JP2009263166A - Dielectric porcelain and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric ceramic having excellent dielectric characteristics even in a case where a dielectric ceramic is large in a sample made of a sintered body obtained by firing a molded body having a diameter of 10 mm and a thickness of 5 mm. It was unclear whether this requirement could be met.
When Al in the dielectric ceramic 4 contains 0.007% by mass or less (excluding zero) in terms of Al ₂ O ₃ and the concentration of Al in the inside is 1, the dielectric ceramic 4 The ratio of the Al concentration in the vicinity of the surface is 0.5 to 2, and the average pore diameter is 8 μm or less.
[Selection] Figure 1

Description

  The present invention relates to a novel dielectric ceramic having a high relative permittivity and a high Q value in a high frequency region such as a microwave and a millimeter wave, and more particularly to a high frequency electronic component such as a dielectric resonator, a filter, a capacitor, or an MIC. The present invention relates to a dielectric ceramic suitable for a dielectric substrate for millimeter wave and a waveguide for millimeter wave.

  Conventionally, dielectric ceramics are widely used for dielectric resonators, dielectric substrates for MICs, and the like in high frequency regions such as microwaves and millimeter waves. Recently, dielectric lines have been applied to millimeter wave waveguides. The required characteristics are as follows: (1) Since the wavelength of the electromagnetic wave propagating in the dielectric is shortened to (1 / εr) 1/2, the dielectric constant is large with respect to the demand for miniaturization. 2) Low dielectric loss in the high frequency region, that is, high Q, (3) Small change in resonance frequency with respect to temperature, that is, temperature dependency of relative dielectric constant εr is small and stable. The three characteristics are mainly listed.

Patent Document 1 discloses a dielectric ceramic composition composed of a complex oxide composed of BaO, SrO, MgO, WO ₃ and RE (rare earth element) as satisfying these three characteristics.
JP-A-12-87881

  The characteristics of the dielectric ceramic described in the example of Patent Document 1 are as follows. In a sample made of a sintered body obtained by firing a molded body having a diameter of 10 mm and a thickness of 5 mm, the relative dielectric constant εr is 20. 1 to 25.3, Qf was 101000 to 231000, and temperature characteristic τf of the resonance frequency was −11.2 to 41.3 ppm / ° C. Patent Document 1 describes that a molded product having a diameter of 10 mm and a thickness of 5 mm satisfies this characteristic. In the dielectric ceramic described in Patent Document 1, it is difficult to satisfy this characteristic in a molded body having a diameter larger than 10 mm and a thickness of 5 mm.

  An object of the present invention is to provide a dielectric ceramic having relatively excellent dielectric characteristics even when the size of the dielectric ceramic is relatively large, and a method for manufacturing the same.

In order to solve the above problems, the present invention provides a dielectric ceramic having a perovskite crystal containing Ba, Sr, Mg, W and Yb as a main crystal phase, wherein Al inside the dielectric ceramic is Al _2. When the content is 0.007% by mass or less in terms of O ₃ and the mass% of Al in the dielectric ceramic is 1, the ratio of mass% of Al in the vicinity of the surface of the dielectric ceramic is 0.5 to A dielectric ceramic is provided.

The present invention also provides a dielectric porcelain having a perovskite-type crystal containing Ba, Sr, Mg, W and Yb as a main crystal phase, which is placed on a firing jig and fired. A method for manufacturing a dielectric ceramic, wherein the Al content in the firing jig is 0.9% by mass or less in terms of Al ₂ O ₃ , is also provided.

  The present invention also provides a dielectric resonator characterized in that the above-described dielectric ceramic is disposed between a pair of input / output terminals and is operated by electromagnetic coupling.

  The dielectric ceramic of the present invention has a relatively large sintered body size and relatively high dielectric characteristics.

  The dielectric ceramic of the present invention also has a relatively high Qf value.

  The method for manufacturing a dielectric ceramic according to the present invention can manufacture a dielectric ceramic having a relatively large size and relatively good dielectric characteristics.

