JP2012116684A - Dielectric ceramic and dielectric filter including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide dielectric ceramic which indicates high specific dielectric constant εr and Qf value and an excellent temperature coefficient of a resonance frequency, and a dielectric filter capable of stably maintaining excellent performance over a long period of time even in a location where the temperature difference is significant.SOLUTION: For the dielectric ceramic, when the composition formula is expressed as aBaO/bNdO/c[{1-(x/2)-(y/2)}TiO+1/2xNbO+1/2yAlO], a, b, c, x and y satisfy 13.5≤a≤16.1, 17.6≤b≤19.4, 64.5≤c≤68.8, 0.01≤x≤0.15, 0.01≤y≤0.15, and a+b+c=100. The dielectric ceramic indicates the high specific dielectric constant εr and Qf value and the excellent temperature coefficient of a resonance frequency, and the dielectric filter 1 including an input terminal 3 and an output terminal 4 electromagnetically coupled with the dielectric ceramic 5 is capable of stably maintaining the excellent performance over a long period of time even in a location where the temperature difference is significant.

Description

  The present invention relates to a dielectric ceramic having a high relative dielectric constant εr (ratio to a vacuum dielectric constant εo) and a high quality factor Qf value in a high-frequency region including microwaves, millimeter waves, and the like, and a filter including the dielectric ceramic.

In recent years, with the rapid development of mobile communication market such as mobile phones and personal computers, dielectric ceramics used for capacitors and so on are required to have high dielectric constant, but dielectric loss is small, In addition, it is required to satisfy various conditions such as a good temperature coefficient. Recently, the frequency of use has shifted to a higher frequency band due to diversification of functions used, and in particular, dielectric characteristics in a high frequency region (800 MHz to 2 GHz) have been required.

Therefore, for example, in Patent Document 1, the composition formula xBaO-y ((1-a) Nd ₂ O ₃ · aS
m ₂ O ₃ ) -zTiO ₂ (where 14 <x <18, 11 <y <15, 67 <z <75, 0.07 <a <0.6, x + y + z = 100 (molar ratio)) On the other hand, a dielectric ceramic composition containing Bi ₂ O ₃ as subcomponents in a proportion of 10 to 20%, Al ₂ O ₃ in a proportion of 0.1 to 1.5% and MnO in a proportion of 0.01 to 1.5% has been proposed.

Japanese Unexamined Patent Publication No. 2003-292373

However, in the BaO—Nd ₂ O ₃ —Sm ₂ O ₃ —TiO ₂ based dielectric ceramic composition described in Patent Document 1, the temperature characteristics of the resonance frequency are obtained by adding Bi ₂ O ₃ and Al ₂ O _3. Although τf could be brought close to 0 ppm / ° C., the Qf value could not be improved.

  An object of the present invention is to provide a dielectric ceramic having a high dielectric constant εr, a high Qf value, and a temperature coefficient τf of a stable resonance frequency close to 0 ppm / ° C., and a dielectric filter including the dielectric ceramic. It is.

The dielectric ceramic of the present invention has a composition formula of aBaO · bNd ₂ O ₃ · c [{1- (x / 2)-(y / 2)} TiO ₂ + 1 / 2xNb ₂ O ₅ + 1 / 2yAl ₂ O ₃ ]. When
a, b, c, x, y satisfy 13.5 ≦ a ≦ 16.1, 17.6 ≦ b ≦ 19.4, 64.5 ≦ c ≦ 68.8, 0.01 ≦ x ≦ 0.15, 0.01 ≦ y ≦ 0.15, a + b + c = 100 It is what.

  The dielectric filter according to the present invention includes the dielectric ceramic, an input terminal that is electromagnetically coupled to the dielectric ceramic and receives an electric signal from the outside, and is electromagnetically coupled to the dielectric ceramic and the dielectric ceramic. And an output terminal that selectively outputs an electrical signal corresponding to the resonance frequency of the body ceramic.

According to the dielectric ceramic of the present invention, the composition formula is aBaO · bNd ₂ O ₃ · c [{1- (
x / 2)-(y / 2)} TiO ₂ + 1 / 2xNb ₂ O ₅ + 1 / 2yAl ₂ O ₃ ], a, b, c, x, y are 13.5 ≦ a ≦ 16.1, 17.6 ≦ If b ≦ 19.4, 64.5 ≦ c ≦ 68.8, 0.01 ≦ x ≦ 0.15, 0.01 ≦ y ≦ 0.15, a + b + c = 100, a high dielectric constant and a high Qf value can be obtained, and the temperature dependence of the resonance frequency Can be stabilized.

