JPH0952762A - Aluminous ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the temp. coefficient of resonance frequency while low dielectric loss is kept, in a ceramic consisting essentially of Al2 O3 . SOLUTION: This aluminous ceramic composition consists essentially of Al2 O3 , TiO2 and Nb2 O5 and the composition ratio of each component in the mol ratio is prepared so as to be in the range surrounded with segments of lines A-B-C-D-A in an Al2 O3 -TiO2 -Nb2 O5 three component composition diagram shown in the figure, and by allowing at least α-Al2 O3 and TiO2 to deposit as a crystal phase, excellent dielectric characteristics <=1×10<-3> dielectric loss in 8GHz measured frequency, and <=30ppm |τf|absolute value of temp. coefficient of resonance frequency at 25-85 deg.C, are obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dielectric resonator, a microwave waveguide, a microwave capacitor, and a microwave I.
The present invention relates to an alumina-based porcelain composition which is suitably used for high frequencies in the field of telecommunications such as C substrates, IC packages, dielectric antennas and the field of nuclear fusion related facilities such as microwave transmission windows.

[0002]

2. Description of the Related Art In recent years, with the rapid development of communication networks, frequencies used for communication have expanded, and at the same time, have reached high frequencies such as microwaves and millimeter waves. On the other hand, dielectric porcelain has been applied to dielectric resonators, integrated circuit boards, dielectric antennas, impedance matching of various high-frequency circuits, etc. in addition to capacitors, etc. What is adaptable is desired. For example, it is necessary for frequency stabilization of filters, guns, or FET microwave oscillators, and its demand is increasing.

The size of the microwave circuit element is based on the wavelength of the electromagnetic wave, and when the electromagnetic wave propagates in the microwave three-dimensional circuit using the dielectric, the wavelength is λ _{0 in} vacuum. , Let ε be the relative permittivity, then λ ₀ / ε ^1/2 .

On the other hand, alumina, which is most commonly used as ceramics, has a low dielectric loss of about 10 and a dielectric loss of 10 ⁻⁶ (8 GHz) in the case of sapphire single crystal, but it is very expensive. On the other hand, an alumina-based sintered body obtained by adding various sintering aids to alumina powder has high mechanical strength and is low in cost, so that it can be greatly used in the telecommunications field as described above. Is expected.

[0005]

However, since the temperature coefficient of resonance frequency (hereinafter referred to as τf) is large at about −55 ppm / ° C., the porcelain mainly containing alumina is extremely limited in its intended use. There was a problem.
As a method of controlling τf, it is possible to adjust by appropriately combining τf with a positive component and a negative component, but τf can be controlled while maintaining low loss at high frequencies such as increased dielectric loss. It was difficult to make it smaller. Further, although the single crystal such as sapphire (Al ₂ O ₃ ) has a very low dielectric loss, it has a problem that it is very high as compared with the alumina sintered body.

Therefore, there has been a demand for an inexpensive porcelain having a low dielectric loss comparable to that of sapphire and having a small τf.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention firstly assume that in order to reduce the absolute value of τf of alumina, it is necessary to add a compound having a temperature coefficient having an opposite sign to that of alumina. As a result of various investigations into the present invention, as a result of adding TiO ₂ and Nb ₂ O ₅ in combination within a specific range as an additive to alumina, it was found that low dielectric loss and the absolute value of τf can be reduced, and the present invention I arrived.

That is, the alumina-based ceramic composition of the present invention is
Al ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ as main components,
The composition ratio according to the molar ratio of each component is Al ₂ O ₃ -T in FIG.
iO ₂ —Nb ₂ O ₅ 3 composition diagram Is within the range surrounded by the line segment A-B-C-D-A, and further contains at least α-Al ₂ O ₃ and TiO ₂ as a crystal phase. , The dielectric loss at a measurement frequency of 8 GHz is 1 × 10 ⁻³ or less,
Absolute value of temperature coefficient at resonance frequency of 25 to 85 ° C |
τf | has an excellent dielectric property of 30 ppm or less.

[0009]

According to the present invention, TiO ₂ is added to Al ₂ O ₃ .
_The temperature coefficient τf can be shifted to the positive side by TiO ₂ produced by the combined addition of ₂ and Nb ₂ O ₅ . As a result, the dielectric loss is 1 × 1 at the measurement frequency of 8 GHz.
The absolute value of τf is 30 ppm / ° C while maintaining 0 ^-3 or less.
It becomes possible to control as follows, and thus it has become possible to use it in a wide range in the telecommunication field in the high frequency region.

When the amount of Al ₂ O ₃ exceeds the above composition range, τf becomes negatively large. On the contrary, when the Al ₂ O ₃ amount is less than the above composition range, τf becomes positively large or the dielectric loss increases. It exceeds 1 × 10 ^-3 . Further, even if the alumina content is within the range, if the ratio of Nb ₂ O ₅ and TiO ₂ deviates from the above composition range, Al ₂ TiO ₅ or AlNbO ₄ will be excessively precipitated and the dielectric loss will be 1 × 1.
Either it exceeds 0 ^-3 or the absolute value of the temperature coefficient of the resonance frequency exceeds 30 ppm / ° C.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The alumina-based porcelain composition of the present invention uses Al ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ , or a salt such as a carbonate or a nitrate capable of forming the oxide by firing. After being weighed and mixed so that the composition range shown in FIG. 1 is obtained, this is mixed with a desired molding means, for example, a sheet molding method such as a doctor blade method, a die pressing method, a cold isostatic pressing method, an extrusion molding method, a rolling method It is formed into an arbitrary shape by a method or the like. Then, the compact can be densified to a relative density of 98% or more by firing the compact at a temperature of 1400 to 1700 ° C. in an oxidizing atmosphere such as air.

