JP2008222520A - Dielectric porcelain composition and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric porcelain composition and an electronic component which have reduced amount of electrostriction and can improve volume temperature change rate at a high temperature. <P>SOLUTION: The dielectric porcelain composition has a main component containing BaTiO<SB>3</SB>, and a first subcomponent containing BaZrO<SB>3</SB>, a second subcomponent containing Mg oxide, a third subcomponent containing an oxide of a rare earth element (R), a forth subcomponent containing oxides of one or more elements selected from Mn, Cr, Co and Fe, and a fifth subcomponent containing oxides of one or more elements selected from Si, Al, Ge, B and Li, wherein the dielectric porcelain composition has dielectric particles and crystal grain boundaries, at least a part of the dielectric particles in the dielectric particles has a surface diffusion structure constituted of a center layer and a diffusion layer which exists around the center layer, and it satisfies Cmax/Cb>1 when the concentration of R near the interface of the dielectric particles is Cb and the max value of the concentration of R at the diffusion layer is Cmax. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic composition and an electronic component having the dielectric ceramic composition in a dielectric layer. More specifically, the dielectric ceramic composition is suitably used for medium-high voltage applications having a high rated voltage (for example, 100 V or more). The present invention relates to a body porcelain composition and an electronic component.

  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, the medium- and high-voltage capacitors used at a high rated voltage (for example, 100 V or more) are ECM (engine electric computer module), fuel injection device, electronic control throttle, inverter, converter, HID headlamp unit, hybrid engine battery. It is suitably used for devices such as control units and digital still cameras.

  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, in particular, it is desired that the rate of change in the capacity temperature is small even at a high temperature of 100 ° C. or higher.

  In response to such a demand, for example, Patent Document 1 discloses a dielectric having a configuration in which the concentrations of Mg, Mn, and rare earth elements in crystal grains gradually increase from the center of the crystal grains toward the crystal grain boundary. Multilayer ceramic capacitors having layers have been proposed.

  Further, Patent Document 2 is a multilayer ceramic capacitor having a dielectric layer made of dielectric particles having a core-shell structure, and the shell portion includes an acceptor element such as Mn, Mg, and a rare earth element. A structure has been proposed in which the concentrations of the acceptor element and the rare earth element contained in the portion gradually increase from the boundary between the core portion and the shell portion toward the crystal grain boundary.

  Further, Patent Document 3 discloses a multilayer ceramic capacitor having a dielectric layer made of a dielectric particle that is a solid solution, wherein the concentration of an acceptor element such as Mn and a rare earth element such as Ho contained in the dielectric particle is as follows. There has been proposed one having a structure that gradually increases from the center of the grain toward the grain boundary.

  However, in the multilayer ceramic capacitor disclosed in Patent Document 1, the test voltage for IR (insulation resistance) life is as low as 4.75 V / μm and is not intended for use at a high voltage. On the other hand, the multilayer ceramic capacitor disclosed in Patent Document 2 is only described as satisfying the B characteristic as the capacity-temperature characteristic, and is not intended for use at a high temperature. In addition, the multilayer ceramic capacitor disclosed in Patent Document 3 only satisfies the F characteristic as the capacity-temperature characteristic, and is not intended for use at a high temperature as in Patent Document 2.

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-A-2005-217000 JP 2001-230149 A JP 2001-230148 A

  The present invention has been made in view of such circumstances, and a dielectric ceramic composition that has a low amount of electrostriction when a voltage is applied and that can improve the rate of change in capacitance temperature at high temperatures, and a dielectric ceramic composition that is a dielectric ceramic composition. An object is to provide an electronic component having a body layer.

