JP2002193661A - Dielectric ceramic and dielectric resonator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dielectric ceramic in which a high ε r and a high Q value, a temperature coefficient τ f of a resonance frequency is small and fracture toughness is large are obtained in a high frequency region. SOLUTION: The dielectric ceramic comprises an oxide including at least Nd, Al, Ca and Ti as a metal element and contains a crystal where a crystal structure is identified in at least one or more kinds among CaAl2O4, Nd2TiO6, Ca2Al2O6, Nd4Ti9O24 and Ca3Ti8Al12O37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric porcelain and a dielectric resonator having a high relative dielectric constant .epsilon.r and a resonance sharpness Q value in a high frequency region such as a microwave and a millimeter wave. Dielectric materials used in various resonator materials, dielectric substrate materials for MIC (Monolithic IC), dielectric waveguide materials, multilayer ceramic capacitors, etc., and dielectric resonators using the same. .

[0002]

2. Description of the Related Art Dielectric ceramics are widely used in dielectric resonators, MIC dielectric substrates, waveguides, and the like in high-frequency regions such as microwaves and millimeter waves. The required characteristics are: (1) Since the wavelength of an electromagnetic wave propagating in a dielectric is reduced to (1 / εr) ^1/2 , the relative dielectric constant is large for the demand for miniaturization; 2) low dielectric loss in a high frequency region, that is, high Q; (3)
The three main characteristics are that the change of the resonance frequency with respect to the temperature is small, that is, the temperature dependence of the relative permittivity εr is small and stable.

[0003] As such dielectric ceramics, for example, in JP-A _{4-118807 CaO-TiO 2 -Nb 2 O} 5 -M
A dielectric ceramic made of O (M is Zn, Mg, Co, Mn, etc.) is shown. However, in this dielectric porcelain, 1
The Q value when converted to GHz is as low as about 1600 to 25000, and the temperature coefficient τf of the resonance frequency is 215 to 835p
pm / ° C, so that the Q value can be improved and τf
There was a problem of reducing the size.

Accordingly, the applicant of the present invention has proposed an LnAlCaTi-based dielectric porcelain (see Japanese Patent Application Laid-Open No. 6-76633,
Is a rare earth element), LnAlSrCaTi-based dielectric porcelain (see JP-A-11-278927) and LnAlC
aSrBaTi based dielectric porcelain (JP-A-11-1062)
No. 55).

[0005]

Problems to be Solved by the Invention LnAlCaTi-based dielectric porcelain (see JP-A-6-76633, Ln is a rare earth element), LnAlSrCaTi-based dielectric porcelain (see JP-A-11-278927), LnAlCaSrB
In an aTi-based dielectric porcelain (see Japanese Patent Application Laid-Open No. H11-106255), the relative dielectric constant εr is 30 to 48 and the Q value is 2000.
0 to 75000, and these characteristics were not a serious problem in practical use.

However, the dielectric frequency of a dielectric ceramic built in a large-sized dielectric resonator used for transmitting and receiving radio waves in a base station of a cellular phone, for example, changes the resonance frequency of the dielectric resonator when chipping or cracking occurs. As a result, a major problem has occurred such as the inability to transmit and receive radio waves from the base station. For this reason, a dielectric porcelain with high fracture toughness that is less likely to cause chipping or cracking is required.

The present invention has been completed in view of the above circumstances, and has as its object a high relative Q value of 30,000 or more in the range of 30 to 48, and a small change rate of the resonance frequency due to temperature. Temperature coefficient of resonance frequency τ _f
An object of the present invention is to provide a dielectric porcelain having a low fracture toughness and a high fracture toughness, and a dielectric resonator using the same.

[0008]

According to the present invention, there is provided a dielectric porcelain comprising:
It is composed of an oxide containing at least Nd, Al, Ca and Ti as metal elements, and has a crystal structure of CaAl ₂ O ₄ , N
d ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and C
It is characterized by containing at least one or more crystals of a ₃ Ti ₈ Al ₁₂ O ₃₇ .

