JP5247294B2 - Ceramic support member and dielectric resonator using the same - Google Patents

Description

  The present invention relates to a dielectric resonator used in a mobile phone base station or the like. In particular, the present invention relates to a ceramic support member that can be used for supporting and fixing a dielectric resonator in a cavity of the dielectric resonator, and can improve the dielectric characteristics as the dielectric resonator, and a dielectric resonator using the ceramic support member.

Dielectric resonators are used as frequency filters for mobile communication base stations. For example, a dielectric resonator made of dielectric ceramics is disposed at the center of a metal case via a cylindrical ceramic support member formed of insulating ceramics. When a specific signal is input to this dielectric resonator, only the resonance frequency of the dielectric resonator is output as an output signal. Therefore, this dielectric resonator has been used as a dielectric filter and mounted on various circuits (for example, Patent Documents 1 to 3).
Japanese Utility Model Publication No. 51-94643 Japanese Utility Model Publication No. 3-92809 JP 2003-273614 A

  As such a ceramic support member, a material having a high total dielectric characteristic (particularly Q value) is desired even when used in combination with a dielectric resonator having good dielectric characteristics and high dielectric characteristics.

  The present invention provides a ceramic support member that has good dielectric characteristics when used alone and that can be used in combination with a dielectric resonator, and that can provide good dielectric characteristics (particularly Q value), and a dielectric resonator using the ceramic support member. The purpose is to provide.

The ceramic support member of the present invention is used to support a dielectric resonator, and at least the support portion of the dielectric resonator contains 99.3% by mass of alumina, contains Si and Sr, and contains alumina crystals. It becomes the particles as a main crystal grains, and the grain boundary to SrAl ₂ Si compound represented by the ₂ O ₈ of alumina crystal grains present crystalline phase, further density 3.83 g / cm ³ or more der Ru alumina It consists of a sintered body.

The dielectric resonator of the present invention is characterized in that the ceramic support member and a dielectric resonator supported by the ceramic support member are provided in a cavity .

Since the ceramic support member of the present invention contains 99.3% by mass or more of alumina, the excellent corrosion resistance, mechanical properties, and electrical properties of alumina can be maintained. In addition, a low-loss crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ is present at the grain boundaries of the alumina crystal particles instead of a glass composed of a conventional grain boundary phase component , and the density is 3.83 g. since consisting / cm ³ or more alumina sintered body, it is possible to lower the dielectric loss tangent (tan [delta) than conventional. Thereby, the quality factor Q value represented by the reciprocal of the dielectric loss tangent can be increased.

The dielectric resonator of the present invention, by Rukoto features a ceramic support member of the present invention and the ceramic support dielectric resonator which is supported member in the cavity, reducing the dielectric loss tangent than conventional Therefore, it is possible to obtain a higher quality factor Q value.

The dielectric resonator of the present invention includes the ceramic support member of the present invention and a dielectric resonator supported by the ceramic support member in the cavity, so that the dielectric loss tangent (tan δ) of the dielectric resonator is provided. Therefore, when the dielectric resonator is used for a mobile phone base station or the like, radio waves can be transmitted and received without attenuation.

The best embodiment of the present invention (hereinafter referred to as the present embodiment) will be described in detail with reference to the drawings. As shown in FIG. 1 as an example, a dielectric resonator 1 according to this embodiment includes a dielectric resonator 4 made of dielectric ceramics, and a cylinder made of an alumina sintered body that supports the dielectric resonator 4. And a ceramic support member 3. Thus, the ceramic support member 3 is used to support the dielectric resonator 4, and at least the support portion of the dielectric resonator 4 contains 99.3% by mass or more of alumina, and contains Si and Sr. The crystal phase of the compound represented by SrAl ₂ Si ₂ O ₈ is present at the grain boundary of the alumina crystal particles , and the density is 3.83 g / cm ³ or more. characterized by comprising the alumina sintered body that.

