JPH0597511A - Porcelain composition - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a magnetic composition having a high dielectric constant, a low loss, a temperature coefficient of the dielectric constant which can be arbitrarily controlled, and which can be used as a dielectric of an electronic component in a high frequency band in a stable manner. . [Structure] xMgO + yCaO + zTiO ₂ + uCr ₂ O ₃ , where x, y, z, and u are 25 ≦ x ≦ 80, respectively.
(mol%), 1 ≦ y ≦ 5 (mol%), 10 ≦ z ≦ 70 (mol%), 0.5
A porcelain composition having a composition satisfying <u ≦ 10 (mol%).

Description

Detailed Description of the Invention

[0001]

The present invention relates to MgO-CaO-TiO ₂
-Cr ₂ O ₃ -based porcelain composition has a relatively large relative permittivity ε _{r and a} dielectric loss tangent tan δ in a high frequency band.
Is small and the temperature coefficient of the dielectric constant is -50 to 50 depending on the composition.
The present invention relates to a porcelain composition that can be controlled in the range of ppm / ° C. and that operates stably in a high frequency band.

[0002]

2. Description of the Related Art In recent years, frequency resonators in the high frequency band represented by microwaves (hereinafter simply referred to as "resonators") are used in high frequency components such as antenna substrates for microstrips, and have a relatively high dielectric constant and low loss. The dielectric porcelain material is used positively to stabilize and downsize the equipment. Conventionally, as these dielectric ceramic materials, MgO-CaO-TiO ₂
The three-component porcelain composition of the system and the addition of other additives to this ternary system have been investigated.

[0003]

[Problems to be Solved by the Invention] However, MgO
-CaO-TiO ₂ based ceramic has a narrow composition range which can both reduce the temperature coefficient and dielectric loss tangent tanδ of the dielectric constant, changing the composition ratio and the relative dielectric constant epsilon _r, because the temperature coefficient changes at the same time, for example, a dielectric the relative dielectric constant epsilon _r of the composition, such as the temperature coefficient of the dielectric constant epsilon _r dielectric loss tangent tanδ of the porcelain with a minimum is obtained a value of ± 0 ppm / ° C. vicinity is about 15, more large specific dielectric constant of It was difficult to obtain ε _r .

On the other hand, in order to miniaturize high frequency components such as a resonator, a material having a large relative permittivity ε _r is required. Therefore, Mg ₂ O ₃ Ca ₂ O ₃ and Al ₂ O ₃ are added to the MgO—CaO—TiO ₂ system. Has been studied. La ₂ O as an additive
_{When 3} is added, composition change occurs due to reaction with CO ₂ in the atmosphere, and it was difficult to control the composition during mass production and industrialization. Further, when Al ₂ O ₃ is added, there is a drawback that the sintering temperature becomes a high temperature of about 1500 ° C. and the cost becomes high.

In view of the above conventional problems, the present invention has a large relative permittivity ε _r , a small dielectric loss tangent tan δ in a high frequency band, and a temperature coefficient of the permittivity can be controlled by the composition, and
It is intended to provide a stable porcelain composition.

[0006]

Means for Solving the Problems The present invention, x when expressed the composition range of component as _{xMgO · yCaO · zTiO 2 · uCr} 2 O 3, y, z, u , respectively, 25 ≦ x ≦ 80 mol
%, 1 ≦ y ≦ 5 mol%, 10 ≦ z ≦ 70 mol%, 0 <u ≦ 10mo
It is characterized in that it is in a range satisfying l%.

