JP2013155064A - Dielectric ceramic composition and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition that has high specific resistance characteristics while keeping a high dielectric constant.SOLUTION: A dielectric ceramic composition includes a first phase having as a principal component a compound represented by general formula CaCuTiO, a second phase having as a principal component a compound represented by general formula CaTiSiO, and a mixed-phase structure of the first phase and the second phase.

Description

  The present invention relates to a dielectric ceramic composition and an electronic component.

There is a strong demand for downsizing and high performance of electronic devices in recent years. In order to meet the demand for higher performance of such electronic equipment, higher performance of electronic components used in various electronic devices such as oscillators, resonators, multilayer circuit boards, and microwave circuits has been studied. In particular, capacitors for electronic parts are strongly demanded to be smaller and have a higher capacity, and higher dielectric constant characteristics are required as higher performance of the dielectric ceramic composition, that is, the dielectric material. The requirement for the dielectric constant characteristics of such a dielectric material discloses a compound represented by CaCu ₃ Ti ₄ O ₁₂ (CCTO) having a high dielectric constant disclosed in Patent Document 1.

  However, although this CCTO compound has a high specific dielectric constant characteristic, it cannot obtain a sufficient specific resistance characteristic necessary for a capacitor, and can be applied as a dielectric material for a capacitor that requires a specific resistance characteristic. There wasn't.

Therefore, the MnO (Non-Patent Document 1) in CCTO, ZrO ₂ (Non-patent Document 2), SiO ₂ (non-patent document 3) compound material was added such Tokue, a high resistance characteristic of the CCTO compound Various attempts have been made to achieve this.
However, there is a problem that the relative dielectric constant characteristics are lowered when an attempt is made to increase the resistance of the CCTO compound. For this reason, the CCTO compound has not yet obtained the result of achieving the specific resistance characteristics necessary for the multilayer ceramic capacitor while maintaining a high relative dielectric constant.

JP 2008-143758 A

APPLYED PHYSICS LETTERS 88, 23903, 2006 APPLYED PHYSICS LETTERS 87, 182911, 2005 Journal Of European Ceramic Society 27, 3991-3995, 2007

  Therefore, an object of the present invention is to provide a dielectric ceramic composition having a high specific resistance while maintaining a high specific dielectric constant.

In order to achieve the above object, the dielectric ceramic composition of the present invention is represented by a first phase mainly composed of a compound represented by the general formula CaCu _y Ti ₄ O ₁₂ and a general formula CaTiSiO _5. It has the mixed phase structure of the 2nd phase which has a compound as a main component, and said 1st phase and said 2nd phase, It is characterized by the above-mentioned. (Y is an arbitrary number in the range of 0 <y <3)

  In order to have a mixed phase structure of a first phase having a high dielectric constant and a second phase having a high resistance, the dielectric ceramic composition of the present invention maintains a high relative dielectric constant and has a specific resistance characteristic. A high dielectric ceramic composition can be obtained.

Furthermore, preferably, in the X-ray diffraction measurement of the dielectric ceramic composition, the X-ray diffraction intensity of the (21-1) plane of the second phase is the X-ray diffraction intensity of the (222) plane of the first phase. The value of the divided quotient is set to 0.03 or more and 1.00 or less.
As a result, it is possible to obtain characteristics with high specific resistance and a higher dielectric constant of 5000 or more. A relative dielectric constant of 5000 or more is useful, for example, for increasing the size and capacity of multilayer ceramic capacitors.

Moreover, y of the compound represented by the general formula (CaCu _y Ti ₄ O ₁₂ ) of the first phase is set to a value in the range of 2.9 to 3.1. As a result, it is possible to suppress the generation of heterogeneous phases such as copper oxide and calcium titanate that affect the specific permittivity and specific resistance. If a different phase exists, the dielectric constant and the resistance value are expected to decrease. Therefore, it is necessary to prepare a dielectric ceramic composition under the condition that no different phase is generated.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide as a dielectric ceramic composition with a high specific resistance characteristic, maintaining a high dielectric constant.