  The dielectric resonator of the present invention can also provide a dielectric resonator having excellent dielectric characteristics.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The dielectric ceramic of the present invention is a dielectric ceramic having a main crystal phase of a perovskite crystal containing Ba, Sr, Mg, W and Yb, and contains Al in an amount of 0.007% by mass or less (excluding zero). And the ratio of the Al concentration in the vicinity of the surface of the dielectric ceramic is 0.5 to 2, where the Al concentration in the dielectric ceramic is 1.

  Here, the surface of the dielectric ceramic means the surface of the dielectric ceramic and the vicinity thereof. Preferably, the surface of the dielectric ceramic means the surface of the dielectric ceramic and the vicinity of less than 2 mm from the surface.

  The inside of the dielectric ceramic preferably refers to a region of a portion that is 2 mm or more away from the surface of the dielectric ceramic. In the case where the shape of the dielectric ceramic is a disk, a region 2 mm or more away from the center of one of the main surfaces in the depth direction is the interior of the dielectric ceramic. In the case where the shape of the dielectric ceramic is a cylinder, a region 2 mm or more away from the center of one end face (plane) of the cylinder in the depth direction is the inside of the dielectric ceramic. When the shape of the dielectric porcelain is a cylinder, the central portion in the thickness direction between the inner peripheral surface and the outer peripheral surface, and a region away from any one end surface by 2 mm or more in the depth direction is a dielectric. Inside of porcelain. When the shape of the dielectric ceramic is a substantially cubic or a substantially rectangular parallelepiped, a region 2 mm or more away from any one surface in the depth direction is the inside of the dielectric ceramic.

  By setting the Al content to 0.007% by mass or less, the temperature during sintering can be made relatively low, and the Qf can be made relatively high. Moreover, since Al is contained, εr can be made relatively large.

  Further, when the Al concentration in the dielectric ceramic is set to 1, the sintering temperature is relatively lowered by setting the Al concentration ratio in the vicinity of the surface of the dielectric ceramic to 0.5-2. The sinterability can be made relatively high. Further, Qf can be relatively improved by relatively increasing the size of the sintered body.

The Al content can be measured by ICP emission spectroscopy. Specifically, it can be measured by the following method. Dielectric porcelain is pulverized in a cemented mortar and used as an analysis sample. To 0.1 g of this sample, 2 g of boric acid and 3 g of sodium carbonate are added and melted, and dissolved in a hydrochloric acid solution. The obtained solution is quantitatively analyzed with an ICP emission spectroscopic analyzer, for example, ICPS-800 manufactured by Shimadzu Corporation, and the Al content is measured. The Al content is converted to the Al ₂ O ₃ content.

  When the concentration of Al in the dielectric ceramic is set to 1, the ratio of Al concentration in the vicinity of the surface of the dielectric ceramic can be measured by ICP emission spectroscopy as follows.

  When measuring the Al content on the surface of the dielectric ceramic, an analysis sample is obtained by cutting out the surface region. When the shape of the dielectric ceramic is a disk, a cylinder, or a cylinder, the outer peripheral surface is preferably used as the analysis sample.

  When measuring the content of Al in the dielectric ceramic, the sample cut out from the dielectric ceramic is used as the analysis sample. In the case where the shape of the dielectric ceramic is a disk, a cylinder, or a cylinder, it is preferable that the inside is 2 mm or more from the main plane as an analysis sample.

  The dielectric ceramic preferably has an average pore diameter of 8 μm or less. The reason why the porosity of the dielectric ceramic is preferably 8 μm or less is as follows.

  An increase in porosity results in a decrease in dielectric constant. In the dielectric ceramic according to the present embodiment, the relative permittivity εr can be made relatively high by setting the average pore diameter to 8 μm or less.

  The dielectric ceramic of the present invention more preferably has an average pore diameter of 5 μm or less. This is because even if the firing temperature further changes, εr is prevented from fluctuating.

The average pore diameter can be measured by the following method. An analysis sample is obtained by mirror polishing a dielectric ceramic. An image obtained by observing the analysis sample with a metal microscope at a magnification of about 100 times is captured by a CCD camera. The average pore diameter of the pores shown in this image is measured by an image analyzer. As the image analysis apparatus, for example, LUZEX FS, LUZEX SE manufactured by Nireco Corporation can be used. The measurement conditions when the image analysis apparatus is used are a measurement area of 9 × 10 ⁻² mm ^{2 on} the surface of the analysis sample, a measurement count of 10 times, and a total measurement area of 9 × 10 ⁻¹ mm ² . When LUZEX FS is used, the lamp voltage is preferably 5V. In the present invention, the average pore diameter refers to the average pore diameter inside the dielectric ceramic.

