JP5061961B2 - 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 response to such a demand, for example, Patent Document 1 discloses a non-reducing dielectric having a composition in which a relatively large amount of an oxide such as rare earth oxide, Mn, or Mg is added to barium titanate as a main component. Ceramic has been proposed.

  Patent Document 2 proposes a multilayer ceramic capacitor in which a rare earth element and an M element (M is at least one selected from Ni, Co, Fe, Cr, and Mn) are present in the grain boundaries. .

  However, the multilayer ceramic capacitor disclosed in Patent Document 1 cannot sufficiently satisfy the requirements in the high temperature load life. Furthermore, the multilayer ceramic capacitor disclosed in Patent Document 2 does not satisfy the requirements in terms of DC bias characteristics.

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.
JP 2000-103668 A JP 2002-201065 A

  The present invention has been made in view of such a situation, and an object thereof is to provide a dielectric ceramic composition that has a low amount of electrostriction when a voltage is applied and that can improve high-temperature load life and DC bias characteristics. .

  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. In addition, in the crystal grain boundary existing around the dielectric particles constituting the dielectric ceramic composition, the content ratio of a specific subcomponent element is set to a specific range, It has been found that the high temperature load life and DC bias characteristics can be improved, 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 existing between the adjacent dielectric particles;
When the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary were measured, the ratio of the measurement points at which the content ratio of the Zr element and the content ratio of the R element were 1 atom% or more were all It is 90% or more of the measurement point, and the average value of the content ratio of the Zr element and the average value of the content ratio of the R element at the measurement point are 1 atom% or more.

Preferably, the ratio of the first subcomponent is 10 mol or more in terms of BaZrO _{3 and} the ratio of the second subcomponent is 4 to 6 mol in terms of R ₂ O _{3 with} respect to 100 mol of the main component. .

Preferably, when the barium titanate is expressed as a composition formula (BaO) _x · TiO ₂ , x in the formula is 1.000 or more and does not exceed 1.010.

  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.

  According to the present invention, usually, a specific amount of Zr element and R element that tend to diffuse into the main component is present in the grain boundary, and the content ratio of Zr element and the content ratio of R element in the crystal grain boundary are as described above. Thus, a dielectric ceramic composition controlled in the above range can be obtained. By doing in this way, the dielectric ceramic composition according to the present invention exhibits good high temperature load life and is suitably used for medium to high pressure applications having a relatively high rated voltage.

  Further, the content of the first subcomponent and the second subcomponent is within the above range, or the ratio (x) between the A site and B site of barium titanate contained in the main component is within the above range. In addition to the above effect, a dielectric ceramic composition having a high relative dielectric constant and excellent DC bias characteristics and electrostrictive characteristics can be obtained.

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 of measuring the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary 2b.
FIG. 4 shows the ratios of the measurement points where the Zr element content ratio and the R element content ratio at the crystal grain boundary are 1 atom% or more, and the high temperature load life for the samples according to the examples and comparative examples of the present invention. A graph showing the relationship,
FIG. 5 is a graph showing the relationship between the average value of the content ratio of the Zr element at the crystal grain boundary and the high temperature load life for the samples according to Examples and Comparative Examples of the present invention,
FIG. 6 is a graph showing the relationship between the average value of the content ratio of the R element at the crystal grain boundary and the high temperature load life for the samples according to the examples and comparative examples of 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. Note that the form in which the Si oxide as the fourth subcomponent is contained is not particularly limited. For example, it may be contained in the form of SiO ₂ or may be a composite oxide such as (Ba, Ca) SiO _3. It may be included in the form of a thing.

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 boundaries 2b formed between a plurality of adjacent dielectric particles 2a. Consists of. 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. Mainly composed of glass or glass.

  In the present invention, the grain boundary 2b contains a Zr element and an R element, and the content ratio thereof is controlled. In addition, Si element and M element may exist in the crystal grain boundary 2b.

  In the present invention, when the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary 2b are measured, the content ratio of the Zr element and the content ratio of the R element is 1 atom% or more, It is 90% or more of all measurement points, preferably 92 to 100%. Further, the average value of the content ratio of Zr element at the measurement point is 1 atom% or more, preferably 1.5 atom% or more, and the average value of the content ratio of R element at the measurement point is 1 atom% or more, preferably 1.3 atom%. That's it.

  Usually, the Zr element and the R element tend to diffuse into the main component, and the content ratio in the crystal grain boundary 2b is very small. On the other hand, in this invention, the high temperature load lifetime of a dielectric ceramic composition can be improved by controlling the content rate of Zr element and R element in said range.

  When the content ratio of the Zr element and the content ratio of the R element is less than 90% of all the measurement points, the high temperature load life tends to deteriorate. In addition, the high temperature load life tends to be deteriorated when both or one of the average value of the Zr element content and the average value of the R element content at the measurement point is less than 1 atom%.

  The method for measuring the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary 2b is not particularly limited, but can be measured by, for example, point analysis using TEM.

