JPH0524845A - Method for controlling dielectric characteristic of dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To manifest excellent dielectric characteristics in good reproducivity and at a low cost, and to freely control the dielectric characteristics manifested even when the same calcinated product is used. CONSTITUTION:A method for crushing the calcined product of a composition having a Perovskite type structure of general formula ABO3 or A1-xBO3-x (an alkaline earth metal ion such as Ba or Sr ion is fed at the A site) and subsequently sintering the crushed product comprises crushing the calcined product in a polar solvent, simultaneously adjusting the amount of the alkaline earth metal ion eluted in a solvent by the selection of the crushing condition, removing the liquid fraction from the produced slurry, drying the solid fraction alone and subsequently sintering the dried solid fraction. The method is particularly effective for a composition containing Mg, Zn or Ta fed into the B site.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling dielectric properties of a dielectric ceramic composition having a perovskite structure. More specifically, ABO ₃ or A _1-x
When pulverizing the calcined product of the composition represented by BO _3-x , the amount of alkaline earth metal ions such as barium (Ba) and strontium (Sr) to be eluted can be adjusted by selecting the pulverizing conditions. , A method for controlling dielectric properties. This technique can be used for manufacturing, for example, a dielectric resonator material used in a high frequency region such as microwaves and millimeter waves, a dielectric substrate material for MIC (microwave IC), and the like.

[0002]

2. Description of the Related Art Various series of materials have already been developed and used as high frequency dielectric ceramic materials used in microwaves and millimeter waves. For example, Ba (Zn _1/3 , Ta
_{2/3) O 3 -Ba (Zn 1/3} , Nb 2/3) O 3 system, or _{Ba (Zr x, Zn y,} Ta z) O 7/2-x / 2-3y / z systems like Therefore, dielectric ceramic compositions having a high Q value have been obtained in these composition systems.

There is also a technique for obtaining a high frequency dielectric ceramic composition having a high Q value by making the Ba composition ratio shorter than the stoichiometry. One example is Ba (Zn
_{In the 1/3} , Ta _2/3 ) O ₃ -based material, the Ba composition ratio is slightly insufficient, and the calcined product is crushed only by the dry method, and after molding, it is baked at 1600 to 1700 ° C. for 1 to 10 hours. There is a method (JP-A-2-51464).

In these conventional techniques, the control of the dielectric properties has been performed exclusively by adjusting the composition ratio of the material. In other words, it is a method of controlling the composition so that desired dielectric characteristics can be obtained by precisely adjusting the composition ratios of a plurality of raw material materials and manufacturing them in a manufacturing process with high reproducibility.

[0005]

In the production of a dielectric material, it is necessary to obtain excellent dielectric properties with good reproducibility and at low cost. However, in the conventional method as described above, it is necessary to precisely weigh many kinds of raw materials first, and in addition, it is necessary to pay close attention to the purity of the raw materials and the reproducibility of the manufacturing environment, which takes time. However, there is a drawback that mistakes are likely to occur.

In addition, the dielectric ceramic composition of the perovskite structure represented by ABO _{3 in} which alkaline earth metal ions such as Ba and Sr are introduced into the A site has a structure that causes A site ions in the manufacturing process. Is easily desorbed, and the resulting carbonate has a particle size several tens of times that of the pulverized powder and significantly impairs sinterability. For this reason, there arise problems that the firing conditions become strict and the characteristics deteriorate.
This tendency is particularly remarkable in low-loss materials such as Ba (Zn _1/3 , Ta _2/3 ) O ₃ series or Ba (Mg _1/3 , Ta _2/3 ) O ₃ series. This is because these low loss materials have high firing temperatures.

Further, if the Ba composition ratio is made lower than the stoichiometry,
In the manufacturing method in which only dry pulverization is performed, carbonate is not generated because wet pulverization is not performed, but since the pulverized powder has a large particle size, a high firing temperature is still required to improve the dielectric properties.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to exhibit excellent dielectric properties with good reproducibility and at low cost, and to develop even when the same calcined powder is used. It is an object of the present invention to provide a method capable of freely controlling the dielectric properties of the material.

