KR100489886B1 - Microwave dielectric ceramic compositions and preperation method therof - Google Patents

Abstract

BaTiO ₃ is used as a starting material of Ba-compound in the dielectric composition consisting of a ratio of Ba to Ti of 1: 4 to 4.3 using general formula (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ It has a value ranging from 3 ≤ x ≤ 3.3, 0.035 ≤ y ≤ 0.3, 0.025 ≤ z ≤ 0.07, and additionally added to the total composition by weight ratio WO ₃ , SrWO ₄ , Nd ₂ O ₃ , Mn (NO ₃ ) A microwave dielectric ceramic composition and a method for producing the same are characterized in that ₂ nH ₂ O is added simultaneously or in a weight ratio of 0.3% to 5% or less. This dielectric ceramic has excellent dielectric properties with a dielectric constant of 40-65 and a quality factor (Q × f _o ) of 15000 to over 40000. It can be used as a patch antenna or dielectric resonator by adjusting the resonant frequency and temperature coefficient. It is especially suitable for 18mm × 18mm, 15mm × 15mm GPS patch antennas and C-band dielectric resonators.

Description

Microwave dielectric ceramic composition and manufacturing method therefor {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 GPS patch antennas, dielectric resonators, dielectric antennas operating in microwave bands.

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 automotive telephones, wireless telephones, pagers, and GPS (Global Positioning System). Microwave dielectric ceramics are used in filters, resonators, duplexers and antennas in these systems. Used as a material for passive components.

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 and purpose of use. As a dielectric resonator for a low noise block converter (hereinafter referred to as "LNB"), high temperature stability is essential, and thus the resonant frequency temperature coefficient is the most important characteristic, and a high dielectric constant is required for the miniaturization of the LNB. On the other hand, for the GPS patch antenna, because the bandwidth of the frequency used is large, it is important to control the dielectric constant according to the desired patch size rather than the temperature coefficient.

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, the materials that have been used in the C-band band (5 GHz band) as the dielectric resonator for LNB are BaO-TiO ₂ based (BT) having a dielectric constant of 37 and CaTiO ₃ -NdAlO ₃ having a dielectric constant of 45. However, the BT-based low dielectric constant cannot meet the miniaturization of the LNB, so it is currently used in the Ku-Band band (10 GHz band) and CaTiO ₃ -NdAlO ₃ is still used as a dielectric resonator for C-band and Ku-band. Although miniaturization of the dielectric resonator which occupies the largest volume in the LNB is being continually pursued, the study of applying the dielectric constant of 50 for C-band is underway and the required resonant frequency temperature coefficient is 9 ± 1ppm / ℃.

On the other hand, the GPS patch antenna has also been miniaturized, and a patch antenna having a size of 25mm × 25mm using MgTiO ₃ -CaTiO ₃ based material having a dielectric constant of 20 has been widely used, and a size of 20mm × 20mm has been reduced using a BT system having a dielectric constant of 37. Patch antennas have been developed. However, in order to manufacture a patch antenna of 18 mm x 18 mm or less, a material having a dielectric constant of 43 to 45 or more is required.

An object of the present invention is to provide a microwave dielectric ceramic composition capable of miniaturizing parts by improving dielectric properties on the basis of recognizing the problems of the prior art and the trend of component development as described above, and an object thereof.

For this purpose, according to the present invention, BaTiO ₃ is used as a starting material of a Ba compound in a dielectric composition consisting of a ratio of Ba to Ti of 1: 4 to 1: 4.3, using general formula (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO _2, having values in the range of 3 ≦ x ≦ 3.3, 0.035 ≦ y ≦ 0.3, 0.025 ≦ z ≦ 0.07, and additionally WO _{3 in} weight ratio for the whole composition. , SrWO ₄ , Nd ₂ O ₃ , Mn (NO ₃ ) ₂ · nH ₂ O provides a microwave dielectric ceramic composition characterized in that the weight ratio is added simultaneously or in the range of 0.3% to 5%, respectively.

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.

In addition, the present invention is to prepare a SrWO ₄ powder by mixing and heat treatment SrCO ₃ and WO ₃ powder, (1-yz) [BaTiO ₃ + x TiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ in a weight ratio to the composition After calcining by mixing with WO ₃ , SrWO ₄ , Nd ₂ O ₃ , Mn (NO ₃ ) ₂ · nH ₂ O, etc., respectively or simultaneously at a rate of 5% or less, the calcined powder is pulverized and shaped into a predetermined shape. 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 1280 to 1350 ° C.

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

SrCO ₃ 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 SrWO ₄ powder.