  In addition, in the cavity of the metal case 2, the dielectric resonator 4 is disposed via the ceramic support member 3. When a specific signal is input to the thus configured dielectric resonator 1, only the resonance frequency of the dielectric resonator 4 is output as an output signal. Therefore, the dielectric resonator 1 can be mounted on a dielectric filter or various circuits. Is possible.

Ceramic support member 3 and the dielectric resonator 4 in this embodiment, a method of fitting the ends of the ceramic support member 3 in the recess (not shown) formed in advance by counterbored processed derivative collector resonator 4, etc. It is fixed by.

The ceramic support member 3 is used, for example, to support and fix the dielectric resonator 4 in the cavity of the dielectric resonator 1 , and at least the support portion contains 99.3% by mass or more of alumina, with containing Si and Sr, the alumina crystal grain becomes a main crystal grains, made of alumina sintered body crystal phase of grain boundary SrAl ₂ Si ₂ O compound is Ru represented by _eight of the alumina crystal particles are present .

As shown in FIG. 2, the alumina sintered body of the present embodiment, deposition between alumina crystal particles 10 in (grain boundary 11), a crystalline phase of the low-loss consisting of the compounds express by SrAl ₂ Si ₂ O ₈ Then, since the dielectric loss tangent of the crystal phase itself is low, the dielectric loss tangent of the entire alumina sintered body can be lowered. In a general alumina sintered body, the auxiliary component added as a sintering aid exists between the alumina crystal particles as a glass or a crystal having a high dielectric loss tangent, and the dielectric tangent of the entire alumina sintered body is reduced. There was a tendency to increase.

  Further, in the ceramic support member 3 of the present embodiment, by containing 99.3% by mass or more of alumina, the sinterability becomes perfect and the excellent mechanical and electrical properties of alumina are maintained. Is possible.

In the ceramic support member 3 of the present embodiment, the alumina sintered body includes 0.02 to 0.2% by mass of Si in terms of SiO ₂ and 0.01 to 0.1% by mass of Sr in terms of SrO. It is characterized by that. If the Si and Sr are respectively converted to SiO ₂ and Sr is set to the above range in terms of SrO , the crystal phase of the compound represented by SrAl ₂ Si ₂ O ₈ with these elements and low loss is converted into particles of the alumina sintered body. This is because it precipitates in the boundary. In particular, it is desirable from the viewpoint of dielectric loss tangent and sinterability Si is 0.05 to 0.15 wt% in terms of SiO _2.

  In the ceramic support member 3 of the present embodiment, the alumina sintered body further contains 0.01 to 0.3% by mass of Mg in terms of MgO and 0.01 to 0.2% by mass of Ca in terms of CaO. It is characterized by doing. As a result, the sinterability of the alumina sintered body can be improved, and the sintered body can be further densified, thereby reducing voids and defects that lower the dielectric properties (improve the Q value). And a low-loss alumina sintered body can be obtained.

Moreover, the ceramic support member 3 of the present embodiment is characterized in that the average particle diameter D ₅₀ of the alumina crystal particles is 10μm or more. Thereby, the dielectric loss tangent can be stably reduced, and the Q value can be improved. From the viewpoint of further stabilizing the low dielectric loss tangent, the average particle diameter D ₅₀ of the alumina crystal particles is preferably 15 μm or more. The average particle diameter D ₅₀ of the alumina crystal particles is preferably 70μm or less from the viewpoint of mechanical properties. Incidentally, the average particle diameter D _50, refers to the particle size of cumulative 50% fine particle side of the cumulative particle size distribution.

Moreover, the ceramic support member 3 of the present embodiment is characterized in that crystalline phases present in the grain boundary of the alumina sintered body is a compound represented by Sr Al ₂ Si ₂ O _8. The generation of the crystal phase can be reduced dielectric loss tangent, Ru can be further improved Q value.

In this embodiment, the compound represented by Sr Al ₂ Si ₂ O _8, a concept including those of the constituent elements of Sr is substituted with another element.

