Dielectric porcelain composition and dielectric resonator using the composition Number:7,160,826 from the United States Patent and Trademark Office (PTO) owispatent A dielectric porcelain composition includes MgTiO.sub.3 and Mg.sub.2SiO.sub.4 and satisfies a+b=1 and 0<b<1, wherein a denotes a molar ratio of MgTiO.sub.3 and b denotes a molar ratio of Mg.sub.2SiO.sub.4. It can include MgTiO.sub.3 and CaTiO.sub.3 and satisfy a+c=1 and 0<c.ltoreq.0.15, wherein a has the same meaning as shown above and c denotes a molar ratio of CaTiO.sub.3. It can also include MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 and satisfy a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a, b and c have the same meanings as shown above. These compositions can be manufactured, with the content of Mg.sub.2SiO.sub.4, the content of CatiO.sub.3 and the contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3 adjusted, respectively. These compositions can be used as dielectric materials to manufacture dielectric resonators.<H composition, dielectric, Dielectric, porc, 7160826.html, Patent, pto, 7160826

Title: Dielectric porcelain composition and dielectric resonator using the composition

Abstract: A dielectric porcelain composition includes MgTiO.sub.3 and Mg.sub.2SiO.sub.4 and satisfies a+b=1 and 0<b<1, wherein a denotes a molar ratio of MgTiO.sub.3 and b denotes a molar ratio of Mg.sub.2SiO.sub.4. It can include MgTiO.sub.3 and CaTiO.sub.3 and satisfy a+c=1 and 0<c.ltoreq.0.15, wherein a has the same meaning as shown above and c denotes a molar ratio of CaTiO.sub.3. It can also include MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 and satisfy a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a, b and c have the same meanings as shown above. These compositions can be manufactured, with the content of Mg.sub.2SiO.sub.4, the content of CatiO.sub.3 and the contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3 adjusted, respectively. These compositions can be used as dielectric materials to manufacture dielectric resonators.

Patent Number: 7,160,826 Issued on 01/09/2007 to Miyauchi, et al.

Inventors: Miyauchi; Yasuharu (Tokyo, JP), Arashi; Tomohiro (Tokyo, JP)
Assignee: TDK Corporation (Tokyo, JP)

Appl. No.: 10/798,355

Filed: March 12, 2004

Foreign Application Priority Data


Mar 17, 2003 [JP]			2003-071545

Current U.S. Class: 501/136 ; 501/154

Current International Class: C04B 35/20 (20060101); C04B 35/465 (20060101)

Field of Search: 501/136,154

References Cited [Referenced By]

U.S. Patent Documents


4242213	December 1980	Tamura et al.
5340784	August 1994	Katoh et al.
5616528	April 1997	Toda et al.
5683790	November 1997	Suzuki et al.
5846892	December 1998	Takada

Foreign Patent Documents


0727789	Aug., 1996	EP
1460645	Sep., 2004	EP
61-14605	Apr., 1986	JP
6-56519	Mar., 1994	JP
8-208330	Aug., 1996	JP
2002-193662	Jul., 2002	JP

Other References

Patent Abstracts of Japan, vol. 2002, No. 11, Nov. 6, 2002. cited by other .
Patent Abstracts of Japan, vol. 1996, No. 12, Dec. 26, 1996. cited by othe- r .
Patent Abstracts of Japan, vol. 0182, No. (c-1207), Jun. 2, 1994. cited by other .
English Language Abstract of JP 2002-193662. cited by other .
"Ceramics Engineering Handbook", edited by Japan Ceramics Society and published by Gihodo, vol. 1, p. 1885,(May 30, 1993). cited by other.

Primary Examiner: Brunsman; David M.
Attorney, Agent or Firm: Greenblum & Bernstein, P.L.C.

Claims

The invention claimed is:

1. A dielectric porcelain composition calcined at a temperature of not less than 1300.degree. C. comprising MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 and satisfying a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3.

2. The composition according to claim 1, wherein the molar ratio b is defined as 0.5.ltoreq.b<1 and the molar ratio c is defined as 0.05.ltoreq.c.ltoreq.0.09.

3. A dielectric resonator comprising as a dielectric material a dielectric porcelain composition calcined at a temperature of not less than 1300.degree. C. that comprises MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 and satisfies a+b+c=1,0.ltoreq.b.ltoreq.1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3.

4. A manufacturing process for a dielectric porcelain composition that comprises MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3, comprising adjusting respective contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3 to satisfy a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3, thereby adjusting relative permittivity .epsilon.r and temperature coefficient .tau.f, and calcining these materials at a temperature of not less than 1300.degree. C.

5. A dielectric porcelain composition consisting of MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 and satisfying a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3.

6. The composition according to claim 5, wherein the molar ratio b is defined as 0.5 b<1 and the molar ratio c is defined as 0.05.ltoreq.c.ltoreq.0.09.

