U.S. patent application number 09/821769 was filed with the patent office on 2002-02-07 for dielectric ceramic composition, ceramic capacitor using the composition and method of producing thereof.
Invention is credited to Fujino, Shigehiro, Hirai, Nobutake, Kim, Jong Hee.
Application Number | 20020016246 09/821769 |
Document ID | / |
Family ID | 18612774 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020016246 |
Kind Code |
A1 |
Kim, Jong Hee ; et
al. |
February 7, 2002 |
Dielectric ceramic composition, ceramic capacitor using the
composition and method of producing thereof
Abstract
The present invention provides a dielectric ceramic composition,
a capacitor using the composition and the producing method, of
having a lower dielectric loss and a stable characteristics in high
frequency bandwidth, and enabling to use a base metal or a
carbon-based material as an electrode material by allowing
sintering at a low temperate, thereby resulting in lower cost. The
dielectric ceramic composition according to present invention, is
characterized in comprising a main component of formula
Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y) O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1) to which MuO.sub.2 of
0.05-15 wt %, at least one of 0.001-5 wt % selected from the group
consisting of Bi.sub.2O.sub.3PbO and Sb.sub.2O.sub.3 and a glass
component of 0.5-15 wt % are added based on the weight of the main
component.
Inventors: |
Kim, Jong Hee; (Seoul,
KR) ; Fujino, Shigehiro; (Yokohama, JP) ;
Hirai, Nobutake; (Yokohama, JP) |
Correspondence
Address: |
LOWE HAUPTMAN
GILMAN & BERNER, LLP
Suite 310
1700 Diagonal Road
Alexandria
VA
22314
US
|
Family ID: |
18612774 |
Appl. No.: |
09/821769 |
Filed: |
March 30, 2001 |
Current U.S.
Class: |
501/32 ; 501/137;
501/138; 501/139 |
Current CPC
Class: |
C04B 2237/343 20130101;
C04B 2237/066 20130101; C04B 2237/348 20130101; C04B 2237/345
20130101; C04B 2237/346 20130101; C03C 14/00 20130101; C04B
2237/068 20130101; B32B 18/00 20130101; C04B 35/47 20130101; C04B
2237/341 20130101; C04B 2237/68 20130101; C04B 2235/6562 20130101;
C04B 2237/565 20130101 |
Class at
Publication: |
501/32 ; 501/137;
501/139; 501/138 |
International
Class: |
C03C 014/00; C04B
035/49; C04B 035/48 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2000 |
JP |
2000-98271 |
Claims
What is claimed is:
1. A dielectric ceramic composition, comprising a main component of
formula Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1), MnO.sub.2 of 0.05-15
wt %, at least one of 0.001-5 wt % selected from the group
consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a glass
component of 0.5-15 wt %, based on He weight of the main
component.
2. The dielectric ceramic composition according to claim 1, further
comprising SiO.sub.2 of 0.01-5 wt % and Al.sub.2O.sub.3 of 0.01-5
wt %.
3. The dielectric ceramic composition according to claim 1, further
comprising a rare earth oxide of 0.001-2 wt %.
4. The dielectric ceramic composition according to claim 2, further
comprising a rare earth oxide of 0.001-2 wt %.
5. The dielectric ceramic composition according to claim 1, wherein
the glass component is ZnO-SiO.sub.2 based glass or
Li.sub.2-Al.sub.2O.sub.3-- SiO.sub.2 based glass.
6. The dielectric ceramic composition according to claim 2, wherein
the glass component is ZnO-SiO.sub.2 based glass or
Li.sub.2O-Al.sub.2O.sub.3- -SiO.sub.2 based glass.
7. The dielectric ceramic composition according to claim 3, wherein
the glass component is ZnO-SiO.sub.2 based glass or
Li.sub.2O-Al.sub.2O.sub.3- -SiO.sub.2 based glass.
8. The dielectric ceramic composition according to claim 4, wherein
the glass component is ZuO-SiO.sub.2 based glass or
Li.sub.2O-Al.sub.2O.sub.3- -SiO.sub.2 based glass.
9. The dielectric ceramic composition according to claim 3, wherein
the rare earth oxide is at least one selected from the group
consisting of La.sub.2O.sub.3, CeO.sub.2, Pr.sub.6O.sub.11,
Nd.sub.2O.sub.3, Sm.sub.2O.sub.3, Dy.sub.2O.sub.3, Ho.sub.2O.sub.3,
Er.sub.2O.sub.3, Tm.sub.2O.sub.3, and Yb.sub.2O.sub.3.
