Dielectric ceramic, manufacturing method therefor, and multilayer ceramic capacitor

The invention claimed is:

1. A dielectric ceramic comprising: a primary component comprising a barium titanate base composite oxide represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.sub.yHf.s- ub.jMg.sub.n)O.sub.3, in which 0.995.ltoreq.k.ltoreq.1.015, 0.ltoreq.h.ltoreq.0.03, 0.ltoreq.i.ltoreq.0.03, 0.015.ltoreq.m.ltoreq.0.035, 0.ltoreq.y<0.05, 0.ltoreq.j<0.05, 0.ltoreq.(y+j)<0.05, and 0.015.ltoreq.n.ltoreq.0.035, the Ba being partly replaced with Gd, and the Ti being partly replaced with Mg; and an additive component containing Ma, Mb and Mc in which Ma is at least one of Ba, Sr, and Ca, Mb is at least one of Mn and Ni, and Mc is Si or both Si and Ti, and in which Ma is contained in a positive amount which is less than 1.5 moles with respect to 100 moles of the primary component, Mb is contained in a positive amount which is less than 1.0 mole with respect to 100 moles of the primary component, and Mc is contained in a positive amount in the range of from 0.5 to 2.0 moles with respect to 100 moles of the primary component.

2. The dielectric ceramic according to claim 1, further comprising, with respect to 100 moles of the primary component, 0.5 moles or less of R.sub.2O.sub.3 in which R is at least one lanthanoid element other than Gd, Y, and Sc as a subcomponent.

3. The dielectric ceramic according to claim 2, further comprising, with respect to 100 moles of the primary component, a positive amount which is 1 mole of less of Al.sub.2O.sub.3.

4. A multilayer ceramic capacitor comprising: a laminate having dielectric ceramic layers which are laminated to each other and interior electrodes provided along interfaces between dielectric ceramic layers overlapped with each other in the lamination direction; and exterior electrodes on exterior surfaces of the laminate so as to be electrically connected to specific ones of the interior electrodes, wherein the dielectric ceramic layers each comprise the dielectric ceramic according to claim 2, and the interior electrodes each comprise a base metal.

5. A multilayer ceramic capacitor comprising: a laminate having dielectric ceramic layers which are laminated to each other and interior electrodes provided along interfaces between dielectric ceramic layers overlapped with each other in the lamination direction; and exterior electrodes on exterior surfaces of the laminate so as to be electrically connected to specific ones of the interior electrodes, wherein the dielectric ceramic layers each comprise the dielectric ceramic according to claim 3, and the interior electrodes each comprise a base metal.

6. The dielectric ceramic according to claim 3, wherein the primary component contains less than 0.02 w % of alkali metal oxide and the dielectric ceramic has an average crystal grain size of 2.5 .mu.m or less.

7. A multilayer ceramic capacitor comprising: a laminate having dielectric ceramic layers which are laminated to each other and interior electrodes provided along interfaces between dielectric ceramic layers overlapped with each other in the lamination direction; and exterior electrodes on exterior surfaces of the laminate so as to be electrically connected to specific ones of the interior electrodes, wherein the dielectric ceramic layers each comprise the dielectric ceramic according to claim 6, and the interior electrodes each comprise a base metal.

8. The dielectric ceramic according to claim 6, wherein the dielectric ceramic has an average crystal grain size of 1.5 .mu.m or less.

9. The dielectric ceramic according to claim 8, wherein the dielectric ceramic has an average crystal grain size of 1.5 .mu.m or less.

10. A multilayer ceramic capacitor comprising: a laminate having dielectric ceramic layers which are laminated to each other and interior electrodes provided along interfaces between dielectric ceramic layers overlapped with each other in the lamination direction; and exterior electrodes on exterior surfaces of the laminate so as to be electrically connected to specific ones of the interior electrodes, wherein the dielectric ceramic layers each comprise the dielectric ceramic according to claim 1, and the interior electrodes each comprise a base metal.

11. The dielectric ceramic according to claim 1, further comprising, with respect to 100 moles of the primary component, 1 mole of less of Al.sub.2O.sub.3.