Next, the manufacturing method of the ceramic support member 3 of this embodiment is demonstrated. For example, an aluminum oxide powder is mixed with a raw material powder obtained by mixing and heat-treating a Si source and an Sr source, and the mixed powder is molded and then fired at 1500 to 1800 ° C.

The raw material powder obtained by mixing and baking the Sr source and the Si source is a powder obtained by mixing the Si source and the Sr source at a predetermined ratio and baking at 500 ° C. to 1400 ° C. The Si source and Sr source here may be any of metals, oxides, hydroxides, carbonates and nitrates. By using the raw material powder of Si and Sr, the distribution of Si and Sr in alumina sintered body in and made uniform, it is possible to eliminate the uneven sintering tissue.

Further, cause a reaction of Si and Sr preferentially, it is possible to generate Si and Sr, Al, a low crystalline dielectric loss tangent consisting of O element among alumina crystal grains.

In some cases, the raw material powder obtained by mixing and baking the Sr source and the Si source with the aluminum oxide powder and the raw material powder containing the Mg source and the Ca source are mixed and fired. As the Mg source or Ca source , it is possible to use metals, metal oxides, metal hydroxides, metal carbonates, and other salts as powders or aqueous solutions.

For molding, a molding method such as press molding, casting, cold isostatic pressing, or cold isostatic pressing can be used. Next, the obtained molded body is fired in a temperature range of 1500 to 1800 ° C. Thus a high density, it is possible to form a ceramic support member 3 crystal phase consisting of compounds between the alumina grain you express by SrAl ₂ Si ₂ O ₈ is made from the resulting alumina sintered body.

  Next, the dielectric characteristics of the ceramic support member 3 are measured. Dielectric characteristics are measured by a cylindrical resonator method at a measurement frequency of 800 MHz, a relative dielectric constant εr, a Q value, and a temperature coefficient τf of the resonance frequency. After the measurement, the Q value is converted into a Q value at 1 GHz from a certain relationship (Q value) × (measurement frequency f) = which is generally established in a microwave dielectric. As the temperature coefficient of the resonance frequency, a temperature coefficient τf of 25 to 60 ° C. is calculated based on the resonance frequency at 25 ° C.

It is also possible to measure the dielectric loss tangent of the alumina sintered body at the measurement frequencies of 1 MHz and 8.5 GHz. 5 × ^{10 -4} or less at 1 MHz, by using a ceramic support member 3 as good what you 5 × ^{10 -4} or less at 8.5 GHz, the dielectric loss tangent in the frequency region between the measurement frequency 1MHz~8.5GHz Can be expected to be 5 × 10 ⁻⁴ or less.

  With this manufacturing method, it is possible to use a high-precision capacitance meter (Hewlett Packard: HP-4278A) and network analyzer (Agilent Technology: 8722ES) with respect to dielectric loss tangent. This makes it possible to design a low dielectric loss tangent material in the 1 MHz to 8.5 GHz band that cannot be guaranteed by a conventional impedance analyzer. The frequency measured by the network analyzer may deviate somewhat from 8.5 GHz.

Conventionally, dielectric loss tangent at a measuring frequency 1MHz, the capacitor down smelling chromatography data: Measurements (Hewlett Packard HP-4278A), dielectric loss tangent at a measuring frequency 8.5GHz, using a cavity resonator method (a network analyzer 8722ES) It is known that accurate dielectric loss tangents with measurement errors of ± 2 × 10 ⁻⁴ or less and ± 0.1 × 10 ⁻⁴ or less can be obtained. However, in the frequency range of 1 MHz to 8.5 GHz, particularly 10 MHz to 1 GHz, required for semiconductor and liquid crystal panel manufacturing equipment members, there is only measurement by an impedance analyzer (HP-4291A manufactured by Hewlett-Packard Company), and the measurement error is Even if it is small, it is about ± 30 × 10 ⁻⁴ , and the measurement accuracy is very low for a dielectric loss tangent of 5 × 10 ⁻⁴ or less.

