KR20030097555A - Microwave dielectric ceramic compositions and preperation method therof - Google Patents

Abstract

PURPOSE: Provided is a dielectric ceramic composition, which has an improved quality factor sufficient to obtain a compact component and is easily controlled in terms of the temperature coefficient without adding PbO. CONSTITUTION: The microwave dielectric ceramic composition comprises Ba and Ti in the ratio of 1:4 and is represented by the formula of: BaTiO3.£xNd2O3+ySm2O3+zBi2O3|.3TiO2, wherein x is ranged from 0.1 to 0.3, y is ranged from 0.66 to 0.86 and z is ranged from 0 to 0.08 provided that x+y+z=1. Particularly, the microwave dielectric ceramic composition optionally further comprises one or more additives selected from the group consisting of ZnWO4, ZnTiO3 and CeO2, in the amount of 0.1-1.5 wt% based on the total amount of the composition. Further, the composition has the dielectric constant of 87-93 and the quality factor of 6000-8000.

Description

Microwave dielectric ceramic composition and manufacturing method thereof {MICROWAVE DIELECTRIC CERAMIC COMPOSITIONS AND PREPERATION METHOD THEROF}

TECHNICAL FIELD The present invention relates to dielectric ceramic compositions for microwaves, and more particularly, to dielectric ceramic compositions for microwave devices such as patch antennas, dielectric filters, and dielectric antennas operating in the microwave band.

The characteristics of dielectric ceramics that can be used in the high frequency band between 500 MHz and 30 GHz are (1) dielectric constant (ε _r : dielectric constant) (2) temperature coefficient of resonance frequency (τ _f ) and (3) Q × f _o (Q ∝ 1 / tanδ: quality factor). The permittivity is a factor that determines the size of the resonator at a certain operating frequency (resonance frequency). High permittivity is required for miniaturization of components. The temperature coefficient of the resonant frequency indicates the temperature dependence of the operating frequency (resonant frequency) and is a factor related to the stabilization of the operating frequency of a communication device used in harsh conditions indoors and outdoors, and generally requires characteristics within ± 10 ppm / ° C. . Q x f _o is a factor related to the dielectric loss. As the value of Q x f _o increases, the dielectric loss decreases, so that the bandpass characteristic, that is, the frequency characteristic of the resonator is improved when used as the dielectric filter. Therefore, in order to reduce noise by narrowing the frequency width of the resonator and the filter, a high quality factor is required.

Recently, as the use of information communication devices such as mobile communication and satellite broadcasting increases, interest in dielectric ceramic devices using microwaves is increasing. Particularly, mobile communication media include automobile telephones, wireless telephones, pagers, GPS (Global Positioning System), and microwave dielectric ceramics are passive components of filters, duplexers, and antennas in these systems. Used as the material for the parts.

The reason for using dielectric in high frequency band is that it can achieve stability and miniaturization with respect to temperature. In the dielectric, the wavelength of high frequency is inversely proportional to the dielectric constant of the dielectric. The shorter the dielectric constant, the smaller the device becomes, and when the device is made of metal, the volume becomes large and the stability of the frequency is lowered by the thermal expansion of the metal. These phenomena can be solved by using a dielectric material. have.

Dielectric ceramics occupy an important position in mobile / satellite communication components, and their characteristics and sizes vary depending on the frequency of use, purpose of use of base stations, terminals, etc. Since the selection of the filter is made in a direction that emphasizes the characteristics rather than the size for the base station, a material having a high Q value is required, but a material having a high dielectric constant is required because the use of the terminal places more emphasis on miniaturization. At present, PCS of 900MHz band and PCS of 1.8GHz band have a dielectric constant of 80 or higher, Q × f _o 5000 or higher, and τ _f of 5ppm / ° C or lower. However, as the frequency increases to IMT2000 (2.1 GHz band), wireless LAN, Bluetooth (2.4 GHz band), etc., a material having a higher Q value is required.

