JP3098763B2 - Dielectric resonator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dielectric resonator composed of dielectric porcelain.

2. Description of the Related Art In recent years, with the development of communications using electromagnetic waves in the microwave region, such as automobile telephones, portable telephones, and satellite broadcasting,
There is a demand for miniaturization of equipment. For this purpose, it is necessary to reduce the size of individual components constituting the device.

In these devices, a dielectric is incorporated in a filter element or an oscillation element as a dielectric resonator. When using the same resonance mode, the size of the dielectric resonator is inversely proportional to the square root of the dielectric constant of the dielectric material. is necessary. Other characteristics required for the dielectric are low loss in the microwave region, that is, a high unloaded Q value, and a small temperature change in the resonance frequency, that is, a small temperature change in the relative permittivity. It is.

Conventionally, dielectrics used in this field include Ba
The composition of (Zn _1/3 Ta _2/3 ) O ₃ , BaO—TiO ₂ system and the composition in which a part of the composition is replaced by another element are known. Each of these has a relative dielectric constant of about 30 and is too low to reduce the size of 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,
It has a high no-load Q factor of about 3000 at 4 GHz and a small temperature coefficient of relative permittivity.

However, in order to further reduce the size of 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 is not known. On the other hand, the temperature coefficient of the dielectric is generally negative as the relative dielectric constant increases, but there are some such as PbZrO ₃ having a positive value.
Therefore, attempts have been made to reduce the temperature coefficient by combining materials having positive and negative values. As materials having a negative temperature coefficient, TiO ₂ and SrTiO ₃ are known, and as a material having a positive temperature coefficient, a system obtained by adding a lanthanide oxide to PbO-ZrO ₂ is disclosed in disclosed in 156602 JP been the like _{PbO-Tb 2 O 3 -ZrO 2} . In these materials, the relative permittivity is as large as 100 or more, which greatly contributes to the miniaturization of the resonator.
_f indicates a large temperature change of about -1000 ppm / ° C.

Problems to be Solved by the Invention In such a conventional dielectric ceramic composition, there is a problem that the relative dielectric constant and the unloaded Q value are large, and the condition that the temperature change of the relative dielectric constant is small is not satisfied. .

The present invention solves the above-mentioned problems, and provides a dielectric resonator using a dielectric ceramic composition having a large relative dielectric constant, low loss in a microwave region, and a small temperature change rate of the relative dielectric constant. The purpose is to provide.

Means for Solving the Problems The present invention provides xPbO-y (Mg
_1/3 Nb _2/3 ) O ₂ —Consists of a composition composed of lead oxide, magnesium oxide, niobium oxide and calcium oxide represented by the composition formula of CaO, where x, y, and z are mol percentages and 0.05 ≦ x ≦ 0.45 0.4 ≦ y ≦ 0.55 0.15 ≦ z ≦ 0.4 Note that the dielectric resonator uses a ceramic composition satisfying the condition of x + y + z = 1.

Action The present invention has a small size and high efficiency by using a porcelain composition in which a part of Pb of lead magnesium niobate (Pb (Mg _1/3 Nb _2/3 ) O ₃ ) is substituted for Ca by the above-described configuration. A dielectric resonator having a Q value and excellent temperature characteristics is produced.

Example Hereinafter, an example of the present invention will be described.

