JP2004155649A - Dielectric ceramic, method of producing the same, and multilayer ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide dielectric ceramic which is suitable for composing dielectric ceramic layers of a multilayer ceramic capacitor obtained by firing in a reducing atmosphere, and in which temperature dependency on a dielectric constant is not so deteriorated for the thickness even if thin layered, and which has excellent reliability. <P>SOLUTION: The dielectric ceramic has a composition essentially consisting of ABO<SB>3</SB>(A is Ba or the like, and B is Ti or the like), and comprising rare earth elements and Si. At least a part of the rare earth elements and at least a part of the Si are present as composite compounds 22 including rare earth elements and Si, and different from ABO<SB>3</SB>particles 21 as the essential components. Also, the composite compounds 22 have a crystallinity at least in a part thereof. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a dielectric ceramic, a method of manufacturing the same, and a multilayer ceramic capacitor formed by using the dielectric ceramic. In particular, the present invention can advantageously reduce the thickness of a dielectric ceramic layer in a multilayer ceramic capacitor. It is related to the improvement for

  A multilayer ceramic capacitor is generally manufactured as follows.

First, a ceramic green sheet containing a dielectric ceramic raw material having a conductive material serving as an internal electrode provided in a desired pattern on its surface is prepared. As the dielectric ceramic, for example, a ceramic mainly containing BaTiO ₃ is used.

  Next, a plurality of ceramic green sheets including the above-described ceramic green sheet provided with the conductive material are laminated and thermocompression-bonded, thereby producing an integrated raw laminate.

  Next, the green laminate is fired, thereby obtaining a sintered laminate. An internal electrode made of the above-described conductive material is formed inside the laminate.

  Next, external electrodes are formed on the outer surface of the laminate so as to be electrically connected to specific ones of the internal electrodes. The external electrode is formed, for example, by applying a conductive paste containing a conductive metal powder and a glass frit on the outer surface of the laminate and baking the paste.

  Thus, a multilayer capacitor is completed.

  In the past, palladium or a palladium-silver alloy was used as a conductive material for the above-mentioned internal electrodes. Inexpensive base metals are increasingly used. However, when manufacturing a multilayer ceramic capacitor in which an internal electrode is formed with a base metal, firing in a neutral or reducing atmosphere must be applied to prevent oxidation of the base metal during firing. The dielectric ceramic used in the multilayer ceramic capacitor must have reduction resistance.

In the case where the capacitance-temperature characteristics of the multilayer ceramic capacitor are intended to satisfy, for example, the B characteristics of the JIS standard, the dielectric ceramic having reduction resistance as described above includes, for example, BaTiO ₃ as a main component and a rare earth element as the main component. , An oxide of a so-called acceptor element such as Mn, Fe, Ni or Cu, and a sintering aid are used.

  For example, JP-A-5-9066 (Patent Document 1), JP-A-5-9067 (Patent Document 2), JP-A-5-9068 (Patent Document 3), or JP-A-9-270366 (Patent Reference 4) proposes a composition of a dielectric ceramic having a high dielectric constant, a small change in the dielectric constant with temperature, and a long high-temperature load life.

  Further, focusing on the structure and structure of the dielectric ceramic, JP-A-6-5460 (Patent Document 5), JP-A-2001-220224 (Patent Document 6), or JP-A-2001-230149 (Patent Document 7) In (2), a so-called core-shell structured dielectric ceramic has been proposed.

  Further, according to Patent Document 4 described above, it is described that a dielectric ceramic having a higher dielectric constant and better electric insulation can be obtained by controlling the grain boundary structure of the ceramic.

Further, Japanese Patent Application Laid-Open No. 11-1557928 (Patent Document 8) proposes a dielectric ceramic in which a glass component containing SiO ₂ and an oxide of a rare earth element is added to a BaTiO ₃ -based main component. . According to this dielectric ceramic, there are obtained effects that the dielectric constant is high, the insulation resistance is high, the dielectric loss is small, and the reliability in a high-temperature load test is good.
JP-A-5-9066 JP-A-5-9067 JP-A-5-9068 JP-A-9-270366 JP-A-6-5460 JP 2001-220224 A JP 2001-230149 A JP-A No. 11-1557928

  With the development of electronics technology in recent years, the miniaturization of electronic components has been rapidly progressing, and the tendency of multilayer ceramic capacitors to be smaller and have a larger capacity has become remarkable. An effective means for reducing the size and increasing the capacity of the multilayer ceramic capacitor is to reduce the thickness of the dielectric ceramic layer. The thickness of the dielectric ceramic layer has been reduced to 2 μm or less at the commercial level and 1 μm or less at the experimental level.

  Further, in order for the electric circuit to operate stably irrespective of the fluctuation of the temperature, the capacitor used therein must also be stable with respect to the temperature.

  In view of the above, it is strongly desired to realize a multilayer ceramic capacitor having high electrical insulation and excellent reliability even when the capacitance temperature change is small and the dielectric ceramic layer is thinned.

  The dielectric ceramics described in Patent Documents 1, 2 and 3 described above satisfy the X7R characteristic in the EIA standard and exhibit high electrical insulation properties. With respect to the capacitance-temperature characteristics and reliability when the thickness is reduced to 5 μm or less, particularly 3 μm or less, the requirements of the market cannot always be sufficiently satisfied.