1 is a schematic cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. The pattern of the result of the X-ray diffraction measurement of Example 4 is shown.

The dielectric ceramic composition according to an embodiment of the present invention mainly includes a first phase mainly composed of a compound represented by the general formula CaCu _y Ti ₄ O ₁₂ and a compound represented by the general formula CaTiSiO _5. By having the second phase as a component and the mixed phase structure of the first phase and the second phase, it is possible to obtain a characteristic having a high specific resistance while maintaining a high specific dielectric constant. (Y is an arbitrary number in the range of 0 <y <3)

This mixed phase structure can be determined by, for example, X-ray diffraction (XRD) or electron diffraction analysis. More specifically, X-ray diffraction peaks attributed to two crystal phases of CaCu _y Ti ₄ O ₁₂ and CaTiSiO ₅ and electron beam diffraction peaks can be confirmed from the X-ray diffraction analysis. Furthermore, the ratio, size, dispersion, and the like of these phases can be confirmed from cross-sectional observation of the dielectric ceramic composition.

The mixed phase structure of the first phase and the second phase is obtained by combining the first phase having a high relative dielectric constant and a low specific resistance and the second phase having a low relative dielectric constant and a high specific resistance. A dielectric ceramic composition having a higher specific resistance can be obtained.
In other words, it has a mixed phase structure of CaCu _y Ti ₄ O ₁₂ which is the first phase having a high relative dielectric constant and CaTiSiO ₅ which is the second phase having a high specific resistance, so that it is composed of CaCu _y Ti ₄ O ₁₂ alone. Instead, the substantial electrical conduction path becomes longer and the resistance value becomes higher. At that time, CaCu _y Ti ₄ O ₁₂ and CaTiSiO ₅ are required to have two phases in order to maintain the high dielectric constant inherent in CaCu _y Ti ₄ O ₁₂ .

_Further, the first phase mainly composed of a compound represented by CaCu _y Ti _{4 O 12} is preferably a mixed oxide in the range of 2.9 ≦ y ≦ 3.1. If y is out of the above range, a foreign phase such as CaTiO ₃ or CuO is generated, and the dielectric constant of CaCu _y Ti ₄ O ₁₂ may be reduced. In addition, CuO is a semiconductor, and this phase may reduce the specific resistance.

And, the phase of CaCu _y Ti ₄ O ₁₂ and CaTiSiO ₅ is not limited to the formation of a structure in which these two types of crystal phases are mixed, and various metals can be used as long as the dielectric constant characteristics are not lowered thereby. These oxides, double oxides and the like can also be contained as subcomponents. Examples of such subcomponents include SrTiO ₃ , TiO ₂ , MgTiO ₃ , La ₂ O ₃ , Bi ₂ O _{3 and the} like.

  The y and subcomponents of the compound can be determined by elemental analysis such as X-ray fluorescence analysis (XRF) or inductively coupled plasma (ICP) emission spectroscopy.

The second phase mainly composed of a compound represented by CaTiSiO ₅ is a double oxide compound in which Ca, Ti, and Si elements are present in the same element ratio.

Here, the mixed phase structure of the first phase and the second phase is a structure including a crystal phase of CaCu _y Ti ₄ O _{12 and} a crystal phase of CaTiSiO ₅ . Preferably, each is uniformly dispersed, and the first phase preferably has a particle size of 0.1 to 10 μm. It is preferable that these phases are uniformly dispersed because the CaTiSiO ₅ phase has the effect of increasing resistance due to the inhibition of electrical conduction. Further, the particle is preferably 0.1 to 10 μm in consideration of application to a laminate structure.

Further, when the inventors examined, the quotient obtained by dividing the X-ray diffraction intensity of the (21-1) plane of the second phase by the X-ray diffraction intensity of the (222) plane of the first phase was 0.03. As described above, by setting it to 1.00 or less, a higher dielectric constant of 5000 or more can be obtained.
When the value of the quotient is in the range of 1.00 or less, it is more preferable in terms of a characteristic having a high specific resistance and a dielectric constant of 5000 or more. This is because the dielectric constant of the first phase is higher than that of the second phase. This is because it is high and the specific resistance is low.