7. A dielectric resonator comprising as a dielectric material a dielectric porcelain composition consisting of MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 and satisfies a+b+c=1, 0<b.ltoreq.1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3.

8. A manufacturing process for a dielectric porcelain composition consisting of MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3, comprising adjusting respective contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3 to satisfy a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3, thereby adjusting relative permittivity .epsilon.r and temperature coefficient .tau.f.

Description

The present invention relates to a dielectric porcelain composition particularly excellent in characteristics at a millimeter-wave bandwidth region, a dielectric resonator using the composition, and a process for the manufacture of the composition and resonator capable of controlling the characteristics (relative permittivity .epsilon.r and temperature coefficient .tau.f).

DESCRIPTION OF THE PRIOR ART

While various dielectric materials have been known as dielectric materials for high frequency, magnesium titanate-based dielectric materials have been known as one of the materials having a relatively high Qf value. According to "Ceramics Engineering Handbook," edited by Japan Ceramics Society and published by Gihodo, Vol. 1, p. 1885, May 30, 1993, MgTiO.sub.3 that is a magnesium titanate-based dielectric material, has relative permittivity .epsilon.r of 17, a Qf value of 110000 GHz and temperature dependency of resonance frequency (temperature coefficient .tau.f) of -45 ppm/K.

In addition, improvements in magnesium titanate-based materials have also been proposed. For example, JP-B SHO 61-14605 discloses a dielectric material obtained by sintering a material containing titanium dioxide and more than 1 mole and not more than 1.3 moles of magnesium oxide per mole of the titanium dioxide. As the characteristics of the dielectric material of the prior art, it is disclosed that the relative permittivity .epsilon.r=17.3 and no load Qu=12000 (120000 GHz in terms of the Qf value) when MgO:TiO.sub.2=1.2:1.

JP-A 2002-193662 discloses dielectric porcelain comprising a first crystal phase of at least one species consisting of MgTiO.sub.3, CaTiO.sub.3, Mg.sub.2SiO.sub.4 and BaTi.sub.4O.sub.9, a second crystal phase of at least one species consisting of Mg.sub.2TiO.sub.4, Mg.sub.2B.sub.2O.sub.5 and Li.sub.2TiSiO.sub.5 and oxides of Si, B and Li, with the aim of materializing dielectric porcelain having a high Qf value, with neither flexion nor distortion produced when being calcined together with a conductive material.

Though the technologies in the field of date communications have recently been developed conspicuously, the characteristics required for dielectric materials used for dielectric resonators or other such devices, including the aforementioned Qf value, tend to be diversified due to applications, frequency bandwidths and the like.

In consideration of an application particularly as a resonator material, it is required from a standpoint of ready design to develop dielectric materials having relative permittivity .epsilon.r low to a certain extent as one of the characteristics of dielectric materials for submillimeter-wave and millimeter-wave regions. Since the dimension of a resonance phenomenon is directly proportionate to .epsilon..sup.-1/2 when the dielectric constant is defined as .epsilon., when a material having high relative permittivity is used, the dimension of a resonator has to be extremely small with an increasing frequency. In order to make it easy to design a resonator, it is demanded to develop a dielectric material having appropriate relative permittivity .epsilon.r taking the entire dimension and workability into consideration.

When the dielectric material is used for a resonator, it is generally noted that the temperature coefficient .tau.f is desirably as small as possible. It is further preferable in view of the temperature coefficient of the peripheral parts and other such surrounding parts that the temperature coefficient be set at an optional value to a certain extent.

From these viewpoints, the prior art technologies, such as those disclosed by JP-B SHO 61-14605 and JP-A 2002-193662, for example, pay principal attention to an improvement in the Qf value and Q value, with relative permittivity .epsilon.r and temperature coefficient .tau.f taken little into consideration.

In the materials available on the market, which have small relative permittivity .epsilon.r and small temperature coefficient .tau.f, the former is about 12.6 and the latter is about -10 ppm/K. These values do not necessarily suffice.

The present invention has been proposed in view of the state of the conventional affairs.

One object of the present invention is to provide a dielectric porcelain composition and a dielectric resonator using the composition, in which the relative permittivity .epsilon.r can be adjusted to a relatively small value, and it is made possible to readily design submillimiter-wave resonators and millimeter-wave resonators, for example.

Another object of the present invention is to provide a dielectric porcelain composition and a dielectric resonator using the composition, in which the temperature coefficient .tau.f can be made small as much as possible and slightly adjusted in accordance with the surrounding circumstances and the like.

Still another object of the present invention is to provide a dielectric porcelain composition and a dielectric resonator using the composition, in which the relative permittivity .epsilon.r has been adjusted to a small value to a certain extent and the temperature coefficient .tau.f has been adjusted to the vicinity of zero.

