JPH06107457A - Microwave dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a microwave dielectric porcelain composition capable of properly and stably controlling tauf to bring close to zero or to a desired value of plus side and minus side with zero as the center while keeping epsilonr and Qu in a practical specific property range. CONSTITUTION:This composition contains a component expressed by xMgTiO3.(1-x)CaTiO3 (wherein, 0.925<=x<=0.940) as an essential component and furthermore 1-6 pts.wt. (particularly 2-4 pts.wt.) Nb2O5 per 100 pts.wt. xMgTiO3.(1-x)CaTiO3 by adding thereinto. Particularly, in the case that x is 0.930 and the adding quantity of Nb2O5 is 2wt.% Qu (6GHx) is 3980-4320, tauf is -3.69 to (+0.52)ppm/ deg.C and epsilonr is 19.05-21.51 at the time of firing at 1275-1400 deg.C.

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, and more specifically, to a temperature coefficient () of a resonance frequency while maintaining an unloaded Q (hereinafter simply referred to as "Q") at a high value. (Hereinafter simply referred to as τf)) can be brought close to zero, and by further adjusting the mixing ratio of CaTiO ₃ , τf can be arbitrarily controlled to the plus side and the minus side centering on zero, and Nb _{The present} invention relates to a microwave dielectric ceramic composition having high quality even if it is fired in a wide temperature range by adding ₂ O ₅ . 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. By adjusting the mixing ratios of CaTiO ₃ and Nb ₂ O ₅ , ε _r and Qu can be maintained within a practical characteristic range, and τ f can be reduced. It can be controlled to a desired value on the plus side and the minus side centered around zero, centered around zero, and can be controlled in a stable manner. High quality even when fired in a wide temperature range by adding Nb ₂ O _5. An object of the present invention is to provide a dielectric ceramic composition comprising

[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 Nb 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
5 ≦ x ≦ 0.940] as a main component, and the above xMgTiO ₃ · (1-x) CaTiO ₃ 10
It is characterized in that 1 to 6 parts by weight of Nb ₂ O ₅ is added to 0 parts by weight. If x is smaller than 0.925, τf takes a large positive value, and Qu becomes small, and conversely, if it exceeds 0.940, τf takes a large negative value, which is not preferable. Also, in particular, the above x
Is 0.930 and the amount of Nb ₂ O ₅ added is 2% by weight, when fired at 1275 to 1400 ° C., Qu is 3980 to 4320 and τf is −3.69 to + 0.52p.
Since pm / ° C. and ε _r are 19.05 to 21.51, high quality ones can be stably secured even if fired in a wide temperature range.

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. 4 to 6, Nb ₂ O
Addition of ₅ does not significantly change Qu and εr, but tends to decrease τ _f . In particular, CaTiO ₃
When the mixing ratio (x) is 0.07, the addition amount of Nb ₂ O ₅ is about 2% by weight and τ _f is about 0 ppm / ° C., which is very preferable. 7 to 11 and Tables 2 and 3
As shown in (1), the addition of Nb ₂ O ₅ makes it possible to produce a sintered body having stable performance and high sintering density even if it is fired in a wide temperature range. Therefore, the addition amount of Nb ₂ O ₅ is particularly 1 to
When it is 4% by weight (especially around 2% by weight), it is more excellent in balance of excellent performance and stable sinterability. From the above, in the above proper mixing range of CaTiO ₃ and Nb ₂ O ₅ , these properties are excellent and balanced, and stable quality is obtained.