Therefore, in this embodiment, the dielectric loss tangent at the measurement frequencies of 1 MHz and 8.5 GHz is indirectly measured without directly measuring the dielectric loss in the frequency region at 1 MHz to 8.5 GHz with an impedance analyzer with low measurement accuracy. When the dielectric loss tangent at the measurement frequency of 1 MHz and 8.5 GHz is in the range of 5 × 10 ⁻⁴ or less, the dielectric loss tangent is 5 × even in the frequency range between the measurement frequency of 1 MHz to 8.5 GHz, particularly 10 to 100 MHz. It can be estimated to be 10 ⁻⁴ or less, and the dielectric loss tangent at the measurement frequency of 1 MHz to 8.5 GHz can be estimated easily and accurately.

Next, the ceramic support member 3, in combination with a dielectric resonator 4 formed of separately manufacturing the dielectric ceramics, and dielectric resonator ceramic body 5. Here, the dielectric ceramics used as derivative collector resonator 4, it is possible to use any one of general any material system if those employed. In this case, according to the use frequency band of the dielectric resonator 1 derivative collector resonator ceramic body 5 is used, the material system of the dielectric ceramics used in the dielectric resonator 4 is selected. The ceramic support member 3 can be changed to various shapes in accordance with this, and since the dielectric loss tangent of the ceramic support member 3 can be made lower than before, a high quality factor Q value can be obtained when combined with the dielectric resonator 4. The ceramic body 5 for a dielectric resonator can be provided.

Next, the derivative collector resonator ceramic body 5, by supporting and fixing the metal cavity 2 as shown in FIG. 1, it is possible to a dielectric resonator 1 of the present embodiment. The dielectric resonator 1 can be mainly used for a filter for a base station of a mobile phone, and has an excellent dielectric characteristic (Q value), so that the number of processing lines per base station is increased as compared with the prior art. It is possible. In addition, it is possible to install a mobile phone base station with higher performance than before even with a small number of installations and an installation area, and it is possible to realize a drastic reduction in the installation cost of the base station.

  Furthermore, if the dielectric resonator 1 provided with the ceramic body 5 for dielectric resonators is installed in an airplane in order to realize use in an airplane where the use of a conventional mobile phone is impossible, the conventional dielectric can be obtained. Compared with a body resonator, the number of processing lines can be increased. For this reason, it is possible to process more lines in a small installation space, and it is possible to use communication-related equipment such as a mobile phone and a personal computer in the airplane without affecting the airplane instrument.

  Moreover, the frequency of the high frequency signal in which the dielectric resonator 1 using the ceramic support member 3 of the present embodiment is used is about 500 MHz to 500 GHz, and the resonance frequency is preferably about 2 GHz to 80 GHz.

  Examples of the present invention will be described below.

<Example 1>
A sample of an alumina sintered body constituting the ceramic support member 3 was manufactured, and its dielectric property (Q value) was evaluated.

First, powders of SiO ₂ and SrCO ₃ were weighed and mixed so as to have compositions shown in Table 1 in terms of SiO ₂ and SrO, respectively, to obtain a mixed powder. This powder was heat-treated at 1000 ° C. to 1300 ° C. and pulverized in an alumina ball mill for 48 to 72 hours to produce a raw material powder.

Next, a sintering aid composed of the Si source , Sr source powder, and a predetermined amount of Mg (OH) ₂ powder is added to 99.95% by mass of Al ₂ O ₃ powder. A predetermined amount of water was further added to the mixture and mixed for 48 hours in an alumina ball mill to form a slurry. The slurry was added to the slurry, dried, granulated, and this mixed powder was press-molded at a pressure of 1 t / cm ² to produce a plurality of samples having a diameter of 16.5 mm and a thickness of 10 mm. Thereafter, subjected to calcination in air at at 1,650 to 1,750 ° C., to obtain a plurality of ceramic support member made of alumina sintered body.

  Next, Q values were measured as dielectric characteristics of these samples and are shown in Table 1. As for the dielectric characteristics, the Q value was measured at a measurement frequency of 800 MHz by a cylindrical resonator method. The measured Q value is converted into a Q value at 1 GHz from a certain relationship (Q value) × (measurement frequency f) = constant relationship generally established in a microwave dielectric, and shows a value of 80000 or more. Was good.