Yet another object of the present invention is to provide a process for optionally adjusting the characteristics (relative permittivity .epsilon.r and temperature coefficient .tau.f) of a dielectric porcelain composition.

The present inventors have keenly continued their studies over a long period of time in order to attain the objects mentioned above. As a result, they have found that addition of Mg.sub.2SiO.sub.4 to MgTiO.sub.3 enables the relative permittivity .epsilon.r to be freely adjusted in accordance with the content of Mg.sub.2SiO.sub.4, with the temperature coefficient .tau.f varied little, and also to be set optimum in submillimeter-wave or millimeter-wave bandwidth regions and that addition of CaTiO.sub.3 to MgTiO.sub.3 enables the temperature coefficient .tau.f to be set optional in the vicinity of zero in accordance with the content of CaTiO.sub.3, with the relative permittivity .epsilon.r not so much varied. The present invention has been perfected based on these findings.

According to one aspect of the present invention, a dielectric porcelain composition comprising MgTiO.sub.3 and Mg.sub.2SiO.sub.4 is characterised in that the composition satisfies a+b=1 and 0<b<1, wherein a denotes a molar ratio of MgTiO.sub.3 and b denotes a molar ratio of Mg.sub.2SiO.sub.4; a dielectric porcelain composition comprising MgTiO.sub.3 and CaTiO.sub.3 is characterised in that the composition satisfies a+c=1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio MgTiO.sub.3 of and c denotes a molar ratio of CaTiO.sub.3; or a dielectric porcelain composition comprising MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 is characterised in that the composition satisfies a+b+c=1, 0<b<1 and 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3.

In the dielectric porcelain compositions, relative permittivity .epsilon.r and temperature coefficient .tau.f can be obtained at optional values, respectively, in the range of 6.8 to 18 and in the range of -55 to +55 ppm/K. There can be realized a dielectric porcelain composition having relative permittivity .epsilon.r in the vicinity of 10 and temperature coefficient .tau.f in the vicinity of zero, for example.

The dielectric porcelain composition can be used as a dielectric material for dielectric resonators, such as submillimeter-wave resonators and millimeter-wave resonators. Therefore, the dielectric resonator of the present invention uses the dielectric porcelain composition as its resonator material.

As described above, the addition of Mg.sub.2SiO.sub.4 to MgTiO.sub.3 enables the relative permittivity .epsilon.r to be freely adjusted in accordance with the content of Mg.sub.2SiO.sub.4, and the addition of CaTiO.sub.3 to MgTiO.sub.3 enables the temperature coefficient .tau.f to be set optional in the vicinity of zero in accordance with the content of CaTiO.sub.3. In view of these, the adjustment of the contents of these components enables adjustment of the characteristics of a dielectric porcelain composition to be obtained.

According to another aspect of the present invention, there is provided a manufacturing process for the dielectric porcelain composition, which can control the characteristics of the composition. Specifically, the contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3 are adjusted respectively within predetermined ranges to adjust the relative permittivity .epsilon.r and temperature coefficient .tau.f.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, characteristic features and advantages of the present invention will become apparent to those skilled in the art from the description to be give herein below with reference to the accompanying drawings, in which:

FIG. 1 is a flow chart showing one example of a manufacturing process for a dielectric porcelain composition according to the present invention,

FIG. 2 is an X-ray diffraction chart of 0.6MgTiO.sub.3-0.4Mg.sub.2SiO.sub.4,

FIG. 3 is a characteristic diagram showing the relationship between Mg.sub.2SiO.sub.4 content and the relative permittivity .epsilon.r in a system of MgTiO.sub.3--Mg.sub.2SiO.sub.4,

FIG. 4 is a characteristic diagram showing the relationship between Mg.sub.2SiO.sub.4 content and the temperature coefficient .tau.f in the MgTiO.sub.3--Mg.sub.2SiO.sub.4 system,

FIG. 5 is a characteristic diagram showing the relationship between the calcining temperature and the relative density in the MgTiO.sub.3--Mg.sub.2SiO.sub.4 system,

FIG. 6 is an X-ray diffraction chart of 0.91MgTiO.sub.3-0.09CaTiO.sub.3,

FIG. 7 is a characteristic diagram showing the relationship between CaTiO.sub.3 content and the relative permittivity .epsilon.r in a system of MgTiO.sub.3--CaTiO.sub.3,

FIG. 8 is a characteristic diagram showing the relationship between CaTiO.sub.3 content and the temperature coefficient .tau.f in the MgTiO.sub.3--CaTiO.sub.3 system,

FIG. 9 is a characteristic diagram showing the relationship between the calcining temperature and the relative density in the MgTiO.sub.3--CaTiO.sub.3 system,

FIG. 10 is an X-ray diffraction chart of 0.2275MgTiO.sub.3-0.6825Mg.sub.2SiO.sub.4-0.09CaTiO.sub.3,

