TWI406310B - Dielectric ceramics and laminated ceramic capacitors - Google Patents

Dielectric ceramics and laminated ceramic capacitors Download PDF

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TWI406310B
TWI406310B TW097133152A TW97133152A TWI406310B TW I406310 B TWI406310 B TW I406310B TW 097133152 A TW097133152 A TW 097133152A TW 97133152 A TW97133152 A TW 97133152A TW I406310 B TWI406310 B TW I406310B
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crystal
dielectric
barium titanate
dielectric ceramic
crystal grains
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TW097133152A
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Chinese (zh)
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TW200921726A (en
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Yusuke Azuma
Youichi Yamazaki
Masaaki Nagoya
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Kyocera Corp
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Publication of TWI406310B publication Critical patent/TWI406310B/en

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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00Fixed capacitors; Processes of their manufacture
    • H01G4/002Details
    • H01G4/018Dielectrics
    • H01G4/06Solid dielectrics
    • H01G4/08Inorganic dielectrics
    • H01G4/12Ceramic dielectrics
    • H01G4/1209Ceramic dielectrics characterised by the ceramic dielectric material
    • H01G4/1218Ceramic dielectrics characterised by the ceramic dielectric material based on titanium oxides or titanates
    • H01G4/1227Ceramic dielectrics characterised by the ceramic dielectric material based on titanium oxides or titanates based on alkaline earth titanates
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    • C04B35/01Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
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Abstract

[PROBLEMS] To provide a dielectric ceramic, which has high permittivity and low dielectric loss, can satisfy X7R properties in EIA standards in a temperature change of specific permittivity, and can realize high insulating resistance even in the case of low applied voltage, and a laminated ceramic capacitor which comprises the dielectric ceramic as a dielectric layer and has an excellent service life property in a high-temperature load test. [MEANS FOR SOLVING PROBLEMS] A dielectric ceramic composed mainly of barium titanate and containing predetermined amounts of vanadium, magnesium, manganese, and a rare earth element, wherein the diffracted intensity of a (004) face, which exhibits tetragonal barium titanate, is larger than the diffracted intensity of a (004) face, which exhibits cubic barium titanate, the crystal grain comprises a crystal grain having a calcium concentration of not more than 0.2 atomic% and a crystal grain having a calcium concentration of not less than 0.4 atomic%, the area ratio of the crystal grain having a calcium concentration of not less than 0.4 atomic% is 0.4 to 0.7, and the average diameter of the crystal grains is 0.21 to 0.28 µm.

Description

Dielectric ceramic and multilayer ceramic capacitor
The present invention relates to a dielectric ceramic composed of a crystal grain containing barium titanate as a main component, and a multilayer ceramic capacitor using the dielectric ceramic as a dielectric layer.
In recent years, the demand for miniaturization of electronic components due to the increase in density of electronic circuits has increased, and the miniaturization and large capacity of multilayer ceramic capacitors are rapidly increasing. Accordingly, the thinning of each of the dielectric layers in the multilayer ceramic capacitor is progressing, and thus there is a need for a dielectric ceramic which can maintain the reliability as a capacitor even if it is thinned. In particular, for the use of a capacitor for a withstand voltage at a high rated voltage, the miniaturization and the increase in capacity of the capacitor are required to have a very high reliability for the dielectric ceramic.
It is known that a base metal can be used as a material constituting the internal electrode layer, and the temperature change of the electrostatic capacity satisfies the X7R characteristic of the EIA (electronic industries association) standard (-55 to 125 ° C, ΔC = ± 15%) As the above technique, the applicant of the present application proposed the dielectric ceramic disclosed in Patent Document 1.
In the above technique, a dielectric ceramic is formed by using two types of barium titanate having different calcium concentrations as a main crystal, and contains magnesium, a rare earth element, manganese, etc., thereby increasing the dielectric constant and improving the insulation resistance. (IR, insulation resistance) is the life characteristic in the high temperature load test. However, in the rapid development of miniaturization and large capacity, it is still seeking to further improve reliability.
In addition, as for the dielectric ceramics for dielectric layers constituting the multilayer ceramic capacitor, as in the case of the above-described Patent Document 1, the dielectric properties satisfying the EIA standard and the dielectric properties of the insulation resistance in the high-temperature load test are improved. Ceramics are known as disclosed in Patent Documents 2 and 3.
The dielectric ceramic disclosed in Patent Document 2 contains, as a main component of crystal grains of the dielectric ceramic, magnesium, a rare earth element, vanadium, etc., and is in an X-ray diffraction pattern. The ray of the (200) plane partially overlaps with the ray of the (002) plane, and becomes a crystal structure of a wide-angle ray (so-called core-shell structure); thereby improving the dielectric breakdown voltage or the insulation resistance at a high temperature load test Life characteristics in the middle.
Further, the dielectric ceramic disclosed in Patent Document 3 adjusts the valence of vanadium dissolved in barium titanate to a value close to four valences, thereby suppressing the movement of electrons existing in the crystal grains. And inhibiting excessive diffusion of vanadium to barium titanate or precipitation of vanadium compound, forming a core-shell structure of a shell phase having vanadium in the crystal grains, and having a moderate concentration gradient in the shell phase, thereby achieving life characteristics in a high temperature load test Improve.
[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-156450
[Patent Document 2] Japanese Patent Laid-Open No. Hei 8-124785
[Patent Document 3] Japanese Patent Laid-Open Publication No. 2006-347799
However, the dielectric ceramic disclosed in the above Patent Documents 1 to 3 has a high dielectric constant and a temperature change of the dielectric constant satisfies the X7R characteristic of the EIA standard (-55 to 125 ° C, and the rate of change of the dielectric constant is ± Although it is less than 15%), there is a problem that the dielectric loss is large, and although a high insulation resistance can be obtained when the applied voltage is low, there is a problem that the insulation resistance is increased when the applied voltage is increased.
Further, in the multilayer ceramic capacitor including the dielectric ceramic as the dielectric layer, since the dielectric resistance of the dielectric ceramic is lowered, it is difficult to satisfy the life characteristics in the high-temperature load test when the dielectric layer is thinned.
Therefore, an object of the present invention is to provide a dielectric ceramic which has a high dielectric constant and a small dielectric loss, and the temperature variation of the dielectric constant satisfies the X7R characteristic of the EIA standard, and is high even when the applied voltage is low. Insulation resistance, and the reduction in insulation resistance is small when the voltage is increased. Further, another object of the present invention is to provide a multilayer ceramic capacitor comprising the dielectric ceramic as described above as a dielectric layer, which is excellent in life characteristics in a high-temperature load test.