  The dielectric ceramic of the present invention preferably has an average crystal grain size of 3 to 4.5 μm or less in order to particularly improve Qf. By setting the average crystal grain size to 3 to 4.5 μm or less, the sinterability can be made relatively high and Qf can be made relatively improved.

The average crystal grain size can be measured by the following method. An analysis sample is obtained by mirror polishing a dielectric ceramic. An image obtained by observing the analysis sample with a metal microscope at a magnification of about 400 times is captured by a CCD camera. The average pore diameter of the pores shown in this image is measured by an image analyzer. As the image analysis apparatus, for example, LUZEX FS, LUZEX SE manufactured by Nireco Corporation can be used. The measurement conditions when the image analysis apparatus is used are generally as follows. That is, the measurement area of the analysis sample surface is 5.6 × 10 ⁻³ mm ² , the number of measurements is 3, and the total measurement area is 1.68 × 10 ⁻² mm ² . When LUZEX FS is used, the lamp voltage is preferably 5V. The average crystal grain size in the present invention refers to the average crystal grain size inside the dielectric ceramic.

The dielectric ceramic according to the present invention has a composition formula based on the molar ratio of each metal element oxide of Ba, Sr, Mg, W, and Yb as aBaO · bSrO · cMgO · dWO ₃ · eYb ₂ O _3. , B, c, d, e are 0.35 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.25, 0.10 ≦ c ≦ 0.30, 0.15 ≦ d ≦ 0.35, It is preferable that 0.01 ≦ e ≦ 0.20 and a + b + c + d + e = 1 are satisfied. The reason why a, b, c, d, and e are preferably in the above ranges is as follows.

  The reason why 0.35 ≦ a ≦ 0.55 is preferable is that a particularly high Qf value is obtained when 0.35 ≦ a ≦ 0.55. In particular, 0.40 ≦ a ≦ 0.50 is preferable.

  The reason why 0.01 ≦ b ≦ 0.25 is preferable is that, when 0.01 ≦ b ≦ 0.25, the temperature dependency of εr is small, so that εr hardly changes even if the temperature changes. In particular, 0.01 ≦ b ≦ 0.15 is preferable.

  0.10 ≦ c ≦ 0.30 is preferable because a high Qf value is obtained when 0.10 ≦ c ≦ 0.30. In particular, 0.15 ≦ c ≦ 0.25 is preferable.

  The reason why 0.15 ≦ d ≦ 0.35 is preferable is that a high Qf value is obtained when 0.15 ≦ d ≦ 0.35. In particular, 0.20 ≦ d ≦ 0.30 is preferable.

  The reason why 0.01 ≦ e ≦ 0.20 is preferable is that the temperature dependency of εr is small when 0.01 ≦ e ≦ 0.20. In particular, 0.01 ≦ e ≦ 0.10 is preferable.

The dielectric ceramic of the present invention preferably contains 0.01 to 0.2% by mass of Mn as a metal element in terms of MnO ₂ . By containing 0.01 to 0.2% by mass of Mn as a metal element in terms of MnO ₂ , the sinterability can be made relatively good and the Qf value can be relatively improved.

The dielectric ceramic of the present invention has an X-ray diffraction peak intensity attributed to the (112) plane of BaWO ₄ having a (220) plane of a perovskite crystal containing P1, Ba, Sr, Mg, W and Yb. When the X-ray diffraction peak intensity attributed to is P2, the ratio f = P1 / P2 is preferably 0.024 or less. Thereby, a high Qf value is obtained. In particular, f is preferably 0.013 or less. As for the crystal structure of the BaWO ₄ , for example, JCPDS-ICDD No. 43-646 and the like are described. The crystal structure of the perovskite crystal containing Ba, Sr, Mg, W and Yb is, for example, JCPDS-ICDD No. 43-646. Here, JCPDS-ICDD is a powder data file (JCPDS, abbreviated as JCPDS) issued by the International Committee for Diffraction Data (abbreviated as ICDD). Powder Data File).

