JPH04265271A - Microwave dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a microwave dielectric porcelain compsn. having such a practical temp. coefft. as -1 to +12ppm/ deg.C and superior performance balance and maintaining high Q and a high relative dielectric constant. CONSTITUTION:BaO.4TiO2 (BaTi4O9) is used as a base and SnO2 is incorporated into the base by >0-5wt.% to obtain a microwave dielectric porcelain compsn.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to microwave dielectric ceramic compositions, and more specifically, the present invention relates to microwave dielectric ceramic compositions, and more specifically, the present invention relates to microwave dielectric ceramic compositions that are particularly suitable for ensuring well-balanced performance in Q value, dielectric constant, and temperature coefficient of resonance frequency. The present invention relates to a microwave dielectric ceramic composition having a temperature coefficient. The present invention is utilized in the microwave region for impedance matching of dielectric resonators, microwave integrated circuit boards, various microwave circuits, and the like.

0002

[Prior Art] Conventional microwave dielectric ceramic compositions include ZrO2-SnO2-TiO2 ceramic compositions, BaO-TiO2 ceramic compositions, and ceramic compositions in which a part of them is replaced with other elements (especially Publication No. 1-37807) and the like are known.

0003

[Problems to be Solved by the Invention] However, conventional ceramic compositions have problems such as a small dielectric constant or Q value, or an inability to obtain a desired temperature coefficient. In particular, there is a need for new microwave dielectric ceramic compositions having different compositions that have excellent relative dielectric constant, Q value, and temperature coefficient performance. In particular, BaO・4TiO2
A dielectric ceramic having a composition of (BaTi4O9) is known as a dielectric for microwaves. However, although this porcelain exhibits a high dielectric constant εr of about 38 and a high no-load Q value of about 3000, the temperature coefficient τf of the resonance frequency is large at about +50 ppm/°C, so it is designed as a microwave resonator. In this case, it was not possible to obtain a product with stable performance over temperature. For this reason, the above τf
It was desired that the value be close to 0. The present invention has been made in view of the above points, and exhibits a practical temperature coefficient (close to 0) while maintaining a high Q value and dielectric constant,
The purpose of the present invention is to provide a microwave dielectric ceramic composition (hereinafter simply referred to as a dielectric ceramic composition) having an excellent performance balance.

0004

[Means for Solving the Problems] The present inventor has discovered that BaO.4
A predetermined amount of SnO is added to TiO2 (BaTi4 O9).
By incorporating 2, they succeeded in making τf as close to 0 as possible, and completed the present invention. That is, the dielectric ceramic composition of the present invention contains BaO.
It is characterized by having 4TiO2 (BaTi4O9) as its main component, and containing 15% by weight or less of SnO2 (however, not including 0). The reason for containing SnO2 is BaO・4TiO2 (B
This is because although aTi4O9) exhibits a large τf on the positive side, the addition of SnO2 can shift this τf to the negative side. If the amount added exceeds 15% by weight, the other properties such as the no-load Q value and relative dielectric constant will drop significantly, making it impossible to put it into practical use. This porcelain composition is made by mixing a predetermined amount of predetermined raw materials,
Manufactured by sintering. For example, raw material powder that becomes BaO after sintering, TiO2 powder, and SnO2 powder are mixed and calcined in amounts corresponding to the above composition formula, and this is crushed to produce calcined powder, and this calcined powder is used to produce calcined powder. It can be manufactured by molding and firing.

[0005]

[Examples] The present invention will be explained in detail with reference to Examples below. (1) Preparation of each sample BaCO3 powder with a purity of 99.9%, TiO2 powder with a purity of 99.9%, and SnO2 powder with a purity of 99.8% are used.
(BaTi4 O9), and Table 1
and 5, 10, 15% by weight as shown in Table 2 (the Ba
A predetermined amount (approximately 650 g in total) was weighed out and mixed so as to have a composition in which SnO2 was added to O.4TiO2, and primary pulverization and mixing were performed using an Eirich mixer in a dry manner. Thereafter, it was calcined in the air at a temperature of 1100° C. for 2 hours. Next, an appropriate amount of organic binder (approximately 29 g of polyvinyl alcohol) and ion exchange water (approximately 300 g of polyvinyl alcohol) are added to this calcined powder.
~500g) was added, secondary pulverized with 20mmφ alumina balls, and granulated by spray drying.
It was molded into a cylindrical shape of x10 mmt (thickness). Next, this molded body was placed in the atmosphere at 1250°C (sample Nos. 1 to 3),
275°C (Sample No. 4 to 6), 1300°C (Sample No.
．． 7-9), 1325°C (Sample No. 10-12), 1
The dielectric material was baked at 350°C (sample Nos. 13 to 15) and 1375°C (sample Nos. 16 to 18) for 4 hours, and finally polished into a cylindrical shape of 16 mmφ x 8 mmt (thickness). Body samples (No. 1 to 18) were used. And Qu
The value and relative dielectric constant εr were measured in TE011 mode using a parallel conductor plate type dielectric resonator method. The temperature coefficient τf of the resonance frequency was measured in the range of -30 to 80°C. The resonant frequency is approximately 4.5 GHz.