10. The dielectric ceramic composition according to claim 4,
wherein the rare earth oxide is at least one selected from the
group consisting of La.sub.2O.sub.3, CeO.sub.2, Pr.sub.6O.sub.11,
Nd.sub.2O.sub.3, Sm.sub.2O.sub.3, Dy.sub.2O.sub.3, Ho.sub.2O.sub.3,
Er.sub.2O.sub.3, Tm.sub.2O.sub.3, and Yb.sub.2O.sub.3.
11. A ceramic capacitor comprising: a ceramic body of the
dielectric ceramic composition according to claim 1; and electrodes
formed respectively on opposed surfaces of the ceramic body.
12. The ceramic capacitor according to claim 11, wherein said
electrode is base metal or carbon-based material.
13. A ceramic capacitor comprising: a ceramic body of the
dielectric ceramic composition according to claim 2; and electrodes
formed respectively on opposed surfaces of the ceramic body.
14. A ceramic capacitor comprising: a ceramic body of the
dielectric ceramic composition according to claim 3; and electrodes
formed respectively on opposed surfaces of the ceramic body.
15. A ceramic capacitor comprising: a ceramic body of the
dielectric ceramic composition according to claim 4; and electrodes
formed respectively on opposed surfaces of the ceramic body.
16. A ceramic capacitor comprising: a ceramic body of the
dielectric ceramic composition according to claim 5; and electrodes
formed respectively on opposed surfaces of the ceramic body.
17. A ceramic capacitor comprising: a plurality of sheets of
dielectric ceramic composition according to claim 1; and a
plurality of electrodes on each of sheets, wherein the sheets and
the electrodes are alternatively laminated.
18. The ceramic capacitor according to claim 17, wherein said
electrode is base metal or carbon-based material.
19. A method of producing a dielectric ceramic composition,
comprising the steps of: forming a bulk or a sheet with powder
including a main component of formula
Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1), to which MuO.sub.2
of 0.05-15 wt %, at least one of 0.001-5 wt % selected from the
group consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and
glass component 0.5-15 wt % are added based on the weight of the
main component; and firing the bulk or the sheet at
925-1080.degree. C.
20. The method according to claim 10, further comprising: providing
an electrode on a main surface of the sheet; laminating the sheet
in the thickness direction under pressure to form a laminate; and
firing the laminate at 925-1080.degree. C.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a dielectric ceramic
composition, more particular to a dielectric ceramic composition, a
ceramic capacitor using the composition and the producing method,
thereof having a lower dielectric loss and stable characteristics
in high frequency bandwidth, and enabling to use a base metal(e.g.
Cu, W etc) or a carbon-based material (e.g. C, graphite etc) as an
electrode material by allowing sintering at a low temperature, and
thereby reducing the production cost.
[0002] Conventionally, a dielectric property of a ceramic provides
a ceramic capacitor having larger capacitance and being more
miniature in size. The ceramic capacitor may be made of a material
selected from TiO.sub.2 having a rutile structure, MgTiO.sub.3,
CaTiO.sub.3 and SrTiO.sub.3, having a perovskite structure and the
mixture thereof.
[0003] This ceramic capacitor may be classified into a platelike
type and a laminate type. The platelike type capacitor is produced
by forming said material powder into some shaped body, such as
pellet(disc), rod(cylinder) or chip(angular), under pressure,
sintering the shaped body at 1200.degree. C.-1400.degree. C. to a
sintered body, and forming electrode at each surface of the
sintered body.
[0004] Also, the laminated type ceramic capacitor is produced by
mixing said material powder with organic binder and organic solvent
to prepare a slurry, forming green sheets from the slurry trough a
doctor bladding, printing the pattern of electrode comprising of a
noble metal, such as Pt and Pd, on each of the green sheets,
subsequently laminating said green sheets in the thickness
direction under pressure to form a laminate, and sintering the
laminate at 1200.degree. C.-1400.degree. C.
[0005] As described above, however, in the conventional ceramic
capacitor, the sintering process must be performed at a high
temperature ranging 1200.degree. C.-1400.degree. C., to obtain the
sintered body exhibiting a good electric characteristics and having
a high density.
[0006] For the laminated ceramic capacitor, particularly, in the
case of using a base metal as an electrode material, there has been
a problem to oxidize the base metal during the sintering process,
which occurs a high resistance layer formation between the ceramic
layers. To avoid the problem, the noble metal material, being
stable at high temperature, must be employed as an electrode
material, thereby resulting in high cost.
[0007] On application of a device for high frequency bandwidth, it
is preferred to have a low dielectric loss. And such device is
required to have a good electric characteristics such as a quality
value(Q), temperature property(this term means temperature changing
ratio of the capacity), and a high reliability, However, no current
dielectric material meets all the conditions.