[0009]

The present invention is of general formula ABO.
_In this method, a calcined product of a composition having a perovskite structure represented by ₃ or A _1-x BO _3-x is crushed and fired. However,
x is a value within the range allowed as a lattice defect of the perovskite structure, and is a composition in which an alkaline earth metal ion such as Ba or Sr is introduced into the A site. Here, the feature of the present invention is that the calcined product is pulverized in a polar solvent, the elution amount of alkaline earth metal ions to the solvent is adjusted by selecting the pulverization conditions at that time, and the resulting slurry is subjected to solid-liquid separation. Then, the liquid content is removed, and only the solid content is dried and used for sintering.

Here, the selection of the grinding conditions includes selection of grinding media (selection of ball mill container or ball material, container shape, ball amount, etc.), selection of solvent (selection of solubility such as solvent type and temperature), and grinding. For example, time selection. The polar solvent used is a solvent composed of polarized molecules, such as water or alcohol. The present invention is particularly effective in the case of a composition having Mg, Zn, and Ta introduced at the B site.

In the present invention, the reason why the range of x is set to a value within the range allowed as the lattice defect of the perovskite structure in each dielectric ceramic composition is that the second phase is generated due to the factor of improving the sinterability. This is to remove the factor. In addition, introducing alkaline earth metal ions such as Ba and Sr to the A site and introducing Mg, Zn, and Ta to the B site are particularly useful in the high frequency region of these compositions, and dielectrics used in this region Strict control of dielectric properties is required for body porcelain compositions, and further, these porcelain compositions are difficult to sinter, and deterioration of sinterability caused by carbonate generated by desorbed A site ions. Is a problem.

[0012]

The A site ion can coexist in a polar solvent such as water or alcohol. Therefore, when such a polar solvent is used for pulverization, a part of the A site ions of the perovskite type crystal structure escapes into the solvent. In the present invention, for example, A
_{When a} calcined product of a dielectric porcelain composition having a composition of _1-x BO _3-x is crushed in water, A site ions are eluted in a polar solvent, resulting in A _1-xy BO _3-xy + yA (OH) ₂ . Become. Of these, yA (OH) ₂ of the second term is dissolved in the liquid of the slurry, and is removed by removing the liquid component by solid-liquid separation, and finally, A _{1-xy of} the first term, which is the solid component. BO
Only _3-xy remains. Therefore, the y amount can be controlled by changing the pulverization conditions, whereby a desired composition can be obtained and the dielectric properties can be freely controlled.

By the way, A _1-xy BO _3-xy + yA (OH)
_{When 2} is dried in the air as it is, carbon dioxide in the air reacts with A (OH) ₂ to produce A _1-xy BO _3-xy + yACO.
₃ , yACO _{3 of} the second term was deposited as large crystals, which impeded the sinterability. However, in the present invention, since the liquid component is removed, such a hardly-sinterable precipitate does not occur.

[0014]

EXAMPLE High-purity BaCO ₃ , Zn as a starting material
Using O, Ta ₂ O ₅ and ZrO ₂ , the following general formula (1-
m) Ba _1-x (Zn _1/3 , Ta _2/3 ) O _3-x + mBa
The values of m and x were adjusted so that the composition represented by _1-x ZrO _3-x was adjusted, and the sample was weighed. This was wet-mixed with pure water for 20 hours using a resin pot, taken out, dried, and calcined at 1300 ° C. for 10 hours. 130 g of this calcined product was used as a ball of partially stabilized zirconia (diameter 10
mm, weight 1 kg) and pure water 450 cc were put in a resin pot (diameter 15 cm) and wet-ground for 20 to 60 hours. The obtained slurry was filtered, the supernatant was separated and removed by filtration, the residue was dried, and then a binder was added to granulate. Apply 3000 kg / cm ² of pressure with a press machine,
A disk having a diameter of 14 mm and a thickness of 6 mm was molded, and then this molded product was baked in an oxidizing atmosphere at a predetermined temperature for a predetermined time to produce a dielectric ceramic composition. The upper and lower surfaces and the side surface were scraped off by about 1 mm to obtain a measurement sample.