  In addition, according to the dielectric filter of the present invention, a high dielectric constant and a high Qf value can be obtained, and the dielectric ceramic that can stabilize the temperature dependence of the resonance frequency is coupled to the dielectric ceramic. Since it has an input terminal for inputting an electric signal from the outside and an output terminal for selectively outputting an electric signal corresponding to the resonance frequency of the dielectric ceramic by being electromagnetically coupled to the dielectric ceramic, Good performance can be maintained stably over a long period of time even in a severe place.

It is a schematic diagram which shows the cross section of the dielectric material filter of this embodiment.

  Below, the example of embodiment of the dielectric ceramic of this embodiment and a dielectric filter provided with the same is demonstrated.

The dielectric ceramic of the present embodiment has a composition formula of aBaO · bNd ₂ O ₃ · c [{1- (x / 2) − (y / 2)} TiO ₂ + 1 / 2xNb ₂ O ₅ + 1 / 2yAl ₂ O _3. ], A, b, c, x, y are 13.5 ≦ a ≦ 16.1, 17.6 ≦ b ≦ 19.4, 64.5 ≦ c ≦ 68.8, 0.01 ≦ x ≦ 0.15, 0.01 ≦ y ≦ 0.15, a + b + c = 100 It is characterized by satisfying.

Here, when a, b, c, x and y satisfy the above numerical range, it is considered that a main crystal in which Nb and Al are dissolved is formed, and by this main crystal phase, the relative dielectric constant εr and The quality factor Qf value (product of the Q value and the resonance frequency f) is high, and the absolute value of the temperature coefficient τf of the resonance frequency tends to be small. For example, the relative dielectric constant εr can be set to 70 or more, the Qf value can be set to 12000 GHz or more, and the temperature coefficient τf of the resonance frequency can be set to −10 to +20 ppm / ° C.

Moreover, it is preferable that the dielectric ceramic of this embodiment contains 3 mass% or less (except 0 mass%) of manganese in conversion of an oxide with respect to 100 mass% of components of a composition formula.

For dielectric ceramics, manganese is converted to oxide with respect to 100% by mass of the component in the composition formula.
When containing less than mass% (excluding 0 mass%), oxygen generated by change in valence of manganese oxide during firing enters oxygen defects in dielectric ceramics, thereby suppressing oxygen defects generated in dielectric ceramics Thus, the Qf value can be increased. Moreover, Qf value can be raised more by including manganese in 0.1-2 mass% mass% in conversion of an oxide.

  Regarding the content of each component contained in the dielectric ceramic, a part of the dielectric ceramic is pulverized, the obtained powder is dissolved in a solution such as hydrochloric acid, and then ICP (Inductively Coupled Plasma) emission spectroscopy. It can be obtained by measuring using an analyzer (manufactured by Shimadzu Corporation: ICPS-8100) and converting the metal content of each component obtained into an oxide.

  Moreover, it is preferable that the dielectric ceramic of this embodiment has a surface and internal average void ratio of 5% or less.

In the dielectric ceramic according to the present embodiment, by setting the average void ratio to 5% or less, the relative dielectric constant εr and the quality factor Qf can be maintained high, and the dielectric characteristics are easily stabilized. Furthermore, when the average void ratio of the dielectric ceramic is 5% or less, the density of the dielectric ceramic is high, so that the mechanical characteristics can be kept high. Further, it is preferable to set the average void ratio to 3% or less because the relative dielectric constant εr and the quality factor Qf can be maintained higher and the dielectric characteristics are more easily stabilized.

  In addition, what is necessary is just to obtain | require an average void ratio as follows, for example.

  First, several places on the ceramic surface and internal cross section of dielectric ceramics were photographed or photographed with a metal microscope or SEM (Scanning Electron Microscope) adjusted to an arbitrary magnification so that the range of 100 μm × 100 μm could be observed, By analyzing this photograph or image with an image analyzer, the ratio of the void area per unit area is obtained as the void ratio. An average void ratio can be obtained by averaging the void ratios at several locations. Further, as an image analysis apparatus, for example, LUZEX-FS manufactured by Nireco Corporation may be used.

  Next, the manufacturing method of the dielectric ceramic of this embodiment is demonstrated. For example, it can be produced by the following steps (1) to (7).

(1) As raw materials, high-purity barium carbonate (BaCO ₃ ) of 99.5% or more, neodymium oxide (Nd ₂ O ₃ ), titanium oxide (TiO ₂ ), niobium oxide (Nb ₂ O ₅ ), and aluminum oxide (Al ₂ Prepare each powder of O ₃ ). Then, BaCO ₃ , Nd ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ and Al ₂ O ₃ are weighed so as to have a desired ratio. Next, pure water is added to the weighed powder and pulverized by a ball mill using zirconia balls or the like for 1 to 50 hours until the average particle size of the mixed raw material becomes 2.0 μm or less to obtain a mixture.

