KR20040078525A - Dielectric Ceramic Compositions for High Frequency Applications - Google Patents

Abstract

PURPOSE: Provided is a microwave dielectric ceramic composition of the Ba(Zn1/3Nb2/3)O3-Ba(Co1/3Nb2/3)O3-Ba(Ni1/3Nb2/3)O3-BaWO4 system having a high dielectric constant, large Q value and low temperature coefficient of resonant frequency. CONSTITUTION: The dielectric ceramic composition for producing dielectric resonator or filter for microwave application is expressed by a composition formula of Ba(Zn1/3Nb2/3)O3-Ba(Co1/3Nb2/3)O3-Ba(Ni1/3Nb2/3)O3-BaWO4, wherein x, y and z are in the ranges of 0<=x<=0.9 mole, 0<=y<=0.9 mole and 0<=z<=0.3 mole. BaWO4 for high quality factor and low temperature sintering, and Ba(Co1/3Nb2/3)O3 and/or Ba(Ni1/3Nb2/3)O3 for low temperature coefficient of resonant frequency are added to Ba(Zn1/3Nb2/3)O3, dielectric ceramic composition. The resultant composition has 30-40 of dielectric constant, more than 55,000 of Q value and controllable temperature coefficient of resonant frequency of -10 to 20.

Description

Dielectric Ceramic Compositions for High Frequency Applications

The present invention relates to a dielectric ceramic composition for high frequency, and in particular, Ba (Zn _1/3 Nb _2/3 ) O ₃ -Ba (Co _1/3 Nb) exhibiting low loss as a high frequency dielectric material used in mobile and satellite communication base station filters. _2/3 ) O ₃ -Ba (Ni _1/3 Nb _2/3 ) O ₃ -BaWO ₄ -based high frequency dielectric ceramic composition.

The high frequency dielectric is an essential component material of frequency resonators used in wireless telephones, duplexers and band pass filters in mobile communication terminals, wireless LANs, and satellite broadcasting. However, in order to manufacture a component with a high frequency dielectric, development of a dielectric having a high quality factor (Q) value, a dielectric constant and a temperature coefficient close to zero (0) is required.

Representative dielectric materials with high quality factor (Q) are complex perovskite structures such as Ba (Mg _1/3 Ta _2/3 ) O ₃ and Ba (Zn _1/3 Ta _2/3 ) O ₃ There are dielectrics with The Ba (Mg _1/3 Ta _2/3 ) O ₃ and Ba (Zn _1/3 Ta _2/3 ) O ₃ show high values of quality factor × resonant frequency (Q × f) of 100,000 GHz or more, but permittivity As low as 25 and 30, the manufacturing process is complicated, and the raw material of Ta ₂ O ₅ is expensive, there is a difficulty in manufacturing the actual product.

Other low-loss materials having a dielectric constant of 30 or more include La (or Nd) AlO ₃ -Ca (or Sr) TiO ₂ , (Ba, Sr) (Zn _1/3 Nb _2/3 ) O ₃ , (Zr, Sn) TiO ₄ , Ba ₂ Ti ₉ O ₂₀ and the like, but these materials have a high dielectric constant, while the sintering temperature is higher than 1400 ℃, Q x f is less than 50,000GHz low.

In particular, Korean Patent Laid-Open Publication No. 1998-52343 discloses a solid solution composition of Ba (Ni _1/3 Nb _2/3 ) O ₃ and Ba (Zn _1/3 Nb _2/3 ) O ₃ having a composite perovskite structure. Ba [(Ni _1-x Zn _x ) _1/3 Nb _2/3 } O ₃ (where x is a constant ranging from 0.1 to 0.9) is proposed.

The composition has a dielectric constant of 30 or more, Q x f of 45,000 GHz or more, the temperature coefficient of the resonance frequency is to be adjustable in a wide range from -11 to 36 ppm / ℃ range, the sintering temperature is 1,500 ~ 1,550 ℃ range When the high temperature sintering furnace and the temperature coefficient is within ± 10ppm / ℃ there is a problem that the Q x f is less than 50,000GHz, there is a relatively large temperature problem.