  Analysis by X-ray diffraction of a dielectric ceramic can be performed using an X-ray diffraction apparatus. A candidate for the X-ray diffraction apparatus is PW3050 manufactured by Spectris Co. Measurement conditions are diffraction angle 2θ = 10-80 °, X-ray output; 40 Kv: 50 mA, scan speed: 0.02, step: 0.01, time: 2.0, MASK: 15 mm, detector: high, rotation Yes. The X-ray diffraction apparatus used for X-ray diffraction may be RINT series manufactured by Rigaku Corporation, RINT-TTRIII, or the like.

A method for manufacturing a dielectric ceramic according to the present invention will be described. In the method for manufacturing a dielectric ceramic according to the present invention, a molded body containing a perovskite crystal containing Ba, Sr, Mg, W and Yb as a main component is placed on a firing jig and fired, and Ba, Sr , Mg, W and Yb, a manufacturing method for manufacturing a dielectric ceramic having a perovskite crystal as a main crystal phase, wherein the Al content in the firing jig is 0 in terms of Al ₂ O ₃ .9% by mass or less. Accordingly, it is possible to provide a manufacturing method capable of obtaining a dielectric ceramic having a high Qf even when the size of the dielectric ceramic is large.

When the composition formula based on the molar ratio of the metal elements contained in the molded body is expressed as aBaO · bSrO · cMgO · dWO ₃ · eYb ₂ O ₃ , the a, b, c, d and e are 0.35 ≦ a ≦ 0.55, 0.01 ≦ b ≦ 0.25, 0.10 ≦ c ≦ 0.30, 0.15 ≦ d ≦ 0.35, 0.01 ≦ e ≦ 0.20, a + b + c + d + e = 1 satisfied It is preferable to do.

When the Al content in the firing jig is 0.9 mass% or less in terms of Al ₂ O ₃ , Al hardly diffuses from the firing jig to the dielectric ceramic. For this reason, when the Al content of the dielectric ceramic after firing is 0.007% by mass or less in terms of Al ₂ O ₃ and the concentration of the Al inside the dielectric ceramic is 1, the dielectric ceramic A dielectric ceramic having an Al concentration ratio in the vicinity of the surface of 0.5 to 2 can be manufactured. In particular, even for a dielectric ceramic having a diameter of 25 mm or more and a thickness of 15 mm or more, the Al content of the dielectric ceramic and the concentration ratio of Al can be within the range of the dielectric ceramic of the present invention.

When the Al content in the firing jig exceeds 0.9 mass% in terms of Al ₂ O ₃ , it is difficult to provide a method for manufacturing a dielectric ceramic having a high Qf when the size of the dielectric ceramic is large. .

The amount of Al ₂ O ₃ in the firing jig can be measured by the following method. The firing jig is pulverized in a cemented mortar to obtain an analysis sample. To 0.1 g of this analytical sample, 2 g of boric acid and 3 g of sodium carbonate are added and melted, and dissolved in a hydrochloric acid solution. This solution is subjected to quantitative analysis of Al with an ICP emission spectroscopic analyzer (ICPS-800 manufactured by Shimadzu Corporation). The obtained Al content is converted into the amount of Al ₂ O ₃ .

  Specifically, the dielectric ceramic of the present invention is manufactured as follows, for example. After preparing metal oxides such as carbonates, nitrates, and acetates that produce oxides of Ba, Sr, Mg, W, and Yb, or oxides upon firing, as main raw materials, and weighing these so as to be in the above-mentioned range Then, the preparation water is added, and the mixed raw material is wet mixed and pulverized by a mill using zirconia balls or the like. And after drying a mixture at predetermined | prescribed temperature, this mixture is calcined at 1100-1300 degreeC.

