WO2013073295A1 - Dielectric porcelain composition and ceramic electronic components using same - Google Patents

Abstract

[Problem] To provide a dielectric porcelain composition which has a high relative dielectric constant even when calcined at a low temperature and ceramic electronic components in which the dielectric porcelain composition is applied to dielectric layers thereof. [Solution] A dielectric porcelain composition is obtained which comprises: a compound which is represented by general formula ABO₃ (A is Ba and at least one type of element selected from Ca and Sr, and B is at least one type of element selected from Ti and Zr) and which has a perovskite crystal structure; and a compound composed of a rare earth titanium oxide which is represented by general formula R₂Ti₂O₇ (wherein element R is at least one type of element selected from Sc, Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu).

Description

Dielectric porcelain composition and ceramic electronic component using the same

The present invention relates to a dielectric ceramic composition and a ceramic electronic component using the same, and more specifically, a dielectric ceramic composition capable of obtaining excellent electrical characteristics while firing at a low temperature, and a ceramic electronic component using the same. It is about.

Recently, in order to maintain price competitiveness in the ceramic electronic parts market where price competition is intense, further reduction in manufacturing cost is strongly demanded. As one means for realizing such cost reduction, it is extremely effective to obtain a dielectric ceramic composition by firing at a low temperature of 1100 ° C. or lower. Moreover, firing at a low temperature is also effective from the viewpoint of suppressing CO ₂ emission.

Also, there is a high demand for downsizing and increasing the capacity of electronic components accompanying the increase in the density of electronic circuits, and for this reason, for example, multilayer ceramic capacitors are becoming thinner and multilayered. As a means for realizing such thin-layer multi-layering, firing at a low temperature is effective in obtaining a thin electrode layer with good lineability and a dielectric layer with a uniform particle diameter.

Conventionally, in order to obtain desired electrical characteristics, it is necessary to add various additives such as rare earth oxides to a compound having a perovskite crystal structure and calcinate. Therefore, the temperature required for calcination is as high as 1300 ° C. or higher. Become. Therefore, generally, a large amount of Si compound is usually added for the purpose of lowering the firing temperature.

However, for example, when BaTiO ₃ is used as the base material, as shown in Patent Document 1, the firing temperature using only the SiO ₂ compound without greatly impairing the relative dielectric constant is generally as high as about 1200 ° C., Insufficient low-temperature firing effect. On the other hand, the addition of an excessive Si compound is easy to form a second phase having a low relative dielectric constant, either alone or with additives, during sintering, and the dielectric constant of the resulting dielectric ceramic composition is remarkably lowered. Not right.

Further, even when lithium oxide having a stronger low-temperature firing effect than Si compounds is used, when the firing is performed at a low temperature of about 1100 ° C., the thermal diffusion of the added element does not sufficiently proceed and the grain boundary layer or triple point Therefore, there is a fundamental problem that the relative dielectric constant of the obtained dielectric ceramic composition is remarkably lowered. Therefore, as in Patent Document 2, when BaTiO ₃ is used as a base material, the firing temperature is 1180 ° C., which is not sufficient for lowering the temperature even when the low temperature firing is performed using lithium oxide. It has been common to use a Si compound in combination with a small amount of Li.

Further, as disclosed in Patent Document 3, a dielectric ceramic composition characterized by containing R ₂ Ti ₂ O ₇ together with BaO and TiO ₂ has been reported for a low dielectric constant temperature compensation material. The rare earth elements having large ionic radii such as Nd, La, Pr, Ce, and Sm were selected as the R elements, and they were not intended for low-temperature sintering.

JP-A-8-180733 JP 2004-182582 A JP 2003-267778 A

The present invention has been made in view of such a situation, and a dielectric ceramic composition having a high relative dielectric constant even when fired at a low temperature, and a ceramic electronic in which the dielectric ceramic composition is applied to a dielectric layer The purpose is to provide parts.

In order to achieve the above object, the present invention provides a general formula ABO ₃ (A is at least one element selected from Ba, Ca and Sr, and B is at least one element selected from Ti and Zr) And a compound β comprising a rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ (wherein R element is Sc, Y, Eu, Gd, Tb) , Dy, Ho, Er, Tm, Yb and Lu) and a dielectric ceramic composition comprising a grain boundary formed between the particles of the compound α. To do.

The formation of R ₂ Ti ₂ O ₇ facilitates the formation of a liquid phase at a low temperature as compared with the case where a large amount of R ₂ O ₃ is present as the second phase. As a result, it is considered that the low dielectric constant component remaining at the grain boundary or the grain boundary triple point decreases, the grain boundary becomes thin, and the relative dielectric constant increases.