12. The dielectric ceramic according to claim 11, wherein the primary component contains less than 0.02 w % of alkali metal oxide and the dielectric ceramic.

13. A multilayer ceramic capacitor comprising: a laminate having dielectric ceramic layers which are laminated to each other and interior electrodes provided along interfaces between dielectric ceramic layers overlapped with each other in the lamination direction; and exterior electrodes on exterior surfaces of the laminate so as to be electrically connected to specific ones of the interior electrodes, wherein the dielectric ceramic layers each comprise the dielectric ceramic according to claim 12, and the interior electrodes each comprise a base metal.

14. The dielectric ceramic according to claim 12, wherein the dielectric ceramic has an average crystal grain size of 1.5 .mu.m or less.

15. The dielectric ceramic according to claim 14, wherein the dielectric ceramic has an average crystal grain size of 1 .mu.m or less.

16. The dielectric ceramic according to claim 1, wherein 0.997.ltoreq.k.ltoreq.1.01, 0.ltoreq.h.ltoreq.0.01, 0.ltoreq.i.ltoreq.0.02, 0.02.ltoreq.y<0.03, 0.ltoreq.j<0.04, 0.02.ltoreq.(y+j)<0.04; Ma is 0.1-0.8 moles with respect to 100 moles of the primary component; Mb is 0.2-0.9 mole with respect to 100 moles of the primary component; Mc is 0.8 to 1.5 moles with respect to 100 moles of the primary component; and the dielectric ceramic has an average crystal grain size of 2.5 .mu.m or less.

17. A method for manufacturing a dielectric ceramic comprising: providing a reaction product comprising a barium titanate base composite oxide represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.sub.yHf.s- ub.jMg.sub.n)O.sub.3, in which 0.995.ltoreq.k.ltoreq.1.015, 0.ltoreq.h.ltoreq.0.03, 0.ltoreq.i.ltoreq.0.03, 0.015.ltoreq.m.ltoreq.0.035, 0.ltoreq.y<0.05, 0.ltoreq.j<0.05, 0.ltoreq.(y+j)<0.05, and 0.015.ltoreq.n.ltoreq.0.035, the Ba being partly replaced with Gd, and the Ti being partly replaced with Mg; providing an additive containing Ma which is at least one of Ba, Sr, and Ca, Mb which is at least one of Mn and Ni, and Mc which is Si or both Si and Ti; mixing the reaction product, Ma, Mb, and Mc so that a positive amount which is less than 1.5 moles of Ma is contained with respect to 100 moles of the reaction product, a positive amount which is less than 1.0 mole of Mb is contained with respect to 100 moles of the reaction product, and 0.5 to 2.0 moles of Mc is contained with respect to 100 moles of the reaction product; firing the resulting mixture.

18. The method for manufacturing a dielectric ceramic, according to claim 17, wherein, prior to firing a positive amount which is 0.5 moles or less of R.sub.2O.sub.3 in which R is at least one lanthanoid element other than Gd, Y, and Sc is mixed as a subcomponent with respect to 100 moles of the reaction product.

19. The method for manufacturing a dielectric ceramic, according to claim 18, wherein, prior to firing, a positive amount which is 1 mole or less of Al.sub.2O.sub.3 is further mixed with respect to 100 moles of the reaction product.

20. The method for manufacturing a dielectric ceramic, according to claim 17, wherein, prior to firing, a positive amount which is 1 mole or less of Al.sub.2O.sub.3 is further mixed with respect to 100 moles of the reaction product.

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TECHNICAL FIELD

The present invention relates to a dielectric ceramic, a manufacturing method thereof, and a multilayer ceramic capacitor formed of this dielectric ceramic. In particular, the present invention relates to improvements in the dielectric constant of a dielectric ceramic, in the temperature characteristics of the dielectric constant of a dielectric ceramic layer which is formed of the above dielectric ceramic and which forms a multilayer ceramic capacitor, and in the reliability thereof.

BACKGROUND ART

A multilayer ceramic capacitor is generally formed as described below.