  (2) After drying this mixture, it is calcined at 1000-1300 ° C. for 1-10 hours to obtain a calcined raw material. If the calcining temperature is less than 1000 ° C., the synthesis does not proceed and favorable characteristics cannot be obtained.

(3) The obtained calcined raw material is pulverized with a ball mill or the like until the average particle diameter becomes 0.5 to 3 μm, and the resulting mixture is transferred to a container. This calcined raw material is described in ASTM E 11-61. The classified calcined powder is obtained by passing through a mesh sieve having a particle size number of 80. Note that for the pulverization of the calcined raw material, a mass collider manufactured by Masuko Sangyo Co., Ltd. may be used instead of the ball mill.

(4) After adding pure water to the calcined powder obtained in (3), mixing is performed by a ball mill using zirconia balls or the like for 1 to 30 hours until the average particle size becomes 2.0 μm or less.

(5) A binder of 3 to 10% by mass, for example, paraffin wax, acrylic polymer, urethane polymer, polyvinyl alcohol (PVA), or polyethylene glycol (PEG), based on 100 parts by weight of the calcined powder. After that, granulation is performed by, for example, a spray drying method, and the obtained granulated body is formed into an arbitrary shape by, for example, a die pressing method or a cold isostatic pressing method. Moreover, a clay may be produced using the obtained granulated body and formed into an arbitrary shape using a general extrusion molding method.

  (6) The obtained molded body is held in an air atmosphere at 1350 ° C. to 1550 ° C. for 1 to 10 hours and fired to obtain a fired body. More preferably, firing is performed at 1400 to 1500 ° C. In such a firing condition, since the solid solution of Nb and Al is easily promoted in the main crystal phase and the amount of foreign phases other than the main crystal phase tends to be reduced, the relative permittivity and the Qf value are increased. Also, the temperature dependence of the resonance frequency of the dielectric ceramic is likely to be stable.

(7) If necessary, the obtained fired body in a gas containing 5 to 30% by volume of oxygen,
Heat treatment is performed at a temperature of 900 to 1500 ° C. and a pressure of 0.1 to 300 MPa for 30 minutes to 100 hours. More preferably, heat treatment is performed at a temperature of 1000 to 1300 ° C. and a pressure of 0.1 to 100 MPa for 1 to 60 hours.

  Next, an example of a dielectric filter including the dielectric ceramic according to the present embodiment will be described below.

  The dielectric filter of the present embodiment includes the above-described dielectric ceramics, an input terminal that is electromagnetically coupled to the dielectric ceramics and receives an electric signal from the outside, and an electromagnetic field coupled to the dielectric ceramics. And an output terminal for selectively outputting an electrical signal corresponding to the resonance frequency.

  FIG. 1 is a schematic view showing a cross section of the dielectric filter of the present embodiment.

  As shown in FIG. 1, the TE mode type dielectric filter 1 of this embodiment includes a metal case 2, an input terminal 3, an output terminal 4, a ceramic body 5, and a mounting table 6. The metal case 2 is made of lightweight metal such as aluminum, and the input terminal 3 and the output terminal 4 are provided on opposite sides of the inner wall of the metal case 2. The ceramic body 5 is made of the dielectric ceramic of the present embodiment. The ceramic body 5 is disposed between the input terminal 3 and the output terminal 4, and is electromagnetically coupled to the input terminal 3 and the output terminal 4, respectively. In such a dielectric filter 1, a magnetic field is generated at the input terminal 3 in the metal case 2 by inputting an electric signal from the outside to the input terminal 3. Due to the magnetic energy, the ceramic body 5 resonates at a specific frequency to generate a magnetic field. This magnetic energy generates a magnetic field at the output terminal 4 to cause a current to flow, and an electric signal is output from the output terminal 4. Thus, the dielectric filter 1 can selectively output an electrical signal corresponding to the resonance frequency of the dielectric ceramic.

  The mode is not limited to the TE mode, and may be a TM mode, a TEM mode, or a multiple mode. The configuration of the dielectric filter 1 is not limited to the configuration described above, and the input terminal 3 and the output terminal 4 may be directly provided on the ceramic body 5. The ceramic body 5 is a resonance medium having a predetermined shape made of the dielectric ceramic according to the present embodiment. The shape of the ceramic body 5 is a cylindrical body, a rectangular parallelepiped, a cube, a plate-like body, a disc, a cylinder, a polygonal column, or other resonance. Any solid shape that can be used. The frequency of the input high-frequency signal is about 500 MHz to 500 GHz, and the resonance frequency is preferably about 2 GHz to 80 GHz in practice.

