JPH0580764B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to dielectric porcelain, and particularly to dielectric porcelain suitable for high frequency applications having a high no-load Q in a high frequency region. [Prior Art] Generally, dielectric resonators and dielectric substrates used in signal circuits in high frequency ranges such as microwaves and millimeter waves have a high dielectric constant and a high no-load Q.
Furthermore, it is desirable to use dielectric ceramics that have a small absolute value of the temperature coefficient of the resonance frequency. Conventionally, _TiO2- based materials have often been used as this type of dielectric porcelain, such as BaO- _TiO2- based, _{ZrO2- SnO2
-TiO2-} based materials, recently Ba(Zn, Ta) _O3
There are materials such as Ba (Mg, Ta) O ₃ type, etc. Dielectric ceramics made of these materials have an unloaded Q of 3000 to 7000 and a dielectric constant of 20 at high frequencies of about 10 GHz.
~40, and the temperature coefficient of the resonance frequency is quite small, close to 0 ppm/°C. [Problem to be solved by the invention] By the way, in recent years, the frequencies used in communication equipment have become higher and higher, and the SHF used in satellite broadcasting etc.
There is a demand for dielectrically charged ceramics having a higher no-load Q than ever before. However, the above-mentioned conventional dielectrically charged ceramic material has a problem in that it cannot satisfactorily meet the demand for higher operating frequencies because its unloaded Q is about 7000 at most. Therefore, an object of the present invention is to
It is an object of the present invention to provide a dielectrically charged ceramic suitable for high frequency use, which has a high no-load Q of over 7000 and has excellent characteristics in terms of dielectric constant and temperature coefficient of resonance frequency. [Means for Solving the Problems] The present invention solves the above problems by using the general formula (): Ba{(Mg _1-xy Ni _x Co _y ) _1-z Ta _z }O _w ……( ) [In the formula, x, y and z are each 0.001≦
A number expressed by x≦0.40, 0.001≦y≦0.40, 0.61≦z≦0.72, and 0.002≦x+y≦
0.40 and w is Ba, Mg, Ni, Co and Ta
The present invention provides a dielectric ceramic having a composition represented by the following formula, and having a substantially perovskite crystal structure. In the general formula (), x, y, and z representing the composition ratio of each cation correspond to one of the objectives of the present invention.
They are important in increasing the no-load Q in the high frequency region, and their ranges are limited to achieve that purpose. The range of x is
0.001≦x≦0.40. For the range of y,
0.001≦y≦0.40. If x or y is less than 0.001, sintering becomes difficult or the no-load Q decreases. Moreover, when x or y exceeds 0.40, the no-load Q decreases. Also, the range of x+y is 0.002
≦x+y≦0.40, preferably 0.002≦x+
y≦0.35. When x+y is less than 0.002, sintering becomes difficult, and when it exceeds 0.40, the no-load Q decreases and the temperature coefficient of the resonance frequency increases sharply in the negative direction, which is not preferable. x+y is 0.002~0.40
In this case, it is possible to adjust the temperature coefficient of the resonant frequency to an arbitrary value. In particular, x+y is 0.002 ~
In the range of 0.15, the temperature coefficient is 0 to 10 ppm/℃
Furthermore, when x+y is in the range of 0.15 to 0.40, the temperature coefficient can be adjusted to any value in the range of 0 to 13 ppm/°C. z
The range is 0.61≦z≦0.72, preferably 0.66≦z≦0.68. When z is less than 0.61, sintering becomes difficult, and when z exceeds 0.72, the no-load Q decreases and the temperature coefficient of the resonance frequency increases rapidly in the positive direction, which is not preferable. Further, the dielectric ceramic of the present invention has a substantially perovskite crystal structure. This means that in X-ray diffraction, a phase with a perovskite crystal structure is observed, and no or almost no other phases are observed. There are no particular restrictions on the method of manufacturing the dielectric ceramic of the present invention, and it can be manufactured by a conventional method. For example, as raw materials for Ba, Mg, Ni, Co, and Ta components, powders of barium carbonate, magnesium oxide, nickel oxide, cobalt oxide, and tantalum oxide are weighed in proportions such that the respective cations have the desired composition. , mix them thoroughly. After subjecting the mixture to calcination, it is crushed,
Pressure mold. The dielectric ceramic of the present invention can be obtained by firing the obtained molded body at about 1500 to 1650°C. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples. As raw materials, barium carbonate, magnesium oxide, nickel oxide, cobalt oxide, and tantalum oxide powders with a purity of 99.9% by weight were prepared, and the values of x, y, and z in the general formula () were as shown in Table 1. Each sample number was weighed to match that of the 24 types of samples shown (samples marked with an asterisk are comparative examples, others are examples), placed in a pot of a ball mill with pure water, and wet-mixed for 16 hours. This mixture was taken out of the pot, dried at 150℃ for 5 hours, and then left in the air.
It was calcined at 1000°C for 2 hours. After calcining, it was crushed and sized through a 42-mesh sieve. The obtained powder was used in a mold with a pressure of 500 kg/cm ² and a diameter of 100 mm and a thickness of approximately 5 mm.
After primary molding into a disk shape of mm, it was compressed with a rubber press at a pressure of 2000 Kg/cm ² to obtain a molded body. This molded body was fired at 1650° C. for 4 hours in an oxygen stream to obtain porcelain. Dielectric constant (εr) and unloaded Q of the obtained porcelain
(Qu) was measured at a frequency of approximately 10 GHz using the dielectric cylindrical resonator method. In addition, the resonant frequency was measured in the temperature range from -10°C to 80°C, and the temperature coefficient (τf) of the resonant frequency at 20°C was calculated. The results obtained are shown in Table 1.

〔Effect of the invention〕

The dielectric ceramic of the present invention has excellent properties in terms of dielectric constant, no-load Q, and temperature coefficient of resonance frequency in a high frequency region around 10 GHz. In particular, the unloaded Q is a large value exceeding 7,000, and can be set to 10,000 or more depending on the composition.
Therefore, it is possible to cope with higher frequencies used in recent communication equipment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an X-ray diffraction chart of a dielectric ceramic according to an embodiment of the present invention.

Claims (1)

[Claims] 1 General formula: Ba{(Mg _1-xy Ni _x Co _y ) _1-z Ta _z }O _w [where x, y and z are each 0.001≦
A number expressed by x≦0.40, 0.001≦y≦0.40, 0.61≦z≦0.72, and 0.002≦x+y≦
0.40 and w is Ba, Mg, Ni, Co and Ta
A dielectric porcelain having a composition represented by the following formula and having a substantially perovskite crystal structure.