First, ceramic green sheets are prepared, each having a conductive material on a surface thereof to be formed into an interior electrode which has a desired pattern, and each containing a powdered dielectric ceramic starting material. As the dielectric ceramic, for example, a ceramic primarily composed of BaTiO.sub.3 is used.

Next, ceramic green sheets including the above-described ceramic green sheets provided with the conductive material are laminated to each other and are then thermally bonded to each other, thereby forming an integrated green laminate.

Next, this green laminate is fired, thereby obtaining a sintered laminate. Inside this laminate, the interior electrodes are formed using the conductive material described above.

Subsequently, on exterior surfaces of the laminate, exterior electrodes are formed to be electrically connected to specified interior electrodes. The exterior electrodes are each formed, for example, by applying a conductive paste containing a powdered conductive metal and a glass frit onto the exterior surfaces of the laminate, followed by baking.

As described above, the multilayer capacitor is formed.

In order to reduce the cost for manufacturing a multilayer ceramic capacitor as low as possible, a relatively inexpensive base metal such as nickel or copper has been frequently used in recent years as the conductive material described above for forming the interior electrodes. When a multilayer ceramic capacitor having interior electrodes made of a base metal is manufactured, firing must be performed in a neutral or a reducing atmosphere in order to prevent the base metal from being oxidized in firing.

However, by firing in a neutral or a reducing atmosphere, in general, a ceramic composed, for example, of barium titanate is extremely reduced, and as a result, a problem may arise in that the ceramic becomes semiconductive.

For solving the problem described above, in order to prevent dielectric ceramic materials from being reduced, various techniques have been proposed (for example, see Japanese Unexamined Patent Application Publication Nos. 8-8137, 2001-97772, 2001-97773, 5-217793, 5-217794, 4-25005, and 11-278930). According to the reduction-preventing techniques of a dielectric ceramic material as mentioned above, manufacturing of a multilayer ceramic capacitor using nickel or the like as an interior electrode material can be performed.

In recent years, techniques for forming electronic circuits having a higher density have significantly advanced. Accordingly, a multilayer ceramic capacitor used for the electronic circuits as described above has been increasingly required to be miniaturized and to have a larger capacity. In addition, a multilayer ceramic capacitor may be used in some cases to isolate or buffer an electric source of a microprocessor which is operated at a high speed, and in this case, since an active electron element generates a large amount of heat while being operated at a high speed, a multilayer ceramic capacitor used around a microprocessor is required to have superior reliability in a high-temperature atmosphere.

Accordingly, even when the thickness of a dielectric ceramic layer forming a multilayer ceramic capacitor can be decreased, it has been desired that a dielectric ceramic material be realized which has a low dielectric loss, superior electrical insulating properties, and high reliability.

Although the dielectric ceramic materials disclosed in Japanese Unexamined Patent Application Publication Nos. 8-8137, 2001-97772, and 2001-97773 have a high relative dielectric constant, crystal grains in the ceramic are grown larger, and when the thickness of a dielectric ceramic layer is decreased, for example, to 3 .mu.m or less, the number of crystal grains present in one dielectric ceramic layer is decreased, and as a result, a problem of degradation in reliability occurs.

Since the dielectric ceramic materials disclosed in Japanese Unexamined Patent Application Publication Nos. 5-217793, 5-217794, and 4-25005 use Ba--Si--Li or Ba--Si--B as a sintering auxiliary agent, problems may arise in that the properties of the dielectric ceramic material largely varies depending on firing conditions and in that the reliability in a high-temperature and high-humidity atmosphere is degraded.

According to the dielectric ceramic material disclosed in Japanese Unexamined Patent Application Publication No. 11-278930, a rare earth element which is added thereto is allowed to be primarily present in crystal grain boundaries so that the reliability by a high-temperature loading test is improved and, in addition, so that a higher relative dielectric constant is obtained. However, according to this dielectric ceramic material disclosed in Japanese Unexamined Patent Application Publication No. 11-278930, as are the materials disclosed in Japanese Unexamined Patent Application Publication Nos. 8-8137, 2001-97772, and 2001-97773, since crystal grains in the ceramic grow large, when the thickness of the dielectric ceramic layer is decreased, for example, to 3 .mu.m or less, the number of crystal grains present in one dielectric ceramic layer is decreased, and as a result, a problem of degradation in reliability occurs.

