Compositions: ceramic – Ceramic compositions – Titanate – zirconate – stannate – niobate – or tantalate or...
Reexamination Certificate
1999-12-27
2001-06-12
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Titanate, zirconate, stannate, niobate, or tantalate or...
C333S219100
Reexamination Certificate
active
06245702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency dielectric ceramic composition and electronic devices using the same.
2. Description of the Related Art
Dielectric ceramics are widely used as materials for a dielectric resonator, a dielectric filter, a circuit board, etc., which are mounted on electronic apparatuses used in a high-frequency region such as a microwave or millimeter wave region, or the like, such as a cellular telephone, personal communication equipment, satellite broadcasting receiver, etc.
Dielectric characteristics required for such high-frequency dielectric ceramics include (1) a high dielectric constant (∈
r
) for complying with the need for miniaturization because the wavelength of electromagnetic waves is shortened to 1/(∈
r
)
½
in the dielectric material, (2) a low dielectric loss, i.e., a high Q value, (3) excellent temperature stability of resonance frequency, i.e., the temperature coefficient (&tgr;f) of the resonance frequency of about 0 ppm/° C., etc.
Examples of conventional known dielectric ceramic compositions include dielectric ceramic compositions such as Ba(Zn, Ta)O
3
system compositions (Japanese Patent Publication No. Sho-58-25068), Ba(Sn, Mg, Ta)O
3
system compositions (Japanese Patent Publication No. Hei-3-34164), (Zr, Sn)TiO
4
system compositions (Japanese Patent Publication No. Hei-4-59267), Ba
2
Ti
9
O
20
(Japanese Laid-open Patent Application No. Sho-61-10806).
However, Ba(Zn, Ta)O
3
based and Ba(Sn, Mg, Ta)O
3
based materials have a high Q value of 150,000 to 300,000 (at 1 GHz) but have a relatively low dielectric constant (∈
r
) of 24 to 30.
On the other hand, (Zr, Sn)TiO
4
based materials and Ba
2
TiO
20
have a relatively high dielectric constant (∈
r
) of 37 to 40, and a high Q value of 50,000 to 60,000 (at 1 GHz), but it is difficult to realize a relatively high dielectric constant (∈
r
) of over 40.
There has recently been increasing demand for decreasing the loss and miniaturizing electronic apparatus, and accordingly, there has been increasing demand for developing dielectric materials having excellent dielectric characteristics, particularly, both a high dielectric constant (∈
r
) and a high Q value. However, at present, it is impossible to satisfactorily comply with these demands.
SUMMARY OF THE INVENTION
Accordingly, it is one object of the present invention to provide a high-frequency dielectric ceramic composition having a relatively high dielectric constant (∈
r
) of, for example, 25 to 60, and a high Q value of, for example, 15,000 (at 1 GHz), and permitting arbitrary control of the temperature coefficient of the resonance frequency to about 0 ppm/° C., and a dielectric resonator comprising the dielectric ceramic composition.
In order to solve the above-described technical problems, a high-frequency dielectric ceramic composition of the present invention comprises a rare earth element (Ln), Mg, Ta, Ti and M (M: at least one of Ca and Sr), and has a composition represented by the composition formula aLnO
x/2
-bMgO-cTaO
5/2
-dMO-eTiO
2
, wherein a, b, c, d, e and x are mol % and are in the ranges of 0.100≦a≦0.350, 0.067≦b≦0.233, 0.033≦c≦0.117, 0.150≦d≦0.400, 0.150≦e≦0.400, a+b+c+d+e=1, and 3≦x≦4, respectively.
The a, b, c, d, e and x are preferably in the ranges of 0.150≦a≦0.200, 0.100≦b≦0.133, 0.050≦c≦0.067, 0.300≦d≦0.350, 0.300≦e≦0.350, a+b+c+d+e=1, and 3×4, respectively.
Another high-frequency dielectric ceramic composition of the present invention comprises a rare earth element (Ln), Mg, Ta, Ti and M (M: at least one of Ca and Sr), and has a composition represented by the composition formula yLn(Mg
2/3
Ta
1/3
)O
3
-(1−y)MTiO
3
, wherein y is in the range of 0.2≦y≦0.7.
The rare earth element (Ln) is preferably at least one of Y, La, Ce, Pr, Nd, Sm, Dy and Er, and is more preferably La.