Similarly, the dielectric ceramic described in Patent Document 4 also has a problem in that the capacitance-temperature characteristics and the reliability deteriorate as the dielectric ceramic layer becomes thinner. Further, in the dielectric ceramic described in Patent Document 4, since an additive to be added to a main component such as BaTiO ₃ needs to be melted in a firing process, the reaction between the main component and the additive is easy to proceed, In particular, there is a problem that the capacitance-temperature characteristics when the dielectric ceramic layer is thinned deteriorate.

  Further, the so-called core-shell type dielectric ceramics described in Patent Documents 5, 6, and 7 also have a problem that the capacitance-temperature characteristics and reliability deteriorate as the dielectric ceramic layers are made thinner.

Further, in the dielectric ceramic described in Patent Document 8, since the BaTiO ₃ -based main component contains SiO ₂ and an oxide of a rare earth element in a glassy state, when the dielectric ceramic layer is thinned, As for the reliability of the product, it cannot always satisfy the market requirements.

  From the above, if the dielectric ceramic layer is thinned for the purpose of responding to the miniaturization and large capacity of the multilayer ceramic capacitor, if the AC signal level is the same as before the thinning, Since the electric field intensity applied to one dielectric ceramic layer is increased, the capacitance-temperature characteristics are significantly reduced. Also, regarding the reliability, when the dielectric ceramic layer is thinned, if the DC rated voltage is the same as before thinning, the electric field intensity applied per one dielectric ceramic layer increases. , Which is significantly reduced.

  Therefore, even though the dielectric ceramic layer is made thinner, it is desired to realize a multilayer ceramic capacitor which does not worsen the temperature dependency of the dielectric constant as thinner as possible and has excellent reliability. .

  An object of the present invention is to provide a dielectric ceramic, a method for manufacturing the same, and a multilayer ceramic capacitor constituted by using the dielectric ceramic, which can satisfy the above-mentioned demands.

The dielectric ceramic according to the present invention is characterized in that ABO ₃ (A is Ba or Ba and at least one of Ca and Sr partially substituted, and B is Ti or Ti and partially substituted thereof. And a rare-earth element and Si as a main component, characterized by having the following configuration.

  That is, at least a part of the rare earth element and at least a part of the Si exist as a composite compound containing the rare earth element and Si and different from the main component described above, and the composite compound has at least a part thereof. Is characterized by having crystallinity.

  The dielectric ceramic according to the present invention may further include at least one of Mn, Ni, Fe, Cu, Mg, Al and Cr as so-called acceptor elements.

  Further, the dielectric ceramic according to the present invention may further include a sintering aid containing at least one of Si, B and Li.

  The invention is also directed to a method for producing a dielectric ceramic as described above.

The method for producing a dielectric ceramic according to the present invention is characterized in that ABO ₃ (A is at least one of Ba or Ba and partially substituted Ca and Sr, and B is Ti or Ti and one of them. Part of which is at least one of Zr and Hf substituted), and a step of reacting at least a rare earth element with Si, thereby forming a reactant having crystallinity in a part thereof. And mixing the ABO ₃ and the reactant to form a raw material powder and firing the raw material powder.

  In the step of preparing the above-mentioned raw material powder, if necessary, a compound containing at least one of Mn, Ni, Fe, Cu, Mg, Al and Cr as an acceptor element, and at least one of Si, B and Li are used. The sintering aid may be further mixed with at least one of the compounds containing a rare earth element.

  The present invention is further directed to a multilayer ceramic capacitor formed using the above-described dielectric ceramic.

  The multilayer ceramic capacitor according to the present invention includes a multilayer body including a plurality of stacked dielectric ceramic layers and an internal electrode formed along a specific interface between the dielectric ceramic layers. And an external electrode formed on the outer surface of the laminate so as to be electrically connected, wherein the dielectric ceramic layer is made of the dielectric ceramic as described above.

  As described above, according to the dielectric ceramic of the present invention, the rare earth element and Si exist as a composite compound containing the rare earth element and Si, and the composite compound has crystallinity in at least a part thereof. Therefore, when the dielectric ceramic layer of the multilayer ceramic capacitor is formed with this, even if the dielectric ceramic layer is made thinner, the temperature dependency of the dielectric constant does not deteriorate as much as the thickness becomes thinner. Excellent.

  Therefore, if the dielectric ceramic layer of the multilayer ceramic capacitor is formed using the dielectric ceramic, the multilayer ceramic capacitor can be reduced in size and thickness by reducing the thickness of the dielectric ceramic layer while maintaining good capacitance temperature characteristics and reliability. Large capacity can be achieved. In particular, according to the dielectric ceramic according to the present invention, the thickness of the dielectric ceramic layer can be reduced to about 0.5 μm without any problem.

  FIG. 1 is a sectional view schematically showing a multilayer ceramic capacitor 1 according to one embodiment of the present invention.

