JP2516620B2 - Dielectric porcelain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a novel dielectric ceramic suitable for high frequency,
In particular, the present invention relates to a dielectric porcelain having a negative temperature coefficient of the resonance frequency when the resonator is configured and useful for compensating the temperature coefficient.

[Conventional technology]

In recent years, as a dielectric ceramic used in a high frequency region such as a microwave and a millimeter wave, a dielectric ceramic having an unloaded Q and a high relative dielectric constant has been developed.

Among these high-frequency dielectric porcelains, the temperature coefficient of the resonance frequency when the resonator is constructed is too positively biased despite the fact that the no-load Q and the relative permittivity are excellent. Some of them are difficult to use for applications such as stabilization, and examples thereof include TiO ₂ and SrO—TiO ₂ porcelain.

As a method for improving such a dielectric porcelain in which the temperature coefficient of the resonance frequency is too positively biased, such a dielectric porcelain is compounded with a dielectric porcelain having a large negative temperature coefficient, and the temperature coefficient is ± 10 ppm / Attempts have been made to make it practical by controlling it within the range of ° C. As a dielectric porcelain with a large negative negative temperature coefficient of the resonance frequency used for this composite, for example,
MgTiO ₃ , La ₂ Ti ₂ O ₇ , Ca ₂ Nb ₂ O _{7 and the} like are known.

[Problems to be solved by the invention]

However, although the dielectric ceramics having a large negative temperature coefficient of the resonance frequency can compensate the temperature coefficient by compounding, since the unloaded Q is small, the unloaded Q of the obtained composite dielectric is lowered. There was a problem.

Therefore, an object of the present invention is to provide a novel dielectric porcelain having a negative temperature coefficient of resonance frequency and excellent characteristics such as no-load Q and relative permittivity, which is suitable for compensation of the temperature coefficient of resonance frequency. It is in.

[Means for solving problems]

In order to solve the above-mentioned conventional problems, the present invention provides Ln ₂ O ₃ (where Ln represents at least one rare earth element selected from La, Sm, Eu, Gd, Tb and Dy) and Al
Disclosed is a dielectric porcelain substantially composed of ₂ O ₃ and having a perovskite structure.

Here, the dielectric ceramics of the present invention having “substantially have a perovskite structure” means that a phase having a perovskite type crystal structure is observed in X-ray diffraction, and no other phase is observed at all. Means that.

In the present invention, as the rare earth element Ln, La, S
One of m, Eu, Gd, Tb and Dy may be used alone or in combination of two or more, and the ratio of Ln ₂ O ₃ and Al ₂ O ₃ is generally Ln ₂ O ₃ 60
-80 wt% and Al ₂ O ₃ 20-40 wt% are preferable, and Ln ₂ O ₃ 75-80 wt% and Al ₂ O ₃ 20-25 wt% are more preferable. When Ln ₂ O ₃ is less than 60% by weight and Al ₂ O ₃ exceeds 40% by weight, the relative permittivity of the porcelain decreases and it becomes difficult to put it into practical use. Also, when Ln ₂ O ₃ exceeds 80% by weight, Al ₂ O ₃ exceeds 80% by weight. This is because if O ₃ is less than 20% by weight, the sinter density of the porcelain, and thus the mechanical strength, decreases and the unloaded Q also decreases.

When using a single type of element as a rare earth element,
The preferable ratio of each rare earth element to Al ₂ O ₃ is as shown in Table 1, and in these cases, a particularly preferable ratio is Ln ₂ O ₃ 75 in any rare earth element.
80% by weight, in the range of Al ₂ O ₃ 20-25% by weight.

The method for producing the dielectric porcelain of the present invention is not particularly limited, and it can be produced by an ordinary method. For example, a rare earth oxide is used as a raw material of a rare earth element, aluminum oxide is selected as a raw material of aluminum, each is weighed at a required ratio, mixed, and calcined at about 1000 to 1200 ° C. It can be produced by firing at a temperature of ~ 1650 ° C.

The dielectric porcelain of the present invention has a negative temperature coefficient of the resonance frequency when the resonator is formed, and the unloaded Q, the relative dielectric constant and the like are sufficient for high frequencies. Therefore, the temperature coefficient of the resonance frequency is too positively biased even though the no-load Q and the relative permittivity are good. Suitable for compensation within the range of.

