KR100356641B1 - Dielectric Ceramic Compositions for High Frequency - Google Patents

Abstract

The present invention is represented by the composition formula (1-x) (Al _1/2 Ta _1/2 ) O ₂ -x (Mg _1/3 Ta _2/3 ) O ₂ , where x is in a range of 0 ≦ x ≦ 1. It provides a dielectric composition for. The composition has a dielectric constant of 8.7 to 27.1, Qxf _O (GHz) of 6500 to 111230, and a temperature coefficient of resonant frequency (τ _f ) in the range of -55.2 to +51.2 ppm / ° C, where τ _f is changed according to the composition change. It is a high frequency dielectric composition having excellent characteristics that can be adjusted to 0 ppm / ℃ and can be used as a material of high frequency dielectric ceramic components.

Description

Dielectric Ceramic Compositions for High Frequency

The present invention relates to a high frequency dielectric ceramic composition having a high quality factor (Q value) and a dielectric constant and an excellent temperature coefficient of resonance frequency.

Recently, a communication system using microwaves having a frequency band of 300 MHz to 300 GHz for mobile communication, satellite broadcasting, and satellite communication of wireless telephones and automobile telephones has been remarkably developed, and for the practical use of such new media, resonators and band pass ( Or the application of high frequency dielectric ceramics to a filter, a duplexer, a microwave integrated circuit (MIC), and the like, has been greatly increased.

In order for the high frequency dielectric to be used in a communication system, the wavelength of the microwave in the dielectric is inversely proportional to half the square of the permittivity and the frequency, so the dielectric constant and the use frequency must be large for the miniaturization of components. In general, the dielectric constant ε _r and the value of the quality factor Q (proportional to the inverse of the dielectric loss) are inversely related, and at a high frequency of 1 to 2 GHz or higher, a dielectric material having a large quality factor (relatively low dielectric constant) is required. It is becoming. In addition, as mentioned above, as the frequency of use increases, the size of the component is sufficiently small, and dielectric materials in the dielectric constant region of 90 region are used for cellular filters in the 800 MHz band and 38 regions in the dielectric constant of PCS filters in the 1.9 GHz band. In the future, as frequencies such as WLL and IMT 2000 become more high frequency, materials with a dielectric constant of 20 will be used, and are currently actively used in various resonators.

In general, high dielectric constant materials increase the dielectric loss and the temperature coefficient of the resonant frequency, but high frequency dielectrics have to stabilize the temperature coefficient of the resonant frequency in order to be applicable.

Representative dielectric materials in the region of dielectric constant 20 developed so far include the MgTiO ₃ -CaTiO ₃ system, which has a Q value of 8000 (at 7 GHz), a dielectric constant of 21 and a temperature coefficient of resonant frequency of zero. ppm / ° C. (K. Wakino, Ferroelectrics, 91, 69 (1989)). This Q f _o value (56000 GHz) has no problem in application to components, but larger Q values are required to improve frequency selectivity.

Accordingly, it is an object of the present invention to provide a high frequency dielectric composition having a dielectric constant of 20 regions and a low dielectric loss, that is, a large quality factor Q.

Another object of the present invention to provide a dielectric composition for high frequency that can adjust the temperature coefficient of the resonance frequency.

The object of the present invention as described above is achieved by providing a dielectric ceramic composition having the following compositional formula.

(1-x) (Al _1/2 Ta _1/2 ) O ₂ -x (Mg _1/3 Ta _2/3 ) O ₂

Wherein x is in the range 0 ≦ x ≦ 1.

The dielectric composition according to the present invention has a dielectric constant of 8.7 to 27.1, Qxf _O (GHz) of 6500 to 111230, and the temperature coefficient (TCF) of the resonance frequency is -55.2 to +51.2 ppm / ° C according to the composition change. The TCF can be adjusted to 0 ppm / ° C and can be used as a material used as a component of high-frequency dielectric ceramics.

The dielectric ceramic composition of the present invention has a temperature coefficient of (Al _1/2 Ta _1/2 ) O ₂ having a temperature coefficient of negative (-55.2 ppm / ° C.) and a positive (+51.2 ppm / ° C.) temperature coefficient. A solid solution in which (Mg _1/3 Ta _2/3 ) O ₂ having a solid solution is employed, and its properties are (Al _1/2 Ta _1/2 ) O ₂ and (Mg _1/3 Ta _2/3 ) O _It changes with the composition ratio of ₂ and sintering temperature. (Al _1/2 Ta _1/2 ) O ₂ has a dielectric constant of 8.7 when the sintering temperature is 1600 ° C., Qxf _O (GHz) of 60830, and a temperature coefficient of resonant frequency of −55.2 ppm / ° C. Further, (Mg _1/3 Ta _2/3 ) O ₂ has a dielectric constant of 27.1 when the sintering temperature is 1500 ° C., Qxf _O (GHz) is 95360, and a temperature coefficient of the resonance frequency is +51.2 ppm / ° C. Therefore, when the two compositions are employed, excellent microwave dielectric properties can be obtained at a high sintering temperature in a region in which (Al _1/2 Ta _1/2 ) O ₂ is high and (Mg _1/3 Ta _2/3 ) O ₂ In highly employed regions, good microwave dielectric properties can be obtained at relatively low sintering temperatures. Also, as the content of (Mg _1/3 Ta _2/3 ) O ₂ with relatively high permittivity and temperature coefficient of positive resonant frequency increases, the temperature coefficient of dielectric constant and resonant frequency increases at all sintering temperatures. do. In particular, when the content of (Mg _1/3 Ta _2/3 ) O ₂ is 0.65 mol, excellent dielectric constant is 26.1, Qxf _O is 94470 GHz, and the temperature coefficient of resonant frequency is 0 ppm / ℃ when sintered at 1450 ℃ for 3 hours. Microwave dielectric ceramics can be produced.

