JP2010120847A - Dielectric ceramic composition for high frequency wave and dielectric resonator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a dielectric ceramic composition for high frequency wave which has high Q value, the decreasing rate of the Q value at 125°C to that at 25°C is low and the curve of the temperature coefficient (τf) of resonant frequency is small. <P>SOLUTION: The dielectric ceramic composition comprises a main component containing at least Mg, Ca and Ti as metal elements and Nb. When the composition formula of the main component is expressed by aMgO-bCaO-cTiO<SB>2</SB>based on the molar ratio of the metal elements, the relations of 0.42≤a≤o.51, 0.01≤b≤0.06, 0.45≤c≤0.53, (where a+b+c=1) are satisfied. The Qf value at 1 GHz is equal to or above 79,000. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dielectric ceramic composition for high frequency and a dielectric resonator having a high Q value in a high frequency region such as a microwave and a millimeter wave. For example, the present invention is used in a high frequency region such as a microwave and a millimeter wave. Resonator materials, dielectric substrate materials for MICs, dielectric waveguide materials, multilayer ceramic capacitors, dielectric ceramic compositions for high frequencies that can be used for impedance matching of various microwave circuits, and dielectrics It relates to a resonator.

Dielectric ceramics are widely used in dielectric resonators, dielectric substrates for MICs, waveguides, and the like in high frequency regions such as microwaves and millimeter waves. Since the wavelength is there as characteristics required (1) dielectric material is reduced to 1 / .epsilon.r ^1/2, relative dielectric constant with respect to the miniaturization demand is large, the dielectric loss in the (2) high frequency The above three characteristics are mainly cited as follows: (1) a small Q, that is, a high Q value; (3) a small change in the resonance frequency with respect to temperature; Conventionally, as this type of dielectric ceramic, for _{example, CaO · MgO · TiO 2 ·} La 2 O 3 · CeO 2 based material disclosed in JP-A-7-282627, a La ₂ O ₃ in a molar ratio 0 0.07 <La ₂ O ₃ <0.20 is described. Japanese Laid-Open Patent Publication No. 7-262824 discloses a CaO.MgO.TiO ₂ .Nd ₂ O ₃ .CeO ₂ -based material, and Nd ₂ O ₃ in a molar ratio of 0.07 <Nd ₂ O ₃ <0.20. The inclusion is described.

  However, the dielectric ceramics in these conventional techniques have a low temperature coefficient τf curve of the resonance frequency, that is, the linearity of the temperature drift is low. Further, the Q value at a high temperature (for example, 125 ° C.) is greatly reduced as compared with the Q value at a normal temperature (for example, 25 ° C.). For this reason, dielectric resonators and dielectric substrates using these dielectric porcelains have problems that it is difficult to control the characteristic change accompanying the temperature change with high accuracy and that the loss at high frequency becomes large. It was. The present invention has been completed in view of the above circumstances, and the curvature of the temperature coefficient τf of the resonance frequency, that is, the linearity of the temperature drift is high while maintaining a high Q value with εr of about 16 to 24, and at room temperature. An object of the present invention is to provide a high frequency dielectric ceramic composition and a dielectric resonator that have a low Q value decrease rate at a high temperature with respect to the Q value.

The high frequency dielectric ceramic composition of the present invention is a high frequency dielectric ceramic composition having a main component containing at least Mg, Ca, Ti as a metal element and Nb,
When the composition of the main component is expressed as aMgO · bCaO · cTiO ₂ by the molar ratio of the metal elements, the a, b and c are:
0.42 ≦ a ≦ 0.51
0.01 ≦ b ≦ 0.06
0.45 ≦ c ≦ 0.53
(However, a + b + c = 1) is satisfied, and the Qf value at 1 GHz is 79000 or more.

In the above dielectric ceramic composition, the Nb is preferably contained in an amount of 0.01 part by weight or more and less than 0.1 part by weight in terms of Nb ₂ O _{5 with} respect to 100 parts by weight of the main component.

The dielectric ceramic composition preferably contains at least one or more rare earth elements of Pr, Nd, Sm, and La, and contains a total of 0.01 to 3 parts by weight of the rare earth elements and the Nb. (However, Pr is converted to Pr ₆ O ₁₁ , Nd is converted to Nd ₂ O ₃ , Sm is converted to Sm ₂ O ₃ , La is converted to La ₂ O ₃ , and Nb is converted to Nb ₂ O ₅ ).

  Preferably, in the above dielectric ceramic composition, the Q value at 125 ° C. is 75% or more of the Q value at 25 ° C.