MgO is a starting material is chemically pure, and Nb ₂ O _5, were weighed after performing the purity correction so that an equal amount in a molar ratio, a polyethylene ball mill using stabilized zirconia cobblestone Add the pure to the mixing medium and mix for 17 hours. After mixing, the slurry is dried, put into a crucible made of alumina, and calcined at 1000 ° C. for 2 hours to synthesize MgNb ₂ O ₆ . After correcting the purity of PbO and CaCo ₃ , which are also chemically highly pure, a predetermined amount is weighed according to the blending amount shown in the following table. Put these powders into the above-mentioned ball mill,
Mix as before. After mixing, the slurry is dried, put into a crucible made of alumina, and calcined at 750 to 850 ° C. for 2 hours.
The calcined body is pulverized by a raikai machine, then pulverized by the above-mentioned ball mill for 17 hours, and dried to obtain a raw material powder. 6% by weight of a 5% aqueous solution of polyvinyl alcohol as a binder is added to this powder, mixed, and then granulated through a 32 mesh sieve, and pressed into a column having a diameter of 13 mm and a thickness of about 5 mm at 100 MPa. The molded body is heated at 600 ° C. for 2 hours to incinerate the binder, put in a magnesia container, and place a calcined powder of the same composition around to prevent evaporation of PbO.
It is kept at 0 to 1400 ° C. for 2 hours for firing. A dielectric resonator is prepared from the obtained sintered body, and its resonance frequency and unloaded Q
The value was determined. The relative permittivity was calculated from the dimensions of the sintered body and the resonance frequency. The resonance frequency was between 2 and 6 GHz. Further, the resonance frequencies at −25 ° C. and 85 ° C. were measured, and the temperature change rate (τ _f ) was calculated based on the value at 20 ° C. The results are shown in the table.

Lead oxide As is apparent from Table, magnesium oxide, composition a composition consisting of niobium oxide and calcium oxide formula _{xPbO-y (Mg 1/3 Nb 2/3} ) when expressed as O ₂ -zCaO, x, y, where z is a mole percentage and 0.05 ≦ x ≦ 0.45 0.4 ≦ y ≦ 0.55 0.15 ≦ z ≦ 0.4 However, in a composition satisfying the relationship of x + y + z = 1, the relative dielectric constant is as high as 35 to 107 and the unloaded Q value is 300 or more. And the temperature change of the resonance frequency is 200 ppm / ° C. or more. In particular, sample numbers 7, 8, and 12 have a relative dielectric constant of 80 or more, a no-load Q value of 400 or more and a
It exhibited excellent characteristics of not more than 00 ppm / ° C.

However, a composition of x, y, and z outside the above range is not desirable as a microwave dielectric. That is, CaO
When the composition is less than 0.15 (sample No. 6 in the table), the unloaded Q value is 100 or less. In the composition where CaO is more than 0.4 (sample No. 11 in the table), the relative dielectric constant is 35 or less. Not suitable. In the case of a composition in which (Mg _1/3 Nb _2/3 ) O ₂ is less than 0.4 (sample No. 18 in the table), the unloaded Q value is 200 or less, and 1400 ° C. in a composition exceeding 0.55 (sample No. 1 in the table). At the following temperatures, it is not suitable for use because it does not densely sinter.

Effect of the Invention As is apparent from the above embodiments, according to the present invention, since the dielectric ceramic composition is composed of lead oxide, magnesium oxide, niobium oxide and calcium oxide, the unloaded Q value and the microwave region Has a high relative dielectric constant,
A dielectric resonator having a small change in the resonance frequency with temperature can be provided. Therefore, the relative permittivity in the microwave region is improved, so that the dielectric resonator can be reduced in size, which greatly contributes to miniaturization of microwave devices such as a mobile phone and a portable phone. Further, the present invention can be used not only for a dielectric resonator but also for a stripline resonator formed on a microwave circuit board, and has great industrial value.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-1047 (JP, A) JP-A-63-25261 (JP, A) JP-A-55-51758 (JP, A) JP-A-55-51758 121959 (JP, A) JP-A-3-285864 (JP, A) Tokyo Chemical Industry Co., Ltd., “Lee Inorganic Chemistry” (April 15, 1982); 328-329

Claims (1)

(57) [Claims] A composition comprising lead oxide, magnesium oxide, niobium oxide and calcium oxide is represented by the composition formula xPbO-y (Mg _1/3 Nb _2/3 ) O ₂ -zCaO, where x, y, z
Is a molar percentage of 0.05 ≦ x ≦ 0.45 0.4 ≦ y ≦ 0.55 0.15 ≦ z ≦ 0.4, where x + y + z = 1, and a resonance frequency of 2 to 6 GHz and a no-load Q value of 300 or more. Dielectric resonator using.