JPH08188463A - Dielectric ceramic composition for microwave - Google Patents

Abstract

PURPOSE: To improve a dielectric constant by blending a dielectric porcelain composition shown by a specific composition formula with a prescribed amount of one of Bi2 O3 , SnO2 and MnO2 . CONSTITUTION: Lithium oxide is mixed with CaO, Eu2 O3 and TiO2 in a fixed molar ratio and further with <=10mol% of one of Bi2 O3 , SnO2 and MnO2 . Then the mixture is mixed by a wet method in a ball mill and calcined at about 700-1,000 deg.C for about 1-5 hours. The calcined material is ground, mixed with an organic binder such as PVA, press molded under about 2,000-3,000kg/cm<2> , the molded article is baked at about 1,200-1,400 deg.C for about 1-5 hours to give a dielectric porcelain composition shown by the composition formula wLi2 O- xCaO-yEu2 O3 -zTiO2 -α (0.0<(w)<=25.0mol%; 0.0<(x)<=50.0mol%; 0.0<(y)<=30.0mol%; 0.0<(z)<=80.0mol%, w+x+y+z=100mol%; (α) is Bi2 O3 , SnO2 and MnO2 ) having a high dielectric constant. The similar dielectric porcelain composition is obtained even if Nb2 O5 or Ta2 O5 is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition used for a resonator material used in a microwave range of several GHz.

[0002]

2. Description of the Related Art In recent years, the high density of information has led to an increase in the frequency of signals used. Above all,
Microwaves in the several hundred MHz to several GHz band are used in various information transmission media such as satellite communication, mobile communication, broadcasting, and mobile identification devices.

Indispensable for such a medium is a resonator for a transmitter / receiver and a filter. These are manufactured by using a dielectric porcelain material that has a sufficient function in the high frequency band.

Conventionally, as a dielectric ceramic material of this type,
BaO-Ti because the high frequency characteristics are relatively good
O ₂ system, Ba {Zn _1/3 (Nb ・ Ta) _2/3 } O ₃ system, or (Zr
・ Sn) TiO ₄ series is used.

However, in a resonator or the like made of this dielectric ceramic material, if the permittivity of this dielectric is ε, the wavelength of the electromagnetic wave propagating in the dielectric will be as short as 1 / √ε. Therefore, the larger the dielectric constant ε is, the smaller the dimensions of the resonator and the like can be.

However, in the above dielectric ceramic material,
Its dielectric constant is usually as small as 20 to 40, and the size of the resonator becomes large in the microwave band in the range of 1 to 3 GHz.

On the other hand, as a material having a large dielectric constant,
For example, SrTiO ₃ (ε; about 300), CaTiO ₃ (ε; about 18)
However, the temperature coefficient τf of the resonance frequency of these materials is +1700 ppm / ° C, +
It is very large at 800 ppm / ° C, and stable use cannot be expected. Therefore, usually, in order to make the temperature coefficient τf of such a dielectric composition close to zero, the dielectric constant is large,
Moreover, a method of combining with a material having a negative temperature coefficient τf is used.

According to this method, a ceramic composition having a large dielectric constant and a small temperature coefficient τf can be obtained by selecting an appropriate material.

[0009]

However, in general, the larger the permittivity ε, the greater the temperature coefficient τf becomes on the plus side, so that the permittivity is large and the temperature coefficient τf is a negative value. However, it has been difficult to increase the Q value as a dielectric ceramic material for microwaves.

In view of the above points, the present invention has an object to obtain a dielectric ceramic composition having a large dielectric constant and Q value and a temperature coefficient τf of resonance frequency close to zero.

[0011]

The feature of the dielectric ceramic composition for microwaves of the present invention is that the composition formula is w.Li.
In _{2 O-x · CaO-y} · Eu 2 O 3 microwave dielectric ceramic composition represented by the -z · TiO _2, each of w, x,
y and z are 0.0 mol% <w ≦ 25.0 mol% 0.0 mol% ≦ x ≦ 50.0 mol% 0.0 mol% <y ≦ 30.0 mol% 0.0 mol% <z ≦ 80.0 mol% w + x + y + z = 100 mol% in the range of which Bi ₂ O ₃ , SnO ₂ or MnO ₂ is contained in an amount of 10 parts by weight or less, or Nb ₂ O ₅ or Ta _This is because it contained 10 parts by weight or less of any one of ₂ O ₅ .

[0012]

In the microwave dielectric ceramic composition of the present invention, a mixture of lithium oxide (Li ₂ O), europium oxide (Eu ₂ O ₃ ), titanium oxide (TiO ₂ ) and calcium oxide (CaO) is mixed with Bi By containing 10 parts by weight or less of either ₂ O ₃ , SnO ₂ or MnO ₂ or Nb ₂ O ₅ or Ta ₂ O ₅ , the relative permittivity εr and Q value are large, and the temperature coefficient τf You get a small one.

[0013]

EXAMPLES In producing the dielectric ceramic composition for microwaves of the present invention, first, the raw materials Li ₂ CO ₃ and CaCO are used.
Prepare ₃ , Eu ₂ O ₃ and TiO ₂ . Then, these are weighed and mixed so as to have a predetermined composition.

As an example, the composition ratios of Li ₂ O, CaO, Eu ₂ O ₃ and TiO ₂ are 9 mol% and 16 mol, respectively.
%, 12 mol% and 63 mol% are weighed and blended. Then, 3 parts by weight of Bi ₂ O ₃ is weighed and blended with this weighed material.