  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 dielectric particles constituting the dielectric ceramic composition, the concentration of a specific subcomponent element in the region where the subcomponent element diffuses into the main component element is reduced. It has been found that the capacity temperature change rate at a high temperature can be improved by increasing the concentration of the subcomponent element in the vicinity of the interface of the boundary, 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 ;
A second subcomponent comprising an oxide of Mg;
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 third subcomponent comprising
A fourth subcomponent comprising an oxide of at least one element selected from Mn, Cr, Co and Fe;
A dielectric ceramic composition comprising: a fifth subcomponent including an oxide of at least one element selected from Si, Al, Ge, B and Li,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary existing between the adjacent dielectric particles;
A surface diffusion structure in which at least some of the plurality of dielectric particles are composed of a central layer and a diffusion layer in which the subcomponent is diffused, which exists around the central layer. Have
In the dielectric particle having the surface diffusion structure, the dielectric particle is located at a distance of 5% of the particle diameter of the dielectric particle from the interface of the crystal grain boundary in the direction from the crystal grain boundary toward the approximate center of the dielectric particle. The relationship of Cmax / Cb> 1 is satisfied, where Cb is the concentration of R in the vicinity of the interface and Cmax is the maximum value of the concentration of R in the diffusion layer.

  The dielectric ceramic composition of the present invention can reduce the amount of electrostriction when a voltage is applied by including a main component containing barium titanate and the specific subcomponent. In addition, among the plurality of dielectric particles constituting the dielectric ceramic composition of the present invention, at least some of the dielectric particles have a surface diffusion structure. The surface diffusion structure is a structure composed of a central layer that is substantially composed of the main component and a diffusion layer that exists around the central layer and in which the subcomponent diffuses into the main component.

  In the present invention, the R element is present in the diffusion layer, and the concentration distribution of R in the diffusion layer is higher than the concentration (Cb) of R in the vicinity of the interface of the dielectric particles. The maximum value (Cmax) of the R concentration at an arbitrary point is large. That is, the diffusion layer shows a concentration distribution where Cmax / Cb> 1.

  Since the concentration distribution of the R element has the above configuration, the capacity-temperature characteristic can be improved.

  Preferably, the ratio of the dielectric particles satisfying the relationship of Cmax / Cb> 1 is 70% or more, more preferably 90% or more with respect to all the dielectric particles having the surface diffusion structure.

  By setting the ratio of the dielectric particles satisfying the relationship of Cmax / Cb> 1 within the above range, the above-described effect can be further increased.

  Preferably, the ratio of each subcomponent in terms of oxide or composite oxide to 100 mol of the main component is as follows: first subcomponent: 9 to 13 mol, second subcomponent: 2.7 to 5.7 mol, Third subcomponent: 4.5 to 5.5 mol, fourth subcomponent: 0.5 to 1.5 mol, and fifth subcomponent: 3.0 to 3.9 mol. In particular, the capacity temperature change rate can be further improved by setting the addition amount of each subcomponent within the above range.

  According to the present invention, there is also provided an electronic component having a dielectric layer and an internal electrode layer, wherein the dielectric layer is composed of any one of the above dielectric ceramic compositions. .

  The electronic component according to the present invention is not particularly limited, and examples thereof include a multilayer ceramic capacitor, a piezoelectric element, a chip inductor, a chip varistor, a chip thermistor, a chip resistor, and other surface mount (SMD) chip type electronic components.

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 diagram of surface diffusion particles according to an embodiment of the present invention,
FIG. 3A is a schematic diagram for explaining a method of measuring Cmax and Cb of an element of R in surface diffusion particles according to an embodiment of the present invention.
FIG. 3B is a schematic diagram for explaining a method of measuring Cmax and Cb of an R element in surface diffusion particles according to a conventional example,
FIG. 4 is a TEM photograph of surface diffusion particles according to an embodiment of the present invention.
FIG. 5 is a graph showing the concentration distribution of the R element of the surface diffusion particles 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 respective 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 comprises a main component containing barium titanate,
A first subcomponent comprising BaZrO ₃ ;
A second subcomponent comprising an oxide of Mg;
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 third subcomponent comprising
A fourth subcomponent comprising an oxide of at least one element selected from Mn, Cr, Co and Fe;
And a fifth subcomponent including an oxide of at least one element selected from Si, Al, Ge, B, and Li.

