JPH052918A - Porcelain compound for dielectric substance - Google Patents

Abstract

PURPOSE:To enhance the dielectric constant by specifying the mol ratio of Pb, Ca, Sr in a compound as expressed by a specific composition formula. CONSTITUTION:A compound as expressed by a composition formula (Pbx, Cay, Srz) (Mg1/3 Nb2/3)O3 is used, where (x, y, z) represent mol ratio and meet the condition x+y+z=1. In the three-dimensional composition diagram wherein Pb(Mg1/3Nb2/3)O3, Ca(Mg1/3Nb2/3)O3, and Sr(Mg1/3Nb2/3)O3 constitute apices, the values of x, y, z shall lie within a region bounded by a quadrangle whose apices are A, B, C, D as given on the attached schema, excluding the line segment AD. Thereby a high no-load Q-value is obtained, and thermal variation of the resonance frequency is decreased, which should enhance the dielectric constant in the microwave region. This enables constructing a microwave apparatus in a small size, such as car telephone, portable telephone, etc.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, miniaturization of electronic devices has been demanded with the progress of communication using electromagnetic waves in the microwave region such as car telephones, portable telephones, and satellite broadcasting. For this purpose, it is necessary to reduce the size of each component that constitutes the electronic device. In these electronic 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, so to make a small dielectric resonator,
Materials with high dielectric constants are needed. Another characteristic required for the dielectric is that it has a low loss in the microwave range, that is, it has a high unloaded Q value, and that the temperature change of the resonance frequency is small, that is, the temperature change of the dielectric constant is small. Is.

Conventionally, as a dielectric material used in this field, a composition of Ba (Zn _1/3 Ta _2/3 ) O ₃ or BaO--TiO ₂ system and a composition in which a part of the composition is replaced with other elements are used. Was known. These are about 30 to 40 both the dielectric constant, to reduce the size of the dielectric resonator, the dielectric constant is too low, as higher dielectric constant material, BaO-TiO ₂ -Sm
₂ O ₃ based compositions and the like. (For example, JP-A-57-153
No. 09), this composition has a relative dielectric constant of about 80,
It has a high unloaded Q value of about 3000 at 2 to 4 GHz and a small temperature coefficient of relative permittivity.

However, in order to further miniaturize the resonator, a material having a higher dielectric constant is required, but a material having a high unloaded Q value and a small temperature coefficient is not known. On the other hand, the temperature coefficient of the dielectric is generally negative as the dielectric constant increases, but there is a material having a positive value such as PbZrO ₃ . Therefore, attempts have been made to reduce the temperature coefficient by combining materials having positive and negative values. Known materials having a negative temperature coefficient include TiO ₂ and SrTiO _3, and materials having a positive temperature coefficient include PbO-Zr.
The O ₂ was added lanthanide oxide PbO-Tb ₂ O ₃ -Zr
O ₂ based compositions and the like. (For example, JP-A-61-156
(See Japanese Patent No. 602) These materials have a relative dielectric constant of 10
Although it greatly contributes to the miniaturization of the resonator as 0 or more, the temperature coefficient τ _f of the resonance frequency is −1000 ppm.
A large temperature change of about / ° C is exhibited. In view of such a current situation, the inventor of the present invention has selected (Pb _1-x Ca _x ) Z as a material having a large dielectric constant and a small temperature coefficient of resonance frequency.
We have found rO ₃ and (Pb _1-x Ca _x ) (Mg _1/3 Nb _2/3 ) O ₃ and have already filed an application. (Japanese Patent Application No. 2-176008
(See Japanese Patent Application No. 2-176007)

[0005]

SUMMARY OF THE INVENTION The present invention provides a dielectric ceramic composition represented by the above composition formula (Pb _1-x Ca _x ) ZrO ₃ .
Alternatively, to provide a dielectric ceramic composition having a higher dielectric constant than the dielectric ceramic composition represented by the composition formula (Pb _1-x Ca _x ) (Mg _1/3 Nb _2/3 ) O _3. With the goal.

