JPH05117024A - Dielectric porcelain for high frequency and its production - Google Patents

Abstract

PURPOSE:To provide the dielectric porcelain consisting mainly of (Zr, Sn) TiO4 improved in low loss characteristics effectively without using expensive high- purity raw materials. CONSTITUTION:A raw material composition comprising (A) a mixture of ZrO2, SnO2 and TiO2 at a specified proportion leading to (Zr, Sn) TiO4 and (B) <=2wt.% of a metal oxide or a compound convertible thereto as sintering auxiliary is used. Also the raw material composition is adjusted to contain <=300ppm of CaO as an impurity in the product, then is fired at 1300-1400 deg.C to obtain the objective dielectric porcelain.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high frequency dielectric porcelain containing (Zr, Sn) TiO ₄ as a main component and a method for manufacturing the same, and more particularly to a technique for effectively improving low loss characteristics of the dielectric porcelain. is there.

[0002]

2. Description of the Related Art With the recent development of high-frequency devices such as mobile phones, the dielectric resonators used therein are required to have higher performance. Therefore, in the dielectric ceramic used for such a resonator, (1) high relative permittivity (ε _r ), (2) high Q value, (3) temperature coefficient of resonance frequency (τ _f ) Is required to be small. As one of the dielectric ceramics satisfying these characteristics, a dielectric ceramic mainly containing zirconium tin titanate: (Zr, Sn) TiO ₄ is known.

However, when manufacturing this dielectric ceramic, Z which gives (Zr, Sn) TiO ₄ as a main component is given.
Since rO ₂ , SnO ₂ and TiO ₂ alone cannot provide a sufficiently densified sintered body, Mn, Ni, Z
Oxides of metals such as n and Ta are added to the raw material composition as a sintering aid, and it is said that such a dielectric ceramic cannot obtain a sufficiently high Q value. The problem was inherent.

Therefore, in Japanese Patent Laid-Open No. 58-18808, Zr having a purity of 99.9% or more is used.
Using O ₂ , SnO ₂ and TiO ₂ as raw materials,
A method for obtaining a sufficiently densified sintered body by firing at a firing temperature of 00 to 1600 ° C. without adding a sintering aid to obtain a high Q value is disclosed. When such high-purity raw materials are used, there is a problem that the manufacturing cost becomes extremely high.

[0005]

The present invention has been made in view of such circumstances, and the problem to be solved is to use raw materials of high purity such as a purity of 99.9% or more, By controlling the specific chemical components contained in the dielectric porcelain as impurities, the cost is sufficiently low,
Another object is to obtain a high frequency dielectric ceramic having a high Q value.

[0006]

As a result of intensive studies conducted by the present inventors in order to solve the above-mentioned problems, among the impurities contained in the dielectric ceramic, the content of CaO is particularly Q of the dielectric ceramic.
The present invention has been completed on the basis of such findings, since it has been found that it greatly affects the value.

That is, the present invention relates to (Zr, Sn) Ti
O ₄ as the main component and CaO content as an impurity is 3
The gist is a high-frequency dielectric ceramic characterized by being set to 00 ppm or less.

Further, according to the present invention, as a method for producing such a high frequency dielectric ceramic, ZrO ₂ , SnO ₂ and TiO ₂ which give (Zr, Sn) TiO ₄ are mixed at a predetermined ratio and further baked. When a raw material composition containing a metal oxide or a compound producing the same in an amount of 2% by weight or less is used as a co-agent, the raw material composition is fired to produce a dielectric porcelain. C
The gist of the present invention is that the raw material composition is prepared so that the content of aO is 300 ppm or less, and then the raw material composition is fired at a firing temperature of 1300 to 1400 ° C.

[0009]

That is, in the present invention, among various impurities contained in the dielectric porcelain, focusing attention on CaO, which has a large adverse effect on the Q value, and setting its content to 300 ppm or less, It was possible to increase the Q value extremely effectively, which made it possible to obtain a high Q value even if other impurities were contained to some extent and a sintering additive was added. Of. Therefore, it is not necessary to use high-purity raw materials of 99.9% or more, which are high in cost, and use raw materials of general purity in consideration of the content of CaO contained in each raw material. By preparing the raw material composition, it becomes possible to advantageously reduce the cost of the dielectric ceramic. Further, by adding a sintering aid, the dielectric ceramics can be sufficiently densified by firing at 1300 to 1400 ° C., and it is possible to effectively prevent the over firing of the dielectric ceramics. It was decided.

[0010]

Concrete Structure By the way, zirconium tin titanate which is a main component of the dielectric ceramics of the present invention: (Zr, Sn)
Raw material powders that give TiO ₄ include ZrO ₂ and Sn.
With respect to both O ₂ and TiO ₂ , those generally used conventionally can be appropriately used in consideration of the content of CaO, and they will be mixed at a predetermined ratio. It should be noted that, in general, ZrO ₂ : 44 to 51 wt%, so that the relative permittivity (ε _r ) and the temperature coefficient (τ _f ) of the resonance frequency of the obtained dielectric porcelain are suitable for practical use.
It is desirable to mix SnO _{2 in} the range of 10 to 41 wt% and TiO _{2 in} the range of 36 to 41 wt%.

