JP2007169088A - Sintered compact, ceramic capacitor, and their production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sintered compact with high relative permittivity, a ceramic capacitor using the same, and their production method. <P>SOLUTION: The sintered compact used for the dielectric layer 1 of a ceramic capacitor is produced by adding to a main component comprising barium titanate, the subcomponents including A-site elements comprising Ba and rare earth elements, and B-site elements comprising one or more selected from Ti, Zr, Sn and Hf, and then firing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sintered body suitable for a dielectric layer material of a ceramic capacitor and a method for manufacturing the same, and a ceramic capacitor and a method for manufacturing the same.

Conventionally, in a multilayer ceramic capacitor, barium titanate is often used as a material for the dielectric layer. In addition, Pt or Pb alloy is sometimes used as the material of the internal electrode, but since it is expensive, a relatively inexpensive base metal such as Ni or Ni alloy is often used. For example, see Patent Document 1.
JP 2005-89224 A

  When Ni or Ni alloy is used for the internal electrode, it is necessary to fire in a reducing atmosphere in which Ni or Ni alloy is not oxidized. However, when firing in such a reducing atmosphere, the dielectric layer is reduced and the relative dielectric constant is lowered. For this reason, development of a dielectric material excellent in reduction resistance is required.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a sintered body and a ceramic capacitor having a high relative dielectric constant, and a method for producing them.

  The sintered body of the present invention contains barium titanate as a main component, and as a subcomponent added to the main component, an A site element containing Ba and rare earth elements, and Ti, Zr, Sn, Hf 1 And a B-site element containing an element of a seed or more.

  The ceramic capacitor of the present invention is characterized by comprising a plurality of electrodes and a dielectric layer provided between the electrodes and including the above-mentioned main component and subcomponent.

  Further, the method for producing a sintered body of the present invention includes a barium titanate, a Ba compound, a rare earth element compound, and one or more elements selected from Ti, Zr, Sn, and Hf as raw materials of the accessory component. It is characterized by adding this compound and firing it in a reducing atmosphere.

  Further, the method for producing a ceramic capacitor of the present invention comprises a barium titanate containing Ba compound, a rare earth element compound, and one or more elements selected from Ti, Zr, Sn, and Hf as raw materials of subcomponents. It is characterized by comprising a step of forming a sheet-like dielectric layer using a compound to which a compound is added, and a step of laminating these by interposing electrodes between a plurality of dielectric layers.

  According to the sintered body of the present invention, by adding the above-mentioned subcomponent to barium titanate (main component), the reduction resistance is excellent and the relative dielectric constant can be increased. Further, if a dielectric layer containing barium titanate (main component) and the above-described subcomponents is used as the dielectric layer of the ceramic capacitor, the capacitance can be increased.

  According to the present invention, a sintered body having a high relative dielectric constant or a ceramic capacitor having a large capacity can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The sintered body according to the embodiment of the present invention includes barium titanate (BaTiO ₃ ) as a main component, and A-site elements including Ba and rare earth elements as subcomponents added to the main component, Ti, And a B-site element containing one or more elements selected from Zr, Sn, and Hf.

  The ratio of the A site element Ba to the B site element Ti (Ba / Ti ratio) in the main component is, for example, 0.997 to 1.002. Moreover, the rare earth element contained in the A-site element of the subcomponent is, for example, one or more elements selected from Y, Dy, and Ho. Moreover, other elements, such as Mg and Si, may be included as subcomponents.

  In such a sintered body, a compound of Ba, a compound of a rare earth element, and a compound of one or more elements selected from Ti, Zr, Sn, and Hf are added to barium titanate as a raw material of an auxiliary component. It can be obtained by firing in a reducing atmosphere. Barium titanate can be synthesized, for example, by a solid phase method in which titanium oxide powder and barium carbonate powder are mixed and heat-treated. Note that barium titanate may be synthesized not only by the solid phase method but also by a hydrothermal method, an oxalic acid method, a sol-gel method, or the like.

  According to the sintered body according to the present embodiment, a specific resistance (insulation resistance) can be obtained even when fired in a reducing atmosphere by adding the above-mentioned subcomponent to the main component (barium titanate). ) And relative permittivity can be increased. This is presumably because the reduction resistance was improved by adding the above-mentioned subcomponents, and the decrease in specific resistance (insulation resistance) and specific permittivity could be suppressed.

  FIG. 1 is a schematic cross-sectional view illustrating a cross-sectional structure of a ceramic capacitor according to an embodiment of the invention.