[0006]

To achieve this object, the dielectric ceramic composition of the present invention has a composition formula (Pb _x Ca _y S
r _z ) (Mg _1/3 Nb _2/3 ) O ₃ where x, y and z are molar ratios, x + y + z = 1, and Pb (Mg _1/3 Nb
_2/3 ) O ₃ , Ca (Mg _1/3 Nb _2/3 ) O ₃ and Sr (Mg _1/3 Nb
_2/3) O ₃ x in the ternary composition diagram whose vertices, the values of y and z (Table 3) are shown A, B, C and square segment on AD whose vertices D excluding region composition in, or composition formula (Pb _x Ca _y Sr _z) is represented by ZrO ₃ wherein x, y
And z represent a molar ratio, x + y + z = 1, and Pb
In the ternary composition diagram having ZrO ₃ , CaZrO ₃ and SrZrO ₃ as vertices, x, y, and z-square values shown in (Table 4) are rectangular line segments AD having A, B, C, and D as vertices. The composition of the composition is in the area to be excluded.

[0007]

[Table 3]

[0008]

[Table 4]

[0009]

[Action] This arrangement is included in the _{(Pb 1-x Ca x)} ZrO 3 or _{(Pb 1-x Ca x)} (Mg 1/3 Nb 2/3) O 3 (Pb
_1-x Ca _x ) is a ternary system containing Sr.

[0010]

EXAMPLES Example 1 An example of the present invention will be described below. Chemically highly pure MgO and Nb ₂ O ₅ were used as starting materials, and were weighed after adjusting the purity so that the molar ratio becomes equal, and put in a polyethylene ball mill using stabilized zirconia boulders. Pure water is added to the mixed medium and mixed for 17 hours. After mixing, the slurry is dried and placed in an alumina crucible for 100
It is calcined at 0 ° C. for 2 hours to synthesize MgNb ₂ O ₆ . to this,
PbO, CaCO ₃ and Sr, which are also chemically highly pure
CO ₃ is purity-corrected to obtain PbO, CaO and Sr.
A predetermined amount is weighed so that O has the compounding ratio shown in (Table 5). The composition of each sample number in (Table 5) is shown by numbers in FIG. These powders are put into the above ball mill and mixed in the same manner as described above. After mixing, dry the slurry,
Put in an alumina crucible and calcine at 750 to 850 ° C. for 2 hours. The calcined body is crushed by a raider, then crushed by the 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 as a binder was added and mixed, and then the mixture was granulated through a 32 mesh sieve and press-molded into a cylinder having a diameter of 13 mm and a thickness of about 5 mm at 100 MPa. Molded body is 600
After incinerating the binder by heating at ℃ for 2 hours, put it in a magnesia container and arrange calcinated powder of the same composition around it to prevent evaporation of PbO, and hold at 1100 to 1400 ℃ for 2 hours depending on the composition. And bake. The resonance frequency and the unloaded Q value of the obtained sintered body 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 4.5 GHz. Also,
Measure the resonant frequency at -25 ° C and 85 ° C, and
The temperature change rate (τ _f ) was calculated based on the value of ° C.
These results are also shown in (Table 5).

[0011]

[Table 5]

As is clear from this (Table 5), CaO
By replacing SrO with SrO, a higher relative dielectric constant can be realized. In FIG. 1, the relative permittivity is 65 or more and the no-load Q value is 400 or more in a rectangular region having sample numbers 1, 7, 14 and 13 of A, B, C and D in (Table 3) as vertices.
Above, the temperature change rate (τ _f ) of the resonance frequency is 200 ppm
/ ° C or lower. Sample Nos. 3 and 12 have an unloaded Q value of 40
Since it is lower than 0 and the relative dielectric constant of sample No. 15 is less than 65, it is outside the scope of the invention.

