JP3162208B2 - Microwave dielectric porcelain composition - Google Patents

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 particularly, to a temperature coefficient of resonance frequency (hereinafter referred to as "Qu") while maintaining a high value of unloaded Q (hereinafter referred to simply as Qu). Hereinafter, simply referred to as τf) can be made close to zero, and by further adjusting the mixing ratio of CaTiO ₃ , τf can be arbitrarily controlled to a plus side and a minus side with zero as a center, and Nb can be controlled. _{The present} invention relates to a microwave dielectric porcelain composition having high quality even when baked in a wide temperature range by adding ₂ O ₅ . INDUSTRIAL APPLICABILITY The present invention is used for a dielectric resonator, a microwave integrated circuit board, impedance matching of various microwave circuits, and the like in a microwave region.

[0002]

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

[0003]

However, in the former dielectric ceramic composition, Nd ₂ O ₃ , La ₂ O ₃ , PbO, Zn
In addition to containing many other components such as O, Qu cannot always be said to be a large value. In the latter dielectric porcelain composition, TiO
₂ 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 a small value near 0 has a problem that adjustment is difficult.

The present invention solves the above-mentioned problems. By adjusting the mixing ratio of CaTiO ₃ and Nb ₂ O ₅ , the τf can be maintained while maintaining ε _r and Qu within a practical characteristic range. It can be arbitrarily and stably controlled to a desired value on the plus side and the minus side near zero or centered on zero. Further, even if it is fired in a wide temperature range by adding Nb ₂ O ₅ , high quality can be obtained. It is an object to provide a dielectric ceramic composition comprising:

[0005]

Means for Solving the Problems The present inventor has proposed a dielectric ceramic composition which can make τf close to zero while maintaining a high Qu, and has a stable quality even when the firing temperature is changed. As a result of various investigations, CaTi
The inventors have found that this disadvantage can be solved by adjusting the mixing (constitution) 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 comprises xM
gTiO ₃ · (1-x) CaTiO ₃ [provided that 0.92
5 ≦ x ≦ 0.940] as a main component, and the composition represented by xMgTiO _3. (1-x) CaTiO ₃ 10
Characterized that it contained added Nb ₂ O ₅ 1-6 parts by weight with respect to 0 parts by weight. If x is smaller than 0.925, τf takes a large positive value and Qu decreases. 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 baked at 1275 to 1400 ° C., Qu is 3980 to 4320 and τf is −3.69 to + 0.52p.
pm / ° C., ε _r is 19.05 to 21.51, and a high-quality product can be stably secured even when fired in a wide temperature range.

Incidentally, as the mixing ratio of CaTiO ₃ increases, τf changes from a negative value to a positive direction (FIG. 3),
_r tends to increase (FIG. 2), while Qu tends to decrease (FIG. 1). Further, as shown in FIG. 4 to 6, Nb ₂ O
By adding ₅ , Qu and εr do not change much, but τ _f tends to decrease. 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), by adding Nb ₂ O ₅ , it is possible to produce a sintered body having stable performance and high sintering density even when fired in a wide temperature range. Therefore, the addition amount of Nb ₂ O ₅ is particularly 1 to
When the content is 4% by weight (in particular, about 2% by weight), it is more excellent in terms of excellent performance balance and stable sinterability. As described above, in the above-mentioned appropriate mixing range of CaTiO ₃ and Nb ₂ O ₅ , the performances thereof are excellent and balanced, and the quality is stable.

[0008]

The present invention will be described below in detail with reference to examples. MgO powder (purity; 99.4%), C as CaO
aCO ₃ powder (purity; 99%), TiO ₂ powder (purity;
99.98%) and Nb ₂ O ₅ powder (purity: 100%) as starting materials, and as shown in Tables 1 to 3 and FIGS. 1 and 4, the composition formula xMgTiO _3. (1-x) CaTiO ₃ +
y weight% Nb ₂ O ₅ [xMgTiO _3. (1-x) Ca
100 parts by weight of TiO ₃ means y parts by weight of Nb ₂ O ₅ . A predetermined amount (about 500 g in total) was weighed and mixed so that each of x and y in the above formulas was changed. still,
Table 1 shows changes in the amount of MgTiO ₃ added, and Tables 2 and 3 show changes in the amount of Nb ₂ O ₅ added.
Then, after performing dry mixing (20 to 30 minutes) and primary pulverization with a mixer, the mixture was calcined at 1100 ° C. for 2 hours in an air atmosphere. Next, an appropriate amount of an organic binder (29 g) and water (300 to 400 g) were added to the calcined powder, and the mixture was mixed with a 20 mmφ alumina ball at 90 rpm, 2 rpm.
Milled for 3 hours. Then, freeze-dry (approximately 0.4 To
rr, 40-50 ° C., about 20 hours), and the obtained raw material was formed into a 19 mmφ × 11 mmt (thickness) cylindrical shape at a pressing pressure of 1000 kg / cm ² .

