Compositions – Piezoelectric
Reexamination Certificate
2000-02-08
2001-06-19
Koslow, C. Melissa (Department: 1755)
Compositions
Piezoelectric
C501S136000
Reexamination Certificate
active
06248254
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to piezoelectric ceramic compositions and piezoelectric ceramic devices using the same. In particular, the present invention relates to piezoelectric ceramic compositions which are useful as materials for piezoelectric ceramic filters, piezoelectric ceramic oscillators and piezoelectric ceramic vibrators, and relates to piezoelectric ceramic devices using the same.
2. Description of the Related Art
Piezoelectric ceramic compositions comprising lead titanate zirconate (Pb(Ti
x
Zr
1-x
)O
3
) or lead titanate (PbTiO
3
) as main components are extensively used in piezoelectric ceramic filters, piezoelectric ceramic oscillators and piezoelectric ceramic vibrators. In production of the piezoelectric ceramic compositions comprising lead titanate zirconate or lead titanate as the main components, lead oxide is generally used. Since lead oxide, however, is lost by vaporization during the production steps, the composition of the product is not uniform.
On the other hand, piezoelectric ceramic compositions comprising bismuth layered compounds such as (Ca
1-x
M
x
)Bi
4
Ti
4
O
15
as main components do not contain lead oxide and do not have the above problem. The bismuth-based piezoelectric ceramic compositions, however, have small electromechanical coupling coefficients kt and are not used in practice.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a piezoelectric ceramic composition which exhibits a high electromechanical coupling coefficient kt of at least 10%. The piezoelectric ceramic composition having such a high electromechanical coupling coefficient kt is useful as materials for piezoelectric ceramic filters, piezoelectric ceramic oscillators and piezoelectric ceramic vibrators.
It is another object of the present invention to provide a piezoelectric ceramic device using the piezoelectric ceramic composition.
According to a first aspect of the present invention, a piezoelectric ceramic composition comprising: a main component represented by the general formula CaBi
4
Ti
4
O
15
; and manganese as an auxiliary component in an amount of more than 0 to not more than about 1.5 percent by weight calculated as MnCO
3
.
The piezoelectric ceramic composition may further comprise a divalent metal other than Ca in an amount of more than 0 to 0.075 mole with respect to 1 mole of Bi in the main component. In such a case, the divalent metal other than Ca is at least one element selected from the group consisting of Mg, Sr and Ba.
Alternatively, the piezoelectric ceramic composition may further comprise a trivalent metal other than Bi in an amount of more than 0 to about 0.075 mole with respect to 1 mole of Bi in the main component. In such a case, the trivalent metal other than Bi is at least one element selected from the group consisting of La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Sc and Y.
According to second aspect of the present invention, a piezoelectric ceramic composition comprises: a main component represented by the general formula (Ca
1-x
M
1
x
)Bi
4
Ti
4
O
15
wherein M1 is one of divalent metals other than Ca and trivalent metals other than Bi, and 0<x≦0.3; and manganese as an auxiliary component in an amount of more than 0 to not more than about 1.5 percent by weight as MnCO
3
. The M1 in the general formula may be at least one element selected from the group consisting of Sr, Ba, Mg, La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Sc and Y.
According to a third aspect of the present invention, a piezoelectric ceramic composition comprises a main component represented by the general formula (Ca
1-x
M2
2x/3
)Bi
4
Ti
4
O
15
wherein M2 is a trivalent metal other than Bi, and 0<x≦0.45; and manganese as an auxiliary component in an amount of more than 0 to not more than about 1.5 percent by weight as MnCO
3
. The M2 in the general formula may be at least one element selected from the group consisting of La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb, Sc and Y.
According to a fourth aspect of the present invention, a piezoelectric ceramic device comprises a piezoelectric ceramic comprising the piezoelectric ceramic composition according to one of the first to third aspects, and electrodes.
The above objects, other objects, features, and advantages of the present invention will be further apparent from the following preferred embodiments.
REFERENCES:
patent: 4900702 (1990-02-01), Tsuboi et al.
Derwent abstract 1989-301168 for DD 267,877, pub. May 17, 1989.*
Derwent abstract 1989-240006 for SU 1,458,356 A, pub. Feb. 15, 1989.*
Derwent abstract 1981-67331D for SU 789,458 B, pub. Dec. 23, 1980.
Ando Akira
Hayashi Koichi
Kimura Masahiko
Sawada Takuya
Koslow C. Melissa
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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