Moreover, the analysis of the crystal phase in each sintered body is performed by energy dispersive X-ray spectroscopy (EDS) and limited-field electron diffraction using a transmission electron microscope (TEM), and Si, Al, Sr, Table 1 shows the presence or absence of SrAl ₂ Si ₂ O _8, which is a low-loss crystal phase composed of a compound containing O element. In FIG. 6 shows an electron diffraction photograph.

As shown in Table 1, Sample No. which is outside the scope of the present invention. Since 1 and 2 do not contain a Sr component, a crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ is not generated at the grain boundary of the alumina crystal particles, and the Q value is as low as less than 80000. The value is shown.

In addition, sample No. which is outside the scope of the present invention. No. 3, the purity of alumina is as low as less than 99.3% by mass, and a crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ is formed at the grain boundary of alumina crystal particles, but other auxiliary agents The Q value was as low as less than 80000 due to the influence of the components.

Compared to this, sample No. within the scope of the present invention. As for Nos. 4 to 7, the alumina purity is 99.3% by mass or more, a crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ is formed at the grain boundary of the alumina crystal particles, and the Q value is 80000. The result showed the value of the above favorable range.

<Example 2>
The alumina sintered body constituting the ceramic support of the present invention was subjected to a test for confirming the dielectric properties (Q value) by increasing or decreasing the amount of SiO ₂ and SrO added with a constant alumina purity.

Tests were conducted in the same manner as in Example 1 for the sample manufacturing method and dielectric property evaluation method. First, a mixed powder was prepared so as to obtain the blending amounts shown in Table 2 for each sample at the stage of producing a mixed powder of SiO ₂ and SrCO ₃ . About the process after that, the sample was produced through the process similar to Example 1. FIG.

For the evaluation of the sample, the Q value was determined by the cylindrical resonator method. And using the crystalline phase by a transmission electron microscope (TEM), to confirm the presence or absence of crystal phase comprising a compound represented by SrAl ₂ Si ₂ O _8.

  About Q value, what showed the value of 130,000 or more was evaluated as a favorable thing.

  Each sample contains a compound containing Mg and Ca elements in addition to Si and Sr elements, and a compound containing elements such as Na, K, Ti, Fe, Ni, Zn and Ga as inevitable impurities within the range of alumina purity. doing.

  The test results are shown in Table 2.

As shown in Table 2, sample no. For No. 8, since the addition amount of SiO ₂ was small and sintering was difficult, the density was slightly lowered, and the Q value was also relatively low. Sample No. As for No. 13, on the contrary, the amount of SiO ₂ added is too large and a crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ can be present at the grain boundary of alumina crystal particles, but more than that Since many glass phases containing Si element with large dielectric loss existed, the Q value was relatively low.

Sample No. No. 14 has a relatively low Q value because the amount of SrO added is too small, and a crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ cannot be sufficiently present at the grain boundaries of alumina crystal particles. It was. Sample No. For No. 19, the amount of SrO added is large, and excess SrO is present at the grain boundaries of the alumina crystal particles, so that the sinterability is relatively poor and tends to be slightly densified. The value was relatively low.

Compared to these samples, sample No. Samples 9 to 12 and 15 to 18 were sufficiently densified, and a crystal phase composed of a compound represented by SrAl ₂ Si ₂ O ₈ could be present at the grain boundaries of the alumina crystal particles. A Q value was obtained.

<Example 3>
Next, a test was conducted to confirm the influence on the dielectric characteristics by increasing or decreasing the addition amount of MgO and CaO while keeping SiO ₂ and SrO constant.

In the test, in the same manner as in Example 2, first, a mixed powder of SiO ₂ and SrCO ₃ is produced at the stage of producing a mixed powder of Table 2 for each sample. About the subsequent process, the sample was produced through the process similar to Example 1. FIG.

