JPH05182522A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To improve the no-load Q value of a composition expressed by means of a composition formula xPbO-y (Mg1/3Nb2/3)O2-z/CaO by substituting TiO2 partly for the (Mg1/3Nb2/3)O2 of magnesium lead calcium niobate. CONSTITUTION:A dielectric porcelain composition, containing lead oxide, calcium oxide, titanium oxide, magnesium oxide, and niobium oxide, is expressed by a composition formula (Pb1-xCax) (Mg1/3Nb2/3)1-yTiyO3. (X) and (Y) are set so as to stay within the area of a quadrangle taking points A, B, C, and D as vertices in a xy plane (where, the points on a line AB, where y=0, are excluded). That is, it is possible to obtain a high dielectric constant, excellent temperature characteristic, and a high Q value in a microwave area by substituting TiO2 partly for the (Mg1/3Nb2/3)O2 of magnesium lead calcium niobate (PbCa) (Mg1/3Nb2/3)O3. It is also possible to obtain change due to temperature of small resonance frequency in xPbO-y (Mg1/3Nb2/3)O2-zCaO system at a high relative dielectric constant, and to improve a non-load Q value thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic used in the microwave region.

[0002]

2. Description of the Related Art In recent years, there has been a demand for downsizing of equipment with the progress of communication using electromagnetic waves in the microwave range, such as car telephones, portable telephones, and satellite broadcasting.
For this purpose, it is necessary to reduce the size of individual parts that make up the device. In these devices, the dielectric is incorporated as a dielectric resonator in a filter element or an oscillating element. When the same resonance mode is used, the size of the dielectric resonator is inversely proportional to the square root of the dielectric constant of the dielectric material. Therefore, in order to manufacture a small dielectric resonator, a material having a high dielectric constant is used. is necessary. Another characteristic required for the dielectric is that it has a low loss in the microwave region, that is, it has a high no-load Q value, that the temperature change of the resonance frequency is small, that is, that the temperature change of the dielectric constant is small. Is.

Conventionally, as the dielectrics used in this field, Ba (Zn _1/3 Ta _2/3 ) O ₃ and BaO--TiO ₂ system compositions and compositions in which a part thereof is replaced with other elements are used. Was known. These have a relative dielectric constant of about 30 to 40,
The relative permittivity is too low to miniaturize the resonator. As a large material more dielectric _{constant, BaO-TiO 2 -Sm 2 O} 3 system is disclosed in JP-A-57-15309. This system has a relative dielectric constant of about 80, a high unloaded Q value of about 3000 at 2 to 4 GHz, and a small temperature coefficient of relative dielectric constant.

In order to further miniaturize the resonator, a material having a higher relative dielectric constant is required, but a material having a high unloaded Q value and a small temperature coefficient has not been known.
It is different ceramic composition and ceramic composition described above, in _{xPbO-y (Mg 1/3 Nb 2/3} ) O 2 -zCaO a composition system expressed, as high as 40 to 100 ratio A porcelain composition having a dielectric constant and excellent temperature characteristics has been found, and an application has already been made (see the specification of Japanese Patent Application No. 2-176007).

[0005]

However, in the above-mentioned composition system in which the relative dielectric constant is 50 or more, the unloaded Q value is 2000 or less, and the above-mentioned BaO-Sm ₂ O _3-
Low compared to TiO ₂ etc. Since the no-load Q value decreases in inverse proportion to the frequency, the frequency to be used is limited to a relatively low frequency, and there is a problem that it cannot be used in applications requiring a high no-load Q.

In consideration of the above-mentioned conventional problems, the present invention takes the above composition formula xPbO-y (Mg _1/3 Nb _2/3 ) O ₂ -zC.
The object is to improve the unloaded Q value of the dielectric ceramic composition represented by aO.

[0007]

[Means for Solving the Problems] A dielectric ceramic composition containing lead oxide, calcium oxide, titanium oxide, magnesium oxide, and niobium oxide has a composition formula (Pb _1-x Ca _x ) (Mg
_1/3 Nb _2/3 ) _1-y Ti _y O ₃ , x and y are x
It is a dielectric porcelain composition located in a rectangular region having the following points A, B, C, and D as vertices on the y-plane (except on the AB line where y = 0).