Hence, an object of the present invention is to provide a dielectric ceramic capable of satisfying the desires described above while the above-described problems are dissolved and to provide a manufacturing method thereof.

Another object of the present invention is to provide a multilayer ceramic capacitor formed using the above-described dielectric ceramic.

DISCLOSURE OF INVENTION

The inventors of the present invention found that when Gd, which is a rare earth element, replaces a part of Ba forming a barium titanate composite oxide and is contained as a solid solution in crystal grains, although the thickness of a dielectric ceramic layer of a multilayer ceramic capacitor is decreased, for example, to 3 .mu.m or less, the reliability under high-temperature loading conditions is improved, and as a result, the present invention was finally made.

In order to solve the technical problems described above, a dielectric ceramic of the present invention comprises a primary component composed of a barium titanate base composite oxide represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.s- ub.yHf.sub.jMg.sub.n)O.sub.3, in which 0.995.ltoreq.k.ltoreq.1.015, 0.ltoreq.h.ltoreq.0.03, 0.ltoreq.i.ltoreq.0.03, 0.015.ltoreq.m.ltoreq.0.035, 0.ltoreq.y<0.05, 0.ltoreq.j<0.05, 0.ltoreq.(y+j)<0.05, and 0.015.ltoreq.n.ltoreq.0.035 hold, Ba is partly replaced with Gd, and Ti is partly replaced with Mg; and an additive component containing Ma (Ma is at least one of Ba, Sr, and Ca), Mb (Mb is at least one of Mn and Ni), and Mc (Mc is Si or includes both Si and Ti), in which Ma is contained in an amount of less than 1.5 moles (however, 0 moles are not included) with respect to 100 moles of the primary component, Mb is contained in an amount of less than 1.0 mole (however, 0 moles are not included) with respect to 100 moles of the primary component, and Mc is contained in an amount in the range of from 0.5 to 2.0 moles with respect to 100 moles of the primary component.

In the dielectric ceramic of the present invention, it is important that the primary component is represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.sub.yHf.s- ub.jMg.sub.n)O.sub.3. That is, it is important that Gd and Mg are not simply contained as an additive component, Gd replaces a part of Ba and is contained as a solid solution in the primary component, and Mg replaces a part of Ti and is contained as a solid solution in the primary component. For example, when a material containing a calcined BaTiO.sub.3 base compound and Gd and/or Mg simply added thereto is fired, it has been already known that Gd in a solid solution form cannot be sufficiently present at Ba sites, and that Mg in a solid solution form cannot be sufficiently present at Ti sites.

The dielectric ceramic according to the present invention preferably further comprises, with respect to 100 moles of the primary component, 0.5 moles or less of R.sub.2O.sub.3 (R is at least one of a lanthanoid element except Gd, Y, and Sc) as a subcomponent.

In addition, the dielectric ceramic according to the present invention preferably further comprises, with respect to 100 moles of the primary component, 1 mole of less of Al.sub.2O.sub.3.

The present invention may also be applied to a method for manufacturing the dielectric ceramic as described above.

First, a method for manufacturing a dielectric ceramic, according to the present invention, comprises a first step of obtaining a reaction product composed of a barium titanate base composite oxide represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.sub.yHf.s- ub.jMg.sub.n)O.sub.3, in which 0.995.ltoreq.k.ltoreq.1.015, 0.ltoreq.h.ltoreq.0.03, 0.015.ltoreq.i.ltoreq.0.03, 0.015.ltoreq.m.ltoreq.0.035, 0.ltoreq.y<0.05, 0.ltoreq.j<0.05, 0.ltoreq.(y+j)<0.05, and 0.015.ltoreq.n.ltoreq.0.035, Ba being partly replaced with Gd, and Ti being partly replaced with Mg.

