JP2964260B2 - Dielectric porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel dielectric ceramic composition suitable as a resonator or circuit board material in a microwave region.

(Prior art) In recent years, the development of microwave circuits into ICs with the practical use of car phones, cordless telephones, personal radios, and satellite broadcasting receivers, expansion of the use range of gun oscillators, use of gallium arsenide field effect transistors Dielectric porcelain in the microwave region is widely used, for example, in applications to oscillators.

Such microwave dielectric porcelain is mainly used for resonators, but the characteristics required for it are that the relative dielectric constant is large for the demand for miniaturization and the dielectric loss at high frequencies is small. For example, the mechanical quality factor Q value is large, and the change of the resonance frequency with respect to temperature is small.

Conventionally, as this kind of dielectric porcelain, for example, BaO-T
There are known iO ₂ -based materials, BaO-REO-TiO ₂ (where REO is a rare earth oxide, the same applies hereinafter), CaZrO ₃ -based materials, and the like.

(Problems to be Solved by the Invention) However, the relative dielectric constant εr of the BaO—TiO ₂ based material is 38.
40 and high and although the dielectric loss tanδ is as small as 2.0 × 10 ^-4, a single-phase hard to obtain those temperature dependence τf of the resonance frequency is zero, the temperature of the dielectric constant and the dielectric constant for the composition change Since the dependence greatly changes, it is difficult to stably control the temperature coefficient τf of the resonance frequency to be small while maintaining a high relative dielectric constant and a low dielectric loss.

Also, the BaO-REO-TiO ₂ based materials BaO-Nd ₂ O ₃ -
TiO ₂ system or BaO-Sm ₂ O ₃ -TiO ₂ system and the like are known, but in these systems, the dielectric constant εr is as high as 40 to 60,
In addition, a dielectric constant having a temperature coefficient τf of zero is obtained, but the dielectric loss tan δ is as large as 5.0 × 10 ⁻⁴ or more.

Further, in CaZrO ₃ system, various auxiliaries are added because the sinterability itself is poor. In any case, tan δ is 3-4.
It was as large as about × 10 ^-4 and the dielectric constant and temperature characteristics were insufficient.

As described above, none of the above-mentioned materials sufficiently satisfies the three characteristics required for the high-frequency dielectric material.

(Object of the Invention) The present invention has been devised in view of the above-mentioned drawbacks, and has a high dielectric constant (εr) (25 or more) and a high Q value (4500 It is an object of the present invention to provide a high-frequency dielectric ceramic composition having a small and stable resonance frequency temperature characteristic (τf).

(Means for Solving the Problems) The present inventors have studied the CaZrO ₃ system,
By replacing Zr with Nb, the sinterability of the system is greatly improved, and a porcelain with good crystallinity can be obtained.In terms of characteristics, a porcelain with high dielectric constant, high Q value, low τf and excellent strength It was found that it could be obtained.

That is, the dielectric porcelain composition of the present invention has CaO, ZrO ₂ and N
Using b ₂ O ₅ , these composition formulas are adjusted so that the molar ratio in the formula xCaO.yZrO ₂ .zNbO _{5/2 is} 0.9 <x / (y + z) ≦ 1.10. <z / (y + z) ≦ 0.5 It is characterized by having done.

The present invention has an effect of improving the sinterability by substituting a part of Zr with Nb for CaZrO ₃ to increase the dielectric constant and Q value in a microwave region, and adjusting the Ca / Zr ratio. Therefore, it is based on the finding that τf can be controlled while the dielectric constant and the Q value are constant.

The reason for setting the molar ratio of each oxide in the above range in the dielectric ceramic composition of the present invention is that the (x / y + z) ratio is 0.9.
Below, the Q value is low, and when it exceeds 1.1, the sinterability of the porcelain decreases, and when the (z / y + z) ratio exceeds 0.5, the temperature coefficient of the resonance frequency becomes undesirably large. However, when Ca / Zr = 1, if Nb is not added at all, the sinterability is poor and the Q value is low. Even within these ranges, 1 ≦ x / (y +
z) ≦ 1.1, 0 <z / (y + z) ≦ 0.5
Further, it is more preferable that x / (y + z) = 1 and 0.01 ≦ z / (y + z) ≦ 0.1.

The dielectric porcelain of the present invention is also excellent in strength, and particularly when z / (y + z) is 0.1 or less, 15 kg / mm ²
The above strength is obtained.

