JP2010024126A - Dielectric ceramic composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition having long life under high temperature load and excellent DC bias characteristics. <P>SOLUTION: The dielectric ceramic composition containing BaTiO<SB>3</SB>and containing BaZrO<SB>3</SB>and rare earth (R) oxide as auxiliary components, has a surface diffusive particle comprising a non-diffusive phase and a diffusive phase. The concentration of Zr and R are measured to a micro-region in the diffusive phase, and an aggregate of a micro-region where the concentration of R is larger than the concentration of Zr is defined as a first region and an aggregate of a micro-region where the concentration of Zr is higher than the concentration of R is defined as a second region. In the first region, a region where the concentration of Zr is ≥1.0 atom% and <2.0 atom% and the concentration of R is ≥2.0 atom% and <3.5 mol% is defined as a first diffusive phase and in the second region, a region where the concentration of Zr is ≥2.0 atom% and <4.0 atom% and the concentration of R is ≥1.0 atom% and <2.0 atom% is defined as a second diffusive phase, the first diffusive phases 20b-24b exist nearer to the non-diffusive phases 20a-24a than the second diffusive phases 20c-24c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic composition, and more particularly to a dielectric ceramic composition that is suitably used for medium to high voltage applications having a relatively high rated voltage.

  In recent years, there has been a high demand for downsizing of electronic components due to higher density of electronic circuits, and the use of multilayer ceramic capacitors has rapidly increased in size and capacity, and applications have been expanded.

  For example, medium and high voltage capacitors used in equipment such as ECM (engine electric computer module), fuel injection device, electronic control throttle, inverter, converter, HID headlamp unit, hybrid engine battery control unit, digital still camera, etc. It must be usable even under high electric field strength.

  Therefore, when using a medium- or high-voltage capacitor for the above equipment, heat generation caused by high-density mounting of electronic components and the harsh use environment typified by automotive electronic components are problematic, so it can be used under high voltage. In addition, high reliability is desired even at high temperatures, for example, at 100 ° C. or higher.

  For example, Patent Document 1 proposes a multilayer ceramic capacitor composed of dielectric particles having a core-shell particle structure, in which the shell portion is composed of a plurality of portions having different diffusion components.

  However, in the multilayer ceramic capacitor disclosed in Patent Document 1, the specific components of the shell portion, the content, the thickness (area), etc. are not disclosed, and there is no description about the relationship between these and the obtained characteristics. It has not been.

A multilayer ceramic capacitor using a dielectric ceramic composition mainly composed of barium titanate exhibiting ferroelectricity is accompanied by an electrostriction phenomenon in which mechanical strain is generated when an electric field is applied. The vibration sound generated by the vibration due to the electrostriction phenomenon may be in a sound range that is unpleasant to humans, and countermeasures have been required.
Japanese Patent Laid-Open No. 2001-240466

  The present invention has been made in view of such a situation, and a dielectric ceramic composition capable of improving the high temperature load life and the DC bias characteristics while maintaining the relative dielectric constant and the amount of electrostriction when a voltage is applied satisfactorily. The purpose is to provide.

  As a result of intensive investigations to achieve the above object, the present inventors have found that a dielectric ceramic composition having a main component containing barium titanate and a specific subcomponent has an electrostriction amount when a voltage is applied. Found that can be lowered. Furthermore, in the dielectric particles constituting the dielectric ceramic composition, the high temperature load life and the DC bias characteristics can be improved by controlling the existence state of a region where a specific amount of a specific subcomponent exists. As a result, the present invention has been completed.

That is, the dielectric ceramic composition according to the present invention is
A main component comprising barium titanate;
As a subcomponent, BaZrO ₃ and
R element oxide (wherein R element is at least selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) 1), and a dielectric ceramic composition comprising:
The dielectric ceramic composition has surface diffusing particles having a surface diffusing structure comprising a non-diffusing phase and a diffusing phase that is present around the non-diffusing phase and includes at least a Zr element and the R element. And
A content ratio of the Zr element and the R element is measured with respect to a micro area in the diffusion phase, and a set of micro areas in which the content ratio of the R element is equal to or more than the content ratio of the Zr element When the second region is a set of minute regions in which the content ratio of the Zr element is larger than the content ratio of the R element,
In the first region, a region where the content ratio of the Zr element is 1.0 atom% or more and less than 2.0 atom% and the content ratio of the R element is 2.0 atom% or more and less than 3.5 atom% is defined as a first diffusion phase. age,
In the second region, a region in which the content ratio of the Zr element is 2.0 atom% or more and less than 4.0 atom% and the content ratio of the R element is 1.0 atom% or more and less than 2.0 atom% is a second diffusion phase. age,
The first diffusion phase is present in the vicinity of the non-diffusion phase, and the entire periphery of the first diffusion phase is a first region other than the first diffusion phase, and a first region other than the first diffusion phase. One region and the second region, or a first region other than the first diffusion phase, the second region, and the non-diffusion phase are covered.