The barium titanate contained as the main component is represented by, for example, the composition formula Ba _m TiO _{2 + m} , and _m in the composition formula is 0.990 <m <1.010, and the ratio of Ba to Ti Can be used such that is 0.990 <Ba / Ti <1.010.

The content of the first subcomponent (BaZrO ₃ ) is preferably 9 to 13 mol and more preferably 10 to 13 mol in terms of BaZrO _{3 with} respect to 100 mol of the main component. The first subcomponent mainly has an effect of suppressing the ferroelectricity of the main component barium titanate. If the content of the first subcomponent is too small, the temperature characteristics at the time of voltage application tend to deteriorate, while if too large, the relative dielectric constant tends to decrease.

  The content of the second subcomponent (Mg oxide) is preferably 2.7 to 5.7 mol, more preferably 4.0 to 5.7 mol in terms of MgO with respect to 100 mol of the main component. is there. The second subcomponent mainly has an effect of suppressing the ferroelectricity of the main component barium titanate. If the content of the second subcomponent is too small, the temperature characteristics at the time of voltage application tend to deteriorate, while if too large, the relative dielectric constant tends to decrease.

The content of the third subcomponent (oxide of R), relative to 100 _moles of the main component in R 2 _{O 3} in terms of, preferably 4.5 to 5.5 moles, more preferably 4.7 to 5.5 moles. The third subcomponent mainly has an effect of suppressing the ferroelectricity of the main component barium titanate. If the content of the third subcomponent is too small, the temperature characteristics at the time of voltage application tend to deteriorate, while if too large, the relative dielectric constant tends to decrease. The R element constituting the R oxide is preferably at least one selected from Gd, Tb, Eu, Y, La, and Ce, and particularly preferably Gd.

The content of the fourth subcomponent (oxide of Mn, Cr, Co and Fe) is preferably in terms of MnO, Cr ₂ O ₃ , Co ₃ O ₄ or Fe ₂ O _{3 with} respect to 100 mol of the main component. It is 0.5-1.5 mol, More preferably, it is 0.7-1.2 mol. If the content of the fourth subcomponent is too small or too large, the insulation resistance tends to decrease. As the fourth subcomponent, it is preferable to use an oxide of Mn from the viewpoint that the effect of improving the characteristics is large among the above oxides.

The content of the fifth subcomponent (oxide of Si, Al, Ge, B and Li) is SiO ₂ , Al ₂ O ₃ , GeO ₂ , B ₂ O ₃ or Li ₂ O with respect to 100 mol of the main component. It is preferably 3.0 to 3.9 mol in terms of conversion. If the content of the fifth 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. As the fifth subcomponent, it is preferable to use an oxide of Si from the viewpoint that the effect of improving the characteristics is large among the above oxides.

Structure of Dielectric Particle In the present embodiment, at least some of the dielectric particles contained in the dielectric layer 2 are surface diffusion particles 20 having a surface diffusion structure as shown in FIG. The crystal grain boundary 22 exists between adjacent grains. The surface diffusion particles 20 are composed of a central layer 20a containing barium titanate as a main component, and a diffusion layer 20b that exists around the central layer 20a and in which components other than barium titanate are diffused in the barium titanate. Composed. Since the center layer 20a is substantially made of barium titanate, it exhibits ferroelectric characteristics. On the other hand, in the diffusion layer 20b, 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 are exhibited. In the present embodiment, it is considered that the R element is present in the diffusion layer 20b and other subcomponent elements are also present.

