KR19980014910A - Dielectric material for CaTiO3-La (Zn1 / 2Ti1 / 2) O3-LaA103 microwave - Google Patents

Abstract

The present invention relates to a dielectric material for a microwave of CaTiO ₃ -La (Zn _1/2 Ti _1/2 ) O ₃ -LaA 10 ₃ system. The microwave dielectric material of the present invention is a material for a microwave, which is represented by the general formula (1-x) CaTiO ₃ -x [(1-y) La (Zn _1/2 Ti _1/2 ) O ₃ -yLaA 10 ₃ ] 0.3? X? 0.6 and 0? Y? 1.0 in a composition system. The dielectric material for high frequency use of the present invention has a dielectric constant of at least 48 in the vicinity of a composition having a temperature coefficient of 10 ppm / 占 폚, has a small dielectric loss, and can easily be moved to positive and negative sides with a temperature coefficient of 0 ppm / .

[Table 1]

Description

Dielectric material for CaTiO3-La (Zn1 / 2Ti1 / 2) O3-LaA103 microwave

FIG. 1 is a CaTiO ₃ -La (Zn _1/2 Ti _1/2 ) O ₃ -LaAl ₃ O ₃ system showing the composition range of the dielectric material of the present invention.

FIG. 2 is a graph showing the temperature coefficient characteristic of the resonance frequency according to the compositional change of the dielectric resonator according to the present invention. FIG.

The present invention relates to a micro-waveguide dielectric material having a low loss of a CaTiO ₃ -La (Zn _1/2 Ti _1/2 ) O ₃ -LaA 10 ₃ system and having a temperature coefficient of a resonant frequency.

Recently, communication systems using microwaves (frequency band: 300 MHz to 300 GHz) have been remarkably developed in satellite communications including mobile communication and satellite broadcasts such as radio transceivers and automobile telephones, and resonator elements, bandpass Application of high frequency dielectric ceramics to a microwave integrated circuit (MIC) and the like has been greatly increased.

A high-frequency dielectric used in a communication system using microwaves is a high-

1) Since the wavelength of the microwave in the dielectric is inversely proportional to 1/2 of the dielectric constant, the dielectric constant must be large for miniaturization of the component,

2) Since the dielectric loss increases in proportion to the frequency, the Q value (reciprocal of dielectric loss) must be high for high performance,

3) The temperature coefficient of the resonant frequency of the dielectric resonator should be small,

Incidentally, it is required that the change with time is small, the thermal conductivity is high, and the mechanical strength is high.

As typical dielectric materials for microwave, dielectric materials such as Ba (Mg _1/3 Ta _2/3 ) O ₃ have a dielectric constant of 20 to 30 and a composite perovskite having a high quality factor (Q × f ₀ = 200,000) (Ba, Pb) O-Nd ₂ O, which has a moderate quality factor (Q × f ₀ = 500,000) with a dielectric constant of 30 to 40, such as (Zr, Sn) TiO ₄ , ₃ -TiO ₂ with a relatively high quality factor (Q × f ₀ = 6,000) and a dielectric constant as high as 90 to 100, and the known data related to this is classified by dielectric constant as follows.

First, a dielectric material having a dielectric loss of 40 or less, but having a low dielectric loss,

Lt; / RTI >

In addition, the dielectric loss is relatively keuna _{(Qx (X), x (} 0) f 0 (GHz) 10000), the dielectric constant is 80 or higher,

Are known.

In general, the dielectric constant and the resonant frequency temperature coefficient of a material having a large dielectric constant increase due to defects such as a dipole inside the dielectric. In addition, the high-frequency dielectric material can be applied to the case where the temperature coefficient of the resonance frequency is stabilized to about ± 10 ppm / ° C.

However, in the case of CaTiO _3, and a very large dielectric constant problems in the 170 ~ 180 very high, but the number of the temperature coefficient of resonant frequency + 800ppm / ℃ so at _{3GHz, La (Zn 1/2 Ti 1/2} ) O _3, the dielectric constant for the (Q × f ₀ GHz) is as high as 60,000, and the temperature coefficient of the resonance frequency is about -60 ppm / ° C. In the case of LaA10 _3, the dielectric constant of around 26-27, the temperature coefficient is on the order of about -90ppm / ℃.

Therefore, the present invention utilizes the advantages of each of the CaTiO ₃ , La (Zn _1/2 Ti _1/2 ) O ₃ and LaA10 ₃ -based materials, and improves the problems, thereby permitting the dielectric constant to be 40 or more, And the temperature coefficient of the frequency can be easily shifted to + and - around 0 ppm / DEG C as needed.

The ceramic composition of the microwave dielectric of the present invention is a perovskite type solid solution containing CaTiO ₃ , La (Zn _1/2 Ti _1/2 ) O ₃ and LaA10 ₃ as main components, As shown in the state diagram.

The reason for limiting the above range is that the temperature coefficient of the dielectric resonance frequency of these compositions is about +80 to -50 ppm / 占 폚, so that by itself or by adding a small amount of additives, dielectric porcelain for microwaves, Because it can be manufactured.

Various characteristics and detailed manufacturing processes of the dielectric material for microwave of the present invention will be more clearly understood through the following examples.

Example

CaCO ₃ , La ₂ O ₃ , Al ₂ O ₃ , TiO ₂ and ZnO having a purity of 99.9% were used as raw materials, and the raw materials were precisely weighed so as to have the compositions shown in the following Table 1, and then mixed with each other. The mixed powders were calcined at 1,250 ℃ for 4 hours in the atmosphere, and then solid solutions having a perovskite structure were prepared.

The prepared powders were pulverized well and pressed with a disk type specimen having a diameter of 15 mm and a thickness of 6 to 7 mm and sintered at 1,450 ~ 1,550 ℃ for 2 ~ 6 hours. At this time, the shrinkage of the specimen after sintering was about 15 ~ 20%.

Sintered specimens were polished on both sides with abrasive paper (up to # 3000), placed in a waveguide, and dielectric constant, Q value and temperature coefficient of resonance frequency were measured by dielectric resonance method. The measurement frequency was 4 ~ 6GHz and the measurement temperature range was -30 ~ 80 ℃. The microwave dielectric properties of the specimens for each composition are shown in Table 1.

As shown in Table 1, depending on the amounts of La (Zn _1/2 Ti _1/2 ) O ₃ and LaA10 ₃ , there is no significant change in the high-frequency dielectric characteristics, but the characteristics are largely changed depending on the amount of CaTiO ₃ . As the content of CaTiO ₃ increases, the dielectric constant gradually increases in the range of 35 to 60, but Q _{x (x)} and x _(O) f _O (GHZ) And is gradually changing from - to +. Therefore, it is possible to manufacture a dielectric material for microwave having a dielectric constant of 45 to 55, a Q × fo (GHz) of 45,000 or more at a CaTiO ₃ content of about 0.45 to 0.55 mol and a temperature coefficient of resonance frequency of ± 10 ppm / ° C or less. On the other hand, by controlling the content of CaTiO _{3 in} a small amount, the temperature coefficient of the resonance frequency can be freely controlled to + and - around 0 ppm / ° C under the same manufacturing conditions.

Claims (1)

In the composition system represented by the general formula (1-x) CaTiO ₃ -x [(1-y) La (Zn _1/2 Ti _1/2 ) O ₃ -yLaA 10 ₃ ], 0.3 ≦ x ≦ 0.6 and 0 ≦ y ≦ 1.0 And the dielectric material for microwave.