  Furthermore, the dielectric resonator according to the present invention includes a dielectric ceramic disposed between a pair of input / output terminals, wherein the dielectric ceramic is operated by electromagnetic coupling, and the dielectric ceramic is composed of the dielectric ceramic composition. It consists of things.

As described above in detail, the high-frequency dielectric ceramic composition has a main component containing at least Mg, Ca, Ti as metal elements and Nb, and the main component has a composition formula based on the molar ratio of the metal elements as aMgO. When expressed as bCaO · cTiO ₂ , a, b and c are 0.42 ≦ a ≦ 0.51, 0.01 ≦ b ≦ 0.06, 0.45 ≦ c ≦ 0.53 (where a + b + c = 1) is satisfied, and the Qf value at 1 GHz is 79000 or more.

  Thereby, the dielectric ceramic composition for high frequency of the present invention can be used for a resonator material used in a microwave or millimeter wave region, for example, in an apparatus such as a car phone, a cordless telephone, a personal radio, a satellite broadcast receiver, or the like. It is applied to dielectric substrate materials for MICs, dielectric waveguide lines, dielectric antennas, impedance matching of various microwave circuits, and other various electronic components, and is particularly suitable for dielectric resonators.

It is the schematic which shows the dielectric resonator of this invention.

In this embodiment, it is composed of a composite oxide containing at least Mg, Ca, and Ti as metal elements, and when the composition formula by the molar ratio of the metal elements is expressed as aMgO · bCaO · cTiO ₂ , the a, b, and c is
0.42 ≦ a ≦ 0.51
0.01 ≦ b ≦ 0.06
0.45 ≦ c ≦ 0.53
However, with respect to 100 parts by weight of the main component composition satisfying a + b + c = 1, at least one of Pr, Nd, Sm, La and Nb is contained in Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , It contains a total of 0.01 to 3 parts by weight in terms of La ₂ O ₃ and Nb ₂ O ₅ , and when Nb is contained, it is important to contain 0.01 to less than 1 part by weight in terms of Nb ₂ O _5. is there. The reasons for limiting the contents of a, b, c, and Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , La ₂ O ₃ and Nb ₂ O ₅ to the above ranges are as follows. .

  That is, the reason why 0.42 ≦ a ≦ 0.51 is set is that when 0.51 <a, the Q value decreases, or τf becomes negative and the absolute value of τf exceeds 50. . When a <0.42, the Q value decreases, τf increases positively, the absolute value of τf greatly exceeds 50, the curve of the temperature coefficient τf of the resonance frequency increases, and the linearity of the temperature drift It is because it falls. In particular, 0.43 <a <0.49 is desirable.

  In addition, 0.01 ≦ b ≦ 0.06 is set because, when 0.06 <b, the temperature coefficient τf of the resonance frequency increases positively, the absolute value of τf greatly exceeds 50, and the Q value decreases. When b <0.01, τf becomes negative and the absolute value of τf exceeds 50, or the curve of the temperature coefficient τf of the resonance frequency increases and the linearity of the temperature drift decreases. Because. In particular, 0.02 ≦ b ≦ 0.05 is preferable.

  Furthermore, 0.45 ≦ c ≦ 0.53 is set when 0.53 <c, the temperature coefficient τf of the resonance frequency becomes positive and the absolute value of τf greatly exceeds 50, or the resonance frequency This is because the curvature of the temperature coefficient τf increases and the linearity of the temperature drift decreases. This is because in the case of c <0.45, the Q value decreases or the relative dielectric constant decreases. In particular, the range of 0.46 ≦ c ≦ 51 is preferable.

The total Pr, Nd, Sm, La and Nb at least one or more of the at _{Pr 6 O 11, Nd 2 O} 3, Sm 2 O 3, La 2 O 3 and calculated _as Nb ₂ O ₅ 0.01 to 3 The reason for containing parts by weight is that when the amount is less than 0.01 parts by weight, the linearity of the temperature drift is low, and when the amount is more than 3 parts by weight, the rate of decrease in the Q value at high temperature (125 ° C.) is large. . When Nb is contained, it is contained in an amount of 0.01 part by weight or more and less than 1 part by weight in terms of Nb ₂ O ₅ because the linearity of the temperature drift is low when it is less than 0.01 part by weight. This is because the rate of decrease in the Q value at high temperature (125 ° C.) is large in the above case. In particular, it is desirable to contain a total of 0.05 to 2.5 parts by weight in terms of Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , La ₂ O ₃ and Nb ₂ O ₅ . When containing Nb it is desirably contains 0.05 to 0.8 parts by weight calculated as Nb ₂ O _5.

