JPH06243722A - Dielectric ceramic composition for microwave - Google Patents

Abstract

PURPOSE:To obtain the ceramic composition having a large dielectric constant and a large Q value and a small temperature coefficient by using a specified composition made of each oxide of Li, Ca, Sm, Ti and Nd, La or Pr. CONSTITUTION:A ceramic composition represented by a composition formula w.Li2O-x.CaO-y.{(1-u).Sm2O3}-z.TiO2 is used. In the formula, A means Nd, La or Pr, and 0<x<100 mole %, 0<y<100 mole %, 0<x<100 mole %, w+x+y+z=100 mole %, and 0<w<1.0. A ceramic composition having a large dielectric constant and a small temperature coefficient is thereby obtained.

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 as a resonator material used in a microwave region of several GHz band.

[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.

Usually, the temperature coefficient τf of such a dielectric composition is
As a measure for making the value of zero close to zero, a method of combining with a material having a large dielectric constant and 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.

[0010]

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. I haven't found the right ingredients.

In addition, the dielectric ceramic material for microwaves must have a large Q value.

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 the resonance frequency close to zero.

[0013]

Means for Solving the Problems] It is a feature of the present invention a microwave dielectric ceramic composition, a composition _{formula, w · Li 2 O-x} · CaO-y · {(1-u) · Sm ₂ O ₃ -u
_{· A 2 O 3} -z ·} TiO 2 , however, A is, Nd, is La or Pr, 0 mol% <w <100 mol% 0 mol% <x <100 mol% 0 mol% <y <100 moles % 0 mol% <z <100 mol% w + x + y + z = 100 mol% 0.0 <u <1.0, and in the dielectric ceramic composition for microwave, the above w, x, y, z is 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% 0.0 <u <1.0.

[0014]

In the dielectric ceramic composition for microwaves of the present invention, lithium oxide (Li ₂ O), samarium oxide (Sm ₂ O ₃ ) and titanium oxide (TiO ₂ ) are further mixed in a mixed ratio to adjust the oxidation ratio. Calcium (CaO) and neodymium oxide (Nd)
₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ) or praseodymium oxide (Pr ₂ O ₃ ) is added to obtain a material having a large relative permittivity εr and Q value and a small temperature coefficient τf. .

[0015]

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.
₃ , La ₂ O ₃ , Sm ₂ O ₃ , and TiO ₂ are prepared. Then, these are weighed and mixed so as to have a predetermined composition.

As an example, the ratio of Sm ₂ O ₃ to La ₂ O ₃ , that is, u is 0.17, and Li ₂ O, CaO, Sm ₂ O ₃ and Nd ₂ O _{3 are used.}
And the composition ratio of TiO ₂ is 9 mol%, 16
Weigh and mix to be mol%, 12 mol% and 63 mol%.

Next, these powders are blended, wet-mixed with alcohol for 5 to 20 hours by a ball mill or the like, and then calcined at 700 to 1000 ° C. for 1 to 5 hours. Subsequently, this calcined product is again subjected to 2 with a ball mill or the like.
Grind for ~ 50 hours.

Next, 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, the 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 Table 1, Table 2 and Table 3. It should be noted that the sample used in the description of the examples corresponds to sample number 9 in Table 3.

When Pr is used as A, Pr ₂ O ₃ is used instead of Nd ₂ O ₃ used in the examples,
Furthermore, when using La as A, La ₂ O ₃
Should be used.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

As shown in the table, the relative permittivity εr gradually increases as the content of neodymium oxide, lanthanum oxide or praseodymium oxide increases, that is, as the u value increases.

On the other hand, the absolute value of the temperature coefficient is as small as about 30 ppm / ° C., which means that a good porcelain composition can be obtained. Further, the Q value tends to gradually decrease as the content of these oxides increases.

Therefore, when the dielectric ceramic composition for microwaves of the present invention is used in, for example, a resonator, the above-described tendency when the content of neodymium oxide, lanthanum oxide or praseodymium oxide is changed is exhibited. In consideration of this, it will be sufficient to appropriately select and use it.

When the microwave dielectric ceramic composition of the present invention is used for microwaves, especially when the Q value and the above temperature coefficient are important parameters in design, the dielectric constant is Even if the value of is small, it is practical.

In particular, when the dielectric ceramic composition for microwaves of the present invention is represented by Chemical Formula 1, it is preferable that the composition is within the range represented by Formula 1.

[0029]

[Chemical 1]

[0030]

[Equation 1]

In the present invention, by adjusting the mixing ratio of samarium oxide and neodymium oxide, lanthanum oxide or praseodymium oxide, a dielectric suitable for the microwave band could be obtained. By adjusting the ratio in this way, the dielectric constant can be maintained large while the temperature coefficient is kept small, and the Q value can also be increased.

[0032]

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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Shibata 2-18, Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A composition _{formula, w · Li 2 O-x} · CaO-y · {(1-u) · Sm 2 O 3 -u
_{· A 2 O 3} -z ·} TiO 2 where A, Nd, is La or Pr, and 0 mol% <w <100 mol% 0 mol% <x <100 mol% 0 mol% <y <100 moles % Dielectric ceramic composition for microwaves represented by 0 mol% <z <100 mol% w + x + y + z = 100 mol% 0.0 <u <1.0. 2. The microwave dielectric ceramic composition according to claim 1, wherein each of w, x, y, z and u is 0.0 mol% <w ≦ 25.0 mol% 0 0.0 mol% ≦ x ≦ 50.0 mol% 0.0 mol% <y ≦ 30.0 mol% 0.0 mol% <z ≦ 80.0 mol% 0.0 <u <1.0 A dielectric porcelain composition for microwaves, which is characterized in that