JPH06199567A - Microwave dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a microwave dielectric porcelain compsn. capable of making the temp. coefft. of resonance frequency (tauf) close to zero or capable of arbitrarily and stably controlling it to a desired value on the plus or minus side of zero as a center while maintaining Qu (no-load Q) and epsilonr (relative dielectric constant) in a practical characteristic range each. CONSTITUTION:A compsn. represented by xMgTiO3.(1-x)CaTiO3 [where 0.93<=x<=0.95] is used as a base and Al2O3 is added to the base by 3-12 pts.wt. per 100 pts.wt. of the base to obtain the objective porcelain compsn. When the amt. of Al2O3 added is 3-9wt.% and firing temp. is 1,300-1,375 deg.C, 3,360-3,730 Qu (6GHz), 18.4-20.6 epsilonr, -2.2 to +2.6ppm/ deg.C tauf and 3.57-3.82g/cm<3> sintering density are attained.

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 by further adjusting the amount of Al ₂ O ₃ added, τf can be arbitrarily controlled to the plus side and the minus side centering on zero. 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 by adjusting the amount of Al ₂ O ₃ added, Qu
While maintaining the relative permittivity (hereinafter, simply referred to as ε _r ) within a practical characteristic range, τf is brought close to zero or is arbitrarily and stably set to a desired value on the plus side and the minus side centered on zero. It is an object to provide a dielectric porcelain composition that can be controlled.

[0005]

Means for Solving the Problems The present inventors have found that, in the dielectric ceramic composition, while maintaining high Qu and epsilon _r, tau
As a result of various studies on the composition capable of making f close to zero, the inventors have found that this can be achieved by adjusting the amount of Al ₂ O ₃ added, and completed the present invention. That is, the dielectric ceramic composition of the present invention is x
MgTiO ₃ · (1-x) CaTiO ₃ [however, 0.9
3 ≦ x ≦ 0.95] as a main component, and the above xMgTiO ₃ · (1-x) CaTiO ₃ 100
It is characterized in that 3 to 12 parts by weight of Al ₂ O ₃ is added and contained with respect to parts by weight. If x is smaller than 0.93, τf takes a large positive value, and Qu becomes small. Conversely, if it exceeds 0.95, τf takes a large negative value, which is not preferable.

As the amount of Al ₂ O ₃ added increases, Qu
Tends to increase (FIG. 1), and ε _r , τ f and the sintered density tend to decrease (FIGS. 2-4). In particular, the above Al
_When the addition amount of ₂ O ₃ is 3 to 9 wt% and the firing temperature is 1300 to 1375 ° C., Table 1 and FIGS.
, Qu is 3360 to 3730 and ε _r is 1.
8.4 to 20.6, τf is -2.2 to +2.6 ppm /
℃, the sintered density is 3.57 ~ 3.82g / cm ³ ,
Even if it is fired in a wide temperature range, a high quality product can be stably secured. In particular, τf has a very small variation (that is, it is concentrated in the range of −2 to +3 ppm / ° C.), and each shows a value near 0. From the above, Al ₂ O ₃
(3 to 9% by weight) and the appropriate temperature range (1
At 300 to 1375 ° C.), these properties are excellent and well-balanced, and stable quality is obtained.

[0007]

EXAMPLES The present invention will be specifically described below with reference to examples. MgO powder (purity; 99.4%), CaCO ₃ powder as a CaO component (purity; 99%), TiO ₂ powder (purity; 99.98%), Al ₂ O ₃ powder (purity; 9)
9.9%) as the starting material, as shown in Tables 1 and 2, the composition formula xMgTiO _3. (1-x) CaTiO ₃ +
y wt% Al ₂ O ₃ [xMgTiO ₃ · (1-x) Ca
It means Al ₂ O ₃ 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 CaTiO ₃ (1-x) added (constituent amount), and Table 2 shows the amount of Al ₂ O ₃ added.