The dielectric ceramic of the present invention contains barium titanate as a main component and contains 0.05 to 0.3 mol of vanadium in terms of V 2 O 5 and 0 to 0 in terms of MgO. 0.1 mol of magnesium, 0 to 0.5 mol of manganese in terms of MnO, and 0.5 to 1.5 mol of RE 2 O 3 in a rare earth element (RE) selected from the group consisting of ruthenium, osmium, iridium and osmium. And further contains calcium. Further, the dielectric ceramic of the present invention has a first crystal group and a second crystal group as crystal grains, and the first crystal group contains crystal grains having the calcium concentration of 0.2 atom% or less as a main component of the barium titanate. The second crystal group contains crystal grains having the above calcium titanate as a main component and having a calcium concentration of 0.4 atom% or more.
Further, in the X-ray diffraction pattern of the dielectric ceramic of the present invention, it is indicated that the diffraction intensity of the (004) plane of the tetragonal barium titanate is greater than the diffraction intensity of the (004) plane representing the cubic crystal barium titanate, and When the area of the crystal grains constituting the first crystal group observed on the polished surface of the dielectric ceramic is a, and the area of the crystal grains constituting the second crystal group is b, b/(a +b) is 0.4 to 0.7, and the crystal grains constituting the first crystal group and the crystal grains constituting the second crystal group have an average particle diameter of 0.21 to 0.28 μm.
Further, the multilayer ceramic capacitor of the present invention is composed of a laminate and an external electrode, and the laminate system is formed by alternately laminating a dielectric layer composed of the dielectric ceramic and an internal electrode layer, and the external electrode is provided in the laminate. Both end faces are connected to the above internal electrode layer.
Further, the rare earth element is referred to as RE, which is based on the rare earth element (Rare earth). Further, in the present invention, the lanthanoid is included in the rare earth element.
The dielectric ceramic according to the present invention has a high dielectric constant and a small dielectric loss, and the temperature variation of the dielectric constant satisfies the X7R characteristic of the EIA standard. Further, even when the applied voltage is low, a high insulation resistance is obtained, and when the voltage is increased, the insulation resistance is lowered (the voltage dependency of the insulation resistance is small).
The multilayer ceramic capacitor of the present invention can have a high dielectric constant and a low dielectric loss by using the above dielectric ceramic as a dielectric layer, and the temperature variation of the dielectric constant satisfies the X7R characteristic of the EIA standard even if the dielectric layer is thin. The stratification still ensures high insulation, so the life characteristics in the high temperature load test are excellent.
The dielectric ceramic of the present invention contains barium titanate as a main component and contains 0.05 to 0.3 mol of vanadium in terms of V 2 O 5 and 0 to 0 in terms of MgO. 0.1 mol of magnesium, 0 to 0.5 mol of manganese in terms of MnO, and 0.5 to 1.5 mol of RE 2 O 3 in a rare earth element (RE) selected from the group consisting of ruthenium, osmium, iridium and osmium. Further, it contains calcium and has a first crystal group and a second crystal group as crystal grains, and the first crystal group is composed of crystal grains having a calcium concentration of 0.2 atom% or less as a main component and the calcium concentration is 0.2 atom% or less. The 2 crystal group is composed of crystal grains having a calcium concentration of 0.4 atom% or more as a main component, and the dielectric ceramic is characterized in that an X-ray diffraction pattern of the dielectric ceramic indicates a tetragonal system. The diffraction intensity of the (004) plane of barium titanate is greater than the diffraction intensity of the (004) plane representing the cubic crystal barium titanate, and the first crystal group is formed when observed on the polished surface of the dielectric ceramic. When the area of the crystal grains is a, and the area of the crystal grains constituting the second crystal group is b, b/(a+b) is 0.4 to 0.7, and crystals constituting the first crystal group are formed. The average grain size of the grains and the crystal grains constituting the second crystal group is 0.21 to 0.28 μm.
Thereby, the following dielectric ceramics can be obtained: a dielectric constant of 3600 or more, a dielectric loss of 13% or less, a temperature change of the dielectric constant satisfying the X7R characteristic of the EIA standard, and a pair of thickness per unit (1 μm) When the value of the applied DC voltage is changed from 3.15 V/μm to 12.5 V/μm, the insulation resistance is 5 × 10 8 Ω or more, and the insulation resistance at 3.15 V/μm and the insulation resistance at 12.5 V/μm The difference is as small as 0.2 × 10 8 Ω or less.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the microstructure of a dielectric ceramic of the present invention. The dielectric ceramic of the present invention is composed of a crystal grain 1a, a crystal grain 1b, and a grain boundary phase 2, wherein the crystal grain 1a has a Ca concentration of 0.2 atom% or less, and the barium titanate is mainly composed of a first crystal group. The particle 1b has a Ca concentration of 0.4 atom% or more, and barium titanate is mainly used to constitute a second crystal group.
In the dielectric ceramic of the present invention, the average grain size of the crystal grains 1 composed of the crystal grains 1a of the first crystal group and the crystal grains 1b of the second crystal group is 0.21 to 0.28 μm.
In other words, when the average grain size of the crystal grains 1 composed of the crystal grains 1a of the first crystal group and the crystal grains 1b of the second crystal group is less than 0.21 μm, the dielectric constant is less than 3600. When the average grain size of the crystal grains 1 composed of the crystal grains 1a of the crystal group and the crystal grains 1b of the second crystal group is larger than 0.28 μm, the dielectric constant becomes high, but the dielectric loss is more than 13%.
Here, the average particle diameter of the crystal grains 1 composed of the crystal grains 1a constituting the first crystal group and the crystal grains 1b constituting the second crystal group is obtained by the following method: for the cross section of the dielectric ceramic Grinding (ion grinding) the polished surface, inputting the image reflected by the transmission electron microscope to the computer, drawing a diagonal line on the screen, and imaging the contour of the crystal grain existing on the diagonal line After the treatment, the area of each particle was determined, and the diameter when replacing the circle having the same area was calculated, and the average value of about 50 crystal grains was calculated.
Further, regarding the Ca concentration in the crystal grains, about 30 crystal grains existing on the polished surface obtained by polishing the dielectric ceramic cross section were subjected to elemental analysis using a transmission electron microscope with an elemental analyzer. At this time, the spot size of the electron beam is set to 5 nm, and the analyzed portion is set to be in the range of the center position from the vicinity of the grain boundary to the center portion of the crystal grain, and is substantially equally spaced on a line drawn toward the center thereof. The analysis value is set to an average value of about 4 to 5 points between the vicinity of the grain boundary and the center, and Ba, Ti, Ca, V, Mg, which are detected from each measurement point of the crystal grain, The total amount of the rare earth element and Mn was set to 100%, and the Ca concentration at this time was determined. Wherein, the selected crystal grains are the following crystal grains: the area of each particle is obtained according to the contour of the image processing, and the diameter when replacing the circle having the same area is calculated, and the diameter of the crystal grain is determined as the average particle diameter. ±60% of the range.