[0007]

[Operation] MgO constituting the porcelain composition exceeds 80 mol%,
When CaO exceeds 5 mol% and TiO ₂ exceeds 70 mol%,
The temperature coefficient of the permittivity rapidly increases to a negative value, the characteristics change due to compositional changes, and the MgO content is less than 25 mol%, C
If aO is less than 1 mol% and TiO ₂ is less than 10 mol%, the ceramic material tends to crack due to shrinkage after sintering, which is difficult to put into practical use. Furthermore, when Cr ₂ O ₃ exceeds 10 mol%, the temperature coefficient of the dielectric constant sharply increases to a negative value, the characteristics change largely due to compositional variations, and the dielectric loss tangent tan δ deteriorates. Therefore, according to the present invention, by adopting a composition excluding the above range, the relative permittivity ε _r is relatively large, the dielectric loss tangent tan δ in the high frequency band is small, the temperature coefficient of the permittivity can be controlled by the composition, and the stability is stable. A porcelain composition that is easy to obtain is obtained.

[0008]

EXAMPLES Examples will be described below.

First, the raw material powder contains Mg having a purity of 99.5% or more.
Each powder of O, CaO, TiO ₂ , and Cr ₂ O ₃ was weighed so as to have a predetermined composition shown in Table 1 and wet-mixed with pure water by a ball mill. Then, the mixture was dried and then calcined in air at a temperature of 1000 ° C. for 2 hours.

[0010]

[Table 1]

The above calcined product was again wet-ground with a ball mill to form an average particle size of 1 to 2 μm, and then dehydrated and dried.

About 7 wt% of a 10% concentration polyvinyl alcohol solution was added to this powder to form a granule, and the granulated powder was sieved through a 60-mesh sieve to obtain 10 particles using a die and a hydraulic press.
Molded into a shape with a molding pressure of 00 kg / cm ² of 15 mm in diameter and 7 mm in height.

The molded body was held in an oxidizing atmosphere at a temperature in the range of 1200 to 1400 ° C. for 2 hours and fired depending on its composition.

The porcelain obtained as described above was processed into predetermined dimensions, and the relative permittivity ε _r and the dielectric loss tangent tan δ at 25 ° C. and 8 GHz were determined.

The temperature coefficient of relative permittivity (T _k ppm / ° C.)
Was calculated as a change in resonance frequency (T _f ppm / ° C.) in the temperature range of −50 ° C. to + 120 ° C., and T _k was calculated from the equation (1).

[0016]

[Equation 1]

However, in the equation (1), T _f is the temperature coefficient of the resonance frequency, T _k is the temperature coefficient of the dielectric constant, and α is the thermal expansion coefficient of the porcelain.

The measuring method used at this time was the dielectric cylinder transmission method. That is, the cylindrical sample obtained as described above is sandwiched between two upper and lower metal plates to form a resonator, and the relative permittivity ε _r , the dielectric loss tangent tan δ and the resonance are calculated from the TE ₀₁₁ mode. The temperature coefficient of frequency T _f was determined.

The results obtained as described above are shown in Table 1 above.

In Table 1, sample numbers 5, 8, 1
Samples 0, 12, 13, 16, and 17 are porcelains having compositions other than the limits according to the present invention, and samples Nos. 19, 20, and 21 are comparative examples. It is a sample.

As is clear from the sample results shown in Table 1, the porcelain composition according to the present invention has a relatively large relative permittivity ε _r and a small dielectric loss tangent in the high frequency band. It is a material that can control the temperature coefficient of, and is stable, and has an extremely large industrial application range or value.

[0022]

As can be seen from the above description, the porcelain composition of the present invention has a relatively large relative dielectric constant in the high frequency band and a small dielectric loss tangent, and therefore exhibits excellent effects as a dielectric used in electronic parts in the high frequency band. be able to.

Claims (1)

[Claims] 1. Magnesium oxide (MgO), calcium oxide (CaO), titanium oxide (TiO ₂ ) and chromium oxide.
A porcelain composition comprising (Cr ₂ O ₃ ), where x, y, z and u are each 25 ≦ x when the composition range of this component is expressed as xMgO · yCaO · zTiO ₂ · uCr ₂ O _3. A porcelain composition characterized by being in a range satisfying ≤80 mol% 1 ≤y ≤5 mol% 10 ≤z ≤70 mol% 0 <u ≤10 mol%.