[0008]

[Table 1]

[0009]

[Table 2]

Then, dry mixing (20
˜30 minutes) and primary pulverization, and then calcination for 2 hours at a temperature of 1100 ° C. in an air atmosphere. Next, an appropriate amount of organic binder (29 g) and water (300-
400 g), and with an alumina ball of 20 mmφ,
It was crushed at 0 rpm for 23 hours. Then, it is granulated by vacuum freeze-drying (about 0.4 Torr, 40 to 50 ° C., about 20 hours), and 1 ton / cm ² is used by using this granulated raw material.
It was molded into a cylindrical shape of 19 mmφ × 11 mmt (thickness) by the pressing pressure of.

Next, the molded body was placed in the atmosphere at 500 ° C. for 3 days.
After degreasing for a period of time, after that, it is baked at a predetermined temperature in the range of 1250 to 1425 ° C. for 4 hours, and finally both end surfaces are about 16 m
Dielectric samples (Nos. 1 to 12 in Table 1 and Nos. 1 to 24 in Table 2) were polished into a cylindrical shape of mφ × 8 mmt (thickness).
And Then, for each sample, Qu, ε _{r was} measured by a parallel conductor plate type dielectric cylinder resonator method (TE ₀₁₁ MODE) or the like.
And τf, and the sintered density was measured by the Archimedes method. This τ _f is measured in the temperature range of 20 ° C. to 80 ° C., and τ _f = [(f (80 ° C.) − F (20 ° C.)] / [F (20
C) × ΔT]. This ΔT is 80 ° C-20 ° C =
It is 60 ° C. These results are shown in Table 1, Table 2 and FIGS.
Shown in. The resonance frequency used for the Qu measurement is 5.7 to
It is 6.3 GHz. The Qu value in Tables 1 and 2 is 6G.
It is a value converted to Hz. 9 shows the relationship between the added amount of Al ₂ O ₃ and the average particle size of the sintered body, and FIG. 10 shows the relationship between the firing temperature and the average particle size of the sintered body. Furthermore, as an example, 0.
FIG. 13 (13) shows the results of X-ray diffraction in the case of 94MgTiO ₃ .0.06CaTiO ₃ .3 to 12 wt% Al ₂ O ₃ .
Calcination at 50 ° C. for 4 hours).

According to these results, xMgTiO ₃ ·
If (1-x) of (1-x) CaTiO ₃ is large, 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. Qu tends to increase as the amount of Al ₂ O ₃ added increases, and ε _r , τ
f and the sintered density tend to decrease. When the firing temperature is 1275 ° C., Qu, ε _r, and sintered density tend to be small, and the variation is large, but 1
At 300 to 1375 ° C, very stable performance is exhibited. Further, in the case where the added amount of Al ₂ O ₃ is 3 to 9 wt% and the firing temperature is 1300 to 1375 ° C., as described above, Qu
Is 3360-3730, ε _r is 18.4-20.6, τ
f is -2.2 to +2.6 ppm / ° C, and the sintered density is 3.5.
It was 68 to 3.816 g / cm ³ , showing very well balanced performance and physical properties. From the above, proper addition of Al ₂ O ₃ improves Qu performance while maintaining ε _r, and is suitable for adjusting τ f. Especially, regarding τf, A
Since the rate of change with respect to the amount of l ₂ O ₃ added and the firing temperature is low, it is easy to adjust a small value near 0 ppm / ° C.