  This ceramic capacitor has a structure in which a dielectric layer 1 containing the above-mentioned main component and subcomponent is provided between opposing internal electrodes 2. This can be obtained by forming the internal electrode 2 on one side of a green sheet obtained by forming the above-mentioned main component and subcomponents into a sheet shape, and laminating and firing a plurality of these. In addition, external electrodes 3 and 4 connected to end portions of the internal electrode 2 are provided on the side surfaces of the laminate.

  Examples of the material for the internal electrode 2 and the external electrodes 3 and 4 include metals such as Cu, Ni, W, and Mo or alloys thereof, In—Ga, Ag, Ag-10Pd alloy, etc., or carbon, graphite, carbon and graphite. A mixture of the above can be used.

  The internal electrode 2 is, for example, a conductive paste having a predetermined viscosity, which is kneaded after adding a predetermined amount of an organic binder, a dispersant, an organic solvent, and a reducing agent, if necessary, to the powder made of the main material. It is formed by printing so as to form a predetermined pattern on one side of a sheet formed by forming a sintered body and firing in a reducing atmosphere. As the internal electrode 2, relatively inexpensive Ni or Ni alloy is desirable.

  Further, as the external electrodes 3 and 4, Cu is desirable because of its low resistance and low cost. The external electrodes 3 and 4 are formed on the outer surface of the laminated body including the internal electrode 2 and the dielectric layer 1 using a coating method or the like.

  According to the ceramic capacitor according to the present embodiment, since the material having a high relative dielectric constant described above is used as the material of the dielectric layer 1, the capacitance can be increased. In particular, when Ni or Ni alloy, which is a base metal that is easily oxidized in air, is used as the internal electrode 2, it is necessary to fire in a reducing atmosphere in which the Ni or Ni alloy is not oxidized. In this case, since the above-described material is excellent in reduction resistance, reduction of the dielectric layer 1 can be suppressed. Thereby, the dielectric constant of the dielectric layer 1 can be increased, and the capacitance of the ceramic capacitor can be increased.

  Next, an example of a method for manufacturing a ceramic capacitor according to an embodiment of the present invention will be described.

First, BaCO ₃ and TiO ₂ are weighed and mixed so that the Ba / Ti ratio in BaTiO _{3 is} in the range of 0.997 to 1.002 as raw materials for the main component BaTiO ₃ of the dielectric layer.

  Next, the main component compound is put in a ball mill, water is added, and the mixture is wet-mixed for about 20 hours to obtain a slurry. The slurry was dehydrated and dried, calcined at 1000 ° C. or higher, pulverized, and sized so that the average particle size was less than 0.2 μm. The average particle size was determined by observing the powder with a scanning electron microscope and measuring the particle size of 100 particles.

Next, each of TiO ₂ , BaCO ₃ , MgO, Mn ₃ O ₄ , SiO ₂ , and Re ₂ O ₃ (Re is one or more elements selected from Y, Dy, and Ho) with respect to the main component. Each compound powder was weighed, put into a ball mill, mixed with a toluene-ethanol mixed solvent, a polyvinyl butyral binder and a plasticizer until an appropriate viscosity was obtained, and a green sheet was prepared by a doctor blade method.

  Next, on each green sheet, after the internal electrode is screen-printed in a predetermined shape using a conductive paste made of Ni powder, a plurality of green sheets on which the conductive paste is printed are stacked, integrated by thermocompression bonding, A laminate was produced.

And after removing the organic binder by heating the laminated body in the air, it was baked for 2 hours in a reducing atmosphere at 1200 ° C. and then re-oxidized in an N ₂ gas atmosphere at 1000 ° C. for 2 hours. Thereafter, the external electrode is baked on the end face portion of the laminate in which the internal electrode is exposed, and the structure illustrated in FIG. 1 is obtained.

  Next, Table 1 and Table 2 show various evaluation results for Examples 1 to 28 and Comparative Examples A to L in which the composition of the dielectric layer was variously changed.

In Examples 1 to 28 and Comparative Examples A to L, the thickness per dielectric layer was 5 μm, and the effective dielectric layer was 10 layers. Moreover, the internal (opposite) electrode area per layer is 0.9 × 10 ⁻⁶ [mm ² ].

  The relative dielectric constant ε is a capacitance obtained by measuring an electrostatic capacity using an LCR meter under conditions of a temperature of 25 [° C.], a frequency of 1 [kHz], and a voltage of 2.5 [V]. The thickness was calculated from the thickness of the dielectric layer and the area of the internal electrode.

  The dielectric loss tan δ was measured using an LCR meter under the same conditions as the relative dielectric constant.

  The insulation resistance R was measured by applying a voltage of DC 100 [V] for 3 minutes to each of the multilayer ceramic capacitors of Examples 1 to 28 and Comparative Examples A to L under the condition of 25 ° C.