  In the present embodiment, the Q value indicates a value converted into a Qf value at 1 GHz from a certain relationship, that is, Q value generally established in microwave dielectrics × measurement frequency f = constant.

  Thus, the high frequency dielectric ceramic composition of the present embodiment has a high dielectric constant of about 16 to 24, a high Q value, a high linearity of temperature drift, and a high temperature with respect to a normal temperature (25 ° C.) Q value. There is an effect that the Q value retention of (125 ° C.) is 75% or more. By placing a dielectric ceramic composition having a high-temperature (125 ° C.) Q value retention ratio of 75% or higher with respect to the Q value at normal temperature (25 ° C.) in the dielectric resonator, the temperature around the resonator Since the output signal is not easily attenuated even if changes, an output signal with less noise can be obtained in a wide temperature range, and an excellent dielectric resonator can be obtained.

  The high frequency dielectric ceramic composition of the present embodiment is produced, for example, as follows. Using each powder of magnesium carbonate, calcium carbonate and titanium oxide as the starting material, weighed to the desired ratio described above, and then added pure water until the average particle size of the mixed material became 2.0 μm or less For 10 to 30 hours, wet mixing and pulverization are performed by a mill using zirconia balls or the like.

  The mixture is dried and calcined at 1000-1300 ° C. for 2-10 hours. To the obtained calcined product, praseodymium oxide, neodymium oxide, samarium oxide, lanthanum oxide and niobium oxide are added within the specific range described above, and mixed and pulverized. Further, a predetermined amount, for example, about 5% by weight of an organic binder for molding is added, and the particle size is adjusted, and the obtained powder is arbitrarily selected by a desired molding means such as a die press, cold isostatic pressing, extrusion molding, etc. After forming into a shape of the above, the binder removal treatment was performed in an oxidizing atmosphere such as air under the condition that the binder removal temperature was 600 ° C. or more and the holding time was 10 hours or more, and thereafter, the temperature was 1300 to 1400 ° C. Dielectric porcelain is obtained by firing in air for 10 hours.

  In the present embodiment, by using the above-described manufacturing method within a specific composition range, the curvature (temperature drift) of the temperature coefficient τf of the resonance frequency is 0 ± 3 (25 ± 85 ° C.). ppm / ° C.), that is, the linearity of temperature drift can be increased. In addition, the reduction rate of the Q value at a high temperature with respect to the Q value at room temperature can be reduced.

As a starting material of the dielectric ceramic composition for high frequency in this embodiment, in addition to oxides, oxides such as carbonates, acetates, nitrates, carbonates, hydroxides, etc. by heat treatment in an oxidizing atmosphere are used. A compound that can be generated may be used. Further, for Mg, Ca, and Ti, MgTiO ₃ and CaTiO ₃ compounds prepared by a sol-gel method or a hydrothermal method may be used.

  In this embodiment, Zr, Si, Ba, etc. may be mixed as inevitable impurities in the porcelain, but these may cause no problem in characteristics even if mixed in an amount of 0.4% by weight or less in terms of oxide.

  According to the dielectric ceramic composition for high frequency of this embodiment, the main component contains at least one of Pr, Nd, Sm, La and Nb, thereby having a high Q value and having a resonance frequency. It is possible to control the bend (temperature drift) of the temperature coefficient τf in the range of 0 ± 3 (ppm / ° C.) at 25 to 85 ° C., that is, to increase the linearity of the temperature drift. In addition, the reduction rate of the Q value at a high temperature with respect to the Q value at room temperature can be reduced.

  The high frequency dielectric ceramic composition of the present embodiment is most useful for a dielectric resonator. As a dielectric resonator of the present embodiment, a schematic diagram of a TE mode type dielectric resonator is shown in FIG. The resonator shown in FIG. 1 is configured by forming an input terminal 2 and an output terminal 3 on both sides of a metal case 1 and disposing a dielectric ceramic 4 having the above composition between these terminals 2 and 3. The As described above, the TE mode type dielectric resonator receives a microwave from the input terminal 2, and the microwave is confined in the dielectric ceramic 4 by reflection at the boundary between the dielectric ceramic 4 and the free space. Resonance occurs at a frequency of.

  This signal is electromagnetically coupled to the output terminal 3 and output. Although not shown, the high frequency dielectric ceramic composition of the present embodiment is applied to a coaxial resonator using a TEM mode, a strip line resonator, a TM mode dielectric ceramic resonator, and other resonators. Of course, it is also good.

