JP2000335965A - Microwave dielectric porcelain composition and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a microwave dielectric porcelain composition having a higher quality factor while maintaining a high dielectric constant and a low temperature coefficient in a microwave region. SOLUTION: Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄
(R is any one of La, Pr, Nd, Sm, and Gd
X) in the tungsten bronze-type solid solution represented by (x), by setting the value of x to 0.5 ≦ x ≦ 0.7, the quality factor is significantly improved while maintaining a high dielectric constant and a low temperature coefficient. It is possible to provide a microwave dielectric porcelain composition which can be used. Also, the solid solution is x = 2 /
The composition of No. 3 can provide a microwave dielectric ceramic composition having a higher quality factor. Further, by combining this solid solution with TiO ₂ , the firing temperature can be lowered to about 1350 ° C., and a microwave dielectric ceramic composition having a temperature coefficient of 0 can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microwave dielectric porcelain composition, and more particularly to a microwave dielectric porcelain composition most suitable for a dielectric resonator, a dielectric substrate, a dielectric antenna and the like.

[0002]

_2. Description of the Related Art Conventionally, BaO-TiO.sub.2, Mg-CaO-Ti have been used as microwave dielectric ceramic compositions of this kind.
O ₂ system and BaO—R ₂ O ₃ —TiO ₂ (R: rare earth element) system are known, and these microwave dielectric porcelain compositions are used for mobile communication and satellite communication typified by mobile phones. It is a core material responsible for transmitting and receiving signals.When used as a dielectric resonator, it has a high quality factor in the high frequency range.
A high dielectric constant and a low temperature coefficient are required.

[0003]

However, the diversification of equipment used in recent years has led to higher operating frequencies, and dielectric properties in the microwave region have been required.

[0004] First, it is required to have a characteristic that easily resonates due to a weak electromagnetic wave, that is, a high Q value (reciprocal of dielectric loss). In addition, in order to use a dielectric resonator as a filter or to allow a communication device to be used for a long time in mobile communication, a particularly low loss, that is, a high quality factor Q · f value is required. In addition, a high dielectric constant ε _r is necessary for miniaturization of the resonator, and further, it is preferable that a dielectric resonator has its characteristic change due to a change in ambient temperature, that is, a temperature change of the resonance frequency. Therefore, a low temperature coefficient τ _f is desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a microwave dielectric porcelain composition having a higher quality factor while maintaining a high dielectric constant and a low temperature coefficient in a microwave region. For the purpose of providing.

[0006]

In order to achieve the above object, the present invention according to claim 1 is _{directed to} Ba _6-3x R _{8 + 2x} T
i ₁₈ O ₅₄ (R = La, Pr, Nd, Sm, Eu, G
d) is a microwave dielectric ceramic composition having a composition in which the value of x satisfies 0.5 ≦ x ≦ 0.7 in the tungsten bronze-type solid solution represented by (d).

Further, according to a second aspect of the present invention, there is provided the microwave dielectric porcelain composition according to the first aspect, wherein x =
The feature is that it is 2/3.

[0008] In the invention according to claim 1 and claim 2 constructed as described _{above, Ba 6- 3x R 8 + 2x} Ti
₁₈ O ₅₄ (R = La, Pr, Nd, Sm, Eu, Gd
Of the tungsten bronze type solid solution represented by the formula (1), it has been found that the distribution of large cations (Ba and R ³⁺ ) in the crystal structure has a great influence on the microwave dielectric properties. Was.

This crystal structure has two different sizes.
Coordination polyhedron, equivalent to perovskite A site
Distorted square A1 seat and perovskite block
There is a pentagonal A2 seat that can be created between the chiefs. Also the basics
In the periodic unit cell, 10 A1 seats and 4 A2 seats
Since it exists, its basic structural formula is [(R, Ba, V)
₁₀]_A1[(Ba, V)₄]_A2Ti₁₈O₅₄And table
I can do it. Here, V represents an empty seat.

In terms of the structural formula for each composition (the value of x), the structural formula for the end component x = 0 is [R ₈ Ba ₂ ] _A1
[Ba ₄ ] _A2 Ti ₁₈ O ₅₄ is represented. At this time,
Both ions R and Ba are mixed in the A1 seat.

Also, a structural formula in the range of 0 ≦ x ≦ 2/3
Is [R_{8 + 2x}Ba_2-3xV_x] _A1[Ba₄]
_A2Ti₁₈O₅₄It is expressed as In this range, 3
Ba²⁺→ 2R³⁺+ V_A1A1 according to the substitution formula
Ba in the seat is replaced with R and V.