  In the present embodiment, the content ratio of the Zr element and the content ratio of the R element 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 is selected, and a predetermined number of measurement points are selected at the crystal grain boundary 2b existing around the dielectric particle. For example, as shown in FIG. 3, a point that divides the outer peripheral length of the dielectric particles into approximately five equal parts is taken as a measurement point. Then, at the selected measurement points (5 points), point analysis is performed using an energy dispersive X-ray spectrometer attached to the STEM, and the content ratio of the Zr element and the content ratio of the R element are calculated.

  By performing this for a predetermined number of dielectric particles, the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary 2b can be measured. The number of measurement points is preferably 100 points or more. The number of dielectric particles to be selected is preferably 20 or more. This is because the influence of the deviation in the content ratio of the Zr element and the R element can be reduced.

  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, (BaO) _x · TiO ₂ may be used as a raw material for (BaO) _x · TiO ₂ , or BaCO ₃ and TiO ₂ may be used. Further, BaZrO ₃ may be used as a raw material for BaZrO ₃ , or BaCO ₃ and ZrO ₂ may 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 state before forming a paint, the particle size of the dielectric material is usually about 0.1 to 1 μm in average particle size.

  The barium titanate powder as the main ingredient is various, such as those manufactured 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. What was manufactured by the method of can be used.

In the present embodiment, only the raw materials of the first subcomponent (BaZrO ₃ ), the second subcomponent (R element oxide), and the fourth subcomponent (Si oxide) are preliminarily calcined, and the calcined raw material Is preferably added to the main component material and the remaining subcomponent materials to form a dielectric material. For example, even if only the second subcomponent, the third subcomponent, and the fourth subcomponent are calcined in advance, it is difficult to obtain the effect of the present invention.

  The calcining temperature is preferably 1000 to 1200 ° C., and the calcining time is preferably 2 to 10 hours. Only the raw materials of the first subcomponent, the second subcomponent, and the fourth subcomponent are preliminarily calcined at a predetermined temperature and time so that the Zr element content ratio and the R element content ratio are within the above-described ranges. Can do.

  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. By setting the rate of temperature rise in the above range, the Zr element and the R element can be present in the grain boundary, and as a result, the content ratio of the Zr element and the content ratio of the R element can be in the above-described ranges. it can.

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.

  In the present embodiment, the Zr element at the grain boundary 2b in the dielectric layer 2 is combined by combining the amount of the auxiliary component raw material powder added, presence / absence of calcining of the specific auxiliary component raw material, control of the above baking conditions, and the like. The content ratio of R and the content ratio of the R element can be controlled within the ranges described above. As a result, it is possible to obtain a dielectric ceramic composition having good electrostrictive characteristics and DC bias characteristics and improved high temperature load life.

  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 was 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, (BaO) _x · TiO ₂ powder was prepared as a main component material, and BaZrO ₃ , R ₂ O ₃ , MO, and SiO ₂ were prepared as subcomponent materials. In addition, as (BaO) _x · TiO ₂ powder, those having the value of x shown in Table 1 were prepared. _As the R 2 _{O 3,} to prepare a _Gd 2 _{O 3} and _Y 2 _{O 3,} as the MO, was prepared MnO and _Cr 2 _{O 3.} Furthermore, in addition to the above raw materials, MgCO ₃ and Al ₂ O ₃ were prepared.
Next, only the auxiliary components shown in the column of “calcined auxiliary component” in Table 1 were calcined at 1000 ° C. for the auxiliary component materials prepared above. The calcined raw material, the main component raw material and the remaining subcomponent raw materials were wet pulverized in a ball mill for 15 hours and dried to obtain a dielectric raw material. The addition amount of each subcomponent, with respect to BaTiO ₃ 100 moles of the main component, and the amount shown in Table 1.
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. as shown in Table 1, 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: 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 sample, the measurement of the content rate of Zr element and R element in the crystal grain boundary in a dielectric material layer was performed by the method shown below. Next, the relative dielectric constant (εs), the DC bias characteristics, the amount of electrostriction due to voltage application, and the high temperature load life were measured by the following methods.

Measurement of content ratio of Zr element and R element at grain boundaries For each sample, 20 arbitrary dielectric particles were selected and pointed using an energy dispersive X-ray spectrometer attached to a transmission electron microscope (TEM). By performing the analysis, the content ratio of the Zr element and the R element in the crystal grain boundary was measured. First, the measurement points were selected so that the outer peripheral length of the dielectric particles was divided into approximately five equal parts at the crystal grain boundaries existing around the dielectric particles. At this measurement point, point analysis was performed to measure the content ratio of the Zr element and the content ratio of the R element. This measurement was performed on 20 dielectric particles, and the total number of measurement points was 100.

  The ratio (%) of the measurement points at which the content ratio of the Zr element and the content ratio of the R element were 1 atom% or more with respect to the measured 100 points. In this example, 90% or more, that is, the case where the number of measurement points at which the content ratio of the Zr element and the content ratio of the R element were 1 atom% or more was 90 points or more was considered good. The results are shown in Table 1.

  Furthermore, the average value of the content ratio of Zr element and the content ratio of R element was calculated | required about 100 measured. The case where both the average value of the content ratio of the Zr element and the average value of the content ratio of the R element were 1 atom% or more was regarded as good. The results are shown in Table 1.