Research into dielectric ceramic compositions has been conducted on many titanic acid-based materials since TiO ₂ was first developed. As a result, currently used microwave dielectric compositions include TiO ₂ based on Ba ₂ Ti ₉ O ₂₀ , (Zr, Sn) TiO ₄ , BaO-Nd ₂ O ₃ -4 TiO ₂ based (BNT), and Ba (Mg _{1). / 3} Ta _2/3 ) O ₃ , Ba (Zn _1/3 Ta _2/3 ) O ₃ and many other dielectrics with complex perovskite structures have been found, and also CaTiO ₃ -NdAlO ₃ , CaTiO ₃ -La Efforts have been made to develop new dielectric materials using solid solutions having two or more types of perovskite structures, such as (Zn _1/2 Ti _1/2 ) O ₃ . Among them, a material that has been studied for the purpose of miniaturization of parts is BNT-based BaO-PbO-Nd ₂ O ₃ -TiO ₂ (BPNT-based), in which PbO is added and temperature coefficients are commercially used.

However, BPNT materials have higher dielectric constants than other microwave dielectrics, but their Q-values (Q × f _o ) are less than 5000, so the Q-values need to be improved to cope with the high frequency of communication components. Heavy PbO is a volatile substance, which causes problems of product stability and manufacturing contamination, and thus requires development of a material without PbO.

An object of the present invention is to provide a dielectric ceramic composition capable of miniaturizing components in response to high frequency of the use frequency by improving the Q value in order to solve the problems of the prior art as described above.

Another object of the present invention is to provide a microwave dielectric ceramic composition and a method of manufacturing the same, which can easily adjust the temperature coefficient within a range of ± 10 ppm / ° C without adding PbO.

Figure 1 shows the result of the return loss of the GPS patch antenna after manufacturing a 13mm x 13mm GPS patch antenna using a high-frequency dielectric material prepared by the present invention.

For this purpose, according to the present invention, BaTiO ₃ · [xNd ₂ O ₃ + ySm ₂ O ₃ using BaTiO ₃ as a starting material of a Ba compound in a dielectric composition consisting of a ratio of Ba and Ti of 1: 4. + zBi ₂ O ₃ ] · 3TiO ₂ at 0.1 ≦ x ≦ 0.3, 0.66 ≦ y ≦ 0.86, 0 ≦ z ≦ 0.08, x + y + z = 1 and ZnWO ₄ , ZnTiO ₃ , Provided is a microwave dielectric ceramic composition characterized in that CeO ₂ is added at the same or less than 1.5% each or simultaneously.

BaO-TiO ₂ -based oxides such as BaTi ₄ O ₉ , Ba ₂ Ti ₉ O ₂₀ , BaO-Nd ₂ O ₃ -4 TiO ₂ -based (BNT-based), etc., generally use BaCO ₃ as a starting material for Ba- compounds. to be. However, in this case, CO ₂ in BaCO ₃ volatilizes in the gaseous state during the manufacturing process (calcination), resulting in mass loss, which leads to a decrease in productivity during mass production. Therefore, the present invention aims to improve the productivity of the product by using BaTiO ₃ instead of BaCO ₃ generally used for mass production.

The present invention is mixed with ZnO and WO ₃ powder was heat treated to prepare a ZnWO ₄ powder, and a mixture of ZnO and TiO ₂ powder and heat treated ready for ZnTiO ₃ powder and BaTiO ₃ · [xNd ₂ O ₃ + ySm ₂ O ₃ + zBi ₂ O ₃ ] · 3TiO ₂ powder, mixed with CeO ₂ in a weight ratio, respectively, or at the same time mixed at a ratio of 0.1% to 1.5% or less, and then calcined to form a predetermined form. The present invention provides a method for producing a microwave dielectric ceramic composition comprising forming a sintered body by heat-treating the molded body in a temperature range of 1300 to 1400 ° C.

Hereinafter, the present invention will be described in detail through examples.

