JP3302550B2 - High frequency low loss dielectric material and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency low-loss dielectric material applied to an oscillator, an antenna, a filter, an electronic circuit board or the like in a high-frequency region such as a microwave and a millimeter wave.

[0002]

2. Description of the Related Art In recent years, the development and spread of mobile communications such as automobile telephones and cordless phones, and simple portable telephone systems (PHS), satellite broadcast receivers and the like, and high-frequency devices and devices such as semiconductor and CVD equipment for liquid crystal production have been developed. Accordingly, high frequency dielectric ceramics have been actively used as electronic components and electronic circuit boards used in a high frequency region.

[0003] These dielectric materials used for high-frequency applications are required to reduce dielectric loss at high frequencies for high performance. However, with the recent generalization of high-frequency technology, special dielectric materials such as high temperature and corrosion are required. It is also considered to be used under the above conditions, and a highly reliable, high-frequency, low-loss dielectric material having high mechanical properties and high chemical stability is desired.

[0004]

As such a low-loss dielectric material, BaO, which has better dielectric characteristics than the prior art, has been used.
-TiO _{2 system, MgO-CaO-TiO 2,} CaO-Z
Various additives have been used to improve the electrical characteristics of dielectric ceramic materials such as rO ₂ . However, in these dielectric materials, the strength of the base material itself is at most about 100 MPa at room temperature,
In addition, the mechanical properties strongly depend on the Young's modulus, interatomic bonding mode and bonding force inherent in the material, so that a significant improvement in strength cannot be expected. Therefore, there has been a problem that electronic components using these materials have a low reliability in use under severe conditions while handling them with care.

[0005]

Means for Solving the Problems The present inventors have studied materials having high mechanical strength and low loss in a high frequency band, and have found that a group 3a element (RE) of the periodic table, silicon (Si) and oxygen A kind of disilicate (RE ₂ Si ₂ O ₇ ) or monosilicate (RE ₂ SiO ₅ ) of Group 3a element of the periodic table obtained by controlling the composition ratio and firing conditions of the ternary system composed of (O) The present inventors have found that a sintered body containing the above has a low loss property and a high mechanical strength in a high frequency range, and has reached the present invention.

That is, the high-frequency low-loss dielectric material of the present invention comprises at least a complex oxide containing Group 3a element (RE) of the periodic table and silicon (Si), and has a main phase of disilicate (RE _2). Si ₂ O ₇ ), monosilicate (RE ₂ S)
iO ₅ ), and the molar ratio of the oxide equivalent of the Group 3a element of the periodic table (RE ₂ O ₃ ) to the silicon equivalent of silicon dioxide (SiO ₂ ) is 0.4. And a dielectric loss at 10 GHz of 5 × 10 ⁻⁴ or less.

Further, as a method for producing such a material according to the present invention, an oxide of a Group 3a element of the periodic table (RE ₂ O ₃ ) and silicon dioxide (SiO ₂ ) are used.
iO ₂ ), an oxide of an element of Group 3a of the periodic table (R
E ₂ O ₃ ) molar ratio (RE ₂ O ₃ / SiO ₂ ) is 0.4
The molded body having a composition of ~ 1.2 is fired at a temperature of 1100 to 1850 ° C in an oxidizing or non-oxidizing atmosphere.

[0008]

According to the high-frequency low-loss dielectric material of the present invention and the method of manufacturing the same, disilicate which is a silicate of a Group 3a element of the periodic table represented by RE ₂ Si ₂ O ₇ and RE ₂ SiO ₅ is used. By containing one or more monosilicates, a high dielectric strength can be achieved while obtaining a low dielectric loss at high frequencies. It is not clear why such a configuration provides a low loss property, but the disilicate or monosilicate has a low symmetry in the crystal structure, and has a monoclinic crystal structure. It is presumed that it is.

As a result, as a low-loss material, an oscillator, an antenna,
When used for filters or electronic circuit boards,
Highly reliable parts can be provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The high-frequency low-loss dielectric material of the present invention is composed of a complex oxide containing at least a Group 3a element (RE) of the periodic table and silicon (Si). Are disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂ ) which are silicates of Group 3a element of the periodic table.
Be those which contain one or more kinds of SiO ₅₎ as a main phase, crystal structure disilicate (RE ₂ Si ₂ O ₇₎ is triclinic, monoclinic, orthorhombic alpha, beta, gamma, [delta] , Y-type, but β, γ, and δ phases, which are high-temperature stable phases, are particularly preferable.

