JP2000243138A - Microwave dielectric porcelain composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave dielectric porcelain composition having a high dielectric constant and a small absolute value of temperature coefficient. SOLUTION: A tungsten bronze type solid solution system represented by Ba6-3xR8+2x-y/3LiyTi18O54 (R = any one of Sm, Nd, Pr and La) produced by solid dissolving Li in a tungsten bronze type solid solution system represented by Ba6-3xR8+2xTi18O54 is present as a single phase solid solution within the range of 0<=y<=7. The Li ion contributes to ion polarization, whereby a microwave dielectric porcelain composition having a high dielectric constant and a low absolute value of temperature coefficient is provided while keeping a high quality coefficient. This dielectric porcelain composition has sufficient electric characteristic even in low frequency area, and is also usable as a temperature compensating capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave dielectric ceramic 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, MgO-CaO-T have been used as microwave dielectric ceramic compositions of this kind.
An iO ₂ system and a 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 such as a mobile phone and a mobile phone and satellite communication. When used as a dielectric resonator or the like, a high quality coefficient in a high frequency region, a high dielectric constant, and a temperature coefficient of a low resonance frequency are required.

[0003]

However, in recent years,
There is a demand for high performance and miniaturization of communication devices and the like, which depend on the characteristics of microwave dielectric porcelain compositions.

[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 make a communication device usable for a long time in mobile communication, low loss, that is, a high quality factor Q · f value is required.

Since the wavelength of an electromagnetic wave in a dielectric is shortened in inverse proportion to the square root of the relative permittivity as compared with that in a vacuum, it is necessary to reduce the size of the dielectric when used in a microwave dielectric resonator. In particular, a material having a high dielectric constant is required.

Further, since it is not preferable that the resonance frequency changes due to a change in the surrounding temperature when the resonator is used as a resonator, the temperature coefficient of the resonance frequency (hereinafter simply referred to as "temperature coefficient") in a high frequency region is low. Those with a small absolute value are required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a microwave dielectric porcelain composition having a high quality factor, and further having a high dielectric constant and a low absolute value of a temperature coefficient. .

[0008]

In order to achieve the above object, a microwave dielectric ceramic composition according to claim 1 is characterized in that:
a _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄ (R = Sm, N
_d, Pr, _Ba 6-3x dissolved therein in a solid state Li to any) solid solutions of _{La R 8 + 2x-y /} 3 Li y Ti 1 8 O
A tungsten bronze-type solid solution represented by ₅₄ , characterized in that 0.5 ≦ x ≦ 0.7 and 0 <y ≦ 7.

The invention according to claim 2 is the invention according to claim 1.
In the microwave dielectric porcelain composition described in, in particular,
It is characterized in that the range of y is 0 <y ≦ 1.

The crystal structure of the tungsten bronze-type solid solution is such that TiO ₆ octahedra shares a vertex to form a three-dimensional skeletal structure, and has a 2 × 2 perovskite block in a crystal lattice. The crystal structure has a coordination polyhedron into which these ions can enter. That is, A1 seat in the 2 × 2 perovskite block and A in the pentagonal column formed between the perovskite blocks.
Two seats and a seat C in a triangular column similarly formed between the blocks. Further, there are 10 A1 seats, 4 A2 seats, and 4 C seats in the unit cell of the basic period, and the basic structural formula is [(R, Ba, Li, V) ₁₀ ].
_A1 [(Ba, V) ₄ ] _A2 [(Li, V) ₄ ] _C Ti
₁₈ O ₅₄ . Here, V is an empty seat.

Ba _6-3x R _{8 + 2x−y / 3} Li _y T
As a typical example of i ₁₈ O ₅₄ solid solution system, here, R
= Sm, x = ２ will be described. x = 2 /
The composition _No. 3 has the largest quality factor (Q · f value) in the Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄ solid solution system, and has a sufficient quality factor in the range of 0.5 ≦ x ≦ 0.7. x
Ba ₄ Sm _{(28-y) / 3} Li _y Ti obtained by adding Li to a Ba ₄ Sm _28/3 Ti ₁₈ O ₅₄ solid solution of = _{2/3
The 18} O ₅₄ solid solution system exists as a single-phase solid solution in the range of 0 <y ≦ 7, and the structural formula and cation atomic arrangement corresponding to its composition (y value) are as shown in the following section. It is.

First, Ba in which Li is not substituted
_{6-3x R 8 + 2x Ti 18 O} 54 x in solid solution system
Ba ₄ Sm _28/3 Ti ₁₈ O = 2/3 composition
₅₄ solid solution, that is, when y = 0, A1 seat has Sm and V
, The A2 seat is _occupied by Ba and the C seat is vacant, so [Sm _28/3 V _2/3 ] _A1 [Ba ₄ ] _A2
[V ₄ ] _C Ti ₁₈ O ₅₄ is obtained.

Then, Ba in which a part of Sm is substituted by Li
₄Sm_{(28-y) / 3}Li_yTi ₁₈O₅₄To solid solution
In the case of 0 <y ≦ 1, the replaced Li enters the A1 seat.
And seat C remains vacant, so [Sm
_{(28-y) / 3}Li_yV_{2/3 (1-x)}]_A1[B
a₄]_A2[V₄]_CTi₁₈O₅₄Becomes

In particular, when y = 1, [Sm ₉ Li ₁ ]
_{A1 [Ba 4] A2 [V} 4] becomes _{C Ti} 1 _{8 O 54,}
All vacant A1 seats are occupied by ions.

