic radius ratio (A site element / Ag 0.7 Pd 0.3 The term "alloy)" is indicated. For sample 17, the ratio of the ionic radius of the element Ca in a 6-coordinate state (1.00 Å) to the ionic radius of the silver / palladium alloy in a 6-coordinate state (1.06 Å) as shown in Table 1 is indicated.

[0057] 3. Fabrication of multilayer ceramic capacitors A ceramic slurry containing the CaZrO3-based ceramic raw material powder prepared in step 1 above was prepared, and then a doctor blade method was applied to the ceramic slurry to form a ceramic green sheet. Subsequently, a multilayer ceramic capacitor to be used as a sample was fabricated through the same process as in Experimental Example 1.

[0058] 4. Evaluation

[0059] [Table 3]

[0060] Following the same procedure as in Experimental Example 1, "coverage" was calculated and evaluated in the same manner, as shown in Table 3.

[0061] 5. Discussion Samples 11-16 in Table 3 are marked with "○" for "Evaluation". In these samples 11-16, the internal electrode contains (Ag) as the ABO3 oxide. 0.7 Pd 0.3 It contains one of the following: TiO3, NaTiO3, or EuTiO3. Additionally, the internal electrodes contain a silver / palladium alloy as a conductive component.

[0062] Now, focusing on the ionic radius, first, as shown in the "(Ag,Pd)TiO3" column in Table 1, the ionic radius of the silver / palladium alloy in 6-coordinate is 1.06 Å. On the other hand, the ABO3 oxide contained in the internal electrodes of samples 11-16 is (Ag 0.7 Pd 0.3 The ionic radii of the element at the A site of TiO3, NaTiO3, and EuTiO3 in 6-coordinate configuration are 1.06 Å, 1.02 Å, and 1.17 Å, respectively, as shown in Table 1.

[0063] In samples 11-16, which were evaluated as "○", the ratio of the ionic radius of the element at the A site in ABO3 in a 6-coordinate state to the ionic radius of the metal element contained in the conductive metal particles in a 6-coordinate state, i.e., the "ionic radius ratio", is 0.96 or greater and 1.10 or less.

[0064] Thus, (Ag) is used as an ABO3 oxide in samples 11-16. 0.7 Pd 0.3TiO3, NaTiO3, and EuTiO3 have ionic radii at the A site in ABO3 in a 6-coordinate configuration that are equal to or close to the ionic radii of the silver / palladium alloy, which is the conductive metal that should be included in the internal electrode, in a 6-coordinate configuration. As a result, the energy difference with the silver / palladium alloy in the internal electrode becomes zero or small, and they remain without being discharged from the internal electrode portion, acting to improve the heat resistance of the internal electrode. Consequently, it is presumed that the coverage in samples 11-16 was high, exceeding 81%.

[0065] Also, as in samples 14-16, (Ag 0.7 Pd 0.3 The addition ratio of TiO3, NaTiO3, and EuTiO3 is not necessarily 100%, but is 10% or more. 0.7 Pd 0.3 Compared to cases that do not contain any of TiO3, NaTiO3, or EuTiO3, an improvement in coverage was observed.

[0066] In contrast to these, sample 17, which was evaluated as "×", only CaZrO3 as a co-material was added to the internal electrode. In this case, Ca, the element at the A site in the perovskite structure ABO3, is 12-coordinate, but when solid-solubilating into the A site of the ilmenite structure, it is necessary to compare the ionic radius at 6-coordinate, which is the coordination number of the A site in the ilmenite structure. As shown in Table 1, the ionic radius of Ca at 6-coordinate is 1.00 Å. Therefore, the ratio of the ionic radius of Ca at 6-coordinate to the ionic radius of the silver / palladium alloy at 6-coordinate, i.e., the "ionic radius ratio", is 0.94. Thus, the "ionic radius ratio" falls outside the range of 0.96 or more and 1.10 or less, resulting in a low coverage of 72%.

[0067] In sample 17, the "ionic radius ratio" fell outside the range of 0.96 or higher and 1.10 or lower. It is presumed that CaZrO3 was discharged from the internal electrode portion, preventing improvement in the heat resistance of the internal electrode and resulting in low coverage.