  The rate of change in capacitance was determined by putting each of the multilayer ceramic capacitors of Examples 1 to 28 and Comparative Examples A to L into a constant temperature layer, and at a temperature of −55 ° C. to 85 ° C., a frequency of 1 [kHz] and a voltage of 2.5 [V ] Was obtained by measuring the capacitance using an LCR meter and determining the change in capacitance with respect to the capacitance at 25 ° C. From this rate of change in capacitance, the suitability of the EIA (Electronic Industries Association) X5R standard (capacity change rate from -55 ° C. to 85 ° C. (25 ° C. standard) is plus or minus 15%) was judged.

In Table 1, the item in the first column represents the A-site element / B-site element ratio (Ba / Ti ratio) in the main component BaTiO ₃ of the dielectric layer.

In addition, the numerical values of the A-site element (Ba, Y, Dy, Ho), B-site element (Ti, Zr, Sn, Hf), Mg, and Si in the subcomponent are in 100 mol parts of the main component (BaTiO ₃ ). On the other hand, the molar part converted to Ba of the Ba compound, the molar part converted to Y of the Y compound, the molar part converted to Dy of the Dy compound, the molar part converted to Ho of the Ho compound, and converted to Ti of the Ti compound. Mol part, mol part converted to Zr of Zr compound, mol part converted to Sn of Sn compound, mol part converted to Hf of Hf compound, mol part converted to Mg of Mg compound, converted to Si of Si compound Each represents a mole part.

  The item [B + (Ti + Zr + Sn + Hf)] in the fourth column assumes that the composition of Ti, which is the B site element in the main component, is 1.000, (the composition of the main component Ti) + (subcomponent for 100 mole parts of the main component) The molar part of B site element / 100). Here, the mole part of the B-site element of the accessory component was converted into (mol part converted to Ti of Ti compound + mol part converted to Zr of Zr compound + mol part converted to Sn of Sn compound + Hf of Hf compound). Mole part).

  In Table 1, the composition of the main component Ti represented by “B” is all 1.000.

  The item [A / B + (Ba + Y + Dy + Ho)] in the third column represents (composition of Ba as the A site element in the main component) + (mole part of the A site element of the subcomponent relative to 100 mol parts of the main component). . Here, the mole part of the A-site element of the accessory component was converted to (mol part converted to Ba of the Ba compound + mol part converted to Y of the Y compound + mol part converted to Dy of the Dy compound + Ho of the Ho compound). Mole part).

  The item [A / B + (Ba + Y + Dy + Ho) − (Ti + Zr + Sn + Hf)] in the second column is (Ba of the main component / Ti ratio of the main component) + (mol part of the A-site element of the subcomponent with respect to 100 mol part of the main component) / 100 )-(Mole part of B site element of subcomponent / 100 parts by mole of main component / 100).

  From the results of Tables 1 and 2, if [B + (Ti + Zr + Sn + Hf)] is 1.002 to 1.010, a desired high dielectric constant can be obtained.

  In Comparative Example A where [B + (Ti + Zr + Sn + Hf)] is smaller than 1.002 and Comparative Example B larger than 1.010, the relative dielectric constant is smaller than 2600 and insufficient.

Further, in Comparative Example H in which [B + (Ti + Zr + Sn + Hf)] is 1.012 which is the same as Comparative Example B, sintering was not performed (unsintered).
When the density is measured with a sample for density measurement obtained by stacking a plurality of green sheets having a thickness of 40 μm so as to have a thickness of 1 mm, then cutting into 1 cm square and firing, and this is a density of 5.7 or less And “unsintered”.

  Also, looking at the results for [A / B + (Ba + Y + Dy + Ho) − (Ti + Zr + Sn + Hf)], if [A / B + (Ba + Y + Dy + Ho) − (Ti + Zr + Sn + Hf)] is 1.009 to 1.018, the desired high ratio A dielectric constant is obtained.

  In Comparative Examples C, D, E, and Comparative Examples A, F, and G, where A / B + (Ba + Y + Dy + Ho) − (Ti + Zr + Sn + Hf)] is less than 1.009, the relative dielectric constant is less than 2600 and insufficient. It is.

  Further, Comparative Examples F and G did not satisfy the X5R standard and were incompatible.

  Therefore, assuming that the composition of Ti which is the B site in the main component is 1.000, (composition of Ti of the main component) + (mol part of B site element of subcomponent per 100 mol parts of main component / 100) is 1.002. ˜1.010, (Ba ratio of main component / Ti ratio of main component) + (mol part of A-site element of subcomponent with respect to 100 mol parts of main component / 100) − (B site of subcomponent with respect to 100 mol parts of main component) It is desirable that the mol part / 100) of the element is 1.009 to 1.018. In Examples 1 to 28 that satisfy this requirement, normal sintering was achieved, a sufficient dielectric constant was obtained, and the X5R standard was also met.