FIG. 11 is a characteristic diagram showing the results of relative permittivity .epsilon.r measured in a system of MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3, with 0.05 mol of CaTiO.sub.3 fixed and with the Mg.sub.2SiO.sub.4 substitution amount varied,

FIG. 12 is a characteristic diagram showing the results of temperature coefficient .tau.f measured in the MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3 system, with 0.05 mol of CaTiO.sub.3 fixed and with the Mg.sub.2SiO.sub.4 substitution amount varied,

FIG. 13 is a characteristic diagram showing the results of relative density measured in the MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3 system, with 0.05 mol of CaTiO.sub.3 fixed and with the Mg.sub.2SiO.sub.4 substitution amount varied,

FIG. 14 is a characteristic diagram showing the results of relative permittivity .epsilon.r measured in a system of MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3, with MgTiO.sub.3:Mg.sub.2SiO.sub.4 fixed to 1:3 and with the CaTiO.sub.3 substitution amount varied,

FIG. 15 is a characteristic diagram showing the results of temperature coefficient .tau.f measured in the MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3 system, with MgTiO.sub.3:Mg.sub.2SiO.sub.4 fixed to 1:3 and with the CaTiO.sub.3 substitution amount varied, and

FIG. 16 is a characteristic diagram showing the results of relative density measured in the MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3 system, with MgTiO.sub.3:Mg.sub.2SiO.sub.4 fixed to 1:3 and with the CaTiO.sub.3 substitution amount varied.

The dielectric porcelain composition, dielectric resonator using the composition and manufacturing process for the composition according to the present invention will be described hereinafter in detail.

The dielectric porcelain composition of the present invention comprises magnesium titanate MaTiO.sub.3 added with either one or both of Mg.sub.2SiO.sub.4 and CaTiO.sub.3.

Though MaTiO.sub.3 has excellent characteristics that include a high Qf value, it exhibits slightly high relative permittivity .epsilon.r of about 18.2 and large temperature coefficient .tau.f of -57 ppm/K. In view of this, added to MaTiO.sub.3 in the present invention are Mg.sub.2SiO.sub.4 to improve the relative permittivity .epsilon.r and CaTiO.sub.3 to improve the temperature coefficient .tau.f.

When Mg.sub.2SiO.sub.4 is added to MaTiO.sub.3, the relative permittivity .epsilon.r decreases substantially in proportion to the content of Mg.sub.2SiO.sub.4, whereas the temperature coefficient .tau.f varies little. On the other hand, when CaTiO.sub.3 is added to MaTiO.sub.3, the temperature coefficient .tau.f shifts gradually from the minus side to the plus side, whereas the relative permittivity .epsilon.r arises little. For these reasons, the relative permittivity .epsilon.r and temperature coefficient .tau.f can independently be controlled depending on the contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3.

From these standpoints, Mg.sub.2SiO.sub.4 or CaTiO.sub.3 is added to MaTiO.sub.3. It is preferable that the content of Mg.sub.2SiO.sub.4 should satisfy that a+b=1 and that 0<b<1, wherein a denotes the molar ratio of MgTiO.sub.3 and b denotes the molar ratio of Mg.sub.2SiO.sub.4. Controlling the content of Mg.sub.2SiO.sub.4 optionally to satisfy these enables the relative permittivity .epsilon.r to be freely controlled to a value lower than that MaTiO.sub.3 has, e.g. in the range of 6.8 to 18. However, when the relative permittivity .epsilon.r is to be set at a value suitable for use in submillimeter-wave and millimeter-wave regions, e.g. a value of not more than 12, the b is more preferably defined as 0.5.ltoreq.b<1.

In the case of CaTiO.sub.3 added to MaTiO.sub.3, it is preferable that the content thereof should satisfy that a+c=1 and that 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3 and c denotes a molar ratio of CaTiO.sub.3. Controlling the content of CaTiO.sub.3 optionally to satisfy these enables the temperature coefficient .tau.f to be freely controlled to a value in the range of -55 to +55 ppm/K. In order to control the temperature coefficient .tau.f to be as close as zero, i.e. around 30 ppm/K, however, the c is more preferably defined as 0.03.ltoreq.c.ltoreq.0.08.

When both Mg.sub.2SiO.sub.4 and CaTiO.sub.3 are added to MaTiO.sub.3, the contents thereof may be adjusted to respectively suitable amounts to satisfy that a+b+c=1, that 0<b<1 and that 0<c.ltoreq.0.15, wherein a denotes a molar ratio of MgTiO.sub.3, b denotes a molar ratio of Mg.sub.2SiO.sub.4 and c denotes a molar ratio of CaTiO.sub.3.

In order to control the relative permittivity .epsilon.r to be a value suitable for use in submillimeter-wave and millimeter-wave regions, e.g. a value of not more than 12, and the temperature coefficient .tau.f to be as close as zero, the contents of Mg.sub.2SiO.sub.4 and CaTiO.sub.3 may be adjusted as mentioned above. Though their respective optimum values are slightly different from the defined values, the more preferably ranges are 0.5.ltoreq.b<1 and 0.05.ltoreq.c.ltoreq.0.09, respectively.

