KR20000002598A - Dielectric magnetic composition for high frequency - Google Patents

Abstract

PURPOSE: A dielectric magnetic composition for high frequency is provided to have the 40 to 50 dielectric rate with little loss, and have a good temperature coefficient of resonance frequency. CONSTITUTION: A dielectric material for high frequency is mainly composed that x is bigger or the same than 0.1 and smaller or the same than 0.5 in a composition system, which displays a formula (1-x)CaTiO6 + xYAIO6. The dielectric material hires the xYAIO6 to the CaTiO6, which the dielectric rate is high, but the temperature coefficient is so high that it is difficult to be practical.

Description

High Frequency Dielectric Magnetic Composition

The present invention relates to a dielectric ceramic composition for high frequency, which has a low loss, has a dielectric constant of 40 to 50, and has a good temperature coefficient of resonance frequency.

Recent advances in mobile communications, hypocrisy broadcasting, satellite communications, etc.

Communication systems using waves (frequency bands: 300 MHz to 300 GHz) have been remarkably developed, and ceramic dielectrics for high frequencies in resonators, bandpasses, stop filters, and microwave integrated circuits (MIC) used in the practical application of these new media. Applications are increasing significantly.

In order to use such a high frequency ceramic dielectric in a communication system,

(1) Since the wavelength of radio waves in the dielectric is inversely proportional to the half power of the dielectric constant, the dielectric constant must be large for the miniaturization of components.

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

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

Incidentally, good thermal conductivity and high mechanical strength are required.

Existing dielectric compositions include Ba (M ²⁺ _1/3 M ⁵⁺ _2/3 ) O ₃ (M ²⁺ = Mg, Zn, M ⁵⁺ = Ta, Multiple pages lobe solid solution of Sky bit structure having a dielectric constant of 20 to 30 and a high quality factor (Q x fo = 200,000), such as Nb) system, (Zr, Sn) TiO ₄ based with a dielectric constant of medium from 30 to 40, such Simple solid solution having a quality factor of (Q x fo = 50,000), and BaTi ₄ O ₉ and Ba ₂ Ti ₉ O ₂₀ system is known. In addition, the dielectric loss is relatively large (Qxf _0≤ 10000) a dielectric constant of 80 or higher BaO-Sm ₂ O ₃ -TiO _{2 based, O-Nd 2 O 3 (} Ba, Pb) -TiO 2 system, and (Pb, Ca) ZrO ₃ system and the like have been reported.

In general, materials with high dielectric constants increase the dielectric loss and the temperature coefficient of the resonance frequency due to dipoles and defects in the dielectric.

Among the known high frequency dielectric materials, CaTiO ₃ has a very high dielectric constant of about 170 to 180 at 3 GHz, but has a problem in that the temperature coefficient of the resonance frequency is very high as +800 ppm / ° C.

Accordingly, the present invention dielectric constant is high by employing the YAlO ₃ unknown dielectric property is still difficult to put to practical use and large temperature coefficient of CaTiO ₃ to improve the temperature characteristics of resonance frequency, a low-loss dielectric constant is adjusted in a range of 40 to 50 It is an object to provide a dielectric ceramic composition for high frequency where possible.

1 is a graph showing the dielectric characteristics according to the composition change of the dielectric resonator according to the present invention.

Figure 2 is a graph showing the temperature coefficient characteristics of the resonant frequency according to the composition change of the dielectric resonator according to the present invention.

The present invention relates to a high frequency dielectric material having a distorted perovskite structure mainly composed of CaTiO ₃ and YAlO ₃ .