Moreover, conventionally, a technique for reducing the firing temperature to 1,300 ° C. by adding Sb ₂ O ₅ and B ₂ O ₅ for the purpose of reducing the firing temperature in the composition has been proposed in Korean Patent No. 0783329, in which case Q × There was a problem with f as low as 40,000 GHz.

In general, since the dielectric loss tanδ is inversely proportional to the quality factor Q, the conventional composition having the low quality factor as described above has a problem in that the loss of the dielectric resonator manufactured using the same is large.

Therefore, the present invention has been made in view of the problems of the prior art, the object of which is a high frequency having a dielectric constant of 30 or more, Q x f of 55,000 GHz or more, and preferably a resonant frequency temperature coefficient within the range of ± 10ppm / ℃ As a dielectric ceramic composition, there is provided a high efficiency low loss high frequency dielectric ceramic composition which can be used directly as a dielectric material of a dielectric resonator filter for a mobile / satellite communication base station.

In order to achieve the above object, the present invention is a general formula (1-xyz) Ba (Zn _1/3 Nb _2/3 ) O ₃ -xBa (Co _1/3 Nb _2/3 ) O ₃ -yBa (Ni _{1 / 3} Nb _2/3 ) O ₃ -zBaWO ₄ , wherein the mole fractions x, y, and z range from 0 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.9, and 0 <z ≦ 0.3, respectively. A dielectric ceramic composition is provided.

In general, Ba (Zn _1/3 Nb _2/3 ) O ₃ having a composite perovskite structure is known to have a (Q × f) value of 54,000 GHz, a dielectric constant of 41, and a temperature coefficient of resonance frequency of +30 ppm / ° C. (See Jpn. J. Appl. Phys., Vol. 21, No. 12, (1982) 1707-1710). The conventional dielectric material has a high temperature coefficient of resonant frequency of about +30 ppm / 占 폚, which makes it difficult to use a dielectric resonator, a dielectric filter, a dielectric duplexer, and the like.

Therefore, in the present invention, Ba (Zn _1/3 Nb _2/3) O realize low-temperature sintering as a _{Ba (Zn 1/3 Nb 2/3) O} 3 in order to increase the utilization efficiency of the _third addition of BaWO ₄ and increase the quality factor By adding Ba (Co _1/3 Nb _2/3 ) O ₃ and / or Ba (Ni _1/3 Nb _2/3 ) O ₃ , the temperature coefficient of the resonance frequency can be lowered.

The addition of BaWO ₄ to the Ba (Zn _1/3 Nb _2/3 ) O ₃ lowers the sintering temperature to about 1,400 ° C., greatly improves the quality factor and at the same time serves to slightly lower the temperature coefficient of the resonance frequency. The addition amount z of BaWO ₄ is preferably in the range of 0 <z ≦ 0.3, and when the addition amount z exceeds 0.3, the Q × f value is rather decreased, and Q × f is particularly preferably within the temperature coefficient range of the resonance frequency. And the dielectric constant will appear below the expected expectations.

Further, in the (Ba (Zn _1/3 Nb _2/3 ) O ₃ + BaWO ₄ ) ceramic composition, Ba (Co _1/3 Nb _2/3 ) O ₃ and / or Ba (Ni _1/3 Nb _2/3 The addition of) O ₃ can significantly reduce the temperature coefficient of the resonance frequency.

First, the addition amount (x) of Ba (Co _1/3 Nb _2/3 ) O ₃ is preferably in the range of 0 ≦ x ≦ 0.9, and when the addition amount (x) exceeds 0.9, the quality factor and permittivity may be less than the expected expectations. Will appear. In this case, the preferable addition amount x of Ba (Co _1/3 Nb _2/3 ) O ₃ , which is represented by a temperature coefficient of the resonant frequency in the range of ± 10 ppm / ° C., is in the range of 0.3 ≦ x ≦ 0.8.