And, when the area ratio of the second phase is in the range of 0.03 or more, it is more preferable in that the specific resistance is 2.5 × 10 ¹⁰ Ω · μm or more. This is because the dielectric constant of the second phase is low and the specific resistance is high.

Y of the compound represented by CaCuyTi ₄ O ₁₂ is a value in the range of 2.9 to 3.1, and y is set to 2.9 or more in that it does not precipitate a heterogeneous phase of CuO or CaTiO _3. It is desirable. If it is 2.9 or less, a CaTiO ₃ heterogeneous phase is precipitated, which is not preferable in terms of obtaining a higher relative dielectric constant. If it is 3.1 or more, a CuO heterogeneous phase tends to precipitate in the dielectric ceramic composition, which is not preferable in terms of obtaining a high relative dielectric constant.

  The dielectric ceramic composition according to the present embodiment can be applied to, for example, an LC filter, a coupler, a module component substrate, etc. in addition to the capacitor.

An example of a method for producing a dielectric ceramic composition according to this embodiment will be described. It is preferable in that a first phase and a second phase are formed by adding CaCO ₃ , SiO _2, TiO _{2 to} a compound having a CaCu _y Ti ₄ O ₁₂ phase and baking it.
First, a compound powder containing Ca, Cu, and Ti is blended and mixed so as to have a predetermined composition to obtain a mixed powder. Next, the obtained mixed powder is calcined at a temperature capable of having a CCTO crystal phase of about 660 ° C. to 900 ° C. in the air, for example, to obtain a calcined powder.
Furthermore, the obtained calcined powder is obtained by mixing a binder resin such as polyvinyl butyral and polyvinyl alcohol, a compound containing an organic solvent and Ca, a compound containing Si, and a powder of a compound containing Ti at a predetermined ratio, and a dielectric paste. To adjust as. These compounds may be added after preparing CaTiSiO5 in advance. This dielectric paste is formed into a sheet shape, and the molded product obtained by laminating is fired, for example, in the atmosphere at a temperature of 900 ° C. to 1100 ° C. to obtain a dielectric ceramic composition.

  In particular, FIG. 1 shows a multilayer ceramic capacitor 1 as an electronic component according to an embodiment of the present invention. The multilayer ceramic capacitor 1 has a capacitor element body 10 in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. When the dielectric ceramic composition is applied to a multilayer capacitor, the calcined product is mixed with an organic solvent together with a binder resin and a powder of a compound containing Ca, Ti, and Si in a predetermined ratio, and the base of the dielectric layer. This paste is alternately printed and laminated with the paste that forms the internal electrode layer, or the calcined material is mixed with a binder resin to form a ceramic green sheet. A paste is obtained by alternately laminating pastes that form the internal electrode layers. Further, the multilayer body is fired and provided with terminal electrodes, whereby a multilayer ceramic capacitor in which the dielectric ceramic compositions as the dielectric layers 2 are alternately stacked is manufactured.

Hereinafter, the present invention will be described based on examples, but the configuration of the present invention is not limited to these examples.
Example 1

CaCO _3, CuO, and TiO ₂ powder, each chemical formula CaCuyTi ₄ O ₁₂ and so as to CaCO ₃ and CuO and TiO ₂ to the dielectric ceramic composition after firing 15.0 g, 34.6 g, 47. 8 g each was mixed with YTZ balls in water, and the liquid containing the mixed powder was dried and ground in a mortar to prepare a mixed powder. At this time, the value of y is 2.95, and the value is in the range of 2.9 to 3.1.

Next, this mixed powder was calcined at 700 ° C. in the air to obtain a calcined powder. It was confirmed that CaCu _2.95 Ti ₄ O ₁₂ was produced by XRD.

