High dielectric ceramic composition

Details High dielectric ceramic composition High dielectric ceramic composition

1999-09-09

2001-01-30

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

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

Reexamination Certificate

active

06180547

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates, in general, to a high dielectric ceramic composition and, more particularly, to a high dielectric ceramic composition which is superior in temperature properties with a low loss factor and can be sintered at low temperatures.
2. Description of Prior Art
Generally, a laminated ceramic capacitor is prepared by molding a dielectric ceramic raw material powder into a green sheet, printing on the green sheet a conductive paste comprised of a precious metal such as platinum or palladium, laminating a plurality of such green sheets under pressure, and sintering the lamination at 1,300~1,400° C. The precious metal, such as platinum or palladium, used as an internal electrode, however, is very expensive, causing an increase in the production cost of such laminated ceramic condensers.
In order to produce a laminated ceramic condenser at a reduced cost, there were suggested Pb-based, low temperature-sintered dielectrics whose internal electrodes were made of a high content of Ag. These dielectrics can be sintered at low temperatures, but suffer from a disadvantage of having dielectric loss factors as high as 3~6%. The conventional dielectrics can be found in many reports (for example, T. R. Shrout and A. Halliyal, “Preparation of Lead-based Ferroelectric Relaxors for Capacitors”, Am. Ceram. Soc. Bull., 66[4], 704 (1987); and M. T. Lanagan, N, Yang, D. C. Dube, and S. J. Jang, “Dielectric Behavior of the Relaxor Pb[Mg
1/3
Nb
2/3
]O
3
−PbTiO
3
Solid-Solution System in the Microwave Region”, J. Am. Ceram. Soc., 72[3], 481-83 (1989)).
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to overcome the problems encountered in prior art and to provide a dielectric capacitor composition which can be sintered at low temperatures and shows stable temperature characteristics in the range of operation temperatures with high dielectric constants.
It is another object of the present invention to provide a dielectric relaxor for capacitors, which meets the U.S. Industrial Standards, Z5U, Y5V and Y5S and has a low dielectric loss factor.
Based on the present invention, the above objects could be accomplished by a provision of a high dielectric ceramic composition, consisting of four components, Pb(Fe
1/2
Nb
1/2
)O
3
, Pb(Fe
1/2
Ta
1/2
)O
3
, Pb(Ni
1/3
Nb
2/3
)O
3
and Pb(Zn
1/3
Nb
2/3
)O
3
, in association with manganese nitrate (Mn(NO
3
)
2
.4H
2
O).
DETAILED DESCRIPTION OF THE INVENTION
The present invention contemplates a ceramic composition which is of a tetra-component system, each component being based on Pb(B
1
,B
2
)O
3
. Coming from combinations of lead oxide (PbO), ferric oxide (Fe
2
O
3
), niobium penta oxide (Nb
2
O
5
), tantalum penta oxide (Ta
2
O
5
), nickel oxide (NiO) and zinc oxide (ZnO), the tetra-component system consists of Pb(Fe
1/2
Nb
1/2
)O
3
, Pb(Fe
1/2
Ta
1/2
)O
3
, Pb(Ni
1/3
Nb
2/3
)O
3
, and Pb(Zn
1/3
Nb
2/3
)O
3
. In this tetra-component system, Pb(Fe
1/2
Nb
1/2
)O
3
has a function of raising the phase transition temperature to a high temperature, Pb(Fe
1/2
Ta
1/2
)O
3
of allowing low loss factors at low temperatures, Pb(Ni
1/3
Nb
2/3
)O
3
of reducing the temperature-dependent characteristics of the dielectric constant, and Pb(Zn
1/3
Nb
2/3
)O
3
of preventing the lowering of the dielectric constant. In addition, a transition metal, such as manganese, even in a small quantity, can contribute to a significant improvement in electric resistance and dielectric loss factor of the ceramic composition.
The dielectric ceramic composition of the present invention can be sintered at a temperature less than 1,100° C. and has a high dielectric constant enough to meet the temperature characteristics which show a maximum of allowable change rate of 22%-56% at a revision temperature range of 10° C.~85° C. and 22%~82% at a revision temperature range of −30° C.~85° C.


REFERENCES:
patent: 4379309 (1983-04-01), Wilson
patent: 5786048 (1998-07-01), Gesemann et al.

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