JPH0692798A - Acicular oxide dielectric particle and its production - Google Patents

Abstract

PURPOSE:To provide the particle having functionability as a deriv. and mechanical characteristics as a reinforcing material of a composite material in combination by heat treating a mixture of raw materials contg. barium, titanium and rare earth element and a flux. CONSTITUTION:The barium, titanium and rare earth element (e.g.; respective oxides) respectively having <=5mum grain sizes are mixed at the compounding ratios expressed by compsn. formula: aBaO.bTiO2.cR2O3 (R is the tervalent rare earth element; (a), (b), (c) are molar ratios, a+b+c=1, 0.1<a<0.2, 0.6<b<0.8, 0.1<c<0.2) and are calcined at 700 to 1400 deg.C. The calcined mixture is melted under heat treating conditions and the flux, for example, the sulfate or chloride of an alkaline metal, which does not induce a selective reaction with the raw materials is added thereto. The amt. of the flux to be added is preferably 25 to 500wt.% based on the value expressed in terms of the oxides of the raw materials. These materials are mixed and are heat-treated at 900 to 1600 deg.C. The flux, etc., are then removed by several N hot hydrochloric acid, etc., and thereafter, the particle is washed, by which the particle having >=3 aspect ratio is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to novel acicular oxide dielectric particles and a method for producing the same. The acicular oxide dielectric particles are promising as a novel functional material capable of imparting mechanical properties and dielectric properties due to the reinforcing effect to various composite materials at the same time because they are acicular and have dielectric properties.

[0002]

2. Description of the Related Art Conventionally, oxide dielectric powder has been used as a powder raw material for composites with a raw material for manufacturing a dielectric porcelain and a resin, but oxide dielectric particles having a needle-like shape are known. Has not been done. In addition, oxides of barium, titanium and rare earth elements such as BaO-TiO ₂ -Nd ₂ O ₃ system {Be
r. Dt. Keram. Ges. 55 (1978) No. 7; JP 60-354
No. 06, etc.} is a dielectric material having a large relative permittivity in the microwave band, a large quality coefficient Q (small dielectric loss), and a temperature coefficient τf of resonance frequency close to 0,
It is particularly important as a communication system using microwaves, that is, satellite communication, communication such as satellite broadcasting, and a resonance element of a broadcasting device.

[0003]

However, the above-mentioned oxide dielectric particles having a needle-like shape have not been known, and their application range has been limited. When the oxide dielectric particles are acicular, not only the effect of imparting the dielectric properties thereof, but also the effect of the reinforcing material can be imparted when used as the raw material of the composite material. Further, since the particle shape is needle-like, it is possible to orient the particles and manufacture a material having anisotropic properties by devising a molding method or the like. The present invention has been made for the purpose of providing new acicular oxide dielectric particles and a method for producing the same.

[0004]

That is, the first aspect of the present invention is a needle-shaped oxide dielectric particle having barium, titanium and a rare earth element as a main component and an aspect ratio of 3 or more. The second invention is a method for producing acicular oxide dielectric particles having an aspect ratio of 3 or more, which comprises heat-treating a mixture of barium, titanium, a rare earth element component-containing raw material and a melting agent.

The present invention will be described in more detail below. The aspect ratio referred to in the first aspect of the invention is the ratio of the major axis of the acicular or columnar particles to the minor axis. Rare earth elements are as usual defined La, Ce, Pr, Nd, Pm, Sm, Eu, G
17 kinds of elements, d, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, Sc, and La, C
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy are useful. The present invention is needle-like dielectric particles containing barium, titanium, and at least one of the rare earth elements as a main component. Other than these main components, additional components include, but are not limited to, Pb, Sr, Ca, Zr, Hf, Bi, Mn, Al, Mg, Si, Ge, T.
One or more kinds of e, Ni, Tl, Sb, Co, Cr and the like may be added, and the addition amount thereof is preferably 25% by weight or less in terms of oxide.

The composition ratio of barium, titanium and rare earth elements in the needle-shaped dielectric particles of the present invention is not particularly limited, but the composition is based on the assumption that the rare earth element is represented by R and has a valence of +3. Formula a ・ BaO ・ b ・ TiO ₂・ c ・ R ₂ O ₃ (where a, b, and c are molar ratios, a + b + c = 1, 0.1 <a <0.2, 0.6 <b <0.8, 0.1 <
The composition range represented by c <0.2) is preferable from the viewpoint of dielectric properties.