Further, Mn, W and Ta are used as metal elements.
At least one of MnO ₂ , WO ₃ and T
characterized in that it contains 0.01 to 3 wt% in a ₂ O ₅ basis.

Further, the dielectric ceramic is at least Nd, Al, and containing Ca and Ti, a when a composition formula represented as _{aNd 2 O 3 · bAl 2 O} 3 · cCaO · dTiO 2 as the metal element, b , C, d satisfy that 0.056 ≦ a ≦ 0.214 0.056 ≦ b ≦ 0.214 0.286 ≦ c ≦ 0.500 0.230 <d <0.470 a + b + c + d = 1 Features.

Further, the dielectric resonator according to the present invention has the above-mentioned dielectric porcelain arranged between a pair of input / output terminals to constitute a dielectric resonator operated by electromagnetic field coupling.

[0012]

The dielectric ceramic according to the present invention comprises an oxide containing at least Nd, Al, Ca and Ti as metal elements, and has a crystal structure of CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂
Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇
By containing at least one crystal among them, the fracture toughness can be increased.

Further, Mn, W and Ta are used as metal elements.
At least one of MnO ₂ , WO ₃ and T
With total 0.01 to 3 wt% contained in a ₂ O ₅ in terms, it is possible to further enhance the Q value.

The dielectric porcelain of the present invention is obtained by calcining and synthesizing calcium titanate having a non-stoichiometric composition, and calcining the obtained calcined body A with an oxide of Ca, Ti, Nd, Al or an oxide by firing. After mixing with at least one of the possible compounds, granulation is performed to produce a granulated body B, and neodymium aluminate having a non-stoichiometric composition is calcined and synthesized, and the obtained calcined body C and Ca, Ti, After mixing with at least one of oxides of Nd and Al or compounds that can be converted into oxides by firing, granulation is performed to produce granules D, and the granules B and D are mixed, and then molded. And, by a manufacturing method of firing at 1500 ° C. to 1650 ° C. for 2 hours or more, the crystal structure is CaAl.
₂ O ₄ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti
₈ Al ₁₂ contain a crystal identified by at least one or more of O ₃₇ can be obtained a dielectric ceramic having a large fracture toughness.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below.

The dielectric porcelain in the present invention means a sintered body obtained by molding and firing a green body. In order to increase the Q value, it is made of an oxide containing at least Nd, Al, Ca and Ti as metal elements, and has a crystal structure of CaAl ₂ O ₄ , Nd ₂ TiO ₆ , C
_{a 2 Al 2 O 6, Nd} 4 Ti 9 O 24 and Ca ₃ Ti ₈ Al _{1 2}
It contains at least one crystal of O ₃₇ .
In order to further improve the fracture toughness of the dielectric porcelain of the present invention, the crystal structure should be CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂
Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇
It is desirable to contain at least two or more of these crystals. Particularly preferably, the crystal structure is CaAl ₂ O ₄ , Nd
₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃
By including at least three or more crystals of Ti ₈ Al ₁₂ O _37, the fracture toughness can be most improved.

In the dielectric porcelain of the present invention, the fracture toughness can be increased because the crystal structure is CaAl ₂ O ₄ ,
Liquid phase sintering is promoted by containing at least one crystal of Nd ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ , and the sintering is promoted. It is considered that the fracture toughness is improved by improving the crystal grain boundary strength of the body.

The reason why the fracture toughness is improved when the crystal is contained is considered as follows.