It is noted that since it is clear from the X-ray diffraction that the respective components of the dielectric porcelain composition exist respectively in the form of MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CatiO.sub.3 and that the matrix thereof is a crystal phase having the three components combined, the composition is to be represented by their ratios in mol.

Based on the above, by controlling the ratios of the respective components, a dielectric porcelain composition exhibiting the relative permittivity .epsilon.r of 10.86, temperature coefficient .tau.f of -2.7 ppm/K and Qf value of 74000 GHz can be materialised.

The manufacturing process for the dielectric porcelain composition according to the present invention will be described herein below. The flow chart thereof adopted by the present invention is as shown in FIG. 1.

In the manufacturing process of the present invention, MgO, TiO.sub.2, CaCO.sub.3 and SiO.sub.2 are used as raw materials, for example. While the respective components are mixed in accordance with their respectively desired characteristics, since the prepared composition is reflected substantially as it is by the composition of the dielectric porcelain composition, the raw material components are mixed so that the prepared composition and the composition of the dielectric porcelain composition can have the relationship of 1:1.

The process of manufacturing the dielectric porcelain composition will be described. The raw materials, MgO, TiO.sub.2, CaCO.sub.3 and SiO.sub.2, are mixed at a mixing process 1 to obtain a mixture. The mixture is subjected to a drying process 2 and a shaping process 3 and preliminarily calcined at a calcining process 4. The preliminary calcining is performed in order for the reaction of the raw materials to proceed to a certain extent and generally at a temperature slightly lower than that used in the sintering.

The preliminarily calcined product is milled at a milling process 5 and then dried at a drying process 6. The dried product is granulated at a granulating process 7. In the granulating process, a binder is mingled with the dried product. Though any optional binder can be used, polyvinyl alcohol or the like can advantageously be used, for example.

The granulated product is shaped into a desired shape at a shaping process 8 and sintered at a sintering process 9. The sintering temperature used at the sintering process is adjusted in the range of 1250.degree. C. to 1500.degree. C., for example. The optimum sintering temperature is made slightly different depending on the raw materials for the dielectric porcelain composition. When manufacturing a dielectric porcelain composition comprising MgTiO.sub.3 and Mg.sub.2SiO.sub.4, the sintering temperature of not less than 1300.degree. C. is preferred. In this case, when the sintering temperature is less than 1300.degree. C., the Qf value will be lowered and the relative density will also be lowered. In the case of a dielectric porcelain composition comprising MgTiO.sub.3 and CaTiO.sub.3, it is preferable to use the sintering temperature of not less than 1250.degree. C. When it is less than 1250.degree. C., both the Qf value and the relative density are lowered similarly to the case mentioned above. When a dielectric porcelain composition comprising MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 is to be manufactured, the sintering temperature of not less than 1300.degree. C. is preferable. By setting the sintering temperature within the aforementioned range, the Qf value and relative density can be maintained at high levels, respectively.

In the manufacturing process, MgO, TiO.sub.2, CaCO.sub.3 and SiO.sub.2 are used as the raw materials. However, this is by no means limitative. For example, MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 can be prepared in advance at their predetermined ratios and used in the manufacturing process.

The dielectric porcelain composition can be used at the frequency bandwidths of submillimeter-waves and millimeter-waves, e.g. 30 to 300 GHz. The frequency bandwidths include that of a radar for automobiles (using the frequency of 77 GHz:38.5 GHz multiplied by 2).

Therefore, the dielectric porcelain composition of the present invention can be used as a material for resonators used in the submillimeter-wave and millimeter-wave regions and a substrate material for MIC dielectrics, and for dielectric waveguides, dielectric antennas, impedance matching of various kinds of millimeter-wave circuits and other such electronic parts. It can suitably be used for dielectric resonators.

The present invention will be described based on concrete experimental results.

Samples of a dielectric porcelain composition were produced in accordance with the following procedure.

MgO, TiO.sub.2, CaCO.sub.3 and SiO.sub.2 were weighed so that these raw materials had a predetermined mixing ratio and then mixed with a ball mill for 16 hours. The mixture obtained was dried at 120.degree. C. for 24 hours and then shaped under a shaping pressure of 200 kgf/cm.sup.2 into a disc 60 mm in diameter.

The disc was preliminarily calcined at 1100.degree. C. for 2 hours, then milled for 16 hours using the ball mill and dried at 120.degree. C. for 24 hours. The dried product was granulated, with 1% by weight of polyvinyl alcohol added thereto, and shaped under a shaping pressure of 2000 kgf/cm.sup.2 into a 12 mm-diameter.

Finally, the shaped product was principally calcined to obtain dielectric porcelain composition samples.