BaTiO ₃ and TiO ₂ , Sm ₂ O ₃ , CeO ₂ are weighed according to the molar ratio of (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ (3 ≦ x ≦ 3.3, 0.035 ≦ y ≤ 0.3, 0.025 ≤ z ≤ 0.07), to which WO ₃ , SrWO ₄ , Nd ₂ O ₃ , Mn (NO ₃ ) ₂ · nH ₂ O are each added at the weight ratio or simultaneously in the range of 0.3% to 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 range of 1280-1350 ° 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 WO ₃ (% by weight) SrWO ₄ (% by weight) Nd ₂ O ₃ (% by weight) Mn (NO ₃ ) ₂ nH ₂ O (% by weight) Permittivity (ε _r ) Quality Factor (Q × f _o ) Temperature coefficient (τ _f ) (ppm / ℃) One 3.0 0.035 0.025 43.3 35888 19.2 2 3.05 0.035 0.025 40.4 49123 15.4 3 3.199 0.035 0.025 40.6 43236 8.7 4 3.2 0.035 0.025 40.3 39030 3.5 5 3.201 0.035 0.025 40.8 42299 2.5 6 3.2 0.035 0.015 40.4 39422 10.2 7 3.2 0.045 0.025 41.4 39296 9.0 8 3.2 0.06 0.025 42.0 34314 8.1 9 3.2 0.08 0.025 42.2 27576 7.7 10 3.2 0.08 0.045 43.9 28132 7.7 11 3.2 0.08 0.065 44.6 26388 8.3 12 3.2 0.1 0.025 44.1 25704 7.0 13 3.2 0.1 0.025 0.3 44.3 29541 6.8 14 3.2 0.1 0.025 0.5 44.5 28369 5.5 15 3.2 0.1 0.025 1.0 44.9 29453 6.4 16 3.2 0.1 0.025 0.3 0.5 44.6 30247 5.8 17 3.2 0.1 0.025 0.5 0.5 44.4 31568 5.0 18 3.2 0.16 0.025 47.4 22987 8.0 19 3.2 0.16 0.05 48.8 21407 8.5 20 3.2 0.18 0.025 49.2 20754 8.3 21 3.2 0.18 0.03 49.2 19056 9.3 22 3.2 0.18 0.035 49.4 19818 9.4 23 3.2 0.2 0.025 50.2 18700 7.5 24 3.2 0.25 0.025 58.3 17105 3.5 25 3.2 0.3 0.025 65.3 15081 2.5 26 3.0 0.16 0.025 49.2 21253 18.3 27 3.1 0.16 0.025 48.5 22201 14.5 28 3.2 0.16 0.025 47.6 22987 8.0 29 3.3 0.16 0.025 47.3 23161 3.9 30 3.2 0.18 0.025 0.3 49.1 26598 4.6 31 3.2 0.18 0.025 0.5 48.7 27832 3.7 32 3.2 0.18 0.025 1.0 48.5 28453 2.0 33 3.2 0.18 0.025 0.3 49.2 25497 7.5 34 3.2 0.18 0.025 0.5 49.0 24536 6.3 35 3.2 0.18 0.025 1.0 48.6 26732 5.4 36 3.2 0.18 0.025 One 50.4 22418 8.7 37 3.2 0.18 0.025 2 51.0 23245 8.9 38 3.2 0.18 0.025 4 51.2 22634 9.8 39 3.2 0.18 0.025 0.3 49.5 23548 9.6 40 3.2 0.18 0.025 0.5 49.7 25623 9.3 41 3.2 0.18 0.025 1.0 49.5 24826 8.7 42 3.2 0.18 0.025 0.3 0.5 49.3 24581 8.5 43 3.2 0.18 0.025 0.3 0.5 2 50.8 26936 9.0 44 3.2 0.18 0.025 0.3 0.5 4 51.1 24871 9.5 45 3.2 0.18 0.025 0.3 0.5 2 0.3 51.0 25781 9.8 46 3.2 0.18 0.025 0.3 0.5 2 0.5 50.8 26754 9.2

As shown in Table 1, (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ has a very wide dielectric constant according to the change of x, y, and z values. If it is 3.2 or more, it has a value within 10ppm / ℃ (Sample Nos. 4 to 25 and 28 to 46).

(1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO _2, where x = 3.2, 0.08 ≦ y ≦ 0.1, 0.025 ≦ z ≦ 0.065, and SrWO ₄ and Mn (NO ₃ ) ₂ · nH ₂ o was added to the composition to be less than 1% each, or at the same time the weight ratio (sample Nos. 10-17) 44-45 permittivity, quality factor (Q × f _o) was 25000 or more, the temperature coefficient 5~8ppm / ℃. It is therefore suitable for 18mm x 18mm GPS patch antennas.

For (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ , the composition with x = 3.2, y = 0.25, z = 0.025 is (Sample No. 24) dielectric constant 58.3, quality factor (Q × f _o ) 17,000 or more and the temperature coefficient was 3.5 ppm / 占 폚. This can be applied with a 15mm × 15mm GPS Patch Antenna.