Further, in the present invention, it is difficult to obtain a sufficiently densified sintered body (dielectric ceramics) with only these three components. Therefore, a predetermined metal oxide is used as a sintering aid. An object or a compound which produces such a metal oxide will be contained. As the metal oxide, any conventionally known one can be used, for example,
MnCO ₃ (MnO), NiO, ZnO, Ta ₂ O ₅ ,
Co ₂ O ₃ , Sb ₂ O ₅ , WO ₃ , Nb ₂ O ₅ , La ₂
O _{3 and the} like can be mentioned. They are alone or 2
It is possible to use more than one kind in an appropriate combination, and the total amount is 2% by weight or less.

Thus, in the present invention, as the above-mentioned raw material powder and sintering aid, those having a general purity can be used, while mainly as impurities resulting from those raw material powder and sintering aid. The raw material composition is prepared so that the content of CaO is 300 ppm or less. For example, the content of CaO in each raw material component is 300 ppm
In the following, each raw material component is compounded, and even if the CaO content in one raw material component is 300 ppm or more, the one having a low CaO content is used as the other raw material component, CaO content is 300pp
The raw material composition is prepared so as to be not more than m. For example, among the raw material powders, ZrO ₂ has various contents of CaO as an impurity of about 30 to 50 ppm to about 800 ppm. Therefore, selection and combination with other raw material components , Caution is required. As is conventionally known, when the dielectric ceramic contains Fe ₂ O ₃ as an impurity, the Q value of the ceramic is lowered (Journal of the A
American Ceramic Society, Vol.67, No.4, P.278),
Also in the present invention, in order to prevent the Q value from decreasing, Fe ₂
Needless to say, it is desirable to reduce the content of O ₃ .

The raw material composition prepared in this manner is molded into a desired molded body according to a conventional method and fired at a firing temperature of 1300 to 1400 ° C.
It will be set in the range of. Baking temperature is 1300 ℃
If it is lower than that, firing becomes difficult in practice,
On the other hand, if the firing temperature is higher than 1400 ° C., over-firing may occur, causing problems such as a decrease in Q value. More preferably 1350 ° C to 1400 ° C
It is baked at the temperature of.

The dielectric porcelain thus obtained does not use a high-purity raw material in particular, and the content of CaO as an impurity is 300 ppm or less in spite of the addition of a sintering aid. Based on what is said to be
It has an extremely high Q value, and is usually 1
A high Q value of 2000 or more can be obtained. And
Since the raw material cost is reduced, the cost of the dielectric ceramic can be advantageously reduced.

[0015]

EXAMPLES Some examples of the present invention will be shown below to clarify the present invention in more detail. However, the present invention is not limited by the description of such examples. Needless to say, it is not something to receive. Further, in addition to the following specific examples, in addition to the following embodiments, the present invention includes various modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention.
It should be understood that modifications, improvements, etc. may be made.

First, commercially available zirconium oxide (Zr
O ₂ ), titanium oxide (TiO ₂ ), tin oxide (Sn
O ₂ ) and manganese carbonate (MnC) which is a sintering aid.
O ₃ ), zinc oxide (ZnO), nickel oxide (Ni
O) and tantalum oxide (Ta ₂ O ₅ ) are prepared, the components are selected and combined in consideration of the CaO content of each component, and the composition and total CaO amount of the raw material components are shown in Table 1 below. Are weighed so as to give, and put into a polyethylene pot together with zirconia boulders and pure water, and mixed to give 1
One kind of raw material composition was obtained. Then, after drying each raw material composition, 1% by weight of PVA as a binder was added and mixed, and further passed through a 40-mesh sieve to granulate.

Next, each of the granulated powders was subjected to a pressure of 300 kg / cm ² by a uniaxial press molding machine and a diameter of 20.
mm × thickness: 1t / after preforming into a disk shape of 12mm
CIP treatment at a pressure of cm ² and 1350 in air
Baking was performed at a temperature of ˜1400 ° C. for 4 hours. Then, the obtained fired body was ground to a size of 16 mm in diameter and 8 mm in thickness.

The relative permittivity (ε
_r ), Q value, temperature coefficient (τ _f ) of resonance frequency,
The results are also shown in Table 2 below. The relative permittivity (ε _r ) and the Q value are measured by a known parallel conductor plate type dielectric resonator method, and the Q value is converted into a value at 3 GHz in Table 2. The temperature coefficient of the resonance frequency is -25 to 7
It was measured in the range of 5 ° C. The measurement frequency was 6 to 7 GHz.

[0019]

[Table 1]

[0020]

[Table 2]

As is clear from the results of Tables 1 and 2, the Q value varies depending on the total amount of CaO in the fired body, and the total amount of CaO exceeds 300 ppm, Nos. 1 to 3 and N.
In the fired body of o.7, a sufficiently high Q value was not obtained.
On the other hand, in the fired bodies of Nos. 4 to 6 and Nos. 8 to 11 in which the content of CaO is 300 ppm or less, the Q value is an extremely high value of 14000 to 15000.

Claims (2)

[Claims] 1. A main component of (Zr, Sn) TiO ₄ ,
Content of CaO as an impurity is 300 ppm or less, The dielectric ceramics for high frequencies characterized by the above-mentioned. 2. ZrO which gives (Zr, Sn) TiO _4.
A raw material composition prepared by mixing ₂ , SnO ₂ and TiO ₂ at a predetermined ratio and further containing a metal oxide or a compound which produces the metal oxide as a sintering aid at a ratio of 2% by weight or less is used. When a dielectric ceramic is manufactured by firing a material, after preparing the raw material composition so that the content of CaO as an impurity is 300 ppm or less, firing at a firing temperature of 1300 to 1400 ° C. And a method for manufacturing a high frequency dielectric porcelain.