When producing the ceramic in the present invention is an oxide of the metal constituting the ceramic, i.e. CaO, can be converted to the oxide by ZrO ₂ and Nb ₂ O _5, firing, for example carbonates, nitrates, such as sulfate After weighing and mixing with the compound, the mixture is calcined at 1200 to 1500 ° C. if desired. After molding this mixture or calcined powder, it is fired in the air at 1500 to 1700 ° C. to obtain a porcelain.

Incidentally, the dielectric material of the present invention has a tendency that the Q value greatly fluctuates depending on the amount of impurities, and it is desirable that the raw material to be used is also of high purity, and specifically, B which is the same as Ca, Zr, and Nb is used.
It is desirable that the amount of impurities such as Al, Si, Fe, etc. excluding a, Sr, Hf, and Ta be suppressed to 1% by weight or less.

In the present invention, Ba and Sr may be substituted for Ca element, Hf for Zr, and Ta for Nb at 5 mol% or less.

 Hereinafter, the present invention will be described with reference to the following examples.

(Examples) Starting materials except high-purity calcium carbonate (CaCO ₃ ) having an impurity amount of 0.1% by weight or less excluding Ba and Sr, zirconium oxide (ZrO ₂ ) having an impurity amount of 0.1% by weight or less excluding Hf, and Ta are excluded. Using each powder of niobium oxide (Nb ₂ O ₅ ) having an impurity amount of 0.1% by weight or less, weighing them so that the x, y, and z values in the above formula (1) become the ratios in Table 1, and Pure water was added and wet mixing was performed overnight using an agate. After drying this mixture, the mixture was calcined at 1350 to 1600 ° C. for 2 hours.
Press molding was performed under a pressure of 00 kg / cm ² to prepare a distortion-free cylindrical molded body having a diameter of about 20 mm and a height of about 10 mm. Thereafter, the molded body was subjected to a binder removal treatment at 400 ° C. for 4 hours.
Calcination in air at a temperature of 11700 ° C. for 2 hours.

The obtained porcelain was subjected to surface polishing and cylindrical grinding to obtain a sample. Using this sample, dielectric cylinder resonator method
Dielectric constant (εr), Q value (1 / tan
δ), the temperature coefficient of resonance frequency (τf) is measured, and τf
Was measured from −40 to + 85 ° C.

 The results are shown in Table 1.

As is clear from Table 1, sample No. 1 which is CaZrO ₃
Has a low Q value. On the other hand, by adding Nb, the Q value is greatly improved as shown in Sample Nos. 2 to 13, 15. However, Sample Nos. 12 to 13 having an Nb amount exceeding the range of the present invention have large temperature characteristics, which is not desirable.

Samples Nos. 1 and 14 to which Nb was not added had extremely low Q values. Incidentally, even in a system to which Nb was added, x / (y + z) = 0.9.
Of sample No. 16 had a low Q value.

Further, the temperature characteristics of Sample No. 13 containing no Zr were deteriorated.

The dielectrics within the scope of the present invention all have characteristics of a relative dielectric constant of 25 or more, a Q value of 4000 or more, and a τf of ± 100 (ppm / ° C.) or less, and particularly, a / b + c = 1, c / b + c In Sample Nos. 3, 4, and 5 having 0.03 to 0.1, a dielectric constant of 29 to 33, a Q value of 8000 or more, and a temperature characteristic of ± 10 (ppm / ° C.) or less were achieved.

In addition, when the transverse rupture strength of Sample Nos. 3 and 5 was measured by JISR1601, No. 3 was 19.4 kg / mm ² and No. 5 was 16.7 kg / m 2.
m ^2, and the other samples also had a strength of 10-20 kg / mm ^2.

(Effects of the Invention) As described in detail above, the dielectric porcelain composition of the present invention contains Ca
By adding Nb ₂ O ₅ to O, ZrO ₂ , and replacing Zr with Nb, the sinterability of the porcelain is increased, and it has a high Q value in the microwave region and the dielectric constant and the temperature characteristics of the resonance frequency. And high strength porcelain can be provided. As a result, it is possible to increase the reliability for use as a resonator or a circuit board material, and at the same time, to reduce the size.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H01B 3/12 313 C04B 35/00 C04B 35/48 H01G 4/12 H01P 7/10

Claims (1)

(57) [Claims] 1. A dielectric ceramic composition having a composition formula of xCaO.yZrO ₂ .zNbO _5/2 , wherein 0.9 <x / (y + z) ≦ 1.10 <z / (y + z) ≦ 0.5.