[0008] Accordingly, there has been a need in the art to provide a
dielectric ceramic composition, ceramic capacitor using the
composition and the producing method to solve the problem as
described above.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a
dielectric ceramic composition and a producing method of the
dielectric ceramic composition of having a lower dielectric loss
and a stable characteristics in high frequency bandwidth and
enabling to use a base metal or a carbon-based material as an
electrode material by allowing sintering at a low temperature,
thereby reducing the production cost.
[0010] To achieve the above object, the present invention provides
the dielectric ceramic composition comprising a main component of
formula Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1 ) to which MnO.sub.2
of 0.05-15 wt %, at least one of 0.01-5wt % selected from the group
consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a glass
component of 0.5-15 wt % are added based on the weight of the main
component.
[0011] It is another object of the present invention to provide a
ceramic capacitor using the composition and a method of
manufacturing the ceramic capacitor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus, are
not limitative of the present invention and wherein:
[0013] FIGS. 1 illustrates cross-sectional structural views of a
platelike ceramic capacitor in accordance with example 1,
[0014] FIGS. 2 illustrates cross-sectional structural views of a
laminated ceramic capacitor in accordance with example 2.
DETAILED DESCRIPTION OF THE INVENTION
[0015] According to the present invention, the dielectric ceramic
composition is characterized in comprising a main component of
formula Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-yO.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1), to which MnO.sub.2
of 0.05-15 wt %, at least one of 0.001-5 wt % selected from the
group consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a
glass component of 0.5-15 wt % are added based on the weight of the
main component.
[0016] In the preferred embodiment, the dielectric ceramic
composition is produced by adding MnO.sub.2 of 0.05-15 wt %, at
least one of 0.001-5 wt % selected from the group consisting of
Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a glass component
0.5-15 wt % to a main component of formula
Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1). The resulting
composition can exhibit a high dielectric constant, a good
temperature property and a high quality value(Q). As a result, the
dielectric ceramic composition is suitable for using at high
frequency bandwidth.
[0017] The mole fraction of Sr is preferably 0.8(80 mol %) or more,
when the composition containing Sr of less than 0.8 is fired at
925.degree. C.-1080.degree. C. The sintering property of the
resultant is deteriorated.
[0018] The mole fraction of Ti is preferably 0.1(10 mol %) or less.
When the mole fraction of Ti is more than 0.1, the temperature
property as well as the quality factor(Q) are deteriorated.
[0019] MnO.sub.2 is added to the main component as a sintering aid
agent for enabling to sinter at a low temperature. The amount of
the agent is preferably 0.05-15 wt %. When the amount of MnO.sub.2
is less than 0.05 wt %, it does little function as an additives
resulting in a lower density of the sintered body. When the amount
of MnO.sub.2 is more than 15 wt %, the quality value is
deteriorated.
[0020] A metal oxide having a low melting point is added to the
main component for improving the temperature property. The metal
may be at least one selected from the group consisting of
Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3. The additive amount is
preferably 0.001-5wt %. When the additive is less than 0.001 wt %,
the temperature property cannot be improved. When the additive is
more than 5 wt %, the quality value is deteriorated.
[0021] The glass component is added thereto as a sintering aid
agent for enabling to sinter at a low temperature. The additive
amount is preferably 0.5-15 wt %, When the glass component is less
than 0.5 wt %, the temperature property cannot be improved. When
the glass component is more than 15 wt %, the quality value is
deteriorated.
[0022] The glass component employed in the present invention
preferably has a good wettability to the main composition
Sr.sub.xBa.sub.1-x(Zr.sub.- yTi.sub.1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1) and is softened
and/or melted at 925-1080.degree. C. Specifically, such glass
component may be ZnO-SiO.sub.2 based glass or
Li.sub.2O-Al.sub.2O.sub.3-SiO.sub.2 based glass.
[0023] In second embodiment of the present invention, SiO) of
0.01-5 wt % and Al.sub.2O.sub.3 of 0.01-5wt % based on the weight
of the main component are further added to the dielectric ceramic
composition to provide another dielectric ceramic composition.
[0024] SiO.sub.2 is used as an additive for improving the
temperature property. The amount of SiO.sub.2 is preferably about
0.01-5 wt %. When the amount of SiO.sub.2 is less than 0.01 wt %,
the temperature property cannot be improved. When the amount of
SiO.sub.2 is more than 5 wt %, the quality value is
deteriorated.
[0025] Al.sub.2O.sub.3 is used as an additive for improving the
quality value. The amount of Al.sub.2O.sub.3 is preferably about
0.01-5 wt %. When the amount of Al.sub.2O.sub.3 is less than 0.01
wt %, the quality value cannot be improved. When the amount of
Al.sub.2O.sub.3 is more than 5 wt %, the temperature property is
deteriorated,
[0026] In the third embodiment of the present invention, a rare
earth oxide of 0.01-2 wt % is further added to the dielectric
ceramic composition to provide another dielectric ceramic
composition based on the weight of the main component.