  The multilayer ceramic capacitor 1 includes a multilayer body 2. The laminate 2 includes a plurality of dielectric ceramic layers 3 to be laminated, and a plurality of internal electrodes 4 and 5 respectively formed along a plurality of specific interfaces between the plurality of dielectric ceramic layers 3. You. The internal electrodes 4 and 5 are formed so as to reach the outer surface of the multilayer body 2. The internal electrodes 4 are extended to one end face 6 of the multilayer body 2 and the internal electrodes are extended to the other end face 7. 5 are alternately arranged inside the laminate 2.

  External electrodes 8 and 9 are formed on the outer surface of the laminate 2 and on the end faces 6 and 7, respectively. First plating layers 10 and 11 made of nickel, copper, or the like are formed on external electrodes 8 and 9, respectively, and second plating layers 12 and 13 made of solder, tin, or the like are further formed thereon. Are formed respectively.

In such a multilayer ceramic capacitor 1, the dielectric ceramic layer 3 is made of ABO ₃ (A is Ba or Ba and at least one of Ca and Sr partially substituted, and B is Ti or And at least one of Zr and Hf partially substituted with Ti)) and a dielectric ceramic further containing a rare earth element and Si.

  In this dielectric ceramic, at least a part of the rare earth element and at least a part of Si exist as a composite compound different from the main component, including the rare earth element and Si, and the composite compound has at least It is characterized by having crystallinity in part.

In general, a dielectric ceramic composed mainly of ABO ₃ , particularly BaTiO _3, to which some additive is added, has a large temperature dependence of the dielectric constant when the additive is dissolved. . Therefore, when a multilayer ceramic capacitor is manufactured using such a dielectric ceramic, the multilayer ceramic capacitor has poor capacitance-temperature characteristics.

In recent years, rare earth elements have been frequently used as the additional components. When a rare earth element is added to BaTiO ₃ , for example, it easily forms a solid solution, so that the dielectric constant of such a dielectric ceramic has poor temperature dependence. It is also known that when the rare earth element is present alone as an oxide, the reliability is reduced.

Therefore, the present inventor has repeatedly conducted investigations and experiments. As a result, by adding a rare earth element as a crystalline reactant with Si, the compound containing the rare earth element and Si was converted into a dielectric material containing ABO ₃ as a main component. They have been found to be present in ceramics and suppress the solid solution of rare earth elements into ABO ₃ . At this time, it was found that the reaction product of the rare earth element and Si did not need to be 100% crystalline, and it was sufficient that at least part of the reactant had crystallinity. In addition, it was also found that the rare earth element does not decrease the reliability of the dielectric ceramic if it is present not alone but in a compound with Si.

For this reason, as described above, a main component containing ABO ₃ as a main component, further containing a rare earth element and Si, and at least a part of the rare earth element and at least a part of Si containing the rare earth element and Si. The dielectric ceramic layer 3 shown in FIG. 1 is constituted by such a dielectric ceramic which is present as a composite compound different from the component, and the composite compound has crystallinity at least in part. For example, even if the dielectric ceramic layer 3 is made thinner, the temperature dependency of the dielectric constant does not deteriorate as the thickness becomes thinner, and the reliability can be improved. Therefore, the multilayer ceramic capacitor 1 including the dielectric ceramic layer 3 made of such a dielectric ceramic can have excellent capacitance temperature characteristics and excellent reliability.

FIG. 2 schematically shows the structure of the above-described dielectric ceramic. The dielectric ceramic has ABO ₃ particles 21. In addition, in the dielectric ceramic, apart from the ABO ₃ particles 21, a composite compound 22 containing a rare earth element and Si exists.

In the above-mentioned ABO ₃ particles 21, a rare earth element and an additive component such as Si may be partially dissolved. Further, the composite compound 22 may include an element other than the rare earth element and Si.

  The dielectric ceramic may further include at least one of Mn, Ni, Fe, Cu, Mg, Al and Cr as a so-called acceptor element.

  In addition, the dielectric ceramic may further include a sintering aid containing at least one of Si, B, and Li.

  The internal electrodes 4 and 5 contain, for example, a base metal such as nickel, a nickel alloy, copper or a copper alloy as a conductive component.

  Further, the external electrodes 8 and 9 are constituted by a sintered layer of a conductive metal powder or a sintered layer of a conductive metal powder to which glass frit is added.

  Next, a method of manufacturing the multilayer ceramic capacitor 1 will be described.

First, in order to produce a raw material powder of the dielectric ceramic constituting the dielectric ceramic layer 3, a step of producing ABO ₃ and reacting at least a rare earth element with Si, thereby having a part in crystallinity And a step of preparing a reactant are respectively performed.

In producing the above-mentioned ABO ₃ , a compound containing each of A and B is mixed at a desired ratio, for example, heat-treated, thereby synthesizing ABO ₃ , and pulverizing the ABO ₃ to obtain an ABO ₃ powder. To be made.

On the other hand, in producing a reactant containing a rare earth element and SiO ₂ , a compound containing a desired rare earth element and Si is mixed, and the mixture is subjected to, for example, a heat treatment to thereby prepare a reactant containing the rare earth element and Si. Is obtained and pulverized to produce a reactant powder containing a rare earth element and Si. This reactant may contain rare earth elements such as alkaline earth elements and transition metal elements, and elements other than Si. The average particle size of the reactant powder is preferably smaller than the average particle size of the above-mentioned ABO ₃ powder.