The main crystal phase of the dielectric ceramic according to the present invention is a solid solution of CaTiO ₃ and NdAlO ₃ having a perovskite crystal structure. In order to improve the fracture toughness of the dielectric porcelain of the present invention, a liquid phase that easily forms a solid solution with the crystal particles of the solid solution is generated in the sintering process, and the crystal particles of the solid solution and the liquid phase are strongly bonded. It is necessary to produce a crystal having an effect of causing the crystal to have a function of causing a crystal to be formed. The crystal having the action is contained in the dielectric porcelain of the present invention, and the crystal structure is CaAl ₂ O ₄ , Nd.
₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃
It is a crystal of at least one kind among Ti ₈ Al ₁₂ O ₃₇ . Other crystals such as Nd ₂ Ti ₂ O ₇ , CaAl ₆
O _{13 and the} like hardly form a solid solution with the solid solution crystal, so that the bonding strength with the solid solution crystal is low, and when mechanical stress occurs in the sintered body, cracks are likely to occur in the grain boundaries, resulting in fracture toughness. Becomes smaller.

The conventional dielectric porcelain having a composition similar to that of the dielectric porcelain of the present invention does not contain the crystals, and thus has a low fracture toughness.

Here, C contained in the dielectric porcelain of the present invention
aAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti
The presence of crystals of ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ was analyzed by a selected area electron diffraction image using a transmission electron microscope.
The measurement is performed by a line diffraction method, a minute X-ray diffraction method, or the like. Further, it is desirable that these crystals are contained in an amount of 30% by volume or less.
It is particularly desirable to contain 10 to 10% by volume. When measuring the content (% by volume) of these crystals, measurement is performed by analysis using a selected area electron diffraction image using a transmission electron microscope.

Analysis by a selected area electron diffraction image using a transmission electron microscope reveals that C contained in the dielectric porcelain of the present invention.
aAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti
₉ O _{2 4} and Ca ₃ Ti ₈ Al ₁₂ when performing the identification of crystal O _37, for example a magnification internal crystal dielectric ceramic 2000
An area of about 5 × 10 ^{−3 to} 5 × 10 ⁻² mm ^{2 at} about 8000 times is observed by a photograph and a selected area diffraction image, and an electron diffraction image of each crystal is analyzed to identify a crystal structure. Of the area, CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al
_The content (vol.%) Is defined as the proportion occupied by at least one of ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O _37.
And

As a measuring device, for example, a transmission electron microscope JEM2010F manufactured by JEOL is used.

The crystal structure contained in the dielectric porcelain of the present invention is CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄
The production method for producing at least one crystal of Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ is as follows.

The method of manufacturing the dielectric porcelain of the present invention includes:
A calcined body obtained by calcining and synthesizing calcium titanate having a non-stoichiometric composition in which the ratio of the titanium element to the calcium element is different.
And at least one of oxides of Ca, Ti, Nd, and Al or compounds that can be turned into oxides by firing, and then granulating to produce granulated body B, wherein the ratio of neodymium element to aluminum element is different. Neodymium aluminate having a specific composition is calcined and synthesized, and the calcined body C and Ca, Ti, N
d, mixed with at least one of Al oxides or compounds that can be converted into oxides by firing, and then granulating the granulated product D
Is prepared, and the granules B and D are mixed and then molded.
It is characterized by firing at a temperature of 500 ° C. to 1650 ° C. for 2 hours or more.

By using this manufacturing method, the crystal structure during firing is CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al ₂
A liquid phase composed of at least one crystal of O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ is generated, and as a result, the strength of the crystal grain boundary of the sintered body is improved, so that the sintered body is broken. It is thought that the toughness is improved. The mechanism by which these crystals are formed during firing is considered as follows.

The granules B may contain Ca, T which is not chemically bonded to the non-stoichiometric calcium titanate.
It is made of at least one of oxides of i, Nd, and Al or compounds that can be turned into oxides by firing. The granule D is made of at least one of oxides of Ca, Ti, Nd, and Al which are not chemically bonded to neodymium aluminate having the non-stoichiometric composition or compounds which can be converted into oxides by firing. The Ca, Ti, Nd, not chemically bonded, contained in the granules B and D,
Al oxides or compounds that can be converted into oxides by firing tend to react with each other during the sintering process, and are considered to produce liquid phase components. The Ca, Ti, Nd, A
Compounds that do not contribute to the formation of the liquid phase component among the oxides of l or compounds that can be turned into oxides by firing chemically bind to the calcium titanate and the neodymium aluminate and contribute to the formation of the solid solution. Conceivable.