In the dielectric material of the present invention, in addition to the main phase, as a crystal having a different composition, for example, a silicon dioxide (SiO ₂ ) phase or an oxide of a group 3a element of the periodic table (R
E ₂ O ₃ ) phases may also form, but these phases
Since ionic bonding is high when used alone, dielectric loss in a high frequency range increases when these phases are used as the main phase.

Accordingly, the overall composition of the low-loss dielectric material for high frequency waves according to the present invention is as follows.
E ₂ O ₃ ) and the oxide of silicon dioxide (SiO ₂ ), and the molar ratio of RE ₂ O ₃ to SiO ₂ , that is, RE ₂
It is important that the composition ratio expressed as O ₃ / SiO _{2 is} in the range of 0.4 to 1.2, particularly 0.45 to 1.1.

The reason is that if the molar ratio represented by RE ₂ O ₃ / SiO ₂ is smaller than 0.4, a large amount of SiO ₂ phase is formed. Conversely, if the molar ratio is larger than 1.2, RE
_This is because many ₂ O ₃ phases are formed, and in any case, the dielectric loss of the material is increased.

The Group 3a element (RE) of the Periodic Table used in the present invention includes Y, Sc and lanthanoid elements, and in particular, Y, Sc, Dy, Er, Ho, Y
Rare earth elements such as b and Lu are preferable because the ionic radius is small, so that the silicate crystal formed has a high bond strength and therefore has excellent low loss in a high frequency range.

On the other hand, metals of Groups 4a, 5a, and 6a of the periodic table, and oxides, carbides, nitrides, silicides, and silicon carbide (SiC) thereof are dispersed particles or whiskers of the dielectric material of the present invention. Even if a small amount is present in the material, the effect of deteriorating the properties is small, so that it is naturally possible to improve the properties as a composite material by adding an appropriate amount of these based on well-known techniques.

Next, a method for producing the rare earth silicate-based low-loss dielectric material for high frequencies of the present invention will be described. According to the present invention, powders of rare earth element oxides (RE ₂ O ₃ ) and silicon dioxide (SiO ₂ ), which are Group 3a elements of the periodic table, are mainly used as starting materials. The starting material may be mixed with a rare earth element and silicon metal powder and then oxidized in an oxygen atmosphere. The particle diameter of these raw material powders is suitably from 0.3 to 2.0 μm.

Next, an oxide of a Group 3a element of the periodic table (RE ₂ O ₃ ) and silicon oxide (SiO ₂ )
₂ ) and a molar ratio represented by RE ₂ O ₃ / SiO ₂ of 0.
Prepare in the range of 4-1.2.

After mixing the raw material powders prepared so as to have the above proportions, the mixture is formed into an arbitrary shape by a desired molding means, for example, die pressing, casting molding, extrusion molding, injection molding, cold isostatic pressing, tape molding or the like. Mold into

Next, the compact is sintered by a known sintering method, for example, a hot press method, a normal pressure sintering method, a nitrogen gas pressurizing sintering method, and a hot isostatic pressure treatment (HIP) after the sintering.
Or after glass sealing, hot isostatic pressure treatment (HI
P) to obtain a dense sintered body having a theoretical density ratio of 95% or more.

The firing atmosphere may be either an oxidizing or non-oxidizing atmosphere, and the firing temperature is set to 1100 to 1850 in order to obtain a dense sintered body having high mechanical strength.
It is desirable to bake at a temperature of 1300C, especially at a temperature of 1300 to 1750C.

According to the above-described manufacturing method, a homogeneous, fine-grained and dense rare earth silicate-based low-loss dielectric material for high frequency can be obtained, and a dielectric loss (tan) at a high frequency of 10 GHz is obtained.
δ) is as low as 5 × 10 ⁻⁴ or less, and has a high strength of 300 MPa or more at room temperature as compared with a conventionally known dielectric material, as is apparent from the examples described later.