ZnO and WO ₃ powders were weighed in a 1: 1 molar ratio and dried at 120 ° C. after wet mixing for 24 hours using zirconia balls at a 1: 1 ratio of powder to distilled water. The dried powder was placed in an alumina crucible and calcined at 900 ° C. for 3 hours to obtain ZnWO ₄ powder.

ZnO and TiO ₂ powders were weighed in a 1: 1 molar ratio and the mixture was wet mixed for 24 hours using zirconia balls at 1: 1 ratio of powder to distilled water and then dried at 120 ° C. The dried powder was placed in an alumina crucible and calcined at 900 ° C. for 3 hours to obtain ZnTiO ₃ powder.

BaTiO ₃ and TiO ₂ , Nd ₂ O ₃ , Sm ₂ O ₃ , Bi ₂ O ₃ are weighed to the molar ratio of BaTiO ₃ · [xNd ₂ O ₃ + ySm ₂ O ₃ + zBi ₂ O ₃ ] · 3TiO ₂ 0.1≤x≤0.3, 0.66≤y≤0.86, 0≤z≤0.08, x + y + z = 1) After adding ZnWO ₄ , ZnTiO ₃ , CeO ₂ in weight ratio, respectively or simultaneously at 0.1 ~ 1.5% The mixed powders of various compositions obtained were prepared.

The ratio of powder to distilled water was adjusted to 1: 1, followed by wet mixing for 24 hours using zirconia balls and drying at 120 ° C. The dried powder was placed in an alumina crucible and calcined at 1000 ° C. for 3 hours.

Each calcined powder was ball milled for 24 hours and uniaxially press-molded into a disc shape having a diameter of 15 mm and a thickness of 7 mm at a pressure of 80 MPa. The compact was heat treated at a temperature in the range of 1300 to 1400 ° C. to obtain a compact sintered compact. The rate of temperature increase during calcination and sintering was 5 ° C./min and then furnace cooled. Both surfaces of the sintered specimens were alumina paste 1 μm and 0.3 μm, and after specular treatment, the quality factor (Q × f _o ), the resonant frequency temperature coefficient (τ _f ), and the dielectric constant (ε _r ) were measured using a network analyzer (HP8753D). It was measured by the Hockey-Coleman post resonator method. The above results are shown in Table 1.

Dielectric Properties of Dielectric Ceramic Compositions According to the Present Invention