[0068] (Experimental Example 3) Main component of the ceramic constituting the dielectric layer: SrTiO3 1. Fabrication of SrTiO3-based ceramic raw materials for the dielectric layer As starting materials, the main components SrCO3 and TiO2 powders, along with the minor components MnO, SiO2, and MgO powders, were weighed, mixed in 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.

[0069] 2. Preparation of conductive paste for internal electrode formation The "ABO3 oxide" powder shown in Table 4 below, along with the SrTiO3-based ceramic raw material powder for the dielectric layer, were used as ceramic powders included in the conductive paste for forming the internal electrodes.

[0070] These "ABO3 oxide" powders and SrTiO3-based ceramic raw material powders were weighed to the "addition ratios" shown in Table 4, and a conductive paste for forming internal electrodes was prepared by following the same process as in Experimental Example 1 above.

[0071] Table 4, as in Table 2, shows "Ionic radius ratio (A site element / Ag 0.7 Pd 0.3 The term "alloy)" is indicated. For sample 27, the ratio of the ionic radius of the silver / palladium alloy in 6-coordinate state (1.06 Å) to the ionic radius of the Sr element in 6-coordinate state (1.18 Å), as shown in Table 1, is indicated.

[0072] 3. Fabrication of multilayer ceramic capacitors A ceramic slurry containing the SrTiO3-based ceramic raw material powder prepared in step 1 above was prepared, and then a ceramic green sheet was formed by applying the doctor blade method to the ceramic slurry. Subsequently, a multilayer ceramic capacitor to be used as a sample was fabricated through the same process as in Experimental Example 1.

[0073] 4. Evaluation

[0074] [Table 4]

[0075] Following the same procedure as in Experimental Example 1, "coverage" was calculated and evaluated in the same manner, as shown in Table 4.

[0076] 5. Discussion Samples 21-26 in Table 4 have a "○" rating. In these samples 21-26, the internal electrode contains (Ag) as an ABO3 oxide. 0.7 Pd 0.3 It contains one of the following: TiO3, NaTiO3, or EuTiO3. Additionally, the internal electrodes contain a silver / palladium alloy as a conductive component.

[0077] Now, focusing on the ionic radius, first, as shown in the "(Ag,Pd)TiO3" column in Table 1, the ionic radius of the silver / palladium alloy in 6-coordinate is 1.06 Å. On the other hand, the ABO3 oxide contained in the internal electrodes of samples 21-26 is (Ag 0.7 Pd 0.3 The ionic radii of the element at the A site of TiO3, NaTiO3, and EuTiO3 in 6-coordinate configuration are 1.06 Å, 1.02 Å, and 1.17 Å, respectively, as shown in Table 1.

[0078] In samples 21-26, which were evaluated as "○", the ratio of the ionic radius of the A-site element in ABO3 in six-coordinate configuration to the ionic radius of the silver / palladium alloy in six-coordinate configuration, i.e., the "ionic radius ratio", is between 0.96 and 1.10.

[0079] Thus, (Ag) is used as an ABO3 oxide in samples 21-26. 0.7 Pd 0.3TiO3, NaTiO3, and EuTiO3 have ionic radii at the A site in ABO3 in a 6-coordinate configuration that are equal to or close to the ionic radii of the silver / palladium alloy, which is the conductive metal that should be included in the internal electrode, in a 6-coordinate configuration. As a result, the energy difference with the silver / palladium alloy in the internal electrode becomes zero or small, and they remain without being discharged from the internal electrode portion, acting to improve the heat resistance of the internal electrode. Consequently, it is presumed that the coverage in samples 21-26 was high, exceeding 80%.

[0080] Also, as in samples 24-26, (Ag 0.7 Pd 0.3 The addition ratio of TiO3, NaTiO3, and EuTiO3 is not necessarily 100%, but is 10% or more. 0.7 Pd 0.3 Compared to cases that do not contain any of TiO3, NaTiO3, or EuTiO3, an improvement in coverage was observed.