Next, the ABO ₃ powder and the reactant powder are mixed to obtain a dielectric ceramic raw material powder. In the mixing step for obtaining the raw material powder, even if a compound containing at least one of Mn, Ni, Fe, Cu, Mg, Al and Cr as an acceptor element is further mixed, at least one of Si, B and Li A sintering aid containing a seed may be mixed, or a compound containing a rare earth element may be further mixed. Note that the acceptor element is preferably added in advance to the reactant powder. In this case, the acceptor element is present in the composite oxide phase.

  Next, an organic binder and a solvent are added to and mixed with the mixed powder obtained as described above, whereby a slurry is produced. Using this slurry, a ceramic green sheet serving as the dielectric ceramic layer 3 is formed. Molded.

  Next, a conductive paste film to be the internal electrodes 4 or 5 is formed on a specific ceramic green sheet by, for example, screen printing. This conductive paste film contains, for example, nickel, a nickel alloy, copper or a copper alloy as a conductive component. The internal electrodes 4 and 5 may be formed by, for example, a vapor deposition method, a plating method, or the like, in addition to a printing method such as a screen printing method.

  Next, a plurality of ceramic green sheets including the ceramic green sheet on which the conductive paste film is formed as described above are laminated, thermocompression-bonded, and cut as necessary. In this manner, a raw laminate having a structure in which the plurality of ceramic green sheets and the conductive paste films to be the internal electrodes 4 and 5 formed along the specific interfaces between the ceramic green sheets, respectively, are laminated. Is obtained. In this green laminate, the conductive paste film has its edge exposed at any one of the end surfaces.

  Next, the green laminate is fired in a reducing atmosphere. Thereby, the laminated body 2 after sintering as shown in FIG. 1 is obtained. In this laminate 2, the dielectric ceramic layer 3 is constituted by the above-described ceramic green sheets, and the internal electrodes 4 or 5 are constituted by the conductive paste film.

  Next, external electrodes 8 and 9 are formed on end surfaces 6 and 7 of laminated body 2 so as to be electrically connected to the exposed edges of internal electrodes 4 and 5, respectively.

As the material of the external electrodes 8 and 9, it is possible to use the same material as the internal electrodes 4 and 5, silver, palladium, silver - palladium alloy etc. may also be used, also, these metal powders, B ₂ can be used those O ₃ was added -SiO ₂ -BaO-based glass, Li ₂ O-SiO ₂ -BaO-based _{glass, B 2 O 3 -Li 2 O} -SiO 2 -BaO -based glass frit made of glass or the like . An appropriate material is selected in consideration of the application, the place of use, and the like of the multilayer ceramic capacitor 1.

  The external electrodes 8 and 9 are usually formed by applying and baking a paste containing the above-described conductive metal powder on the outer surface of the fired laminate 2. It may be formed by coating on the outer surface of the green laminate and baking simultaneously with firing for obtaining the laminate 2.

  Thereafter, plating of nickel, copper, or the like is performed on the external electrodes 8 and 9 to form first plating layers 10 and 11. Then, plating of solder, tin or the like is performed on the first plating layers 10 and 11 to form second plating layers 12 and 13. The formation of a conductor layer such as the plating layers 10 to 13 on the external electrodes 8 and 9 may be omitted depending on the use of the multilayer ceramic capacitor 1.

  As described above, the multilayer ceramic capacitor 1 is completed.

In the multilayer ceramic capacitor 1 thus obtained, the dielectric ceramic constituting the dielectric ceramic layer 3 is, as shown in FIG. 2, in addition to the ABO ₃ particles 21, at least a part of a rare earth element and Si. It has a structure in which at least a part thereof exists as the composite compound 22. Although a part of the reaction product of the rare earth element and Si may be dissolved in the ABO ₃ particles 21, it is preferable that 30% or more of the total amount of the rare earth element is present as the composite compound 22 of the rare earth element and Si. . More preferably, 50% or more of the rare earth element and Si are present as the composite compound 22.

The average particle diameter (average primary particle) of the ABO ₃ particles 21 as the main component is in the range of 0.05 to 0.7 μm in order to cope with the thinning of the dielectric ceramic layer 3. Is preferred. As described above, by mainly including the ABO ₃ particles 21 having an average particle diameter of 0.05 to 0.7 μm, the dielectric ceramic layer 3 can be thinned to a thickness of about 0.5 μm without any problem. Can be. Further, the ratio of the composite compound 22 is preferably 0.01 mol or more and 25 mol or less with respect to 100 mol of the main component. More preferably, it is 0.1 mol or more and 5 mol or less.

  It should be noted that Al, Zr, Fe, Hf, Na, N, and the like may be mixed as impurities at any stage of the production of the raw material powder of the dielectric ceramic and the other manufacturing steps of the multilayer ceramic capacitor 1. The mixing of these impurities does not cause a problem on the electrical characteristics of the multilayer ceramic capacitor 1.

  Further, at any stage of the manufacturing process of the multilayer ceramic capacitor 1, there is a possibility that Fe or the like may be mixed into the internal electrodes 4 and 5 as an impurity. Never.

  Next, an experimental example performed for confirming the effect of the present invention will be described.