In addition, a step of preparing Ma (Ma is at least one of Ba, Sr, and Ca), Mb (Mb is at least one of Mn and Ni), and Mc (Mc is Si or includes both Si and Ti) is performed.

Subsequently, a third step of mixing the reaction product obtained in the first step and Ma, Mb, and Mc prepared in a second step is carried out so that less than 1.5 moles of Ma (however, 0 moles are not included) is contained with respect to 100 moles of the reaction product, less than 1.0 mole of Mb (however, 0 moles are not included) is contained with respect to 100 moles of the reaction product, and 0.5 to 2.0 moles of Mc is contained with respect to 100 moles of the reaction product.

Next, a fourth step of firing the mixture obtained in the third step is performed.

In the method for manufacturing a dielectric ceramic, according to the present invention, in the third step described above, 0.5 moles or less of R.sub.2O.sub.3 (R is at least one of a lanthanoid element except Gd, Y, and Sc) is preferably further mixed as a subcomponent with respect to 100 moles of the reaction product.

In addition, in the method for manufacturing a dielectric ceramic, according to the present invention, 1 mole or less of Al.sub.2O.sub.3 is preferably further mixed with respect to 100 moles of the reaction product in the third step described above.

The present invention may be further applied to a multilayer ceramic capacitor which comprises: a laminate having dielectric ceramic layers which are laminated to each other and interior electrodes which are provided along specific interfaces between dielectric ceramic layers and which are overlapped with each other in the lamination direction; and exterior electrodes formed on exterior surfaces of the laminate so as to be electrically connected to specific interior electrodes.

In the multilayer ceramic capacitor according to the present invention, the dielectric ceramic layers described above each comprise the dielectric ceramic according to the present invention, and the interior electrodes each comprise a base metal as a primary component.

According to the dielectric ceramic of the present invention as described above, when a dielectric ceramic layer for forming a multilayer ceramic capacitor is formed therefrom, since sintering stability is superior, the humidity resistance is improved, the F characteristics of the JIS standard and the Y5V characteristics of the EIA standard are satisfied, the relative dielectric constant is 9,000 or more, and the multilayer ceramic capacitor can be used in a wide temperature range.

In addition, since the humidity resistance and the high-temperature reliability are superior although the thickness of the dielectric ceramic layer is decreased, a miniaturized multilayer ceramic capacitor having a larger capacity can be realized by decreasing the thickness, and in addition, it is not necessary to decrease a rated voltage. Accordingly, even when the thickness of the dielectric ceramic layer is decreased, for example, to 3 .mu.m or less, practically sufficient characteristics can be imparted to the multilayer ceramic capacitor.

In addition, even when being fired in a neutral or a reducing atmosphere, the dielectric ceramic of the present invention is not rendered semiconductive and may have a high specific resistance. Accordingly, when a multilayer ceramic capacitor is formed using this dielectric ceramic, a base metal can be used as a conductive component contained in interior electrodes without causing any problems, and as a result, cost of the multilayer ceramic capacitor can be reduced.

When 0.5 moles or less of R.sub.2O.sub.3 (R is at least one of a lanthanoid element except Gd, Y, and Sc) is further contained in the dielectric ceramic according to the present invention as a subcomponent with respect to 100 moles of the primary component, the lifetime under high-temperature loading conditions and/or the sintering properties can be further improved.

In addition, when 1 mole or less of Al.sub.2O.sub.3 is further contained in the dielectric ceramic according to the present invention with respect to 100 moles of the primary component, the sintering properties can be further improved.

According to the method for manufacturing a dielectric ceramic of the present invention, since the reaction product composed of a barium titanate base composite oxide is obtained in which Ba is partly replaced with Gd and Ti is partly replaced with Mg, and the necessary additive components are mixed with this reaction product, as the primary component, a dielectric ceramic can be easily and reliably obtained containing the barium titanate base composite oxide in which Ba is partly replaced with Gd and Ti is partly replaced with Mg.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing a multilayer ceramic capacitor 1 formed using a dielectric ceramic according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, a multilayer ceramic capacitor 1 has a laminate 2 in the form of a rectangular parallelepiped on the whole. The laminate 2 is formed of a plurality of dielectric ceramic layers 3 which are laminated to each other and a plurality of interior electrodes 4 and 5 which are formed along a plurality of specific interfaces between the dielectric ceramic layers 3. The interior electrodes 4 and 5 are formed to extend to exterior surfaces of the laminate 2, and the interior electrodes 4 extending to one end surface 6 of the laminate 2 and the interior electrodes 5 extending to the other end surface 7 are alternately disposed in the laminate 2.