  Further, in particular, as in Examples 2 to 4, 7, 8, 10, 11, 13, 14, 16 to 28, (composition of main component Ti) + (subsite B site of subcomponent with respect to 100 mol parts of main component) (Mol part of the element / 100) is 1.002 to 1.008, (Ba of the main component / Ti ratio of the main component) + (mol part of the A-site element of the subcomponent with respect to 100 mol part of the main component)-( If the molar part of the B-site element as a minor component / 100) with respect to 100 mole parts of the main component is set to 1.011 to 1.015, a relative dielectric constant close to 3000 or exceeding 3000 is obtained, which is more desirable.

  In addition, in Comparative Example I where the molar part converted to Mg of the Mg compound contained in the subcomponent is 0.5 molar part and Comparative Example J which is 2.4 molar part relative to 100 molar parts of the main component, The relative dielectric constant was less than 2600, and the X5R standard was not compliant.

  Therefore, it is desirable that the molar part converted to Mg of the Mg compound is 0.7 to 2.1 molar part with respect to 100 molar part of the main component. In Examples 1 to 28 that satisfy this requirement, normal sintering was achieved, a sufficient dielectric constant was obtained, and the X5R standard was also met.

  In addition, in Comparative Example K, in which the mole part converted to Si of the Si compound contained in the subcomponent is 1.0 mole part with respect to 100 mole parts of the main ingredient, it is not sintered, and with respect to 100 mole parts of the main ingredient In Comparative Example L, in which the molar part converted to Si of the Si compound contained in the subcomponent was 2.3 molar part, the X5R standard was incompatible.

  Therefore, it is desirable that the mole part converted to Si of the Si compound is 1.2 to 2.0 mole parts with respect to 100 mole parts of the main component. In Examples 1 to 28 that satisfy this requirement, normal sintering was achieved, a sufficient dielectric constant was obtained, and the X5R standard was also met.

1 is a schematic cross-sectional view illustrating a cross-sectional structure of a ceramic capacitor according to an embodiment of the invention.

Explanation of symbols

1 Dielectric layer 2 Internal electrode 3, 4 External electrode

Claims (8)

As a main component, contains barium titanate,
The secondary component added to the main component includes an A site element containing Ba and a rare earth element, and a B site element containing one or more elements selected from Ti, Zr, Sn, and Hf. Sintered body. The composition of Ti as the main component is 1.000,
(Composition of Ti of the main component) + (mol part of B site element of the subcomponent with respect to 100 mol part of the main component / 100) is 1.002 to 1.010,
(Ba of the main component / Ti ratio of the main component) + (mol part of the A-site element of the subcomponent with respect to 100 mol parts of the main component / 100) − (B of the subcomponent with respect to 100 mol parts of the main component) 2. The sintered body according to claim 1, wherein a site element molar part / 100) is 1.009 to 1.018. (Composition of Ti of the main component) + (mol part of B site element of the subcomponent with respect to 100 mol part of the main component / 100) is 1.002 to 1.008,
(Ba of the main component / Ti ratio of the main component) + (mol part of the A-site element of the subcomponent with respect to 100 mol parts of the main component / 100) − (B of the subcomponent with respect to 100 mol parts of the main component) The molar part of the site element / 100) is 1.011 to 1.015. The sintered body according to claim 2, wherein: For 100 mole parts of the main component,
0.7 to 2.1 mole parts Mg,
1.2 to 2.0 mole parts Si;
The sintered body according to claim 2, further comprising: as a subcomponent. A ceramic capacitor comprising a plurality of electrodes and a dielectric layer provided between the electrodes,
The dielectric layer includes barium titanate as a main component, and as an auxiliary component added to the main component, an A site element including Ba and a rare earth element, and one kind selected from Ti, Zr, Sn, and Hf A ceramic capacitor comprising a B-site element including the above elements.   The ceramic capacitor according to claim 5, wherein the electrode includes Ni or a Ni alloy.   To the barium titanate, a Ba compound, a rare earth element compound, and a compound of one or more elements selected from Ti, Zr, Sn, and Hf are added as accessory ingredients, and this is added in a reducing atmosphere. A method for producing a sintered body characterized by firing. A sheet-like material obtained by adding a compound of Ba, a rare earth element compound, and a compound of one or more elements selected from Ti, Zr, Sn, and Hf to barium titanate as a raw material of the accessory component Forming a dielectric layer;
Laminating them with an electrode interposed between the plurality of dielectric layers;
A method of manufacturing a ceramic capacitor, comprising:

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