[0081] In contrast to these, sample 27, which was evaluated as "×", only SrTiO3 as a co-material was added to the internal electrode. In this case, Sr, the element at the A site in the perovskite structure ABO3, is 12-coordinate. However, when solid-solubilating into the A site of the ilmenite structure, it is necessary to compare the ionic radius at 6-coordinate, which is the coordination number of the A site in the ilmenite structure. As shown in Table 1, the ionic radius of Sr at 6-coordinate is 1.18 Å. Therefore, the ratio of the ionic radius of Sr at 6-coordinate to the ionic radius of the silver / palladium alloy at 6-coordinate, i.e., the "ionic radius ratio", is 1.11. Thus, the "ionic radius ratio" falls outside the range of 0.96 or higher and 1.10 or lower, resulting in a low coverage of 70%.

[0082] In sample 27, the "ionic radius ratio" fell outside the range of 0.96 or higher and 1.10 or lower. It is presumed that SrTiO3 was discharged from the internal electrode portion, preventing improvement in the heat resistance of the internal electrode and resulting in low coverage.

[0083] In the experimental examples 1 to 3 described above, the powder consisting of an ABO3 type oxide with a specific ionic radius, which is at least a part of the ceramic powder contained in the conductive paste, is (Ag 0.7 Pd 0.3 ) was at least one selected from TiO3, NaTiO3, and EuTiO3, but other types may also be used. In other words, any ABO3 type oxide with a specific ionic radius is acceptable, as long as the ratio of the ionic radius of the element at the A site in ABO3 in six-coordinate configuration to the ionic radius of the silver / palladium alloy in six-coordinate configuration contained in the conductive paste is 0.96 or more and 1.10 or less.

[0084] Embodiments of this invention include the following:

[0085] <1> A conductive paste for forming internal electrodes of a multilayer ceramic capacitor, comprising conductive metal powder, ceramic powder, an organic solvent, and an organic binder, The conductive metal powder includes a silver / palladium alloy. A conductive paste in which at least a portion of the ceramic powder is a powder made of an ABO3 type oxide with a specific ionic radius such that the ratio of the ionic radius of the A-site element in ABO3 in a 6-coordinate configuration to the ionic radius of the silver / palladium alloy in a 6-coordinate configuration is 0.96 or more and 1.10 or less.

[0086] <2> The aforementioned ABO3 type oxide with a specific ionic radius has an ilmenite crystal structure. <1> The conductive paste described above.

[0087] <3> The aforementioned ABO3 type oxide with a specific ionic radius is (Ag 0.7 Pd 0.3 ) At least one selected from TiO3, NaTiO3, and EuTiO3. <2> The conductive paste described above.

[0088] <4> The ceramic powder comprises at least 10% by volume of an ABO3 type oxide with the specified ionic radius, and the remainder of the ceramic powder is a powder mainly composed of at least one selected from BaTiO3, SrTiO3, and CaZrO3. <1> or <3> A conductive paste as described in any of the following. [Explanation of symbols]

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

Claims

1. A conductive paste for forming internal electrodes of a multilayer ceramic capacitor, comprising conductive metal powder, ceramic powder, an organic solvent, and an organic binder, The conductive metal powder includes a silver / palladium alloy. At least a portion of the aforementioned ceramic powder is ABO relative to the ionic radius of the silver / palladium alloy in 6-coordinate configuration. ３ ABO of a specific ionic radius such that the ratio of ionic radii of the element at site A in 6-coordinate is 0.96 or greater and 1.10 or less. ３ A conductive paste, which is a powder made of a specific type of oxide.

2. The ABO of the specified ionic radius ３ The conductive paste according to claim 1, wherein the oxide of the type has an ilmenite crystal structure.

3. The ABO of the specific ionic radius ３ type oxide is (Ag 0.7 , Pd 0.3 ), TiO ３ , NaTiO ３ and EuTiO ３ The conductive paste according to claim 2, which is at least one selected from the group consisting of

4. 10% by volume or more of the ceramic powder is ABO of the specified ionic radius ３ The powder consists of an oxide of a certain type, and the remainder of the ceramic powder is BaTiO ３ SrTiO ３ and CaZrO ３ A conductive paste according to any one of claims 1 to 3, wherein the conductive paste is a powder mainly composed of at least one selected from the following.

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