The relative permittivity εr and Q value of each sample at a resonance frequency of about 10 GHz were measured by the postresonator method. The experimental results are shown in FIGS. First, it can be seen from FIG. 3 that the elution amount of Ba into the grinding solvent changes when the grinding time is changed, and the elution amount of Ba increases as the grinding time increases. Under the above conditions, the leaching time is about 20 hours, the Ba elution amount is about 0.25%, and the leaching amount is 0.7 at 60 hours.
Reach 5%. These values are calculated from the values obtained by measuring the weight of the separated supernatant in the form of BaCO ₃ by allowing it to stand (dry) in the air.

FIG. 1 shows the change in Q value with respect to the Ba elution amount (BaCO ₃ conversion amount), and FIG. 2 shows the Ba elution amount (Ba
The change in relative permittivity εr with respect to the CO ₃ conversion amount is shown. In the region where the Ba elution amount is 0.75% or more, the dielectric properties are rather deteriorated. According to the observation result by X-ray, the crystal structure is distorted and the second phase (second phase) is generated in this region. In the region of 0.5 to 0.75%, the perovskite type crystal structure was observed and the second phase was not observed, but the dielectric property is almost constant. 0.5%
In the following region, the Q value and the relative permittivity εr greatly change according to the change in the Ba elution amount. From this, in the case of this example, by changing the pulverization conditions in the region where the Ba elution amount was 0.5% or less, a slight change in the crystal structure caused by the pulverization was caused, which made it possible to control the dielectric properties. It turns out that

In the above embodiment, only the crushing time is changed, but the same effect can be obtained by changing other crushing conditions (crushing media, solvent type, temperature, etc.). Further, the plurality of crushing conditions may be changed at the same time.

[0018]

As described above, the present invention pulverizes a calcined product in a polar solvent, and adjusts the amount of alkaline earth metal ions eluted into the polar solvent by selecting the pulverization conditions at that time, Since it is a method of separating and removing a liquid component from the obtained slurry, it is possible to modify the dielectric characteristics during the manufacturing process. In other words, even if the same calcined powder is used, it is possible to control the desired dielectric characteristics simply by changing the grinding conditions. This makes it possible to obtain higher dielectric properties with good reproducibility and at low cost. Further, in the method of the present invention, harmful carbonates that inhibit the sinterability are not mixed in, so that problems such as deterioration of the sinterability do not occur.

[Brief description of drawings]

FIG. 1 is a graph showing changes in the Q value with respect to the elution amount of Ba.

FIG. 2 is a graph showing changes in relative permittivity εr with respect to the elution amount of Ba.

FIG. 3 is a graph showing the relationship of Ba elution amount with respect to grinding time.

Claims (2)

[Claims] 1. A composition having a perovskite structure represented by the general formula ABO ₃ or A _1-x BO _3-x (where x is within a range acceptable as a lattice defect of the perovskite structure,
In the method of crushing and calcining a calcined product (in which alkaline earth metal ions are introduced into A site), the calcined product is crushed in a polar solvent, and the alkaline earth metal ion is selected depending on the crushing conditions at that time. The method for controlling the dielectric properties of a dielectric ceramic composition, comprising: adjusting the amount of elution, removing the liquid content of the resulting slurry by solid-liquid separation, and drying only the solid content for sintering. 2. The method according to claim 1, wherein a calcined product of a composition having Mg, Zn, and Ta introduced at the B site is used.