In addition, the central portion of the crystal grain refers to a range surrounded by a circle having a radius of 1/3 of the radius of the inscribed circle as a radius of the inner circle of the crystal grain, and the grain boundary of the crystal grain The vicinity is in the range of 5 nm from the grain boundary to the inner side of the crystal grain. Secondly, the inner circle of the die is input to the computer by the image reflected by the transmission electron microscope, and an inscribed circle is drawn on the crystal grain on the screen to determine the central portion of the crystal grain.
Further, as described above, the dielectric ceramic of the present invention has crystal grains 1a constituting the first crystal group and crystal grains 1b constituting the second crystal group as crystal grains 1, and the ratio thereof is a crystal constituting the first crystal group. When the area of the particles 1a is a and the area of the crystal grains 1b constituting the second crystal group is b, b/(a+b) is 0.4 to 0.7.
In other words, when the ratio b/(a+b) of the area of the crystal grains 1a constituting the first crystal group and the area of the crystal grains 1b constituting the second crystal group is less than 0.4, the dielectric constant is less than 3600. When b/(a+b) is more than 0.7, although the dielectric constant is 3600 or more, there is a dielectric loss of more than 13%.
The area ratio of the crystal grains 1a constituting the first crystal group and the crystal grains 1b constituting the second crystal group constituting the dielectric ceramic is calculated using the area data used for obtaining the above average particle diameter.
The dielectric ceramic of the present invention contains barium titanate as a main component, and contains 90 to 0.3 mol of vanadium in terms of V 2 O 5 and 0 to 0 in terms of MgO. 0.1 mol of magnesium, 0 to 0.5 mol of manganese in terms of MnO, and 0.5 to 1.5 mol of RE 2 O 3 in a rare earth element (RE) selected from the group consisting of ruthenium, osmium, iridium and osmium. .
That is, the value of the direct current voltage applied per unit thickness (1 μm) is obtained from the value of the vanadium content in the range of less than 0.05 mol in terms of V 2 O 5 with respect to 100 Å of barium titanate. When the voltage is changed from 3.15 V/μm to 12.5 V/μm, the decrease in the insulation resistance is increased, and the high-temperature load life is shortened in the multilayer ceramic capacitor in which the dielectric ceramic as described above is used as the dielectric layer.
Further, when the content of vanadium is more than 0.3 mol in terms of V 2 O 5 with respect to 100 Å of barium titanate, the value of the DC voltage applied per unit thickness (1 μm) is 3.15 V/ At μm and 12.5V/μm, the insulation resistance is less than 10 8 Ω.
Further, a rare earth element selected from the group consisting of ruthenium, osmium, iridium and osmium is less than 0.5 mol in terms of RE 2 O 3 , and the value of the direct current voltage applied per unit thickness (1 μm) is 12.5. When V/μm, the insulation resistance is 1.5 × 10 8 Ω or less, and the decrease in insulation resistance is larger than the value of the insulation resistance when the DC voltage is 3.15 V/μm.
Further, the content of the rare earth element selected from the group consisting of ruthenium, osmium, iridium and osmium is more than 1.5 moles in terms of RE203, or the content of manganese is more than 0.5 mole in terms of MnO, both of which are The electrical constant is less than 3600.
Further, in the case where the content of magnesium is more than 0.1 mol in terms of MgO, the temperature change of the dielectric constant does not satisfy the X7R characteristic of the EIA standard, and there is a DC voltage applied per unit thickness (1 μm). When the values are 3.15 V/μm and 12.5 V/μm, the decrease in the insulation resistance is increased, so that the life characteristics in the high-temperature load test are lowered.
On the other hand, as described above, the dielectric ceramic of the present invention can obtain a dielectric ceramic having a dielectric constant of 3,600 or more and a dielectric loss of 13% or less, and a temperature change of the dielectric constant satisfying EIA. The standard X7R characteristics, in addition, when the DC voltage applied per unit thickness (1 μm) is 3.15 V/μm and 12.5 V/μm, the insulation resistance is 10 8 Ω or more, and the insulation resistance hardly decreases.
In the dielectric ceramic of the present invention, the barium titanate is used as a main component, and the barium titanate is composed of 100 mole, and contains vanadium in an amount of 0.05 to 0.3 mol in terms of V 2 O 5 in terms of MnO. In the case of a rare earth element (RE) selected from the group consisting of lanthanum, cerium, lanthanum and cerium, which is 0.5 to 1.5 moles in terms of RE 2 O 3 in terms of RE 2 O 3 , it is preferred that magnesium is converted in terms of MgO. 0 mole.
By setting the dielectric ceramic to the above composition, it is possible to have a high dielectric constant and a small dielectric loss, and the temperature variation of the dielectric constant satisfies the X7R characteristic of the EIA standard, and can be obtained by applying a low voltage. In this case, a higher dielectric resistance is obtained, and the dielectric resistance of the insulation resistance is smaller. In more detail, it is possible to obtain a high insulation resistance (inclination change) when the DC voltage applied per unit thickness (1 μm) of the dielectric layer is between 3.15 V/μm and 12.5 V/μm. Dielectric ceramics with small dielectric loss.
Further, in the dielectric ceramic of the present invention, barium titanate is used as a main component, and the barium titanate is composed of 100 mols, and contains vanadium in an amount of 0.05 to 0.3 mol in terms of V 2 O 5 . In the case where RE 2 O 3 is converted to 0.5 to 1.5 mols of rare earth elements selected from the group consisting of ruthenium, osmium, iridium and osmium, it is desirable that magnesium is 0 mol in terms of MgO, and manganese is converted to 0 mol in terms of MnO. ear.
By setting the above composition, a dielectric ceramic having a small voltage dependence of the insulation resistance can be obtained, and the dielectric loss can be further reduced. Here, magnesium is 0 mol in terms of MgO or 0 mol in terms of MnO, which means that magnesium or manganese is not actually contained, for example, inductive coupled plasma (ICP) analysis of dielectric ceramics. In the meantime, it means that each component is below the detection limit (0.5 μg/g or less).
Further, in the case where cerium, lanthanum, cerium, and lanthanum are contained in the rare earth element, it is difficult to form a hetero phase when it is dissolved in barium titanate, and high insulation can be obtained. From the standpoint of increasing the dielectric constant of the dielectric ceramic, it is more preferable.