[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%), Nb ₂ O ₅ powder (purity; 100%) as a starting material, and as shown in Tables 1 to 3 and FIGS. 1 and 4, the composition formula xMgTiO _3. (1-x) CaTiO ₃ +
y wt% Nb ₂ O ₅ [xMgTiO ₃ · (1-x) Ca
It means Nb 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. still,
Table 1 shows the amount of MgTiO ₃ added, and Tables 2 and 3 show the amount of Nb ₂ O ₅ added.
Then, after dry-mixing (20 to 30 minutes) and primary pulverization with a mixer, calcination was performed at a temperature of 1100 ° C. for 2 hours in an air atmosphere. Then, an appropriate amount of an organic binder (29 g) and water (300 to 400 g) were added to the calcined powder, and an alumina ball having a diameter of 20 mm was used at 90 rpm for 2 minutes.
Crushed for 3 hours. After that, vacuum freeze-drying (about 0.4 To
rr, 40 to 50 ° C., about 20 hours), and the formed raw material was molded into a column of 19 mmφ × 11 mmt (thickness) at a pressing pressure of 1000 kg / cm ² .

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

Next, the molded body was placed in the atmosphere at 500 ° C. for 3 days.
Degreasing in time, then 1275-140 shown in each figure
Baking at each temperature in the range of 0 ° C. for 4 hours, and finally, polishing both end faces into a cylinder of about 16 mmφ × 8 mmt (thickness),
Dielectric samples (Nos. 1 to 24 in Table 1 and Tables 1 and 3)
No. 1-36). Then, for each sample, the relative permittivity (hereinafter, simply referred to as ε _r ), Qu and τ f, and the sintering density were measured by the Archimedes method by a parallel conductor plate type dielectric cylinder resonator method (TE ₀₁₁ MODE) or the like. It was measured. The resonance frequency is 6 GHz. The results are shown in Tables 1 to 3 and FIGS. Also, as an example,
Figure 12 (0.93MgTiO ₃ · 0 The results of X-ray diffraction of when the 0.93MgTiO ₃ · 0.07CaTiO _3.
2, 4 or 6% by weight of Nb _{2 with} respect to 07CaTiO ₃ .
Containing O ₅ and baked at 1350 ° C. for 4 hours).

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. The sintering density tends to increase as the firing temperature increases, but it does not change much even if the firing temperature is changed as the amount of Nb ₂ O ₅ added increases. Also, Nb
The addition of ₂ O ₅ does not significantly change Qu and εr, but tends to reduce τ _f . Therefore, Nb ₂
Addition of O ₅ gives τ _f without degrading the performance of Qu and εr.
Suitable for adjustment of. Further, when Nb ₂ O ₅ is not added, the characteristics cannot be measured when the firing temperature is low (1275-1325 ° C.) (Table 3), and 1350-1400 ° C.
Although the characteristics can be measured even when fired at, τ _f is remarkably large [Table 2 and FIG. 6; 19.7 (N
o. 1), 17.5 (No. 7), 15.1 ppm / ° C
(No. 13)], the sintered density is also 1375 ° C. or 135
It becomes small when firing at 0 ° C. (No.
7 and No. 13).

When the firing temperature is 1300 to 1400 ° C. and the amount of Nb ₂ O ₅ added is 2% by weight, τf is +8.01 when x is in the range of 0.925 to 0.940.
~ -11.72 ppm / ° C, ε _r is 20.07-21.
86 and Qu are preferable because they show a practical characteristic range of 3900 to 4540. Especially when x is 0.930 and the amount of Nb ₂ O ₅ added is 2% by weight, for example, the firing temperature is 1350.
In the case of ℃ and 1375 ℃, τf is -0.16 ~
+0.51 ppm / ° C, ε _r 21.48 to 21.5
1 and Qu are 3980 to 4030, exhibiting a particularly excellent performance balance and exhibiting very little variation in performance. Further, regarding τf, since the rate of change with respect to the firing temperature is low, it is easy to adjust a small value near 0 ppm / ° C. On the other hand, when CaTiO ₃ is not contained, the Qu value is large, but ε _r is small, and τ f is −25 to −4.
4ppm / ℃, which is extremely small on the minus side,
Not preferable.