In accordance with the process of producing the dielectric porcelain composition samples, MgTiO.sub.3 and Mg.sub.2SiO.sub.4 used as raw materials were mixed so that b is in the range of 0 to 1, provided that a+b=1, when the molar ratio of MgTiO.sub.3 was defined as a and the molar ratio of Mg.sub.2SiO.sub.4 was defined as b. The mixture was sintered at a temperature of 1250.degree. C. to 1500.degree. C. to obtain various samples.

A sample of 0.6MgTiO.sub.3-0.4Mg.sub.2SiO.sub.4, wherein a=0.6 and b=0.4, was measured using an X-ray diffraction apparatus. The results of measurement are shown in FIG. 2. It can be observed from the X-ray diffraction chart that there exist peaks resulting respectively from MgTiO.sub.3 and Mg.sub.2SiO.sub.4, from which it is found that the sample comprises a mixed crystal of MgTiO.sub.3 and Mg.sub.2SiO.sub.4.

The relative permittivity .epsilon.r and temperature coefficient .tau.f of each sample were measured in accordance with the "Method of Testing Dielectric Characteristics of Fine Ceramics for Microwaves" of the Japanese Industrial Standards (JIS R 1627). The results of relative permittivity .epsilon.r measurement are shown in FIG. 3 and Table 1 below, and the results of temperature coefficient .tau.f measurement are shown in FIG. 4 and Table 2 below.

TABLE-US-00001 TABLE 1 Molar ratio Relative Relative Relative Relative Relative b of permittivity permittivity permittivity permittivity permittivity Mg.sub.2SiO.sub.4 .epsilon.r at 1300.degree. C. .epsilon.r at 1350.degree. C. .epsilon.r at 1400.degree. C. .epsilon.r at 1450.degree. C. .epsilon.r at 1500.degree. C. 0.0 17.90 18.16 18.24 18.17 18.22 0.1 16.05 16.33 16.36 16.24 16.07 0.2 14.06 14.61 14.67 14.64 14.41 0.4 11.23 11.88 11.99 11.93 11.84 0.5 10.25 10.53 10.64 10.63 10.62 0.6 9.54 9.59 9.65 9.67 9.69 0.8 7.93 7.99 8.08 8.14 8.16 0.9 7.26 7.41 7.45 7.47 7.49 1.0 6.55 6.89 6.98 6.99 6.91

TABLE-US-00002 TABLE 2 Molar ratio b Temperature coefficient of Mg.sub.2SiO.sub.4 .tau.f at 1450.degree. C. (ppm/K) 0.0 -57.6 0.1 -52.1 0.2 -58.0 0.4 -60.3 0.5 -62.1 0.6 -62.8 0.8 -63.1 0.9 -64.0 1.0 -65.3

As is clear from FIG. 3 and Table 1 above, it is found that the relative permittivity .epsilon.r gradually decreases in proportion as the Mg.sub.2SiO.sub.4 content increases. As shown in FIG. 4 and Table 2 above, it is found that the temperature coefficient .tau.f varies little even when the Mg.sub.2SiO.sub.4 content varies.

This means that controlling the Mg.sub.2SiO.sub.4 content enables the relative permittivity .epsilon.r to be controlled without affecting the other characteristic (temperature coefficient .tau.f). Particularly when the molar ratio b of Mg.sub.2SiO.sub.4 is set to be 0.5 or more, the relative permittivity .epsilon.r of 12 or less can be materialised.

The relative density of each sample produced was also measured. The results of measurement are shown in FIG. 5 and Table 3 below. As is clear from FIG. 5 and Table 3, while the relative density shows a slight drop at 1300.degree. C., it varies little at a temperature of more than 1300.degree. C. Desired relative density could not be obtained when the calcining temperature was 1200.degree. C. or less (not shown). Therefore, when Mg.sub.2SiO.sub.4 is used to control the relative permittivity .epsilon.r, it can be said that the calcining temperature is preferably set to be 1300.degree. C. or more.

TABLE-US-00003 TABLE 3 Relative Relative Relative Relative Relative Molar density density density density density ratio b of (%) at (%) at (%) at (%) at (%) at Mg.sub.2SiO.sub.4 1300.degree. C. 1350.degree. C. 1400.degree. C. 1450.degree. C. 1500.degree. C. 0.0 97.5 98.4 99.0 98.7 98.6 0.1 97.6 98.6 98.6 98.0 97.6 0.2 95.5 97.7 98.2 97.8 97.1 0.4 93.5 96.9 97.4 97.3 96.8 0.5 92.9 96.3 97.9 97.2 97.1 0.6 92.5 95.6 98.2 97.0 96.9 0.8 91.5 94.8 97.6 97.0 96.9 0.9 90.9 94.0 97.6 96.9 97.8 1.0 90.2 92.3 97.8 97.1 97.5

In accordance with the process of producing the dielectric porcelain composition samples, MgTiO.sub.3 and CaTiO.sub.3 used as raw materials were mixed so that c is in the range of 0 to 0.09, provided that a+c=1, when the molar ratio of MgTiO.sub.3 was defined as a and the molar ratio of CaTiO.sub.3 was defined as c. The mixture was principally calcined at a temperature of 1300.degree. C. to obtain various samples.