  The dielectric filter according to the present embodiment includes the dielectric ceramic according to the present embodiment having a high relative dielectric constant εr and a Qf value and a stable temperature dependence of the resonance frequency as a filter. Even in a place, good performance can be maintained stably over a long period of time.

  Moreover, the dielectric ceramic of the present embodiment is used for a dielectric substrate for MIC (Monolithic IC), a dielectric waveguide, a dielectric antenna, or a dielectric of a multilayer ceramic capacitor, in addition to various dielectric filter materials. May be.

Samples were prepared by variously changing the molar ratios a, b, c, x and y of the BaO—Nd ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ —Al ₂ O ₃ based material according to the present embodiment, and the relative dielectric constant εr, quality factor Qf value, and temperature coefficient τf of resonance frequency of 25 to 85 ° C. were measured. Details of the manufacturing method and the characteristic measuring method will be described below.

As a starting material, BaCO ₃ , Nd ₂ O ₃ , TiO ₂ , Nb ₂ O having a purity of 99.5% by mass or more
₅ and Al ₂ O ₃ were prepared.

Next, each material is weighed so as to have the ratio shown in Table 1. _Then, a mixture of _{BaCO 3, Nd 2 O 3,} TiO 2, Nb 2 O 5 and _Al 2 _{O 3,} were charged into a ball mill, addition of pure water in a ball mill. Then, it grind | pulverized with the ball mill using a zirconia ball until the average particle diameter of the mixed raw material became in the range of 0.5-2.0 micrometers, and obtained the mixture.

Then, after drying the obtained mixture, calcined at 1100 ° C. to obtain a calcined raw material, and the calcined raw material was passed through a mesh sieve having a particle size number of 80 described in ASTM E 11-61, and classified. After the obtained calcined powder is obtained, pure water is added to the calcined powder and pulverized with a ball mill using zirconia balls or the like for 1 to 30 hours so that the average particle size becomes 0.5 to 2 μm. , Sample No. 1 shown in Table 1. 1 to 31 slurries were obtained.

  Next, 3 to 10% by weight of polyvinyl alcohol was added to the slurry, and the mixture was mixed for a predetermined time. The slurry was sprayed and granulated with a spray dryer to obtain a secondary material. This secondary material was molded into a cylindrical body having a diameter of 20 mm and a height of 15 mm by a die press molding method to obtain a molded body.

  The obtained molded body was fired by holding at 1400 ° C. to 1500 ° C. for 2 hours in an air atmosphere. 1-31 were obtained. These samples are those obtained by polishing the upper and lower surfaces and part of the side surfaces after firing and ultrasonically cleaning in acetone.

  Next, these sample Nos. 1 to 31 were evaluated for dielectric properties. Evaluation of the dielectric characteristics was conducted using sample No. 1 to 31 were used to measure the relative dielectric constant εr and Q value at a measurement frequency of 4 to 5 GHz by the dielectric cylindrical resonator method (international standard IEC61338-1-3 (1999)). The Q value is converted to a quality factor Qf value represented by the product of the measurement frequency f. Further, the resonance frequency in the temperature range of 25 to 85 ° C. was measured, and the temperature coefficient τf of the resonance frequency of 25 to 85 ° C. was calculated based on the resonance frequency at 25 ° C. The sample is set in a metal cavity to which an input terminal and an output terminal are connected. After setting the metal cavity in a thermostatic chamber, the resonance frequency observed at a desired temperature is measured, and 25 to 85 ° C. The temperature coefficient τf of the resonance frequency can be calculated by the following equation.

τf = (f ₈₅ −f ₂₅ ) / f ₂₅ / (85−25)
Here, f ₈₅ is a resonance frequency measured at 85 ° C., and f ₂₅ is a resonance frequency measured at 25 ° C.

  The results are shown in Table 1.

From Table 1, a, b, c, x, and y are 13.5 ≦ a ≦ 16.1 and 17.6 ≦ b ≦ in the values of the relative dielectric constant εr, the quality factor Qf, and the temperature coefficient τf of the resonance frequency of 25 to 85 ° C. No. 19.4, 64.5 ≦ c ≦ 68.8, 0.01 ≦ x ≦ 0.15, 0.01 ≦ y ≦ 0.15, a + b + c = 100 (rounded to the nearest decimal place) 2 to 5, 8 to 11, 14 to 17, 20 to 24, and 27 to 30 have a relative dielectric constant εr of 70 or more, a quality factor Qf value of 12000 GHz or more, and a temperature coefficient τf of −10 ppm / ° C. or more and 20 ppm / ° C. or less. Tend to show high dielectric properties.