According to the analysis method based on the presence / absence of X-ray diffraction peaks shown in FIG. 12, the structure of the product of the present invention is MgTi.
It contains O ₃ (○) and CaTiO ₃ (●), and the other peaks are MgTi ₂ O ₅ (△), and MgO, CaO,
It shows that it does not contain TiO ₂ . Also, Nb
_No peak of ₂ O ₅ compound was detected. However, Nb
_{Although the} diffraction pattern is almost the same as the amount of ₂ O ₅ added, the amount of M added increases from 2% by weight to 6% by weight.
The peaks of gTiO ₃ and MgTi ₂ O ₅ were slightly shifted to the low angle side of 2θ (FIG. 12). Therefore, it is considered that Nb ⁵⁺ ions are solid-dissolved in MgTiO ₃ and MgTi ₂ O ₅ .

Further, although not shown, according to the result of the electron micrograph, the particle size becomes larger as the firing temperature increases (1275 ° C .; 2.6 μm, 1300 ° C .; 3.1 μ).
m, 1350 ° C .; 4.9 μm, 1400 ° C .; 6.1 μ
m, both are measured by the Intercept method), and the number of pores is reduced, indicating that densification is completed at 1350 ° C. All fracture surfaces showed intragranular fracture.

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. Also, the raw material that becomes CaO is the above-mentioned CaC.
Besides O ₃ , peroxides, hydroxides, nitrates and the like can be used. Similarly, for other oxides, other kinds of compounds which become oxides by heating can be used.

[0018]

As described above, the dielectric porcelain composition of the present invention maintains the Qu and ε _r in the practical (high) characteristic range while adjusting the mixing ratio of CaTiO ₃ and Nb ₂ O _5. By doing so, τf can be brought close to zero or can be arbitrarily controlled to a desired value on the plus side and the minus side centering on zero, and τf can be stably adjusted to near zero. Furthermore, by adding Nb ₂ O ₅ , it is possible to stably produce a high-quality and high-quality sintered body even if the firing temperature is variously changed within a wide temperature range. Therefore,
The mixing ratio of CaTiO ₃ and Nb ₂ O ₅ can be changed according to the purpose.

[Brief description of drawings]

FIG. 1 [xMgTiO _3. (1-x) CaTiO ₃ +2 produced at each firing temperature (1275-1400 ° C.)
₅ is a graph showing the relationship between x and Qu in a wt% Nb ₂ O ₅ ] porcelain composition.

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 + (0~6} )
₅ is a graph showing the relationship between the amount of Nb ₂ O ₅ and Qu in a wt% Nb ₂ O ₅ ] porcelain composition.

5] In the porcelain composition shown in FIG. 4, (0-6)
₅ is a graph showing the relationship between the weight% Nb ₂ O ₅ amount and ε _r .

FIG. 6 is a graph showing the relationship between (1 to 6% by weight) Nb ₂ O ₅ amount and τ _f in the porcelain composition shown in FIG. 4.

7 is a graph showing the relationship between the amount of (0-6 wt%) Nb ₂ O ₅ and the sintered density in the porcelain composition shown in FIG.

FIG. 8 [0.93MgTiO ₃ .0.07CaTiO
In ₃ + (1-6) wt% Nb ₂ O _5] ceramic composition is a graph showing the relationship between the firing temperature and Qu.

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

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

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

FIG. 12 [0.93MgTiO ₃ .0.07CaTi
O ₃ +2, 4 or 6 wt% Nb ₂ O ₅ ] X of porcelain composition
It is a graph which shows a line diffraction result.

Claims (1)

[Claims] 1. xMgTiO _3. (1-x) CaTiO
₃ [however, 0.925 ≦ x ≦ 0.940] is the main component, and the above xMgTiO ₃ · (1-
x) A microwave dielectric ceramic composition, wherein 1 to 6 parts by weight of Nb ₂ O ₅ is added to 100 parts by weight of CaTiO ₃ .