As an aspect of the present invention, the peak intensity of the surface index (222) in the X-ray diffraction chart of the compound β is 0.5 to about the peak intensity of the surface index (110) in the X-ray diffraction chart of the compound α. The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition is 9.0%.

Further, the present invention is characterized in that a ceramic electronic component having a dielectric layer composed of the dielectric ceramic composition and an electrode layer is obtained.

The present invention can provide a dielectric ceramic composition having a high relative dielectric constant even when fired at a low temperature, and a ceramic electronic component in which the dielectric ceramic composition is applied to a dielectric layer. Play.

1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. Is a diagram illustrating the relationship R ₂ Ti ₂ O ₇ content and relative dielectric constant as the effect of one embodiment of the present invention. It is a figure explaining the relationship between Li compound addition amount and a dielectric constant as an effect of one Embodiment in this invention. It is a figure explaining the relationship between Li compound addition amount and a dielectric constant as an effect of one Embodiment in this invention.

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

Multilayer ceramic capacitor 1
As shown in FIG. 1, the multilayer ceramic capacitor 1 includes a capacitor element body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. At both ends of the capacitor element body 10, a pair of external electrodes 4 are formed which are electrically connected to the internal electrode layers 3 arranged alternately in the capacitor element body 10. The shape of the capacitor element body 10 is not particularly limited, but is usually a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use.

Dielectric layer 2
The dielectric layer 2 is composed of a dielectric ceramic composition according to this embodiment. The dielectric ceramic composition has, as a main component, a general formula ABO ₃ (A is Ba alone or at least one selected from Ba and Ca and Sr, and B is Ti alone or Ti and Zr. ) And a compound composed of a rare earth titanium oxide phase represented by the general formula R ₂ Ti ₂ O ₇ as an auxiliary component (wherein R element is Sc, Y, Eu, Gd, Tb, Dy) , Ho, Er, Tm, Yb and Lu). Note that the amount of oxygen (O) may be slightly deviated from the stoichiometric composition.

Specifically, the compound is a compound represented by a composition formula (Ba _1-xy Ca _x Sr _y ) · (Ti _1-m Zr _m ) O ₃ and having a perovskite crystal structure. Further, at least Ba is included as the A site atom, and at least Ti is included as the B site atom. Furthermore, the molar ratio between the A site atoms (Ba, Sr, and Ca) and the B site atoms (Ti and Zr) is expressed as an A / B ratio. It is preferably 98 to 1.02.

In the present embodiment, x = y = m = 0 in the above formula, that is, barium titanate is particularly preferable. The grain boundary contains elements such as Ti and Si and exists between the compounds α.

A compound comprising a rare earth titanium oxide phase represented by the general formula R ₂ Ti ₂ O ₇ (where R element is selected from Sc, Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) In the X-ray diffraction chart, the content of at least one selected from the general formula ABO ₃ (A is Ba alone, or at least one selected from Ba and Ca and Sr, and B is Ti alone, or In the plane index (222) of the rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ with respect to the peak intensity of the plane index (110) of the compound having a perovskite type crystal structure. The peak intensity is 0.5-9%. By setting the content of the compound comprising the rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ in the above range, there is an advantage that it is easy to achieve both a low firing temperature and a high relative dielectric constant. The R element is at least one selected from Sc, Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and preferably at least one selected from Y, Ho, Dy, Yb. , Y, Dy, and Yb are more preferable.

In the present embodiment, other components may be contained as necessary.

For example, Mg oxide may be contained. The content thereof is preferably 0.5 to 3 mol in terms of Mg element with respect to 100 mol of the compound represented by ABO ₃ . By setting the content of the oxide in the above range, there is an advantage that the crystal particle diameter of the dielectric particles can be easily controlled, and the desired fine structure of the dielectric ceramic composition can be obtained. .

Further, for example, an oxide of at least one element selected from Mn, Cr, Co, Fe, and Cu may be contained. The content of these oxides is preferably 0.1 to 1 mol in terms of each element with respect to 100 mol of the compound represented by ABO ₃ . By making the content of the oxide within the above range, the diffusion of the R element into the core at the center of the crystal grain can be easily controlled, and the desired microstructure of the dielectric ceramic composition is desired. There is an advantage that can be. Among these oxides, it is preferable to use an oxide of Mn and / or an oxide of Cr from the viewpoint that the effect of improving characteristics is great.