Further, by controlling the average particle size of the granules A and B to 50 to 100 μm, the liquid phase sintering is promoted in the sintering process in the dielectric porcelain of the present invention, and the crystal structure is improved. CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ ,
Crystals identified by at least two of Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ are generated, which can further improve the fracture toughness.

In order to further improve the fracture toughness of the dielectric porcelain of the present invention, the average particle size of the granules B and D is preferably 50 to 100 μm. Thereby, the crystal grain size of the sintered body can be uniformly controlled, so that the fracture toughness can be further improved.

Further, as a method of manufacturing a dielectric porcelain of the present invention, a calcined body A of calcium titanate having the above-mentioned non-stoichiometric composition and / or a calcined body B of neodymium aluminate having the above-mentioned non-stoichiometric composition are further added with a metal element At least one of Mn, W and Ta is MnO ₂ , WO ₃ and T
By manufacturing a granulated body containing 0.01 to 3 wt% in total in total volume a ₂ O ₅ in terms by the process, it is possible to further obtain a high dielectric ceramic Q value.

The dielectric porcelain according to the present invention is characterized in that at least one of Mn, W and Ta as a metal element is Mn.
The content is preferably 0.01 to 3% by weight in terms of O ₂ , WO ₃ and Ta ₂ O ₅ . The content of at least one of Mn, W and Ta of 0.01 to 3% by weight in terms of MnO ₂ , WO ₃ and Ta ₂ O ₅ is 0.01 to 3% by weight.
This is because when the content is contained, the Q value is remarkably improved. In order to increase the Q value, at least one of Mn, W and Ta is required.
Preferably contains especially from 0.02 to 2 wt% in a total amount in MnO _2, WO ₃ and Ta ₂ O ₅ in terms of species, further M
n is preferably contained in an amount of 0.02 to 0.5% by weight in terms of MnO ₂ .

Furthermore, the dielectric ceramic of the present invention, at least Nd, Al, and containing Ca and Ti, a when a composition formula represented as _{aNd 2 O 3 · bAl 2 O} 3 · cCaO · dTiO 2 as the metal element , B, c, and d satisfy the following condition: 0.056 ≦ a ≦ 0.214 0.056 ≦ b ≦ 0.214 0.286 ≦ c ≦ 0.500 0.230 <d <0.470 a + b + c + d = 1 Is preferred.

The reasons for limiting the molar ratios a, b, c, and d of the respective components to the above ranges in the dielectric ceramic of the present invention are as follows.

That is, when 0.056 ≦ a ≦ 0.214, when 0.056 ≦ a ≦ 0.214, εr is large, Q value is high, and the absolute value of the temperature coefficient τf of the resonance frequency is large. This is because it becomes smaller. In particular, 0.078 ≦ a ≦ 0.1
80 is preferred.

The reason for setting 0.056 ≦ b ≦ 0.214 is that
When 0.056 ≦ b ≦ 0.214, εr is large and Q
This is because the value is high and the absolute value of τf becomes small. In particular, 0.078 ≦ b ≦ 0.180 is preferable.

The reason that 0.286 ≦ c ≦ 0.500 is as follows.
When 0.286 ≦ c ≦ 0.500, εr is large and Q
This is because the value is high and the absolute value of τf becomes small. Particularly, 0.330 ≦ c ≦ 0.470 is preferable.

The reason for 0.230 <d <0.470 is that
When 0.230 <d <0.470, εr is large and Q
This is because the value is high and the absolute value of τf becomes small. Particularly, 0.340 ≦ d ≦ 0.45 is preferable.

In the present invention, in order to increase the Q value, it is preferable that 0.75 ≦ (b + d) / (a + c) ≦ 1.25. To further increase the Q value, 0.85 ≦ (b +
It is particularly preferred that d) / (a + c) ≦ 1.15.

Specifically, the method for manufacturing a dielectric ceramic according to the present invention comprises, for example, the following steps (1a) to (10a).