1. Experimental example 1
In Experimental Example 1, samples according to Examples 1 and 2 and Comparative Examples 1-1, 1-2, and 2 as described below were produced.

(Example 1)
In Example 1, (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ was used as ABO ₃ , and Y ₂ O ₃ , MgO, MnO ₂ and SiO ₂ were used as additional components.

First, BaCO ₃ , CaCO ₃ , TiO ₂ and ZrO ₂ are prepared as starting materials of the main components, and these are weighed so as to have a composition of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ . Next, these were mixed by a ball mill and heat-treated at a temperature of 1150 ° C. to synthesize (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , which was pulverized.

On the other hand, Y ₂ O ₃ and SiO ₂ as additive components were weighed so as to have a molar ratio of 1: 2, and then mixed by a ball mill and heat-treated at a temperature of 1000 ° C. to obtain YO _3/2 A SiO ₂ -based reactant was obtained and pulverized.

Next, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, and 0.1 moles of MgO. 5 mol of MnO ₂ was mixed to obtain a mixed powder to be a raw material powder of the dielectric ceramic.

  Next, a ceramic slurry was prepared by adding a polyvinyl butyral-based binder and an organic solvent such as ethanol to the mixed powder and performing wet mixing using a ball mill.

  Next, the ceramic slurry was formed into a sheet shape by a doctor blade method so that the thickness of the fired dielectric ceramic layer became 1.5 μm, to obtain a rectangular ceramic green sheet.

  Next, a conductive paste containing nickel as a conductive component was screen-printed on the ceramic green sheet to form a conductive paste film to be an internal electrode.

  Next, a plurality of ceramic green sheets including a ceramic green sheet on which the conductive paste film was formed were laminated so that the side from which the conductive paste film was drawn out was alternated, to obtain a raw laminate.

Next, the raw laminate is heated to a temperature of 350 ° C. in a nitrogen atmosphere to burn the binder, and then a reducing agent comprising an H ₂ —N ₂ —H ₂ O gas having an oxygen partial pressure of 10 ⁻¹⁰ MPa is used. It was fired at 1200 ° C. for 2 hours in an atmosphere to obtain a sintered laminate.

Next, a conductive paste containing B ₂ O ₃ —Li ₂ O—SiO ₂ —BaO-based glass frit and containing copper as a conductive component is applied on both end surfaces of the laminate, and heated at 700 ° C. in a nitrogen atmosphere. Baking was performed at a temperature to form an external electrode electrically connected to the internal electrode.

The external dimensions of the multilayer ceramic capacitor thus obtained are 1.6 mm in width, 3.2 mm in length, and 1.2 mm in thickness. The thickness of the dielectric ceramic layer interposed between the internal electrodes is 1. It was 5 μm. The number of effective dielectric ceramic layers was 100, and the counter electrode area per layer was 2.1 mm ² .

(Comparative Example 1-1)
Comparative Example 1-1 has the same composition as Example 1, _except that 100 mol of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ is _added to 1.0 mol of Y ₂ O ₃ , 2.0 mol Of SiO ₂ , 0.5 mol of MgO and 0.5 mol of MnO ₂ at a time to obtain a mixed powder to be a raw material powder of the dielectric ceramic.

  Thereafter, using the mixed powder, a multilayer ceramic capacitor was manufactured through the same operation as in Example 1.

(Comparative Example 1-2)
Comparative Example 1-2 has the same composition as that of Example 1, except that Y ₂ O ₃ and SiO ₂ are replaced with 1 instead of the YO _3/2 —SiO ₂ -based reactant as an additional component in Example 1. : Weighed so as to have a molar ratio of 2: 2, mixed by a ball mill, melted at a temperature of 1500 ° C, then poured the melt into water to produce a glass cullet, and crushed the glass cullet. A mixed powder to be a raw material powder of a dielectric ceramic was obtained and a multilayer ceramic capacitor was produced in the same manner as in Example 1 except that the obtained material was used as an additive component.

  In addition, it was confirmed by XRD that the above-mentioned additive components used in Comparative Example 1-2 were not crystalline.

(Example 2)
In Example 2, Ba (Ti _0.85 Zr _0.15 ) O ₃ was used as ABO ₃ , and Gd ₂ O ₃ , MgO, MnO ₂ and SiO ₂ were used as additive components.

First, BaCO ₃ , TiO _2, and ZrO ₂ are prepared as starting materials of the main components, and they are weighed so as to have a composition of Ba (Ti _0.85 Zr _0.15 ) O ₃ , and then mixed by a ball mill. By heat treatment at a temperature of 1150 ° C., Ba (Ti _0.85 Zr _0.15 ) O ₃ was synthesized and pulverized.

On the other hand, Gd ₂ O ₃ , SiO ₂ and MnO ₂ were weighed as additive components in a molar ratio of 0.5: 1: 1, and then mixed by a ball mill and heat-treated at a temperature of 1000 ° C. As a result, a GdO _3/2 —SiO ₂ —MnO ₂ system reactant was obtained.

Next, 100 moles of Ba (Ti _0.85 Zr _0.15 ) O ₃ , 1.0 mole of a GdO _3/2 —SiO ₂ —MnO ₂ system reactant, 10 moles of MgO, and 7.5 moles of Gd ₂ By mixing with O ₃ , a mixed powder to be a raw material powder of the dielectric ceramic was obtained.