  Formulated water is added to the obtained calcined powder, wet-mixed by a mill using zirconia balls or the like as a mixed raw material, and pulverized to an average particle size of 0.8 to 1.2 μm. Furthermore, a predetermined amount, for example, about 3 to 6% by mass of an organic binder for molding is added to prepare a slurry, and the obtained slurry is spray-dried with a spray dryer to obtain a granulated body. Furthermore, the obtained granulated body is formed into an arbitrary shape by a desired forming means, for example, a die press, a cold isostatic press, an extrusion forming, and the like to obtain a formed body. Thereafter, the binder is removed in an oxidizing atmosphere such as the air, and then held at 1600 to 1700 ° C. for 2 to 10 hours, and then the temperature is decreased from 1200 to 800 ° C. at 5 to 100 ° C./hour to obtain a dielectric. Porcelain is obtained.

The following board | substrate can be used as a jig | tool for baking for mounting a molded object. That is, the first candidate is a high-purity magnesia, which is a substrate made of a sintered body containing not more than 0.9% by mass of Al in terms of Al ₂ O ₃ , and the second candidate is high-purity yttrium oxide. there are a substrate formed of a sintered body containing Al _Al 2 _{O 3} in terms of 0.9% by mass or less.

  The binder removal treatment may be performed in the same process as the firing or in a separate process.

  The dielectric ceramic according to the present invention is a dielectric resonator that is operated by electromagnetic coupling by disposing the above-described dielectric ceramic between a pair of input / output terminals.

  The dielectric ceramic of the present invention is most preferably used particularly as a dielectric ceramic of a dielectric resonator. FIG. 1 shows a schematic diagram of a TE mode type dielectric resonator. The dielectric resonator shown in FIG. 1 is provided with an input terminal 2 and an output terminal 3 on opposite sides of an inner wall of a metal case 1, and a dielectric ceramic made of the above dielectric ceramic composition between the input / output terminals 2 and 3. 4 is arranged. In such a TE mode type dielectric resonator, a microwave is input 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, and a specific wave Resonates at frequency. This signal is electromagnetically coupled to the output terminal 3 and output.

  Although not shown, it is needless to say that the dielectric ceramic of the present invention may be applied to a coaxial resonator using a TEM mode, a strip line resonator, a TM mode dielectric ceramic resonator, and other resonators. . Furthermore, a dielectric resonator can also be configured by providing the input terminal 2 and the output terminal 3 directly on the dielectric ceramic 4.

  The dielectric ceramic 4 is a resonance medium having a predetermined shape made of the dielectric ceramic according to the present invention. The shape of the dielectric ceramic 4 is a rectangular parallelepiped, a cube, a plate, a disk, a cylinder, a polygonal column, and other three-dimensional shapes capable of resonance. If it is. The frequency of the input high frequency signal is about 1 to 500 GHz, and the resonance frequency is preferably about 2 to 80 GHz in practice.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

<Reference Example 1>
Using BaCO ₃ , SrCO ₃ , MgCO ₃ , WO ₃ , Yb ₂ O _3, and MnO ₂ powders with a purity of 99% or more as raw materials, these ratios (a, b, c, d, e) shown in Table 1 are used. (MnO ₂ content converted to the ratio) and pure water was added, and wet mixing and pulverization were performed by a mill using zirconia balls. The average particle size of the pulverized particle size was 0.5 to 1 μm.

  Thereafter, the mixture was dehydrated and dried, and calcined at 1200 to 1300 ° C. for 2 hours. Pure water was put into the obtained calcined product, and wet mixing and pulverization were performed by a mill using zirconia balls. This pulverization was wet pulverization such that the average particle diameter was 0.8 to 1.2 μm.

Thereafter, an organic binder for molding was added, followed by spray drying and granulation with a spray dryer. A plurality of the obtained powders are respectively formed into two types of cylinders of a molded body A having a diameter of 10 mm and a thickness of 5 mm and a molded body B having a diameter of 30 mm and a thickness of 15 mm at a molding pressure of 100 MPa using a powder pressure molding machine. Molded. Furthermore, after these cylinders were held at 1670-1700 ° C. for 2-10 hours, the temperature was lowered from 1200-800 ° C. at 5-100 ° C./hour and fired to obtain dielectric ceramics. As a firing jig, a high purity magnesia substrate made of a sintered body containing Al in an amount of 0.1% by mass in terms of Al ₂ O ₃ was used.

  Both planes of the obtained dielectric porcelain were each polished by 0.3 mm, washed and dried, and sample A (sample prepared using molded body A) and sample B (sample manufactured using molded body B) were obtained. No. shown in Tables 1 and 2. A plurality of each were prepared.