  In the present invention, in the surface diffusion particles having a non-diffusion phase and a diffusion phase, the diffusion phase is divided into two regions depending on the content ratio of the Zr element and the R element. Furthermore, in these two regions, the region in which the contents of R element and Zr element are in the above range is divided into a first diffusion phase and a second diffusion phase. The first diffusion phase is present in the dielectric particles (surface diffusion particles) as described above. That is, the first diffusion phase tends to exist in a region closer to the non-diffusion phase (near the center of the dielectric particles) than the second diffusion phase.

  According to the present invention, by controlling the content ratio of the Zr element and the R element in the first diffusion phase and the second diffusion phase and the existence state of the first diffusion phase as described above, the relative permittivity and the electrostrictive characteristics are obtained. It is possible to obtain a dielectric ceramic composition having improved DC bias characteristics and high temperature load life while maintaining good.

  Preferably, in the dielectric ceramic composition, the ratio of the area occupied by the first diffusion phase to A [%] and the ratio of the area occupied by the second diffusion phase to the field area of 3 × 3 μm is B [ %], 1.0 ≦ A <16.0% and 60.0 ≦ (A + B) <70.0%.

  By setting the ratio (area ratio) of each area within the above range, the high temperature load life can be further improved while maintaining the relative dielectric constant, the DC bias characteristic, and the electrostrictive characteristic well.

  The electronic component having a dielectric layer for which the dielectric ceramic composition according to the present invention is preferably used is not particularly limited, but includes a multilayer ceramic capacitor, a piezoelectric element, a chip inductor, a chip varistor, a chip thermistor, a chip resistor, and other surfaces. A mounting (SMD) chip type electronic component is exemplified.

  According to the present invention, there can be obtained a dielectric ceramic composition in which the existence state of the first diffusion phase and the second diffusion phase defined by the content ratio of the R element and the Zr element in the surface diffusion particles is controlled as described above. By doing so, the dielectric ceramic composition according to the present invention exhibits good DC bias and high temperature load life, and is suitably used for medium to high voltage applications having a relatively high rated voltage.

  Furthermore, by setting the area occupied by the first diffusion phase and the second diffusion phase within the above range, in addition to the above effects, it is possible to obtain a dielectric ceramic composition that is further excellent in high temperature load life.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a surface diffusion particle according to an embodiment of the present invention,
FIG. 3 is a schematic diagram for explaining a method of measuring a boundary between a non-diffusible phase and a diffused phase;
FIG. 4A is a mapping image for each phase after the principal component analysis is performed on the sample according to the embodiment of the present invention, and FIG. 4B is the main image regarding the sample according to the comparative example of the present invention. It is a figure which shows the mapping image about each phase after performing a component analysis.

Multilayer ceramic capacitor 1
As shown in FIG. 1, a multilayer ceramic capacitor 1 according to an embodiment of the present invention 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 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.

  The internal electrode layers 3 are laminated so that the end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor element body 10. The pair of external electrodes 4 are formed at both ends of the capacitor element body 10 and connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

Dielectric layer 2
The dielectric layer 2 contains the dielectric ceramic composition of the present invention.
The dielectric ceramic composition of the present invention includes a main component containing barium titanate, BaZrO ₃ as a subcomponent, and an oxide of an R element as a subcomponent (provided that the R element is Sc, Y, La, Ce) , Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu).

Barium titanate contained as a main component is represented by, for example, a composition formula (BaO) _x · TiO ₂ . X in the composition formula represents the ratio of A site to B site of barium titanate, and x is preferably 1.000 ≦ x <1.010, more preferably 1.000 ≦ x ≦ 1. .006.

  If x is too small, the relative permittivity tends to decrease and the high temperature load life tends to decrease. On the other hand, when x is too large, the electrostrictive characteristics and the DC bias characteristics tend to be lowered.

BaZrO ₃ mainly has an effect of suppressing the ferroelectricity of the main component, barium titanate. The content of BaZrO ₃ is preferably 10 mol or more, more preferably 10 to 15 mol in terms of BaZrO _{3 with} respect to 100 mol of the main component. When the content of BaZrO ₃ is too small, the electrostrictive characteristics and the DC bias characteristics tend to deteriorate, while when too large, the relative permittivity tends to decrease.