  Thereafter, using the mixed powder, a multilayer ceramic capacitor was manufactured through the same operation as in Example 1.

(Comparative Example 2)
Comparative Example 2 has the same composition as that of Example 2, in which 100 mol of Ba (Ti _0.85 Zr _0.15 ) O ₃ , 8 mol of Gd ₂ O ₃ , 1.0 mol of SiO ₂ , and 10 mol of By mixing MgO and 1.0 mol of MnO ₂ at a time, a mixed powder to be a raw material powder of the dielectric ceramic was obtained.

  Thereafter, using the mixed powder, a multilayer ceramic capacitor was manufactured through the same operation as in Example 1.

[Evaluation]
The multilayer ceramic capacitors according to Examples 1 and 2 and Comparative Examples 1-1, 1-2, and 2 obtained as described above were evaluated as follows.

  First, the structure of the ceramic constituting the dielectric ceramic layer included in the multilayer ceramic capacitor was observed and analyzed using WDX and TEM-EDX to confirm the presence or absence of a compound containing a rare earth element and Si. In addition, with respect to a sample in which the presence of this compound was confirmed, it was confirmed whether or not the compound containing the rare earth element and Si was crystalline by TEM electron diffraction and XRD.

Further, the dielectric constant of the dielectric ceramic layer included in the multilayer ceramic capacitor according to each sample at room temperature (25 ° C.) was measured under the conditions of 1 kHz and 1 V _rms .

  Further, the change rate of the capacitance with respect to the temperature change was obtained. The rate of change of the capacitance with respect to this temperature change is based on the rate of change at −25 ° C. and the rate of change at 85 ° C. based on the capacitance at 20 ° C., and the rate of change at 25 ° C. The rate of change at -55 ° C and the rate of change at 125 ° C were evaluated.

  In addition, a high temperature load test was performed. In the high-temperature load test, a voltage of 12 V was applied to 100 samples at a temperature of 125 ° C. so that the electric field intensity became 8 kV / mm, and the change with time of the insulation resistance was obtained. By the time the sample became 200 kΩ or less, it was determined to be defective, and the number of defective samples was determined.

  In addition, a humidity resistance high temperature load test was performed. In the humidity resistance high temperature load test, a voltage of 6 V was applied to 100 samples at a temperature of 85 ° C. and a humidity of 95% so that the electric field strength was 4 kV / mm, and the change with time of the insulation resistance was obtained. Samples having a value of 200 kΩ or less before the elapse of 1000 hours were determined to be defective, and the number of defective samples was determined.

  Table 1 shows the above evaluation results.

  As shown in Table 1, in Examples 1 and 2, the presence of a compound containing a rare earth element and Si was confirmed in the dielectric ceramic constituting the dielectric ceramic layer. In Example 1, the presence of a crystalline compound composed of Y-Si-O was confirmed, and in Example 2, the presence of a crystalline compound composed of Gd-Si-Mn-O was confirmed. Further, according to Examples 1 and 2, it was found that the capacitance-temperature characteristics satisfied the B characteristics of the JIS standard and the X7R characteristics of the EIA standard, and that the reliability was good in the high-temperature load test.

  On the other hand, in Comparative Example 1-1, unlike the case of Example 1, the presence of a compound containing Y and Si was not confirmed in the dielectric ceramic constituting the dielectric ceramic layer. It was confirmed that Si was dissolved in the main component. Therefore, according to Comparative Example 1-1, the capacitance-temperature characteristics were inferior to Example 1.

  Further, in Comparative Example 1-2, unlike the case of Example 1, the presence of a compound containing Y and Si was not confirmed in the dielectric ceramic constituting the dielectric ceramic layer. This is presumed to be because the glass-added component is different from the crystalline additive component observed in Example 1 in that the reaction with the main component easily proceeds. Therefore, as in the case of Comparative Example 2 described later, Comparative Example 1-2 was inferior to Example 1 in the capacity-temperature characteristics. Further, in Comparative Example 1-2, a failure occurred in the moisture resistance and high temperature load test. This is considered to be because glass generally has low moisture resistance, and in Comparative Example 1-2, the additive component is added as glass.

  Further, in Comparative Example 2, unlike the case of Example 2, the presence of a compound containing Gd and Si was not confirmed in the dielectric ceramic constituting the dielectric ceramic layer, and the compound of Gd alone was present. I was just there. In addition, in Comparative Example 2, since the compound of Gd alone was present, the capacity-temperature characteristics were relatively good, but the reliability in the high-temperature load test was inferior to Example 2.

2. Experimental example 2
In Experimental Example 2, the following samples according to Examples 3 to 16 using elements other than Y as the rare earth element were produced.

(Example 3)
Example 1 was repeated except that La ₂ O ₃ was used instead of Y ₂ O ₃ and a LaO _3/2 -SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 3 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 4)
Example 1 was the same as Example 1 except that CeO ₂ was used instead of Y ₂ O ₃ as the compound containing a rare earth element, and a CeO ₂ —SiO ₂ -based reactant was used. Using the raw material composition, a multilayer ceramic capacitor according to Example 4 was produced through the same operation.