Further, for example, an oxide of at least one element selected from V, Mo and W may be contained. The content of these oxides is preferably 0.05 to 0.5 mol in terms of each element with respect to 100 mol of the compound represented by ABO ₃ . By setting the content of the oxide within the above range, there is an advantage that the desired microstructure of the dielectric ceramic composition can be made desired. Of these oxides, the oxide of V is preferably used from the viewpoint that the effect of improving the characteristics is great.

For example, if it is a small amount, a compound containing Si may be contained. The content of these compounds is preferably 0.8 mol or less in terms of Si element with respect to 100 mol of the compound represented by ABO ₃ . By setting the content of the compound in the above range, deterioration of characteristics can be suppressed while easily controlling the firing temperature and holding time, and the desired microstructure of the dielectric ceramic composition can be obtained as desired. There is an advantage that it can be made. The compound containing Si is preferably an oxide of Si or a composite oxide of Si and at least one selected from Li, B, Al, Ba and Ca.

The thickness of the dielectric layer 2 is not particularly limited, and may be determined as appropriate according to desired characteristics and applications.

Microstructure of the dielectric ceramic composition In this embodiment, the rare earth titanium oxide phase represented by the general formula R ₂ Ti ₂ O ₇ contained in the dielectric ceramic composition constituting the dielectric layer 2 is used. The resulting compound may form a segregation phase independent of the compound represented by ABO ₃ , or may exist in the grain boundary layer or grain boundary triple point of the main component (ABO ₃ ).

In the present embodiment, the rare earth element R exists mainly in the form of a rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ , but is not necessarily limited to the compound, and a part thereof is R _It may be present in oxides such as ₂ O ₃ and other forms.

The method for observing the microstructure of the dielectric ceramic composition is not particularly limited. For example, a reflected electron image using a YAG (yttrium / aluminum / garnet) detector attached to a scanning electron microscope (SEM) is used. From the contrast, the main component (ABO ₃ ) and the segregation phase containing the rare earth element R may be observed, and energy dispersive X-ray spectroscopy attached to the scanning transmission electron microscope (STEM) or the scanning electron microscope (SEM). main component using a device (EDS) (ABO ₃₎ and may be observed and segregation phase containing a rare earth element R.

Further, the dielectric ceramic composition mainly containing a segregation phase containing rare earth elements R and Ti is identified from the peak position of the chart obtained by the X-ray diffraction (XRD) method, whereby the rare earth elements R It can be specified that the main compound containing is a rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ .

For example, when a rare earth titanium oxide represented by Y ₂ Ti ₂ O ₇ with barium titanate BaTiO ₃ as the main component is used as a subcomponent, the plane index (222), (400), (622), (444) ), The presence of Y ₂ Ti ₂ O ₇ can be confirmed by confirming the peak position of the X-ray diffraction chart corresponding to (840).

Furthermore, the method for deriving the ratio of the rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ to the main component (ABO ₃ ) in the dielectric ceramic composition is not particularly limited. For example, the main component (ABO) ₃ ) Judging by the peak intensity in the plane index (222) of the rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ when the peak intensity of the X-ray diffraction chart of the plane index (110) is 100. May be. This method is adopted in the embodiments described later. The dielectric ceramic composition containing 0.5 to 3 moles of Y ₂ Ti ₂ O ₇ with 100 moles of barium titanate BaTiO ₃ as the main component, the plane index (110) of barium titanate BaTiO ₃ The peak intensity in the plane index (222) of Y ₂ Ti ₂ O ₇ when the peak intensity of the X-ray diffraction chart is 100 is 1 to 5%. The effect of increasing the dielectric constant was confirmed when the peak intensity was in the range of 0.5% to 9.0%.

In addition, the main component (ABO ₃ ) and the segregated phase containing the rare earth element R are distinguished from the contrast of the reflected electron image using the YAG (yttrium / aluminum / garnet) detector attached to the scanning electron microscope (SEM). After deriving the ratio of the segregation phase containing the rare earth element R to the total area of the image obtained in step 1, the energy dispersive X-ray spectroscopy attached to the scanning transmission electron microscope (STEM) or scanning electron microscope (SEM) Using the apparatus (EDS), the presence or absence of R or the presence or absence of Ti is analyzed for the segregation phase containing the rare earth element R, so that the general formula R ₂ Ti _{2 of the} segregation phase containing the rare earth element R is analyzed. it may be determined as a proportion of the rare earth-titanium oxide represented by O _7.

