JPH0692727A - Microwave dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a dielectric porcelain composition capable of optionally and stably controlling so as to bring tauf to '0' or a desired value between a plus side and a minus side with '0' as a center while keeping epsilonr and Qu in a specific range and small in the dispersion of performance even if firing temp. is fluctuated. CONSTITUTION:This porcelain composition has a composition expressed by a formula (x)MgTiO3.(1-x)CaTiO3 (where, 0.923<=(x)<=0.940), as a main component and is made by adding 2-4 pts.wt. Ta2O5 to 100 pts.wt. (x)MgTiO3.(1-x) CaTiO3. When (x) is 0.927-0.935 and the adding quantity of Ta2O5 is 3wt.% (firing temp.; 1300-1400 deg.C), Qu is 3920-4260, tauf is -8.5-(+2.3) (ppm/ deg.C) and epsilonr is 19.7-216 and even in the case of changing the firing temp., the dispersion of the performance is extremely small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave dielectric porcelain composition, and more specifically, to a high temperature of unloaded Q (hereinafter simply referred to as "Q") while maintaining a temperature coefficient of resonance frequency ( Hereinafter, simply referred to as τf) can be brought close to zero, and the mixing ratio of CaTiO ₃ and Ta ₂ O
By adjusting the addition amount of ₅ , τf can be arbitrarily controlled to the plus side and the minus side around zero, and even if the firing temperature is changed by the addition of Ta ₂ O ₅ , microscopic variation is small. The present invention relates to a wave dielectric ceramic composition. INDUSTRIAL APPLICABILITY The present invention is utilized for impedance matching of dielectric resonators, microwave integrated circuit substrates, various microwave circuits, etc. in the microwave region.

[0002]

2. Description of the Related Art Microwave dielectric porcelain compositions (hereinafter simply referred to as dielectric porcelain compositions) tend to increase in dielectric loss as the operating frequency becomes higher.
A dielectric ceramic composition having a large Qu in the micro frequency range is desired. As a conventional dielectric porcelain material, a dielectric porcelain composition having a crystal structure containing two phases of a perovskite phase and an ilmenite phase (Japanese Patent Laid-Open No. 2-129065),
A dielectric ceramic composition (Japanese Patent Laid-Open No. 52-118599) in which MgTiO ₃ and TiO ₂ contain a predetermined amount of CaTiO ₃ is known.

[0003]

However, in the former dielectric ceramic composition, Nd ₂ O ₃ , La ₂ O ₃ , PbO and Zn are used.
In addition to containing many other components such as O, Qu is not always a large value. In the latter dielectric ceramic composition, TiO 2
₂ is included as an essential component, and the mixing amount of CaTiO ₃ is 3 to
In the range of 10% by weight, τf greatly changes from +87 to -100, and there is a problem that it is difficult to adjust a small value near 0.

The present invention solves the above-mentioned problems, and maintains ε _r and Qu within a practical characteristic range by adjusting the compounding ratio of CaTiO ₃ and the addition amount of Ta ₂ O _5. , Τf can be controlled to a desired value on the plus side and the minus side centering on zero or close to zero, and the performance can be improved even if the firing temperature changes due to the addition of Ta ₂ O _5. An object is to provide a dielectric ceramic composition having a small variation.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have proposed a dielectric porcelain composition in which τf can be brought close to zero while maintaining a high Qu and the composition has stable quality even when the firing temperature is changed. As a result of various studies on CaTi
The inventors have found that this drawback can be solved by adjusting the mixing (composition) ratio of O ₃ and Ta ₂ O ₅ , and have completed the present invention.

That is, the dielectric ceramic composition of the present invention is xM
gTiO ₃ · (1-x) CaTiO ₃ [however, 0.92
3 ≦ x ≦ 0.940] as a main component, and the above xMgTiO ₃ · (1-x) CaTiO ₃ 10
It is characterized in that 2 to 4 parts by weight (hereinafter referred to as 2 to 4% by weight) of Ta ₂ O ₅ is added to 0 parts by weight. When x is smaller than 0.923, τf takes a large positive value and Qu becomes small, and conversely 0.94.
This is because τf takes a large negative value when it exceeds 0, which is not preferable. Further, in particular, x is 0.927 to 0.9.
35, if the added amount of Ta ₂ O ₅ is 3% by weight, Q
u is 3920 to 4260, and τf is -8.5 to +2.3.
(Ppm / ° C.), ε _r is 19.7 to 21.6, and the variation in performance is very small even if the firing temperature is changed.
preferable.