Still another preferred high-frequency dielectric ceramic composition comprises a rare earth element (Ln and Lm), Mg, Ta, Ti and M (M: at least one of Ca and Sr), and has a composition represented by the composition formula xMTi
a
O
1+2a
-yLn(Mg
2/3
Ta
1/3
)
b
O
(3+3b)/2
-zLm(Mg
1/2
Ti
1/2
)
c
O
(3+3c)/2
(wherein x, y and z are by mol %); wherein a, b, and c are in the ranges of 0.950≦a≦1.050, 0.900≦b≦1.050, and 0.900≦c≦1.050; x, y and z are on a polygonal line or inside the line (except on lines A′B′ and C′D′) which connects point A′ (x=70, y=0, z=30), point B′ (x=50, y=0, z=50), point C′ (x=50, y=50, z=0) and point D′ (x=70, y=30 z,=0) in the ternary composition diagram of FIG.
3
.
The rare earth element (Ln, Lm) is preferably at least one of Y, La, Pr, Nd, and Sm. The element M is preferably Ca. The rare earth element (Ln, Lm) is more preferably at least one of La, Nd and Sm. The rare earth element (Ln, Lm) is most preferably La.
A further preferred high-frequency dielectric ceramic composition comprises a rare earth element (Ln or Lm), Mg, Ta, Sb, Ti and M (M: at least one of Ca and Sr), and has a composition represented by the composition formula by molar ratio, xMTi
a
O
1+2a
-yLn(Mg
2/3
Ta
1/3
)
b
O
(3+3b)/2
-zLm(Mg
2/3
Sb
1/3
)
c
O
(3+3c)/2
(wherein x, y and z are by mol %); wherein a, b, and c are in the ranges of 0.950≦a≦1.050, 0.900≦b≦1.050, and 0.900≦c≦1.050, respectively; x, y and z are on a polygonal line or inside the line (except on line C″D″), which connects point A″ (x=75, y=0, z=25), point B″ (x=55, y=0, z=45), point C″ (x=55, y=45, z=0) and point D″ (x=75, y=25 z=0), in a ternary composition diagram of FIG.
4
.
The rare earth element (Ln, Lm) is at least one of Y, La, Pr, Nd and Sm. The element M is preferably Ca. The rare earth element (Ln, Lm) is preferably at least one of La, Nd and Sm. The rare earth element (Ln, Lm) is most preferably La.
A dielectric resonator of the present invention is operated by electromagnetic field coupling of the dielectric ceramic with input/output terminals, wherein the dielectric ceramic is composed of any one of the above-described high-frequency dielectric ceramic compositions.
A dielectric filter of the present invention comprises the above dielectric resonator including external couplings.
A dielectric duplexer of the present invention comprises at least two dielectric filters, input/output connections to each of the dielectric filters, and an antenna connector connected to the dielectric filters in common, wherein at least one of the dielectric filters is the above-described dielectric filter.
A communication device of the present invention comprises the above dielectric duplexer, a transmitting circuit connected to at least one input/output connection of the dielectric duplexer, a receiving circuit connected to at least one input/output connection different from the input/output connection connected to the transmitting circuit, and an antenna connected to the dielectric duplexer.
REFERENCES:
patent: 4142164 (1979-02-01), Nishikawa et al.
patent: 5470808 (1995-11-01), Okuyama et al.
patent: 5781080 (1998-07-01), Ando
patent: 5824616 (1998-10-01), Kagato et al.
patent: 5846892 (1998-12-01), Takada
patent: 63-124602 (1988-05-01), None
patent: 4287403 (1992-10-01), None
Chemical Abstracts; vol. 120, No. 14; Apr. 4, 1994; Columbus, Ohio, US; Abstract No. 18102, Kuramitsu, Hidenori: “Dielectric Ceramic Compositions”; XP002144699; Abstract & JP 05 266711 A (Matsushita Electric Ind. Co., Ltd., Japan); Oct. 15, 1993.
Patent Abstracts of Japan; vol. 1999; No. 07; Mar. 31, 1999; & JP 08 017246 A (Korea Advanced List Inst. of Sci. Technol.); Jan. 19, 1996; Abstract.
Takagi Hitoshi
Tamura Hiroshi
Tatekawa Tsutomu
Group Karl
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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