The oxide of R element mainly has an effect of suppressing the ferroelectricity of the main component barium titanate. The content of the oxide of R element is preferably 4 to 6 mol, more preferably 4.5 to 5.5 mol in terms of R ₂ O _{3 with} respect to 100 mol of the main component. When the content of the R element oxide is too small, the electrostrictive characteristics and the DC bias characteristics are deteriorated and the high temperature load life tends to be deteriorated. On the other hand, if the amount is too large, the relative permittivity tends to decrease. The R element constituting the oxide of the R element is preferably at least one selected from Gd, Sm, Tb, Dy, Ho, and Y. Among these, Gd is particularly preferable because of excellent temperature characteristics.

In the present embodiment, other subcomponents may be added in addition to BaZrO ₃ and the oxide of the R element as necessary. Such subcomponents include, for example, an oxide of M element (where M element is at least one selected from Mn, Ni, Cr, Co, and Fe), an oxide of Mg, an oxide of Si, and the like. Is mentioned.

  The M element oxide has the effect of improving the reduction resistance of the dielectric ceramic composition. Further, the Mg oxide has the effect of stabilizing the capacity-temperature characteristics while maintaining other characteristics favorable. Si oxides mainly have a role as a sintering aid.

When these oxides are used, the content of the M element oxide is 0.1% in terms of MnO, NiO, CrO _3/2 , CoO _4/3 or FeO _{3/2 with} respect to 100 mol of the main component. It is preferable that it is 5-1.5 mol. Further, the Mg oxide is preferably 2.7 to 5.7 mol in terms of MgO with respect to 100 mol of the main component. Further, oxides of Si, relative to 100 moles of the main component in terms of SiO ₂ is preferably 3.0 to 3.9 moles.

Structure of Dielectric Particles In the present invention, the dielectric particles contained in the dielectric layer 2 are present as surface diffusion particles 20 having a surface diffusion structure as shown in FIG. The surface diffusing particles 20 are present in a non-diffusing phase 20a containing barium titanate as a main component and a non-diffusing phase 20a around the non-diffusing phase 20a, and a diffusion phase (20b) in which components other than barium titanate are diffused in the barium titanate. 20c). Since the non-diffusing phase 20a is substantially made of barium titanate, it exhibits ferroelectric characteristics. On the other hand, in the diffusion phase (20b, 20c), since the element added as the auxiliary component is mainly diffused (solid solution) in the barium titanate, the ferroelectric characteristics are lost, and the paraelectric characteristics. Indicates.

  In the present invention, Zr and R elements are present in the diffusion phase. The diffusion phase includes a first region in which the R element content is greater than the Zr element content, and the Zr element content is the R element. And a second region larger than the content of. The first region has a first diffusion phase in which the contents of Zr and R elements in the first region are in a specific range. Further, the second region has a second diffusion phase in which the contents of Zr and R elements in the second region are in a specific range.

When the dielectric layer 2 contains subcomponents other than the BaZrO ₃ and R oxides, these subcomponent elements are present in the diffusion phase (first region, second region). May be. Further, in addition to the first diffusion phase, the first region may have a region (phase) in which the content ratio of the Zr element and the R element is outside the above range, and the second region includes the first region. In addition to the two diffusion phases, it may have a region (phase) in which the content ratio of the Zr element and the R element is outside the above range.

  In the present invention, the first diffusion phase exists in the vicinity of the non-diffusion phase 20a. In addition, the entire periphery of the first diffusion phase is covered with the first region other than the first diffusion phase. Alternatively, the entire periphery of the first diffusion phase is covered with the first region and the second region other than the first diffusion phase. Alternatively, the entire periphery of the first diffusion phase is covered with the first region, the second region, and the non-diffusion phase 20a other than the first diffusion phase.

  In the present embodiment, in order to explain the existence state of the first diffusion phase, in FIG. 2, the first region and the first diffusion phase match, and the second region and the second diffusion phase match. The case is illustrated. That is, the case where the entire periphery of the first diffusion phase is covered with the second region and the case where the entire periphery of the first diffusion phase is covered with the second region and the non-diffusion phase 20a are illustrated.

  In the surface diffusion particle 20 of FIG. 2, the first diffusion phase 20b covers the entire periphery of the non-diffusion phase 20a, and the second diffusion phase 20c covers the outer periphery of the first diffusion phase 20b. This corresponds to a case where the entire periphery of the first diffusion phase 20b is covered with the second region (second diffusion phase 20b) and the non-diffusion phase 20a.

  In the surface diffusion particle 21 of FIG. 2, the first diffusion phase 21b covers a part of the periphery of the non-diffusion phase 21a, and the second diffusion phase 21c is formed around the non-diffusion phase 21a and the first diffusion phase 21b. It is configured to cover a part. This also corresponds to the case where the entire periphery of the first diffusion phase 21b is covered with the second region (second diffusion phase 21b) and the non-diffusion phase 21a.