(Example 5)
Example 1 was repeated _except that Pr ₆ O ₁₁ was used instead of Y ₂ O ₃ and that a PrO _11/6 -SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 5 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 6)
Example 1 was repeated except that Nd ₂ O ₃ was used instead of Y ₂ O ₃ and that a NdO _3/2 —SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 6 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 7)
Example 1 was repeated except that Sm ₂ O ₃ was used instead of Y ₂ O ₃ and a SmO _3/2 -SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 7 was produced using the same raw material composition as in the case and through the same operation.

(Example 8)
Example 1 was repeated except that Eu ₂ O ₃ was used instead of Y ₂ O ₃ as the compound containing a rare earth element, and a EuO _3/2 -SiO ₂ -based reactant was used. A multilayer ceramic capacitor according to Example 8 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 9)
In Example 1, a compound containing a rare earth element, except that using Gd ₂ O ₃ instead of Y ₂ O _3, and was used reactants GdO _3/2 -SiO ₂ system, the Example 1 A multilayer ceramic capacitor according to Example 9 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 10)
In Example 1, a compound containing a rare earth element, except that using a Tb ₄ O ₇ instead of Y ₂ O _3, and was used TBO _7/4 -SiO ₂ based reactants of Example 1 A multilayer ceramic capacitor according to Example 10 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 11)
In Example 1, a compound containing a rare earth element, except that using Dy ₂ O ₃ instead of Y ₂ O _3, and was used reactants DyO _3/2 -SiO ₂ system, the Example 1 A multilayer ceramic capacitor according to Example 11 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 12)
Example 1 was repeated except that Ho ₂ O ₃ was used instead of Y ₂ O ₃ and that a HoO _3/2 -SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 12 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 13)
Example 1 was repeated except that Er ₂ O ₃ was used instead of Y ₂ O ₃ as a compound containing a rare earth element, and an ErO _3/2 -SiO ₂ -based reactant was used. A multilayer ceramic capacitor according to Example 13 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 14)
Example 1 was repeated except that Tm ₂ O ₃ was used in place of Y ₂ O ₃ and a TmO _3/2 -SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 14 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 15)
Example 1 was repeated except that Yb ₂ O ₃ was used instead of Y ₂ O ₃ and a YbO _3/2 —SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 15 was manufactured using the same raw material composition as in the case and through the same operation.

(Example 16)
Example 1 was repeated except that Lu ₂ O ₃ was used instead of Y ₂ O ₃ and a LuO _3/2 —SiO ₂ -based reactant was used as the compound containing a rare earth element. A multilayer ceramic capacitor according to Example 16 was produced using the same raw material composition as in the case and through the same operation.

[Evaluation]
As described above, the same evaluation as in Example 1 was performed on the multilayer ceramic capacitors obtained in Examples 3 to 16. Table 2 shows the results of the evaluation.

  As can be seen from Table 2, almost the same characteristics as in Example 1 were obtained even when a rare earth element other than Y was used as the rare earth element as in Examples 3 to 16.

3. Experimental example 3
In Experimental Example 3, the following samples of Examples 17 to 22 were manufactured using elements other than Mg as the acceptor element contained in the dielectric ceramic.

(Example 17)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of the mixed powder (raw powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of BaTiO ₃ and 2.2 mol of Y—Si—Mg—O (Y ₂ O ₃ : Except that a mixed powder of a mixture of SiO ₂ : MgO = 1: 2: 1), 0.2 mol of NiO and 0.1 mol of Cr ₂ O ₃ was used. Through the same operations as in the case of No. 1, a multilayer ceramic capacitor according to Example 17 was produced.

(Example 18)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of the mixed powder (raw material powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of (Ba _0.98 Sr _0.02 ) TiO ₃ and 1.8 mol of Y—Si—Ni—O (Y ₂ O ₃ : SiO ₂ : NiO = 1: 1: 1) system reactant, 0.3 mol Dy ₂ O ₃ , 0.5 mol CuO, 0.1 mol Al ₂ O Example 18 was obtained through the same operation as in Example 1 except that a mixed powder of ₃ and 0.02 mol of B ₂ O ₃ and 0.1 mol of SiO ₂ was used. Was manufactured.

(Example 19)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of the mixed powder (raw powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of (Ba _0.98 Ca _0.02 ) TiO ₃ and 1.5 mol of Y—Si—Fe—O (Y ₂ O ₃ : SiO ₂ : Fe ₂ O ₃ = 1: 3: 0.5) system reactant, 0.4 mol Ho ₂ O ₃ , 0.3 mol MnO ₂ , 0.1 mol A multilayer ceramic capacitor according to Example 19 was manufactured through the same operation as in Example 1 except that a mixed powder obtained by mixing 5 mol of CuO was used.

(Example 20)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of the mixed powder (raw powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of Ba (Ti _0.95 Hf _0.05 ) O ₃ and 2.4 mol of Y—Si—Cu— O (Y ₂ O ₃ : SiO ₂ : CuO = 1: 1: 0.5) based reactant, 0.2 mol MnO ₂ , 0.1 mol Fe ₂ O ₃ , 0.1 mol A multilayer ceramic capacitor according to Example 20 was produced through the same operation as in Example 1, except that a mixed powder obtained by mixing SiO ₂ was used.