CaTiO ₃ is a material having a perovskite structure and has a unit crystal of a tetragonal system of a = 5.381, b = 7.645 c = 5.443Å, and the dielectric properties are dielectric constant of 170 or higher, temperature coefficient of 800ppm / ℃ or higher, Q × f _o is less than 10000 The YAlO ₃ are a = 5.179, b = 5.329 c = Fe lobes yet as the material of the high-frequency dielectric characteristics Perovskite - Type-like structure having a unit of information GdFeO ₃ of 7.370Å Although there is no been reported findings of the present inventors dielectric constant is approximately 13 It is a material with a negative temperature coefficient. In general, materials having CaTiO ₃ and perovskite-like structures having a perovskite-like structure form a solid solution, and when these materials are substituted with CaTiO ₃ to form a solid solution, distorted perovskite-like structures have dielectric properties, In particular, the temperature coefficient can be improved. In this study, improvement of high-frequency dielectric characteristics of the CaTiO ₃ and a dielectric constant of the addition of 13 degree, negative temperature coefficient of the YAlO ₃ CaTiO _3. These results and the addition of CaTiO ₃ to the YAlO ₃ forms a solid solution on the crimes, as the addition amount of the YAlO ₃ increases the dielectric constant is reduced, the temperature coefficient is negative it varies from the amount Q value increases.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example

To synthesize CaTiO ₃ and YAlO ₃ , CaCO ₃ (99.9%), TiO ₂ (99.9%), Y ₂ O ₃ (99.9%), and Al ₂ O ₃ (99.9%) were used. After precisely weighing up to 10 ^-4 g, zirconia balls were wet mixed for 12 hours in a medium, and the mixed samples were dried and calcined at 1100 ° C. for 3 hours. The calcined CaTiO ₃ and YAlO ₃ powder was weighed in a molar ratio so as to have the composition shown in Table 1, and wet mixed and pulverized for 20 hours, and 8% by weight of a 5% PVA aqueous solution was added as a binder 30 minutes before the completion of grinding. The pulverized powder was dried, sieved, and pressed using a mold having a diameter of 15 mm at a pressure of ¹ ton / cm ² to form a specimen having a thickness of about 6 mm. The molded specimens were sintered at 1550-1650 ° C. using a box-type electric furnace. At this time, the organic matter was maintained for 1 hour at 650 ℃ and the temperature and cooling rate was 300 ℃ / hr.

The dielectric constant was measured by the Hakki-Coleman method using the TE ₁₁ resonance mode between two sheets of on-board. Two dielectrics having the same diameter and three times the height were made to measure the surface resistance of TE ₁₁ , TE ₁₃ and the silver plate. Calculated. In addition, the temperature coefficient of the resonant frequency was obtained by measuring the change of the resonant frequency at 25 ° C and 65 ° C. Microwave dielectric properties of the specimens for each composition are shown in Table 1.

As shown in Table 1, as the amount of YAlO ₃ increases, the dielectric constant decreases, the temperature coefficient changes from positive to negative, and shows good temperature characteristics between the dielectric constants of 40 to 50. At this time, the Q × f _o value is higher than 30000. Have

High Frequency Dielectric Properties of (1-x) CaTiO ₃ + YAlO ₃ System No. x permittivity Q × f _o (GHz) T _f (ppm / ℃) One 0.1 82.33 21381 198.3 2 0.2 53.06 31683 72.9 3 0.25 47.15 35246 13.5 4 0.3 38.97 37342 -11.9 5 0.4 30.50 44469 -44.6 6 0.5 28.22 48717 -50.6 7 0.6 24.79 50865 -55.8 8 0.7 19.80 55558 -60.8 9 0.8 18.43 59462 -63.7 10 0.9 17.57 65065 -62.5 11 1.0 14.31 80477 -60.7

The dielectric ceramic composition for high frequency of the present invention has high dielectric constant, but employs YAlO ₃ in CaTiO ₃ which is difficult to be commercialized due to its high temperature coefficient, thereby improving the temperature characteristic of the resonant frequency, and controlling the dielectric constant in the range of 40 to 50 with low loss.

Claims (1)

A high frequency dielectric material having 0.1? X? 0.5 as a main component in a composition system represented by general formula (1-x) CaTiO ₃ + xYAlO ₃ .