In the present invention, in the dielectric ceramic of the present invention described above, it is preferable to further contain ruthenium in a range of 0.3 mol or less in terms of Tb 4 O 7 with respect to 100 Å of barium titanate. . Thereby, the insulation resistance of the dielectric ceramic can be improved, and when the dielectric ceramic is used as the dielectric layer of the multilayer ceramic capacitor, the life characteristics in the high-temperature load test can be further improved. If the content of cerium is more than 0.3 mol in terms of Tb 4 O 7 , there is a possibility that the dielectric constant of the dielectric ceramic is lowered. Further, in order to obtain a sufficient effect due to the presence of ruthenium, it is preferable to contain 0.05 mol or more.
Further, in the present invention, in the dielectric ceramic of the present invention described above, it is preferable that the barium titanate is formed in a range of from 0.3 to 0.7 mol in terms of Yb 2 O 3 with respect to 100 Å. Further contains 镱. Thereby, the insulation resistance at 125 ° C required by the X7R characteristics can be increased to 2 × 10 7 Ω or more, and the change in dielectric constant can be suppressed even if the calcination temperature is changed (for example, the change is about 20 ° C), even if it is used. A large calciner with uneven temperature in the furnace can still reduce the unevenness of the dielectric constant and thus improve the yield. If it is more than 0.7 mol, there is a concern that the life characteristics in the high temperature load test are lowered.
Further, in the X-ray diffraction pattern of the dielectric ceramic of the present invention, it is preferred that the (004) plane of the tetragonal barium titanate has a diffraction intensity greater than that of the (004) plane representing the cubic crystal barium titanate. Diffraction intensity.
Here, if the crystal structure of the dielectric ceramic of the present invention is further described in detail, the following is the following: The dielectric ceramic of the present invention is almost close to the single crystal of the tetragonal system even if the vanadium is dissolved in the crystal grains. Occupied by the crystalline phase.
Fig. 2(a) is a view showing an X-ray diffraction pattern of a sample No. 4 of the dielectric ceramic of the present invention in Tables 1 to 3 of the following examples, and Fig. 2(b) is the same as Tables 1 to 3. The X-ray diffraction pattern of the sample No. 32 of the dielectric ceramic of the comparative example.
Here, the conventional dielectric ceramics described in Patent Document 2 and Patent Document 3 have a crystal structure of a core-shell structure and correspond to the X-ray diffraction pattern of FIG. 2(b).
That is, in a dielectric ceramic composed of crystal grains having a core-shell structure using barium titanate as a main component, between the (004) plane and the (400) plane of the tetragonal barium represented by the barium titanate. The diffracted intensity of the (004) plane (the (040) plane and the (400) plane overlap) of the cubic crystal system is greater than that of the (004) plane of the tetragonal barium. Shooting intensity.
Moreover, by the dielectric ceramic formed by the crystal grains of the core-shell structure, the X-ray diffraction pattern shows that the crystal phase of the cubic crystal system has a larger ratio with respect to the crystal phase of the tetragonal crystal system, and thus the crystal is crystallized. The anisotropy becomes smaller. Therefore, the ray of the X-ray diffraction pattern (400) plane is shifted toward the low angle side, and the ray of the (004) plane is shifted toward the high angle side, and at least a part of the two ray rays overlap each other to become a wide-width winding. Rays.
The dielectric ceramics as described above are usually formed by adding an oxide powder such as magnesium or a rare earth element to a powder containing barium titanate as a main component, followed by reduction calcination. In the above case, since the crystal grains having the core-shell structure are small in the core portion, such as magnesium or a rare earth element, the amount of solid solution is small, so that the inside of the crystal grains is in a state of containing a large number of defects such as oxygen vacancies. Therefore, when a DC voltage is applied, it is considered that the oxygen vacancies inside the crystal grains are likely to be carriers for carrying charges, and the dielectric properties of the dielectric ceramic are lowered.
In contrast, the dielectric ceramic of the present invention is illustrated in FIG. 2( a ). In the X-ray diffraction pattern of the dielectric ceramic, it is preferable that the barium titanate represents the (004) plane of the tetragonal system. The intensity of the shot is greater than the diffraction intensity of the (004) plane of the cubic crystal system.
That is, the dielectric ceramic of the present invention is as shown in Fig. 2(a), and the barium titanate indicates the (004) plane (near 2θ = 100°) and the (400) plane (near 2θ = 101°) of the tetragonal system. The X-ray diffraction peak is clearly manifested, and the barium titanate which is expressed between the (004) plane and the (400) plane of the tetragonal barium titanate represents the (004) plane of the cubic crystal system (( The diffraction intensity of 040) the surface overlaps with the (400) plane is smaller than the diffraction intensity of the (004) plane of the tetragonal barium titanate.
In the dielectric ceramic of the present invention, when the barium titanate indicates the diffraction intensity of the (004) plane of the tetragonal system is Ixt, and the barium titanate indicates the diffraction intensity of the (004) plane of the cubic system. When Ixc is set, it is preferable that the Ixt/Ixc ratio is 1.4 or more. When the Ixt/Ixc ratio is 1.4 or more, the ratio of the crystal phase of the tetragonal crystal system is increased, so that the dielectric constant can be increased, and the rate of change of the insulation resistance can be further reduced, and the life characteristics in the high temperature load test can be improved. .
The dielectric ceramic of the present invention as described above is a substantially uniform crystal phase of tetragonal crystal even if it contains vanadium. Therefore, it is considered that such crystal grains are vanadium or other additive components which are solid-dissolved throughout. Therefore, it is considered that the occurrence of defects such as oxygen vacancies in the inside of the crystal grains is small, and it is considered that the dielectric properties of the dielectric ceramics when the DC voltage is applied are suppressed from being lowered.
That is, the oxygen vacancies in the dielectric ceramic of the present invention are such that the vanadium atom substituted for solid solution at the titanium site is coupled to the oxygen vacancy charge, and is electrically neutralized by generating a defect pair. Therefore, the promotion of conduction by the application of the electric field is reduced, and it is generally considered that even if the oxygen vacancy is present, the mobility is lowered, so that the insulation resistance in the high-temperature load test can be prevented from being lowered.
Further, in the dielectric ceramic of the present invention, other components may be contained in addition to the above components as long as the range of desired dielectric properties can be maintained, for example, as an auxiliary agent for improving sinterability, it can be dielectrically The ceramic contains a glass component or other additive component in a ratio of 0.5 to 2% by mass.
