JP5151752B2 - Dielectric porcelain composition - Google Patents

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.

In Patent Document 1, in (Ba, Ca) TiO ₃ crystal particles (BCT particles) containing Si element, the dielectric content has a specific amount of Si element in the vicinity of the crystal particle surface and in a specific position inside the particle. Multilayer ceramic capacitors containing a body porcelain composition have been proposed.

However, the content ratio of the Si element inside the BCT particles is only measured at a specific position, and does not reflect the content ratio of the Si element inside the BCT particles. The multilayer ceramic capacitor disclosed in Patent Document 1 is intended for large capacity, and is considered difficult to use as a medium-high voltage capacitor.
JP 2007-201277 A

  This invention is made | formed in view of such a situation, and it aims at providing the dielectric ceramic composition which can improve a high temperature load lifetime, maintaining DC bias characteristic favorably.

  As a result of intensive studies to achieve the above object, the present inventors have found that both in the dielectric particles constituting the dielectric ceramic composition and in the grain boundary phase existing around the dielectric particles. It has been found that by setting the element content ratio within a specific range, the high temperature load life can be improved while maintaining good DC bias characteristics, and the present invention has been completed.

That is, the dielectric ceramic composition according to the present invention is
A main component comprising barium titanate;
A first subcomponent comprising BaZrO ₃ ;
R oxide (where R is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) A second subcomponent comprising
A third subcomponent comprising an oxide of M, where M is at least one selected from Mn, Ni, Cr, Co and Fe;
A dielectric ceramic composition comprising a fourth subcomponent comprising an oxide of Si,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary phase existing between the adjacent dielectric particles,
When the content ratio of the Si element at the boundary between the dielectric particles and the grain boundary phase is measured, the ratio of the measurement points at which the content ratio of the Si element is 1.0 atom% or more is the total of the measurement points. When the average value of the plurality of dielectric particles is calculated for the content ratio of the Si element in the dielectric particles, the average value is 0.5 atom% or more. And

  In the present invention, the Si element content in the grain boundary phase and the Si element content in the crystal grains are controlled so that the Si element satisfies the above range. By doing in this way, the dielectric ceramic composition which can improve a high temperature load lifetime can be obtained, maintaining DC bias characteristics favorably.

  The electronic component having a dielectric layer in which the dielectric ceramic composition according to the present invention is suitably used is not particularly limited, but it is a multilayer ceramic capacitor, a piezoelectric element, a chip inductor, a chip varistor, a chip thermistor, a chip resistor, and other surface mounting. (SMD) chip type electronic components are exemplified.

  Usually, in a dielectric ceramic composition, Si element tends to exist in a grain boundary phase. Since the region where the Si element is present has a high electric resistance, a relatively high amount of the Si element is present in the grain boundary phase, whereby the high temperature load life can be improved.

  However, if a large amount of Si element is present in the grain boundary phase, the difference in electrical resistance between the grain boundary phase and the inside of the dielectric particles increases, resulting in local problems, and conversely, the high temperature load life is reduced. May get worse.

  Further, if the Si element is simply present in the dielectric particles, the crystal structure of the dielectric particles is changed, and the DC bias characteristics are deteriorated.

  According to the present invention, the Si element is diffused inside the dielectric particles, and the content ratio in the particles and the content ratio of the Si element in the crystal grain boundary phase are controlled. The difference in electrical resistance between the two can be reduced. As a result, it is possible to obtain a dielectric ceramic composition in which the above-mentioned local problems are eliminated and the high temperature load life is improved. Therefore, the dielectric ceramic composition according to the present invention has good high temperature load life while maintaining good DC bias characteristics, and is suitably used for medium to high voltage applications having a relatively high rated voltage.

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.
2 is an enlarged cross-sectional view of a main part of the dielectric layer 2 shown in FIG.
FIG. 3 is a schematic diagram for explaining a method for measuring the content ratio of the Si element in the dielectric particles 2a and the grain boundary phase 2b.
FIG. 4 is a flowchart showing a process of obtaining a dielectric material from a main component material and a subcomponent material in the method for producing a dielectric ceramic composition according to the present invention.