  Further, in the surface diffusion particle 22 of FIG. 2, the first diffusion phase 22b exists without covering the periphery of the non-diffusion phase 22a, and the second diffusion phase 22c is the whole of the non-diffusion phase 22a and the first diffusion phase 22b. It is configured to cover the surroundings. This corresponds to the case where the entire periphery of the first diffusion phase 22b is covered with the second region (second diffusion phase 22b).

  Note that the first diffusion phase and the second diffusion phase may exist as a plurality of separated phases. Therefore, the above configurations may be combined. For example, in the surface diffusion particle 23 of FIG. 2, the entire periphery of the first diffusion phase 23b is covered with the second region (second diffusion phase 23b) and the non-diffusion phase 23a, and the first diffusion phase 23b. This corresponds to the case where the entire periphery of the region is covered with the second region (second diffusion phase 23b) and the combination.

  Furthermore, as shown in the surface diffusion particle 24 of FIG. 2, a configuration in which a part of the periphery of the non-diffusion phase 24a is not covered with the first diffusion phase 24b and the second diffusion phase 24c may be employed.

  Among the above configurations, like the surface diffusion particle 20, the first diffusion phase 20b covers the entire periphery of the non-diffusion phase 20a, and the second diffusion phase 20c covers the entire periphery of the first diffusion phase 20b. Preferably it is. That is, the first diffusion phase is present in the vicinity of the non-diffusion phase rather than the second diffusion phase. Furthermore, in the dielectric particles, the first diffusion phase is preferably present inside the second diffusion phase (near the center of the dielectric particles).

  The content ratio of the Zr element in the first diffusion phase 20b is 1.0 ≦ Zr <2.0 atom%, preferably 1.6 to 1.9 atom%. Further, the content ratio of the R element in the first diffusion phase 20b is 2.0 ≦ R <3.5 atom%, preferably 2.6 to 3.3 atom%.

  On the other hand, the content ratio of the Zr element in the second diffusion phase 20c is 2.0 ≦ Zr <4.0 atom%, preferably 2.5 to 3.6 atom%. Further, the content ratio of the R element in the second diffusion phase 20c is 1.0 ≦ R <2.0 atom%, and preferably 1.2 to 1.6 atom%.

  From the above, the Zr element content in the first diffusion phase 20b is smaller than the Zr element content in the second diffusion phase 20c, whereas the R element content in the first diffusion phase 20b is: It is larger than the content of the R element in the second diffusion phase 20c. Thus, by controlling the diffusion state of the Zr element and the R element, it is possible to improve the DC bias characteristic and the high temperature load life while maintaining the specific dielectric constant and the electrostrictive characteristic well.

  When the contents of the Zr element and the R element in the first diffusion phase 20b and the second diffusion phase 20c are outside the above ranges, the DC bias characteristics and the high temperature load life tend to be deteriorated.

  Although it does not restrict | limit especially as a method of measuring the content rate of Zr element and the content rate of R element with respect to the micro area | region in a diffusion phase (20b, 20c), For example, it can measure by the method shown below.

In the present embodiment, a predetermined number of dielectric particles are observed with a scanning transmission electron microscope (STEM), and an attached energy dispersive X-ray spectrometer is used to detect the Zr element on a minute region in the diffusion phase. The content ratio and the content ratio of the R element can be measured. First, Principal Component Analysis (PCA) is performed on a spectrum obtained by energy dispersive X-ray spectroscopy (EDS) performed on dielectric particles. That is, the obtained spectrum is subjected to multivariate analysis, and a spectrum having a similar shape is defined as one phase and separated into a plurality of phases. By performing image processing on the mapping image obtained by this analysis, phases (first diffusion phase and second diffusion phase) in which the content ratio of the Zr element and the content ratio of the R element are in the above-described ranges can be separated.
Note that the size of the minute region in the diffusion phase is not particularly limited, and usually depends on the beam diameter of the measuring instrument.

  Furthermore, in this embodiment, the area which each area | region obtained above occupies is calculated. Specifically, the ratio (area ratio) of each region to the area having a field of view of 3 × 3 μm is calculated at a magnification of 40000 times. When the area ratio of the first diffusion phase 20b is A and the area ratio of the second diffusion phase 20c is B, preferably 1.0 ≦ A <16.0%, more preferably 5.0 ≦ A ≦ 10.4. %. Further, it is preferably 60.0 ≦ (A + B) <70.0%, more preferably 64.2 ≦ (A + B) ≦ 67.0%.

  When A and (A + B) are within the above ranges, the high temperature load life can be further improved.

