JPH0640725A - Acicular oxide dielectric particles and their production - Google Patents

Abstract

PURPOSE:To provide acicular oxide dielectric particles useful as a material having mechanical characteristics as the reinforcing material of a composite material, etc., besides functional properties as a dielectric and also useful as starting material for a novel composite material having anisotropy in characteristics. CONSTITUTION:The mixture of starting materials contg. a rare earth element and titanium with a flux is heat-treated to produce the objective acicular oxide dielectric particles having >=3 aspect ratio. The oxide contains the rare earth element and titanium as principal components.

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. Since the acicular oxide dielectric particles are acicular in shape, they are promising as a reinforcing material having dielectric properties of various composite materials and as a new functional material having both mechanical properties and dielectric properties. .

[0002]

2. Description of the Related Art Conventionally, oxide dielectric powder has been used as a raw material for manufacturing a dielectric ceramic, a powder raw material for compounding with resin, glass, etc., but needle-shaped powders containing rare earth elements and titanium as main components. No oxide particles are known. Many oxides containing rare earth elements and titanium as main components have excellent dielectric properties in the high frequency and microwave regions, such as Ln ₄ Ti ₉ O ₂₄ , Ln ₂ Ti ₄ O ₁₁ and Ln ₂ Ti. ₃ O _9-x , Ln ₂ Ti ₂ O ₇ ,
Compounds and solid solutions such as LnTiO ₃ and Ln ₂ TiO ₅ (Ln represents a rare earth element) are known. The relative permittivity εr of these substances
, The quality factor Q (the reciprocal of the dielectric loss tan δ) and the temperature coefficient τ f vary greatly depending on the crystal structure and composition, especially the type and composition ratio of rare earth elements, and manufacturing conditions. Selected. For example, regarding the dielectric characteristics of Ln ₂ Ti ₂ O ₇ , the relative permittivity εr is about 35 to 45, and the quality factor Q is
It is known that the temperature coefficient τ f is about 500 to 12000 and the temperature coefficient τ f is about 0 to -120, and it depends on the type and composition ratio of rare earth elements and manufacturing conditions. As for the dielectric properties of Ln ₄ Ti ₉ O ₂₄ , it is known that the relative permittivity εr is about 35 and the temperature coefficient τf is about 0 to +80.

[0003]

However, the above-mentioned needle-shaped oxide dielectric particles have not been known, and their use has not been considered. If the oxide dielectric particles are acicular, when used as a raw material for the composite material,
Not only the effect of imparting the dielectric property but also the effect as a reinforcing material can be imparted at the same time. Further, since the particle shape is needle-like, it is possible to orient the particles by devising a molding method or the like to manufacture a material having anisotropic properties. 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 needle-like oxide particles containing a rare earth element and titanium as main components, and the aspect ratio of the particles is 3 or more. And acicular oxide dielectric particles. 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 a raw material containing a rare earth element and a titanium component 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 particles (or columnar particles in some cases) to the minor axis. Rare earth elements are La, Ce,
Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu
And Y and Sc, which are 17 kinds of elements, depending on the characteristics of the required dielectric material, such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb.
And Dy are useful. The present invention is a needle-shaped dielectric particles containing a rare earth element and titanium as a main component, but is not particularly limited as an additive component other than this main component, Pb, Sr,
Ca, Zr, Hf, Bi, Mn, Al, Mg, Si, Ge, Te, Ni, Tl, S
One or more kinds of b, 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 the rare earth element and titanium in the acicular dielectric particles of the present invention is not particularly limited and is selected according to desired dielectric properties. Specifically, Ln ₄ Ti ₉ O
₂₄ , Ln ₂ Ti ₄ O ₁₁ , Ln ₂ Ti ₃ O _9-x , Ln ₂ Ti ₂ O ₇ , LnTiO ₃ , Ln ₂
Examples thereof include compounds such as TiO ₅ (Ln represents a rare earth element) and solid solutions. Relative permittivity εr and quality factor Q of these substances
Dielectric properties such as (reciprocal of dielectric loss tan δ) and temperature coefficient τ f greatly differ depending on its crystal structure and composition, particularly the type and composition ratio of rare earth elements, manufacturing conditions, etc., and are selected according to the intended use. For example, the dielectric properties of Ln ₂ Ti ₂ O ₇ are as follows: relative permittivity εr is about 35 to 45, quality factor Q is about 500 to 12000, and temperature coefficient τf is about 0 to -120. It depends on the composition ratio and manufacturing conditions. Also, Ln ₄ T
Regarding the dielectric properties of i ₉ O ₂₄ , the relative permittivity εr is about 35, and the temperature coefficient τf is about 0 to +80.

Next, the second invention will be described. As a raw material for rare earth elements, oxides of rare earth elements are preferable,
In addition, 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 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 is preferably small, specifically 5 μm or less, preferably 1 μm or less.

The raw material of the additive component used when adding the additive component is not particularly limited, but is a simple substance, alloy, oxide, hydroxide, oxyoxide, chloride, nitrate, sulfate, oxalate, formate. Examples thereof include organic acid salts such as acetic acid salts and alkoxides, and mixtures thereof, and complex compounds composed of two or more kinds of components, 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.