Next, the second invention will be described. Raw materials for barium include barium carbonate, oxide, hydroxide, chloride, nitrate, sulfate and oxalate, formate,
Examples thereof include organic acid salts such as acetates, but those that do not remain as impurities after heat treatment are preferable. When the raw material is in powder form, the particle size is preferably small, specifically 5 μm or less, preferably 1 μm or less.

Examples of titanium raw materials include titanium oxides, hydroxides, oxyoxides, chlorides, nitrates, sulfates, oxalates, formates, acetates, organic acid salts such as alkoxides, and metals. However, it is preferable that the oxide becomes an oxide after heat treatment and no impurities remain. When the raw material is in powder form, the particle size thereof is preferably small, specifically 5 μm or less, preferably 1 μm or less.

As a raw material for rare earth elements, oxides of rare earth elements are preferable, and salts such as carbonates are preferable.
Further, depending on the composition of interest, a raw material containing several kinds of rare earth elements such as a light rare earth oxide mixture obtained in the step of refining rare earth elements may be used. Alternatively, a metal may be used as a raw material. In any case, it is preferable that it becomes an oxide after heat treatment and no impurities remain. When the raw material is in powder form, the particle size is preferably fine, specifically 5
Those having a size of not more than μm, preferably not more than 1 μm are suitable.

The raw material of the additive component used when adding the additive component is not particularly limited, but simple substance, alloy, oxide, hydroxide, oxyoxide, chloride, nitrate, sulfate and oxalate, formic acid. Examples thereof include salts, organic salts such as acetates or alkoxides, and complex compounds composed of a mixture thereof and two or more kinds of the above-mentioned additional components, but those which become an oxide after heat treatment and do not leave impurities are preferable. When the raw material is in powder form, the particle size is preferably small, specifically 5 μm or less, preferably 1
It is preferably μm or less.

The barium, titanium or rare earth element component-containing raw material used in the present invention may be a mixture of the above-mentioned component-containing raw materials, but it is preferable that each component is uniformly distributed. Further, it is preferable that at least a part of the constituent elements barium, titanium and rare earth elements form a composite compound and / or a solid solution.

[0012] Each of these components is evenly distributed and barium,
Methods for producing raw materials in which at least a part of titanium and rare earth elements form a complex compound and / or a solid solution are roughly classified into a solid phase method, a liquid phase method, and a vapor phase method, which are described below. However, the solid phase method is preferable in terms of productivity and manufacturing efficiency. The solid phase method is a method in which the raw materials of the above-mentioned constituents are mixed in a powder form and calcined. Mixing may be performed by using a mixer, a ball mill, a vibration mill or the like, which may be dry type or wet type.
The wet type is more efficient. The optimum calcination temperature varies depending on the composition, but is 700 ° C to 1400 ° C, preferably 900 ° C to 1200 ° C. This is because if the calcination temperature is lower than 700 ° C, the solid-phase reaction of the mixed powder is insufficient, and if it exceeds 1400 ° C, strong agglomeration of the powders progresses and the powder becomes coarse and the powder characteristics deteriorate. Specific examples of the calcination method include calcination in an ordinary electric furnace or the like.

The liquid phase method includes, for example, a method of producing from a melt such as a molten metal spray method and a plasma jet method, and a method of producing from a solution by precipitation formation and solvent removal. As the method for forming a precipitate, there are a coprecipitation method, a uniform precipitation method, an alkoxide method, an electrolysis method, a sol-gel method, etc., and a method for removing a solvent is a spray drying method, a freeze drying method, a heat kerosene method, a liquid drying method, an emulsion method. and so on.

The vapor phase method includes an evaporation-condensation method and a vapor phase chemical reaction method. The former is a method in which a raw material is heated to a high temperature by using an arc or a plasma jet to be vaporized, and then rapidly cooled by a large temperature gradient of the arc or the plasma flame to be agglomerated into particles. The latter gas-phase chemical reaction method is based on the chemical reaction of volatile compound vapors, such as thermal decomposition of a single chemical species and reaction between two or more chemical species.

When the above-mentioned additional components are added in addition to barium, titanium and rare earth elements, a single compound of the additional components such as various salts such as oxides and carbonates of these additional components and some additional components. The composite compound consisting of the solid phase method, the liquid phase method, the vapor phase method or the like in the form of a powder or a solution, or barium, titanium, a raw material containing a rare earth element component and a melting agent produced by the above method are used. When mixing, you may add and mix and use. Here, it is preferable to mix barium, titanium, and a rare earth element so as to have the composition ratio described in the description of the second invention.