Further, when 1 <y ≦ 7, a part of Sm is
Replaced Li replaces Sm of A1 seat, and until now
Entering the vacant seat C, [Sm_{(28-y) / 3}
Li _{(2 + y) / 3}]_A1[Ba₄]_A2[Li
_{2/3 (y-1)}V_{4-2 / 3 (y -1)}]_CTi₁₈
O₅₄Becomes

In the microwave dielectric ceramic composition configured as described above, the A1 seat is larger than the C seat, and since the Sm ion has a larger ionic radius than the Li ion, small Li ions are larger than A1 seats. Upon entering the seat, the added Li ions contribute to ionic polarization.
When Li ions enter the C seat, the C seat expands and A1
The seat is compressed.

[0017]

As described above, the microwave dielectric porcelain composition according to the first aspect can greatly improve the dielectric constant. Further, the absolute value of the temperature coefficient can be reduced.

The temperature coefficient of the microwave dielectric porcelain composition according to the second aspect of the present invention can be reduced to 0 particularly when the composition is in the range of 0 <y ≦ 1.

[0019]

EXAMPLES microwave dielectric ceramic composition according to the present _invention, dissolved therein in a solid state Li tungsten bronze type solid solution system represented by _{Ba 6-3x R 8 + 2x Ti 1} 8 O 54 B
is a solid solution system represented by _{a 6 -3x R 8 + 2x-} y / 3 Li y Ti 18 O 54. In this embodiment described below,
Especially Out R = Sm of the solid solution system, x = 2/3 which is a composition _{Ba 4 Sm (28-y)} / 3 Li y Ti 18
An _O54 solid solution was prepared and evaluated.

Ba ₄ Sm _{(28-y) / 3} Li _y Ti
_The method for producing the ₁₈ O ₅₄ solid solution firstly involves high purity BaC
O ₃ , TiO ₂ , Sm ₂ O ₃ , and Li ₂ CO ₃ powder samples are weighed so that the respective compositions (x and y values) in Table 1 are obtained.

[0021]

[Table 1]

The weighed sample was wet-mixed with ethanol for 2 hours, crushed, and then crushed at 1000 ° C. in air.
And bake for 2 hours. After calcining, the mixture is pulverized again, and PVA is added as a binder and granulated to 300 μm. The mixture was placed in a mold, and a pressure of 1 ton / cm ² was applied thereto to produce a cylindrical pellet having a diameter of 12 mm. And firing temperature 1350 ~
Sintering is performed at 1460 ° C. for 2 hours, and the upper and lower surfaces are polished in parallel so that thickness / diameter = 直径.

With respect to the microwave dielectric properties of the manufactured microwave dielectric porcelain composition, Hak
According to the ki 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). A measurement was made. The measurement results are shown in Table 1 and FIGS.

As shown in FIG. 1, it has been found that the temperature coefficient τ _f gradually increases as the value of y increases. Also, as shown in FIG. 2, the dielectric constant ε _r was ε _r = 79.6 when y = 0, but as the value of y increased, the value of ε _r also increased and y = When it exceeds 8, it decreases sharply. The quality factor Q · f value is, as shown in FIG.
It was found that as the value of increased, it decreased.

Further, when the phases were identified by X-ray powder diffraction, it was found that when y = 0 to y = 7, the phase was a single phase and formed a solid solution. It was found that two phases precipitated.

Therefore, in the present embodiment, the useful range of the composition y for the microwave dielectric ceramic composition is 0 <y ≦ 7.
The dielectric constant is improved, and the absolute value of the temperature coefficient can be reduced. In particular, when the composition is 0 <y ≦ 1, the temperature coefficient approaches 0 in addition to the high quality coefficient and the high dielectric constant. In particular, for a composition with y = 0.3, a temperature coefficient τ _f = 0 is achieved, and a dielectric constant ε _r = 83,
It is possible to provide a microwave dielectric porcelain composition having an improved dielectric characteristic having a quality factor of Q · f = 5000 GHz.

For this reason, according to the microwave dielectric porcelain composition of the present embodiment, it is excellent as a microwave dielectric resonator, the resonator can be miniaturized, and a cellular phone, a car phone, a satellite broadcast Useful for receivers and the like. Further, the microwave dielectric porcelain composition of the present example has sufficient electric characteristics even in a low frequency region, and is used as a capacitor for temperature compensation.

In this embodiment, Sm is used for R. However, when Nd, Pr, and La having similar chemical properties are used for R, a microwave dielectric ceramic composition which similarly improves the dielectric properties is also used. Is obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing a change in a temperature coefficient with respect to a composition y of a microwave dielectric porcelain composition according to an example.

FIG. 2 is a graph showing a change in a dielectric constant with respect to a composition y.

FIG. 3 is a graph showing a change in a quality factor with respect to a composition y.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Susumu Nishigaki 1-1607 Shinonokaze, Midori-ku, Nagoya-shi, Aichi F-term (reference) 4G031 AA01 AA06 AA07 AA09 AA11 BA09 5E001 AB01 AE00 AE02 AE03 AE04 AH05 AH09 AJ02 5G303 AA02 AA05 AA10 AB06 AB08 AB11 BA12 CA01 CB03 CB15 CB16 CB22 CB26 CB35 CB41 5J006 HC07

Claims (2)

[Claims] 1. Ba _6-3x R _{8 + 2x} Ti ₁₈ O ₅₄
(R = Sm, Nd, Pr, or La) Ba _6-3x R _{8 + 2x −y / 3} L in which Li is dissolved in a solid solution.
A microwave dielectric ceramic composition, which is a tungsten bronze type solid solution represented by i _y Ti ₁₈ O ₅₄ , wherein 0.5 ≦ x ≦ 0.7 and 0 <y ≦ 7. 2. The microwave dielectric porcelain composition according to claim 1, wherein 0 <y ≦ 1.