Further, as shown in FIG. 10, the grain size of the crystal grains in the sintered body increased as the firing temperature increased (1300 ° C .; 1.61 μm, 1350 ° C .; 2.19 μ
m, 1400 ° C .; 4.46 μm, both measured by Intercept method), on the other hand, as shown in FIG. 9, the particle size decreased with increasing Al ₂ O ₃ addition amount (3% by weight; 3.97). , 6% by weight; 3.76, 12% by weight;
19). Further, FIG. 12 is a diagram illustrating a crystal structure by black-and-white copying an electron micrograph (1000 times) of a composition (1350 ° C., calcined for 4 hours) to which 6 wt% Al ₂ O ₃ was added in FIG. An electron micrograph of a composition (1350 ° C., baked for 4 hours) to which 12% by weight of Al ₂ O ₃ was added (100
(0 times) is shown in black and white to explain the crystal structure.
According to these figures, all show a substantially uniform particle size distribution. The fracture surface structure is 3 to 12% by weight of Al.
All of the systems containing ₂ O ₃ showed intragranular fracture.

Further, according to the analysis method based on the presence / absence of X-ray diffraction peaks shown in FIG. 13, the structure of the product of the present invention is MgTi.
It contains O ₃ (◯) and CaTiO ₃ (), and the other peak is MgTi ₂ O ₅ (Δ), indicating that it does not contain the reaction product with Al ₂ O ₃ .

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.

[0016]

INDUSTRIAL APPLICABILITY As described above, the dielectric porcelain composition of the present invention maintains the Qu and ε _r in a practical (high) characteristic range while controlling the addition amount of Al ₂ O ₃ . ,
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.

[Brief description of drawings]

FIG. 1 is manufactured by firing at various firing temperatures [0.
94MgTiO ₃ · 0.06CaTiO ₃ + (0-1
2) Al ₂ O ₃ wt%] In the porcelain composition, Al ₂ O
It is a graph which shows the relationship between ₃ quantity and Qu.

2] In the porcelain composition shown in FIG.
₃ is a graph showing the relationship between the weight% Al ₂ O ₃ amount and ε _r .

3] In the porcelain composition shown in FIG.
₃ is a graph showing the relationship between (wt%) Al ₂ O ₃ amount and τf.

4] In the porcelain composition shown in FIG.
₃ is a graph showing the relationship between the amount of (% by weight) Al ₂ O ₃ and the sintered density.

FIG. 5 [0.94MgTiO ₃ .0.06CaTiO _3
3 + (3 to 12) wt% Al ₂ O ₃ ] A ceramic composition showing a relationship between firing temperature and Qu.

FIG. 6 is a graph showing the relationship between the firing temperature and ε _r in the porcelain composition shown in FIG.

FIG. 7 is a graph showing the relationship between firing temperature and τf in the porcelain composition shown in FIG.

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

FIG. 9: manufactured by firing at 1350 ° C. [0.94
_{MgTiO 3 · 0.06CaTiO 3 + (3~12} ) A
In l ₂ O ₃ wt%] porcelain composition is a graph showing the relationship between the average particle size of the Al ₂ O ₃ amount and the sintered body.

FIG. 10 [0.94MgTiO ₃ .0.06CaTi
In O ₃ +12 wt% Al ₂ O _3] ceramic composition is a graph showing the relationship between the average particle diameter of the sintering temperature and the sintered body.

FIG. 11 [0.94MgTiO ₃ .0.06CaTi
O ₃ +6 wt% Al ₂ O _3] an electron micrograph showing the structure of the crystal of the ceramic composition (1000 times).

FIG. 12 [0.94MgTiO ₃ .0.06CaTi
O ₃ is a +12 wt% Al ₂ O _3] an electron micrograph showing the structure of the crystals of the ceramic composition (1000 times).

FIG. 13 [0.94MgTiO ₃ · 0.06CaTi
[Fig. ₃ ] Fig. 3 is a graph showing the X-ray diffraction results of O ₃ +3, _6, 9 or 12 wt% Al ₂ O ₃ ] porcelain composition.

Claims (1)

[Claims] 1. xMgTiO _3. (1-x) CaTiO
₃ [however, 0.93 ≤ x ≤ 0.95] as the main component, and the above xMgTiO ₃ · (1-x) C
₃ to 12 parts by weight of Al based on 100 parts by weight of aTiO _3.
A microwave dielectric ceramic composition containing ₂ O ₃ as an additive.