(Example 21)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of a mixed powder (raw powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of (Ba _0.99 Sr _0.01 ) (Ti _0.99 Zr _0.01 ) O ₃ and 1.7 mol of Y -Si-Al-O (Y ₂ O ₃ : SiO ₂ : Al ₂ O ₃ = 1: 3: 1) -based reactant, 0.2 mol of Yb ₂ O ₃ and 0.3 mol of NiO A multilayer ceramic capacitor according to Example 21 was manufactured through the same operation as in Example 1 except that a mixed powder obtained by mixing was used.

(Example 22)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of the mixed powder (raw powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of BaTiO ₃ and 2.6 mol of Y—Si—Cr—O (Y ₂ O ₃ : (SiO ₂ : Cr ₂ O ₃ = 1: 0.5: 0.5) -based reactant, and a mixed powder obtained by mixing 0.05 mol of Lu ₂ O ₃ and 0.2 mol of SiO ₂ . A multilayer ceramic capacitor according to Example 22 was manufactured through the same operation as in Example 1 except for the above.

[Evaluation]
As described above, the multilayer ceramic capacitors obtained in Examples 17 to 22 were evaluated in the same manner as in Example 1. Table 3 shows the evaluation results.

  As can be seen from Table 3, the composite compound containing the rare earth element and Si and having crystallinity further contains elements such as Mn, Ni, Fe, Cu, Al, and Cr (acceptors) as in Examples 17 to 22. Element).

4. Experimental example 4
In Experimental Example 4, the following sample according to Example 23 was prepared in which the content of the composite compound was different from those in Examples 1 to 22 described above.

(Example 23)
In Example 1, 100 moles of (Ba _0.98 Ca _0.02 ) (Ti _0.98 Zr _0.02 ) O ₃ , 2.0 moles of a YO _3/2 —SiO ₂ -based reactant, 0.5 moles of MgO, Instead of the mixed powder (raw powder of dielectric ceramic) mixed with 0.5 mol of MnO ₂ , 100 mol of Ba (Ti _0.8 Zr _0.2 ) O ₃ and 25 mol of Gd—Sm—Si—O ( Gd ₂ O ₃ : Sm ₂ O ₃ : SiO ₂ = 1: 0.15: 0.1) -based reactant, 11 mol of MgO, and 1.5 mol of MnO ₂ are mixed powder. A multilayer ceramic capacitor according to Example 23 was manufactured through the same operation as in Example 1 except for the fact that it was not.

[Evaluation]
As described above, the same evaluation as in Example 1 was performed on the multilayer ceramic capacitor obtained in Example 23. Table 4 shows the evaluation results.

  As can be seen from Table 4, sufficient characteristics can be obtained even when the content of the complex compound, for example, the content of the Gd-Sm-Si-O-based reactant is 25 mol with respect to 100 mol of the main component.

FIG. 1 is a sectional view schematically showing a multilayer ceramic capacitor 1 according to an embodiment of the present invention. FIG. 3 is a diagram schematically showing a structure of a dielectric ceramic according to the present invention.

Explanation of reference numerals

1 multilayer ceramic capacitor 2 laminate 3 dielectric ceramic layers 4 and 5 the internal electrodes 8 and 9 the external electrode 21 ABO ₃ particles 22 complex compound

Claims (6)

ABO ₃ (A is Ba or at least one of Ba and partially substituted Ca and Sr, and B is Ti or at least one of Ti and partially substituted Zr and Hf thereof. Is a dielectric ceramic containing, as a main component and further containing a rare earth element and Si,
At least a part of the rare earth element and at least a part of the Si exist as a composite compound different from the main component, including the rare earth element and the Si, and the composite compound has a crystal in at least a part thereof. A dielectric ceramic characterized by having properties.   The dielectric ceramic according to claim 1, further comprising at least one of Mn, Ni, Fe, Cu, Mg, Al, and Cr.   3. The dielectric ceramic according to claim 1, further comprising a sintering aid containing at least one of Si, B, and Li. ABO ₃ (A is Ba or at least one of Ba and partially substituted Ca and Sr, and B is Ti or at least one of Ti and partially substituted Zr and Hf thereof. ), And
Reacting at least a rare earth element with Si, thereby producing a reactant having crystallinity in a part thereof;
Preparing a raw material powder by mixing the ABO ₃ and the reactant;
And baking the raw material powder.   The step of preparing the raw material powder includes the steps of: adding a compound containing at least one of Mn, Ni, Fe, Cu, Mg, Al, and Cr, a sintering aid containing at least one of Si, B, and Li; and a rare earth element. The method for producing a dielectric ceramic according to claim 4, further comprising a step of further mixing at least one of the compounds to be contained. A laminate including a plurality of laminated dielectric ceramic layers and internal electrodes formed along a specific interface between the dielectric ceramic layers,
An external electrode formed on an outer surface of the laminate so as to be electrically connected to a specific one of the internal electrodes,
A multilayer ceramic capacitor, wherein the dielectric ceramic layer is made of the dielectric ceramic according to any one of claims 1 to 3.

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