Using each powder of high-purity magnesium carbonate (MgCO ₃ ), calcium carbonate (CaCO ₃ ) and titanium oxide (TiO ₂ ) as starting materials, weigh them so that they have the molar ratio shown in Table 1, and then add pure water. in addition, until the average particle diameter of the mixed raw material is 2.0μm or less, about 20 hours wet mixing by mill using ZrO ₂ balls were crushed.

The mixture was dried and calcined at 1200 ° C. for 2 hours. To the obtained calcined product, high-purity praseodymium oxide (Pr ₆ O ₁₁ ), neodymium oxide (Nd ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), and lanthanum oxide (La ₂ O ₃ ) Niobium oxide (Nb ₂ O ₅ ) was added, and wet mixing and pulverization were performed for about 20 hours with a mill using ZrO ₂ balls until the average particle size of the mixed raw material became 2.0 μm or less. The slurry was dried and further sized after adding 5% by weight of a binder, and the obtained powder was formed into a disk shape at a pressure of about 1 ton / cm ² . The obtained molded body was debindered in the air under the conditions of a debinding temperature of 800 ° C. and a holding time of 10 hours, and then baked in the air at a temperature of 1300 to 1500 ° C. for 8 hours.

  The obtained porcelain was polished and ultrasonically cleaned in acetone, dried at 150 ° C. for 1 hour, and then measured for relative dielectric constant εr and Q value at a measurement frequency of 8 to 10 GHz by a cylindrical resonator method at a room temperature of 25 ° C. did. Qf was converted into a Qf value at 1 GHz from a certain relationship of Q value × measurement frequency f = generally established for microwave dielectrics. Furthermore, the Q value at a high temperature of 125 ° C. was measured in the same manner, and the retention of the Q value at 125 ° C. with respect to the Q value at 25 ° C. was calculated.

  The temperature coefficient τf of the resonance frequency was measured in the range of 25 to 85 ° C. Further, a value obtained by subtracting τf of 55 to 85 ° C. from τf at 25 to 55 ° C. was defined as a bending (temperature drift) of τf.

  As is clear from Table 1, in the dielectric ceramic composition outside the scope of the present invention, the dielectric constant is low, the Q value is low, or the absolute value of τf exceeds 50, or τf The bending (temperature drift) exceeded 0 ± 3 ppm / ° C. In Table 1, * indicates a sample outside the scope of the present invention.

  In contrast, in the dielectric ceramic composition of the present invention, the relative dielectric constant is 20 to 23, the Q value is 80000 (at 1 GHz) or more, τf is within ± 50 (ppm / ° C.), and τf is bent (temperature drift). Is within 0 ± 3 (ppm / ° C.), the Q value at 125 ° C. with respect to the Q value at 25 ° C. has a holding ratio of 75% or more, and it can be seen that excellent dielectric properties can be obtained.

1 Metal Case 2 Input Terminal 3 Output Terminal 4 Dielectric Porcelain

Claims (5)

A high-frequency dielectric ceramic composition having a main component containing at least Mg, Ca, Ti as a metal element and Nb,
When the composition of the main component is expressed as aMgO · bCaO · cTiO ₂ by the molar ratio of the metal elements, the a, b and c are:
0.42 ≦ a ≦ 0.51
0.01 ≦ b ≦ 0.06
0.45 ≦ c ≦ 0.53
(However, a + b + c = 1)
A dielectric ceramic composition for high frequency, wherein a Qf value at 1 GHz is 79000 or more. _{2. The} dielectric ceramic composition for high frequency according to claim 1, wherein the Nb is contained in an amount of 0.01 part by weight or more and less than 0.1 part by weight in terms of Nb ₂ O _{5 with} respect to 100 parts by weight of the main component. It contains at least one or more rare earth elements of Pr, Nd, Sm, and La, and contains a total of 0.01 to 3 parts by weight of the rare earth elements and the Nb (where Pr is converted to Pr ₆ O ₁₁ , Nd is Nd ₂ O ₃ in terms, Sm is Sm ₂ O ₃ in terms, La is La ₂ O ₃ in terms, Nb is high-frequency dielectric as claimed in claim 2, wherein Nb ₂ O ₅ in terms) that Body porcelain composition. The high frequency dielectric ceramic composition according to any one of claims 1 to 3, wherein a Q value at 125 ° C is 75% or more of a Q value at 25 ° C. A dielectric ceramic comprising the dielectric ceramic composition for high frequency according to any one of claims 1 to 4 is disposed between a pair of input / output terminals, and is operated by electromagnetic field coupling. Body resonator.

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