  Whether or not the dielectric particles have the above-described surface diffusion structure is determined by, for example, analyzing the dielectric particles using an energy dispersive X-ray spectrometer attached to a transmission electron microscope (TEM). Judgment can be made. Specifically, first, the dielectric particles are subjected to line analysis on a straight line passing through the approximate center of the particles to obtain the concentration distribution of each element. Next, the line analysis is performed again on the same particle with the straight line shifted by 90 degrees. Then, from the obtained concentration distribution, for example, it is determined whether or not there is a region where the concentration of the subcomponent element is rapidly decreased, that is, the central layer 20a.

  If the dielectric particles have such a structure, the diffusion layer 20b exhibiting paraelectricity is present around the center layer 20a, so that, for example, the applied DC voltage is applied to the diffusion layer 20b having a low dielectric constant. In addition, a decrease in insulation resistance can be suppressed. In addition, the presence of the central layer 20a exhibiting ferroelectricity can realize a high relative dielectric constant.

  The abundance ratio of the surface diffusion particles 20 having the above configuration is a number ratio when the number of all dielectric particles constituting the dielectric layer 2 is 100%, preferably 50 to 100%, more preferably 70 to 100%.

  In the dielectric particles having a surface diffusion structure according to the present invention, R elements (R is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, As for at least one selected from Tm, Yb, and Lu, it is characteristic that a portion showing a concentration higher than the concentration at the interface vicinity point of the diffusion layer 20b exists in the diffusion layer 20b. Further, since the R element as the sub-component element is hardly diffused in the central layer 20a, the concentration of the R element in the central layer 20a is lower than the concentration in the diffusion layer 20b. Therefore, in the present invention, the concentration distribution of the R element shows a mountain shape from the center of the dielectric particle toward the surface thereof.

  When the R element exhibits such a characteristic concentration distribution, it is possible to improve the capacity temperature change rate at a high temperature, for example, 125 ° C., while maintaining a good dielectric constant and electrostriction.

  In the present embodiment, whether or not the R element exhibits a mountain-shaped concentration distribution is determined as follows.

  As shown in FIG. 3A, with respect to the dielectric particles having the above surface diffusion structure, from the end of the particle to the substantial center, preferably from the end of the particle so as to pass through the approximate center of the particle. A line analysis is performed on the straight line with an energy dispersive X-ray spectrometer attached to the TEM, and the concentration of R element at each point on the line is measured. At this time, the analysis is performed at at least two points of the interface vicinity point B and an arbitrary point X in the diffusion layer different from the interface vicinity point B.

  The interface vicinity point B is a point located at a distance of 5% of the particle diameter of the dielectric particle from the interface of the crystal grain boundary in the direction from the crystal grain boundary to the approximate center of the dielectric particle.

  The maximum value Cmax and the interface vicinity point B among the concentrations C1, C2,... Cn (n is 1 or more) of the R element at arbitrary points X1, X2... Xn (n is 1 or more) in the diffusion layer. Is compared with the concentration Cb of the R element, and if Cmax is larger than Cb, that is, if Cmax / Cb> 1, it is determined that the R element exhibits a mountain-shaped concentration distribution. Even if all Cn other than Cmax are smaller than Cb, it is only necessary that Cmax is larger than Cb. The arbitrary point X may be only one point as long as it is in the diffusion layer 20b, but is preferably 5 points or more. Moreover, it is preferable that one of the arbitrary points X is a boundary point A between the diffusion layer 20b and the central layer 20a. Furthermore, when the concentration of the element of R at the boundary point A is Ca, Cmax / Ca ≧ 1, and more preferably Cmax / Ca> 1.

  Preferably, 1.1 ≦ Cmax / Cb ≦ 4.8. When Cmax / Cb is too small, the capacity-temperature characteristic tends to deteriorate. Further, if Cmax / Cb is too large, the capacity-temperature characteristic tends to deteriorate.

