Microwave dielectric ceramic composition

Details Microwave dielectric ceramic composition Microwave dielectric ceramic composition

2001-02-09

2001-12-18

Brunsman, David (Department: 1755)

Compositions: ceramic

Ceramic compositions

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

Reexamination Certificate

active

06331499

ABSTRACT:

DESCRIPTION
1. Technical Field
The present invention relates to a dielectric ceramic composition whose chief constituents are Ba, Ti, Sm. Nd, La, Ce, Pr, Bi and O
2
, additionally containing Eu
2
O
3
and having the properties ∈=82.5 to 92.5, Qf=6000 to 7300 GHz, &tgr;f=10 to −20 ppm/° C. which is capable of being employed as a dielectric resonance material or frequency adjusting rod thereof.
2. Background Art
In recent years, with the development of new media in the field of electronic technology, there has been rapid progress in miniaturization and digitization. In particular, in the field of communications using microwaves such as satellite communication, car phones, and mobile telephones, advanced miniaturization of components and high levels of reliability are being demanded.
In conventional microwave circuits cavity resonators or waveguides are employed as filter or transmission circuits so this has presented an obstacle to such miniaturization and enhanced reliability. Specifically, in cavity resonators or waveguides, basically the stability of air or vacuum as a propagation medium for electromagnetic waves is made use of; in order to miniaturize a microwave circuit portion as aforesaid, a propagation medium may be employed which has a larger dielectric constant than the dielectric constant of air or vacuum and which has the same level of high stability in respect of temperature as air or vacuum. If this is done, the propagation wavelength of the microwaves in the medium is 1/{square root over ((∈r))} (where ∈r is the relative permittivity), so the resonant wavelength is also 1/{square root over ((∈r))} and miniaturization can be achieved.
Previous microwave dielectric ceramic compositions that have been proposed include BaO—TiO
2
—Nd
2
O
3
—Bi
2
O
3
based ceramics (Laid-open Japanese Patent Publication Sho. 56-102003) and BaO—TiO
2
—Sm
2
O
3
—CeO
2
—Bi
2
O
3
based ceramics (Laid-open Japanese Patent Publication Sho. 62-187162). However, these materials suffered from the problems of their Qf value as a microwave communication dielectric being low at 4000 to 6500 and that adjustment of the temperature characteristic of frequency for various cavities was not easy.
Also, BaO—TiO
2
—Ln
2
O
3
based ceramics (where Ln
2
O
3
represents addition of Cr
2
O
3
to Nd
2
O
3
or Pr
6
O
11
) (Japanese Laid-open Patent Publication H. 7-169326) have a relative permittivity value (∈) of 91 to 93, but they were subject to the problems that their Q value is low at 5700 to 6000, and their temperature coefficient &tgr;f of resonance frequency is 6 to 9 ppm/° C., so that they cannot be employed in filters where the cavity material has a large temperature coefficient of resonance frequency, such as iron or copper.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a microwave dielectric ceramic composition whereby the problems of the prior art microwave dielectric ceramic composition are solved, which is of excellent relative permittivity (∈) characteristic, has a high Qf value, whereby adjustment of the temperature coefficient of the resonance frequency can easily be achieved, and which is ideal for filters where the cavity material has a large temperature coefficient of resonance frequency, such as iron or copper.
As a result of various studies of ceramic compositions with the object of providing a microwave dielectric ceramic composition of high Qf value and of improved temperature characteristic, the present inventors discovered that the properties: ∈=88.5 to 92.5, Qf=6000 to 7300 GHz, &tgr;f=3 to −10 ppm/° C. could be obtained by, in a BaO—TiO
2
—Nd
2
O
3
—Sm
2
O
3
based ceramic, substituting some of the Nd
2
O
3
by Bi
2
O
3
and further substituting some of the Nd
2
O
3
by Ln
2
O
3
(where Ln=La, Ce, Pr).
Furthermore, they discovered that, by substituting some of the aforementioned substituted Ln
2
O
3
with Eu
2
O
3
, a material could be provided with temperature coefficient &tgr;f of resonance frequency improved to 10 to −20 ppm/° C. and furthermore, the foregoing material may be sintered in the atmosphere; however, they discovered that, by sintering in an atmosphere containing at least 80% of oxygen, excellent properties in respect of the Qf value and/or &tgr;f value mentioned above are provided, and in addition the permittivity ∈ of frequency is improved to 82.5 to 92.5, thereby perfecting the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention consists in a microwave dielectric ceramic composition whose compositional formula is represented by:
Ba
6−3x
·{Sm
1−y
·(Nd
1−w−v
Eu
w
Ln
v
)
y−z
Bi
z
}
8+2x
·Ti
18
O
54
(where Ln=La,Ce,Pr)
where the values of x, y, z, y−z, w and v in the compositional formula satisfy the following values:
0.5<x<0.8, 0.3<y<0.5, 0<z<0.4, y−z>0, 0<w≦1,0<v≦1.
The reasons for the restrictions in the composition of the present invention will now be described. In a dielectric ceramic composition of compositional formula Ba
6−3x
·{Sm
1−y
·(Nd
1−w−v
Eu
w
Ln
v
)
y−z
Bi
z
}
8+2x
·Ti
18
O
54
, if x is less than 0.5, the Q value of the dielectric falls; if it is more than 0.8, the permittivity falls; these are therefore undesirable. Also, if y is less than 0.3, this tends to cause a drop in permittivity, while if it is more than 0.5, the Q value falls: these are therefore undesirable. Furthermore, if z exceeds 0.4, the Q value drops severely; this is therefore undesirable.
Also, in the above compositional formula, if w and v are both zero, the permittivity becomes low, and furthermore the temperature characteristic becomes negative and the temperature characteristic cannot be controlled even by addition of Eu, so it is desirable that w and v are not both zero: at least either one of w or v should preferably have a positive value.
The properties of the dielectric ceramic composition of the present invention can be continuously varied between ∈=82.5 to 92.5, temperature characteristic of frequency 10 to −20 ppm/° C. Excellent electrical properties can thereby be conferred on resonance cavities of various materials and sizes.


REFERENCES:
patent: 55131901 (1980-10-01), None
patent: 1128309 (1989-05-01), None
patent: 3192606 (1991-08-01), None
patent: 4265269 (1992-09-01), None
patent: 6-80467 (1994-03-01), None
patent: 597508 (1994-04-01), None
patent: 817243 (1996-01-01), None
patent: 8335810 (1996-12-01), None

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