JPH04265269A - Dielectric ceramic for microwave - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic for the microwave having high dielectric constant (epsilonr) and non-load Q (Qu) and with the temp. coefficient (tauf) of the resonance frequency capable of being optionally changed with 0 as the median by changing the composition of the ceramic. CONSTITUTION:When the composition of the main component is expressed by XBaO.YTiO2.Z{(Sm2O3)1-w1-w2(La2O3)w1(Nd2O3)w2}.VBi2O3 (where X, Y, Z and V are mol%), 11.5<=X<=21.0, 60.0<=Y<=76.0, 6.5<=Z<=26.0, 0<V<=10.0 and X+Y+Z+V=100, and 0<W1<1.0, 0<W2<1.0 and 0<1-W1-W2<1.0 (where W1 and W2 are molar ratios), this ceramic contains <=5wt.% (not 0%) of lead oxide (PbO) and <=5wt.% (not 0%) of cerium oxide (CeO) based on the main component.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to dielectric ceramics for microwave use, and in particular, to
and dielectric ceramics for microwaves which have a large no-load Q (Qu) and whose temperature coefficient (τf) of the resonant frequency can be changed to any value around 0 by changing the composition of the ceramic. It is something.

0002

[Prior Art] Dielectric ceramics used as constituent materials for dielectric resonators for microwave bands, temperature compensation capacitors, etc. have a relative dielectric constant (εr) and an unloaded Q (Qu
) is required, and by changing the composition, the temperature coefficient (τf) of the resonant frequency can be set to any positive or negative value centered around 0.

Conventionally, as such dielectric ceramics, for example, Japanese Patent Publication No. 61-146 filed by the applicant of this application,
No. 06 discloses a (BaO)(TiO2)X-based composition consisting of Sm2O3 and La2O3.

0004

[Problems to be Solved by the Invention] However, among the above-mentioned conventional microwave dielectric ceramics, those exhibiting a temperature coefficient of around 0 (ppm/°C) (including 0; the same shall apply hereinafter) are , the relative permittivity (εr) is at most 80
This was insufficient for miniaturizing dielectric resonators.

[0005] The present invention was made in view of the above points, and therefore, an object of the present invention is to improve the temperature coefficient (τf).
It is an object of the present invention to provide dielectric ceramics for microwaves which exhibit larger relative permittivity (εr) and no-load Q (Qu) than conventional ones even when the composition is such that εr is around 0 (ppm/°C).

[0006]

[Means for Solving the Problems] In order to achieve this object, the microwave dielectric ceramics of the present invention include barium oxide (BaO), titanium dioxide (TiO2),
Samarium oxide (Sm2O3), lanthanum oxide (La2
O3), neodymium oxide (Nd2O3) and bismuth oxide (Bi2O3) as the main component represented by the following formula (1), and 5% by weight or less (however,
It is characterized by containing lead oxide (PbO) of 5% by weight or less (excluding 0%) and cerium oxide (CeO2) of 5% by weight or less (excluding 0%).

[0007]

[Formula 2]

[0008]

(However, in formula (1), X, Y, Z, and V are expressed in mol%, and 11.5≦X≦21.0 60.0≦Y≦76.0 6.5≦Z≦ 26.0 0<V≦10.0 X+Y+Z+V=100 Within the range of <1.0).

0010

[Operation] According to the dielectric ceramic for microwave use of the present invention, as is clear from the experimental results described later, the temperature coefficient (τf) is centered around 0 (ppm/°C) by changing the composition of the ceramic. change to positive or negative. However, with the composition claimed in this invention, both the dielectric constant (εr) and the unloaded Q (QU) of the dielectric ceramic have larger values than those of the dielectric ceramic with a composition outside the scope of the invention. show.

[0011]

[Embodiments] Examples of the present invention will be described below.

First, microwave dielectric ceramics of Examples and Comparative Examples were manufactured as described below.

Starting materials include chemically high-purity barium carbonate (BaCO3), titanium dioxide (TiO2), samarium oxide (Sm2O3), and lanthanum oxide (La2O3).
, neodymium oxide (Nd2O3), bismuth oxide (B
i2O3), lead oxide (PbO) and cerium oxide (Ce
O2) were used, respectively. In order to produce a large number of experimental dielectric ceramics having different compositions, these starting materials were each accurately weighed so that the composition ratios were as listed in Tables 1 to 3 below.

The weighed raw materials were mixed with pure water in a pot mill, dehydrated and dried, and then calcined in an air atmosphere at a temperature of 1050° C. for 2 hours.

Next, this calcined product was wet-pulverized with pure water in a pot mill, and then dehydrated and dried.

Next, a binder was added to the pulverized and dried product to granulate it, and then the granulated powder was sized through a 32-mesh sieve to obtain granulated powder.

[0017] This granulated powder was molded into a diameter of 16 mm using a mold and a hydraulic press at a molding pressure of 1 to 3 ton/cm2.
It was molded into a disk shape with a thickness of 9 mm.

The molded body thus obtained was placed in a high-purity alumina box and then fired in air at a temperature of 1250 to 1450°C for 2 hours to obtain a dielectric ceramic.

Next, the characteristics of each of the experimental dielectric ceramics produced as described above were measured as described below.