The melting agent used in the present invention is preferably one that melts under heat treatment conditions and does not cause a selective reaction with barium, titanium and rare earth elements, such as alkali metal sulfates and chlorides. . Specifically, lithium sulfate, sodium sulfate, potassium sulfate, lithium chloride, sodium chloride, potassium chloride and hydrates thereof may be used alone or in combination of two or more. .

If the amount of the melting agent added is small, the growth of the needle-shaped oxide dielectric particles is hindered, and the needle-shaped oxide dielectric particles tend to agglomerate with each other. The production of the dielectric particles is obstructed and the effect is reduced. Therefore, the optimum addition amount differs depending on the target acicular oxide dielectric particle composition and the type of the melting agent used, etc., but with respect to the total oxide equivalent weight of the components that supply barium, titanium and rare earth elements. It is preferably 25 to 500% by weight, more preferably 50 to 300% by weight.

The method of mixing the barium, titanium, rare earth element-containing raw material and the melting agent is not particularly limited as long as they can be uniformly mixed, and a known dry method,
It can be performed by any of the wet methods.
The dry type means mixing by a usual mixing method such as a mortar, a mixer and a ball mill. The wet method is a method of mixing barium, titanium and a rare earth element component-containing raw material and a melting agent in a solution form. When the wet method is used, it is preferable to add a drying step before the heat treatment.

The optimum heat treatment temperature of the mixture of the raw material containing barium, titanium and rare earth element components and the melting agent varies depending on the composition, but is 900 to 1600 ° C., preferably 1100 to
1500 ° C. If the heat treatment temperature is lower than 900 ° C, the acicular oxide dielectric formation reaction is not promoted, and if it exceeds 1600 ° C, an impurity phase is likely to be generated, which is not preferable. For the heat treatment, a metal container such as Pt that can be used at a high temperature, various ceramic containers, or the like can be used. It is preferable that these containers are hard to react with the components for supplying barium, titanium and rare earth elements and the melting agent. It is also possible to suppress the reaction with a container by heat-treating a mixture of barium, titanium, a rare earth element component-containing raw material and a melting agent, which is molded by pressure molding or the like.

In order to isolate the acicular oxide dielectric particles from the reaction product containing the melting agent, hot hydrochloric acid, hot sulfuric acid, hot nitric acid or a mixture thereof, hot caustic soda, hot water or the like of a few normality is used. Then, after removing the melting agent and other water-soluble substances, it is thoroughly washed with water. If there is a water-insoluble by-product, the needle-shaped oxide dielectric particles may be separated from the residue by a treatment such as decantation, and then sufficiently washed with water.

[0021]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. [Examples 1 to 15] BaCO ₃ so as to have the composition shown in Table 1.
Powder (Sakai Chemical Co., Ltd.), TiO ₂ powder (Ishihara Sangyo Co., Ltd.) and rare earth oxide powder (Nihon Yttrium Co., Sm ₂ O ₃ , La ₂ O)
₃ , Nd ₂ O ₃ , Pr ₆ O ₁₁ , and Gd ₂ O ₃ ) were wet-mixed by a ball mill for 20 hours. The resulting mixture slurry was heated and dried. It should be noted that in Table 1, the expression Pr-O means that Pr ₂ O _11/3 , that is, Pr ₆ O ₁₁ is included in order to facilitate comparison with other rare earth raw materials.
The formula weight of 1/3 is assumed to be the Pr raw material. Next, when calcination was performed, it was calcinated in the air at the temperature shown in Table 1 for 2 hours, and the calcined product was crushed by a ball mill for 10 hours. Calcinated powder or mixed powder if not calcined (raw material containing barium, titanium and rare earth elements)
Then, potassium sulfate powder (K ₂ SO ₄ ) as a melting agent was weighed by a ball mill so that the weight% shown in Table 1 was obtained with respect to the total weight of oxides of the components supplying barium, titanium and rare earth elements. Dry mixed for 5 hours. The obtained mixture was heat-treated at the temperature shown in Table 1 for 5 hours. The reaction product was cooled, nitric acid was added and boiled to remove the melting agent, and then washed thoroughly with water and dried.