Then, all the Ba in the A1 seat are replaced with R.
The composition is x = ２. That is, the structure of x = 2/3
The formula is [R_{9 + 1/3}V_2/3]_A1[Ba₄]_A2
Ti ₁₈O₅₄It is expressed as At this time, A1 seat and A2 seat
R and Ba live separately.

Further, when 2/3 ≦ x ≦ 1, the structural formula is [R _{9 + ／ + 2 (x− ／)} V
_{2 / 3-2 (x-2 / 3)} ] _A1 [Ba
_{4-3 (x-2 / 3)} V3 _{( x-2 / 3)} ] _A2 Ti
Represented as ₁₈ O ₅₄ . In this range, A2 seat B
a is replaced with R, and the R generated by this replacement occupies the A1 seat, and the A2 seat becomes vacant.

The quality coefficient shows the best value when the value of x is 2/3, that is, when R separates from the A1 seat and Ba separates from the A2 seat.

A region where the value of x is less than 2/3, ie, A
The quality factor becomes worse as Ba enters one seat. On the other hand, if the value of x is larger than 2/3, the A2 seat becomes vacant, and the quality factor becomes worse. Further, when the number of vacant seats in the A2 seat increases, the crystal structure itself loses stability, and reaches a solid solution limit near x = 0.7.

On the other hand, it is shown that the internal strain of the crystal determined by the half-width of X-rays measured by powder X-ray diffraction is x = ／, which is the smallest. It was shown to grow.

That is, x = ２ is a singular point, and in this composition, the crystal structure has little distortion and the internal stress is small due to the existence of R in the A1 seat and Ba in the A2 seat. , The quality factor of the microwave dielectric porcelain composition having a composition in and around this case is greatly improved.

According to a third aspect of the present invention, there is provided the microwave dielectric porcelain composition according to the first or second _aspect , wherein the Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄ solid solution and TiO ₂ are _mixed . It is characterized by being a complex.

Further, according to a fourth aspect of the present invention, there is provided the microwave dielectric porcelain composition according to the third aspect, wherein
The feature is that 1.2 ≦ y ≦ 1.8.

[0020] In the invention according to claims 3 and 4 constructed as described _{above, Ba 6- 3x R 8 + 2x} Ti
_By forming a composite of ₁₈ O ₅₄ solid solution and TiO ₂ , the temperature coefficient can be made close to 0, and
It is possible to improve the quality factor and the dielectric constant.

In the method for producing a microwave dielectric porcelain composition according to claim 5, Ba _6-3x R _{8 + 2x} Ti ₁₈ O is obtained by mixing and calcining the required powdery raw materials.
₅₄ (0.5 ≦ x ≦ 0.9) is characterized in that a solid solution is formed, TiO ₂ is added to the solid solution, and firing is performed.

According to the method of manufacturing a microwave dielectric porcelain composition according to the fifth aspect, first, Ba _6-3x R _{8 + 2x} Ti is obtained by mixing and calcining required powdery raw materials.
₁₈ O ₅₄ (0.5 ≦ x ≦ 0.7) solid solution,
By adding TiO ₂ to this and firing it, Ba is obtained.
_{6-3x R 8 + 2x Ti 18 O} 54 Ba by a two-phase coexisting state of a solid solution and _{TiO 2} 6-3x R
_{Although the} sintering temperature in the case of the _{8 + 2xTi 18} O ₅₄ solid solution single phase was 1450 ° C. or higher, it is possible to perform firing at a lower temperature of about 1350 ° C. than before. Further, the temperature coefficient can be adjusted by the addition amount of TiO ₂ , and the quality coefficient can be improved.

When the phase equilibrium is reached by elongating the firing time, Ba _{6-3 x} R _{8 + 2x} Ti
Ba ₂ Ti ₉ O ₂₀ which is a stable phase appears as a third phase in addition to the coexistence region of the ₁₈ O ₅₄ solid solution phase and the TiO ₂ phase, and the TiO ₂ phase decreases to affect the temperature coefficient. By maintaining the phase of TiO ₂ by adjusting the temperature and the like, it is possible to more reliably adjust the microwave dielectric properties such as the temperature coefficient.

[0024]

According to the first aspect of the present invention, it is possible to provide a microwave dielectric porcelain composition capable of greatly improving the quality factor because the distortion of the crystal structure is small.

According to the second aspect of the present invention, the separation of R and Ba stabilizes the crystal structure, reduces distortion of the crystal structure, and further improves the quality factor. A composition can be provided.

According to the third and fourth aspects of the present invention, the quality coefficient and the dielectric constant are improved as compared with the conventional microwave dielectric porcelain composition.
Alternatively, it is possible to provide a microwave dielectric porcelain composition capable of approaching zero.

