JPH05274913A - Dielectric porcelain composite - Google Patents

Abstract

PURPOSE:To provide a porcelain having a high Q value in a microwave zone, high temperature characteristics at a dielectric constant and a resonance frequency, and ensuring high strength. CONSTITUTION:A dielectric porcelain composite comprising a main component having a composition formula of xCaO.yZrO2.zMO2/5 (where M stands for Nb and/or Ta, 0.9<x<(y+z)<=1.1, and 0<=z/(y+ z)<=0.5, but not x/y=1 and z=0), and containing 0.1 to 3wt% of at least one compound selected from Cr2O3, MnO2 and Al2O3 is used for a resonator, a substrate or the like in a microwave frequency zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel dielectric porcelain composition suitable as a resonator or a circuit board material in the microwave region.

[0002]

2. Description of the Related Art Recently, car telephones, cordless telephones,
With the practical use of personal radios and satellite broadcast receivers, dielectric porcelain is widely used as a circuit element in the microwave region. Such a dielectric ceramic for microwaves is mainly used for a resonator. The characteristics required therefor are that the relative dielectric constant is large with respect to the demand for miniaturization, and the dielectric loss tan δ at high frequencies is small. In other words, a large Q value and a small change in resonance frequency with temperature are mainly cited. For reliability,
It is chemically stable and has high mechanical strength.

Conventionally, as this type of dielectric porcelain, for example, BaO-TiO ₂ system material, BaO-REO-TiO _{2 is} used.
₂ (however, REO is a rare earth element oxide, the same applies hereinafter) and CaZrO ₃ -based materials are known.

[0004]

[Problems to be solved by the invention] However,
The BaO—TiO ₂ system material has a relative dielectric constant εr of 38 to 40.
Although the dielectric loss tan δ is as small as 2.0 × 10 ⁻⁴ , it is difficult to obtain a temperature dependence τf of the resonance frequency of zero in a single phase. Since the change in the dependency is large, it is difficult to stably control the temperature coefficient τf of the resonance frequency to be small while maintaining the high relative permittivity and the low dielectric loss.

Regarding BaO-REO-TiO ₂ -based materials, BaO-Nd ₂ O ₃ -TiO ₂ -based materials or B
The aO-Sm ₂ O ₃ -TiO ₂ system and the like are known. These systems have high permittivity εr of 40 to 60 and have a resonance frequency temperature coefficient τf of zero. The loss tan δ is as large as 5.0 × 10 ⁻⁴ or more. Furthermore C
Since the aZrO ₃ system itself has poor sinterability, it is necessary to add various auxiliaries. In all cases, tan δ is large at about 3 to 4 × 10 ^−4, and the dielectric constant and temperature characteristics are insufficient. Met. Further, all of these dielectric materials have the drawbacks of low mechanical strength and weak mechanical impact.

The present inventors have examined the CaZrO ₃ system and changed the Ca / Zr ratio, or changed Zr to N.
By substituting b or Ta, the crystallinity of the system is greatly improved, a ceramic with good crystallinity can be obtained, and an excellent ceramic with high dielectric constant, high Q value and small τf can be obtained in terms of characteristics. Have already found. However, the strength of these porcelain compositions has not reached a practical level either, and mechanical strength is still insufficient.

Therefore, the object of the present invention is to make the resonator compact and highly reliable, so that the dielectric constant (εr) is high (25 or more), the Q value is high (4000 or more), and the resonance frequency is high. It is an object of the present invention to provide a high-frequency dielectric ceramic composition having a small temperature characteristic (τf), stability, and high strength.

[0008]

The inventors of the present invention have made further studies on this specific CaZrO ₃ system, and as a result,
It has been found that by adding at least one selected from ₂ O ₃ , MnO ₂ and Al ₂ O _3, it is possible to obtain a porcelain having excellent strength without deteriorating the dielectric properties.

That is, the dielectric ceramic composition of the present invention is Ca
O, ZrO ₂ , Nb ₂ O ₅ or Ta ₂ O ₅ is used, and these are represented by a molar ratio of xCaO · yZrO ₂ · zMO _5/2 , where M is Nb and / or Ta 0.9 < x / (y + z) ≦ 1.1 0 ≦ z / (y + z) ≦ 0.5 where, as a main component a composition consisting excluding point x / y = 1, z = 0, further Cr ₂ O _3, MnO
₂ , at least one selected from Al ₂ O ₃ is 0.1 to
It is characterized by containing 3% by weight.

In the dielectric ceramic composition of the present invention, Cr
_The reason why the weight ratio of ₂ O ₃ , MnO ₂ and Al ₂ O ₃ is set in the above range is that when the amount of these is less than 0.1% by weight, there is no effect of improving the strength and more than 3% by weight. When,
This is because the Q value decreases and the temperature characteristic of the resonance frequency deteriorates.