  Thereafter, at 22 ° C., the dielectric constants ε and Q values of the samples A and B were measured by a cylindrical resonator method. The measurement frequencies when εr and Q values were measured were 6 to 9 GHz for sample A and 1 to 3 GHz for sample B. Qf is a value obtained by multiplying the measurement value Q and the measurement frequency f.

The temperature coefficient τf of the resonance frequency of the obtained samples A and B at 25 to 85 ° C. is based on the formula τf = {[(f ₈₅ −f ₂₅ ) / f ₂₅ ] / 60} × 10 ⁶ [ppm / ° C.]. Calculated. Here, f ₈₅ is a resonance frequency at 85 ° C., and f ₂₅ is a resonance frequency at 25 ° C. The results are shown in Tables 1 to 5.

Sample A was pulverized, and the Ba, Sr, Mg, W and Yb contents were measured using ICP emission spectroscopic analysis and converted to the contents of BaO, SrO, MgO, WO ₃ , Yb ₂ O ₃ and MnO ₂ . However, it was the same as the preparation composition as shown in Table 1. Similarly, sample No. When the Ba, Sr, Mg, W and Yb contents of Nos. 23 to 44 were measured, as shown in Table 2, sample No. It was the same as 1-22.

The Al content of the analytical sample obtained by pulverizing Sample A was quantitatively analyzed using an ICP emission spectroscopic analyzer, and converted to the Al ₂ O ₃ content.

The Al content in the sample B was measured by using a ICP emission spectroscopic analyzer, and converted to the Al ₂ O ₃ content by cutting out a portion cut out from a region 2 mm deep from the surface. The Al content on the surface of Sample B was measured in the same manner by cutting out each planar portion (upper and lower) of Sample B. Here, the lower part is a surface on the side where the compact B is placed on a firing jig during firing. The upper part is a surface fired so that the compact B does not come into contact with the solid during firing. When the content of _Al 2 _{O 3} of each internal and 1, the upper portion of the _Al 2 _{O 3} value content divided by _Al 2 _{O 3} content of the internal, the content of _Al 2 _{O 3} top internal Al ₂ The value divided by the O ₃ content was determined. Top of _Al 2 _{O 3} value content divided by _Al 2 _{O 3} content of the internal, the value obtained by dividing the content of _Al 2 _{O 3} top with _Al 2 _{O 3} content in the interior, each of the _Al 2 O Calculated as a ₃ concentration ratio.

The average pore diameter was measured by the following method. Samples A and B obtained by mirror polishing were used as analysis samples. An image obtained by observing the analysis sample with a metal microscope at a magnification of 100 was captured with a CCD camera. The average pore diameter of pores shown in this image was measured by an image analyzer. As the image analysis apparatus, LUZEX SE manufactured by Nireco Corporation was used. The measurement conditions in the case of using the image analysis apparatus were a measurement area of 9 × 10 ⁻² mm ^{2 on} the surface of the analysis sample, a measurement count of 10 times, and a measurement total area of 9 × 10 ⁻¹ mm ² .

The average crystal grain size was measured by the following method. Samples A and B obtained by mirror polishing were used as analysis samples. An image obtained by observing the analysis sample with a metal microscope at a magnification of about 400 times was captured with a CCD camera. The average pore diameter of pores shown in this image was measured by an image analyzer. As the image analysis apparatus, LUZEX SE manufactured by Nireco Corporation was used. The measurement conditions when the image analysis apparatus is used are as follows. That is, the measurement area of the analysis sample surface was 5.6 × 10 ⁻³ mm ² , the number of measurements was 3, and the total measurement area was 1.68 × 10 ⁻² mm ² . Here, the average pore diameter was calculated using a value obtained by converting the pore diameter of each pore into an equivalent circle diameter.