(1a) Each powder of calcium carbonate (CaCO ₃ ) and titanium oxide (TiO ₂ ) was weighed to a desired ratio as a starting material, and pure water was added.
A slurry is obtained by wet mixing and pulverization by a ball mill using zirconia balls or the like so that the average particle size of the mixed raw material is 2.0 μm or less. In this case, CaCO ₃
And TiO ₂ are weighed so that the molar ratios are different.

(2a) After drying the slurry of (1a),
Calcination is performed at 000 to 1300 ° C. for 1 to 10 hours to obtain a calcined product A.

(3a) Neodymium oxide (N
d_TwoO_Three), Aluminum oxide (Al _TwoO_Three), Carbonated manga
(MnCO_Three), Tungsten oxide (WO_Three), Oxidation
(Ta)_TwoO_Five) And wet milled
Crush.

(4a) After adding a binder to the slurry obtained in (3a), granules are granulated to have an average particle size of 50 to 100 μm by a spray drying method to obtain granules B.

(5a) As starting materials, high-purity neodymium oxide (Nd ₂ O ₃ ) and aluminum oxide (Al
After weighing each powder of ₂ O ₃ ) to a desired ratio, adding pure water and wet-mixing with a ball mill using zirconia balls or the like so that the average particle size of the mixed raw material is 2.0 μm or less. And pulverization to obtain a slurry. In this case, weighing is performed so that the molar ratio between Nd ₂ O ₃ and Al ₂ O ₃ is different.

(6a) After drying the slurry obtained in (5a), it is calcined at 1000 to 1300 ° C. for 1 to 10 hours to obtain a calcined product C.

(7a) Calcium carbonate (CaCO ₃ ), titanium oxide (TiO ₂ ), manganese carbonate (MnCO ₃ ), tungsten oxide (WO ₃ ), and tantalum oxide (Ta ₂ O ₅ ) are added to the calcined product C. And wet grinding with a ball mill.

(8a) After adding a binder to the slurry obtained in (7a), the granules are granulated to have an average particle size of 50 to 100 μm by a spray drying method to obtain granules D.

(9a) The granules B and D are uniformly mixed, and the obtained mixture is molded by a known molding method, for example, a die pressing method, a cold isostatic pressing method, an extrusion molding method and the like. To form an arbitrary shape. (10a) The obtained molded body is kept at 1500 ° C. to 1650 ° C. for 2 hours or more and fired to obtain the dielectric ceramic of the present invention.

Further, the dielectric porcelain of the present invention further comprises Zn
O, NiO, SnO_Two, Co_ThreeO_Four, ZrO_Two, LiC
O_Three, Rb_TwoCO_Three, Sc_TwoO_Three, V_TwoO_Five, CuO, Si
O_Two, BaCO_Three, MgCO_Three, Cr_TwoO_Three, B_TwoO_Three, Ge
O_Two, Sb_TwoO_Five, Nb_TwoO_Five, Ga_TwoO _ThreeMay be added
No. These vary depending on the added components, but εr and resonance frequency.
Optimization of wave number temperature coefficient τf and improvement of mechanical strength
5 weight in total for 100 parts by weight of main component
Parts by weight or less.

The dielectric porcelain of the present invention is most preferably used as a dielectric porcelain of a dielectric resonator. FIG.
FIG. 1 shows a schematic view 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 porcelain 4 made of the above dielectric porcelain is provided between these input / output terminals 2 and 3. Arranged and configured. 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 porcelain 4 by reflection at a boundary between the dielectric porcelain 4 and free space, and specified. Resonance occurs at the frequency of This signal is electromagnetically coupled to the output terminal 3 and output.

Although not shown, the dielectric ceramic of the present invention may be applied to a coaxial resonator, a strip line resonator using a TEM mode, a dielectric ceramic resonator of a TM mode, and other resonators. Of course. Further, a dielectric resonator can be formed by directly providing the input terminal 2 and the output terminal 3 on the dielectric ceramic 4.