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, a first subcomponent containing BaZrO ₃ , an oxide of R (where R is Sc, Y, La, Ce, Pr, Nd , Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, a second subcomponent, and an oxide of M (where M is Mn, A third subcomponent including at least one selected from Ni, Cr, Co, and Fe) and a fourth subcomponent including an oxide of Si.

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 a ratio of A site and B site of barium titanate, and x is preferably 1.000 ≦ x <1.010, more preferably 1.000 ≦ x ≦ 1. .004.

  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.

The first subcomponent (BaZrO ₃ ) mainly has an effect of suppressing the ferroelectricity of the main component, barium titanate. The content of the first subcomponent 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. If the content of the first subcomponent is too small, the electrostrictive characteristics and the DC bias characteristics tend to deteriorate, while if too large, the relative permittivity tends to decrease.

The second subcomponent (R oxide) mainly has an effect of suppressing the ferroelectricity of the main component, barium titanate. The content of the second subcomponent is preferably 4 to 6 mol and more preferably 4 to 5 mol in terms of R ₂ O _{3 with} respect to 100 mol of the main component. If the content of the second subcomponent 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 R oxide 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.

The third subcomponent (M oxide) has the effect of improving the reduction resistance of the dielectric ceramic composition. The content of the third subcomponent is preferably 0.1 to 2.0 mol in terms of MnO, NiO, CrO _3/2 , CoO _4/3 or FeO _{3/2 with} respect to 100 mol of the main component. More preferably, it is 0.4-1.5 mol. If the content of the third subcomponent is too small, the resistance value of the dielectric tends to decrease. On the other hand, if the amount is too large, the high temperature load life tends to deteriorate. As the third subcomponent, it is preferable to use an oxide of Mn or Cr because the effect of improving the characteristics is great among the above-mentioned oxides.

The fourth subcomponent (Si oxide) mainly serves as a sintering aid. The content of the fourth subcomponent is preferably 0.5 to 5.0 mol, more preferably 1.0 to 3.0 mol in terms of SiO _{2 with} respect to 100 mol of the main component. If the content of the fourth subcomponent is too small, the sinterability tends to deteriorate. On the other hand, if the amount is too large, the relative permittivity tends to decrease. The form in which the oxide of Si as the fourth subcomponent is not particularly limited, for example, may be included in the form of SiO ₂ alone, or a composite such as (Ba, Ca) SiO _3. It may be included in the form of an oxide.

In addition, in this embodiment, you may add another subcomponent in addition to the said 1st-4th subcomponent as needed. Examples of such subcomponents include Mg oxide and Al oxide. Mg oxide has the effect of stabilizing the capacity-temperature characteristics while maintaining other characteristics favorable. In addition, the Al oxide has an effect as a sintering aid while keeping other characteristics good. When these oxides are used, the content of Mg oxide is 1.0 to 5.0 mol in terms of MgO and Al oxide is in terms of Al ₂ O _{3 with} respect to 100 mol of the main component. And preferably 0.3 to 1.0 mol.

As shown in FIG. 2, the dielectric layer 2 includes dielectric particles (crystal grains) 2a and crystal grain boundary phases 2b formed between a plurality of adjacent dielectric particles 2a. Consists of including. This dielectric particle 2a is considered to contain barium titanate, which is the main component, and the subcomponents described above.

  The crystal grain boundary 2b is composed of an oxide of a material constituting the dielectric layer or the internal electrode layer, an oxide of a material added separately, or an oxide of a material mixed as an impurity during the process. Usually, it is mainly composed of glass or glass. In this embodiment, at least Si element is contained.

  In the present invention, Si elements are present (segregated) at a relatively high content in the crystal grain boundaries 2b. The dielectric particles 2a also contain Si element, and the content ratio is controlled. In addition, elements other than Si element, that is, Zr element, R element, M element, or other elements added as subcomponents may exist in the crystal grain boundary 2b.