Further, according to the invention according to claim 5, B
than in the case of _{a 6-3x R 8 + 2x Ti 18} O 5 4 solid solution single phase, it becomes possible to firing at a low temperature, it is possible to improve the microwave dielectric properties.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> Ba_6-3xSm
_{8 + 2x}Ti₁₈O₅₄BaCO to create₃,
Sm ₂O₃, TiO₂The powder sample of the composition (x
) And obtain it at 24:00 with a ball mill.
2 hours at 1000 ° C after wet mixing and grinding in ethanol
Kayaki was performed. After calcination, re-crushed in an alumina mortar,
Add PVA as a binder and mix evenly.
And granulated through a sieve (300 μm). straight
Molding pressure 1 ton / cm in a mold with a diameter of 12mm²One
A cylindrical pellet was produced by axial pressing. Then platinum
Bake at densification temperature (1460 ° C) for 2 hours in air on a plate
Ba_6-3xSm_{8 + 2x}Ti₁₈O
₅₄Was prepared.

[0029]

[Table 1]

With respect to the obtained microwave dielectric porcelain composition, the crystal structure distortion was determined from data obtained by powder x-ray diffraction (see FIG. 1). The dielectric constant ε _r , the quality factor Q · f value, and the temperature coefficient τ _f are represented by Hakk
According to the i and Coleman method (Hack and Coleman method) (refer to “Research Report on Standardization of Performance Evaluation of New Ceramic Materials” published by Japan Fine Ceramics Association in March 1992). It was measured. The measurement frequency is 4-5G
Hz. The temperature coefficient τ _f was determined from a change in resonance frequency in a temperature range of +20 to + 80 ° C. The measurement results are shown in Table 1 above and in FIGS.

Further, other Ba _6-3x R _{8 + 2x} Ti
About ₁₈ O _54, prepared R = La, Nd, in the case of Pr were similarly measured microwave dielectric properties. The measurement results are shown in Tables 2 to 4 and in FIGS. Here, Table 2 has R = La, Table 3 has R = Nd, and Table 4 has R = La.
The case of Pr is shown.

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

From these results, the quality factor is 0.5 ≦ x
It clearly shows a high value in the range of ≦ 0.7, and particularly, x =
2/3 shows the maximum value of each component (see FIG. 2). Also, other dielectric properties have good values (see FIGS. 3 and 4).

As described above, according to the microwave dielectric porcelain composition of the present embodiment, it is possible to greatly improve the quality coefficient while maintaining a high dielectric constant and a low temperature coefficient.

In this embodiment, even when Eu and Gd are used for R, the same effects as those of this embodiment can be obtained.

<Second Embodiment> The microwave dielectric porcelain composition of the present embodiment is composed of BaCO ₃ , Sm ₂ O ₃ , and TiO.
24 hours in ethanol wet mixture of _two powder samples were weighed to a stoichiometric composition with a ball mill to prepare a _{Ba 4 Sm 9.33 Ti 1 8 O} 54 solid solution for 2 hours and calcined at 1000 ° C. After grinding . Ba ₄ Sm _9.33 Ti ₁₈ O ₅₄ was prepared so that the composition (the values of x and y) in Table 5 could be obtained.
TiO ₂ ymol was added to 1 mol of the solid solution, and after calcining, the mixture was wet-mixed in an alumina mortar for 2 hours. Thereafter, PVA was added as a binder, and the mixture was granulated and molded into a size of 12 mm in diameter and 8 mm in height. Test Example 5-1 is 14
Others were fired at 1350 ° C. for 2 hours at 60 ° C., and then mirror-polished so that the height / diameter was し た, to produce pellets for evaluation.

Ba _6-3x R thus obtained
About _{8 + 2x Ti 18 O 54 ·} yTiO 2 complex,
Hakki and Coleman method (both short-circuited dielectric resonator method, Heisei 4
March 1999, published by the Japan Fine Ceramics Association, “Research Report on Standardization of Performance Evaluation of New Ceramic Materials”), microwave dielectric property evaluation in TE ₀₁₁ mode, density measurement by Archimedes method, powder x
The precipitated phase was identified by X-ray diffraction and SEM observation was performed.

[0040]

[Table 5]

The measurement results are shown in Table 5 above, and graphs showing changes in the temperature coefficient, the quality coefficient, and the dielectric constant with respect to the value of y are shown in FIGS.

As shown in FIG. 6, the Q · f value was not added (y
= 0), the dielectric constant is maintained at about 1000 GHz, and the dielectric constant is maintained at about ε _r = 80 up to y = 1.4 as shown in FIG. 7, but decreases as the value of y increases and y =
At 1.9, ε _r = about 70.