Sample B was analyzed using RINT series X-ray diffraction from Rigaku Corporation. A peak intensity of 2θ = 26 to 27 ° attributed to the (112) plane of BaWO ₄ in X-ray diffraction is applied to the (220) plane of a perovskite crystal containing P1, Ba, Sr, Mg, W and Yb. The peak intensity ratio f = P1 / P2 was determined when the assigned peak intensity at 2θ = 30 to 32 ° was P2. As a result of measurement by X-ray diffraction, the crystal structure of BaWO ₄ was determined as JCPDS-ICDD No. 43-646. The structure of the perovskite crystal containing Ba, Sr, Mg, W, and Yb is the same as that of JCPDS-ICDD. 43-646.

The results are shown in Tables 1 and 2. For sample A, as shown in Table 1, No. Any sample Qf of 1-22 was comparatively high with 101000-240000, and (epsilon) r was 20.4-26.3. Sample B No. 23 to 36 had a relatively high Qf of 119000 to 240000. No. of sample B whose Qf is 12000 to 60000 and whose Al ₂ O ₃ content exceeds 0.007 mass%. Compared with 37-38 and 40-44, Qf of sample A is higher.
<Reference Example 2>
Sample No. of Reference Example 1 was prepared except that the sample was prepared by changing the pulverized particle size and the firing temperature within the range of the average crystal grain size of 3 to 5 μm. Sample B was produced in the same manner as in Example 1. As a result, as shown in Table 3, the average crystal grain size of No. 3 in the range of 3 to 4.5 μm. 45 to 48 had a particularly high Qf of 214,000 to 240000. No. which is a sample whose average crystal grain size is outside the range of 3 to 4.5 μm. 48 and 49 had Qf of 179000 and 184000.
<Reference Example 3>
Sample No. of Reference Example 1 was changed except that the content of MnO ₂ was changed. Sample B was produced in the same manner as in Example 1. As a result, as shown in Table 4, the MnO ₂ content was in the range of 0.01 to 0.2% by mass. 50 and 52 had particularly high Qf of 220,000 and 210000, respectively. When the amount of MnO ₂ is in the range of 0.01 to 0.2% by mass, 51, 53, and 54 had Qf of 150,000 to 1750000.
<Reference Example 4>
No. of Reference Example 1 except that the sample was prepared by changing the amount of Al ₂ O ₃ in the firing jig. Sample B was prepared in the same manner as in Example 1 and evaluated in the same manner as in Reference Example 1. As a result, the Al ₂ O ₃ content of Sample B was as shown in Table 5. No. Al ₂ O ₃ content is in the range of 0.001 to 0.007 mass%. 55 to 58 had a relatively high Qf of 175000 to 220,000.

It is sectional drawing which shows one Embodiment of the dielectric resonator of this invention.

Explanation of symbols

1: Metal case 2: Input terminal 3: Output terminal 4: Dielectric porcelain

Claims (6)

A dielectric ceramic having a perovskite crystal containing Ba, Sr, Mg, W and Yb as a main crystal phase, and containing Al within the dielectric ceramic in an amount of 0.007% by mass or less in terms of Al ₂ O _3. When the mass% of Al in the dielectric ceramic is set to 1, the ratio of the mass% of Al in the vicinity of the surface of the dielectric ceramic is 0.5 to 2 and the average pore diameter is 8 μm or less. A dielectric ceramic. 2. The dielectric ceramic according to claim 1, wherein an average crystal grain size of crystals constituting the dielectric ceramic is 3 to 4.5 μm. The dielectric ceramic according to claim 1, wherein Mn is contained as a metal element in an amount of 0.01 to 0.2% by mass in terms of MnO ₂ . The X-ray diffraction peak intensity attributed to the (112) plane of BaWO ₄ is the X-ray diffraction peak intensity attributed to the (220) plane of the perovskite crystal containing P1, Ba, Sr, Mg, W and Yb. The dielectric ceramic according to any one of claims 1 to 3, wherein P1 / P2 is 0.024 or less. It is a manufacturing method for manufacturing a dielectric ceramic having a main crystal phase of a perovskite crystal containing Ba, Sr, Mg, W and Yb, which is placed on a firing jig and fired. A method for producing a dielectric ceramic, wherein an Al content in the firing jig is 0.9 mass% or less in terms of Al ₂ O ₃ . A dielectric resonator comprising the dielectric ceramic according to any one of claims 1 to 4 arranged between a pair of input / output terminals and operated by electromagnetic field coupling.

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