  In the present invention, when the Si element content ratio is measured at the boundary between the grain boundary phase 2b and the dielectric particle 2a, the existence ratio of measurement points at which the Si element content ratio is 1.0 atom% or more is It is 50% or more of the measurement point, preferably 60 to 100%. Further, when the average value is calculated for the content ratio of the Si element in each dielectric particle 2a, the calculated average value is 0.5 atom% or more, preferably 0.7 atom% or more.

  Usually, the Si element is difficult to diffuse into the dielectric particles 2a and tends to stay in the crystal grain boundary phase 2b. Thus, since the Si element is segregated in the grain boundary phase 2b, a region having a high electric resistance is formed, and the high temperature load life tends to be improved. However, if there are many such regions with high electrical resistance, the difference in electrical resistance between the grain boundary phase 2b and the inside of the dielectric particles 2a becomes large, causing local problems, and conversely The high temperature load life may deteriorate.

  Further, for example, it is possible to diffuse Si element into the dielectric particles 2a by calcination or the like. However, simply diffusing the Si element into the particles changes the crystal structure of the particles and deteriorates electrical characteristics such as DC bias characteristics.

  Therefore, in the present invention, the Si element is diffused into the dielectric particles 2a, and the Si element is present (segregated) to some extent even in the crystal grain boundary phase. That is, the Si element content in the crystal grain boundary phase 2b and the average value of the Si element content in the dielectric particles 2a are controlled within the above range. By doing in this way, the high temperature load lifetime of a dielectric ceramic composition can be improved, maintaining DC bias characteristics favorably.

  When the content ratio of the measurement points having a Si element content of 1.0 atom% or more is less than 50% of all measurement points, the high temperature load life tends to deteriorate. Further, in the dielectric ceramic composition, when the average value of the content ratio of Si element in the dielectric particles is less than 0.5 atom%, the high temperature load life tends to deteriorate.

  The method for measuring the Si element content ratio at the boundary between the grain boundary phase 2b and the dielectric particle 2a and the average value of the Si element content ratio inside the dielectric particle 2a is not particularly limited. It can be measured by point analysis using an electron microscope (TEM).

  In the present embodiment, the Si element content can be measured as follows. First, a dielectric layer is observed with a scanning transmission electron microscope (STEM), and the dielectric particle 2a and the crystal grain boundary 2b are discriminated visually. Next, an arbitrary dielectric particle 2a is subjected to image processing, and the center of gravity in the image (cross section) of the dielectric particle 2a is calculated.

  Next, as shown in FIG. 3, in the dielectric particle 2a, a straight line is drawn from end to end of the dielectric particle 2a so as to pass through the center of gravity. On the straight line, the straight line and the dielectric particle are drawn. The intersection (the boundary between the crystal grain boundary phase and the dielectric particles) with the outer periphery of 2a is obtained. With respect to this intersection (measurement point), point analysis is performed using an energy dispersive X-ray spectrometer attached to the STEM, and the content ratio of the Si element in the grain boundary phase is calculated.

  By performing this for a predetermined number of dielectric particles, the Si element content in the crystal grain boundaries 2b can be measured. The number of measurement points is preferably 20 points or more. The number of dielectric particles to be selected is preferably 10 or more.

  Further, as shown in FIG. 3, the points inside the dielectric particles 2a are appropriately selected on the straight line (five points are selected in FIG. 3). At the selected point (measurement point), the point analysis is performed using the energy dispersive X-ray spectrometer attached to the STEM in the same manner as described above, and the content ratio of the Si element inside the dielectric particles is calculated. . And the average value of the content rate of Si element is calculated | required about a measurement point, and this is prescribed | regulated as the content rate of Si element in the dielectric particle.

