JPH06102572B2 - High frequency dielectric ceramic composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention is applied in the micro frequency range, and exhibits a high Q value and a dielectric constant in this range, and has a stable temperature characteristic. It relates to a porcelain composition.

<Prior Art> With the development of communication networks in recent years, the frequency range used has expanded to reach microwaves. In connection with this, the dielectric ceramics are applied to impedance matching of dielectric resonators, microwave integrated circuit boards, and various microwave circuits in the microwave frequency range. Especially recently filter or gun or FE
A large number of T-microwave oscillators are required for frequency stabilization, and the demand for them is increasing.

By the way, the dielectric loss tends to increase as the frequency used increases. Therefore, a dielectric ceramic having a large Q value in the micro frequency range is desired.

<Problems to be solved by the invention> ZrO ₂ is used as a conventional general high-frequency dielectric ceramic material.
-SnO ₂ -TiO ₂ based ceramic, there is a BaO-TiO ₂ based ceramic, and porcelain and the like obtained by substituting a part by another element.

However, these materials have various problems such as a small Q value, a small relative dielectric constant, and a failure to obtain a desired temperature coefficient.

An object of the present invention is to provide a high frequency dielectric ceramic composition having a high Q value applicable to the microwave region, a high dielectric constant that can be practically used, and stable temperature characteristics. .

<Means for Solving Problems> As a result of various studies on porcelain compositions satisfying the above-mentioned demand, the present inventor has barium oxide, neodymium oxide, and titanium oxide as main components, and a composition formula of the main components. when the expressed and _{xBaO-yNd 2 O 3 -zTiO 2} , x, y, z is 8.5 ≦ x ≦ 20 (mol%) 5 ≦ y ≦ 23 (mol%) 62 ≦ z ≦ 85 (mol%) (where X + y + z = 100%), and the upper limit is 15% by weight and the lower limit is 5.5% by weight with respect to the total amount of yttrium oxide and the main component.
Range (however, when x + y + z = 1 mol, Y ₂
It has been found that a composition containing O ₃ added in an amount of 0.0003 mol to 0.03 mol) is contained in an excellent dielectric ceramic composition for high frequencies.

<Example> The present invention was carried out as follows.

・ Sample: BaCO ₃ , Nd ₂ O ₃ , Y ₂ O ₃ and TiO ₂ having a purity of 99.9% are used as starting materials.
Weigh and mix predetermined amounts according to each composition, dry-prime this with a mixer and perform mixing, then at 1100 ° C in air.
It was calcined at the temperature of 4 hours. Further, an appropriate amount of an organic binder and pure water are added to the calcined product, the mixture is wet pulverized in an alumina ball mill, then granulated by spray drying, and the granulated raw material is shaped into a predetermined disc shape, and the shaped body is Atmosphere 13
It was baked at a temperature of 00 ° C to 1450 ° C for 30 minutes to 4 hours, and both end faces were polished to a disk shape of about 16 mmφ x 10 mmt to obtain a dielectric sample.

Then, for each sample, no-load Q (= 1 / tan δ), relative permittivity εr, resonance frequency temperature coefficient τ by the dielectric cylinder resonator method.
f and dielectric loss tan δ were measured.

The resonant frequency in these measurements is 2-3 GHz. Further, the temperature coefficient τf was obtained from the value in the temperature range of −40 ° C. to 80 ° C. based on the following equation.

τf = −1 / 2τ−α where τ; rate of change in permittivity with temperature α; coefficient of linear expansion of porcelain sample These results are shown in the following table.

In the following table, sample numbers marked with * indicate those outside the scope of the present invention.

-Results As is clear from the above table, the dielectric ceramic material of the present invention showed a high relative permittivity εr in the microwave region. It was also confirmed that the dielectric loss and the tan δ were in the order of 10 ⁻⁴ , which was lower than the conventional substrate material of Al ₂ O ₃ by the order of 10 ⁻³ by one digit or more, which was excellent.

It was also shown that the resonance frequency temperature coefficient τf can be put to practical use.

<Reason for limiting the present invention> Next, the reason for limiting the composition range of the present invention will be described.

B) Regarding the content x of barium oxide (BaO), the content x
Is less than 8.5 mol%, the dielectric constant ε is
Is reduced. On the other hand, when it exceeds 20% by weight, the dielectric loss tan δ becomes large as in Sample 34.

(B) Regarding the content y of neodymium oxide (Nd ₂ O ₃ ) When the content y is lower than 5 mol%, the resonance frequency temperature coefficient τf has a large positive value as in Sample 3. When it exceeds 23 mol%, the induced loss tan δ becomes large as in Samples 1 and 2.

C) Content z of titanium oxide (TiO ₂ ) When the content z is lower than 62 mol%, the dielectric loss tan δ becomes large as in Sample 34. If it exceeds 85 mol%,
Like the samples 3 and 4, the resonance frequency temperature coefficient τf has a large positive value.

D) Regarding the added amount w of yttrium oxide (Y ₂ O ₃ ) As the added amount w is increased, the temperature characteristics can be stabilized without significantly decreasing the relative permittivity εr. 15 for the total amount of main components
If it is added in excess of wt%, the sintering becomes unstable, the unloaded Q value decreases, and the resonance frequency temperature coefficient τf takes a large negative value. Therefore, the above ranges are excluded from the scope of the present invention.

The samples 32, 33, 35, and 36 in the table had extremely large unloaded Q, and it was impossible to measure the relative permittivity εr and the resonance frequency temperature coefficient τf.

<Effects of the Invention> The dielectric ceramic composition of the present invention has a high Q value (low dielectric loss tan δ), a high dielectric constant ε, and a resonance frequency temperature, as shown in the above experimental examples. The value of the coefficient τf can also be suitable for practical use.

Therefore, the present invention has an excellent effect that is optimal as a dielectric ceramic material applied to the micro frequency range.

Claims (1)

[Claims] 1. When barium oxide, neodymium oxide and titanium oxide are main components and the composition formula of the main components is expressed as xBaO-yNd ₂ O ₃ -zTiO ₂ , x, y, z are 8.5 ≦ x ≦. 20 (mol%) 5 ≦ y ≦ 23 (mol%) 62 ≦ z ≦ 85 (mol%) (where x + y + z = 100%), and yttrium oxide (Y ₂ O ₃ ) is used as the main component. The upper limit is 15% by weight and the lower limit is 5.
Range of 5% by weight (excluding the range where Y ₂ O ₃ is 0.0003 to 0.03 mol when x + y + z = 1 mol)
A dielectric ceramic composition for high frequencies, characterized in that