  When the above line analysis is performed on a straight line from the end of the particle to the approximate center, a concentration distribution of R element at one location is obtained, and the above line analysis passes through the approximate center of the particle. In addition, when it is performed on a straight line from the end of the particle to the end of the particle, the concentration distribution of the R element at two locations facing each other across the central layer of the particle is obtained. In the present embodiment, it is preferable that the above line analysis is performed on a straight line from the end of the particle so as to pass through the approximate center of the particle, and then the line analysis is further performed by shifting by 90 degrees. In this case, the concentration distribution of the R element at four locations of the diffusion layer 20b is obtained.

  In the obtained concentration distribution, if there is at least one portion where the R element exhibits a mountain-shaped concentration distribution, it is determined that the R element exhibits a mountain-shaped concentration distribution in the particle. The above line analysis is performed on at least 10, preferably 20 or more dielectric particles. It is preferable that the determination as to whether or not the R element has a mountain-shaped concentration distribution and the determination as to whether or not it has the above-described surface diffusion structure be performed simultaneously.

  In the dielectric particles having the surface diffusion structure according to the conventional example, as shown in FIG. 3B, the diffusion layer 20b is usually from the center of the particle or the boundary region between the diffusion layer 20b and the center layer 20a. The concentration of the subcomponent elements diffused in the diffusion layer 20b gradually increases until reaching the surface of the substrate. That is, Cmax / Cb ≦ 1.

  The mountain-shaped concentration distribution of the R element in the diffusion layer 20b described above can be realized by controlling the diffusion of the R element by controlling whether or not the subcomponent material is calcined and controlling the firing conditions.

  The average particle diameter of the dielectric particles contained in the dielectric layer 2 is measured as follows. That is, the capacitor element body 10 is cut in the stacking direction of the dielectric layer 2 and the internal electrode layer 3, the average area of the dielectric particles is measured in the cross section, the diameter is calculated as the equivalent circle diameter, and the value multiplied by 1.5 It is. The measurement was performed on 200 or more dielectric particles, and the value at which the accumulation was 50% from the cumulative frequency distribution of the obtained particle diameter was defined as the average particle diameter (unit: μm).

  In the present embodiment, the average particle diameter may be determined according to the thickness of the dielectric layer 2 and the like, but is preferably 1.5 μm or less.

Internal electrode layer 3
The conductive material contained in the internal electrode layer 3 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 is not particularly limited, but in the present invention, inexpensive Ni, Cu, and alloys thereof can be used. 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. What is necessary is just to determine content of each compound in a dielectric material so that it may become a composition of an 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 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. What was manufactured by the method of can be used.
The above-mentioned raw materials may be added as they are to the main component raw materials as the subcomponent raw materials, but it is preferable to calcine only the subcomponent raw materials in advance and use the calcined raw materials as the main component raw materials. To make a dielectric material.

  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.

  First, the rate of temperature rise is preferably 50 to 500 ° C./hour, more preferably 200 to 400 ° C./hour. Moreover, it is preferable to change a temperature increase rate until it reaches the holding temperature at the time of firing. Specifically, for example, the temperature can be 200 ° C./hour up to 800 ° C., 300 ° C./hour from 800 ° C. to 1000 ° C., and 400 ° C./hour from 1000 ° C. to the holding temperature.

The holding temperature during firing is preferably 1000 to 1400 ° C, more preferably 1200 to 1350 ° C, and the holding time is preferably 0.5 to 8 hours, more preferably 1 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, and 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 rate of temperature reduction is preferably 50 to 500 ° C./hour, more preferably 200 to 400 ° C./hour. Similarly to the temperature rising rate, the temperature decreasing rate is preferably changed until the temperature reaches room temperature. Specifically, for example, the temperature from the holding temperature to 1000 ° C. can be 400 ° C./hour, the temperature from 1000 ° C. to 800 ° C. can be 300 ° C./hour, and the temperature below 800 ° C. can be 200 ° C./hour.

  In the present embodiment, the degree of diffusion of a specific subcomponent present in the diffusion layer 20b by combining the addition amount of the subcomponent raw material powder, presence / absence of calcining of the subcomponent raw material, control of the above baking conditions, and the like. Can be controlled. As a result, a characteristic concentration distribution satisfying Cmax / Cb> 1 can be obtained for the R element.