  This measurement is performed on a plurality of dielectric particles, and an average value is further obtained for the Si element content ratio obtained in each dielectric particle. This average value can be regarded as the average value of the content ratio of Si element in all the dielectric particles constituting the dielectric layer 2.

  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 A manufacturing method of the multilayer ceramic capacitor 1 of this embodiment will be specifically described. In particular, the step of preparing the dielectric material will be described with reference to FIG.

  First, a dielectric material (a main component material and a subcomponent material) constituting a material of the dielectric ceramic composition contained in the dielectric layer 2 is prepared.

As the main component raw material and subcomponent raw material, the above-mentioned main component and subcomponent oxides, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the oxides and composite oxides described above by firing, for example, carbonates, oxalates, nitrates, hydroxides, organometallic compounds, and the like, can be appropriately selected and mixed for use. . For example, BaTiO ₃ may be used as a raw material for barium titanate, which is the main component, or BaCO ₃ and TiO ₂ may be used. Moreover, BaZrO ₃ may be used as a raw material for BaZrO ₃ as a subcomponent, or BaCO ₃ and ZrO ₂ may be used.

  The barium titanate raw material powder as the main component raw material is 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, Those produced by various methods can be used.

  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 present embodiment, as shown in FIG. 4, only the subcomponent materials (first to fourth subcomponent materials and other subcomponent materials) among the main component materials and subcomponent materials prepared above are predispersed. It is preferable.

  The preliminary dispersion method is not particularly limited, but it is preferably carried out by wet dispersion using a ball mill or the like by adding water, an organic solvent, or the like to the raw material powder of the accessory component. The preliminary dispersion is preferably performed for 20 to 30 hours. The average particle diameter of the raw material after preliminary dispersion is about 0.2 to 0.5 μm. By performing preliminary dispersion, it is possible to effectively suppress the local segregation of subcomponent elements from becoming too large.

  Next, as shown in FIG. 4, the main component raw material (barium titanate raw material) is added to and mixed with the raw material after preliminary dispersion (raw materials of the first to fourth subcomponents and other subcomponent raw materials). preferable.

  The mixing method is not particularly limited, but it is preferable to add water, an organic solvent, or the like to the mixture of the raw material after the pre-dispersion and the main component raw material, and perform wet mixing using a ball mill or the like. The mixing is preferably performed for 2 to 4 hours.

  Next, as shown in FIG. 4, the mixed powder (the main component material and the subcomponent material) obtained above is calcined. As calcination conditions, the temperature rising rate is 100 to 300 ° C./h, the holding temperature is preferably 750 to 1000 ° C., and the temperature holding time is preferably 1 to 3 hours. When the holding temperature is too low, the diffusion of Si element into the dielectric particles 2a becomes insufficient, and the high temperature load life tends to deteriorate. On the other hand, if the holding temperature is too high, the agglomeration of the subcomponent raw material powder occurs, the dispersibility of the calcined powder decreases, and the high temperature load life tends to deteriorate.

  This calcination may be performed in the air, or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. By this calcining, calcined powder is obtained.

  By preparing a calcined powder as described above and using it, the diffusion of Si element in the dielectric ceramic composition after firing is controlled, and the existence state in the grain boundary phase and the inside of the dielectric particle are controlled. The presence state in can be a predetermined one.

  As a result, a relatively large amount of Si element exists in the grain boundary phase and also diffuses into the dielectric particles, so the difference in electrical resistance between the grain boundary phase and the inside of the dielectric particles is reduced. Further, the high temperature load life can be improved while maintaining the DC bias characteristics well.

  In addition, as described above, by preliminarily dispersing only the auxiliary component raw material, and then adding the main component raw material to prepare a calcined powder, the powder of the auxiliary component raw material is calcined as in the past. Compared with the method of adding and predispersing the main component raw material, the process can be shortened.

  Next, the calcined powder (dielectric material) 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.

  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 obtained 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.