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 2.

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, -40% or more was considered good. The results are shown in Table 2.

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 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 10 hours or more. The results are shown in Table 2.

  FIG. 4 shows the ratios of the measurement points where the content ratio of Zr element and the content ratio of R element at the crystal grain boundaries are 1 atom% or more, and the high temperature load life for samples Nos. 3 to 5 and 8 to 12. It is a graph which shows the relationship. FIG. 5 is a graph showing the relationship between the average value of the content ratio of the Zr element at the crystal grain boundary and the high temperature load life for the samples Nos. 1 and 8-11. FIG. 6 is a graph showing the relationship between the average value of the content ratio of the R element at the crystal grain boundary and the high temperature load life for samples Nos. 2 and 8-11.

From Tables 1 and 2, when the average value of the content ratio of Zr element at the grain boundary is less than 1 atom% (sample number 1) and when the average value of the content ratio of R element at the grain boundary is less than 1 atom% As is clear from Table 2, (Sample No. 2) has an inferior high-temperature load life.
In addition, even when the measurement point where the content ratio of the Zr element and the content ratio of the R element are 1 atom% or more is less than 90% of the whole (sample numbers 3 to 5), as shown in Table 2, the high temperature Load life is inferior.
Furthermore, when only the second subcomponent and the third subcomponent are calcined in advance (sample number 6) and when only the second to fourth subcomponents are calcined in advance (sample number 7), the content ratio of the Zr element It can be confirmed that the measurement points at which the content ratio of the R element is 1 atom% or more are 80% or less of the whole. As a result, as is clear from Table 2, the high temperature load life is extremely inferior.

  On the other hand, the average value of the content ratio of Zr element and the average value of the content ratio of R element in the grain boundary are within the scope of the present invention, and the content ratio of Zr element and the content ratio of R element are 1 atom%. When the above measurement points are within the scope of the present invention (sample numbers 8 to 12), as is clear from Table 2, while maintaining the relative dielectric constant, the DC bias characteristics, and the electrostrictive characteristics, The high temperature load life is improved.

  Such characteristic results are also apparent from FIGS. That is, from FIG. 4, it can be confirmed that the high temperature load life is drastically improved when the measurement point where the content ratio of the Zr element and the content ratio of the R element is 1 atom% or more exceeds 90% of the whole. . Further, from FIGS. 5 and 6, it can be confirmed that the high-temperature load life is rapidly improved when the average value of the content ratio of the Zr element or the R element at the crystal grain boundary is 1 atom% or more.

Example 2
As R ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ , Sm ₂ O ₃ , Dy ₂ O ₃ and Ho ₂ O ₃ were prepared, and the contents of each subcomponent were changed to the amounts shown in Table 3. A capacitor sample was prepared in the same manner as in Example 1, and the same characteristic evaluation as in Example 1 was performed. The results are shown in Tables 3 and 4.

From Tables 3 and 4, when the content of the first subcomponent or the second subcomponent is outside the preferred range of the present invention (sample numbers 13 to 16), as is clear from Table 4, the DC bias characteristics, Electrostrictive characteristics, relative permittivity, etc. are deteriorated. Also, when the value of x in the main component (BaO) _x · TiO ₂ is outside the preferred range of the present invention (sample numbers 17 and 18), as is apparent from Table 4, the DC bias characteristics and the high temperature Load life has deteriorated.
On the other hand, when the content of the first subcomponent or the second subcomponent, or the value of x is within the preferable range of the present invention, a better result can be obtained.

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 of measuring the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary 2b. FIG. 4 shows the ratios of the measurement points where the Zr element content ratio and the R element content ratio at the crystal grain boundary are 1 atom% or more, and the high temperature load life for the samples according to the examples and comparative examples of the present invention. It is a graph which shows a relationship. FIG. 5 is a graph showing the relationship between the average value of the content ratio of the Zr element at the crystal grain boundary and the high temperature load life for the samples according to Examples and Comparative Examples of the present invention. FIG. 6 is a graph showing the relationship between the average value of the content ratio of the R element at the crystal grain boundary and the high temperature load life for the samples according to the examples and comparative examples of 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 3 ... Internal electrode layer 4 ... External electrode

Claims (3)

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 existing between the adjacent dielectric particles;
When the content ratio of the Zr element and the content ratio of the R element in the crystal grain boundary were measured, the ratio of the measurement points at which the content ratio of the Zr element and the content ratio of the R element were 1 atom% or more were all A dielectric ceramic composition characterized in that it is 90% or more of the measurement point, and the average value of the content ratio of the Zr element and the average value of the content ratio of the R element at the measurement point is 1 atom% or more. . The ratio of the first subcomponent is 10 mol or more in terms of BaZrO _{3 and} the ratio of the second subcomponent is 4 to 6 mol in terms of R ₂ O _{3 with} respect to 100 mol of the main component. The dielectric ceramic composition as described in 1. _{3. When the} barium titanate is expressed as a composition formula (BaO) _x · TiO ₂ , x in the formula is 1.000 or more and does not exceed 1.010. 3. The dielectric ceramic composition as described.

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