Next, a method of manufacturing the dielectric ceramic of the present invention will be described. The production method described below is an example, but the method is not limited thereto. First, as a raw material powder, a barium titanate powder having a purity of 99% or more (hereinafter referred to as BT powder) and a powder in which calcium is dissolved in barium titanate (hereinafter referred to as BCT powder) are prepared as an additive component. Preparing V 2 O 5 powder and MgO powder, further preparing oxide powder of at least one rare earth element of Y 2 O 3 powder, Dy 2 O 3 powder, Ho 2 O 3 powder, and Er 2 O 3 powder, and MnCO 3 powder. Further, when the dielectric ceramic contains cerium as a rare earth element, it is preferred to use Tb 4 O 7 powder as an oxide of a rare earth element. Further, when cerium is contained as the third rare earth element in the dielectric ceramic, Yb 2 O 3 powder is preferably used as the oxide of the rare earth element.
The BCT powder is a solid solution in which Ca is substituted for barium titanate which is a part of the A site as a main component, and is represented by (Ba 1-x Ca x )TiO 3 . The amount of substitution of Ca in the A site is preferably X = 0.01 to 0.2. When the amount of Ca substitution is within this range, a crystal structure in which grain growth is suppressed can be formed by the coexistence structure with the first crystal grains 1a. Therefore, in the case of use as a capacitor, excellent temperature characteristics can be obtained in the temperature range of use. In addition, Ca contained in the second crystal grains 1b is solid-dissolved in a state of being dispersed in the second crystal grains 1b.
Further, the average particle diameter of the BT powder and the BCT powder is preferably from 0.13 to 0.17 μm, particularly preferably from 0.15 to 0.17 μm. When the average particle diameter of the BT powder and the BCT powder is 0.13 μm or more, the first crystal grains 1 a and the second crystal grains 1 b have high crystallinity, and grain growth during sintering can be suppressed, so that the dielectric constant can be improved. And the advantage of reduced dielectric loss.
On the other hand, when the average particle diameter of the BT powder and the BCT powder is 0.17 μm or less, it is easy to dissolve the additives such as magnesium, a rare earth element, and manganese into the first crystal grains 1a and the second crystal grains 1b. Further, as described below, there is also an advantage that the crystal grains of the crystal grains 1a constituting the first crystal group and the crystal grains 1b constituting the second crystal group can be grown from the BT powder and the BCT powder before and after the calcination. The ratio is increased to the established range.
Oxide powder of at least one rare earth element of Y 2 O 3 powder, Dy 2 O 3 powder, Ho 2 O 3 powder, and Er 2 O 3 powder belonging to the additive, Tb 4 O 7 powder, Yb 2 O 3 The powder, the V 2 O 5 powder, the MgO powder, and the MnCO 3 powder are also preferably used in the same manner as the dielectric powder such as BT powder or BCT powder, or the like.
Next, the raw material powder is blended with respect to 100 moles of BT powder and BCT powder: the V 2 O 5 powder is blended at a ratio of 0.05 to 0.3 mol, and the MgO powder is blended at a ratio of 0 to 0.1 mol. MnCO 3 powder is blended in a ratio of 0 to 0.5 mol, and is selected from Y 2 O 3 powder, Dy 2 O 3 powder, HO 2 O 3 powder, and Er 2 O in a ratio of 0.5 to 1.5 mol in terms of RE 2 O 3 . (3 ) The rare earth element (RE) in the powder, and if necessary, the Tb 4 O 7 powder is added in a ratio of 0 to 0.3 mol, and the Yb 2 O 3 powder is added in a ratio of 0.3 to 0.7 mol to prepare a molded body. Then, the formed body is degreased and then calcined in a reducing atmosphere.
Furthermore, when manufacturing the dielectric ceramic of the present invention, glass powder may be added as a sintering aid as long as the range of dielectric properties required is maintained, and the total amount of BT powder and BCT powder which are the main raw material powders will be added. When the amount is 100 parts by mass, the amount thereof is preferably 0.5 to 2 parts by mass.
For the calcination temperature, in the case of using a sintering aid such as glass powder, it is preferably from 1050 to 1135 ° C for the reason of controlling the solid solution of the BT powder and the BCT powder and the grain growth of the crystal grains. On the other hand, sintering can be performed at a temperature of less than 1050 ° C without using a sintering aid such as glass powder by pressurization by a hot press method or the like.
In order to obtain the dielectric ceramic of the present invention, it is preferred to use BT powder and BCT powder of the microparticles, and to add a predetermined amount of the above additives to the above calcination temperature so as to average the BT powder and the BCT powder containing various additives. The calcination is carried out in such a manner that it is increased to about 1.4 to 2.1 times after calcination. The first crystal grain 1a and the second crystal grain 1b are vanadium or other additions so that the average grain size of the crystal grains after calcination is 1.4 to 2.1 times the average particle diameter of the BT powder and the BCT powder. The components are solid-dissolved throughout the entire layer. As a result, it is considered that the occurrence of defects such as oxygen vacancies in the crystal grains is suppressed, and a state in which carriers for carrying charges are formed is less.
Further, in the present invention, after calcination, heat treatment is again performed in a nitrogen atmosphere. The above heat treatment is to reoxidize the dielectric ceramic reduced when calcined in a reducing environment, and to restore the insulation resistance which is lowered by reduction upon calcination. The heat treatment temperature is preferably 900 to 1100 ° C from the viewpoint of suppressing further grain growth of the crystal grains 1 a constituting the first crystal group and the crystal grains 1 b constituting the second crystal group and increasing the amount of reoxidation.
Fig. 3 is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor of the present invention. External electrodes 4 are provided at both ends of the capacitor body 10. The capacitor body 10 is composed of a laminate body 10A in which a dielectric layer 5 and an internal electrode layer 7 are alternately laminated. The dielectric layer 5 is preferably formed by the dielectric ceramic of the present invention described above.
Further, although the laminated state of the dielectric layer 5 and the internal electrode layer 7 is simplified in FIG. 3, in the multilayer ceramic capacitor of the present invention, the dielectric layer 5 and the internal electrode layer 7 are formed to even hundreds of layers. The laminated body 10A.
According to the multilayer ceramic capacitor of the present invention as described above, by using the dielectric ceramic as the dielectric layer 5, a high dielectric constant and a low dielectric loss can be obtained, and the temperature variation of the dielectric constant satisfies the X7R characteristic of the EIA standard. In addition, it is possible to obtain a multilayer ceramic capacitor which is excellent in life characteristics in a high-temperature load test even when the dielectric layer 5 is thinned to ensure high insulation. According to the dielectric ceramic of the present invention, a high dielectric constant and a low dielectric loss can be achieved, and thus, for example, there is an advantage that energy loss can be reduced when used as a bypass capacitor, thereby improving a capacitor which can input and output a high-capacity charge. The function.