As the mixing ratio of CaTiO ₃ increases, τf moves from a negative value to a positive direction (FIG. 3), and ε
_r tends to increase (Fig. 2), while Qu tends to decrease (Fig. 1). Further, as shown in FIG. 7, by adding Ta ₂ O _5, a sintered body having a high density can be manufactured even if it is fired at a low temperature (for example, 1300 to 1325 ° C.). Further, even if the firing temperature is variously changed within the range of 1300 to 1400 ° C., stable quality can be obtained (FIGS. 4 to 1).
0). From the above, in the above proper mixing range of CaTiO ₃ and Ta ₂ O ₅ , the performances thereof are well balanced and the quality is stable.

[0008]

EXAMPLES The present invention will be specifically described below with reference to examples. MgO powder (purity; 99.4%), C as CaO
aCO ₃ powder (purity; 99%), TiO ₂ powder (purity;
99.98%), Ta ₂ O ₅ powder (purity; 99.9%)
As a starting material, as shown in Tables 1 and 2 and FIGS. 1 and 4, the composition formula xMgTiO _3. (1-x) CaTiO ₃ +
y wt% Ta ₂ O ₅ [xMgTiO ₃ · (1-x) Ca
It means Ta ₂ O ₅ y parts by weight with respect to 100 parts by weight of TiO ₃ . ] A predetermined amount (about 500 g as a total amount) was weighed and mixed so that each x and y in the above] had a changed composition. After that, after dry-mixing (20 to 30 minutes) and pulverization with a mixer, 2 at a temperature of 1100 ° C. in an air atmosphere.
I calcined for an hour. Then, an appropriate amount of organic binder (29 g) and water (300 to 400 g) were added to the calcined powder, and 2
It was crushed with a 0 mmφ alumina ball at 90 rpm for 23 hours. After that, vacuum freeze-drying (about 0.4 Torr, 4
Granulation at 0 to 50 ° C. for about 20 hours), and using the granulated raw material at a pressing pressure of 1000 kg / cm ² for 19
It was formed into a cylindrical shape of mmφ × 11 mmt (thickness).

[0009]

[Table 1]

[0010]

[Table 2]

Next, the molded body was placed in the atmosphere at 500 ° C. for 3 days.
After degreasing at a certain time, 1300-300 shown in each table and figure
It was fired at each temperature in the range of 1400 ° C. for 4 hours, and finally both end faces were polished into a cylindrical shape of about 16 mmφ × 8 mmt (thickness) to obtain a dielectric sample. Then, for each sample, ε _r (relative permittivity), Qu and τ f, and the sintered density were measured by the Archimedes method by a parallel conductor plate type dielectric cylinder resonator method (TE ₀₁₁ MODE) or the like. The resonance frequency is 6 GHz. These results are shown in Table 1, Table 2 and FIGS.
As shown in FIG. Also, as an example, 0.93 MgTiO 3
The ₃ · 0.07CaTiO ₃ · _3% by weight of Ta ₂ O results of X-ray diffraction in the case of ₅ (4 hours firing at 1300 ° C.) 11 and shown in FIG. 12 (4 hours firing at 1350 ° C.).

According to these results, xMgTiO ₃ ·
When x of (1-x) CaTiO ₃ is small, the Qu value tends to be small, but conversely, τf and ε _r tend to be large on the plus side. Although the sintering density tends to increase as the firing temperature increases, it becomes flat with respect to the firing temperature as the amount of Ta ₂ O ₅ added increases. Baking temperature is 1300-14
At 00 ° C, when x is in the range of 0.923 to 0.940, τf is +8 to -13, ε _r is 19 to 22, and Qu is 3.
It is preferable because it shows a practical characteristic range of 850 to 4380. Especially when x is 0.930 and the amount of Ta ₂ O ₅ added is 3% by weight, for example, the firing temperature is 1325 ° C to 1375 ° C.
In the case of, as shown in FIGS. 1 to 6 and Tables 1 and 2,
τf is −0.1 to +0.65 ppm / ° C., ε _r is 21.
1 to 21.4 and Qu are 4030 to 4130, which shows a particularly excellent performance balance and has a very small variation. On the other hand, when CaTiO ₃ is not contained, Qu
Although the value is large, ε _r is small and τ f is -25.
It is unfavorable because it becomes extremely small on the minus side, which is about -44.