First, the rate of temperature rise is preferably 400 ° C./hour or more, more preferably 500 to 800 ° C./hour.
The holding temperature during firing is preferably 1000 to 1400 ° C., more preferably 1200 to 1300 ° C., and the holding time is preferably 0.5 to 8 hours, more preferably 2 to 5 hours. If the holding temperature is less than the above range, the densification is insufficient. 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 1000 ° C./hour, more preferably 100 to 800 ° 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, particularly 500 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 10 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.

  The capacitor element main body obtained as described above is subjected to end face polishing, for example, by 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 , R ₂ O ₃ , MO, and SiO ₂ were prepared as subcomponent materials. _As the R 2 _{O 3,} to prepare a _Gd 2 _{O 3,} as the MO, was prepared MnCO _3. In addition to the above raw materials, MgCO ₃ was prepared.

Next, the auxiliary component materials prepared above were wet-dispersed with a ball mill for 20 hours as a preliminary dispersion. BaTiO ₃ powder was added to the raw material after this pre-dispersion, wet mixed with a ball mill for 3 hours, and dried at 150 ° C. for 3 hours. The dried material was calcined at a holding temperature of 800 ° C. for 2 hours to obtain a calcined powder (dielectric material). In addition, the addition amount of each subcomponent is 11 mol of BaZrO ₃ , 5.0 mol of Gd ₂ O ₃ , and 1 mol of MnO with respect to 100 mol of BaTiO ₃ as a main component in the dielectric ceramic composition after firing. 0.0 mol, SiO ₂ 3.3 mol, and MgO 4.5 mol.
Note that MnCO ₃ and MgCO ₃ will be contained in the dielectric ceramic composition as MnO and MgO, respectively, after firing.

  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.
Firing was performed at a temperature elevation rate of 200 ° C./hour, a holding temperature of 1260 ° C., and a holding time of 2 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: 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 4.

  For each obtained capacitor sample, the measurement of the content ratio of Si element at the boundary between the crystal grain boundary phase and the dielectric particles in the dielectric layer and the content ratio of Si element inside the dielectric particles was performed by the following method. went. Next, the high temperature load life and DC bias characteristics were measured by the following methods.

Measurement of Si Element Content Ratio in Grain Boundary Phase For each sample, 8 arbitrary dielectric particles were observed with a transmission electron microscope (TEM), and the observed image was processed to obtain the center of gravity of the dielectric particles. It was. Next, a straight line was drawn from end to end of the dielectric particles so as to pass through the center of gravity, and the boundary between the grain boundary phase and the dielectric particles was taken as a measurement point on the straight line. That is, there are two measurement points in one dielectric particle. The content ratio of the Si element in the crystal grain boundary was measured by performing point analysis on the measurement point using an energy dispersive X-ray spectrometer attached to the TEM. A total of 16 measurement points were used.

  The ratio (%) of the measurement points at which the Si element content was 1.0 atom% or more was obtained with respect to the 16 measured points. In this example, 50% or more, that is, the case where the number of measurement points where the content ratio of the Si element is 1.0 atom% or more is 8 or more is considered good. The results are shown in Table 1.

Measurement of Si Element Content Ratio in Dielectric Particles For each sample, nine arbitrary dielectric particles were observed with a TEM, and the center of gravity was determined as described above. Next, a straight line was drawn from end to end of the dielectric particles so as to pass through the center of gravity. On this straight line, as shown in FIG. 3, the above point analysis is performed on five points that equally divide the intersection between the grain boundary phase and the dielectric particles into six, and the content ratio of the Si element at the five points is It was measured. The average value of the Si element content at these five points was taken as the Si element content in the dielectric particles. This measurement was performed on nine dielectric particles, and an average value was calculated for the content ratio of the Si element in the nine dielectric particles. The case where the average value of the content rate of Si element was 0.5 atom% or more was considered good. The results are shown in Table 2.

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 50 hours or more. The results are shown in Table 3.

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, 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, -60% or more was considered good. The results are shown in Table 3.