  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, the multilayer ceramic capacitor is exemplified as the electronic component according to the present invention. However, the electronic component according to the present invention is not limited to the multilayer ceramic capacitor, and has a dielectric layer having the above configuration. Anything is fine.

  In the above-described embodiment, the case where the concentration of the element of R satisfies Cmax / Cb> 1 has been described. However, the concentration of the other subcomponent element is set so as to satisfy Cmax / Cb> 1. These conditions may be controlled.

  In particular, when the concentration of the element of R and the concentration of Mg contained in the second subcomponent simultaneously satisfy Cmax / Cb> 1, not only the capacity-temperature change rate but also the IR lifetime is improved. be able to.

  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 , MgCO ₃ , Gd ₂ O ₃ , MnO and SiO ₂ were prepared as subcomponent materials. Next, only the auxiliary component materials prepared above were calcined at 1000 ° C. The calcined raw material and the main component raw material 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.
In addition, the amount shown in Table 1 is the amount in terms of complex oxide (first subcomponent) or each oxide (first to fifth subcomponent). Further, MgCO _{3 as} the second subcomponent will be contained in the dielectric ceramic composition as MgO after firing.

  Next, the obtained dielectric material: 100 parts by weight, polyvinyl butyral resin: 10 parts by weight, dibutyl 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. Thus, an internal electrode layer paste was produced.

  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.
The firing rate was 200 ° C./hour up to 800 ° C., 300 ° C./hour from 800 ° C. to 1000 ° C., and 400 ° C./hour from 1000 ° C. to the holding temperature. The holding temperature was 1220 to 1320 ° C., and the temperature lowering rate was the same as the temperature rising 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. In this example, as shown in Table 1, a plurality of samples in which the addition amount of each subcomponent was changed were prepared.

  About each obtained capacitor | condenser sample, the density | concentration measurement of the Gd element in a diffused layer was performed by the method shown below. Next, the relative dielectric constant (εs), the rate of change in capacitance temperature, and the amount of electrostriction due to voltage application were measured by the following methods.

Measurement of concentration of R element in diffusion layer For each sample, by selecting 10 arbitrary surface diffusion particles and performing line analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope (TEM), The concentration distribution of the Gd element in the diffusion layer was measured. First, line analysis was performed in a straight line from the end to the end of the particle so as to pass through the approximate center of the dielectric particle, and then the line analysis was performed on the same particle with a 90 ° shift. At this time, 8 points in the diffusion layer were analyzed including points near the interface and boundary points between the diffusion layer and the central layer.

  That is, the concentration of the Gd element at the interface vicinity point is Cb, and the maximum value of the concentration of the Gd element is Cmax among 6 points excluding 2 points of the boundary point.

  When one of the four Gd concentration distributions obtained in the diffusion layer showed a mountain-shaped concentration distribution, the particle was judged to exhibit a mountain-shaped concentration distribution of the Gd element. The results are shown in Table 1. In addition, the (Cmax / Cb) value in Table 1 indicates the maximum value among the four (Cmax / Cb) values measured.

  For each capacitor sample, the above measurement was performed, and the ratio of the dielectric particles having a surface diffusion structure was measured using an energy dispersive X-ray spectrometer attached to a transmission electron microscope (TEM). It was measured by performing an analysis. As a result, the ratio was 60% or more for all samples.

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 dielectric constant is preferred. The results are shown in Table 1.

Capacity temperature characteristics (TC)
The capacitance at 125 ° C. was measured for the capacitor sample, and the rate of change relative to the capacitance at the reference temperature (25 ° C.) was calculated. The rate of change is preferably as small as possible and is preferably within ± 25%. 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. It is preferable that the amount of electrostriction is low. The results are shown in Table 1.

