Dielectric ceramic composition for microwave use

Details Dielectric ceramic composition for microwave use Dielectric ceramic composition for microwave use

2002-07-25

2004-05-11

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Titanate, zirconate, stannate, niobate, or tantalate or...

Reexamination Certificate

active

06734126

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a dielectric ceramic composition for microwave use having a relative permittivity &egr;r of 35 to 45, Qf
0
value of at least 50,000 GHz (at 7 GHz) and a dielectric characteristic of &tgr;f=0±10 ppm/° C. employed for microwave communication filters, milliwave communication filters, oscillators, inductor antennas, and frequency adjusting rods etc.
BACKGROUND ART
Dielectric ceramic compositions are widely employed in the high-frequency region such as microwaves and milliwaves in for example dielectric resonators, dielectric substrates for MIC and waveguides. The characteristics that these are required to have are: (1) a large relative permittivity &egr;r to meet demands for miniaturization, since the wavelength is reduced to 1/&egr;r
1/2
in a dielectric, (2) low dielectric loss at high frequency i.e. high Q value, and (3) small and stable temperature coefficient &tgr;f of resonance frequency.
Conventional examples of such a dielectric ceramic composition are La—Ti—Al—O based compositions (see Japan, J. Appl. Phys. 36 (1997) 6814), which have &egr;r=36, Qf
0
value=45,000 GHz, and &tgr;f=−2 ppm/° C., but their Qf
0
values are low.
Also, in the case of Ba(Zn
1/3
Nb
2/3
)O
3
based compositions (published in: Electronics/Ceramics September 1993 September page 3), &egr;r=41, Qf
0
value=86,000 GHz, and &tgr;f=+31 ppm/° C., but a dielectric ceramic composition of small &tgr;f is not obtained.
Recently, La
2
O
3
.Al
2
O
3
.SrO.TiO
2
based composition or La
2
O
3
.Al
2
O
3
.SrO.TiO
2
.CaO based composition or composition containing one or two or more of Ce, Nb, Ta, Y, Zr, V, Cr, Mo, W, Co, Ni, Cu, Zn, Sn, Bi, B, or Si in the aforementioned ceramic compositions (see Laid-open Japanese Patent Publication H. 11-130528) has been proposed.
Regarding the dielectric characteristic of these ceramic compositions, they have excellent dielectric characteristics with &egr;r of more than 30, Qf
0
value more than 25,000 GHz (at 1 GHz) and &tgr;f less than +30 (ppm/° C.), but dielectric ceramic compositions of low &tgr;f are not obtained. Recently, with increasingly severe demands for miniaturization of portable terminal electronic equipment, materials of even better dielectric performance are being demanded.
DISCLOSURE OF THE INVENTION
In view of the foregoing demands, an object of the present invention is to provide a dielectric ceramic composition for microwave use having a relative permittivity &egr;r of 35 to 45, Qf
0
value of at least 50,000 GHz (at 7 GHz) and a dielectric characteristic of &tgr;f=0±10 ppm/° C.
The present invention studied various compositions with the object of obtaining a material capable of being controlled to a relative permittivity &egr;r of 35 to 45, Qf
0
value of at least 50,000 GHz (at 7 GHz) and a dielectric characteristic of &tgr;f=0±10 ppm/° C, and, as a result, discovered that, with an La
2
O
3
.Al
2
O
3
.SrO.TiO
2
based ceramic composition, by adding a specific quantity of Ga
2
O
3
to the aforesaid ceramic composition, the Qf
0
value could be increased, and, by further adding a specific quantity of Pr
2
O
3
, control of the &tgr;f value became possible, so that a ceramic composition capable of being controlled to a relative permittivity &egr;r of 35 to 45, Qf
0
value of at least 50,000 GHz (at 7 GHz) and a dielectric characteristic of &tgr;f=0±10 ppm/° C could be obtained, and thereby perfected the present invention.
Specifically, the present invention consists in a dielectric ceramic composition for microwave use characterized in that the compositional formula is expressed by aAl
2
O
3
.bGa
2
O
3
.cTiO
2
.dSrO.eLa
2
O
3
.fPr
2
O
3
, where a, b, c, d, e and f representing the mol ratios satisfy the following values (the case where b and f are simultaneously 0 is excluded).
a+b+c+d+e+f=1
0.079≦a≦0.167
0≦b≦0.017
0.333≦c≦0.412
0.333≦d≦0.412
0.035≦e≦0.167
0≦f≦0.101
BEST MODE FOR CARRYING OUT THE INVENTION
The reasons why, in the present invention, if the respective mol ratios of Al
2
O
3
, Ga
2
O
3
, TiO
2
, SrO, La
2
O
3
and Pr
2
O
3
are a, b, c, d, e, f, these mol ratios are respectively restricted to 0.079≦a≦0.167, 0≦b≦0.017, 0.333≦c≦0.412, 0.333≦d≦0.412, 0.035≦e≦0.167, and 0≦f≦0.101 are as follows.
If a is less than 0.079, &egr;r increases but the Qf
0
value is less than 50,000 GHz, but if it exceeds 0.167 mol ratio, &egr;r is lowered and drops to 35 or lower, which is undesirable.
If b exceeds 0.017 mol ratio, the Qf
0
value is lowered, resulting in the Qf
0
value dropping below 50,000 GHz, which is undesirable.
If c is less than 0.333 mol ratio, or is lowered, falling to 35 or lower, which is undesirable; if it exceeds 0.412 mol ratio, &egr;r increases, but the Qf
0
value drops below 50,000 GHz, which is undesirable.
If d is less than 0.333 mol ratio, &egr;r is lowered, falling to 35 or lower, which is undesirable; if it exceeds 0.412 mol ratio, &egr;r increases, but the Qf
0
value drops below 50,000 GHz, which is undesirable.
If e is less than 0.035 mol ratio, &egr;r is increased, but the Qf
0
value drops below 50,000 GHz, which is undesirable; if it exceeds 0.167 mol ratio, &egr;r is lowered, falling to 35 or lower, which is undesirable.
If f exceeds 0.101 mol ratio, If becomes quite large, becoming 10 ppm/° C. or more, which is undesirable.


REFERENCES:
patent: 6025291 (2000-02-01), Murakawa
patent: 6503861 (2003-01-01), Murakawa et al.
patent: 11071171 (1999-03-01), None
patent: 11106255 (1999-04-01), None
patent: 11130528 (1999-05-01), None
patent: 11092224 (1999-06-01), None
Patent Abstracts of Japan, vol. 1999, No. 09, Jul. 30, 1999 of JP 11 106285 (Kyocera Corp.), dated Apr. 20, 1999, entitled “Dielectric Ceramic Composition and Its Production”.
Patent Abstracts of Japan, vol. 1999, No. 10, Aug. 31, 1999 of JP 11 130528 (Kyocera Corp. dated May 18, 1999, entitled “Dielectric Ceramic Composition . . . Using the Composition”.
Patent Abstracts of Japan of JP 11-092224 (NGK Spark Plug Co. Ltd), dated Apr. 6, 1999, entitled “Dielectric Material”.

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