Here, the thickness of the dielectric layer 5 is preferably 3 μm or less, and particularly preferably 2.5 μm or less, in order to increase the capacity of the multilayer ceramic capacitor. The thickness of the dielectric layer 5 is preferably 1 μm or more in order to prevent unevenness in electrostatic capacitance and to stabilize the temperature characteristics of the capacitor.
The internal electrode layer 7 is preferably a base metal such as nickel (Ni) or copper (Cu), particularly in the realization of the dielectric layer of the present invention, in terms of suppressing the manufacturing cost even if the high build-up is performed. The aspect of simultaneous calcination of 5 is more preferably nickel (Ni).
The external electrode 4 is formed by, for example, baking Cu or an alloy paste of Cu and Ni.
Next, an example of a method of manufacturing a multilayer ceramic capacitor will be described. A ceramic paste is prepared by adding a special organic vehicle to the above-mentioned base material powder, and then the ceramic paste is formed into a ceramic green sheet by a sheet forming method using a doctor blade method or a die coating method. In the above case, the thickness of the ceramic green sheet is preferably from 1 to 4 μm in terms of maintaining a thin layer and a high insulating property for increasing the capacity of the dielectric layer 5.
A rectangular internal electrode pattern is printed on the main surface of the obtained ceramic green sheet. A conductor paste as an internal electrode pattern is preferably Ni, Cu or an alloy powder thereof.
The ceramic green sheets in which the internal electrode patterns are formed are stacked with the number of sheets required to overlap, and a plurality of ceramic green sheets having no internal electrode patterns are stacked thereon so that the upper and lower layers are the same number to form a sheet laminate. In the above case, the internal electrode patterns in the sheet laminate are shifted every half pattern in the longitudinal direction.
Then, the sheet laminated body is cut into a lattice shape, and the capacitor body molded body is formed so that the end portions of the internal electrode patterns are exposed. According to the laminated method as described above, the internal electrode patterns can be alternately exposed to the end faces of the capacitor body after cutting.
After the obtained capacitor body molded body was degreased, heat treatment was performed under the same calcination conditions and weak reduction environment as described above for the dielectric ceramic, thereby producing a capacitor body.
Finally, an external electrode paste is applied to both ends of the capacitor body and fired to form the external electrode 4. Further, a plating film can be formed on the surface of the external electrode 4 in order to improve mountability.
Hereinafter, dielectric ceramics and laminated ceramic capacitors of the present invention will be described in detail by way of examples, but the present invention is not limited to the following examples.
[Examples] [Example 1] <Production of laminated ceramic capacitors>
First, as a raw material powder, BT powder, BCT powder (composition of (Ba 1-x Ca x )TiO 3 , X = 0.05), MgO powder, Y 2 O 3 powder, Dy 2 O 3 powder, Ho 2 O 3 were prepared. Powder, Er 2 O 3 powder, Tb 4 O 7 powder (second rare earth element), MnCO 3 powder, and V 2 O 5 powder, and the various powders were mixed at a ratio shown in Table 1. These raw material powders were used in a purity of 99.9%.
The average particle diameters of the BT powder and BCT powder used are shown in Table 1. MgO powder, Y 2 O 3 powder, Dy 2 O 3 powder, Ho 2 O 3 powder, Er 2 O 3 powder, Tb 4 O 7 powder, MnCO 3 powder, and V 2 O 5 powder using an average particle diameter of 0.1 μm . The Ba/Ti ratio of the BT powder was set to 1. As the sintering aid, a glass powder composed of SiO 2 = 55, BaO = 20, CaO = 15, and Li 2 O = 10 (mole %) was used. The amount of the glass powder added is 1 part by mass based on 100 parts by mass of the BT powder.
Next, spherical raw zirconia having a diameter of 5 mm was used, and a mixed solvent of toluene and ethanol as a solvent was added to wet-mix the raw material powders. A polyvinyl butyral resin and a mixed solvent of toluene and ethanol are added to the wet-mixed powder, and the ceramic paste is prepared by wet mixing using 5 mm spherical zirconia of the same diameter, and is produced by a doctor blade method. Ceramic green sheets having a thickness of 2.5 μm.
A plurality of rectangular internal electrode patterns having Ni as a main component are formed on the ceramic green sheets. As the conductor paste for the internal electrode pattern, Ni powder having an average particle diameter of 0.3 μm was used, and 30 parts by mass of the BT powder for green sheets was added as a common material with respect to 100 parts by mass of the Ni powder.
Then, 360 pieces of ceramic green sheets printed with internal electrode patterns were laminated, and 20 pieces of ceramic green sheets having unprinted internal electrode patterns were laminated thereon, and pressed at a temperature of 60 ° C, a pressure of 10 7 Pa, and a time of 10 minutes. The laminate was laminated under the conditions and cut into a predetermined size to form a laminated molded body.
The obtained laminated body was heated in the air at a temperature elevation rate of 10 ° C / h to 300 ° C, and debonding treatment was carried out at this temperature. Then, after heating to 500 ° C at the same temperature increase rate, the temperature increase rate from 500 ° C was 300 ° C / h, and the mixture was calcined at 1115 to 1160 ° C for 2 hours in hydrogen-nitrogen. Then, it was cooled to 1000 ° C at a cooling rate of 300 ° C / h, and then subjected to heat treatment (reoxidation treatment) at 1000 ° C for 4 hours in a nitrogen atmosphere, and cooled at a cooling rate of 300 ° C / h to prepare a capacitor body. The size of the capacitor body was 0.95 × 0.48 × 0.48 mm 3 , the thickness of the dielectric layer was 2 μm, and the area of one layer of the internal electrode layer was 0.3 mm 2 .
Next, after the barrel body of the calcined capacitor was subjected to barrel polishing, an external electrode paste containing Cu powder and glass was applied to both end portions of the capacitor body, and baked at 850 ° C to form an external electrode. Thereafter, Ni plating and Sn plating were sequentially performed on the surface of the external electrode using an electrolytic roller machine to produce a laminated ceramic capacitor.
<evaluation>
The following evaluation was performed on the obtained multilayer ceramic capacitor. The evaluation system was set to 10 samples, and the average value was obtained.
(1) Dielectric constant
The electrostatic capacitance was measured under the measurement conditions of a temperature of 25 ° C, a frequency of 1.0 kHz, and a measurement voltage of 1 Vrms, and the obtained electrostatic capacitance was obtained by converting the thickness of the dielectric layer, the total area of the internal electrode layer, and the dielectric constant of the vacuum.
(2) Dielectric loss
The electrostatic capacity was measured under the same conditions.
(3) Temperature characteristics of dielectric constant
The electrostatic capacity was measured in the range of -55 to 125 ° C.