  FIG. 4 shows a TEM photograph of the dielectric particles of sample number 1. From the TEM photograph, it can be confirmed that the center layer and the diffusion layer surrounding the periphery exist in the dielectric particles. Further, FIG. 5 shows a graph of the concentration distribution of the Gd element in the surface diffusion particles according to sample numbers 1, 5, and 6.

From Table 1, samples (sample numbers 1 to 4) having Cmax / Cb greater than 1 for the Gd element have good relative permittivity and electrostriction, and good capacity-temperature change rate at 125 ° C. be able to. On the other hand, it can be confirmed that the samples with the Cmax / Cb smaller than 1 (sample numbers 5 to 8) are inferior in the capacity temperature change rate at 125 ° C. Further, from FIG. 5, sample number 1 (Example 1) satisfies the relationship of Cmax / Cb> 1, and sample numbers 5 and 6 (Comparative Examples 5 and 6) are outside the scope of the present invention. It can be confirmed visually. Furthermore, in sample number 1, it is possible to confirm that Ca <Cb <Cmax is satisfied when the concentration of the Gd element at the boundary point A between the center layer and the diffusion layer is Ca.
Note that the measurement of the concentration distribution for samples 1, 5 and 6 shown in FIG. 5 was performed by selecting dielectric particles having the same thickness of the central layer and the diffusion layer.

Example 2
A capacitor sample was prepared in the same manner as in Example 1 except that the content of each subcomponent was changed to the amount shown in Table 2, and the same characteristic evaluation as in Example 1 was performed. The results are shown in Table 2.

  From Table 2, when the content of each subcomponent is changed, the capacity at 125 ° C. is maintained while maintaining the relative permittivity and the amount of electrostriction by keeping the content of each subcomponent within the preferred range of the present invention. The temperature change rate can be further improved. On the other hand, it can be confirmed that the sample in which the content of each subcomponent is out of the range of the present invention tends to be slightly inferior in the capacity-temperature change rate.

Example 3
A capacitor sample was prepared in the same manner as in Example 1 except that the R element was replaced with the element shown in Table 3 instead of the third subcomponent Gd, and the content of each subcomponent was changed to the amount shown in Table 3. The same characteristic evaluation as in Example 1 was performed. The results are shown in Table 3.

  From Table 3, it can be confirmed that even when the R element of the third subcomponent is changed, by setting Cmax / Cb to be larger than 1, the same characteristics as in the case of Gd are exhibited.

Example 4
For the samples of Sample Nos. 1 to 4 in Example 1, the diffusion conditions of Mg contained in the second subcomponent were controlled in addition to Gd by setting the firing conditions different from those in Example 1. In other respects, a capacitor sample was prepared in the same manner as in Sample Nos. 1 to 4 in Example 1, and the same characteristic evaluation as in Example 1 and the IR lifetime were measured. The results are shown in Table 4. The IR lifetime was measured as follows.

The IR lifetime was evaluated by holding a DC voltage applied to an IR lifetime capacitor sample at 200 ° C. under an electric field of 40 V / μm and measuring the lifetime. 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 IR life was performed for 10 capacitor samples. The evaluation criteria were good for 20 hours or more. The results are shown in Table 4.

From Table 4, it can be confirmed that the concentration distribution of Gd and Mg satisfies Cmax / Cb> 1 by controlling the diffusion of Gd and Mg.
In Sample Nos. 101 to 104, not only Gd but also the Mg concentration distribution satisfies Cmax / Cb> 1, so that in addition to the good characteristics shown by Sample Nos. 1 to 4, the IR life is also good. It can be.