[0027] The rare earth oxide is used as an additive for improving
the temperature property. Preferably, the amount of the rare earth
oxide is about 0.01-2wt %. When the amount of the rare earth oxide
is less than 0.001 wt % the temperature property cannot be
improved. When the amount of the rare earth oxide is more than 2 wt
%, the quality value is deteriorated.
[0028] The rare earth oxide employed in the present invention has
preferably a good wettability to the main composition
Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1) ad has a grain
boundary layer, which is used to improve the sintering property
Specifically, such rare earth oxide may include at least one
selected from the group consisting of La.sub.2O.sub.3, CeO.sub.2,
Pr.sub.6O.sub.11, Nd.sub.2O.sub.3, Sm.sub.2O.sub.3,
Dy.sub.2O.sub.3, Ho.sub.2O.sub.3, Er.sub.2O.sub.3, Tm.sub.2O.sub.3
and Yb.sub.2O.sub.3.
[0029] Also, the present invention provides a ceramic capacitor
with the opposed surfaces comprising one of the dielectric ceramic
compositions as described above, each of which as electrode is
formed on, The electrode of the ceramic capacitor may be base metal
or carbon-based material, since the capacitor can be produced
through sintering at lower temperature.
[0030] Further, the present invention provides a ceramic capacitor
made by laminating alternatively electrodes and sheets comprising
one of the dielectric ceramic compositions as describe above.
[0031] The ceramic capacitor according to the present invention
exhibits a lower dielectric loss and stable characteristics, by
using one of the dielectric ceramic compositions as describe above.
Therefore, the ceramic capacitor is expected to have more improved
reliability. Moreover, it is advantageous that the dielectric
ceramic composition can be sintered at a low temperature of
925-1080.degree. C. Therefore, an inexpensive metal, such as a base
metal and a carbon-based material, can be used as an internal
electrode, thereby reducing the production cost.
[0032] The base metal having a good conductibility and a high
reliability is preferably employed as the electrode, which may be
at least one selected from the group consisting of Cu, Ni, W and
Mo, and the carbon-based material employed as the electrode may be
carbon(amorphous), graphite or the mixture.
[0033] In present invention, a ceramic capacitor manufacturing
method comprises the steps of forming powder comprising a main
component of formula Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3
(where 0.8.ltoreq.x.ltoreq.1 ; 0.9.ltoreq.y.ltoreq.1), to which
MnO.sub.2 of 0.05-15 wt %, at least one of 0.001-5 wt % selected
from the group consisting of Bi.sub.2Q3, PbO and Sb.sub.2O.sub.3,
and a glass component of 0.5-15 wt % are added based on the weight
of the main component, into a bulk or a sheet; and sintering the
bulk or a sheet at about 925-1080.degree. C.
[0034] According to the method, a sintering aid agent of MnO.sub.2
and glass composition can improve a wettability of a grain boundary
layer to bind powder particles and reduce the void fraction during
the sintering process even at low temperature of about
925-1080.degree. C. Thus, the sintered body having a high strength
and high density can be obtained at the low temperature.
[0035] In another embodiment of the present method, the method may
comprise the additional step of providing an electrode on a main
surface of the bulk or the sheet; laminating the bulk or the sheet
in the thickness direction under pressure to form a laminate; and
sintering the laminate at about 925-1080.degree. C.
[0036] According to this method, a base metal, such as Cu and Ni,
or a carbon-based material, such as amorphous carbon and graphite,
is used as an internal electrode, which is less expensive than
noble metal, such as Pt and Pd, resulting in the lower cost without
deteriorating the characteristics.
[0037] The embodiments of the present invention will now be
described by way of example.
EXAMPLE 1
[0038] Referring to FIG. 1, cross-sectional structural view of a
platelike ceramic capacitor in accordance with a first example is
shown in FIG. 1. The capacitor comprises a bulk shape dielectric
body 1, terminal electrodes 2 formed on the opposed surfaces of the
dielectric body 1, lead lines 3 connecting to the terminal
electrode, and an epoxy resin 4 encapsulating the dielectric body
and the terminal electrode 2.
[0039] The dielectric body 1 is made of a dielectric ceramic
composition comprising a main component of formula
Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.- 1-y)O.sub.3 (where
0.8.ltoreq.x.ltoreq.1; 0.9.ltoreq.y.ltoreq.1), to which MnO.sub.2
of 0.05-15 wt %, at least one of 0.001-5 wt % selected from the
group consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a
glass frit(glass component) of 0.5-15 wt % are added based on the
weight of the main component.