For the evaluation of the sample, the Q value was measured by the cylindrical resonator method, and the transmission electron microscope (TEM)
By using the crystal phase, the presence or absence of a crystal phase composed of a compound containing Si, Al, Sr, and O elements was confirmed, consisting of a compound represented by SrAl ₂ Si ₂ O ₈ .

  Each sample contains a compound containing elements such as Na, K, Ti, Fe, Ni, Zn, and Ga as inevitable impurities in the range of 0.001 to 0.05 mass%.

  The test results are shown in Table 3.

  As shown in Table 3, Sample No. Regarding No. 20, since the amount of MgO acting as a sintering aid was too small, the sinterability was relatively poor and the density was slightly lowered. As a result, sample Nos. Having the same alumina purity were obtained. Q value is lower than 21. Sample No. For sample No. 25, the amount of MgO added is large, and excess MgO is present at the grain boundaries of the alumina crystal particles. It is thought that Q value became low compared with 24.

  Sample No. For sample No. 26, since the amount of CaO acting as a sintering aid was too small, the sinterability was relatively poor and the density was slightly lowered. Q value is lower than 27. Sample No. Regarding No. 31, since the amount of CaO added is large and excess CaO is present at the grain boundaries of the alumina crystal particles, Sample No. 31 having the same alumina purity is used. It is thought that Q value became low compared with 24.

Compared to these samples, sample no. For 21～24,27～30,32～34, fully densified, because that could be present grain boundaries SrAl ₂ Si ₂ represented by O ₈ is made of a compound crystalline phase of the alumina crystal grain, high Q value could be obtained.

<Example 4>
Sample No. 1 showing high performance in Example 1 was used. A ceramic resonator 5 for a dielectric resonator is formed by combining a ceramic support body 3 of 23 and a dielectric resonator 4 made of a general dielectric material having a dielectric constant of 33 to 37, and a cylindrical resonator similar to that of the first embodiment. The Q value, which is a dielectric property, was measured by the method.

  As a result, the Q value could be improved by about 10% as compared with a ceramic support member made of a conventional alumina sintered body.

Next, when the ceramic body 5 for dielectric resonator is installed in a metal cavity and used in a base station of a mobile phone, it can be used without any problems and has higher performance than before, so one dielectric resonance. The number of lines that can be processed by the device 1 can be increased, and the capacity of the base station can be improved by 10% or more.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically illustrating an embodiment of the present invention, and is a schematic cross-sectional view of a dielectric resonator including a ceramic support member. It is a figure explaining one embodiment of the present invention typically, and is an organization expansion sectional view of the alumina sintered compact which constitutes a ceramic support member. 3 is an electron diffraction photograph of an alumina sintered body constituting the ceramic support member according to the present invention.

Explanation of symbols

1: dielectric resonator 2: Case 3: ceramic support member 4: dielectric resonator 5: dielectric resonator ceramic body 10: alumina crystal grains 11: grain boundary

Claims (5)

Used for supporting the dielectric resonator, at least the support portion of the dielectric resonator contains 99.3% by mass or more of alumina, contains Si and Sr, and becomes alumina crystal particles as main crystal particles, and wherein the grain boundary to SrAl ₂ Si compound represented by the ₂ O ₈ of alumina crystal grains present crystalline phase ceramic support member further density of from 3.83 g / cm ³ or more der Ru alumina sintered body . 2. The alumina-based sintered body contains 0.05 to 0.2% by mass of Si in terms of SiO ₂ and 0.01 to 0.1% by mass of Sr in terms of SrO, respectively. The ceramic support member described in 1.   The alumina-based sintered body further contains 0.01 to 0.3% by mass of Mg in terms of MgO and 0.01 to 0.2% by mass of Ca in terms of CaO, respectively. Or the ceramic support member of 2.   The ceramic support member according to any one of claims 1 to 3, wherein an average particle diameter of the alumina crystal particles is 10 µm or more.   A dielectric resonator comprising the ceramic support member according to claim 1 and a dielectric resonator supported by the ceramic support member in a cavity.