In addition, the addition amount (x) of Ba (Ni _1/3 Nb _2/3 ) O ₃ is preferably in the range of 0 ≦ y ≦ 0.9, and when the addition amount (y) exceeds 0.9, the quality factor and permittivity may be less than the expected expectations. Will appear. In this case, the preferable addition amount y of Ba (Ni _1/3 Nb _2/3 ) O ₃ represented by the temperature coefficient of the resonance frequency in the range of ± 10 ppm / ° C is in the range of 0.2 ≦ y ≦ 0.7.

Meanwhile, Ba (Co _1/3 Nb _2/3 ) O ₃ and Ba (Ni _1/3 Nb _2/3 ) O in the (Ba (Zn _1/3 Nb _2/3 ) O ₃ + BaWO ₄ ) ceramic composition Even when ₃ is added at the same time, the temperature coefficient of the resonance frequency can be significantly lowered, and the preferable addition amount (x + y) in which the temperature coefficient of the resonance frequency is in the range of ± 10 ppm / ° C is in the range of 0.2≤x + y≤0.8.

As a result, the high frequency dielectric ceramic composition of the present invention is a perovskite solid solution, having a dielectric constant of about 30 to 40, a (Q × f) of 55,000 GHz or more, and a resonance frequency temperature coefficient (TCF) of -10 ppm / ^° C. It is possible to adjust the TCF according to the change in composition from + 20ppm / ℃ at, it can be usefully used as a material of the high-frequency dielectric ceramic component according to the purpose of use.

The present invention will be described in more detail by the following Examples, but the scope of the present invention is not limited to the conditions of the Examples.

(Example)

BaCO ₃ , ZnO, Nb ₂ O ₅ , CoO, NiO, WO ₃ and the like having a purity of 99% or more were weighed according to the composition ratios shown in Table 1, followed by wet mixing using a stabilized ZrO ₂ ball using distilled water as a solvent. The dried powder was calcined at 1000 ° C. to 1200 ° C. for 3 hours, and after milling, PVA (Polyvinyl Alcohol) and PEG (Polyethylene Glycol) were added and molded into a cylindrical specimen having a diameter of 15 mm and a thickness of about 7 to 8 mm. The molded specimen was heat treated at a temperature of about 500 ° C. for about 1 hour to remove the organic binder, and then sintered at about 1350 ° C. to 1400 ° C. for about 10 hours in the air.

The dielectric constant was measured by Hakki-Coleman method using resonance mode between two sheets of copper plate, and the temperature dependence of quality factor and resonance frequency was measured by cavity method. At this time, the measurement frequency was 4.0 to 6.0 GHz, and the temperature coefficient of the resonance frequency was obtained by measuring the change of the resonance frequency at 20 ° C and 80 ° C. The value of (Q × f) was obtained at a value of 1 GHz in relation to the fact that the product of the Q value generally established in the microwave dielectric and the measurement frequency f was constant. Microwave dielectric properties of the specimens for each composition are shown in Table 1 below.

(1-xyz) Ba (Zn _1/3 Nb _2/3 ) O ₃ -xBa (Co _1/3 Nb _2/3 ) O ₃ -yBa (Ni _1/3 Nb _2/3 ) O ₃ -zBaWO ₄ system High frequency dielectric properties Sample Number Mole fraction Permittivity (k) Q × f (GHz) TCF (ppm / ° C) x y z One 0 0 0 40.9 51,900 24.2 2 0 0 0.01 38.0 71,200 18.2 3 0 0 0.02 37.7 70,400 17.2 4 0 0 0.03 36.9 70,900 15.4 5 0 0 0.06 36.4 64,300 14.2 6 0.1 0 0.01 38.12 65,100 16.2 7 0.3 0 0.01 36.0 65,700 8.6 8 0.5 0 0.01 35.4 62,800 4.0 9 0.7 0 0.01 34.5 59,700 -1.2 10 0 0.1 0.01 37.5 62,500 11.7 11 0 0.3 0.01 36.2 59,300 6.4 12 0 0.5 0.01 35.1 56,800 1.2 13 0 0.7 0.01 33.2 55,400 -4.1 14 0.3 0.2 0.01 34 57,200 2.1 15 0.2 0.3 0.01 33.7 52,900 0.7 16 0.25 0.25 0.01 34.1 54,100 1.2