In addition, a, b, c, x, y are 14.3 ≦ a ≦ 15.2, 18.2 ≦ b ≦ 18.8, 66.0 ≦ c ≦ 67.5, 0.04 ≦ x ≦ 0.11, 0.04 ≦ y ≦ 0.11, a + b + c = 100 Satisfy rounding)
Sample No. In particular, 3, 4, 9, 10, 15, 16, 21 to 23, 28, and 29 have a high relative dielectric constant εr and a high Qf value, and the absolute value of the temperature coefficient τf tends to be small.

Next, the manganese content of the _{BaO-Nd 2 O 3 -TiO 2} -Nb 2 O 5 -Al 2 O 3 based material according to the present embodiment, tests were conducted to confirm the effects of the dielectric properties.

Preparation of the sample used for the test is the amount shown in Table 2 of manganese carbonate (MnCO ₃ ) having a purity of 99.5 or more prepared in advance when mixing the two calcining raw materials at a firing temperature of 1450 ° C. and a firing time of 2 hours. Except for the addition method, the production method was the same as in Example 1. Moreover, about test composition, sample No. of Example 1 was added except adding manganese. 3 was used. Sample No. manufactured For 32 to 42, the relative dielectric constant εr, the Q value, and the temperature coefficient τf of the resonance frequency were measured by the same measurement method as in Example 1.

  The results are shown in Table 2.

As shown in Table 2, when the total manganese content in the BaO—Nd ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ —Al ₂ O ₃ material is 3.0 mass% or less, the sample No. Q compared to 3
The f value tended to be higher.

In addition, sample No. According to 32-37, the manganese content in the BaO—Nd ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ —Al ₂ O ₃ material is 0.05% by mass or more and 1.0% by mass or less in terms of oxide. The quality factor Qf value tended to be a high value of 13800 or more.

Next, a test for confirming the influence of the average void ratio of the BaO—Nd ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ —Al ₂ O ₃ material on the dielectric properties was performed.

  The sample used for the test was manufactured by the same manufacturing method as in Example 1 except that the firing time was changed to 1450 ° C. and the firing holding time was changed to 10, 8, 6, 4, 3, and 2 hours, respectively. In addition, the average void ratio increases as the firing holding time increases. Sample No. manufactured For 43 to 48, the relative dielectric constant εr, the quality factor Qf value, and the temperature coefficient τf of the resonance frequency of 25 to 85 ° C. were measured by the same measurement method as in Example 1. For the average void ratio, an SEM photograph in which a 100 μm × 100 μm range of the surface of the dielectric ceramics can be observed, and this photograph is analyzed by an image analyzer (LUZEX-FS manufactured by Nireco). The void ratio was calculated by calculating the average value of void ratios at arbitrary five locations, with the ratio of the area occupied by the voids as the void ratio.

  The results are shown in Table 3.

  As shown in Table 3, Sample No. Since 43 to 47 have an average void ratio of 5% or less, the relative dielectric constant εr, the quality factor Qf value, the temperature coefficient τf of the resonance frequency of 25 to 85 ° C. is high, and the quality factor Qf value is particularly high as 12800 or more. The value is shown.

1: Dielectric filter 2: Metal case 3: Input terminal 4: Output terminal 5: Ceramic body 6: Mounting table

Claims (3)

The composition formula is aBaO · bNd ₂ O ₃ · c [{1- (x / 2) − (y / 2)} TiO ₂ + 1 /
2xNb ₂ O ₅ + 1 / 2yAl ₂ O ₃ ], a, b, c, x, y are 13.5 ≦ a ≦ 16.1, 17.6 ≦ b ≦ 19.4, 64.5 ≦ c ≦ 68.8, 0.01 ≦ x ≦ A dielectric ceramic characterized by satisfying 0.15, 0.01 ≦ y ≦ 0.15, and a + b + c = 100. 2. The dielectric ceramic according to claim 1, comprising 3 mass% or less (excluding 0 mass%) of manganese in terms of oxide with respect to 100 mass% of the component of the composition formula.   3. The dielectric ceramic according to claim 1, wherein the dielectric ceramic is electromagnetically coupled to the dielectric ceramic and an electric signal is input from the outside, and the dielectric ceramic is electromagnetically coupled to the dielectric ceramic. A dielectric filter comprising an output terminal for selectively outputting an electrical signal corresponding to a resonance frequency of ceramics.

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