[0040] The dielectric body1 may include one of to the dielectric
ceramic composition fiber containing SiO.sub.2 of 0.01-5 wt % and
Al.sub.2O.sub.3of 0.01-5 wt %, the dielectric ceramic composition
further containing a rare earth oxide of 0.001-2 wt %, and the
dielectric ceramic composition further containing SiO.sub.2 of
0.01-5 wt %, Al.sub.2O.sub.3 of 0.01-5 wt % and rare earth oxide of
0.001-2 wt %.
[0041] The terminal electrode 2 comprises a conductive material
having a high reliability, such as Ag and Ag alloy. Preferably, Ag
alloy may include 90 Ag-10 Pd. The material of the terminal
electrode 2 may also include at least one selected from the group
consisting of Cu, Ni, W and Mo, or carbon, graphite or the
mixture.
[0042] This ceramic capacitor exhibits a stable dielectric
constant(.epsilon.), quality factor(Q) and temperature property(Tc)
even in high frequency bandwidth.
[0043] The method of manufacturing this capacitor will now be
described.
[0044] Each of Powdered
SBZT(Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3- ), MnO.sub.2,
at least one selected from the group consisting of Bi.sub.2O.sub.3,
PbO and Sb.sub.2O.sub.3, glass frit, SiO.sub.2, Al.sub.2O.sub.3 and
rare earth oxide was weighed as the predetermined amount.
[0045] In this example, each of powdered
Sr.sub.0.95Ba.sub.0.05(Zr.sub.0.9- 5Ti.sub.0.05)O.sub.3, MnO.sub.2,
PbO, glass frit, SiO.sub.2, Al.sub.2O.sub.3 and La.sub.2O.sub.3 was
weighed to prepare a dielectric ceramic composition as shown in
Table 1.
1 TABLE 1 Main component Additive B (mole fraction) Additive A (wt
%) Sintering Specimen Sr.sub.xBa.sub.1-x(Zr.sub.yTi.sub.1-y)O.sub.3
(wt %) Glass temperature number Sr Ba Zr Ti MnO.sub.2
Al.sub.2O.sub.3 SiO.sub.2 frit Sb.sub.2O.sub.3 Dy.sub.2O.sub.3
(.degree. C.) 1 1 0 1 0 0 0 0 0 0 0 1050 2 1 0 1 0 0.3 0 0 0.5 1.0
0 1000 3 1 0 1 0 0.3 0 0 3.0 1.0 0 950 4 1 0 1 0 0.3 0 0 11.0 1.0 0
950 5 1 0 0.95 0.05 5.0 0.1 0.05 2.5 0.5 0.01 950 6 1 0 0.95 0.05
5.0 0.1 0.05 2.5 0.6 0.01 900 7 1 0 0.95 0.05 5.0 0.1 0.05 2.5 0.5
0.01 1000 8 1 0 0.95 0.05 5.0 0.1 0.05 2.6 6.0 0.01 950 9 1 0 0.95
0.05 5.0 0.1 0.05 2.5 0.5 0.01 950 10 0.98 0.02 0.95 0.05 5.0 0.05
0.05 2.6 0.5 0.01 950 11 0.98 0.02 0.95 0.05 6.0 0.8 0.05 2.5 0.5
0.01 900 12 0.98 0.02 0.95 0.05 5.0 0.5 0.05 2.5 1.0 0.01 950 13
0.98 0.02 0.95 0.05 5.0 0.5 0.05 11.0 1.0 0.01 950 14 0.98 0.02
0.95 0.05 5.0 5.0 0.05 2.5 0.5 0.01 950 15 0.98 0.02 0.95 0.05 5.0
0.1 0.05 2.5 0.5 0.01 950 16 0.95 0.05 0.95 0.05 0.04 0 0 3.0 0 0
925 17 0.95 0.05 0.95 0.05 1.5 0 0 0.3 0 0 925 18 0.95 0.05 0.95
0.05 1.5 0 0 3.0 0 0 925 19 0.95 0.05 0.95 0.05 3 0.2 0.3 3.5 0.5
0.001 975 20 0.95 0.05 0.95 0.05 3 0.2 0.3 3.5 0.5 2.1 975 21 0.95
0.05 0.95 0.05 3 0.2 0.3 7.0 0.5 0.03 975 22 0.95 0.05 0.95 0.05 5
0.1 0.05 3.5 0.5 0.03 900 23 0.95 0.05 0.95 0.05 5 0.1 0.05 3.5 0.5
0.03 950 24 0.95 0.05 0.95 0.05 5 0.05 0.05 3.5 0.5 0.03 975 25
0.95 0.05 0.95 0.05 5 0.6 0.05 3.5 0.5 0.03 975 26 0.95 0.05 0.95
0.05 5 5.0 0.05 3.5 0.5 0.03 975 27 0.95 0.05 0.95 0.05 5 0.1 0.5
3.5 0.5 0.03 975 28 0.95 0.05 0.95 0.05 5 0.1 5.0 3.5 0.5 0.03 975
29 0.05 0.05 0.95 0.05 5 0.1 0.1 3.5 0.5 0.03 1050 30 0.95 0.05
0.85 0.15 3 0.2 0.3 3.5 0.5 0.03 975 31 0.0 0.2 0.95 0.05 5 0.1
0.05 3.5 0.5 0.03 960 32 0.8 0.2 0.95 0.05 5 0.1 0.05 5 0.5 0.03
900 33 0.75 0.25 0.95 0.05 5 0.1 0.05 3.5 0.5 0.03 950
comparison
[0046] The prepared components were wet-milled with water(or
organic solvent such as ethanol and acetone) in ball mill for
predetermined time, such as 24 hours. The resultant mixture was
dehydrated(or removal of the solvent, such as ethanol and acetone)
and dried. Specimen comprising different composition from thereof
the present invention was prepared as comparison(indicated by * in
the Table 1).