(4) Insulation resistance
The evaluation was carried out under conditions of a DC voltage of 3.15 V/μm and 12.5 V/μm. The insulation resistance is a value obtained by applying a DC voltage for 1 minute.
(5) High temperature load test
It was carried out at a temperature of 170 ° C under the conditions of an applied voltage of 30 V (15 V / μm). The number of samples in the high temperature load test was set to 20 samples.
(6) an average particle diameter of crystal grains composed of crystal grains constituting the first crystal group and crystal grains constituting the second crystal group
The cross section of the dielectric ceramic is polished (ion milling) until it can be observed using a transmission electron microscope, and the image reflected by the transmission electron microscope is input to the computer for the polished surface. Draw a diagonal line, perform image processing on the contour of the crystal grains existing on the diagonal line, and obtain the area of each particle, and calculate the diameter when replacing the circle having the same area to calculate about 50 crystal grains. Calculated by the average value. Further, the ratio of grain growth of the self-dielectric powder was evaluated as {(average grain size of crystal grains) / (average particle diameter of dielectric powder)} × 100 (%).
(7) Determination of b/(a+b)
Regarding the Ca concentration in the crystal grains, about 30 crystal grains existing on the polished surface of the dielectric layer after the cross-section of the laminated ceramic capacitor is laminated, using a transmission electron microscope with an elemental analyzer And carry out elemental analysis. At this time, the spot size of the electron beam was set to 5 nm, and the analyzed portion was set at a point where the crystal grains were distributed at substantially equal intervals on a straight line drawn from the vicinity of the grain boundary toward the center portion. The analyzed portion is in a range from the vicinity of the grain boundary to the center position of the central portion of the crystal grain, and is a point which is distributed substantially equidistantly on a straight line drawn toward the center thereof, and the analysis value is set to be near the grain boundary. The average value of the values of about 4 to 5 points is analyzed between the centers, and the total amount of Ba, Ti, Ca, V, Mg, rare earth elements, and Mn detected from each measurement point of the crystal grains is set to 100%. And determine the Ca concentration at this time.
In the analysis as described above, the crystal grains having a calcium concentration of 0.2 atom% or less are referred to as "crystals constituting the first crystal group", and the crystal grains having a calcium concentration of 0.4 atom% or more are referred to as "constituting 2 crystal grains of the crystal group." Further, in the above case, the selected crystal grains are the following crystal grains: the area of each particle is obtained by image processing based on the contour, and the diameter when replacing the circle having the same area is calculated, and the crystal of the diameter is obtained. The diameter of the particles is a crystal grain within a range of ±60% of the average particle diameter.
In the above measurement, the central portion of the crystal grain is set from the center of the inscribed circle of the crystal grain to a length of 1/3 of the radius, and on the other hand, the grain boundary of the crystal grain is set from the crystal grain. The grain boundary is in the region of 5 nm on the inner side. Furthermore, the inscribed circle of the die is used to draw an inscribed circle on the screen of the computer by the image reflected by the transmission electron microscope, and the central portion of the die is determined according to the image on the screen.
The area ratio b/(a+b) of the crystal grains constituting the first crystal group and the crystal grains constituting the second crystal group in the dielectric ceramic (where a represents the area of the crystal grains 1a constituting the first crystal group, b The area of the crystal grains 1b constituting the second crystal group is calculated from the data of the area of the average grain size of the crystal grains 1a and 1b for about 50 crystal grains.
(8) Analysis of the composition of the sample
The composition analysis of the sample of the obtained sintered body was carried out by ICP analysis or atomic absorption analysis. In the above case, the obtained dielectric ceramic is mixed with boric acid and sodium carbonate to be melted, and then dissolved in hydrochloric acid. First, qualitative analysis of the elements contained in the dielectric ceramic is performed by atomic absorption analysis, and then For each of the specified elements, the standard solution was diluted to obtain a standard sample, which was quantified by ICP emission spectroscopic analysis. Further, the amount of oxygen is determined by setting the valence of each element to the valence shown in the periodic table.
The composition of the formulation and the calcination temperature are shown in Table 1. The composition of each element in the sintered body is shown in Table 2. The results of the properties are shown in Table 3. Here, in the ICP analysis of the dielectric ceramic, the case where each component is below the detection limit (0.5 μg//g or less) is set to 0 mol.
As is apparent from the results of Tables 1 to 3, in Samples Nos. 1-4 to 7, 9 to 13, 15, 16, 19 to 22, 25, 26, 28 to 31, and 33 to 35 of the present invention, dielectric was used. When the constant is 3600 or more and the dielectric loss is 13% or less, and the temperature change of the dielectric constant satisfies the X7R characteristic of the EIA standard, the value of the DC voltage applied per unit thickness (1 μm) can be set to 3.15 V/μm. And dielectric ceramics with less reduction in insulation resistance at 12.5V/μm and less voltage dependence of insulation resistance. In Table 3, an index method in which E is added between the mantissa portion and the index portion is expressed. For example, "5.2E+08" means 5.2 × 10 8 (the same applies to Table 6 below). Further, the life characteristics in the high-temperature load test were 60 hours or more under conditions of 170 ° C and 15 V/μm.
In addition, the barium titanate is used as a main component, and the barium titanate is composed of 100 mols, and contains vanadium in an amount of 0.05 to 0.3 mol in terms of V 2 0 5 and manganese in an amount of 0 to 0.5 mol in terms of MnO. a rare earth element selected from the group consisting of ruthenium, osmium, iridium, and osmium in the range of 0.5 to 1.5 moles in terms of RE 2 O 3 , and converted to 0 moles in terms of Yb 2 O 3 and 0 moles in terms of MgO. In the sample Nos. 1-4 to 7, 9, 10, 15, 16, 19 to 22, 25, 26, 28 to 31, and 33 to 35 of magnesium, the following high dielectric ceramics can be obtained, that is, The dielectric loss can be made 12.7% or less, and the insulation resistance is increased (positive change) between the direct current voltage applied to the dielectric layer (1 μm) and the direct current voltage of 3.15 V/μm and 12.5 V/μm.
In addition, the barium titanate is used as a main component, and the barium titanate is composed of 100 mole, and contains vanadium in an amount of 0.05 to 0.3 mol in terms of V 2 O 5 and 0.5 to 1.5 in terms of RE 2 O 3 . The rare earth element selected from the group consisting of yttrium, lanthanum, cerium and lanthanum, and is 0 moles in terms of Yb 2 O 3 , 0 moles of magnesium in terms of MgO, and 0 moles of manganese in terms of MnO. In the sample Nos. 1-4 to 7, 9, 10, 15, 16, 19 to 22, 25, 26, 28 to 31, and 33 to 35, the dielectric loss can be further reduced.