Sample Number x y z ZnWO ₄ (% by weight) ZnTiO ₃ (% by weight) CeO ₂ (% by weight) Permittivity (ε _r ) Quality Factor (Q × f _o ) Temperature coefficient (τ _f ) (ppm / ℃) One 1.00 0 0 - - - 85.0 5719 95.8 2 0.9 0.1 0 - - - 90.4 6492 82.7 3 0.96 0 0.04 - - - 92.1 5958 71.8 4 0.50 0.50 0 - - - 87.8 6228 36.2 5 0.50 0.46 0.04 - - - 89.4 6454 24.9 6 0.46 0.50 0.04 - - - 90.1 6465 22.9 7 0.44 0.50 0.06 - - - 91.9 6269 17.2 8 0.42 0.50 0.08 - - - 93.5 5486 14.5 9 0.40 0.56 0.04 - - - 90.2 6397 17.8 10 0.30 0.66 0.04 - - - 89.6 6596 11.7 11 0.28 0.66 0.06 - - - 91.0 5192 6.1 12 0.26 0.70 0.04 - - - 89.5 6711 7.5 13 0.20 0.76 0.04 - - - 89.6 6513 3.7 14 0.15 0.81 0.04 - - - 89.5 6187 1.5 15 0.10 0.86 0.04 - - - 89.2 6273 -2.3 16 0.26 0.70 0.04 0.1 - - 89.3 6313 6.4 17 0.26 0.70 0.04 0.2 - - 89.2 6557 5.8 18 0.26 0.70 0.04 0.4 - - 89.0 6896 3.7 19 0.26 0.70 0.04 0.6 - - 88.7 7018 1.5 20 0.26 0.70 0.04 1.0 - - 88.1 7237 -1.3 21 0.26 0.70 0.04 - 0.3 - 89.9 6546 2.8 22 0.26 0.70 0.04 - 0.5 - 88.5 6943 1.2 23 0.26 0.70 0.04 - 1.0 - 87.2 7357 -1.0 24 0.26 0.70 0.04 - 1.5 - 86.5 7935 -3.0 26 0.26 0.70 0.04 - - 0.1 87.8 6432 4.0 27 0.26 0.70 0.04 - - 0.3 88.0 6765 2.7 28 0.26 0.70 0.04 - - 0.5 88.9 6959 0.3 29 0.26 0.70 0.04 - - 1.0 87.6 8004 3.0 30 0.26 0.70 0.04 0.4 0.3 - 89.3 7026 3.5 31 0.26 0.70 0.04 0.4 0.5 - 89.0 7531 2.7 32 0.26 0.70 0.04 0.4 1.0 - 88.7 7790 -1.5 33 0.26 0.70 0.04 0.4 - 0.1 87.9 7561 3.2 34 0.26 0.70 0.04 0.4 - 0.3 88.0 7023 3.6 35 0.26 0.70 0.04 0.4 - 0.5 89.1 7832 1.3 36 0.26 0.74 - 0.4 - 0.5 88.1 8329 4.5 37 0.26 0.70 0.04 0.4 0.3 0.5 89.0 7342 2.1 38 0.26 0.70 0.04 0.4 0.5 0.5 88.7 7154 1.7 39 0.26 0.74 - 0.4 0.3 0.5 89.2 8127 3.3 40 0.24 0.70 0.06 0.4 0.3 0.5 91.0 6583 -2.5 41 0.24 0.70 0.06 0.4 0.5 0.5 91.2 6691 -4.2 42 0.24 0.76 - 0.4 0.5 0.5 89.0 7854 -1.3 43 0.22 0.70 0.08 - 0.3 0.5 93.1 5987 -3.1 44 0.22 0.70 0.08 0.4 0.3 0.5 92.7 6235 -4.2 45 0.22 0.78 - 0.4 0.3 0.5 88.5 7957 -2.7

As shown in Table 1 as _{BaO · Nd 2 O 3 · 4TiO} 2 is a dielectric constant of about 85 and the number of the quality factor value 5719 or the resonant frequency thermometer 95.8ppm / ℃ (sample No. _{1) BaO · Nd 2 O 3} · 4TiO 2 There is a limit to applying itself as a component. Therefore, replacing the Nd ₂ O ₃ to improve the temperature coefficient as Sm ₂ O ₃ and Bi ₂ O ₃ and investigated the change in the dielectric properties. As the bar shown in Table 1, the more substitution of Nd ₂ O ₃ as Sm ₂ O ₃ and Bi ₂ O ₃ was reduced is the temperature coefficient, Sm ₂ O ₃ is 0.66 molar, more than 0.04 mole of Bi ₂ O ₃ thermometer from substituted Composition The number was lowered below 10 ppm / ° C. (Sample Nos. 10 to 15)

The ZnWO ₄ (sample No. 16~20), ZnTiO ₃ (sample No. 21~24), CeO ₂ (Sample No. 26-29) that increases the Q × f _o value of the material when added, and this effect is ZnWO ₄ ZnTiO ₃ was added simultaneously (Sample No. 30-32), ZnWO ₄ and CeO ₂ (Sample No. 33-36), or ZnWO ₄ , ZnTiO ₃ , CeO ₂ (Sample No. 37-42, 44-45) were added simultaneously. The same effect occurs.