Onto the end surfaces 6 and 7, which are the exterior surfaces of the laminate 2, a conductive paste is applied and is then baked, thereby forming respective exterior electrodes 8 and 9. Whenever necessary, on the exterior electrodes 8 and 9, first plating layers 10 and 11 made of nickel, copper, a nickel-copper alloy, or the like are formed, and on the plating layers thus formed, second plating layers 12 and 13 made of solder, tin, or the like are formed.

As described above, in the multilayer ceramic capacitor 1, the interior electrodes 4 and 5 are formed so as to be overlapped with each other in the lamination direction of the laminate 2, and hence static capacitances are formed between the adjacent interior electrodes 4 and 5. In addition, the interior electrodes 4 are electrically connected to the exterior electrode 8, and in addition, the interior electrodes 5 are also electrically connected to the exterior electrode 9; hence, the static capacitances described above are obtained through those exterior electrodes 8 and 9.

The dielectric ceramic layer 3 is formed from the following dielectric ceramic which is the feature of the present invention.

That is, the dielectric ceramic layer 3 is formed from a dielectric ceramic which comprises a primary component of a barium titanate base composite oxide represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.sub.yHf.s- ub.jMg.sub.n)O.sub.3, in which 0.995.ltoreq.k.ltoreq.1.015, 0.ltoreq.h.ltoreq.0.03, 0.ltoreq.i.ltoreq.0.03, 0.015.ltoreq.m.ltoreq.0.035, 0.ltoreq.y<0.05, 0.ltoreq.j<0.05, 0.ltoreq.(y+j)<0.05, and 0.015.ltoreq.n.ltoreq.0.035 hold, Ba is partly replaced with Gd, and Ti is partly replaced with Mg; and an additive component containing Ma (Ma is at least one of Ba, Sr, and Ca), Mb (Mb is at least one of Mn and Ni), and Mc (Mc is Si or includes both Si and Ti), in which Ma is contained in an amount of less than 1.5 moles (however, 0 moles are not included) with respect to 100 moles of the primary component, Mb is contained in an amount of less than 1.0 mole (however, 0 moles are not included) with respect to 100 moles of the primary component, and Mc is contained in an amount in the range of from 0.5 to 2.0 moles with respect to 100 moles of the primary component.

When the dielectric ceramic layer 3 is formed using the dielectric ceramic as described above, the humidity resistance is improved due to the sintering stability, the F characteristic specified by the JIS standard and the Y5V characteristic specified by the EIA standard are satisfied, the relative dielectric constant .epsilon. is 9,000 or more, and an accelerated lifetime of insulating resistance under high-temperature and high-voltage conditions is increased; hence, even when the thickness of the dielectric ceramic layer is decreased, a compact and large-capacity multilayer ceramic capacitor 1 having superior reliability can be realized. In addition, since this dielectric ceramic can be fired in a neutral or a reducing atmosphere, a base metal such as nickel, a nickel alloy, copper, or a copper alloy can be used as a material for the interior electrodes 4 and 5. In addition, a small amount of a ceramic powder may be added to a metal material forming the interior electrodes 4 and 5.

The dielectric ceramic forming the dielectric ceramic layer 3 preferably further contains 0.5 moles or less of R.sub.2O.sub.3 (R is at least one of a lanthanoid element except Gd, Y, and Sc) as a subcomponent with respect to 100 moles of the above mentioned primary component. Accordingly, the lifetime under high-temperature loading conditions and/or the sintering properties can be further improved.