The main component of the present invention is Ca.
The _{reason why} the ratio of each compound of O, ZrO ₂ , and MO _5/2 is limited to the above range is that x / (y + z) in the above composition formula.
Is less than 0.9, the Q value is low, and if more than 1.1, the sinterability of the porcelain decreases. Also, z / (y + z)
Is larger than 0.5, the temperature coefficient of the resonance frequency becomes large on the negative side. Also, in the above formula, when x / y = 1, z = 0, that is, CaZrO ₃ has poor sinterability and a low Q value.

When the porcelain is manufactured in the present invention, oxides of metals constituting the porcelain, that is, CaCO ₃ and Zr are used.
O ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , Cr ₂ O ₃ , Mn
O ₂ and Al ₂ O ₃ , or compounds such as carbonates, nitrates and sulfates which can be converted into the above oxides are weighed and mixed, and then calcined at 1200 to 1500 ° C. if desired. 1350-170 after molding this mixture or calcined powder
A porcelain can be obtained by firing in the atmosphere of 0 ° C.

It should be noted that B is added to the Ca element in the present invention.
a, Sr, and Hf to Zr at 5 mol% each
You can replace it with

[0014]

According to the present invention, CaO, ZrO ₂ , MO _5/2
With respect to the main component consisting of a specific ratio, Cr ₂ O ₃ , M
By adding nO ₂ or Al ₂ O ₃ , it acts as a so-called sintering aid and the density of the dielectric ceramic can be increased, whereby the mechanical properties of the ceramic are improved.

Further, since these additives do not affect the dielectric characteristics of the main component, they do not deteriorate the dielectric characteristics of the porcelain, and therefore have high reliability in applications to resonators and circuit boards. Can be given.

[0016]

The present invention will be described below with reference to the following examples. As starting materials, CaO, ZrO ₂ , Nb ₂ O _{5 with} a purity of 99% or more,
Ta ₂ O ₅ , Cr ₂ O ₃ , MnO ₂ , and Al ₂ O ₃ powders were used, and they were weighed to have a molar ratio shown in Table 1,
Pure water was added, and ball milling was performed overnight using resin balls. After drying the mixture was calcined for 2 hours at 1100 ° C., about 1 wt% of a binder and sizing after adding, by press molding the resulting powder at a pressure of about 1000 kg / cm ² with a diameter of about 20mm A cylindrical molded body having a height of about 10 mm and having no distortion was produced. In addition, about 5mm
A rectangular parallelepiped molded body having no distortion of 6 mm x 40 mm was prepared. Thereafter, these molded bodies were debindered at 400 ° C. for 4 hours and then fired in air at a temperature of 1350 to 1650 ° C. for 2 hours.

[0017]

[Table 1]

The obtained cylindrical porcelain was surface-polished and cylindrical-ground to obtain a sample for measuring dielectric properties. Using this sample, the resonance frequency of 4 ~
The dielectric constant (εr) and Q value (1 / tanδ) were measured at 6 GHz, and the temperature coefficient (τf) of the resonance frequency was −40.
It was measured in the temperature range of + 85 ° C. Further, a rectangular parallelepiped-shaped porcelain was flat-polished, and the bending strength was measured according to JISR1601.

The results are shown in Table 2.

[0020]

[Table 2]

As is clear from Table 2, CaZrO ₃
Sample No. 1 which has a low Q value. Sample No. 9 containing no additives had insufficient strength, and samples No. 8 and 12 containing a large amount of additives both had a low Q value and contained a large amount of Nb in the main component. In .13, the temperature characteristics of frequency are large and the strength is small. Further, the sample No. 18 containing no ZrO ₂ has a low Q value and poor temperature characteristics. Further, the sample No. 20 having a low CaO ratio had a low Q value.

On the other hand, the sample No. within the scope of the present invention.
2-7, 10, 11, 14-17, and 21 all have high dielectric properties and mechanical properties, and have a dielectric constant of 25 or more, a Q value of 4000 or more, and τf of ± 100 (ppm / ° C) or less. The characteristics were obtained, and the transverse rupture strength exhibited a high strength of 15 Kg / mm ² or more.

[0023]

As described above in detail, the dielectric ceramic composition of the present invention is _{CaO-ZrO 2 - (NbO 2/5} , Ta
O _2/5 ) system, Cr ₂ O ₃ , MnO ₂ , Al ₂ O
By adding ₃ to improve the sinterability of the porcelain and densify it, improve the strength without deteriorating the dielectric properties, have a high Q value in the microwave region, permittivity and temperature of the resonance frequency. It is possible to provide a porcelain having excellent characteristics and high strength. As a result, it is possible to improve reliability in use as a resonator or a circuit board material, and at the same time, reduce the size.

Claims (1)

[Claims] 1. A composition formula is xCaO.yZrO ₂ .zMO _5/2 , wherein M is Nb and / or Ta 0.9 <x / (y + z) ≦ 1.1 10 ≦ z / (y + z) ≦ 0. .5, except that x / y = 1 and z = 0 are excluded from the main component, and Cr ₂ O ₃ , MnO ₂ , A
A dielectric ceramic composition containing at least one selected from l ₂ O _{3 in} a proportion of 0.1 to 3% by weight.