Next, after blending these, wet mixing is carried out with alcohol for 5 to 20 hours by a ball mill or the like, followed by calcination at 700 to 1000 ° C. for 1 to 5 hours. Subsequently, this calcined product is pulverized again by a ball mill or the like for 2 to 50 hours.

Then, an organic binder such as polyvinyl alcohol is added to this, and the mixture is granulated and classified to 2000 to 300.
Molding is performed by applying a pressure of 0 kg / cm ² . Subsequently, this molded product is fired at a temperature of 1200 to 1400 ° C. for 1 to 5 hours, and then both surfaces are polished so that the thickness of the fired product becomes about ½ of the diameter, and a measurement sample is completed.

The sample thus completed is
The dielectric constant (ε), the Q value, and the temperature coefficient (τf) of the resonance frequency were measured near the measurement frequency of 3 GHz by using the Coleman method. The measurement results are shown in Tables 1 and 2. In addition, as the sample used for the description in the examples, sample No. 3 in Table 1 was used.
Corresponds to this.

[0018]

[Table 1]

[0019]

[Table 2]

As shown by these, it can be seen that by including Bi ₂ O ₃ , SnO ₂ or MnO ₂ , the relative permittivity εr is slightly decreased, but the Q value is effectively increased. In particular, it can be seen that the Q value shows a maximum value in the vicinity of 3 to 5 parts by weight, whereas it rapidly decreases when the content is 10 parts by weight or more.

On the other hand, regarding the temperature coefficient, the absolute value is as small as about 30 ppm / ° C., which means that a good porcelain composition can be obtained.

Although manganese dioxide was used as manganese oxide in the examples, the present invention is not limited to this, and even if manganese monoxide or manganese trioxide having a different valence is used, the same effect can be obtained. It is effective. This situation applies to bismuth oxide as well, and it has been confirmed that the effect of the present invention can be obtained even if bismuth pentoxide is used.

Next, Table 3 and Table 4 show the characteristics when Nb ₂ O ₅ and Ta ₂ O ₅ were used as the inclusions. These inclusions were also formed by the same method as in the above-mentioned examples.

[0024]

[Table 3]

[0025]

[Table 4]

As can be seen from these, the characteristic changes of the relative permittivity εr and the Q value with respect to these contents are the same as those of the above-mentioned MnO ₂ and the like. That is, as shown in the same table, it can be seen that by including these, the relative dielectric constant εr slightly decreases, but the Q value increases. In particular, it can be seen that the Q value shows a maximum value in the vicinity of 3 to 5 parts by weight, while it becomes extremely low when the content is 10 parts by weight or more. Further, it can be seen that the absolute value of the temperature coefficient is as small as 30 ppm / ° C. at most, which is excellent.

Therefore, when the dielectric ceramic composition for microwaves of the present invention is used in, for example, a resonator, it is appropriately selected in consideration of the above-mentioned tendency when the amount of these contents is changed. Will be used.

Further, when the dielectric ceramic composition for microwaves of the present invention is used for microwaves, especially when the Q value and the above temperature coefficient are important parameters in design, even if the dielectric constant is Even if the value of is small, it can be used practically.

In the present invention, MnO ₂ , Bi ₂ O _{3 and the} like were used. In addition to these, magnesium oxide, cobalt oxide, nickel oxide, zinc oxide, tin oxide, selenium oxide, tellurium oxide, tungsten oxide, rare earth oxides are used. And so on,
These also have the same effects as MnO ₂ described in the examples.

In the present invention, Eu is used as a part of the main component.
₂O₃Was used, but instead of this Pr ₆O₁₁And La₂O₃use
The same effect can be expected for the used composition.
it can.

[0031]

According to the dielectric ceramic composition for microwaves of the present invention, it is possible to obtain one having a large dielectric constant and a high Q value in the microwave region and a temperature coefficient τf of the resonance frequency close to zero. A resonator or the like made of this composition can be downsized, and can be used with high reliability even in a use situation where the temperature change is relatively large.

Front page continuation (72) Inventor Kenichi Shibata 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A composition formula, In the microwave dielectric ceramic composition represented by _{w · Li 2 O-x ·} CaO-y · Eu 2 O 3 -z · TiO 2, each of w, x, y and z are 0.0 mol% <w ≦ 25.0 mol% 0.0 mol% ≦ x ≦ 50.0 mol% 0.0 mol% <y ≦ 30.0 mol% 0.0 mol% < z ≦ 80.0 mol% w + x + y + z = 100 mol% in the range, and 10% by weight or less of any one of Bi ₂ O ₃ , SnO _{2 and} MnO ₂ is contained therein. Porcelain composition. _2. A microwave dielectric ceramic composition represented by the following formula: w.Li ₂ O-x-CaO-y-Eu ₂ O ₃ -z-TiO ₂ , wherein w, x, y and z are 0.0 mol% <w ≦ 25.0 mol% 0.0 mol% ≦ x ≦ 50.0 mol% 0.0 mol% <y ≦ 30.0 mol% 0.0 mol% < z ≦ 80.0 mol% w + x + y + z = 100 mol% in the range, and contains 10 parts by weight or less of either Nb ₂ O ₅ or Ta ₂ O _{5 in} the dielectric ceramics for microwaves. Composition.