Next, after mixing CaCO ₃ , TiO ₂ and SiO ₂ with 100 g of CaCu _2.95 Ti ₄ O ₁₂ powder as shown in Table 1, the calcined powder is mixed with 1.30, 1.04 and 0.78 g. Then, a binder resin and an organic solvent were mixed to obtain a dielectric paste.

  Next, a ceramic green sheet having a thickness of about 10 μm is molded from the paste of each composition by a doctor blade method, laminated to a thickness of about 600 μm, cut into 12 mm × 12 mm, and a dielectric ceramic composition of the laminated body is obtained. Obtained.

Next, the obtained laminate is maintained in the atmosphere at 1000 ° C. for 2 hours, and has a mixed phase structure in which CaCu _2.95 Ti ₄ O ₁₂ is the first phase and CaTiSiO ₅ is the second phase. A dielectric ceramic composition was obtained. This dielectric ceramic composition showed a mixed phase structure of CaCu _2.95 Ti ₄ O ₁₂ and CaTiSiO ₅ by XRD. The peak intensity indicated by XRD is that when the intensity of the (222) plane of CaCu _2.95 Ti ₄ O ₁₂ is 896.22, the intensity of the (21-1) plane of CaTiSiO ₅ is 245.69, (222 ) The quotient of the strength of the (21-1) plane relative to the plane strength was 0.27.

(Examples 2-9)
Except for using CaCu _2.95 Ti ₄ O ₁₂ and CaCO ₃ , TiO ₂ , and SiO ₂ in the ratios shown in Table 1, the dielectric ceramic compositions of Examples 2 to 9 were produced in the same manner as in Example 1. Obtained.

(Examples 10, 11, and 12)
In the preparation of CaCu _y Ti ₄ O ₁₂ calcined powder, CaCO ₃ , CuO, and TiO ₂ were respectively 15.0 g, 34.6 g, and 48.0 g so that y was 2.90 in Example 10. In Example 11, 14.9 g, 35.5 g, and 47.6 g of CaCO ₃ , CuO, and TiO ₂ are used so that y is 3.0, and in Example 12, y is 3.1. CaCO ₃ , CuO, and TiO ₂ were mixed with 14.8 g, 36.4 g, and 47.2 g, respectively, as shown in Table 1. Otherwise, a dielectric ceramic composition was obtained in the same manner as in Example 3.

(Example 13)
In preparing CaCu _2.95 Ti ₄ O ₁₂ calcined powder, CaCO ₃ , SiO ₂ , and TiO ₂ were added together in the proportions shown in Table 1 to produce a calcined powder, which was the same as Example 1. The dielectric ceramic composition was obtained by this method.

Table 1 shows a table of ratios of mixing CaCu _y Ti ₄ O ₁₂ and CaCO ₃ , TiO ₂ , and SiO ₂ .

(Comparative Example 1)
A dielectric ceramic composition of Comparative Example 1 was obtained in the same manner as in Example 1 except that CaCO ₃ , TiO ₂ , and SiO ₂ were not mixed into the CaCu _2.95 Ti ₄ O ₁₂ calcined powder. It was.

  The relative dielectric constant characteristics were determined by applying an In-Ga paste to the upper and lower surfaces of each dielectric porcelain composition, forming electrodes, and using an LCR meter (4284A manufactured by HPWLETT) at room temperature. From the measured results, the relative permittivity ε ′ when regarded as a parallel plate capacitor was calculated and evaluated. The measurement frequency was 1 kHz and the voltage was 1V. The results are shown in Table 2.

  Further, a resistance value when a direct current of 1 V was applied to the obtained dielectric ceramic composition and the charge time was 30 seconds was measured with a resistance measuring instrument (R8240 ULTRA HIGH RESISTANCE METER) to obtain specific resistance characteristics. The results are shown in Table 2.