Example 2
A capacitor sample was prepared in the same manner as in Example 1 except that the holding temperature in calcination was set to 1000 ° C., and the above characteristics were measured. The results are shown in Tables 1-3.

Comparative Example 1
A capacitor sample was prepared in the same manner as in Example 1 except that calcination was not performed, and the above characteristics were measured. The results are shown in Tables 1-3.

Comparative Example 2
A capacitor sample was prepared in the same manner as in Example 1 except that the preliminary dispersion was not performed, and the above characteristics were measured. The results are shown in Tables 1-3.

Comparative Example 3
A capacitor sample was prepared in the same manner as in Example 1 except that the holding temperature in calcination was 1500 ° C., and the above characteristics were measured. The results are shown in Tables 1-3.

Comparative Example 4
A capacitor sample was prepared in the same manner as in Example 1 except that the holding temperature in calcination was set to 700 ° C., and the above characteristics were measured. The results are shown in Tables 1-3.

Comparative Example 5
A capacitor sample was prepared in the same manner as in Example 1 except that no Si oxide (fourth subcomponent) was contained, and the above characteristics were measured. The results are shown in Tables 1-3.

  From Tables 1 and 2, only in the samples of Examples 1 and 2, the content ratio of Si element at the boundary between the grain boundary phase and the dielectric particles, and the average value of the content ratio of Si element inside the dielectric particles Can be confirmed to be within the scope of the present invention. As a result, from Table 3, it can be confirmed that the samples of Examples 1 and 2 have both good high-temperature load life and DC bias characteristics.

  On the other hand, in the samples of Comparative Examples 1 to 5, one of the content ratio of the Si element at the boundary between the grain boundary phase and the dielectric particle and the average value of the content ratio of the Si element inside the dielectric particle Or both are outside the scope of the present invention. As a result, from Table 3, in the samples of Comparative Examples 1 to 5, the high temperature load life cannot be improved. Alternatively, it can be confirmed that the DC bias characteristic is deteriorated. For example, in the sample of Comparative Example 2, since the auxiliary component raw material was not predispersed, it was confirmed that the presence state of the Si element was excessively localized in the grain boundary phase and the high temperature load life was deteriorated. it can. The sample of Comparative Example 3 has good high temperature load life because Si element is diffused in the dielectric particles, but the DC bias characteristic is deteriorated because there is little Si element present in the grain boundary phase. You can confirm that

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the dielectric layer 2 shown in FIG. FIG. 3 is a schematic diagram for explaining a method for measuring the content ratio of the Si element in the dielectric particles 2a and the grain boundary phase 2b. FIG. 4 is a flowchart showing a process of obtaining a dielectric material from a main component material and a subcomponent material in the method for producing a dielectric ceramic composition according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Capacitor element body 2 ... Dielectric layer 2a ... Dielectric particle 2b ... Grain boundary phase 3 ... Internal electrode layer 4 ... External electrode

Claims (2)

A main component comprising barium titanate;
A first subcomponent comprising BaZrO ₃ ;
R oxide (where R is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) A second subcomponent comprising
A third subcomponent comprising an oxide of M, where M is at least one selected from Mn, Ni, Cr, Co and Fe;
A dielectric ceramic composition comprising a fourth subcomponent comprising an oxide of Si,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary phase existing between the adjacent dielectric particles,
When the content ratio of the Si element at the boundary between the dielectric particles and the grain boundary phase is measured, the ratio of the measurement points at which the content ratio of the Si element is 1.0 atom% or more is the total of the measurement points. When the average value of the plurality of dielectric particles is calculated for the content ratio of the Si element in the dielectric particles, the average value is 0.5 atom% or more. A dielectric ceramic composition. A method for producing a dielectric ceramic composition according to claim 1,
Preliminarily dispersing the raw materials of the first to fourth subcomponents;
Adding a raw material of a main component to the raw materials of the first to fourth subcomponents after the preliminary dispersion and mixing;
A method for producing a dielectric ceramic composition comprising:

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