The above-mentioned dielectric porcelain 4 is a resonance medium of a predetermined shape made of the dielectric porcelain of the present invention, and its shape is a rectangular parallelepiped, cubic, plate-like, disk, column, polygonal column, etc. What is necessary is just a three-dimensional shape. The frequency of the input high-frequency signal is about 1 to 500 GHz, and the resonance frequency is preferably about 2 GHz to 80 GHz for practical use.

Note that the present invention is not limited to the above-described embodiment, and various changes may be made without departing from the scope of the present invention.

[0054]

EXAMPLES As shown in (1b) to (11b), samples of the dielectric porcelain of the present invention were prepared.

(1b) After weighing each powder of calcium carbonate (CaCO ₃ ) and titanium oxide (TiO ₂ ) as a starting material, pure water was added thereto, and the mixed material had an average particle size of 0.5 to 0.5%.
Wet mixing and pulverization were performed by a ball mill using zirconia balls or the like so as to have a thickness of 1.5 μm.

(2b) After drying the pulverized product of (1a), 12
Calcination was performed at 00 ° C. for 2 hours to obtain a calcined product T.

(3b) Neodymium oxide (N
d_TwoO_Three), Aluminum oxide (Al _TwoO_Three), Carbonated manga
(MnCO_Three), Tungsten oxide (WO_Three), Oxidation
(Ta)_TwoO_Five) And wet milled
Crushed.

(4b) After adding a binder to the slurry obtained in (3b), the granules were granulated to have an average particle size of 50 to 100 μm by a spray drying method to obtain granules U.

(5b) As starting materials, high-purity neodymium oxide (Nd ₂ O ₃ ) and aluminum oxide (Al
After weighing each powder of ₂ O ₃ ), pure water was added, and wet mixing and pulverization were performed by a ball mill using zirconia balls or the like so that the mixed raw material had an average particle size of 0.5 to 1.5 μm.

(6b) After drying the pulverized product of (5b), 12
Calcination is performed at 00 ° C. for 2 hours to obtain a calcined product V.

(7b) Calcium carbonate (CaCO ₃ ), titanium oxide (TiO ₂ ), manganese carbonate (MnCO ₃ ), tungsten oxide (WO ₃ ), and tantalum oxide (Ta ₂ O ₅ ) are added to the obtained calcined product V. And wet-pulverized by a ball mill.

(8b) After the binder was added to the slurry obtained in (7b), the granules were granulated to have an average particle size of 50 to 100 μm by a spray drying method to obtain granules W.

(9b) The granules U and W were uniformly mixed, and the resulting mixture was formed into a disk at a pressure of about 1 ton / cm ² and degreased.

(10b) The obtained molded body is placed in the air for 150 hours.
It was kept at 0 ° C. to 1650 ° C. for 2 hours or more and fired to obtain a sintered body.

(11b) The disk (main surface) of the obtained sintered body is polished flat, and ultrasonically cleaned in acetone,
It dried at 1 degreeC for 1 hour, and obtained the sample of the Example of this invention.

Using the obtained sample, the relative permittivity εr, Q at a measurement frequency of 3.5 to 4.5 GHz was measured by the cylindrical resonator method.
The value and the temperature coefficient τf of the resonance frequency were measured. The Q value was converted to a Q value at 1 GHz from the relationship (Q value) × (measurement frequency f) = (constant) that generally holds in microwave dielectrics. As the temperature coefficient of the resonance frequency, a temperature coefficient τf of 25 to 85 ° C. was calculated based on the resonance frequency at 25 ° C. Further, the fracture toughness K _C was measured by the IF method described in JIS standard R1607.

Further, the sintered body was used as a Technology Li
It processed using the ion thinning apparatus made from nda, and the crystal structure of the crystal in a sintered compact was measured as follows by observation with a transmission electron microscope and analysis by a limited area electron diffraction image.