The ratio of the XRD intensity of the first phase and the second phase is CaCu _y Ti ₄ when the value obtained by subtracting the background from the intensity indicated by XRD (X'Pert PRO MPD manufactured by Panallytical) is the X-ray diffraction intensity. A quotient obtained by dividing the peak intensity of the (21-1) plane of CaTiSiO _{5 by} the peak intensity of the (222) plane of O ₁₂ was used. The results are shown in Table 2.
The produced sample was irradiated with X-rays with a source of CuKα to obtain a diffraction pattern of the sample. FIG. 1 shows the X-ray diffraction pattern of Example 4. In the X-ray diffraction pattern, the (222) plane of CaCu ₃ Ti ₄ O ₁₂ is a peak obtained in the vicinity of 34.5 ° at 2θ, and the (21-1) plane of CaTiSiO ₅ is in the vicinity of 27.7 ° at 2θ. This is the peak obtained.

On the other hand, from Table 2, the specific resistance characteristics of the comparative example 1 that does not contain CaTiSiO ₅ (0 mol%) have a specific resistance of 5.53 × 10 ¹⁰ Ω · μm, while that of CaTiSiO ₅ ( In Example 5 in which the quotient obtained by dividing the X-ray diffraction intensity of the 21-1) plane by the X-ray diffraction intensity of the (222) plane of CaCuyTi ₄ O ₁₂ is 0.514, the specific resistance is 6.4 × 10 6. ¹¹ Ω · μm. As a result, it was confirmed that the specific resistance ratio was improved 10 times or more than that of the single CCTO.

In each of Example 1 to Example 13, CaTiSiO _{5 as} the first phase was confirmed by CaCu _y Ti ₄ O ₁₂ as the first phase in XRD. As a tendency, the larger the ratio of the second phase, the larger the specific resistance (the specific resistance characteristic is 1.00 × 10 ¹⁰ (Ω · μm) or more), and the larger the ratio of the first phase, the larger the dielectric constant. all right.

In Comparative Example 1, the first phase was CaCu _y Ti ₄ O ₁₂ by XRD, and the second phase CaTiSiO ₅ was not confirmed, and the single phase was CaCu _y Ti ₄ O ₁₂ .
For this reason, CaTiSiO ₅ having a high specific resistance does not exist, the specific resistance characteristics are less than 1.00 × 10 ¹⁰ (Ω · μm), and sufficient characteristics as a dielectric ceramic composition cannot be obtained.

In Examples 1 to 5 and 10 to 13, in the strength of XRD, the intensity ratio of the (222) plane of the first phase and the (21-1) plane of the second phase is 0.03 or more and less than 1.000. The specific permittivity (relative permittivity is 5000 or more) higher than that of Examples 7, 8, and 9 is obtained, and the specific resistance characteristic higher than that of Example 9 (specific resistance characteristic is 1.00). × 10 ¹¹ (Ω · μm) or more) was obtained.

The dielectric ceramic composition according to the present invention is useful for electronic parts of various electronic devices such as an oscillator, a resonator, a multilayer circuit board, and a microwave circuit including a dielectric layer containing the dielectric ceramic composition. is there.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Dielectric layer 3 Internal electrode layer 4 External electrode 10 Capacitor element body

Claims (4)

A first phase mainly comprising a compound represented by the general formula CaCu _y Ti ₄ O ₁₂ ;
A second phase mainly composed of a compound represented by the general formula CaTiSiO ₅ ;
A dielectric ceramic composition having a mixed phase structure of the first phase and the second phase. (Y is an arbitrary number in the range of 0 <y <3) The X-ray diffraction intensity of the (21-1) plane of the second phase CaTiSiO ₅ of the dielectric ceramic composition is divided by the X-ray diffraction intensity of the (222) plane of the first phase CaCu _y Ti ₄ O _12. The dielectric ceramic composition according to claim 1, wherein the quotient value is 0.03 or more and 1.00 or less. 3. The compound according to claim 1, wherein y of the compound represented by the general formula CaCu _y Ti ₄ O ₁₂ of the first phase is a value in a range of 2.9 to 3.1. The dielectric ceramic composition as described in 1.   An electronic component comprising a dielectric layer containing the dielectric ceramic composition according to any one of claims 1 to 3.

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