[0047] Then, the dried mixture was preliminary fired at
550-750.degree. C. , for 0.5-5.0 hours followed by pulverizing for
1-24hour with a mortar machine(or automatic pestle) to obtain the
fired powder having the desired granularity.
[0048] Subsequently, an appropriate amount of an organic binder was
added to the fired powder. The resultant was mixed and granularized
uniformly using a mortar machine and a like to obtain granular
powder having the desired granularity. Polyvinyl alcohol(PVA) was
employed as a organic binder. Other organic binder may include
ethylcellulose aqueous solution and acryl resin solution(acryl
binder).
[0049] Then, the pellet having a diameter of 20 and a thickness of
0.5 is formed from the granular powder using a forming machine,
followed by firing at 925-1080.degree. C. for 0.5-10 hours under
atmosphere, to obtain a disk-shaped dielectric body 1.
[0050] The composition of the present invention was fired at the
other temperature to prepare another specimen as
comparison(indicated by * in the Table 1).
[0051] Table 2 shows electric characteristics of each specimen, and
the comparison is indicated by "*".
2TABLE 2 Temperature Specimen Dielectric Resistance property Tc
number constant.epsilon. Q value R(.OMEGA. .multidot. cm)
(ppm/.degree. C.) 1* 13 230 1.6 .times. 10.sup.11 96 2 17 680 1.7
.times. 10.sup.12 89 3 23 2300 1.9 .times. 10.sup.12 6O 4* 22 380
1.5 .times. 10.sup.12 180 5 26 2170 2.0 .times. 10.sup.12 45 6* 20
410 1.8 .times. 10.sup.12 57 7 24 3060 2.1 .times. 10.sup.12 43 8*
22 290 1.3 .times. 10.sup.11 62 9 25 4740 2.0 .times. 10.sup.12 39
10 23 2310 1.8 .times. 10.sup.12 29 11* 14 220 1.5 .times.
10.sup.12 19 12 21 1760 1.9 .times. 10.sup.12 21 13* 22 360 1.1
.times. 10.sup.12 43 14 20 1230 1.8 .times. 10.sup.12 36 15 22 2120
1.9 .times. 10.sup.12 34 16* 21 380 1.7 .times. 10.sup.12 47 17* 16
270 2.1 .times. 10.sup.12 31 18 22 2670 3.2 .times. 10.sup.12 56 19
29 2350 2.6 .times. 10.sup.12 41 20* 25 640 1.9 .times. 10.sup.11
10 21 29 1800 2.1 .times. 10.sup.12 32 22* 17 230 1.6 .times.
10.sup.11 85 23 31 2450 2.2 .times. 10.sup.12 75 24 25 3050 1.5
.times. 10.sup.12 61 25 30 3500 1.8 .times. 10.sup.12 82 26 34 2700
1.2 .times. 10.sup.12 97 27 30 2300 1.9 .times. 10.sup.12 74 28 29
1970 1.5 .times. 10.sup.12 23 29 31 4890 2.1 .times. 10.sup.12 35
30* 41 470 1.2 .times. 10.sup.11 -67 31 33 2120 1.9 .times.
10.sup.12 39 32* 18 310 2.0 .times. 10.sup.12 19 33* 42 150 1.9
.times. 10.sup.12 125 *comparison
[0052] Wherein, the dielectric constant(.epsilon.) was measured at
25.degree. C. under the condition of frequency of 1 MHz and an
input voltage of 1V.sub.rms. The Q value was measured under the
condition of frequency of 1 MHz and an input voltage of 1V.sub.rms.