(Second Embodiment) The second embodiment of the present invention will be described below. Chemically high purity PbO and CaC
Purity correction of O ₃ , SrCO ₃ and ZrO ₂
Predetermined amounts of O, CaO, and SrO were weighed so that the compounding ratios shown in (Table 6) were obtained, a sintered body was prepared in the same manner as in Example 1, and the characteristics were measured. The results are also shown in (Table 6). The composition of each sample number in (Table 6) is shown by numbers in FIG.

[0014]

[Table 6]

As is clear from this (Table 6), CaO
By replacing SrO with SrO, a higher relative dielectric constant can be realized. In FIG. 2, A, B, C and D of (Table 4)
Sample Nos. 21, 23, 34, and 32 have vertices in a rectangular region with a relative dielectric constant of 60 or more and an unloaded Q of 40.
0 or more, the temperature deformation rate (τ _f ) of the resonance frequency is 130 pp
m / ° C or lower. Sample Nos. 22 and 27 had an unloaded Q value lower than 400, and Sample No. 35 had a relative permittivity of less than 60 and was low, so it was outside the scope of the invention.

As described above, according to this embodiment, the composition formula (Pb _1-x Ca _x ) ZrO ₃ or (Pb _1-x Ca _x ) (Mg _1/3 Nb
(Pb _1-x Ca _x ) contained in _2/3 ) O ₃ is a ternary system containing Sr, and the composition is such that the molar ratio of x, y and z in the formula is an appropriate predetermined value. A high unloaded Q value, a small temperature change of the resonance frequency, and an improved dielectric constant in the microwave region can reduce the size of the dielectric resonator. Therefore, it largely contributes to downsizing of microwave devices such as car phones and portable phones. Further, the dielectric ceramic composition of the present example can be used not only for the dielectric resonator but also for a microwave circuit board and the like, and has great industrial value.

[0017]

As described above, the present invention is based on the composition formula (Pb _1-x
Ca _x ) ZrO ₃ or (Pb _1-x Ca _x ) (Mg _1/3 Nb _2/3 ) O
₃ are included in the (Pb _1-x Ca _x) a ternary system containing Sr, x in the formula, the structure of the composition in which the molar ratio of y and z with appropriate predetermined value, the composition formula (Pb _{1- x} Ca _x ) ZrO ₃ or
It is possible to realize an excellent dielectric porcelain composition having a higher dielectric constant than the dielectric porcelain composition represented by the composition formula (Pb _1-x Ca _x ) (Mg _1/3 Nb _2/3 ) O _3. .

[Brief description of drawings]

FIG. 1 is a ternary composition diagram showing a composition range of main components of a dielectric ceramic composition according to a first embodiment of the present invention.

FIG. 2 is a ternary composition diagram showing the composition range of the main components of the dielectric ceramic composition of the second embodiment of the present invention.

Claims (2)

[Claims] 1. A composition formula _{(Pb x Ca y Sr z)} (Mg 1/3 Nb 2/3) O
₃ where x, y and z represent the molar ratio, x +
y + z = 1, and Pb (Mg _1/3 Nb _2/3 ) O ₃ , Ca (Mg _1/3
In a ternary composition diagram having Nb _2/3 ) O ₃ and Sr (Mg _1/3 Nb _2/3 ) O ₃ as vertices, the values of x, y and z are A, B and C shown in (Table 1). And a dielectric porcelain composition having a composition in a region excluding a rectangular line segment AD having vertices D and D. [Table 1] Represented by 2. A composition formula _{(Pb x Ca y Sr z)} ZrO 3,
In the formula, x, y and z represent a molar ratio, and x + y + z = 1
And in the ternary composition diagram having PbZrO ₃ , CaZrO ₃ and SrZrO ₃ as vertices, a rectangular line segment having x, y and z values shown in (Table 2) as A, B, C and D. A dielectric ceramic composition having a composition within a region excluding AD. [Table 2]