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

Next, this molded body is heated at 500 ° C.
Degreasing at time, then 1275-140 shown in each figure
Baking for 4 hours at each temperature in the range of 0 ° C., and finally polishing both end surfaces into a columnar shape 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, by the parallel conductive plate type dielectric cylindrical resonator method (TE ₀₁₁ MODE) or the like, the relative dielectric constant (hereinafter, simply referred epsilon _r.), Qu and .tau.f, further, by the Archimedes method sintered density It was measured. The resonance frequency is 6 GHz. The results are shown in Tables 1 to 3 and FIGS. Also, as an example,
FIG. 12 shows the result of X-ray diffraction in the case of 0.93 MgTiO ₃ .0.07 CaTiO ₃ (0.93 MgTiO ₃ .0.
2, 4 or 6% by weight of Nb _{2 with} respect to 07CaTiO ₃
Containing O ₅ and calcined at 1350 ° C. for 4 hours).

According to these results, xMgTiO _3.
(1-x) Qu value x is small CaTiO ₃ is tends to be low, the τf and epsilon _r conversely tends to increase on the plus side. The sintering density tends to increase as the firing temperature increases. However, when the amount of Nb ₂ O ₅ added increases, the sintering density does not change much even when the firing temperature is changed. Also, Nb
By addition of ₂ O ₅ , Qu and εr do not change much, but τ _f tends to decrease. Therefore, Nb ₂
The addition of O ₅ adds τ _f without degrading Qu and εr performance.
Suitable for adjustment. Further, when Nb ₂ O ₅ is not added, the characteristics cannot be measured when the firing temperature is low (1275 to 1325 ° C.) (Table 3), and 1350 to 1400 ° C.
, The properties can be measured, but τ _f is extremely large [Table 2 and FIG. 6; 19.7 (N
o. 1), 17.5 (No. 7), 15.1 ppm / ° C
(No. 13)], and the sintered density was 1375 ° C. or 135.
At the time of firing at 0 ° C., the size becomes small (No.
7 and No. 7 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. In particular, 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%.
° C and 1375 ° C, τf is -0.16 ~
+0.51 ppm / ° C., ε _r 21.48 to 21.5
1. Qu is 3980 to 4030, showing particularly excellent performance balance and extremely small variation in performance. Further, with respect to τf, since the rate of change with respect to the firing temperature is low, it is easy to adjust a small value around 0 ppm / ° C. On the other hand, when it contains no CaTiO _3, although Qu value is large, epsilon _r is small, and τf is -25-4
4ppm / ℃, which is significantly smaller on the minus side,
Not preferred.

Further, according to the analysis method based on the presence or absence of the X-ray diffraction peak shown in FIG.
It contains O ₃ (と) and CaTiO ₃ (●), and other peaks include MgTi ₂ O ₅ (△), and MgO, CaO,
This indicates that TiO ₂ is not contained. Also, Nb
_No peak of the ₂ O ₅ compound was detected. However, Nb
_{Although the} diffraction pattern is almost the same with respect to the added amount of ₂ O _{5, as the} added amount increases from 2% by weight to 6% by weight, M
The peaks of gTiO ₃ and MgTi ₂ O ₅ were slightly shifted to the lower angle side of 2θ (FIG. 12). Therefore, it is considered that the Nb ⁵⁺ ions were dissolved in MgTiO ₃ and MgTi ₂ O ₅ .

Further, although not shown, according to the results of electron micrographs, the particle diameter increases as the firing temperature increases (1275 ° C .; 2.6 μm, 1300 ° C .; 3.1 μm).
m, 1350 ° C; 4.9 µm, 1400 ° C; 6.1 µm
m, both measured by the Intercept method), indicating that the pores were reduced and densification was completed at 1350 ° C. All fracture surfaces showed intragranular fracture.

The present invention is not limited to the specific embodiments described above, but may be variously modified within the scope of the present invention according to the purpose and application. That is,
Various calcination conditions such as the calcination temperature and calcination conditions such as the calcination temperature can be selected. Also, the raw material to be CaO is the same as the above CaC.
In addition to O ₃ , peroxides, hydroxides, nitrates and the like can also be used. Similarly, other compounds that become oxides by heating can be used for other oxides.

[0018]

As it is evident from the foregoing description, the dielectric ceramic composition of the present invention, practical (high) the Qu and epsilon _r while maintaining the characteristic range, adjusting the mixing ratio of CaTiO ₃ and Nb ₂ O ₅ By doing so, it is possible to make τf close to zero or to control arbitrarily to desired values on the plus side and the minus side centering on zero, and to stably adjust τf to around zero. Further, by adding Nb ₂ O _5, a high-density and high-quality sintered body can be stably manufactured even if the firing temperature is varied in 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 the drawings]

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

In Figure 2 ceramic composition shown in FIG. 1 is a graph showing the relationship between x and epsilon _r.

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} )
₂ is a graph showing the relationship between the amount of Nb ₂ O ₅ and Qu in a [weight% Nb ₂ O ₅ ] porcelain composition.

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

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

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

FIG. 8 [0.93MgTiO ₃ .0.07CaTiO
₃ is a graph showing the relationship between sintering temperature and Qu in a 3+ (1-6) wt% Nb ₂ O ₅ ] porcelain composition.

In ceramic composition shown in FIG. 9 8 is a graph showing the relationship between firing temperature and epsilon _r.

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

11 is a graph showing a relationship between a sintering temperature and a sintering 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 the porcelain composition
It is a graph which shows a line diffraction result.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/42-35/49 CA (STN) REGISTRY (STN)

Claims (1)

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