  The region of the non-diffused phase 20a and the region of the diffused phase (20b, 20c) in the dielectric particles can be clearly distinguished, for example, as follows. First, as described above, the dielectric particles are observed with a scanning transmission electron microscope (STEM) and measured using an attached energy dispersive X-ray spectrometer. Specifically, as shown in FIG. 3, point analysis is performed on a straight line passing through the approximate center of the surface diffusion particle 20, and the particle (non-diffusion) is obtained from the concentration distribution of the obtained R element (the same applies to the Zr element). The average concentration of the R element in the phase 20a and the diffusion phases 20b, 20c) is calculated.

  Then, the mapping image of the R element with respect to the surface diffusing particles 20 is subjected to image processing to be divided into a region exceeding 1/3 of the average concentration of R element and a region not exceeding 1/3 of the average concentration. That is, a region having an average concentration exceeding 1/3 is defined as a diffusion phase (20b, 20c), and a region having an average concentration of 1/3 or less is defined as a non-diffusion phase 20a. In this way, in a bright field image by a scanning transmission electron microscope (STEM), the boundary between the non-diffusing phase 20a and the diffusing phase (20b, 20c) of the particle observed as a difference in contrast is in good agreement. Become.

  The average particle diameter of the dielectric particles constituting the dielectric layer 2 shown in FIG. 1 may be determined according to the thickness of the dielectric layer 2 and the like, but in the present embodiment, it is 1.5 μm or less. preferable.

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 because the constituent material of the dielectric layer 2 has reduction resistance. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more elements selected from Mn, Cr, Co and Al, and the Ni content in the alloy is preferably 95% by weight or more. In addition, in Ni or Ni alloy, various trace components, such as P, may be contained about 0.1 wt% or less. 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, or alloys thereof can be used in the present invention. 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 The multilayer ceramic capacitor 1 of the present embodiment is the same as a conventional multilayer ceramic capacitor. After producing a green chip by a normal printing method or a sheet method using a paste and firing it, It is manufactured by printing or transferring an external electrode and firing. Hereinafter, the manufacturing method will be specifically described.

  First, a dielectric material (dielectric ceramic composition powder) contained in the dielectric layer paste is prepared, and this is made into a paint to prepare a dielectric layer paste.

  The dielectric layer paste may be an organic paint obtained by kneading a dielectric material and an organic vehicle, or may be a water-based paint.

As the dielectric material, the above-mentioned main component and subcomponent oxides, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above oxides or composite oxides by firing, such as carbonic acid, can be used. A salt, an oxalate salt, a nitrate salt, a hydroxide, an organometallic compound, or the like can be selected as appropriate and used in combination. For example, as for the material of BaTiO _3, it may be used BaTiO ₃ powder may be used BaCO ₃ powder and TiO ₂ powder. Further, as a raw material of BaZrO _3, may be used BaZrO ₃ powder may be used BaCO ₃ powder and ZrO ₂ powder.

  What is necessary is just to determine content of each compound in a dielectric raw material so that it may become a composition of the above-mentioned dielectric ceramic composition after baking. In the state before forming a paint, the particle size of the dielectric material is usually about 0.1 to 1 μm in average particle size.

Barium titanate (BaTiO ₃ ) powder as a main component material was produced by various liquid phase methods (for example, oxalate method, hydrothermal synthesis method, alkoxide method, sol-gel method, etc.) in addition to the so-called solid phase method. The thing manufactured by various methods, such as a thing, can be used.

In this embodiment, the main component raw material and the R element oxide raw material as the subcomponent raw material are calcined in advance, and the calcined raw material is added to the remaining subcomponent raw materials to obtain a dielectric raw material. Is preferred. Alternatively, the main component raw material, the R element oxide raw material, and at least a part of the BaZrO ₃ raw material may be preliminarily calcined, and the calcined raw material may be added to the remaining subcomponent raw materials to obtain a dielectric raw material. . By doing in this way, the diffusion state of Zr element and R element can be controlled, and the 1st diffusion phase and the 2nd diffusion phase can exist in a desired state.

  The calcining temperature is preferably 800 to 1000 ° C., and the calcining time is preferably 1 to 4 hours.

  An organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. The organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, toluene, and the like according to a method to be used such as a printing method or a sheet method.

  Further, when the dielectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder or a dispersant is dissolved in water and a dielectric material may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, etc. may be used.

  The internal electrode layer paste is prepared by kneading the above-mentioned organic vehicle with various conductive metals and alloys as described above, or various oxides, organometallic compounds, resinates, etc. that become the above-mentioned conductive materials after firing. Prepare.

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

  There is no restriction | limiting in particular in content of the organic vehicle in each above-mentioned paste, For example, what is necessary is just about 1-5 weight% of binders, for example, about 10-50 weight% of binders. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. The total content of these is preferably 10% by weight or less.

  When the printing method is used, the dielectric layer paste and the internal electrode layer paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip.