Although the number of measurements is not particularly limited, it is preferable to have three or more fields of view because there is a local distribution of segregation phase even in one dielectric ceramic composition.

As described above, the content ratio of the rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ in the segregation phase containing Y is in a certain range, and thus has a high relative dielectric constant while firing at a low temperature. The dielectric ceramic composition can be obtained.

As described later, the existence state of the rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ described above can be realized by adding a compound containing specific Li and firing at a low temperature.

In the present embodiment, there is no particular limitation on the crystal grain size of the main component (ABO _3). What is necessary is just to determine suitably with respect to the thickness of the target dielectric material layer.

Internal electrode layer 3
The conductive material contained in the internal electrode layer 3 shown in FIG. 1 is not particularly limited, but a relatively inexpensive base metal can be used when the dielectric ceramic composition constituting the dielectric layer 2 has reduction resistance. . As the base metal used as the conductive material, Ni or Ni alloy is preferable. The internal electrode layer 3 may be formed using a commercially available electrode paste. What is necessary is just to determine the thickness of the internal electrode layer 3 suitably according to a use etc.

External electrode 4
The conductive material contained in the external electrode 4 shown in FIG. 1 is not particularly limited, but inexpensive Ni, Cu, and alloys thereof can be used in this embodiment. What is necessary is just to determine the thickness of the external electrode 4 suitably according to a use etc.

Manufacturing method of multilayer ceramic capacitor 1
In the multilayer ceramic capacitor 1 according to this embodiment, a green chip is produced by a normal printing method or a sheet method using a paste, and fired, and then printed or transferred an external electrode, similarly to a conventional multilayer ceramic capacitor. And then baked. Hereinafter, the manufacturing method will be specifically described.

First, a dielectric material for forming a dielectric layer is prepared, and this is made into a paint to prepare a dielectric layer paste.

As a dielectric material, first, an ABO ₃ material, a compound material containing an R element, and a Li compound are prepared. As these raw materials, oxides of the above-described components, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above oxides or composite oxides by firing, for example, carbonates, oxalates, nitrates, hydroxides, organometallic compounds, and the like may be appropriately selected and mixed for use.

In addition to the so-called solid phase method, the raw material of ABO ₃ can be produced by various methods such as those produced by various liquid phase methods (for example, oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.). What was manufactured can be used.

As the ABO ₃ raw material powder, those having an average particle diameter of 100 to 400 nm are preferably used. When the particle diameter is smaller than 100 nm, it becomes difficult to control crystal growth by firing, and thus the sintered body particle diameter tends to be non-uniform, and a desired dielectric constant cannot be obtained. On the other hand, if it is 400 nm or more, the temperature required for firing becomes high.

In addition, the method for measuring the particle diameter of the raw material powder is not particularly limited, and examples thereof include a laser diffraction / scattering method using information of diffraction / scattered light obtained according to the particle diameter.

The raw material of the compound containing the R element is not particularly limited, and may be a solid powder of a typical R ₂ O ₃ oxide or a solution. For example, R element alkoxides, complexes, and salts added to a solvent may be used.

Similarly, the raw material for the Li compound is not particularly limited, and may be a solid powder or a solution. When using a solid material, it is desirable to use at least an average particle diameter equal to or less than that of the ABO ₃ raw material powder. Further, it is desirable to add in the range of 0.5 to 10 mol% in terms of Li atom.

The Li compound is preferably an oxide Li _a M _b O _c containing Li and another cation M. The cation M in Li _a M _b O _c may be any of B, Al, Si, P, Ti, V, Mn, Co, Zr, Mo, and W, and Ti is suitable for obtaining.

Further, when the dielectric layer contains components other than the above components, raw materials for the components are prepared. As these raw materials, oxides of these components, mixtures thereof, composite oxides, or various compounds that become the oxides or composite oxides described above by firing can be used. Moreover, you may use a solution raw material.

When an Si compound is used as a raw material, it may be an oxide or a complex oxide, but the addition amount is preferably 0.8 mol% or less in terms of Si atoms.

Next, in this embodiment, a raw material of ABO _3, a raw material of an R element compound, and a Li compound are mixed to obtain a solution-like raw material mixture. In this raw material mixture, the ABO ₃ raw material, the R element oxide raw material, and the Li compound are uniformly dispersed in the solvent. The mixing is performed for about 4 to 48 hours using, for example, a ball mill. At this time, a dispersant may be added.