The dielectric ceramic composition according to the present invention can be produced by a generally known ceramic manufacturing process using, for example, Al ₂ O ₃ , MgO and Ta ₂ O ₅ as starting materials. More specifically, in the ceramic dielectric composition according to the present invention, Al ₂ O ₃ , MgO and Ta ₂ O ₅ 1100 ~ 1100 to a powder in which these samples were mixed at a constant composition ratio after drying for about 10 hours at a temperature of 600 ℃ before use After calcining and pulverizing at a temperature of 1300 ° C. for 2 to 4 hours, 5 wt% of a 5% PVA aqueous solution was added as a molding additive, and pressure-molded into a cylindrical specimen having a diameter of 10 mm and a thickness of 5 to 6 mm, followed by 600 ° C. After removing the organic binder by heat treatment for 1 hour at a temperature, it can be prepared by sintering for 1 to 5 hours at a temperature of 1400 ~ 1600 ℃.

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

Hereinafter, the present invention will be described in more detail with examples. However, the present invention is not limited only by the examples.

<Example>

Al ₂ O ₃ and MgO with 99% purity and Ta ₂ O ₅ with 99% were dried at a temperature of 600 ° C. for 10 hours before use, and these samples were mixed at the composition ratios shown in Table 1, and the mixed powder was mixed in the air. It was calcined by calcination at a temperature of 1200 ° C. for about 4 hours. Subsequently, 5 wt% of a 5% PVA aqueous solution was added as a molding additive and pressure molded into a cylindrical specimen having a diameter of 10 mm and a thickness of 5 to 6 mm. In order to remove the organic binder, the molded specimens were heat treated at a temperature of 600 ° C. for 1 hour, and then sintered for 3 hours at a temperature of 1400 to 1600 ° C. in air.

Both surfaces of the sintered specimens were polished well using a SiC paper, and then placed in a waveguide, and the dielectric constant, Q value, and temperature coefficient of the resonance frequency were measured by the dielectric resonant technique. At this time, the measurement frequency was 8.3 to 13.3 GHz, and the measurement temperature range was -15 to 85 ℃. The microwave dielectric properties of each specimen are shown in Table 1.

High Frequency Dielectric Properties of (1-x) (Al _1/2 Ta _1/2 ) O ₂ -x (Mg _1/3 Ta _2/3 ) O ₂ Sample Number Composition (mol) x Sintering Temperature (℃) Permittivity (ε _γ ) Qxf _o (GHz) τ _f (ppm / ℃) One 0.2 1400 10.6 6500 2 0.4 18.8 18270 3 0.6 23.8 52450 4 0.65 25.0 83740 5 0.8 26.2 104200 6 1.0 25.1 18110 7 0.2 1450 14.2 62150 -40.5 8 0.4 22.1 90930 -16.1 9 0.6 25.8 111230 -5.0 10 0.65 26.1 94470 0 11 0.8 26.5 103190 25.3 12 0 1500 10.7 27170 13 0.2 15.8 92810 14 0.4 24.0 76850 15 0.6 24.9 54060 16 0.65 25.2 44860 17 0.8 25.8 105200 18 1.0 27.1 95360 +51.2 19 0.2 1550 15.7 103560 20 0.4 22.1 39960 21 0.6 22.5 36060 22 0.65 23.6 43260 23 0.8 23.9 57790 24 0 1600 8.7 60830 -55.2 25 0.2 14.8 35910 26 0.4 21.6 60630 27 0.6 21.2 44520 28 0.65 22.6 55430 29 0.8 22.7 71920

According to the present invention, it is possible to provide an excellent high frequency dielectric composition having a dielectric constant of 20 regions, a low dielectric loss, a large quality factor and a temperature coefficient of resonance frequency.

Claims (1)

A dielectric composition for high frequency represented by the following formula. (1-x) (Al _1/2 Ta _1/2 ) O ₂ -x (Mg _1/3 Ta _2/3 ) O ₂ Wherein x is in the range 0 ≦ x ≦ 1.