In FIG. 6, shown are measurement results of a sample of 0.91MgTiO.sub.3-0.09CaTiO.sub.3, wherein a=0.91 and c=0.09, measured using an X-ray diffraction apparatus. It can be observed from the X-ray diffraction chart that there exist peaks resulting respectively from MgTiO.sub.3 and CaTiO.sub.3, from which it is found that the sample comprises a mixed crystal of MgTiO.sub.3 and CaTiO.sub.3.

The relative permittivity .epsilon.r and temperature coefficient .tau.f of each sample were measured in accordance with the "Method of Testing Dielectric Characteristics of Fine Ceramics for Microwaves" of the Japanese Industrial Standards (JIS R 1627). The results of relative permittivity .epsilon.r measurement are shown in FIG. 7 and Table 4 below, and the results of temperature coefficient .tau.f measurement are shown in FIG. 8 and Table 5 below.

TABLE-US-00004 TABLE 4 Relative Relative Relative Relative Relative Molar ratio permittivity permittivity permittivity permittivity permittivi- ty c of CaTiO.sub.3 .epsilon.r at 1250.degree. C. .epsilon.r at 1300.degree. C. .epsilon.r at 1350.degree. C. .epsilon.r at 1400.degree. C. .epsilon.r at 1450.degree. C. 0.00 17.80 17.90 18.16 18.24 18.17 0.05 19.80 19.94 20.08 20.51 20.47 0.07 21.22 21.45 21.70 21.98 22.02 0.09 22.82 22.98 23.27 23.52 23.41

TABLE-US-00005 TABLE 5 Molar ratio c Temperature coefficient of CaTiO.sub.3 .tau.f at 1300.degree. C. (ppm/K) 0.00 -57.6 0.05 -8.6 0.07 18.7 0.09 48.3

As is clear from FIG. 8 and Table 5 above, it is found that the temperature coefficient .tau.f gradually varies in proportion as the CaTiO.sub.3 content increases. When the molar ratio c of CaTiO.sub.3 is around 0.06, the temperature coefficient .tau.f becomes substantially zero, and shifts to the minus side when the ratio is smaller than 0.06 and to the plus side when the ratio is larger than 006. On the other hand, the relative permittivity .epsilon.r does not vary so much even when the CaTiO.sub.3 content varies, as shown in FIG. 7 and Table 4 above. This means that controlling the CaTiO.sub.3 content enables the temperature coefficient if to be independently controlled. Particularly when the molar ratio c of CaTiO.sub.3 is set to be in the range of 0.03 to 0.08, the temperature coefficient .tau.f can be controlled in the range of .+-.30 ppm/K.

The relative density of each sample produced was also measured. The results of measurement are shown in FIG. 9 and Table 6 below. As is clear from FIG. 9 and Table 6, the relative density shows a level not giving rise to any problem when the temperature is 1250.degree. C. or more. Therefore, when CaTiO.sub.3 is used to control the temperature coefficient .tau.f, it can be said that the calcining temperature is preferably set to be 1250.degree. C. or more.

TABLE-US-00006 TABLE 6 Relative Relative Relative Relative Relative density density density density density Molar ratio (%) at (%) at (%) at (%) at (%) at c of CaTiO.sub.3 1250.degree. C. 1300.degree. C. 1350.degree. C. 1400.degree. C. 1450.degree. C. 0.00 97.0 97.5 98.4 99.0 98.7 0.05 95.6 96.4 96.8 98.1 98.2 0.07 96.2 96.8 97.7 98.8 99.1 0.09 96.8 97.9 98.3 99.2 99.1

In accordance with the process of producing the dielectric porcelain composition samples, samples each comprising MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3 were produced.

FIG. 10 shows measurement results of a sample of 0.2275MgTiO.sub.3-0.6825Mg.sub.2SiO.sub.4-0.09CaTiO.sub.3, wherein a=0.2275, b=0.6825 and c=0.09, measured using an X-ray diffraction apparatus. It can be observed from the X-ray diffraction chart that there exist peaks resulting respectively from MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3, from which it is found that the sample comprises a mixed crystal of MgTiO.sub.3, Mg.sub.2SiO.sub.4 and CaTiO.sub.3.

In a system of MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3, various samples were prepared, with 0.05 mol of CaTiO.sub.3 fixed (c=0.05) and with the Mg.sub.2SiO.sub.4 substitution amount varied. In this case, the results of relative permittivity .epsilon.r measured are shown in FIG. 11 and Table 7 below, the results of temperature coefficient .tau.f measured in FIG. 12 and Table 8 below, and the relative density measured in FIG. 13 and Table 9 below.