  When the sheet method is used, a dielectric layer paste is used to form a green sheet, the internal electrode layer paste is printed thereon, and these are stacked to form a green chip.

  Before firing, the green chip is subjected to binder removal processing. As binder removal conditions, the temperature rising rate is preferably 5 to 300 ° C./hour, the holding temperature is preferably 180 to 400 ° C., and the temperature holding time is preferably 0.5 to 24 hours. The firing atmosphere is air or a reducing atmosphere.

The firing of the green chip is preferably performed in a reducing atmosphere. As the atmosphere gas, for example, a mixed gas of N ₂ and H ₂ can be used by humidification. Other conditions are preferably as follows.

The heating rate is preferably 250 to 450 ° C./hour. The holding temperature at the time of firing is preferably 1300 ° C. or less, more preferably 1200 to 1300 ° C., and the holding time is preferably 0.5 to 8 hours, more preferably 2 to 3 hours. If the holding temperature is lower than the above range, the densification becomes insufficient. If the holding temperature is higher than the above range, the electrode is interrupted due to abnormal sintering of the internal electrode layer, the capacity temperature characteristic is deteriorated due to diffusion of the constituent material of the internal electrode layer, the dielectric Reduction of the body porcelain composition is likely to occur.
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 content in the firing atmosphere The pressure is preferably 10 ⁻¹⁴ to 10 ⁻¹⁰ MPa. When the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may be abnormally sintered and may be interrupted. Further, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized. The temperature lowering rate is preferably 50 to 500 ° C./hour.

  After firing in a reducing atmosphere, the capacitor element body is preferably annealed. Annealing is a process for re-oxidizing the dielectric layer, and this can significantly increase the IR lifetime, thereby improving the reliability.

The oxygen partial pressure in the annealing atmosphere is preferably 10 ⁻⁹ to 10 ⁻⁵ MPa. When the oxygen partial pressure is less than the above range, it is difficult to re-oxidize the dielectric layer, and when it exceeds the above range, oxidation of the internal electrode layer tends to proceed.

  The holding temperature at the time of annealing is preferably 1100 ° C. or less, and particularly preferably 1000 to 1100 ° C. When the holding temperature is lower than the above range, the dielectric layer is not sufficiently oxidized, so that the IR is low and the IR life tends to be short. On the other hand, if the holding temperature exceeds the above range, not only the internal electrode layer is oxidized and the capacity is lowered, but the internal electrode layer reacts with the dielectric substrate, the capacity temperature characteristic is deteriorated, the IR is lowered, the IR Life is likely to decrease. 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. In this case, the holding temperature is synonymous with the maximum temperature.

As other annealing conditions, the temperature holding time is preferably 0 to 20 hours, more preferably 2 to 4 hours, and the cooling rate is preferably 50 to 500 ° C./hour, more preferably 100 to 300 ° C./hour. . Further, as the annealing atmosphere gas, for example, humidified N ₂ gas or the like is preferably used.

In the above-described binder removal processing, firing and annealing, for example, a wetter or the like may be used to wet the N ₂ gas or mixed gas. In this case, the water temperature is preferably about 5 to 75 ° C.

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

  In this embodiment, by combining the calcining of the main component material and the specific subcomponent material, the control of the above firing conditions, etc., the diffusion state of the Zr element and the R element is controlled, and the dielectric ceramic composition after firing In the product, the existence state of the first diffusion phase and the second diffusion phase can be set as desired. As a result, it is possible to obtain a dielectric ceramic composition having improved DC bias characteristics and high temperature load life while maintaining a good dielectric constant and electrostrictive characteristics.

  The capacitor element body obtained as described above is subjected to end face polishing by, for example, barrel polishing or sand blasting, and the external electrode paste is applied and fired 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 or the like by soldering or the like and used for various electronic devices.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this 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, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
First, BaTiO ₃ powder was prepared as a main component material, and BaZrO ₃ , Gd ₂ O ₃ , MgCO ₃ , MnO and SiO ₂ were prepared as subcomponent materials.
Next, the BaTiO ₃ powder prepared above and BaZrO ₃ and Gd ₂ O ₃ were calcined under the conditions shown in Table 1. The calcined raw material and the remaining subcomponent raw materials were wet pulverized with a ball mill for 15 hours and dried to obtain a dielectric raw material. The addition amount of each subcomponent is 13 mol of BaZrO ₃ , 5 mol of Gd ₂ O ₃ , 3 mol of MgCO ₃ , 1 mol of MnO, and 1 mol of SiO _{2 with} respect to 100 mol of BaTiO _{3 as} the main component. Was 3.5 moles.
Incidentally, MgCO _3, after firing, and thus included in the dielectric ceramic composition as MgO.