According to the analysis method based on the presence / absence of X-ray diffraction peaks shown in FIGS. 11 and 12, the structure of the present invention contains MgTiO ₃ (◯) and CaTiO ₃ (●),
Other peaks are MgTi ₂ O ₅ (▽),
It shows that it does not contain O, CaO, and TiO ₂ .

Further, although not shown, according to the result of the electron micrograph, the particle diameter becomes larger as the firing temperature increases (1300 ° C .; 2.5 μm, 1350 ° C .; 3.7 μm).
m, 1400 ° C .; 6.5 μm, both measured by the Intercept method), and the number of pores is reduced, indicating that densification is completed at 1350 ° C. The fracture surface showed intergranular fracture at 1300 ° C and intragranular fracture at 1350 ° C or higher. In addition, the surface texture is such that, as the firing temperature increases, huge particles (normal particles, particle size 10 to 50 μm) and angular particles (1 to 10 μm)
Less than 1 μm). As a result of EDS analysis (Energy Dispersive Spectrum), Mg, Ca, Ti, and Si are detected from normal particles, and M is detected from angular particles.
g, Ca, Ti, and Ta were detected. This angular particle is T
It is considered to be a compound of a. Also, Si
The components are considered to have been mixed from the starting materials.

The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application. That is,
Various calcination conditions such as the calcination temperature and the calcination conditions such as the calcination temperature can be selected.

[0016]

As described above, the dielectric porcelain composition of the present invention maintains the Qu and ε _r in the practical (high) characteristic range, and adjusts the CaTiO ₃ compounding ratio to adjust τf. Can be controlled to a desired value on the plus side and the minus side with zero as the center, and τf can be stably adjusted to near zero. Furthermore, by adding Ta ₂ O ₅ , it is possible to obtain a sintered body having a high density and high quality even if the firing temperature is changed variously. Therefore, depending on the purpose, CaTiO ₃ and Ta ₂ O
The mixing ratio of ₅ can be changed.

[Brief description of drawings]

FIG. 1 [xMgT produced at a firing temperature of 1350 ° C.
iO ₃ · (1-x) CaTiO ₃ +3 wt% Ta
₂ O ₅ ] In a porcelain composition, it is a graph showing the relationship between x and Qu.

FIG. 2 is a graph showing the relationship between x and ε _r in the porcelain composition shown in FIG.

FIG. 3 is a graph showing the relationship between x and τf in the porcelain composition shown in FIG.

FIG. 4 is manufactured by firing at each firing temperature [0.
93MgTiO ₃ · 0.07CaTiO ₃ + (2-4)
₅ is a graph showing the relationship between the amount of Ta ₂ O ₅ and Qu in a wt% Ta ₂ O ₅ ] porcelain composition.

FIG. 5 shows Ta ₂ O ₅ in the porcelain composition shown in FIG.
It is a graph which shows the relationship between quantity and ε _r .

FIG. 6 shows Ta ₂ O ₅ in the porcelain composition shown in FIG.
Is a graph showing the relationship between the amount and tau _f.

FIG. 7 [0.93MgTiO ₃ .0.07CaTiO _3
3 + (0 to 4) wt% Ta ₂ O ₅ ] A ceramic composition showing a relationship between firing temperature and Qu.

FIG. 8 is a graph showing the relationship between the firing temperature and ε _r in the porcelain composition shown in FIG.

9 is a graph showing the relationship between firing temperature and τf in the porcelain composition shown in FIG.

10 is a graph showing the relationship between the firing temperature and the sintered density in the porcelain composition shown in FIG.

FIG. 11 [0.93MgTiO ₃ .0.07CaTi
O ₃ +3 wt% Ta ₂ O ₅ , firing temperature: 1300 ° C.] A graph showing the X-ray diffraction results of the porcelain composition.

FIG. 12 [0.93MgTiO ₃ .0.07CaTi
O ₃ +3 wt% Ta ₂ O ₅ , firing temperature: 1350 ° C.] A graph showing the X-ray diffraction results of the porcelain composition.

Claims (1)

[Claims] 1. xMgTiO _3. (1-x) CaTiO
₃ [however, the composition represented by 0.923 ≦ x ≦ 0.940] is the main component, and the above xMgTiO ₃ · (1-
x) A microwave dielectric ceramic composition containing ₂ to 4 parts by weight of Ta ₂ O ₅ added to 100 parts by weight of CaTiO ₃ .