Compositions: ceramic – Ceramic compositions – Titanate – zirconate – stannate – niobate – or tantalate or...
Patent
1996-07-24
1998-12-08
Jones, Deborah
Compositions: ceramic
Ceramic compositions
Titanate, zirconate, stannate, niobate, or tantalate or...
C04B 3546
Patent
active
058468927
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a ceramic dielectrics and a method for forming the same.
DESCRIPTION OF THE PRIOR ART
Recently, ceramic dielectrics for high frequency signals have been widely utilized as a material for a resonator used in an antenna duplexer of radio communication equipments such as a mobile phone, a cellular phone and a cordless telephone, a voltage-controlled oscillator (VCO) etc., or a filter used in a tuner for CATV. By using a material having a high dielectric constant for these applications, the wave length of an electromagnetic wave can be shortened to the length of .di-elect cons..sub.r.sup.-1/2 (.di-elect cons..sub.r : relative dielectric constant) under vacuum, so that one wave length, half a wave length or a quarter of a wave length, a resonant condition of an electromagnetic wave, can be shortened. Therefore, when the material is used, electronic devices which process electric signals using a resonance of an electromagnetic wave can be easily downsized.
Characteristics required for the ceramic dielectrics for high frequency signals are: .di-elect cons..sub.r.sup.-1/2 in dielectrics, among ceramic dielectrics having the same resonant frequency, those which have a higher dielectric constant can be more downsized. Thus, the dielectric constant should be as high as possible; high-frequency-bandwidth, that is, the value of Q should be large; and variation should be small, that is, the dependency on temperature of the relative dielectric constant (.di-elect cons..sub.r) should be small.
Besides, a reference clock frequency of electronic devices has been chosen in the microwave-bandwidth in many cases, and at present, the clock frequency of electronic equipment for the consumer is 1 GHz or so. However, as an increase of information content delivered per unit time, and a controlling speed of electronic equipment and a processing speed of signals have become faster, electronic devices for a microwave which can be also used in a higher-frequency-bandwidth (several GHz) are becoming necessary. Accordingly, as a ceramic dielectrics constituting the electronic devices for a microwave, a material having a large value of Q is required to make a microwave loss as small as possible. In addition, a material having a high dielectric constant is required to make the electronic devices as small as possible.
Hitherto, as ceramic dielectrics having the above characteristics, a MgTiO.sub.3 -base and a CaTiO.sub.3 -base ceramic dielectrics have been known.
The conventional MgTiO.sub.3 -base ceramic dielectrics has a large value of Q, but has a relative dielectric constant (.di-elect cons..sub.r) of less than 20, which is not sufficiently high. As a result, it is difficult to downsize an element with the MgTiO.sub.3 -base ceramic dielectrics therein. On the other hand, the CaTiO.sub.3 -base ceramic dielectrics has a high dielectric constant, but has a small value of Q. As a result, it is not suitable for electronic devices processing signals in the high-frequency-bandwidth, and it is not suitable for being put to practical use because of its extremely high temperature coefficient of resonant frequency (.tau..sub.f).
Moreover, since it is difficult to control the temperature coefficient of resonant frequency (.tau..sub.f) without changing the composition of these materials, it is required to change the temperature coefficient of resonant frequency (.tau..sub.f) by adding several kinds of additives such as rare earth elements to the above materials. But a ceramic dielectrics available for several requirements cannot be easily provided since the characteristics in changing compositions have not been systematically examined.
DISCLOSURE OF THE INVENTION
The present invention was achieved in order to solve these problems, and it is an object to provide a ceramic dielectrics having a larger value of Q and a higher relative dielectric constant (.di-elect cons..sub.r) than ever, whose temperature coefficient of resonant frequency (.tau..sub.f) can be controlled to an optional value
REFERENCES:
patent: 5525562 (1996-06-01), Kagata et al.
Jones Deborah
Sumitomo Metal Industries Ltd.
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