The temperature property(Tc) was calculated from the following
equation
Tc(ppm/.degree.C.)=(C2-C1.times.10.sup.6)/(C1.times.(125-25))
[0053] Wherein, the C1 is the capacitance at 125.degree. C. and the
C2 is the capacitance at 25.degree. C.
[0054] And the resistance(R(.OMEGA..multidot.cm)) was calculated by
using the voltage and the current, which were measured on applying
a direct voltage of 1000V for 1 minute at 25.degree. C.
[0055] Referring to the result of table 2, the dielectric
constant(.epsilon.), Q value and temperature property (Tc) were
stable even at high frequency in this example, while the
characteristic of the comparisons were deteriorated.
[0056] Further, when the specimen surfaces of these examples were
observed through a metallurgical microscope, it will be known that
no void was present at grain boundary and a dense sintering body
was constructed.
[0057] As described above, according to this example, the
dielectric composition exhibiting high dielectric constant, high Q
value and good temperature property, can be obtained by adding
MnO.sub.2 of 0.05-15 wt %, at least one of 0.001-5 wt % selected
from tie group consisting of Bi.sub.2O.sub.3, PbO and
Sb.sub.2O.sub.3 and a glass frit 0.5-15 wt % to a main component of
SBZT based on the weight of the main component and optionally
further adding SiO.sub.2 of 0.01-5 wt % and Al.sub.2O.sub.3 of
0.01-5 wt % and rare earth oxide of 0.001-2 wt % thereto. Thus, the
dielectric composition is capable of a dielectric capacitor having
stable characteristics and improved reliability.
[0058] According to the method of manufacturing the ceramic
capacitor, the ceramic capacitor having high density and strength
can be provided at the low temperature by forming a bulk or a sheet
from powder comprising a component of SBZT to which MnO.sub.2 of
0.05-15 wt %, at least one of 0.001-5 wt % selected from the group
consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a glass
component of 0.5-15 wt % are added based on the weight of the
component, and which optionally 0.01-5 wt % of SiO.sub.2 and 0.01-5
wt % of Al.sub.2O.sub.3 and 0.001-2 wt % of rare earth oxide ale
added thereto and firing the sheet or other resultant at
925-1080.degree. C.
EXAMPLE 2
[0059] FIGS. 2 illustrates cross-sectional structural view of a
laminated ceramic capacitor in accordance with second example. The
capacitor comprises a sheet-shaped dielectric layers 11, thin
internal electrodes 12 and terminal electrodes 13,14. This
laminated ceramic capacitor is comprised of eight dielectric
layers11 and seven thin internal electrodes 12, which are
alternatively laminated.
[0060] The dielectric layer11 is made of sheet-shaped ceramic
composition comprising a main component of SBZT to which MnO.sub.2
of 0.05-15 wt % at least one of 0.001-5wt % selected from the group
consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a glass
frit(glass component) of 0.5-15 wt % are added based on the weight
of the main component.
[0061] Alternatively, the dielectric layer 11 may include one of
the dielectric ceramic composition further containing SiO.sub.2 of
0.01-5 wt % and Al.sub.2O.sub.3 of 0.01-5 wt % the dielectric
ceramic composition further containing rare earth oxide of 0.001-2
wt %, and the dielectric ceramic composition further containing
SiO.sub.2 of 0.01-5 wt %, Al.sub.2O.sub.3 of 0.01-5wt % and rare
earth oxide of 0.001-2 wt % is added.
[0062] The internal electrode 12 and the terminal electrodes 13,14
include a conductive material having high reliability, for example,
Cu, Ni, W and Mo, or carbon, graphite or the mixture.
[0063] This laminated ceramic capacitor exhibits a stable
dielectric constant(.epsilon.), quality factor(Q) and temperature
property(Tc) even in RF region.
[0064] The method of manufacturing this laminated ceramic capacitor
will be described now.
[0065] Each of powdered SBZT, MnO.sub.2, at least one selected from
the group consisting of Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3,
glass frit, SiO.sub.2, Al.sub.2O.sub.3 and rare earth oxide was
weighed as the predetermined amount. Each composition was
wet-milled with water(or organic solvent such as ethanol and
acetone) in ball mill for predetermined time, such as 24 hours. The
resultant mixture was dehydrated(or removal of the solvent, such as
ethanol and acetone) and dried. Specimens comprising different
compositions from thereof the present invention were prepared as
comparisons(indicated by * in the Table 1).
[0066] Then, an appropriate amount of an organic binder was added
to the dried powder. Subsequently, the resultant powder was mixed
using a mortar machine, a mixing mill and a like to obtain a slurry
having desired viscosity. Polyvinyl alcohol(PVA) was employed as
the organic binder. Other organic binder may be employed, such as
ethylcellulose aqueous solution and acryl resin solution(acryl
binder).
