JP2579138B2 - Microwave dielectric composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave dielectric magnetic composition having a small dielectric loss and a good temperature coefficient of resonance frequency.

[0002]

2. Description of the Related Art Recently, a frequency band of 300 MHz has been used for mobile communications, such as radio telephones and automobile telephones, satellite broadcasting, and satellite communications.
Communication systems using microwaves of up to 300 GHz have been remarkably developed. For the practical use of such new media, applications of dielectric ceramics for microwaves to resonators, band-pass (or blocking) filters, microwave integrated circuits (MICs), and the like have been greatly increased. When this microwave dielectric is applied to a communication system, (1) the wavelength of the microwave in the dielectric is inversely proportional to the 乗 power of the dielectric constant. (2) Since the dielectric loss increases in proportion to the frequency, the Q value (that is, the reciprocal of the dielectric loss) must be large for high performance, and (3) the dielectric resonator The temperature coefficient of the resonant frequency must be low [Werthing Electronic Ceramics (BCH Stee
le), 67 pages, New York, USA
Elsevier Sci, Pub, Co, (1991)]. The microwave dielectric used in the communication system must have a small change with time, a high thermal conductivity, and a good mechanical strength. As the dielectrics developed so far, B
a (M ⁺² _1/3 M ⁺⁵ _2/3 ) O ₃ (M ⁺² = Mg, Zn, M ⁺⁵
= Ta, Nb), Ba ₂ Ti ₉ O ₂₀ and (Zr, S
n) TiO ₄ system can be mentioned. This type of dielectric has a dielectric constant of 40 or less, but has a low dielectric loss. As another example, BaO—Sm ₂ O ₃ —TiO ₂ system,
(Ba, Pb) O—Nd ₂ O ₃ —TiO ₂ and (P
b, Ca) ZrO ₃ system, but the dielectric loss of this dielectric is relatively large (Qxfo (GHz) <1
000) is known to have a dielectric constant of 80 or more [the above-mentioned Worthing reference; and J. Kato, JEE, Sep., 11].
4-118 (1991)].

[0003]

Generally, a material having a large dielectric constant has an increase in dielectric loss and a temperature coefficient of a resonance frequency due to a defect of a dipole inside the dielectric. Temperature coefficient of frequency is preferentially ± 10ppm / ℃
If it is not stable enough, it cannot be applied. (S
In the case of (r, Ca) TiO ₃ , the dielectric constant at 2 GHz is 255
It is very high at about 170, but the temperature coefficient of the resonance frequency is +
Since it is 1670 to +800 ppm / ° C., there is a very large problem in practical use. On the other hand, Nd (Mg _1/2 Ti _1/2 ) O
_In the case of ₃ , the dielectric constant is as low as about 24, but Qxfo (GH
z) is as high as about 65000, and the temperature coefficient of the resonance frequency is about -53 ppm / ° C. Therefore, an object of the present invention is to provide a microwave dielectric composition having a small dielectric loss while having a large dielectric constant of 30 or more. Another object of the present invention is to set the temperature coefficient of the resonance frequency to 0 pp.
An object of the present invention is to provide a microwave dielectric composition that can be easily adjusted in the + or-direction around m / C as needed.

[0004]

The above objects of the present invention can be attained by providing a dielectric magnetic composition for microwaves represented by the following composition formula. _{(1-y) (Sr 1} -x Ca x) TiO 3 · yNd (Mg
_1/2 Ti _1/2 ) O _{3 In the} formula, 0.01 ≦ x ≦ 1.0 and 0.3 ≦ y ≦ 0.6. The dielectric magnetic composition according to the present invention comprises, for example, SrC
It can be prepared by using O ₃ , CaCO ₃ , Nd ₂ O ₃ , TiO ₂ and MgO as starting materials and treating in a usual manner known in the art. Specifically, SrCO ₃ , CaCO ₃ , Nd ₂ O ₃ , TiO ₂
And a powder obtained by mixing MgO at a predetermined composition ratio is calcined in the air, for example, at a temperature of 1,050 ° C. for about 10 hours, and then pulverized, and further at 1,200 to 1,300 ° C. for a sufficient time,
For example, the solution is calcined again for 6 hours to synthesize a solid solution having a perovskite structure. After this synthetic powder is pulverized well, it is pressed into a disk-shaped specimen having a diameter of, for example, 10 mm and a thickness of 1 to 2 mm, and is heated in air at a temperature of, for example, 1,500 to 1,650 ° C. for 2 hours to 6 hours. It can be manufactured by sintering for a time. At this time, the sintering temperature increases as the content of MgO increases. After the sintering, the shrinkage of the specimen is 12 to 20%.

The dielectric properties of the sintered specimen, such as the dielectric constant, Q value, and temperature counting of the resonance frequency, can be measured by a known dielectric resonance technique.