The obtained raw material mixture is dried. In the raw material mixture after drying, the surface of the ABO ₃ particles is covered with a compound of R element and a Li compound. That is, the R element or the like is physically or chemically adsorbed on the ABO ₃ particles and coats the particle surface.

The drying method is not particularly limited, and may be appropriately selected from stationary drying, spray drying, freeze drying, and the like. Further, the drying temperature is not particularly limited as long as the solvent can be removed from the raw material mixture.

Subsequently, the dried raw material mixture may be used as a dielectric raw material, or may be further heat-treated. When heat treatment is performed, the R element compound and the Li compound coated on the surface of the ABO ₃ particles are more firmly fixed to the particles. For this heat treatment, for example, a rotary kiln, a tunnel furnace, or a batch furnace can be used. The holding temperature in the heat treatment is preferably in the range of 300 to 800 ° C. The holding time is preferably in the range of 0 to 4 hours. In addition, you may perform simultaneously drying and heat processing of a raw material mixture. Examples of the method performed simultaneously include a spray pyrolysis method.

Since the raw material mixture is agglomerated after the heat treatment, the raw material mixture may be crushed to an extent that loosens the aggregation. This crushing may be performed at the time of preparing a dielectric layer paste described later.

The average particle size of the raw material mixture after the heat treatment is usually about 0.1 to 1 μm. Next, the obtained heat-treated material mixture (dielectric material) is made into a paint to prepare a dielectric layer paste. At this time, raw materials of other components not added as solution raw materials may be added. *

The internal electrode layer paste is prepared by kneading the above-described conductive materials made of various conductive metals and alloys, or various oxides, organometallic compounds, resinates, and the like that become the above-mentioned conductive materials after firing.

The external electrode paste may be prepared in the same manner as the internal electrode layer paste described above.

A green sheet is formed using the dielectric layer paste, and the internal electrode layer paste is printed thereon, then, these are stacked, and cut into a predetermined shape to obtain a green chip.

Before firing, the green chip is treated to remove the binder, and then the green chip is fired. In firing, the rate of temperature rise is preferably 200 ° C./hour or more. The holding temperature at the time of firing is preferably 1100 ° C. or less, more preferably 1000 to 1100 ° C., and the holding time is preferably 2 hours or less.

The firing atmosphere is preferably a reducing atmosphere. As the atmosphere gas, for example, a mixed gas of N ₂ and H ₂ can be used by humidification.

In addition, the oxygen partial pressure during firing may be appropriately determined according to the type of the conductive material in the internal electrode layer paste, but when a base metal such as Ni or Ni alloy is used as the conductive material, The oxygen partial pressure is preferably 10 ⁻¹⁴ to 10 ⁻¹⁰ MPa. The temperature lowering rate during firing is preferably 50 to 500 ° C./hour.

It is preferable to anneal the capacitor element body after firing in a reducing atmosphere. Annealing is a process for re-oxidizing the dielectric layer, and thereby the IR life (insulation resistance life) can be remarkably increased, so that the reliability is improved.

The oxygen partial pressure in the annealing atmosphere is preferably 10 ⁻⁹ to 10 ⁻⁵ MPa. The holding temperature during annealing is preferably 1000 ° C. or less, particularly 900 to 1000 ° C. Note that annealing may be composed of only a temperature raising process and a temperature lowering process. That is, the temperature holding time may be zero.

The binder removal treatment, firing and annealing may be performed continuously or independently.

The capacitor element body obtained as described above is subjected to end surface polishing, for example, by barrel polishing or sand blasting, and the external electrode paste is applied and baked to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

The multilayer ceramic capacitor of this embodiment manufactured in this way is mounted on a printed circuit board by soldering or the like and used for various electronic devices.

In the present embodiment, R ₂ is selected by selecting a suitable oxide Li _a M _b O _c containing Li and another cation M, and setting other component additives and firing conditions in the above ranges. Since Ti ₂ O ₇ can be generated, a dielectric ceramic composition having a high dielectric constant can be realized even when fired at a low temperature.

The process in which the relative permittivity becomes high even when fired at a low temperature due to the generation of R ₂ Ti ₂ O ₇ is not necessarily clear, but can be considered as follows, for example. Compared with the case where a large amount of R ₂ O ₃ is present as the second phase, when R ₂ Ti ₂ O ₇ is produced, the liquid phase is easily formed at a low temperature, and the diffusion of the additive element proceeds. As a result, the low dielectric constant components remaining at the grain boundaries and grain boundary triple points are reduced, so that it is considered that the grain boundaries become thinner and the relative dielectric constant becomes higher than in the case of conventional low-temperature firing.

The embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

For example, in the above-described embodiment, a multilayer ceramic capacitor is exemplified as an electronic component to which the dielectric ceramic composition according to the present invention is applied. However, as an electronic component to which the dielectric ceramic composition according to the present invention is applied, a multilayer ceramic capacitor is used. The present invention is not limited to a capacitor, and any capacitor may be used as long as it has a dielectric layer having the above configuration.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

Example 1
First, BaTiO ₃ powder was prepared as a raw material for ABO ₃ , and Y ₂ O ₃ , MgCO ₃ , MnCO ₃ , V ₂ O ₅ , and CaSiO ₃ powders were prepared as subcomponent raw materials. In addition, MgCO ₃ and MnCO ₃ are contained in the dielectric ceramic composition as MgO and MnO after firing.

Furthermore, Li ₂ CO ₃ , LiOH, LiBO ₂ , Li ₂ B ₄ O ₇ , LiPO ₂ , Li ₃ PO ₄ , LiMn ₂ O ₄ , Li ₄ Ti ₅ O ₁₂ , LiCoO ₂ are used as raw materials for subcomponents containing Li. , Li ₂ O, Li ₂ SiO ₃ , Li ₂ TiO ₃ , LiAlO ₂ , LiZrO ₃ , Li ₂ MoO ₄ , LiVO ₃ , and LiCl powders were prepared. Each compound corresponds to Sample Nos. 2 to 17 in Table 1, and in the preparation of the dielectric material, only one of them was selected and used.

Next, the BaTiO ₃ powder, the subcomponent raw material, and the subcomponent raw material containing Li were mixed for 16 hours using a ball mill to prepare a raw material mixture. The obtained raw material mixture was dried at 150 ° C. and then heat-treated at 600 ° C. for 2 hours. The raw material mixture after the heat treatment was used as a dielectric raw material.

In addition, the addition amount of each subcomponent is 4.0 mol of the subcomponent raw material containing Li in terms of each atom with respect to 100 mol of BaTiO ₃ as the main component in the fired dielectric ceramic composition, Y ₂ O ₃ is 1.0 mol, MgO is 0.5 mol, MnO is 0.2 mol, V ₂ O ₅ is 0.1 mol, CaO is 0.8 mol, and SiO ₂ is 0.8 mol. I made it.

Next, the obtained dielectric material: 100 parts by mass, polyvinyl butyral resin: 10 parts by mass, dioctyl phthalate (DOP) as a plasticizer: 5 parts by mass, and alcohol as a solvent: 100 parts by mass with a ball mill The mixture was made into a paste to obtain a dielectric layer paste.

In addition to the above, Ni particles: 44.6 parts by mass, terpineol: 52 parts by mass, ethyl cellulose: 3 parts by mass, and benzotriazole: 0.4 parts by mass are kneaded by three rolls, and slurry To prepare an internal electrode layer paste.

A green sheet was formed on the PET film using the dielectric layer paste prepared above. Next, the electrode layer was printed in a predetermined pattern using the internal electrode layer paste thereon, and then the sheet was peeled off from the PET film to produce a green sheet having the electrode layer. Next, a plurality of green sheets having electrode layers were laminated and pressure-bonded to obtain a green laminated body, and the green laminated body was cut into a predetermined size to obtain a green chip.

The obtained green chip was subjected to binder removal processing, firing and annealing under the following conditions to obtain a sintered body serving as an element body.

The binder removal conditions were as follows: temperature increase rate: 20 ° C./hour, holding temperature: 300 ° C., temperature holding time: 8 hours, atmosphere: in air.

The firing conditions were temperature rising rate: 300 ° C./hour, holding temperature: 1100 ° C., temperature holding time: 2 hours, and cooling rate: 300 ° C./hour. The atmospheric gas was a humidified N ₂ + H ₂ mixed gas, and the oxygen partial pressure was 10 ⁻¹² MPa.

The annealing conditions were as follows: heating rate: 300 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 300 ° C./hour, atmospheric gas: humidified N ₂ gas (oxygen partial pressure: 10 ⁻⁷ MPa). A wetter was used for humidifying the atmospheric gas during firing and annealing.

Next, after polishing the end face of the obtained sintered body with sand blasting, a Cu paste was applied as an external electrode and baked to obtain a sample of the multilayer ceramic capacitor shown in FIG. The size of the obtained capacitor sample is 3.2 mm × 1.6 mm × 0.6 mm, the thickness of the dielectric layer is 1.4 μm, the thickness of the internal electrode layer is 1.1 μm, and the dielectric sandwiched between the internal electrode layers The number of layers was 200.