(2) Performance evaluation The characteristics of each dielectric sample described above were investigated, and the results are shown in Table 1 (firing temperature: 1250, 1275, 1300°C) and Table 2 (
Firing temperature: 1325, 1350, 1375°C).

[Table 1]

[Table 2] According to these results, the Qu value decreases as the amount of SnO2 added increases. And, the lower the firing temperature, the lower the Qu
Values tend to be high. εr decreases slightly as the amount of SnO2 added increases, and the higher the firing temperature, the higher εr tends to be, but in all cases it shows a high value of 29 or more. Further, τf goes from a positive value to a negative value as the amount of SnO2 added increases. In particular, as the firing temperature increases, the decrease in τf in the negative direction becomes more significant. For example, when the firing temperature is 1375°C, Sn
When the amount of O2 added was 15% by weight (No. 18), -0
．． It becomes 96 ppm/°C. In particular, this case is useful in fields of application where the focus is on the low τf rather than the high Qu value. Further, the sintered density does not change much when the firing temperature exceeds 1325°C, but when the firing temperature exceeds 1275°C, the density becomes high at 4.3 g/cm 3 or more.

Furthermore, in order to investigate the crystal structure of the sintered body, the above-mentioned Test No. 16 (firing temperature; 1375°C, SnO2
Addition amount: 5% by weight) and No. 18 (firing temperature; 137
5°C, SnO2 addition amount: 15% by weight) and No. 9 (Firing temperature: 1300°C, SnO2 addition amount: 15% by weight)
X-ray diffraction was performed on the sintered body, and the results are shown in FIGS. 1, 2, and 3, respectively. In addition, the ● mark in the table indicates BaTi4O
9, ○ mark is Ba2 Ti9 O20, △ mark is Ba2
Ti5O12 and Sn indicate peaks assigned to SnO2. According to the results shown in FIGS. 1 and 2, as the amount of SnO2 added increased, BaTi4 O9 decreased and Ba2 Ti9 O20 increased instead. This is SnO2
This corresponds to the fact that the Qu value decreases and goes from positive to negative as . Also, Figures 1 and 3
As shown in Figure 2, when comparing the firing temperatures with the same amount of SnO2 added (15% by weight), at 1300°C, BaTi
4O9 is the central composition, and at 1375℃ Ba2
Ti9O20 was the main composition. This is 1375
This corresponds to the result that the Qu value becomes higher in the positive direction when fired at 1300°C than when fired at 1300°C. From the above, BaTi
4 In the O9 +SnO2 system, the Qu value and τf
The behavior of BaTi4 O9 and Ba2 Ti9 O2
This is thought to be influenced by the amount of 0 produced. Therefore,
By changing the composition ratio of BaTi4O9 and Ba2Ti9O20, it is possible to provide various Qu values or τf depending on the purpose and use. From the above, if you want to increase the dielectric constant, Qu value, and sintered density, and also make the temperature coefficient τf as close to 0 as possible,
The amount of SnO2 added and the firing temperature can be appropriately selected according to each set value. That is, when the amount of SnO2 added is 5 to 15% by weight, τf is approximately -1 to +12 ppm.
/°C. Further, when the following characteristics are satisfied, the amount of SnO2 added can be set to 15% by weight or less, and the firing temperature can be set to 1250 to 1350°C. Specific dielectric constant εr; 28 to 36 Qu value; 1200 to 2600 (for 4.5 GHz) Temperature coefficient τf;
It can be fired at a temperature of 5°C to 1350°C, and in this case, the balance of all performances is very good. It should be noted that the present invention is not limited to what is shown in the above-mentioned specific examples;
Various modifications may be made within the scope of the present invention depending on the application. That is, the calcination conditions such as the calcination temperature, the calcination conditions such as the calcination temperature, etc. can be variously selected. Also, BaO
In addition to the above-mentioned BaCO3, peroxides, hydroxides, nitrates, etc. can also be used as raw materials.

[0008]

As described above, the dielectric ceramic composition of the present invention has a Qu value, a relative dielectric constant εr, and a temperature coefficient τf of the resonant frequency that are all within a practical range, and its performance is well balanced. In particular, the temperature coefficient is close to 0, and when designed as a microwave resonator, it exhibits stable performance with respect to temperature.

[Brief explanation of the drawing]

FIG. 1: Sample No. manufactured in Examples. It is an explanatory view showing the result of X-ray diffraction of the sintered compact of No. 16.

FIG. 2: Sample No. manufactured in the example. It is an explanatory view showing the result of X-ray diffraction of the sintered compact of No. 18.

FIG. 3: Sample No. manufactured in the example. 9 is an explanatory diagram showing the results of X-ray diffraction of the sintered body No. 9. FIG.

Claims (1)

[Claims] [Claim 1] BaO・4TiO2 (BaTi4
1. A microwave dielectric ceramic composition comprising SnO2 as a main component and 15% by weight or less (excluding 0) of SnO2.