TABLE-US-00007 TABLE 7 Molar Relative Relative Relative ratio b permittivity .epsilon.r at permittivity .epsilon.r at permittivity .epsilon.r at of Mg.sub.2SiO.sub.4 1300.degree. C. 1350.degree. C. 1400.degree. C. 0.0000 19.94 20.08 20.51 0.2375 15.41 15.24 14.57 0.4750 11.85 11.31 11.25 0.7125 9.46 9.42 9.43 0.9500 7.60 7.83 7.48

TABLE-US-00008 TABLE 8 Molar ratio b Temperature coefficient of Mg.sub.2SiO.sub.4 .tau.f at 1300.degree. C. (ppm/K) 0.0000 -8.6 0.2375 -21.1 0.4750 -30.5 0.7125 -40.6 0.9500 -44.7

TABLE-US-00009 TABLE 9 Molar ratio b Relative density Relative density Relative density of Mg.sub.2SiO.sub.4 (%) at 1300.degree. C. (%) at 1350.degree. C. (%) at 1400.degree. C. 0.0000 96.4 96.8 98.1 0.2375 96.9 96.7 94.7 0.4750 96.2 93.8 92.3 0.7125 97.1 96.0 95.9 0.9500 96.1 98.3 96.5

In the MgTiO.sub.3--Mg.sub.2SiO.sub.4--CaTiO.sub.3 system, various samples were produced, with MgTiO.sub.3:Mg.sub.2SiO.sub.4 fixed to 1:3 and with the CaTiO.sub.3 substitution amount varied. In this case, the results of relative permittivity .epsilon.r measured are shown in FIG. 14 and Table 10 below, the results of temperature coefficient .tau.f measured in FIG. 15 and Table 11 below, and the relative density measured in FIG. 16 and Table 12 below.

TABLE-US-00010 TABLE 10 Relative Relative Relative Molar ratio c permittivity .epsilon.r at permittivity .epsilon.r at permittivity .epsilon.r at of CaTiO.sub.3 1300.degree. C. 1350.degree. C. 1400.degree. C. 0.00 8.43 8.45 0.05 9.46 9.42 9.43 0.07 10.01 9.91 9.95 0.09 10.70 10.86 10.84

TABLE-US-00011 TABLE 11 Molar ratio c Temperature coefficient of CaTiO.sub.3 .tau.f at 1350.degree. C. (ppm/K) 0.00 -62.0 0.05 -40.6 0.07 -27.3 0.09 -2.9

TABLE-US-00012 TABLE 12 Molar ratio c Relative density Relative density Relative density of CaTiO.sub.3 (%) at 1300.degree. C. (%) at 1350.degree. C. (%) at 1400.degree. C. 0.00 95.8 96.7 0.05 97.1 96.0 95.9 0.07 96.5 95.8 95.6 0.09 95.5 97.4 96.6

As is clear from these Figures and Tables, also in the three-element system, it is possible to control the relative permittivity .epsilon.r through adjustment of the Mg.sub.2SiO.sub.4 content and control the temperature coefficient .tau.f through adjustment of the CaTiO.sub.3 content. In the composition of 0.2275MgTiO.sub.3-0.6825Mg.sub.2SiO.sub.4-0.09CaTiO.sub.3 prepared with the aim that the relative permittivity .epsilon.r=10 and that the temperature coefficient .tau.f=0, it was found that the relative permittivity .epsilon.r=10.86 and that the temperature coefficient .tau.f=-2.7 ppm/K.

In addition, upon considering the relative density of each sample produced, it was found from FIGS. 13 and 16 and Tables 9 and 12 that good results could be obtained when the calcining temperature was 1300.degree. C. or more.

As is clear from the foregoing description, according to the present invention, the relative permittivity .epsilon.r and temperature coefficient .tau.f can be controlled to enable provision of a dielectric porcelain composition with the relative permittivity .epsilon.r suitable for submillimeter-wave and millimeter-wave regions and the temperatue coefficient .tau.f controlled to a value in the vicinity of 0.

Also according to the present invention, using the dielectric porcelain composition as a dielectric material enables provision of a dielectric resonator usable in the submillimeter-wave and millimeter-wave bandwidth regions. In the dielectric resonator, since the dielectric porcelain composition exhibits appropriate relative permittivity .epsilon.r, the dimensional tolerance can be alleviated to make it easy to design a dielectric resonator when being fabricated. Furthermore, the temperature coefficient can also be controlled in compliance with the temperature coefficient of the surrounding parts and the like.

The present disclosure relates to subject matter contained in Japanese Patent Application Nos. 2003-071545, filed on Mar. 17, 2003, the contents of which are herein expressly incorporated by reference in its entirety.

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