[0067] Then, the slurry was deaired and formed into sheets through
doctor blading to obtaining a ceramic green sheet. A conductive
paste was printed as desired pattern on the green sheet. Thereby
the internal electrode layer was formed on the green sheet. The
conductive paste may include alloy containing at least one selected
from a group consisting of Cu, Ni, W and Mo, or carbon, graphite or
the mite.
[0068] Particularly, the conductive paste employed in present
invention may be a carbon paste made from a mixture powder of a
carbon powder and a graphite powder, W paste and Mo paste, as well
as a Cu paste, which is obtained by adding organic binder,
dispersing agent, organic solvent and, if necessary, reducing
agent, to Cu powder and then mixing thereof.
[0069] Then, the green sheets were laminated in the thickness
direction under pressure to form a laminate, followed by firing at
925-1080.degree. C. under inert gas atmosphere, such as N.sub.2
gas, or N.sub.2-H.sub.2 reductive atmosphere. Each terminal
electrode was formed on the opposed surfaces of the laminate. Thus,
the laminated ceramic capacitor can be produced through the process
of laminating alternatively the dielectric layer 11 and the
internal electrode 12.
[0070] As described above, for the laminated ceramic capacitor
according to this example, it can exhibit high dielectric constant,
high Q value and good temperature property, since it is comprised
of the composition obtained by adding MnO.sub.2 of 0.05-15 wt %, at
least one of 0.001-5 wt % selected from the group consisting of
Bi.sub.2O.sub.3, PbO and Sb.sub.2O.sub.3 and a glass frit of 0.5-15
wt % to a main component of SBZT based on the weight of the
component and optionally further adding SiO.sub.2 of 0.01-5 wt %
and Al.sub.2O.sub.3 of 0.01-5 wt % and rare earth oxide of 0.001-2
wt % thereto. Thus, the laminated ceramic capacitor is capable of
exhibiting stable characteristics and improved reliability in high
frequency.
[0071] According to the method of manufacturing the laminated
ceramic capacitor, the laminated ceramic capacitor having high
density and strength can be produced by forming the internal
electrode on the green sheet comprising a main component of SBZT to
which MnO.sub.2 of 0.05-15 wt %, at least one of 0.001-5 wt %
selected from the group consisting of Bi.sub.2O.sub.3, PbO and
Sb.sub.2O.sub.3 and a glass component of 0.5-15 wt % are added
based on the weight of the component, and which optionally
SiO.sub.2 of 0.01-5 wt % and Al.sub.2O.sub.3 of 0.01-5 wt % and
rare earth oxide of 0.001-2 wt % are added thereto, laminating the
green sheet in the thickness direction to form a laminate, firing
the laminate at 925-1080.degree. C. under inert gas atmosphere or
N.sub.2-H.sub.2 reductive atmosphere. Thus, an inexpensive base
metal and carbon-based material can be used as an electrode
material, in lie of a noble metal, such as Pt or Pd, since the
laminated ceramic capacitor is produced by the process of firing at
relatively low temperature. Therefore, the manufacturing method
according to the present invention can realize the lower cost
without deteriorating the characteristics.
[0072] As described above, according to the dielectric ceramic
composition of the present invention, the dielectric composition is
produced by adding MnO.sub.2 of 0.05-15 wt %, at least one of
0.001-5 wt % selected from the group consisting of Bi.sub.2O.sub.3,
PbO and Sb.sub.2O.sub.3 and a glass frit of 0.5-15 wt % to a main
component of SBZT based on the weight of the component and
optionally further adding 0.01-5 wt % of SiO.sub.2 and 0.01-5 wt %
of Al.sub.2O.sub.3 and 0.001-2 wt % of rare earth oxide thereto,
Thus, the dielectric composition cap; exhibit high dielectric
constant, high Q value and good temperature property, resulting in
the stable characteristics and improved reliability at high
frequency bandwidth, such as microwave.
[0073] For a ceramic capacitor, according to the present invention,
the capacitor can exhibit a low dielectric loss even at high
frequency bandwidth, since it is made of the dielectric ceramic
composition. Therefore, the present capacitor is suitable for RF
device. The present capacitor can also realize the lower cost
without deteriorating the characteristics, since all inexpensive
base metal or carbon-based material can be used as an electrode
material due to the low sintering temperature of 925-1080.degree.
C.
[0074] While the invention has been described in its preferred
embodiments, this should not be construed as limitation on the
scope of the present invention and can be modified and changed to
other various embodiments. Accordingly, the scope of the present
invention should be determined not by the embodiments illustrated,
but by the appended claims and their legal equivalents. In second
example, eight dielectric layers and seven internal electrodes are
laminated to form a laminate, but the number of the dielectric or
internal electrode may be changed to be suitable for the desired
capacitor and characteristics.
* * * * *