Therefore, the dielectric material of the present invention can be used under severe conditions such as microwaves, millimeter waves, etc.
A dielectric material suitable for an oscillator, an antenna, a filter, an electronic circuit board, or the like applied to a high frequency band of 300 GHz, particularly 1 GHz to 100 GHz. By using such a dielectric material, a highly reliable high frequency electronic component can be obtained. Can be provided.

[0023]

EXAMPLE Powders of Group 3a element oxide (RE ₂ O ₃ ) powder and silicon dioxide (SiO ₂ ) powder were used as raw material powders to obtain the composition ratios shown in Tables 1 and 2. ,
First, a hydrostatic pressure treatment was performed at a pressure of 1 t / cm ² to produce a molded body.

Next, as shown in Tables 1 and 2, when the molded body is fired in the atmosphere at normal pressure, the temperature is maintained at each firing temperature for 5 hours. Firing was performed in an (Ar) atmosphere or a nitrogen (N ₂ ) atmosphere at a pressure of 0.3 t / cm ² at each firing temperature for 1 hour.

The sintered body thus obtained was subjected to JIS-R16
The specimen was polished to a predetermined size according to the standard No. 01 to prepare a bending test piece, and the bending test piece was subjected to a four-point bending test at room temperature. On the other hand, cylindrical grinding was performed to a shape having a diameter of 16 mm and a thickness of 8 mm, and dielectric loss was measured at around 10 GHz by a dielectric cylinder resonator method. In addition, the sintered body RE ₂
As a result of examining the O ₃ / SiO ₂ molar ratio by the ICP method,
It was confirmed that the composition was almost the same as the starting composition. Table 1 shows the crystal phases detected by the X-ray diffraction measurement.
It was shown to. Tables 1 and 2 show the above results.

[0026]

[Table 1]

[0027]

[Table 2]

According to the above results, RE ₂ O ₃ / SiO ₂
Sample No. 1, 8, 15, 22, with a ratio of less than 0.4
29, 36, 43 and the ratio of RE ₂ O ₃ / SiO ₂ is 1.
Samples No. 7, 14, 21, 28, 35, 4 larger than 2
Nos. 2 and 49 have sufficient strength, but the dielectric loss at 10 GHz exceeds 5 × 10 ^-4 , whereas the dielectric material of the present invention has a dielectric loss of 5 × 10 ⁴ when measured at a high frequency of 10 GHz. × 10 ^-4 or less and room temperature strength of 300 MPa or more were achieved.

[0029]

As described above, the high-frequency low-loss dielectric material of the present invention is an excellent low-loss material having a dielectric loss of 5 × 10 ⁻⁴ or less at a measurement frequency of 10 GHz.
Because it has a high intensity of 300MPa or more, it can be used under severe conditions, such as microwaves, millimeter waves, etc.
By applying the present invention to an oscillator, an antenna, a filter, an electronic circuit board or the like applied to a high frequency band of up to 300 GHz, a highly reliable high frequency electronic component can be provided.

Claims (3)

(57) [Claims] 1. An element (RE) belonging to at least Group 3a of the periodic table
And a composite oxide containing silicon (Si), and the main phase is at least one of disilicate (RE ₂ Si ₂ O ₇ ) and monosilicate (RE ₂ SiO ₅ ),
A molar ratio of an oxide equivalent (RE ₂ O ₃ ) of the group 3a element of the periodic table to a silicon dioxide (SiO ₂ ) equivalent of the silicon is 0.4 to 1.2, and a dielectric loss at 10 GHz; Is 5 × 10 ^-4 or less. 2. The group 3a element (RE) of the periodic table,
2. The high-frequency low-loss dielectric material according to claim 1, wherein the material is at least one rare earth element selected from the group consisting of Y, Sc, Dy, Er, Ho, Yb, and Lu. 3. An oxide of an element belonging to Group 3a of the periodic table (RE)
₂ O ₃ ) and silicon dioxide (SiO ₂ ), and the molar ratio (RE ₂ O ₃ / Si) of the oxide of a group 3a element of the periodic table (RE ₂ O ₃ ) to the silicon dioxide (SiO ₂ ).
A molded article having a composition of O ₂ ) of 0.4 to 1.2 is fired in an oxidizing or non-oxidizing atmosphere at a temperature of 1100 to 1850 ° C. Production method.