For each of the obtained capacitor samples were evaluated for the content of _Y 2 _Ti 2 _{O 7} by X-ray diffractometry. Next, the relative dielectric constant was measured by the method shown below. Moreover, the average thickness of the grain boundary at this time was confirmed by the following method.

Evaluation of Y ₂ Ti ₂ O ₇ Content by X-ray Diffraction Method First, the obtained capacitor sample was pulverized and then analyzed from the diffraction peak of 2θ = 20 to 100 ° by X-ray diffraction method (Cu-Kα). The crystal phase was identified. Then, the plane index (222 of _Y 2 _Ti 2 _{O 7} in the case where the peak intensity of X-ray diffraction chart of the plane index of BaTiO ₃ the ratio of _Y 2 _Ti 2 _{O 7} in the dielectric (110) and 100 ) Obtained as a percentage of the peak intensity ratio was taken as the Y ₂ Ti ₂ O ₇ content.

Dielectric constant ε
The relative dielectric constant ε was measured on a capacitor sample at a reference temperature of 25 ° C. using a digital LCR meter (4274A manufactured by YHP) under the conditions of a frequency of 1 kHz and an input signal level (measurement voltage) of 1.0 Vrms. Calculated from the electric capacity (no unit). In this example, it is preferable that the relative dielectric constant is high, and 3500 or more is good, and 4000 or more is particularly good. The results are shown in Table 1.

Evaluation of Grain Boundary Thickness From the obtained capacitor sample, a flake sample was prepared using FIB. This was observed with a scanning transmission electron microscope (STEM), and the thickness at which the grain boundary was perpendicular to the electron beam was measured with the adjacent crystal grain as the grain boundary. Ten such grain boundaries were searched and the thickness was measured to obtain the average grain boundary thickness.

Table 1 summarizes the relationship between the content of Y ₂ Ti ₂ O ₇ and the relative dielectric constant when various Li compounds are added and fired at a low temperature. Sample No. 1 of the comparative example was a conventional material fired at 1240 ° C. without adding a Li compound, and had a relative dielectric constant of 4500. For sample numbers 2 to 16, Li compounds were added and baked at 1100 ° C. Among these, in the sample numbers 2 to 5 of the comparative examples, the content of Y ₂ Ti ₂ O ₇ is 0%, and the relative dielectric constant is as low as 1500 to 2400. The average grain boundary thickness was 5.0 nm for material number 1 and 4.6 nm for material number 2.

On the other hand, it was confirmed that the sample numbers 6 to 16 of the examples contained Y ₂ Ti ₂ O ₇ . Among these, for sample numbers 7 to 16, the content of Y ₂ Ti ₂ O ₇ was 0.5% or more, and the relative dielectric constant was 3500 or more. In particular, for the sample numbers 13 to 16, the Y ₂ Ti ₂ O ₇ content was as high as 1.8 to 3.4%, and the relative dielectric constant was 4200 to 4500, which was particularly good results. Sample number 17 was obtained by adding the same Li compound as sample number 16 and firing at 1240 ° C., but the content ratio and relative dielectric constant of Y ₂ Ti ₂ O ₇ were the sample numbers fired at 1100 ° C. It was almost equivalent to 16. The average grain boundary thickness of material number 13 was 1.5 nm, and the grain boundary thickness of material number 16 was 1.2 nm.

From Table 1, it was confirmed that a good dielectric constant was obtained when the content of Y ₂ Ti ₂ O ₇ was 0.5% or more. Further, when Li _a M _b O _c is used as an oxide containing Li and another cation M, M is B, Al, Si, P, Ti, V, Mn, Co, Zr, Mo, and It was confirmed that by selecting a Li compound selected from W, a favorable dielectric constant can be obtained because Y ₂ Ti ₂ O ₇ is contained. In particular, it was confirmed that by selecting M = Ti, the content of Y ₂ Ti ₂ O ₇ was increased and the relative dielectric constant was the highest.