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 view of surface diffusion particles according to an embodiment of the present invention. FIG. 3A is a schematic diagram for explaining a method of measuring Cmax and Cb of an R element in surface diffusion particles according to an embodiment of the present invention. FIG. 3B is a schematic diagram for explaining a method of measuring Cmax and Cb of an R element in surface diffusion particles according to a conventional example. FIG. 4 is a TEM photograph of surface diffusion particles according to an example of the present invention. FIG. 5 is a graph showing the concentration distribution of the R element of the surface diffusion particles 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 3 ... Internal electrode layer 4 ... External electrode 20 ... Surface diffusion particle 20a ... Center layer 20b ... Diffusion layer 22 ... Grain boundary

Claims (6)

A main component comprising barium titanate;
A first subcomponent comprising BaZrO ₃ ;
A second subcomponent comprising an oxide of Mg;
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 third subcomponent comprising
A fourth subcomponent comprising an oxide of at least one element selected from Mn, Cr, Co and Fe;
A dielectric ceramic composition comprising: a fifth subcomponent including an oxide of at least one element selected from Si, Al, Ge, B and Li,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary existing between the adjacent dielectric particles;
A surface diffusion structure in which at least a part of the plurality of dielectric particles includes a central layer and a diffusion layer in which the subcomponent is diffused, which exists around the central layer. Have
In the dielectric particle having the surface diffusion structure, the dielectric particle is located at a distance of 5% of the particle diameter of the dielectric particle from the interface of the crystal grain boundary in the direction from the crystal grain boundary toward the approximate center of the dielectric particle. A dielectric ceramic composition satisfying a relationship of Cmax / Cb> 1, where Cb is the concentration of R at a point near the interface and Cmax is the maximum value of the concentration of R in the diffusion layer. object.   2. The dielectric ceramic composition according to claim 1, wherein a presence ratio of dielectric particles satisfying a relationship of Cmax / Cb> 1 is 70% or more with respect to all dielectric particles having the surface diffusion structure. The ratio of each subcomponent in terms of oxide or composite oxide to 100 mol of the main component is as follows:
First subcomponent: 9 to 13 mol,
Second subcomponent: 2.7 to 5.7 mol,
Third subcomponent: 4.5 to 5.5 mol,
4th subcomponent: 0.5-1.5 mol,
The dielectric ceramic composition according to claim 1, wherein the fifth subcomponent is 3.0 to 3.9 mol. An electronic component having a dielectric layer and an internal electrode layer,
The dielectric layer comprises a main component comprising barium titanate;
A first subcomponent comprising BaZrO ₃ ;
A second subcomponent comprising an oxide of Mg;
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 third subcomponent comprising
A fourth subcomponent comprising an oxide of at least one element selected from Mn, Cr, Co and Fe;
A dielectric ceramic composition containing a fifth subcomponent containing an oxide of at least one element selected from Si, Al, Ge, B and Li,
The dielectric ceramic composition has a plurality of dielectric particles and a crystal grain boundary existing between the adjacent dielectric particles;
A surface diffusion structure in which at least a part of the plurality of dielectric particles includes a central layer and a diffusion layer in which the subcomponent is diffused, which exists around the central layer. Have
In the dielectric particle having the surface diffusion structure, the dielectric particle is located at a distance of 5% of the particle diameter of the dielectric particle from the interface of the crystal grain boundary in the direction from the crystal grain boundary toward the approximate center of the dielectric particle. An electronic component satisfying a relationship of Cmax / Cb> 1, where C is the concentration of R at a point near the interface and Cmax is the maximum value of the concentration of R in the diffusion layer.   5. The electronic component according to claim 4, wherein a presence ratio of dielectric particles satisfying a relationship of Cmax / Cb> 1 is 70% or more with respect to all dielectric particles having the surface diffusion structure. The ratio of each subcomponent in terms of oxide or composite oxide to 100 mol of the main component is as follows:
First subcomponent: 9 to 13 mol,
Second subcomponent: 2.7 to 5.7 mol,
Third subcomponent: 4.5 to 5.5 mol,
4th subcomponent: 0.5-1.5 mol,
The electronic component according to claim 4 or 5, wherein the fifth subcomponent is 3.0 to 3.9 mol.

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