In the composition represented by BaTiO ₃ · [xNd ₂ O ₃ + ySm ₂ O ₃ + zBi ₂ O ₃ ] · 3TiO ₂ , 0.1 ≦ x ≦ 0.3, 0.66 ≦ y ≦ 0.86, 0 ≦ z ≦ 0.08, x + y + z A composition in which = 1 (Sample Nos. 10 to 15) and ZnWO ₄ , ZnTiO ₃ , and CeO ₂ were respectively added or added simultaneously at 0.1 to 1.5% by weight of the total composition (Sample Nos. 16 to 45). It can be seen that it exhibits characteristics suitable for use as a dielectric resonator, duplexer, filter, patch antenna, and the like.

Figure 1 shows a result of Return Loss of a patch antenna after manufacturing a 13 × 13 × 4 GPS patch antenna using a high frequency dielectric material prepared by the present invention. The characteristics of patch antennas are evaluated in terms of Center Frequency (f _o ), Return Loss, and Impedance Matching. Originally, the GPS satellite signal is 1575.42MHz, but it is generally selected to have a high F _o about 5MHz considering the effect of the case. Return Loss is more than 10dB, Input Impedance is 50Ω, and Impedance Matching is evaluated as good characteristic when Return Loss drops to 10dB or more. do. In the figure, f _o = 1.580 GHz, and the return loss is more than 20 dB, so it can be seen that 50 Ω impedance matching is also good. At this time, the bandwidth is 5.9 MHz. The patch antenna based on the dielectric constant 20 material commonly used at the GPS satellite signal 1575.42 MHz has a size of 25 × 25 × 4 but a size of 13 × 13 × reduced by 52% when using the material according to the present invention. Appears as 4. Therefore, it can be seen that the present invention is a material suitable for miniaturization of the GPS patch antenna.

As described above, the dielectric composition according to the present invention has a dielectric constant of 87 to 93, a quality coefficient of 6000 to 8000, and a resonant frequency temperature coefficient of ± 10 ppm / 占 폚, which is suitable for miniaturization of a patch antenna and a dielectric filter.

Claims (6)

A dielectric composition consisting of a ratio of Ba and Ti of 1: 4, wherein the compositional formula BaTiO ₃ [xNd ₂ O ₃ + ySm ₂ O ₃ + zBi ₂ O ₃ ] · 3TiO ₂ Wherein x, y, and z satisfy 0.1 ≦ x ≦ 0.3, 0.66 ≦ y ≦ 0.86, 0 ≦ z ≦ 0.08, and x + y + z = 1, respectively. The microwave dielectric ceramic composition of claim 1, wherein at least one selected from ZnWO ₄ , ZnTiO ₃ , and CeO ₂ is added to the composition. The microwave dielectric ceramic composition of claim 2, wherein the additive is added in an amount of 0.1% or more and 1.5% or less by weight with respect to the composition of claim 1. The microwave dielectric ceramic composition according to claim 3, wherein the dielectric composition has a dielectric constant in the range of 87 to 93, a quality coefficient of 6000 to 8000, and a resonant frequency temperature coefficient of ± 10 ppm / ° C. BaTiO ₃ was prepared as a starting material of a Ba compound, BaTiO ₃ and TiO ₂ , Nd ₂ O ₃ , Sm ₂ O ₃ , Bi ₂ O ₃ were weighed to the molar ratio of BaTiO ₃ · [xNd ₂ O ₃ + ySm ₂ O ₃ + zBi ₂ O ₃ ] · 3TiO ₂ Where 0.1 ≦ x ≦ 0.3, 0.66 ≦ y ≦ 0.86, 0 ≦ z ≦ 0.08, x + y + z = 1), At least one selected from ZnWO ₄ , ZnTiO ₃ , and CeO ₂ is added to the weighed material in a weight ratio of 0.1 to 1.5% to obtain a mixed powder. A method for producing a microwave dielectric ceramic composition comprising calcining, molding and sintering a mixed powder. The method of claim 5, wherein the calcination temperature is 1000 ℃, sintering temperature is in the range of 1300 ~ 1400 ℃, heating rate during calcination and sintering is 5 ℃ / min method for producing a microwave dielectric ceramic composition.