  Next, the obtained dielectric material: 100 parts by weight, polyvinyl butyral resin: 10 parts by weight, dioctyl phthalate (DOP) as a plasticizer: 5 parts by weight, and alcohol as a solvent: 100 parts by weight 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 weight, terpineol: 52 parts by weight, ethyl cellulose: 3 parts by weight, and benzotriazole: 0.4 parts by weight are kneaded with three rolls to obtain a slurry. To prepare an internal electrode layer paste.

  Then, using the dielectric layer paste prepared above, a green sheet was formed on the PET film so that the thickness after drying was 30 μm. 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.

Next, the obtained green chip was subjected to binder removal treatment, firing and annealing under the following conditions to obtain a multilayer ceramic fired body.
The binder removal treatment conditions were temperature rising rate: 25 ° C./hour, holding temperature: 260 ° C., temperature holding time: 8 hours, and atmosphere: in the air.
In the firing, the heating rate was the heating rate shown in Table 1. The holding temperature was 1200 to 1300 ° C., and the holding time was 2 to 5 hours. The temperature decreasing rate was the same as the temperature increasing rate. 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: temperature rising rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, temperature falling rate: 200 ° 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 multilayer ceramic fired body by sand blasting, In-Ga was applied as an external electrode 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 20 μm, the thickness of the internal electrode layer is 1.5 μm, and the dielectric layer sandwiched between the internal electrode layers is The number was 10.

  About each obtained capacitor | condenser sample, the dielectric constant ((epsilon) s), the DC bias characteristic, the amount of electrostriction by voltage application, and the high temperature load lifetime were measured by the method shown below. Next, the measurement of the content ratio of the Zr element and the R element in the dielectric particles and the calculation of the area ratio (A) of the first diffusion phase and the area ratio (B) of the second diffusion phase were performed by the following methods.

Dielectric constant εs
At 25 ° C., a capacitor having a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms was input at 25 ° C. with a digital LCR meter (Y284, 4284A), and the capacitance C was measured. The relative dielectric constant εs (no unit) was calculated based on the thickness of the dielectric layer, the effective electrode area, and the capacitance C obtained as a result of the measurement. In this example, the average value of values calculated using 10 capacitor samples was taken as the relative dielectric constant. A higher relative dielectric constant is preferred, with 800 or more being considered good. The results are shown in Table 1.

A DC bias characteristic capacitor sample is held at 25 ° C. in a DC voltage applied state under an electric field of 10 V / μm, and a digital LCR meter (YHP 4284A) has a frequency of 1 kHz and an input signal level (measurement voltage). ) The capacitance was measured under the condition of 1 Vrms, and the rate of change with respect to the capacitance at a reference temperature of 25 ° C. was calculated. In this example, -40% or more was considered good. The results are shown in Table 1.

Electrostriction due to voltage application First, the capacitor sample was fixed by soldering to a glass epoxy substrate on which electrodes of a predetermined pattern were printed. Next, a voltage was applied to the capacitor sample fixed on the substrate under the conditions of AC: 10 Vrms / μm and a frequency of 3 kHz, and the vibration width of the capacitor sample surface at the time of voltage application was measured. A laser Doppler vibrometer was used to measure the vibration width of the capacitor sample surface. In this example, the average value of values measured using 10 capacitor samples was used as the amount of electrostriction. The amount of electrostriction is preferably low, and 40 ppm or less was considered good. The results are shown in Table 1.

The high temperature load life of the capacitor sample was evaluated by holding a DC voltage applied at 200 ° C. under an electric field of 40 V / μm and measuring the life time. In this example, the time from the start of application until the insulation resistance drops by an order of magnitude was defined as the lifetime. Further, this high temperature load life was carried out for 10 capacitor samples. The evaluation criteria were good for 5 hours or more. The results are shown in Table 1.

Measurement of content ratio of Zr element and R element in dielectric particles First, the boundary between the diffusion phase and the non-diffusion phase was measured as follows. In the cross section including the central portion of the obtained sample, a flaky analytical sample having a thickness of about 0.1 μm was prepared. Twenty particles were randomly extracted from this analysis sample using an operation transmission electron microscope (STEM). Then, image processing was performed on the X-ray spectrum measured by the energy dispersive X-ray spectrometer attached to the STEM to clarify the diffusion phase portion and the non-diffusion phase portion, and then the boundary line was visually determined.

  Next, for each sample, spectrum analysis is performed on 20 dielectric particles whose boundaries between the diffusion phase and the non-diffusion phase are measured using an energy dispersive X-ray spectrometer attached to the STEM. The content ratio of Zr element and R element in the body particles was measured. Next, principal component analysis (PCA) was performed on the obtained spectrum, and regions of the first diffusion phase 20b and the second diffusion phase 20c were calculated with respect to the diffusion phase by multivariate analysis. Note that the region of the non-diffusible phase 20a obtained by the principal component analysis was in good agreement with the non-diffusible phase portion obtained by the above method.

