JP2899909B2 - Microwave 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 made in view of the above-mentioned drawbacks, and has a high dielectric constant (ε) (25) in order to make it possible to miniaturize a resonator.
It is an object of the present invention to provide a high-frequency dielectric ceramic composition having a high Q value (4000 or more), a small temperature characteristic (τf) of the resonance frequency, and a stable high frequency.

(Means for Solving the Problems) The present inventors have studied the CaZrO ₃ system,
By containing at least one oxide selected from LaO _3/2 , CeO ₂ , NdO _3/2 , SmO _3/2 , and YO _3/2 as an additive in a proportion of 1 to 10 mol%, the system is fired. The present inventors have found that porcelain with significantly improved crystallinity, good crystallinity, high porosity, high Q value, low τf, and excellent strength can be obtained in terms of characteristics. In the present invention, CaZrO ₃ is selected from rare earth element oxides as an additive that acts as a so-called sintering aid. However, when the dielectric properties in the microwave region were examined simultaneously, it was found that the properties differed depending on the rare earth element oxide used. La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ , Sm ₂ O ₃ and Y among known rare earth element oxides
₂ O ₃ exhibits particularly excellent dielectric properties.
₂ O ₃ and Nd ₂ O ₃ were particularly excellent in Q value and stability of characteristics.

The dielectric porcelain composition of the present invention, CaZr
O ₃ 90 to 99 mol% and, in particular 95 to 99 mol%, LaO _3/2, Ce
At least one selected from O ₂ , NdO _3/2 , SmO _3/2 and YO _3/2
1 to 10 mol%, particularly 1 to 5 mol% of the species, wherein the amount of the rare earth element oxide is less than 1 mol%;
That is, when the amount of CaZrO ₃ is more than 99 mol%, the sinterability is insufficient, the dielectric properties, particularly the Q value is low, and the amount of the rare earth element oxide is 10%.
If it exceeds mol%, that is, if the amount of CaZrO ₃ is less than 90 mol%, sinterability is improved, but from the viewpoint of dielectric properties, the Q value and the dielectric constant are undesirably reduced.

The dielectric porcelain of the present invention is also excellent in strength, particularly when the rare earth oxide content is 10 mol% or less, 15 kg / m
m ² or more strength is obtained.

When producing the ceramic in the present invention is an oxide of the metal constituting the ceramic, i.e. CaO, ZrO ₂ and La ₂ O _3, CeO _2,
After weighing and mixing each powder of NdO ₃ and Sm ₂ O ₃ or a compound which can be converted into the oxide by calcination, for example, carbonate, nitrate, nitrate, etc., it is calcined at 1200 to 1500 ° C. if desired. After molding this mixture or calcined powder,
Porcelain can be obtained by firing in the atmosphere at 00 ° C.

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

(Example) High-purity CaCO ₃ , ZrO ₂ , La ₂ O ₃ , CeO ₂ ,
Using each powder of Nd ₂ O ₃ , Sm ₂ O ₃ , and Y ₂ O ₃ , weigh the rare earth element oxide with respect to CaZrO ₃ to the composition shown in Table 1 (the balance is CaZrO ₃ ), and then add pure water. Ball mill mixing was carried out day and night using agate cobblestone. After drying the mixture was calcined for 2 hours at from 1,350 to 1,600 ° C., press molding φ about 20mm the powder was obtained and sieved from further adding about 1% by weight of the binder at a pressure of about 1000 Kg / cm ² Then, a cylindrical molded body having a thickness of about 10 mm and having no distortion was prepared. Thereafter, the molded body was subjected to a binder removal treatment at 400 ° C. for 4 hours, and further calcined at a temperature of 1400 to 1600 ° C. for 2 hours in air.

The obtained porcelain was subjected to plane polishing and cylindrical grinding to obtain a measurement sample. Using this sample, the dielectric constant (εr), the quality factor Q value (1 / tanδ), and the temperature coefficient of the resonance frequency (τf) were measured at a resonance frequency of 4 to 6 GHz by the dielectric cylinder resonator method. , -40 to + 85 ° C.

 The results are shown in Table 1.

As is clear from Table 1, sample No. 1 containing only CaZrO ₃
Has a low Q value. On the other hand, by adding a rare earth element oxide, the Q value can be increased. Also,
Sample No. 6 in which the amount of rare earth exceeds 10 mol% has a low Q value and is not suitable for the purpose of the present invention.

In contrast to these comparative examples, the samples of the present invention all show excellent microwave dielectric properties of a dielectric constant of 25 or more, a Q value of 4000 or more, and τf ± 20, and particularly as a rare earth element oxide.
The system to which LaO _3/2 and NdO _3/2 are added is specifically stable,
In addition, the Q value was high, and the dielectric constant and the temperature characteristics were better than those of the others. Sample Nos. 2, 3, 7, and 8
When the four-point bending strength was measured based on JISR1601,
In kg / mm ² units, it showed high strength none of 18.3,20.0,16.6,16.2.

(Effects of the Invention) As described in detail above, the dielectric porcelain composition of the present invention contains Ca
The addition of a predetermined rare earth element oxide to O and ZrO ₂ enhances the sinterability of the porcelain and increases the Q in the microwave region.
It is possible to provide a porcelain having high strength, excellent dielectric constant, excellent temperature characteristics of resonance frequency, and high strength. 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.

Claims (1)

(57) [Claims] (1) 90-99 mol% of CaZrO ₃ , LaO _3/2 , CeO ₂ , Nd
At least one selected from O _3/2 , SmO _3/2 and YO _3/2
A microwave dielectric porcelain composition comprising 0 mol%.