The raw material containing the rare earth element and the titanium component used in the present invention may be a mixture of the raw materials containing the above respective components, but the respective components are evenly distributed, and at least the rare earth element and titanium are contained. It is preferable that a part thereof forms a complex compound and / or a solid solution. As a method for producing a raw material in which at least a part of these rare earth elements and titanium form a complex compound and / or a solid solution, there are a solid phase method, a liquid phase method such as a coprecipitation method, and a gas phase method. However, the solid phase method is preferable in terms of productivity and production 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 a dry method or a wet method using a mixer, a ball mill, a vibration mill or the like, but the wet method is more efficient. The optimum calcination temperature varies depending on the composition, but it is 700 ℃ ~ 1500 ℃, preferably 900 ℃ ~
It is 1300 ° C. If the calcination temperature is less than 700 ° C, the solid-phase reaction of the mixed powder is insufficient, and if it exceeds 1500 ° C, strong agglomeration of the powders progresses and the powder becomes coarse and the powder characteristics deteriorate.
This is because the mixing characteristics with the melting agent deteriorate. Specific examples of the calcination method include calcination in an ordinary electric furnace or the like.

When the above-mentioned additional components are added in addition to the rare earth element and the titanium component, a single compound of the additional components such as various salts such as oxides and carbonates of these additional components or some of the additional components are used. Is used in the form of powder or solution in the steps of the solid phase method, the liquid phase method, the gas phase method, or the raw material containing the rare earth element and the titanium component produced by the above method is mixed with the melting agent. You may add and mix it when using it. Here, it is preferable to mix the rare earth element and titanium so that the composition ratio is the composition ratio described in the description of the first 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 rare earth elements and titanium components, such as alkali metal sulfates and chlorides and glass phase forming components. Is preferred. Specific examples of alkali metal sulfates and chlorides include lithium sulfate, sodium sulfate, potassium sulfate, lithium chloride, sodium chloride, potassium chloride and hydrates thereof. Further, specific examples of the glass phase forming component include boron compounds, boron oxides, such as boron oxide and oxyacids of boron, such as orthoboric acid (H ₃ BO ₃ ),
Tetraboric acid (H ₂ B ₄ O ₇ ), metaboric acid (HBO ₂ ) or their alkali metal salts such as sodium tetraborate, potassium tetraborate, sodium metaborate and alkoxide compounds of boron such as boron ethoxide (B (OC ₂ H ₅ ) ₃ )
There are known salts such as. These melting agents 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. It becomes complicated and the effect of addition is small. Therefore,
The optimum addition amount varies depending on the composition of the target acicular oxide dielectric particles and the type of melting agent used, etc., but is 25 to 500 relative to the weight of the raw material containing the rare earth element and titanium component in terms of oxide. %, Preferably 50 to 300% by weight.

The method of mixing the raw material containing the rare earth element and the titanium component with the melting agent is not particularly limited as long as it can be uniformly mixed, and any known dry method or wet method can be used. Can also be done. 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 a raw material containing a rare earth element and a titanium component with a melt raw material 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 the rare earth element and the titanium component and the melting agent varies depending on the composition, but is 900 to 1600 ° C., preferably 1000 to 1500.
℃. If the heat treatment temperature is lower than 900 ° C., the reaction of acicular oxide dielectric formation is not promoted, and if it exceeds 1600 ° C., sticking of acicular particles with each other and generation of an impurity phase are likely to occur, which is not preferable. For the heat treatment, a metal container such as Pt that can be used at high temperature or various ceramic containers can be used. It is preferable that these containers are hard to react with a raw material containing a rare earth element and a titanium component or a melting agent. Also,
It is also possible to suppress the reaction with a container by heat-treating a mixture of a raw material containing a rare earth element and a titanium component and a melting agent, which is molded by pressure molding or the like.

When it is necessary to isolate the needle-shaped oxide dielectric particles from the reaction product containing the melting agent, the isolation method includes hot hydrochloric acid, hot sulfuric acid, hot nitric acid or a mixture thereof of about several normals. A method of sufficiently washing with water after removing the melting agent and other water-soluble substances with hot caustic soda, hot water or the like can be mentioned. When the glass phase is by-produced and it is difficult to remove it by the above method, it can be dissolved and removed by hydrothermal treatment with an acid or an alkali. When 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 washed sufficiently with water.

[0018]

EXAMPLES Examples of the present invention will be specifically described below, but the present invention is not limited to these examples. [Examples 1 to 8] Rare earth oxide powders (Nd ₂ O ₃ , Sm ₂ O ₃ manufactured by Japan Yttrium Co., Ltd.) and TiO ₂ powders (manufactured by Ishihara Sangyo Co., Ltd.) having a composition shown in Table 1 were ball milled. Wet mixed for 20 hours. The resulting mixture slurry was heated and dried. 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. If the calcination powder or the calcination powder is not used, the melting agent shown in Table 1 is added to the mixed powder (raw material containing rare earth element and titanium component) to obtain the raw material containing rare earth element and titanium component in terms of oxide. It was weighed so that the weight% shown in Table 1 was based on the total weight, and dry-mixed for 5 hours by a ball mill. The obtained mixture was heat-treated at the temperature shown in Table 1 for 5 hours. The reaction product was cooled, added with an acid and boiled to remove the melting agent, and then thoroughly washed with water and dried. The color, thickness, length and aspect ratio of the obtained acicular oxide dielectric particles are shown in Table 1. Table 1 shows the results of examining the crystal structure by X-ray diffraction.

[0019]

[Table 1]

[0020]

According to the present invention, it is possible to easily obtain novel acicular oxide dielectric particles which have never been obtained. The acicular oxide dielectric particles of the present invention are used as a material having not only functionality as a dielectric but also mechanical properties as a reinforcing material of a composite material, and a novel composite material having anisotropic properties. It is useful as a raw material and is expected to have a wide variety of uses.

[Procedure amendment]

[Submission date] September 22, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019]

[Table 1]

Claims (2)

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