  Further, FIG. 4A shows a mapping image after principal component analysis for the sample 22, and FIG. 4B shows a mapping image after principal component analysis for the sample 25.

Calculation of the area ratio (A) of the first diffusion phase and the area ratio (B) of the second diffusion phase The ratio (area ratio) of the area occupied by each region obtained above to the 3 × 3 μm visual field area Calculated. In this example, A was satisfied when 1.0 ≦ A <16.0% and A + B satisfied 60 ≦ (A + B) <70%. The results are shown in Table 2.

From Table 1, when the contents of the Zr element and the R element are outside the scope of the present invention in the first diffusion phase and the second diffusion phase, the relative permittivity, the electrostriction amount, the DC bias characteristics, and the high temperature load life It can be confirmed that at least one of them has deteriorated.
In Samples 18 and 19, the first diffusion phase did not exist in the vicinity of the non-diffusion phase, and tended to exist outside the second diffusion phase. That is, the second diffusion phase tends to exist in the vicinity of the non-diffusion phase.

  On the other hand, when the contents of the Zr element and the R element are within the scope of the present invention in the first diffusion phase and the second diffusion phase, the DC bias is maintained while maintaining the relative permittivity and the amount of electrostriction favorably. Characteristics and high temperature load life can be improved.

  Further, as shown in FIG. 4, the first diffusion phase exists in the vicinity of the non-diffusion phase, and the first diffusion phase tends to exist inside the second diffusion phase in the dielectric particles. Can be confirmed.

  From Table 2, by making the sum (A + B) of the area ratio A of the first diffusion phase, the area ratio A of the first diffusion phase, and the area ratio B of the second diffusion phase within the preferable range of the present application, It can be confirmed that it can be further improved.

  4B, the area ratio A of the first diffusion phase is larger than the area ratio A of the first diffusion phase in FIG. 4A. As a result, the area ratio A of the first diffusion phase is It can be visually confirmed that it is outside the preferred range of the present invention.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of surface diffusion particles according to an embodiment of the present invention. FIG. 3 is a schematic diagram for explaining a method for measuring a boundary between a non-diffusible phase and a diffused phase. 4A is a mapping image for each element after principal component analysis is performed on a sample according to an embodiment of the present invention, and FIG. 4B is a main image regarding a sample according to a comparative example of the present invention. It is a figure which shows the mapping image about each element after performing a component analysis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Capacitor element body 2 ... Dielectric layer 20-24 ... Dielectric particle (surface diffusion particle)
20a-24a ... Non-diffusion phase 20b-24b ... 1st diffusion phase 20c-24c ... 2nd diffusion phase 3 ... Internal electrode layer 4 ... External electrode

Claims (2)

A main component comprising barium titanate;
As a subcomponent, BaZrO ₃ and
R element oxide (wherein R element is at least selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) 1), and a dielectric ceramic composition comprising:
The dielectric ceramic composition has surface diffusing particles having a surface diffusing structure comprising a non-diffusing phase and a diffusing phase that is present around the non-diffusing phase and includes at least a Zr element and the R element. And
A content ratio of the Zr element and the R element is measured with respect to a micro area in the diffusion phase, and a set of micro areas in which the content ratio of the R element is equal to or more than the content ratio of the Zr element When the second region is a set of minute regions in which the content ratio of the Zr element is larger than the content ratio of the R element,
In the first region, the first diffusion is performed in a region where the content ratio of the Zr element is 1.0 atom% or more and less than 2.0 atom% and the content ratio of the R element is 2.0 atom% or more and less than 3.5 atom%. Phase and
In the second region, the second diffusion is performed in a region where the content ratio of the Zr element is 2.0 atom% or more and less than 4.0 atom% and the content ratio of the R element is 1.0 atom% or more and less than 2.0 atom%. Phase and
The first diffusion phase is present in the vicinity of the non-diffusion phase, and the entire periphery of the first diffusion phase is a first region other than the first diffusion phase and a first region other than the first diffusion phase. A dielectric ceramic composition covered with one region and the second region, or a first region other than the first diffusion phase, the second region, and the non-diffusion phase.   In the dielectric ceramic composition, the ratio of the area occupied by the first diffusion phase to the viewing area of 3 × 3 μm is A [%], and the ratio of the area occupied by the second diffusion phase is B [%]. 2. The dielectric ceramic composition according to claim 1, wherein 1.0 ≦ A <16.0% and 60.0 ≦ (A + B) <70.0%.

Images