Table 1 shows the average values of the color, thickness, length and aspect ratio of the obtained acicular oxide dielectric particles. In addition, as a result of examining the crystal structure by X-ray diffraction, it was found that any of the samples had a useful BaR ₂ Ti ₄ O ₁₂ (R
Is a rare earth element) and has a crystal structure.
An electron micrograph (magnification: 4000 times) of the acicular oxide dielectric particles obtained in Example 1 is shown in FIG. Aspect ratio 3
The above particles can be seen. In addition, some of the generated acicular oxide dielectric particles are damaged. This was damaged during the process of preparing the observation sample.

Examples 2 to 13 also had the same shape as that of FIG. 1, although the thickness and length were different. In addition, an electron micrograph (magnification: 10 of the acicular oxide dielectric particles obtained in Example 14).
00 times) is shown in FIG. According to this, it is understood that the form is such that large particles and small particles are mixed. Example 15
Also had the same form as in FIG.

[Example 16] Ba used in Examples 1 to 15
CO ₃ powder, TiO ₂ powder, and light rare earth mixed oxide powder as a rare earth material (Pr ₆ O ₁₁ is 22.6 wt%, Nd ₂ O ₃ is 76.4 wt%,
Sm ₂ O ₃ 0.53 wt%, La ₂ O ₃ 0.37 wt%, Y ₂ O ₃ 0.1
wt%, manufactured by Mitsui Mining & Smelting Co., Ltd.) was weighed so as to have the composition ratio shown in Table 1, and acicular oxide dielectric particles were obtained by the same steps as in Examples 1 to 15 below. Table 1 shows the process conditions and the characteristics of the obtained acicular oxide dielectric particles. In addition, as a result of examining the crystal structure by X-ray diffraction, it was found to be a BaR ₂ Ti ₄ O ₁₂ (R represents a rare earth element) crystal structure useful as a microwave dielectric. The morphology of the needle-shaped oxide dielectric particles obtained by morphological observation with an electron microscope shows the morphology of Example 1.
(Fig. 1).

[Examples 17 to 20] Composition ratio (molar ratio)
_{0.153 · BaO · 0.694 · TiO 2} · 0.153 · Nd 2 O and Bi ₂ O ₃ 15 wt% as a further additive for _three and MnO ₂ 0.1
BaCO ₃ powder, TiO ₂ powder, and Nd ₂ O ₃ powder used in Examples 1 to 15 and commercially available Bi ₂ O so as to have a composition added by weight%.
_{Using 3} powders and MnO ₂ powder, acicular oxide dielectric particles were obtained by the same steps as in Examples 1 to 15 below. Table 1 shows the process conditions and the characteristics of the obtained acicular oxide dielectric particles. Also,
As a result of examining the crystal structure by X-ray diffraction, it was found to be a BaR ₂ Ti ₄ O ₁₂ (R represents a rare earth element) crystal structure useful as a microwave dielectric. In morphological observation with an electron microscope, the morphology of the acicular oxide dielectric particles obtained in Examples 17 to 20 was the same as that in Example 1 (FIG. 1).

[0026]

[Table 1]

[0027]

INDUSTRIAL APPLICABILITY The present invention is a novel acicular oxide dielectric particle and a method for producing the same, which is not heretofore known. The acicular oxide dielectric particle of the present invention has a function as a dielectric and a As a material that also has mechanical properties such as reinforcement,
In addition, it is useful as a raw material for a novel composite material having anisotropic properties and expands an application range that has never been seen before. Further, the acicular oxide dielectric particles containing barium, titanium, and a rare earth element as the main components of the present invention have excellent dielectric properties in the microwave region. Furthermore, according to the method of the present invention, the acicular oxide dielectric particles of the present invention can be efficiently produced.

[Brief description of drawings]

1 is a scanning electron micrograph of acicular oxide dielectric particles obtained in Example 1. FIG.

2 is a scanning electron micrograph of acicular oxide dielectric particles obtained in Example 14. FIG.

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[Procedure amendment]

[Submission date] May 18, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

[0026]

[ Table 1 ] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 29, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG . 1 is a photograph replacing a drawing (showing a grain structure.
2) is a scanning electron micrograph of the acicular oxide dielectric particles obtained in Example 1.

FIG . 2 is a photograph replacing a drawing (showing a particle structure.
Is to) is a scanning electron micrograph of the resulting acicular oxide dielectric particles in Example 14.

Claims (2)

[Claims] 1. An acicular oxide dielectric particle comprising barium, titanium and a rare earth element as a main component and having an aspect ratio of 3 or more. 2. The method for producing acicular oxide dielectric particles according to claim 1, wherein a mixture of barium, titanium, a raw material containing a rare earth element component and a melting agent is heat-treated.