Relative permittivity (εr
) and unloaded Q (Qu) are Hakki-Coleman (Ha
It was measured by the Kki-Coleman) method. In addition, the temperature coefficient (τf) of the resonant frequency is, as is conventionally known,
Based on the resonant frequency f(20) at 20°C, −
Resonant frequencies f(-40) and f(85) at temperatures of 40°C and +85°C and temperature difference ΔT (in this case 8
5-(-40)=125) according to the following equation (2). Note that the resonant frequency in these measurements is 3 to 4.
It was GHz.

τf={f(85)−f(−40)}/f(2
0) ΔT...(2) Relative permittivity (εr), no-load Q (Qu), and temperature coefficient (τf) of each dielectric ceramic
are shown in Tables 1 to 3, respectively. In addition, in these tables, samples with sample numbers marked with * indicate comparative examples outside the scope of the present invention, and samples with other sample numbers are examples within the scope of the present invention. In addition, "RE" in the table
is a rare earth oxide ({(Sm2O3)1-W in formula (1)
1-W2(La2O3)W1(Nd2O3)W2} portion) is omitted.

[0022]

[Table 1]

[0023]

[0024]

[Table 2]

[0025]

[0026]

[Table 3]

[0027]

Next, the results of the experiment conducted as described above will be discussed.

When the amount of CeO2 added to the main component is within 5% by weight, the relative permittivity (εr) increases as the amount of PbO added increases up to 5% by weight; It can be seen that when the amount exceeds 5% by weight, the value decreases rapidly. Furthermore, it was found that when the amount of CeO2 added to the main component is within 5% by weight, the unloaded Q (Qu) decreases as the amount of PbO added increases, and decreases rapidly when the amount of PbO added exceeds 5% by weight. Ru. Furthermore, when the amount of CeO2 added to the main component is within 5% by weight, the temperature coefficient (τf) is
It can be seen that after the addition amount of PbO shows a minimum value at 3% by weight, it increases as the addition amount of PbO increases, and increases rapidly when the addition amount of PbO exceeds 5% by weight. Specifically, sample No.
6, 11, and 26 have a smaller relative dielectric constant (εr) than others, a small no-load Q (Qu) of 1000 or less, and a positive temperature coefficient (τf), so they are suitable as dielectric ceramics for microwaves. It turns out that it is inappropriate as such.

On the other hand, when the amount of PbO added to the main component is within 5% by weight, the relative permittivity (εr) slightly decreases with increasing amount of CeO2 additive up to 5% by weight. It can be seen that when the amount added exceeds 5% by weight, the value decreases rapidly to 40 or less. In addition, Pb for the main component
When the amount of O added is within 5% by weight, the unloaded Q (Qu)
It can be seen that the maximum value is reached when the amount of CeO2 added is 3% by weight, and becomes smaller when the amount of CeO2 added is 3% by weight. Also, P for the main component
If the amount of bO added is within 5% by weight, the temperature coefficient (τf)
shows the minimum value when the amount of CeO2 added is 3% by weight, and then
It can be seen that when the amount of CeO2 added exceeds 5 weight, there is a sharp positive increase.

As explained in detail above, from a practical point of view, the composition of the main components is XBaO・YTiO2・Z{(Sm2
O3)1-W1-W2(La2O3)W1(Nd2O3
)W2}・VBi2O3, X, Y, Z,
V is expressed in mol%, 11.5≦X≦21.0, 60.
0≦Y≦76.0, 6.5≦Z≦26.0, 0<V≦1
0.0 and X+Y+Z+V=100, W
1, W2 is expressed as a molar ratio, 0<W1<1.0, 0<W
The main component is within the range of 2<1.0 and 0<1-W1-W2<1.0, and 5% by weight or less (however, 0
% is excluded. ) and 5% by weight or less (excluding 0%) of cerium oxide were found to be suitable as the microwave dielectric ceramic of the present invention.

[0032] The conditions for manufacturing dielectric ceramics in the above-mentioned embodiments have been explained under specific preferred conditions within the scope of the present invention. However, this is merely an example, and it is clear that the invention is not limited to this embodiment.

[0033]

Effects of the Invention As is clear from the above explanation, the microwave dielectric ceramic of the present invention has a high relative dielectric constant (εr) and an unloaded Q (QU) in the microwave region.
are both larger than the conventional ones, and furthermore, by changing the composition, the temperature coefficient (τf) can be easily changed to any positive or negative value centered around 0 (ppm/° C.). Therefore, it can be used as a constituent material for dielectric resonators in the microwave band or temperature compensation capacitors, and has great industrial utility value.

Claims (1)

[Claims] [Claim 1] Barium oxide (BaO), titanium dioxide (TiO2), samarium oxide (Sm2O3), lanthanum oxide (La2O3), neodymium oxide (Nd2O)
3) and bismuth oxide (Bi2O3), the main component is represented by the following formula (1), and the main component is 5
Lead oxide (PbO) up to 5% by weight (excluding 0%) and cerium oxide (excluding 0%) up to 5% by weight (excluding 0%)
A microwave dielectric ceramic characterized by comprising: [Formula 1] (However, in formula (1), X, Y, Z, and V are shown in mol%, 11.5≦X≦21.0 60.0≦Y≦76.0 6.5≦Z ≦26.0 0<V≦10.0 X+Y+Z+V=100 Within the range of (W2<1.0).