In the dielectric ceramic composition for high frequency of the present invention, as shown in Table 1, in the case of pure Ba (Zn _1/3 Nb _2/3 ) O ₃ of sample No. 1 (conventional example), the value of (Q × f) is about 51,900 GHz. However, the addition of BaWO ₃ significantly increased the (Q × f) above 64,000 GHz. And as the addition amount of Ba (Co _1/3 Nb _2/3 ) O ₃ increases, the temperature coefficient (TCF) of the resonant frequency gradually changes from +16.2 ppm / ℃ to -1 ppm / ℃, and the dielectric constant is 38 to 34 It has decreased consistently. In particular, in the composition of 0.5Ba (Zn _1/3 Nb _2/3 ) O ₃ -0.5Ba (Co _1/3 Nb _2/3 ) O ₃ -0.01BaWO ₄ , the dielectric constant is 35.4 and (Q × f) is 62,800 GHz. And excellent dielectric ceramics having a temperature coefficient of resonant frequency of 4.0 ppm / 占 폚 were obtained.

Also, when Ba (Ni _1/3 Nb _2/3 ) O ₃ was added instead of Ba (Co _1/3 Nb _2/3 ) O ₃ , the temperature coefficient of the resonance frequency was +11.7 ppm / ℃ as the amount of addition increased. Gradually changed from to -4.1ppm / ℃, and the dielectric constant decreased from 38 to 33. In particular, in the composition of 0.5Ba (Zn _1/3 Nb _2/3 ) O ₃ -0.5Ba (Ni _1/3 Nb _2/3 ) O ₃ -0.01BaWO ₄ , the dielectric constant is 35.1 and (Q x f) is 56,800 GHz. And excellent dielectric ceramics having a temperature coefficient of resonant frequency of 1.2 ppm / 占 폚 were obtained.

Furthermore, in the present invention, Ba (Zn _1/3 Nb _2/3 ) O ₃ + BaWO ₄ composition, Ba (Co _1/3 Nb _2/3 ) O ₃ and Ba (Ni _1/3 Nb _2/3 ) O ₃ may be prepared by complex addition, and in this case, the temperature coefficient of the resonant frequency was particularly stable in the range of ± 10 ppm / ° C.

As described above, in the high-frequency dielectric ceramic composition of the present invention, BaWO ₄ is added to Ba (Zn _1/3 Nb _2/3 ) O ₃ having excellent quality coefficient and dielectric constant, thereby improving low temperature sintering and improving quality coefficient. By adding (Co _1/3 Nb _2/3 ) O ₃ and / or Ba (Ni _1/3 Nb _2/3 ) O ₃ , it is possible to lower the temperature coefficient of the resonant frequency, so that the dielectric constant of 30 or more and 55,000 GHz or more A dielectric ceramic composition for high frequency having (Qxf) (quality factor x resonant frequency) can be produced, and the temperature coefficient of dielectric constant and resonant frequency of the composition can be adjusted by varying the composition ratio in some cases.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and is not limited to the spirit of the present invention. Various changes and modifications can be made by those who have

Claims (4)

General formula (1-xyz) Ba (Zn _1/3 Nb _2/3 ) O ₃ -xBa (Co _1/3 Nb _2/3 ) O ₃ -yBa (Ni _1/3 Nb _2/3 ) O ₃ -zBaWO ₄ , wherein the mole fractions x, y, and z range from 0 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.9, and 0 <z ≦ 0.3, respectively. The dielectric ceramic composition for high frequency as claimed in claim 1, wherein the range of x is 0.3 ≦ x ≦ 0.8. The dielectric ceramic composition for high frequency as claimed in claim 1, wherein the y range is 0.2 ≦ y ≦ 0.7. The dielectric ceramic composition of claim 1, wherein the range of x + y is 0.2 ≦ x + y ≦ 0.8.