JPH0465017A - Dielectric ceramic compound - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to dielectric ceramic compositions used in the microwave range.

Background of the Invention In recent years, with the development of communications that utilize the tM1 wave in the microwave range, such as car phones, portable telephones, and satellite broadcasting,
There is a demand for smaller equipment. For this purpose, the individual components that make up the equipment need to be miniaturized.

In these devices, dielectrics are incorporated into filter elements and oscillation elements as dielectric resonators. When using the same resonance mode, the size of a dielectric resonator is inversely proportional to the square root of the dielectric constant of the dielectric material. Therefore, in order to create a small dielectric resonator, materials with a high relative permittivity are used. is necessary.

Other characteristics required of a dielectric material are low loss in the microwave region, that is, a high no-load Q value, and small temperature changes in the resonant frequency, that is, small temperature changes in the dielectric constant. It is.

The dielectric material conventionally used in this field is B.
a (Z n +ziT a z7z) Oa,, B
a OT I 02-based compositions and compositions in which some of them are replaced with other elements have been known. All of these have a dielectric constant of about 30, which is too low to make the resonator smaller. Bad-TiO2-3m208 is a material with a higher specific permittivity, as disclosed in Japanese Patent Application Laid-open No. 57-1.
It is disclosed in Japanese Patent No. 5309. This system has a dielectric constant of about 80, a high no-load Q value of about 3000 at 2 to 4 GHz, and a small temperature coefficient of dielectric constant.

However, in order to further downsize the resonator, materials with higher dielectric constants are required, but materials with high no-load Q values and small temperature coefficients are not known. on the other hand,
The temperature coefficient of a dielectric is generally negative as the dielectric constant increases, but there are some that have a positive value, such as P b Z r Ofl. Therefore, attempts have been made to reduce the temperature coefficient by combining materials with positive and negative values. Materials with negative temperature coefficients include T s O2 and S r
T r OB is known, and an example of a material having a positive temperature coefficient is PbO-Tb203-ZrO2, which is a system in which a lanthanide oxide is added to PbO-Zr0□, which was disclosed in JP-A-61-156602. and so on.

These materials have a large relative dielectric constant of 100 or more and greatly contribute to miniaturization of the resonator, but the temperature coefficient τ of the resonance frequency exhibits a large temperature change of about -1000 PPm/°C.

Problems to be Solved by the Invention These conventional dielectric ceramic compositions have a problem in that they do not meet the requirements of large relative permittivity and no-load Q value, and small temperature change in relative permittivity. .

The present invention solves the above problems, and aims to provide a dielectric ceramic composition that has a large dielectric constant, low loss in the microwave region, and a small temperature change rate of the dielectric constant. .

Means to solve problems In order to achieve the above object, the present invention uses xPb.

y (Mg, / B Nb2/3)02 zcao
Lead oxide and magnesium oxide are represented by the composition formula:

It is composed of a composition consisting of niobium oxide and calcium oxide, where x, y, and z are molar percentages, and 0.05≦X≦0,
45 0.4 ≦y≦0.55 0.15≦z 'J1.4 However, the condition of x+y+z=1 is satisfied.

Effect The present invention has the above-described structure, in which a part of the lead in magnesium niobate (P b (Mg+7z Nbzz3) 03 ) is replaced with calcium, and while maintaining the high dielectric constant of lead acid, it has a high dielectric constant in the microwave region. Q value and excellent temperature characteristics appear.

Example An embodiment of the present invention will be described below.

The starting material is MgO, which has high chemical purity.

Nb and O6 are weighed after correcting their purity so that they are equal in molar ratio, placed in a polyethylene ball mill using stabilized zirconia cobblestones, and the pure mixture is added to the mixing medium and mixed for 17 hours. After mixing, the slurry was dried, placed in an alumina crucible, and calcined at 1000°C for 2 hours.
gNb,06 is synthesized. After correcting the purity of PbO and CaCo3, which are also chemically highly pure,
Weigh out the prescribed amount according to the amount shown in the table below. These powders are placed in the aforementioned ball mill and mixed in the same manner as above. After mixing, the slurry is dried, placed in an alumina crucible, and calcined at 750 to 850°C for 2 hours. After crushing the calcined body using a Raikai machine, the calcined body was crushed using the aforementioned ball mill.
Pulverize for hours, dry, and use as raw material powder. To this powder, 6% by weight of a 5% aqueous solution of polyvinyl alcohol as a binder is added and mixed, then granulated through a 32-mesh sieve, and press-molded at 100 MPa into a cylindrical shape with a diameter of 13-1 and a thickness of about 5 mm. The molded body was heated at 600°C for 2 hours to incinerate the binder, then placed in a magnesia container, and placed around it with calcined powder of the same composition to prevent evaporation of PbO, at 1100 to 1400°C depending on the composition. Hold and bake for 2 hours. The resonance frequency and no-load Q value of the obtained sintered body were determined by measurement using the dielectric resonator method. Also, the relative dielectric constant was determined from the dimensions of the sintered body and the resonance frequency. The resonance frequency is 2~
6G) (z. The resonance frequencies at -25°C and 85°C were also measured, and the rate of temperature change (τt) was calculated using the value at 20°C as a reference. These results are shown in the table.

(Left below) As is clear from the table, when a composition consisting of lead oxide, magnesium oxide, niobium oxide and calcium oxide is expressed as the composition formula %, x, y, z are mole percentages and 0. 05≦
X≦0.45 0.4≦y≦0.55 0.15≦2≦0.4 However, in a composition that satisfies the relationship z-4-y+z=1, the dielectric constant is as high as 35 to 107, and no Load Q value is 300
or more, and the temperature change in the resonant frequency is 2
00ppm/'c or less. Especially sample numbers 7 and 8.1
No. 2 had a dielectric constant of 80 or more, an unloaded Q value of 400 or more, and a temperature change in resonance frequency of 200 ppm/''C or less, showing excellent characteristics.

However, compositions of x, y, and t outside the above ranges are not desirable as dielectrics for microwaves.

That is, in a composition with less than 0.15 CaO (sample number 6 in the table), the no-load Q value is 100 or less, and the
For compositions with aO greater than 0.4 (sample number 11 in the table),
Since the specific gN ratio is 35 or less, it is unsuitable for use. Also(
For compositions where M g l/s N b tyx )02 is less than 0.4 (sample number 18 in the table), the unloaded Q value is 200.
The composition is as follows and exceeds 0.55 (sample number 1 in the table)
However, it is not suitable for use at temperatures below 1400°C because it does not sinter densely.

Effects of the Invention As is clear from the above embodiments, according to the present invention, since the dielectric ceramic composition is made of lead oxide, magnesium oxide, niobium oxide, and calcium oxide, the no-load Q value and the microwave region are low. It is possible to provide a dielectric ceramic composition having a high dielectric constant and a small temperature change in resonance frequency. Therefore, since the dielectric constant in the microwave region is improved, the dielectric resonator can be made smaller, which greatly contributes to the miniaturization of microwave equipment such as car phones and portable telephones. Moreover, it can be used not only for dielectric resonators but also for microwave circuit boards, etc., and has great industrial value.

Claims (1)

[Claims] A composition consisting of lead oxide, magnesium oxide, niobium oxide and calcium oxide has the composition formula xPbO-y (Mg_1_/_3Nb_2_/_3)
When expressed as O_2-zCaO, x, y, z are mole percentages, and 0.05≦x≦0.45 0.4≦y≦0.55 0.15≦z≦0.4 However, x+y+z=1 A dielectric ceramic composition characterized by satisfying the following conditions.