[0006]

The dielectric magnetic composition for microwaves according to the present invention has a dielectric constant of about 30 to 60 and a Qxfo (GHz) of about 9.5.
00 to 50,000, temperature coefficient of resonance frequency (TCF)
Is about −60 to +60 ppm / ° C., and can be used in a form suitable for a communication system required by dielectric ceramics for microwaves as described above. Incidentally, the dielectric magnetic composition for microwaves of the present invention comprises SrTiO ₃ , CaTiO ₃ and Nd.
This is a perovskite-type solid solution containing (Mg _1/2 Ti _1/2 ) O ₃ as a main component, and the composition range of each component is as shown in a sample composition example in Table 1 below. A dielectric composition having a composition in such a range has a temperature coefficient of resonance frequency of about ± 60 ppm /
Since the temperature is ° C, microwave dielectric magnetism having small dielectric loss and good temperature characteristics can be obtained as it is or by adding a small amount of an additive.

The characteristics of the dielectric magnetic composition of the present invention are as follows: Sr
It changes greatly depending on the amount of TiO ₃ and CaTiO ₃ .
As the content of SrTiO ₃ and CaTiO ₃ increases, the dielectric constant gradually increases in the range of 30 to 60, but Qxf
o (GHz) is greatly reduced, and the temperature coefficient of the resonance frequency is
As shown in FIG. In particular, Sr
When the content of TiO ₃ and CaTiO ₃ is around 0.4 to 0.5 mol, the dielectric constant is 41 to 48, Qxfo (GHz) is 30,
An excellent dielectric magnetism for microwaves having a temperature coefficient of the resonance frequency of not less than 000 and not more than 10 ppm / ° C. can be manufactured. On the other hand, by adjusting the contents of SrTiO ₃ and CaTiO _{3 in} a small amount, the temperature coefficient of the resonance frequency can be freely controlled to be + or − around 0 ppm / ° C. under the same manufacturing conditions.

[0008]

The present invention will be described below in more detail with reference to examples. However, the present invention is not limited by this embodiment. 99.9% pure SrCO ₃ , CaCO ₃ ,
Nd ₂ O ₃ , TiO ₂ and MgO were accurately weighed so as to have the compositions shown in Table 1 below, and then mixed together. The mixed powder was calcined at 1,050 ° C. in the air for about 10 hours and then pulverized, and further calcined at 1,200 to 1,300 ° C. for 6 hours to synthesize a solid solution having a perovskite structure. After crushing the synthetic powder well, the diameter is 10mm, thickness is 1 ~
It is press-formed into a 2 mm disk-shaped specimen,
Sintered at １，1,650 ° C. for 2 to 6 hours. After sintering, the specimen shrunk by about 12 to 20%. After the both sides of the sintered specimen were polished well with abrasive paper (up to # 3000), they were placed in a waveguide, and the dielectric constant, the Q value, and the temperature coefficient of the resonance frequency were measured by a dielectric resonance technique. At this time, the measurement frequency was 8 to 12 GHz, and the measurement temperature range was -15 to 85 ° C. Table 1 shows the microwave dielectric properties of each specimen.

[0009]

[Table 1]

As shown in Table 1, the dielectric properties are Nd (M
g _1/2 Ti _1/2 ) O ₃ , there is no significant change, but the amount greatly changes depending on the amounts of SrTiO ₃ and CaTiO ₃ . That is, according to the content of SrTiO ₃ and CaTiO ₃ is increased, whereas the dielectric constant is gradually increased in the range of 30~60, Qxfo (GHz) is greatly reduced, the temperature coefficient of resonant frequency - progressively from + It can be seen that it changes.

[0011]

According to the present invention, SrTiO ₃ , CaT
The temperature coefficient of the resonant frequency of a dielectric magnetic composition for microwaves composed of a perovskite-type solid solution containing iO ₃ and Nd (Mg _1/2 Ti _1/2 ) O ₃ as main components is smaller than that of a conventional dielectric magnetic composition. Unlike this, it is ± 60 ppm / ° C., and by itself or by adding a small amount of an additive, it is possible to form a microwave dielectric magnet having small dielectric loss and excellent temperature characteristics.

[Brief description of the drawings]

FIG. 1 is a graph showing a temperature coefficient characteristic of a resonance frequency according to a composition change of a dielectric resonator according to the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yun Sin Jin 203, 810, Janggyeong-dong, Sewon-dong, Awon-gu, Seoul, Republic of Korea (72) Inventor Tetsuro Nakamura Fujiga, Midori-ku, Yokohama-shi, Kanagawa Oka 2-41-21 Fujigaoka Dormitory 403 (72) Inventor Mitsuru Mitsuru 33-7 Sakuradai, Midori-ku, Yokohama-shi, Kanagawa Prefecture 1-11 Sakuradai Court Village 1-11 (72) Inventor Masaho Son 1 Daepo 1-dong, Daegu, Republic of Korea 187 No. 6 (56) References JP-A-8-217535 (JP, A) JP-A-4-118807 (JP, A) JP-A-63-138605 (JP, A)

Claims (1)

(57) [Claims] 1. A microwave dielectric composition represented by the following composition formula: _{(1-y) (Sr 1} -x Ca x) TiO 3 · yNd (Mg
_1/2 Ti _1/2 ) O _{3 In the} formula, 0.01 ≦ x ≦ 1.0 and 0.3 ≦ y ≦ 0.6.