In the porcelain composition of the present invention, in addition to the components of Al ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ , elements such as Mg, Si, Fe, Ca, Na and Ga are unavoidable. There are cases where impurities or impurities are mixed in during the manufacturing process, but these components are contained in an amount of 0.
If it is 2% by weight or less, the effect of the present invention is not particularly affected.

[0013]

EXAMPLES Al ₂ O ₃ powder having a purity of 99.9%, TiO ₂
The powder and the Nb ₂ O ₅ powder were weighed so as to have the compositions shown in Tables 1 and 2, and the mixed powder was mixed with alumina balls having a purity of 99.9% and isopropyl alcohol (IPA).
The mixture was put into a 00 ml polypot and mixed in a rotary mill for 24 hours. The mixed slurry is dried in the air at 80 ° C.
An evaluation powder was obtained through 0 mesh.

This powder was pressed with a die press at 1000 kg /
It was molded into a diameter of 20 mm and a thickness of 10 mm at cm ² , and then cold isostatic pressing (CIP) at 3000 kg / cm ² . Then, the molded body was held in the atmosphere at 1550 ° C. for 2 hours and fired.

The obtained sintered body had a diameter of 15 mm and a thickness of 7.
It was processed and polished to 5 mm. Then, the dielectric constant (εr) and the dielectric loss (tan) are measured by the measurement at the measurement frequency of 8 GHz.
δ) and the temperature coefficient (τf) of the resonance frequency at 25 to 85 ° C were measured. Also, the wavelength λ = 1.5418Å
The crystal phase of the sample was identified by X-ray diffraction using CuKα ray. The results of these measurements are shown in Tables 1 and 2.

[0016]

[Table 1]

[0017]

[Table 2]

[0018] Table 1, according to the results of Table 2, the Al ₂ O ₃ content is too large sample Nanba15,20, the absolute value of τf exceed the 30ppm / ℃, Al ₂ O ₃ content of the Samples Nos. 11 to 13 and 21, which were smaller than the composition range, also had an absolute value of τf exceeding 30 ppm / ° C. Also, TiO
Sample N in which the ratio of ₂ and Nb ₂ O ₅ is outside the scope of the present invention
In o.10, 13, 14, and 15, all of the absolute values of τf exceeded 30 ppm / ° C, or the dielectric loss exceeded 1 × 10 ^-3 .

On the other hand, all the samples in the composition range of the present invention have α-Al ₂ O ₃ and Ti as crystal phases.
O ₂ is deposited, dielectric constant 9 to 20, measurement frequency 8G
The dielectric loss at Hz is 1 × 10 ⁻³ or less, and the absolute value of the temperature coefficient at resonant frequency 25 to 85 ° C. | τf | is 30.
It exhibited excellent characteristics of not more than ppm / ° C.

Among these, line segment EF-G in FIG.
In the area surrounded by −HE, the dielectric constant is 9 to 20, the dielectric loss at the measurement frequency of 8 GHz is 1 × 10 ⁻³ or less, and the absolute value of the temperature coefficient at the resonance frequency of 25 to 85 ° C. | τ
The f | exhibited excellent characteristics of 10 ppm / ° C. or less.

[0021]

As described in detail above, the alumina-based ceramic composition of the present invention is obtained by blending Al ₂ O ₃ with TiO ₂ and Nb ₂ O ₅ so as to satisfy a predetermined relationship. It is possible to reduce the absolute value of the temperature coefficient of the resonance frequency while maintaining low dielectric loss, which allows dielectric resonators, microwave waveguides, microwave capacitors, microwaves that are suitable for microwaves and millimeter waves. IC board,
It has become possible to apply to IC packages, dielectric antennas, etc.

[Brief description of drawings]

FIG. 1 is an alumina porcelain composition of the present invention containing Al ₂ O ₃ ,
FIG. 3 is a three-component composition diagram showing the contents of TiO ₂ and Nb ₂ O ₅ .

Claims (2)

[Claims] 1. A composition containing Al ₂ O ₃ , TiO ₂ and Nb ₂ O ₅ as main components and having a composition ratio based on a molar ratio of each component is A in FIG.
1 ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ 3 Alumina-based porcelain composition characterized by being in a range surrounded by line segment ABCDA in the three-component composition diagram. 2. A crystalline phase of at least α-Al ₂ O _3
2. The alumina-based porcelain composition according to claim 1, wherein the dielectric loss at a measurement frequency of 8 GHz is 1 × 10 ⁻³ or less, and the absolute value of the temperature coefficient at resonance frequency of 25 to 85 ° C. | τf | is 30 ppm or less. .