FIG. 1 shows a return loss result of a patch antenna after fabricating a 15 mm × 15 mm GPS patch antenna using a high frequency dielectric material (sample number 24) manufactured 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 Return Loss drops by more than 19dB, so it can be seen that 50Ω Impedance matching is also good. At this time, the bandwidth is 9MHz. A patch antenna based on a dielectric constant of 20 materials commonly used at GPS satellite signals 1575.42 MHz has a size of 25 × 25 × 4, but a patch antenna based on a dielectric constant of 44 to 45 has a size of 18 According to the present invention, when the material having a dielectric constant of 58 to 60 is used, the size can be reduced to 15 × 15 × 4. Therefore, it can be seen that the present invention is a material suitable for miniaturization of the GPS patch antenna.

(1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO _{2 wherein} x = 3.2, y = 0.18, z = 0.025, and WO ₃ , SrWO ₄ , Nd ₂ O ₃ , Mn ( NO _{3) 2} · composition which is added to no more than 5% of nH ₂ O, respectively, or at the same time the weight ratio (sample Nos. 36-46), the dielectric constant 50 ± 1, the quality factor (Q × f _o) 20000 or more, the temperature coefficient 9 ± 1ppm / ° C.

Table 2 shows the sizes and resonant frequencies of dielectric resonators made from microwave dielectric materials prepared according to the present invention (Sample No. 46). Current frequency of C-band LNB is 5.15GHz ± 20MHz and 5.75GHz ± 20MHz. As shown in Table 2, the microwave dielectric material manufactured according to the present invention was used to adjust the inner diameter to 3.70 ± 0.1mm, the outer diameter of 10.40 to 11.00mm, and the thickness of 2.70 to 4.00mm to be applied as a dielectric resonator for LNB in the C-band band. can do. Thus, the composition of (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ with x = 3.2, y = 0.18, z = 0.025 and WO ₃ , SrWO ₄ , Nd ₂ O ₃ , Mn A composition in which (NO ₃ ) ₂ nH ₂ O is added at the same or less than 5% by weight (Sample Nos. 36 to 46) is suitable for use as a C-band dielectric resonator.

 Size and Resonance Frequency of C-band Dielectric Resonator for LNB

NNo. Resonator Size (mm) Resonant frequency Resonator Bore Outer diameter of resonator Resonator thickness One 3.70 11.00 2.70 5.6660 2 3.70 10.85 2.74 5.6300 3 3.70 10.88 2.77 5.6100 4 3.70 10.72 2.82 5.6280 5 3.70 10.75 2.81 5.6153 8 3.70 10.69 3.71 5.2155 9 3.70 10.70 3.82 5.1735 10 3.70 10.44 3.98 5.1490

As described above, the dielectric composition according to the present invention has excellent dielectric properties with a dielectric constant of 40 to 65 and a quality factor (Q × f _o ) of 15000 to 40000 or more, and can adjust the resonant frequency temperature coefficient of the patch antenna, It can be used as dielectric resonator, and especially suitable for 18mm × 18mm, 15mm × 15mm GPS Patch Antenna, C-band dielectric resonator.

Figure 1 shows the result of the return loss of the GPS patch antenna after manufacturing a 15mm x 15mm GPS patch antenna using a high-frequency dielectric material prepared by the present invention.

Claims (7)

A dielectric composition composed of a ratio of Ba and Ti of 1: 4 to 1: 4.3, wherein the compositional formula (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ Wherein x, y, and z satisfy 3 ≦ x ≦ 3.3, 0.035 ≦ y ≦ 0.3, 0.025 ≦ z ≦ 0.07, respectively. The microwave dielectric ceramic composition according to claim 1, wherein at least one selected from WO ₃ , SrWO ₄ , Nd ₂ O ₃ , and Mn (NO ₃ ) ₂ nH ₂ O is added to the composition. The microwave dielectric ceramic composition of claim 2, wherein the additive is added in a weight ratio of 0.3% to 5% with respect to the composition of claim 1. 4. The microwave dielectric ceramic composition of claim 3, wherein the dielectric composition has a dielectric constant of 40 to 65 and a quality factor of 15000 to 40000. 5. The microwave dielectric ceramic composition of claim 4, wherein the dielectric composition has a temperature coefficient of 9 ± 1 ppm / ° C. BaTiO ₃ was prepared as a starting material of a Ba compound, BaTiO ₃ and TiO ₂ , Sm ₂ O ₃ , CeO ₂ are weighed according to the molar ratio of (1-yz) [BaTiO ₃ + xTiO ₂ ] + ySm ₂ O ₃ + zCeO ₂ , where x, y and z are each 3 Satisfies ≤ x ≤ 3.3, 0.035 ≤ y ≤ 0.3, 0.025 ≤ z ≤ 0.07, At least one selected from WO ₃ , SrWO ₄ , Nd ₂ O ₃ , and Mn (NO ₃ ) ₂ nH ₂ O is added to the weighed material in a weight ratio of 0.3 to 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 6, wherein the calcination temperature is 1000 ℃, sintering temperature is in the range of 1280 ~ 1350 ℃, heating rate during calcination and sintering is 5 ℃ / min method for producing a microwave dielectric ceramic composition.