JP4655254B2 - Dielectric porcelain composition for microwave - Google Patents

Description

【００１９】
【発明の効果】
この発明による誘電体磁器組成物は、組成式（Ｌｉ¹⁺ _1/2・Ｒ³⁺ _1/2）・ＴｉＯ₂において、Ｒ³⁺の一部として特定量のＢｉ³⁺を含有することにより、前記誘電体磁器組成物より、より大きい誘電率εが得られ、且つ共振周波数の温度係数τｆが大になり、さらに、Ｌｉ¹⁺の一部をＮａ¹⁺にて置換することにより、共振周波数の温度係数τｆを０に近づける等、τｆを調整できる。
【００２０】
この発明による誘電体磁器組成物は、実施例に明らかなように誘電率εが大きく、共振周波数の温度係数τｆが０に近く、大きいＱ値が得られており、数ＧＨｚ帯のマイクロ波を利用した衛星通信放送または移動体識別装置などの送受信機において用いられる共振器、フィルター、コンデンサーの誘電体に最適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric ceramic composition for microwaves used for a resonator material or a capacitor material used in a microwave region of several GHz band.
[0002]
[Prior art]
In recent years, dielectrics have been used for resonators, filters, and capacitors used in transceivers such as satellite communication broadcasts using several GHz band microwaves or mobile object identification devices.
[0003]
Conventionally, as this type of dielectric ceramic material, for example, a BaO—TiO ₂ —Nd ₂ O ₃ —Bi ₂ O ₃ composition has been proposed (Japanese Patent Laid-Open No. 61-8806). The composition has a dielectric constant ε of about 70 to 110. When a dielectric resonator or a capacitor is formed, the larger the dielectric constant ε is, the smaller the resonator can be dimensioned. A material having a rate ε is desired.
[0004]
Conventionally, materials having a large dielectric constant ε include, for example, SrTiO ₃ and CaTiO _3. The dielectric constant ε is as large as 300 and 180, but the temperature coefficient τf of the resonance frequency is +1700 ppm / ° C. and +800 ppm / Cannot be used because it is very large at ℃.
[0005]
Therefore, as a method of lowering the temperature coefficient τf of the dielectric ceramic composition, there is a method of combining materials having a dielectric constant ε as large as possible and a temperature coefficient τf having a negative value. By the combination, a ceramic composition having a large dielectric constant ε and a small temperature coefficient τf of the resonance frequency can be obtained.
[0006]
[Problems to be solved by the invention]
For example, JP-A-5-211009 discloses a composition formula (A ¹⁺ _1/2 · B ³⁺ _1/2 ) TiO ₃ as a material having a large dielectric constant ε and a negative temperature coefficient τf. A ¹⁺ is Li ¹⁺ , B ³⁺ is Nd ³⁺ , Sm ³⁺ , Co ^3+, or Pr ³⁺ . It has been proposed that a porcelain composition having a temperature coefficient τf close to 0 can be obtained.
[0007]
Today, however, the demand for miniaturization of portable electronic terminal devices is severe, and it is strongly required to use materials having a higher dielectric constant ε for the dielectrics of resonators, filters, and capacitors used in such devices. It has been.
[0008]
In view of the characteristics required of a dielectric ceramic composition for microwaves, the present invention includes adding a ceramic composition having a large temperature coefficient τf of the resonance frequency to the negative side and adding a large ceramic composition to the positive side of τf. An object is to obtain a dielectric ceramic composition having a large dielectric constant ε, a temperature coefficient τf of resonance frequency close to 0, and a large Q value.
[0009]
[Means for Solving the Problems]
We its composition expressed by _{^{(Li 1+ 1/2 · R 3+ 1/2}} ) · TiO 3, R 3+ is ^{La 3+, Nd 3+, Sm 3} + 1 kind or of In a dielectric ceramic composition containing two or more kinds, by containing a specific amount of Bi ³⁺ as a part of R ³⁺ , a larger dielectric constant ε than that of the dielectric ceramic composition can be obtained, and resonance can be achieved. It has been found that the frequency temperature coefficient τf can be suppressed from becoming large.
[0010]
In addition, the inventors can adjust τf such that the temperature coefficient τf of the porcelain composition is close to 0 by replacing a part of Li ^{1+ in} the composition formula with Na ¹⁺ . Knowing that it can be done, the present invention has been completed.
[0011]
In the present invention, the composition formula is represented by {(1-u) Li 1 ⁺ · uNa ¹⁺ } _1/2 · {xBi ^{3 +} · (1-x) R ³⁺ } _1/2 · TiO ₃ , where R ³⁺ is La It is a dielectric ceramic composition for microwaves, including one or more of ³⁺ , Nd ³⁺ and Sm ³⁺ , wherein u and x satisfy the following values.
0.03 <u <0.8
0 <x <0.7
[0012]
DETAILED DESCRIPTION OF THE INVENTION
This invention is represented by a compositional formula of _{^{(Li 1+ 1/2 · R 3+ 1/2}} ) · TiO 3, R 3+ is ^{La 3+, Nd 3+, Sm 3} + 1 kind of or two A dielectric ceramic composition containing at least seeds contains Bi ³⁺ as a part of R ³⁺ .
[0013]
Such Bi ³⁺ content has the effect of improving the dielectric constant ε. However, when Bi ³⁺ exceeds 0.7, Bi ₂ O ₃ as Bi ³⁺ has a low melting point, and therefore the porcelain composition is used as a slab or the like during firing. This is not preferred because it may react with the floor powder and melt.
[0014]
In the present invention, the reason for limiting the amount of Na ¹⁺ substituting a part of Li ¹⁺ to 0.03 to 0.8 is that τf is greatly negative if it is less than 0.03, and 0.8 If it exceeds, τf becomes a large positive value, which is not preferable.
[0015]
【Example】
In the compositional formula {(1-u) Li 1 ⁺ · uNa ¹⁺ } _1/2 · {xBi ^{3 +} · (1-x) R ³⁺ } _1/2 · TiO ₃ , Li ¹⁺ and Na ¹⁺ with different blending ratios and blending ratios ^La 3+ as different ^{Bi 3+} and _{^{R 3+, Nd 3+, La 2}} O 3 as raw materials as porcelain composition consisting ^{Sm 3+} is _obtained, NdO _{3, Sm} 2 _O 3 and _{Li 2 CO 3, Na 2 O} , Bi ₂ O ₃ and TiO ₃ high-purity powders were blended so as to have a predetermined molar fraction.
[0016]
Then, after mixing with a ball mill for 5 to 20 hours, after calcining at 700 ° C. to 1000 ° C. for 1 hour, pulverizing again for 2 to 50 hours, adding an organic binder to the pulverized powder, and granulating and classifying The disk was formed into a disk shape having a diameter of 10 mm and a thickness of 6 mm at a pressure of ^{2 to 3} T / cm ² . The molded body was sintered at 1200 ° C. to 1400 ° C. for 1 to 5 hours, and then polished on both sides so that the thickness of the sintered body was ½ of the diameter to prepare a measurement sample.
[0017]
The measurement sample was measured for dielectric constant ε, Q value, and temperature coefficient τf of resonance frequency at a measurement frequency of 3 GHz using the Hack & Coleman method. Table different mixing ratio of Li ¹⁺ and Na ¹⁺ to 1, Bi ³⁺ and La ³⁺ as R ^3+, Nd ^3+, the dielectric constant of the different ceramic composition of Sm ^{3 +} compounding ratio of epsilon, Q value And the temperature coefficient τf of the resonance frequency.
[0018]
[Table 1]