JEOL's transmission electron microscope JEM20
Using 10F, the area of 1 × 10 ⁻³ mm ² or more of the crystal inside the sintered body was observed by a selected area diffraction image at a magnification of 5,000 times, and the selected area electron diffraction of 5 or more crystals per sample was performed. The images were analyzed and the crystal structure was identified. In Table 2, ○ indicates that the crystal in the sample was identified by the crystal structure with ○.

The results are shown in Tables 1 and 2. As is clear from Tables 1 and 2, Sample N within the scope of the present invention was used.
o. 1 to 27 have relative permittivity εr of 30 to 48 and 1 GHz
Q value when converted to is as high as 30,000 or more, and τ _f is ±
Within 30 (ppm / ° C.), fracture toughness K _C is 2.0-2.
Excellent characteristics as large as 5 MPa · m ^1/2 were obtained.

On the other hand, a sample was prepared as follows as a comparative example.

As starting materials, high-purity calcium carbonate (CaCO ₃ ), titanium oxide (TiO ₂ ), neodymium oxide (Nd ₂ O ₃ ), and aluminum oxide (Al ₂ O ₃ ) powders were weighed, mixed, and pulverized. After calcining at 1200 ° C. for 2 hours, the calcined product was wet-pulverized to an average particle size of 2.0 μm or less to obtain a slurry. 5% by weight of a binder was added to the obtained slurry, and granulated to an average particle size of 30 to 40 μm by a spray drying method. The granulated product was formed into a disc shape at a pressure of about 1 ton / cm ² and then degreased. It was calcined at 1500 to 1600 ° C. for 2 hours. The obtained sample was polished, washed, and dried in the same manner as in the above-described examples, and then similarly, the relative dielectric constant εr, Q value,
The temperature coefficient τ _f of the resonance frequency and the fracture toughness K _c were measured.

As can be seen from Tables 1 and 2, the sample Nos. 28 to 30 have a fracture toughness K _C of 1.7 MPa.
・ It became smaller than m ^1/2 .

[0073]

[Table 1]

[0074]

[Table 2]

[0075]

According to the present invention, an oxide containing at least Nd, Al, Ca and Ti as a metal element has a crystal structure of CaAl ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ A.
By containing a crystal identified by at least one of l ₂ O ₆ , Nd ₄ Ti ₉ O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ , a high relative dielectric constant ε in a high frequency region is obtained.
A dielectric porcelain having r, high Q value, and large fracture toughness can be obtained. As a result, the present invention can be applied to resonator materials, MIC dielectric substrate materials, dielectric waveguides, dielectric antennas, and other various electronic components used in microwave and millimeter wave regions.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a dielectric resonator of the present invention.

[Explanation of symbols]

 1: metal case 2: input terminal 3: output terminal 4: dielectric porcelain

Claims (4)

[Claims] (1) at least Nd, Al, C
a and an oxide containing Ti and having a crystal structure of Ca
Al ₂ O ₄ , Nd ₂ TiO ₆ , Ca ₂ Al ₂ O ₆ , Nd ₄ Ti ₉
A dielectric ceramic comprising at least one crystal of O ₂₄ and Ca ₃ Ti ₈ Al ₁₂ O ₃₇ . 2. A metal element comprising at least one of Mn, W and Ta in total of MnO ₂ , WO ₃ and Ta ₂ O ₅
2. The dielectric porcelain according to claim 1, wherein the content is 0.01 to 3% by weight in total. 3. At least Nd, Al, C as a metal element
containing a and Ti, a when a composition formula represented as _{aNd 2 O 3 · bAl 2 O} 3 · cCaO · dTiO 2, b, c, d is, 0.056 ≦ a ≦ 0.214 0.056 ≦ 3. The dielectric ceramic according to claim 1, wherein b ≦ 0.214 0.286 ≦ c ≦ 0.500 0.230 <d <0.470 a + b + c + d = 1 is satisfied. 4. The dielectric resonator according to claim 1, wherein said dielectric ceramic is arranged between a pair of input / output terminals and is operated by electromagnetic field coupling. .