A; x = 0.4 y = 0 B; x = 0.75 y = 0 C; x = 0.85 y = 0.4 D; x = 0.65 y = 0.4

[0009]

[Function] Magnesium lead niobate calcium, (PbCa)
(Mg _1/3 Nb _2/3 ) O ₃ , part of (Mg _1/3 Nb _2/3 ) O ₂ is TiO ₂
By substituting with, a high dielectric constant and excellent temperature characteristics and a high Q value in the microwave region can be realized.

[0010]

EXAMPLES Examples of the present invention will be described below.

First, the purity of MgO, Nb ₂ O ₅ , TiO ₂ , PbO and CaCO ₃ , which are chemically high purity, was adjusted as a starting material, and then a predetermined amount was weighed according to the blending amount shown in Table 1. To do. FIG. 1 shows x and y ranges of the composition of Table 1 as x.
It is the figure represented by the y plane. These powders are put into a polyethylene ball mill, stabilized zirconia boulders and pure water are added and mixed for 17 hours. After mixing, the slurry is dried, put in an alumina crucible, and calcined at 750 to 850 ° C. for 2 hours. The calcined body is crushed by a raikai machine, then crushed by the above-mentioned ball mill for 17 hours and dried to obtain a raw material powder. To this powder, 6% by weight of a 5% aqueous solution of polyvinyl alcohol was added as a binder, mixed, and then granulated through a 32 mesh sieve to obtain a diameter of 13 m at 100 MPa.
m and a columnar shape with a thickness of about 5 mm. The molded body is heated at 600 ° C for 2 hours to incinerate the binder, then put in a magnesia container, and a calcined powder of the same composition is placed around it to form Pb.
1250-135 depending on the composition while preventing the evaporation of O
Hold at 0 ° C. for 2 hours and bake.

The resonance frequency and the unloaded Q value of the sintered body obtained as described above were obtained by measurement by the dielectric resonator method. Further, the relative permittivity was calculated from the dimensions of the sintered body and the resonance frequency. The resonance frequency was 2 to 5 GHz. Also, measure the resonance frequency at -25 ° C and 85 ° C,
The temperature change rate (τ _f ) was calculated based on the value of 20 ° C. The results are shown in Table 1.

[0013]

[Table 1]

[0014] As is clear from Table 1, the compositions within the scope of the _{claims, xPbO-y (Mg 1/3 Nb} 2/3) O 2 -
It has a relative dielectric constant equivalent to that of zCaO and has a higher unloaded Q value than the composition without substitution, that is, the composition of y = 0. The absolute value of the change in resonance frequency with temperature is 60 ppm / ° C. or less. In particular, sample numbers 9, 10, and 12 have a relative dielectric constant of about 60, and the absolute value of the temperature change of the resonance frequency is 20 ppm / ° C. or less, and 2
It showed excellent characteristics with an unloaded Q value of 000 or more. Therefore, the limitation of applications and frequencies due to the low unloaded Q value is alleviated. Further, the dielectric ceramic of the present invention can be used not only as a dielectric resonator but also as a microwave circuit board or the like. However, in the composition in which x and y are not included in the quadrangle ABCD, the relative dielectric constant is 40 or less, or the temperature change of the resonance frequency exceeds 60 ppm / ° C., which is not desirable as a microwave dielectric. Excluded from the claims.

The term "within a quadrangle region having vertices at points A, B, C and D in the xy plane" as used in the claims means:
It also includes the line connecting these vertices.

[0016]

As is apparent from the above description, the book
The invention is (Pb_1-xCa_x) (Mg_1/3Nb_2/3) _1-yTi_yO₃Represented by
Since it is a dielectric porcelain composition that is used, xPbO-y (Mg_1/3
Nb_2/3) O₂-Temperature change of small resonance frequency of zCaO system
And a high relative dielectric constant are obtained, and the unloaded Q value is improved.
It

[Brief description of drawings]

FIG. 1 is a composition diagram showing a range of a dielectric ceramic composition of the present invention, and a hatched portion is a claim. The sample numbers shown in the figure correspond to the sample numbers in Table 1.

Claims (1)

[Claims] 1. A dielectric ceramic composition containing lead oxide, calcium oxide, titanium oxide, magnesium oxide, and niobium oxide having a composition formula (Pb _1-x Ca _x ) (Mg _1/3 Nb _2/3 ) _{1 -y} Ti _y
When represented by O ₃ , x and y must be within the rectangular area having the following points A, B, C, and D on the xy plane (except on the AB line where y = 0). A dielectric porcelain composition characterized by: A; x = 0.4 y = 0 B; x = 0.75 y = 0 C; x = 0.85 y = 0.4 D; x = 0.65 y = 0.4