Examples of the compounding method include, for example, a method of joining a plate-shaped dielectric ceramic with a plate-shaped dielectric ceramic to be compensated for according to the present invention, and a method in which both dielectric ceramics are crushed and mixed as a powder, and then integrated by firing. It is possible to use a method of forming a porcelain composed of small phases of both dielectric porcelains. That is, the case where the porcelain of the invention is combined with another porcelain in the state of fine particles like the latter is also included as one aspect of the present invention.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Five types of dielectric porcelain (Sample Nos. 1 to 5), which consisted of La ₂ O ₃ and Al ₂ O _3, and whose compositions are as shown in Table 2, were manufactured as follows.

Lanthanum oxide (La ₂ O ₃ ) with a purity of 99.9% or more as a raw material
And aluminum oxide (Al ₂ O ₃ ) are weighed in a predetermined ratio,
Zirconia balls were used to pulverize and mix in pure water in a pot for 16 hours in a ball mill. This mixture was taken out of the pot and dried at 150 ° C for 5 hours, then 1000-1200 ° C
And calcined. After calcination, crush and sizing, then diameter 10mm,
A formed body having a height of 5 mm was fired at 1500 to 1650 ° C for 1 to 3 hours. The relative permittivity (ε _r ) of the obtained porcelain and 10 GHz
The unloaded Q (Qu) in the above was measured by the dielectric resonator method. Furthermore, the temperature was changed from + 60 ° C. to 0 ° C., the resonance frequency of the resonator was measured, and the temperature coefficient (τ _f ) was calculated. The results obtained are shown in Table 2.

Examples 2 to 6 In Examples 2 to 6, La was used as the rare earth element oxide.
Instead of ₂ O _3, respectively, Sm ₂ O ₃ is 99.9% or higher,
Several kinds of dielectric porcelain were manufactured in the same manner as in Example 1 except that Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ and Dy ₂ O ₃ were used. Compositions of porcelains manufactured in Examples 2 to 6, temperature coefficient (τ _f ) of resonance frequency measured in the same manner as in Example, unloaded Q (Q
u) and relative permittivity (ε _r ) are shown in Tables 3 to 7, respectively.

Further, when the porcelains of Sample No. 3 of Example 1 and Sample No. 4 of Example 4 were crushed and the obtained powder was subjected to X-ray diffraction, a phase having a perovskite type crystal structure was observed, and other No or little phase was observed.

Example 7 SrO-Ti having a relative permittivity of 38, no load Q12000 (12 GHz), and a temperature coefficient of resonance frequency of a resonator of +150 ppm / ° C.
An attempt was made to compensate for the temperature coefficient of the O ₂ -based dielectric ceramic (composition: SrO / TiO ₂ = 2/1 (weight)) by compounding the dielectric ceramic of sample No. 5 of Example 4 described above.

That is, the SrO-TiO ₂ system dielectric ceramic has a diameter of 7.5 mm and a thickness of
The dielectric ceramics of Example 4 and Sample No. 5 were processed into a disk having a diameter of 7.5 mm and a thickness of 2.7 mm on a disk having a thickness of 1.0 mm, and one surface of the both was bonded to form a disk resonator. . The composite dielectric resonator thus obtained was measured in the same manner as in Example 1. As a result, the relative dielectric constant was 23, the unloaded Q8950 and the temperature coefficient of the resonance frequency were +9.2 ppm / ° C. (12 GHz).

〔The invention's effect〕

As is clear from the examples, the dielectric ceramics of the present invention have a negative temperature coefficient of the resonance frequency in the microwave region, and are excellent in both the relative permittivity and the no-load Q. Therefore, it is suitable to improve the temperature coefficient of the dielectric porcelain that cannot be put to practical use by compounding it because the temperature coefficient of the resonance frequency is too positively biased while the relative permittivity and the no-load Q are good. , Enhances the practicality of these materials.

Claims (1)

(57) [Claims] 1. Ln ₂ O ₃ (where Ln is La, Sm, Eu, Gd, T
A dielectric ceramic having a substantially perovskite structure composed of Al ₂ O ₃ and at least one rare earth element selected from b and Dy).