Further, the barium titanate is composed of vanadium, a rare earth element, magnesium, and manganese in an amount specified by the present invention, and is converted to 0 moles in terms of Yb 2 O 3 . Compared with samples No. 1-4 to 7, 9 to 13, 15, 16, 19 to 22, 25, 26, 29 to 30, and 33 to 35 in which Tb 4 O 7 is converted to 0.05 to 0.3 mol. The dielectric resistance of the dielectric ceramic can be improved in the sample No. 28 containing no antimony. When the dielectric ceramic is used as the dielectric layer of the multilayer ceramic capacitor, the life characteristics in the high-temperature load test are further improved.
On the other hand, in the sample outside the scope of the present invention, the dielectric constant is lower than 3600, or the dielectric loss is greater than 13%, or the dielectric constant temperature variation does not satisfy the X7R characteristic of the EIA standard, or When the value of the DC voltage applied per unit thickness (1 μm) was 12.5 V/μm, the insulation resistance was less than 10 8 Ω, or the life characteristic of the high-temperature load test was 8 hours or less.
[Embodiment 2]
In each of the compositions of the present invention, as shown in Example 1, a sample of 0.35 mol in terms of Yb 2 O 3 was further added, and a sample was prepared and evaluated in the same manner as in Example 1 (sample No. 2-1~24).
Furthermore, the sample No. 1-6 of Example 1 was added in an amount of 0 to 0.9 mol in terms of Yb 2 O 3 , and the calcination temperature was set to 1135 ° C, and a sample was prepared in the same manner as in Example 1. Evaluation was performed (sample No. 2-25 to 31).
The blending composition and the calcination temperature are shown in Table 4. The composition of each element in the sintered body in terms of oxide is shown in Table 5. The results are shown in Table 6.
As is apparent from the results of Tables 4 to 6, the composition of the sample of the present invention as shown in Example 1 further contains Sample No. 2-1 to 0.35 m of Yb 2 O 3 . In any of the 24 compositions, the same characteristics as those of the sample containing no bismuth were obtained.
Further, in the sample No. 1-6 of the first embodiment, a sample No. 2-25 to 31 prepared by calcining at a temperature of 1135 ° C in a range of 0 to 0.9 mol in terms of Yb 2 O 3 was further added. The difference between the dielectric constants of Sample No. 2-27 to 30 and Sample No. 1-6 in the range of 0.3 to 0.7 m in terms of Yb 2 O 3 is less than 100, and is comparable to that of The sample having a content of 0.2 mol or less (sample No. 2-25, 26) had a small change in the calcination temperature with respect to the dielectric constant. Further, compared with Sample No. 2-31 containing 0.9 mol of Yb 2 O 3 equivalent, the life characteristics in the high temperature load test were as high as 45 hours or longer. Further, in the sample containing 0.3 to 0.7 mol of Yb 2 O 3 , the insulation resistance at 125 ° C was 2.1 × 10 7 Ω or more.
1. . . Grain
1a. . . Grain of the first crystal group
1b. . . Grain of the second crystal group
2. . . Grain boundary phase
4. . . External electrode
5. . . Dielectric layer
7. . . Internal electrode layer
10. . . Capacitor body
10A. . . Laminated body
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the microstructure of a dielectric ceramic of the present invention.
Fig. 2(a) is a view showing an X-ray diffraction pattern of a sample No. 4 of the dielectric ceramic of the present invention in the embodiment, and Fig. 2(b) is a sample of a dielectric ceramic belonging to the comparative example in the embodiment. No. 32 X-ray diffraction pattern.
Fig. 3 is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor of the present invention.

Claims (7)

  1. A dielectric ceramic containing barium titanate as a main component and containing 0.05 to 0.3 mol of vanadium in terms of V 2 O 5 and 0 to 0.1 in terms of MgO. mole of magnesium, in terms of MnO 0 to 0.5 mole of manganese, in terms of RE 2 O 3 of 0.5 to 1.5 molar selected from yttrium, dysprosium, holmium and erbium 1 of rare earth elements (REs), Further, it contains calcium as a crystal grain, and has a first crystal group composed of crystal grains having a calcium concentration of 0.2 atom% or less as a main component of the barium titanate; and a second crystal group The barium titanate is composed of crystal grains having a calcium concentration of 0.4 atom% or more as a main component, and is characterized by: (004) surface of the tetragonal barium titanate in the X-ray diffraction pattern of the dielectric ceramic. The diffraction intensity is greater than a diffraction intensity indicating a (004) plane of the cubic crystal barium titanate, and the area of the crystal grains constituting the first crystal group observed from the polished surface of the dielectric ceramic is a, When the area of the crystal grains constituting the second crystal group is b, b/(a+b) is 0.4 to 0.7, and the first crystal group is formed. Crystal grains and the crystal grains constituting the average particle diameter of the second group of crystals is 0.21 ~ 0.28μm.
  2. The dielectric ceramic of claim 1, wherein the magnesium is 0 mol in terms of MgO.
  3. The dielectric ceramic of claim 2, wherein the manganese is 0 mol in terms of MnO.
  4. The dielectric ceramic according to any one of the first to third aspects of the present invention, wherein the barium titanate is formed in an amount of 0.3 m or less in terms of Tb 4 O 7 with respect to 100 mol of the barium titanate.
  5. The dielectric ceramic according to any one of claims 1 to 3, wherein the barium titanate is further composed of 0.3 to 0.7 m in terms of Yb 2 O 3 with respect to 100 mol of the barium titanate.
  6. The dielectric ceramic according to any one of claims 1 to 3, wherein a diffraction intensity indicating a (004) plane of the tetragonal barium titanate is Ixt, which means that the cubic titanium is When the diffraction intensity of the (004) plane of the acid bismuth is set to Ixc, the Ixt/Ixc ratio is 1.4 or more.
  7. A multilayer ceramic capacitor characterized in that it is composed of a laminate body and an external electrode, and the above-mentioned laminated system alternates a dielectric layer composed of a dielectric ceramic according to any one of claims 1 to 3 with an internal electrode layer. The external electrodes are provided on both end faces of the laminate and connected to the internal electrode layer.
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TW200716507A (en) * 2005-08-29 2007-05-01 Kyocera Corp Dielectric ceramic and method for manufacturing the same, and multilayer ceramic capacitor
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TW200716507A (en) * 2005-08-29 2007-05-01 Kyocera Corp Dielectric ceramic and method for manufacturing the same, and multilayer ceramic capacitor
JP2007258661A (en) * 2005-09-28 2007-10-04 Kyocera Corp Laminated ceramic capacitor and its manufacturing method
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