[0019]
【The invention's effect】
The dielectric ceramic composition according to the present invention contains a specific amount of Bi ³⁺ as a part of R ^{3+ in} the composition formula (Li ¹⁺ _1/2 · R ³⁺ _1/2 ) · TiO ₂ . A dielectric constant ε larger than that of the dielectric ceramic composition is obtained, and the temperature coefficient τf of the resonance frequency is increased, and further, a part of Li ¹⁺ is replaced with Na ¹⁺ to resonate. The τf can be adjusted, for example, by bringing the temperature coefficient τf of the frequency closer to zero.
[0020]
The dielectric ceramic composition according to the present invention has a large dielectric constant ε, a temperature coefficient τf of the resonance frequency close to 0, and a large Q value, as is apparent from the examples. It is most suitable as a dielectric for resonators, filters and capacitors used in transceivers such as satellite communication broadcasts and mobile object identification devices.

Claims (1)

The composition formula is represented by {(1-u) Li 1 ⁺ · uNa ¹⁺ } _1/2 · {xBi ^{3 +} · (1-x) R ³⁺ } _1/2 · TiO ₃ , where R ³⁺ is La ³⁺ , Nd ³⁺ , And one or more of Sm ³⁺ , and u and x satisfy the following values.
0.03 <u <0.8
0 <x <0.7