Ceramic high dielectric composition

Details Ceramic high dielectric composition Ceramic high dielectric composition

1984-02-16

1985-12-10

McCarthy, Helen M.

Compositions: ceramic

Ceramic compositions

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

361321, 501139, 501152, C04B 3546

Patent

active

045580219

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to ceramic high dielectric composition to be used mainly as laminated ceramic capacitor.
2. Background Art
Hitherto many proposals have been made on ceramic high dielectric compositions with barium titanate (BaTiO.sub.3) as host material, and they have been used specially for disc type ceramic capacitors.
The barium titanate is a material having ferrodielectric characteristic, and its Curie point lies around 120.degree. C. Demarcated by this 120.degree. C., in the lower temperature side thereof it becomes tetragonal, and in the upper temperature side thereof it becomes cubic. And it is well known that in the tetragonal region it shows ferrodielectric characteristic and in the cubic region it shows paraelectric characteristic.
Since, ceramic of such sole barium titanate has a very large change of dielectric constant dependent on temperature and also has a large dielectric dissipation (tan .delta.) in a temperature range of about normal temperature, it is hardly used as capacitor independently; and hitherto devices are made to shift the Curie point to around the normal temperature and to decrease the temperature dependency by adding various additives. CaTiO.sub.3, BaZrO.sub.3, SrTiO.sub.3, BaSnO.sub.3 and etc. are known as representative of the additives. By adding these appropriately and by adjusting with a small amount composition, material having characteristics of X7R, Y5T, Y5V, Z4V and etc. of EIA (Electronic Industries Association) standard are offered. The fact is that these materials have been hitherto utilized generally as ceramic capacitors of thick disc type, for instance having 0.5-1 mm thickness of element.
In these years, miniaturization of capacitors is progressing corresponding to miniaturization of various electronics-related components, and the most in laminated ceramic capacitors. The laminated layer ceramic capacitor is that in which ceramic dielectric body is made into thin film of around 25-100 .mu.m and sandwiching comb type electrodes to form a multiple layer structure. And since a ratio of electrodes area to electrodes gap can be made very large, its capacitance per volume can be made as large as 100 times or larger in comparison with the ceramic disc type capacitor, and the same capacitance can be assured with as small volume as 1/10 or less, and therefore much miniaturization is easy.
When such ceramic dielectric thin film is used, however, it is the fact that conventional disc type ceramic composition can not be used as it is. That is, since a voltage per unit length is loaded 10 times or more than the conventional case, a material having small voltage-dependencies of ceramic dielectric constant and small dissipation factor have become to be needed. Besides, due to recent adoption of direct bonding system onto printed circuit board, such a strong material as is not destroyed by bending of the print circuit board is needed. Further, since in electronics tuner or the like using the laminated ceramic capacitors, the frequencies are shifting to higher band of high sensitivities, those having good high frequency characteristics become necessary also with regard to the laminated ceramic capacitors. Especially, those having characteristic of YD in JIS (Japanese Industrial) standard or characteristic of Y5T in EIA standard are requested by a large number in relation to electronic tuner, and those which have dielectric constant of 3000 or above and tan .delta. of 2.0% or lower and low equivalent series resistance at frequency band of 1-100 MHz are requested.


DISCLOSURE OF THE INVENTION

Accordingly, this invention provide a dielectric ceramic composition having high dielectric constant, a small dependency of characteristics on voltage, a large bending force, and moreover a small equivalent series resistance in the high frequency region, by having BaTiO.sub.3 as host material and to this adding CaTiO.sub.3 and Sb.sub.2 O.sub.3 to be contained, and further adding either of Nd.sub.2 O.sub.3, La.sub.2 O.sub.3 and Sm.sub.2 O.sub.3

REFERENCES:
patent: 3268783 (1966-08-01), Saburi
patent: 3490927 (1970-01-01), Kahn et al.
patent: 3753911 (1973-08-01), Walker et al.
patent: 4073989 (1978-02-01), Wainer
patent: 4086649 (1978-04-01), Hanold
patent: 4275521 (1981-06-01), Gerstenberger et al.
patent: 4280846 (1981-07-01), Charles et al.

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