Example 2
Sample Nos. 19 to 26 in Table 2 were prepared through the same steps as in Example 1 with samples having the same composition as Sample No. 16 in Example 1 but only the addition amount of Li ₄ Ti ₅ O ₁₂ changed. The relationship between the Y ₂ Ti ₂ O ₇ content and the relative dielectric constant was evaluated. Sample Nos. 27 to 32 are samples having the same composition as Sample No. 16 of Example 1 but with the amount of SiO ₂ added being changed through the same steps as in Example 1. Y ₂ Ti ₂ O The relationship between the content of ₇ and the relative dielectric constant was evaluated. In addition, the amount of Li ₄ Ti ₅ O ₁₂ in Table 2 indicates the amount added in terms of Li atom with respect to 100 mol of BaTiO _{3 as the} main component. Similarly, the amount of SiO ₂ indicates the amount added in terms of Si atoms with respect to 100 mol of BaTiO _{3 as the} main component.

From Table 2 and FIG. 3, sample number 18 as a comparative example is a case where the amount of addition of Li ₄ Ti ₅ O ₁₂ is 0.25 mol, but the content of Y ₂ Ti ₂ O ₇ is 0% and the relative dielectric constant Was as low as 2600. On the other hand, sample numbers 19 to 25 in Table 2 in which the amount of Li ₄ Ti ₅ O ₁₂ added is 0.5 to 10 mol have a Y ₂ Ti ₂ O ₇ content of 2.7 to 8.2%. The relative dielectric constant was as good as 3500 or more. In particular, Sample Nos. 19 to 22 and Sample No. 16 in Table 2 where the addition amount of Li ₄ Ti ₅ O ₁₂ is 0.5 to 4 mol are Y ₂ Ti ₂ O ₇ contents of 2.7 to 3.4%. The relative dielectric constant was particularly good at 4000 or more. Sample No. 26 was a case where the addition amount of Li ₄ Ti ₅ O ₁₂ was 12 mol, but the relative dielectric constant was as low as 2600 even if the content of Y ₂ Ti ₂ O ₇ was 10.2%.
The average grain boundary thickness of Sample No. 18 was 3.5 nm, which was thicker than that of the sample of Example 1.

From Table 2 and FIG. 3, it was found that when the added amount of Li ₄ Ti ₅ O ₁₂ is 0.5 to 11 mol, a favorable dielectric constant of 3500 or more is obtained. Further, from Table 2, it was confirmed that a good dielectric constant was obtained when the content of Y ₂ Ti ₂ O ₇ was 10% or less.

From Table 1, FIG. 2 and Table 2, it was confirmed that a favorable result was obtained with a relative dielectric constant of 3500 or more when the content of Y ₂ Ti ₂ O ₇ was in the range of 0.5% to 9.0%. .

Sample numbers 16 and 27 to 31 in Table 2 have a Y ₂ Ti ₂ O ₇ content of 3.1 to 3.8% in a range of 0.2 to 1.2 mol of SiO ₂ added, The relative dielectric constant was as good as 3500 or more. In particular, Sample Nos. 27 to 29 have a Y ₂ Ti ₂ O ₇ content of 3.6 to 3.8% when the SiO ₂ addition amount is in the range of 0.2 to 0.8 mol, and have a relative dielectric constant. Was very good at 4500 or more.

From Table 2 and FIG. 4, it was confirmed that a very good relative dielectric constant was obtained when the amount of SiO ₂ added was 0.8 mol or less. Further, the correlation between the added amount of SiO _{2 and} the content of Y ₂ Ti ₂ O ₇ was weak, and the relative dielectric constant tended to increase when the amount of SiO ₂ was reduced.

By firing at a low temperature without reducing the dielectric constant, a thin electrode layer with good lineability and a dielectric layer with a uniform particle size can be obtained. As a manufacturing method for high-capacity, thin-layer multilayer ceramic capacitors Applicable. At the same time, it is possible to achieve significant manufacturing cost reduction and CO ₂ emission reduction as compared with the case of firing at a high temperature.

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

Claims (3)

1. Compound represented by general formula ABO ₃ (A is at least one element selected from Ba, Ca and Sr, and B is at least one element selected from Ti and Zr) and has a perovskite crystal structure α and a compound β consisting of a rare earth titanium oxide represented by the general formula R ₂ Ti ₂ O ₇ (wherein R element is Sc, Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and A dielectric ceramic composition comprising: at least one element selected from Lu) and a grain boundary formed between particles of the compound α.
2. The peak intensity at the surface index (222) in the X-ray diffraction chart of the compound β is 0.5 to 9.0% with respect to the peak intensity at the surface index (110) in the X-ray diffraction chart of the compound α. The dielectric ceramic composition according to claim 1, wherein:
3. A ceramic electronic component having a dielectric layer composed of the dielectric ceramic composition according to claim 1 and an electrode layer.

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