Then, when y = 1.4, τ _f = −0.
It was 3. The Q · f value at this time is 11860 GHz,
The dielectric constant ε _r was 81.5.

Further, at y = 1.5, τ _f = 0.0
Was able to achieve. The Q · f value at this time is 118
The frequency was 55 GHz and the dielectric constant ε _r was 82.0.

In addition, all the samples fired at 1350 ° C. were sufficiently hardened from the results of the density measurement.
It has been confirmed that the sintering temperature can be lowered to 1350 ° C. as compared with a pure solid solution because of having high dielectric properties. Further, from the result of identification of the precipitated phase by powder x-ray diffraction and the result of SEM observation, Ba ₄ Sm _{9.3 3}
It was confirmed that a two-phase coexistence state of a Ti ₁₈ O ₅₄ solid solution and TiO ₂ was possible.

Thus, Ba _6-3x R _{8 + 2x} Ti
₁₈ O ₅₄ is a composite of a solid solution and TiO ₂ microwave dielectric ceramic composition can be lowered the firing temperature,
In addition, the quality factor and the dielectric constant are improved, and in particular, Ba ₄ Sm
_{9.33 By making} the two-phase coexistence state of the Ti ₁₈ O ₅₄ solid solution and TiO ₂ , the temperature coefficient becomes zero due to the effect of TiO _2.
, And can be set to 0.

In this embodiment, for example, by increasing the firing time, Ba _{6-3 x} R _{8 + 2x} Ti
It was found that when a two-phase coexistence state of _{18 O54} solid solution and TiO ₂ was added and a phase equilibrium was reached, Ba ₂ Ti ₉ O _{20 as} a stable phase was precipitated as a third phase. Since the temperature coefficient is not improved when the phase of TiO ₂ is reduced, it is necessary to maintain the phase of TiO ₂ , especially in order to improve the temperature coefficient and approach zero, thereby more surely maintaining the temperature coefficient. It became possible to adjust.

In this embodiment, the solid solution Ba ₄ Sm
_9.33 Ti ₁₈ O ₅₄ was used, but other Ba _6-3x
A similar effect can be obtained by using a solid solution of R _{8 + 2x} Ti ₁₈ O ₅₄ . Further, although Sm is used for R, La, Pr, Nd, Eu, and Gd having similar properties may be used.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a composition x and a strain of a solid solution according to a first embodiment.

FIG. 2 is a graph showing a change in a quality factor with respect to a composition x in the first embodiment.

FIG. 3 is a graph showing a change in a dielectric constant with respect to a composition x in the first embodiment.

FIG. 4 is a graph showing a change in a temperature coefficient with respect to a composition x in the first embodiment.

FIG. 5 is a graph showing a change in a temperature coefficient with respect to a composition y in the second embodiment.

FIG. 6 is a graph showing a change in a quality factor with respect to a composition y in the second embodiment.

FIG. 7 is a graph showing a change in a dielectric constant with respect to a composition y in the second embodiment.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Susumu Nishigaki 1-1607 Shinonokaze, Midori-ku, Nagoya-shi, Aichi F-term (reference) 4G031 AA06 AA07 AA09 AA11 BA09 5E001 AE02 AE03 AH05 AH09 AJ02 5G303 AA02 AA05 AA10 AB06 AB08 AB11 AB20 BA12 CA01 CB03 CB15 CB22 CB26 CB35 CB41 CB43 DA01 5J006 HC07

Claims (5)

[Claims] 1. Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄
(Where R is one of La, Pr, Nd, Sm, Eu, and Gd), wherein x is 0.5 ≦ x ≦ 0.7. A microwave dielectric porcelain composition. 2. The microwave dielectric porcelain composition according to claim 1, wherein x = 2/3. 3. The microwave dielectric porcelain composition according to claim 1 or 2, wherein Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄ solid solution and TiO.
A complex with _{2, Ba 6-3x R 8 + 2x} Ti
₁₈ O ₅₄ .yTiO ₂ (R = La, Pr, Nd, S
m, Eu, or Gd), and 0.5 ≦
A microwave dielectric porcelain composition, wherein x ≦ 0.7 and 0 <y ≦ 2.0. 4. The microwave dielectric porcelain composition according to claim 3, wherein 1.2 ≦ y ≦ 1.8. 5. A desired powdery raw material is mixed and calcined to obtain Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄ (0.5
≦ x ≦ 0.7) to produce a solid solution, method for producing a microwave dielectric ceramic composition characterized in this that the firing by the addition of TiO _2.