In addition, the dielectric ceramic forming the dielectric ceramic layer 3 preferably further contains 1.0 mole or less of Al.sub.2O.sub.3 with respect to 100 moles of the primary component. Accordingly, the sintering properties can be further improved.

The composition of the exterior electrodes 8 and 9 is not specifically limited. The exterior electrodes 8 and 9 may be each formed, for example, of a sintered body using one of various conductive metal powders such as silver, palladium, a silver-palladium alloy, copper, and a copper alloy, or may be each formed of a sintered body composed of one of the above-mentioned conductive metal powders and a glass frit such as B.sub.2O.sub.3--Li.sub.2O--SiO.sub.2--BaO, B.sub.2O.sub.3--SiO.sub.2--BaO, Li.sub.2O--SiO.sub.2--BaO, or B.sub.2O.sub.3--SiO.sub.2--ZnO base material. In addition, when the content is small, in addition to the conductive metal powder and the glass frit mentioned above, a ceramic powder may also be added.

Next, while a method for manufacturing the multilayer ceramic capacitor 1 shown in FIG. 1 is described, an embodiment of a manufacturing method of the dielectric ceramic of the present invention will be described.

First, a powdered starting material of the dielectric ceramic forming the dielectric ceramic layer 3 is prepared. The powdered starting material is preferably formed as described below.

That is, a step is first performed for obtaining a reaction product composed of a barium titanate base composite oxide represented by the general formula (Ba.sub.1-h-i-mCa.sub.hSr.sub.iGd.sub.m).sub.k(Ti.sub.1-y-j-nZr.sub.yHf.s- ub.jMg.sub.n)O.sub.3, in which 0.995.ltoreq.k.ltoreq.1.015, 0.ltoreq.h.ltoreq.0.03, 0.ltoreq.i.ltoreq.0.03, 0.015.ltoreq.m.ltoreq.0.035, 0.ltoreq.y<0.05, 0.ltoreq.j<0.05, 0.ltoreq.(y+j)<0.05, and 0.015.ltoreq.n.ltoreq.0.035 hold, Ba is partly replaced with Gd, and Ti is partly replaced with Mg.

In more particular, in order to obtain the reaction product, compounds containing the individual elements included in the above general formula, such as powdered BaCO.sub.3, TiO.sub.2, CaCO.sub.3, SrCO.sub.3, ZrO.sub.2, HfO.sub.2, Gd.sub.2O.sub.3, and MgO, are mixed together so as to have the composition ratios described above and are then calcined in the air, followed by pulverization.

In this step, as the compounds containing the individual elements included in the above general formula, compounds other than the carbonates or oxides mentioned above may also be used in order to obtain the reaction product described above. In addition, besides the calcination method mentioned above as a synthetic method for obtaining the reaction product, an alkoxide method, a coprecipitation method, a hydrothermal synthesis method, and the like may also be used.

In addition, Ma (Ma is at least one of Ba, Sr, and Ca), Mb (Mb is at least one of Mn and Ni), and Mc (Mc is Si or includes both Si and Ti) are prepared. In more particular, powdered BaCO.sub.3, SrCO.sub.3, CaCO.sub.3, MnO, NiO, TiO.sub.2, and SiO.sub.2 are prepared.

Next, Ma, Mb, and Mc described above are mixed with the above reaction product so that a mixture is formed in which less than 1.5 moles (however, 0 moles are not included) of Ma is contained with respect to 100 moles of the reaction product, less than 1.0 moles (however, 0 moles are not included) of Mb is contained with respect to 100 moles of the reaction product, and 0.5 to 2.0 moles of Mc is contained with respect to 100 moles of the reaction product. This mixture is used as the powdered starting material of the dielectric ceramic.

In the above mixing step in which Ma, Mb, and Mc are added, the individual powdered compounds may be separately added, or after at least two types of individual compounds are allowed to react with each other to form a powdered composite oxide, the addition may then be performed. In the latter case, a calcination method in the air may be used for the reaction, and an alkoxide method, a coprecipitation method, a hydrothermal synthesis method, and the like may also be used.

When the powdered starting material is prepared as described above, a dielectric ceramic which satisfies the conditions as described above