JPH0369511A - Fibrous dielectric and its production - Google Patents

Abstract

PURPOSE:To obtain the fibrous dielectric with its permittivity controllable to a desired value by mixing one kind among a hydrated titanium dioxide fiber and an anatase or rutile-type titanium oxide fiber and barium hydroxide in a specified ratio and subjecting the mixture to a reaction under hydrothermal conditions. CONSTITUTION:(A) One kind selected from the hydrated titanium dioxide fiber, anatase-type titanium oxide fiber and rutile-type titanium oxide fiber and (B) barium hydroxide are mixed. The mixing weight ratio of the BaO contained in the B component to the TiO2 contained in the A component is appropriately controlled to 0.2-1.5. The mixture is subjected to a reaction preferably at >=100 deg.C under hydrothermal conditions. Consequently, a dielectric in which globular crystallizes of barium titanate are bound in the fibrous state is obtained. The value for permittivity can be widely controlled to 100-1600 by selecting the mixing ratio of the A component to B component.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fibrous dielectric used as a dielectric material and a method for producing the same, and in particular, the invention relates to a fibrous dielectric used as a dielectric material and a method for manufacturing the same. The present invention relates to a dielectric material that can be used as a dielectric material and a method for manufacturing the same.

<Prior Art> Barium titanate is widely used as a material for dielectrics, semiconductors, and piezoelectrics, and is also industrially produced in large quantities. Recently, several studies have been conducted on the production of fibrous barium titanate with oriented crystal axes for application to grain-oriented ceramics and the like.

For example, in Japanese Patent Publication No. 62-55243, K2O・n
A solid material that produces barium titanate with oriented particles by mixing potassium titanate fibers represented by T i O2 and barium oxide or a barium compound that decomposes at high temperatures to become barium oxide, and then firing the mixture. A mutual law has been disclosed.

For example, in Japanese Patent Application Laid-Open No. 63-260822, Ti
Titanium oxide fiber represented by O2゜n H□0 and BaO・
Excess barium compound and NaCl-KC as TiO2
A flux property is disclosed in which polycrystalline fibrous barium titanate is produced by mixing l-based flux, spray drying, and then firing.

Furthermore, for example, in Japanese Patent Publication No. 62-7160, 20-x
A hydrothermal method is disclosed in which potassium titanate hydrate represented by TiO2.yH20 and barium hydroxide are reacted under hydrothermal conditions to produce fibrous barium titanate.

<Problems to be solved by the invention> However, in previous reports, potassium titanate is used as a raw material or alkali metal salts such as sodium chloride or potassium chloride are used as fluxes, so depending on the processing conditions, sodium or potassium may be added to the product. In some cases, it may contain. When electronic devices are manufactured using barium titanate containing elements such as sodium and potassium, their characteristics deteriorate significantly, and in some cases, other devices may also be adversely affected.

In addition, when performing a solid phase reaction, it is necessary to perform sufficient mixing, so wet mixing is usually performed using hard balls in a pot such as Alx, and during this mixing, the fiber shape of the raw materials is damaged. There are some drawbacks. On the other hand, if sufficient mixing is not performed, a uniform reaction cannot be carried out. Even in the fluffx method, if the amount of fluffx is small, it is difficult to obtain a uniform reaction, and if the amount is large, the reaction time becomes long.

In the solid phase/flux type, the reaction temperature is relatively high <Ba
When the mixing ratio of O and TiO2 deviates from 1=1, B a T
By-products such as i z○7 and Ba 2T i O4 are produced. Even in the hydrothermal reaction using potassium titanate hydrate, potassium tetratitanate and potassium hexatitanate are produced as by-products, which poses a problem when used as electronic materials.

<Means for Solving the Problems> The method for producing a fibrous dielectric of the present invention includes titanium dioxide hydrate fibers TiQ2.nH2O, anatase type titanium oxide fibers, and rutile type titanium oxide fibers (these are called titania fibers). and barium hydroxide at a mixing ratio, and then reacted under hydrothermal conditions.

The general structure of the fibrous dielectric of the present invention manufactured in this way is TiOx-BaT, in which spherical barium titanate is attached to the surface of titanium dioxide fibers by 20% or more of the total weight.
It is an iO2-based fibrous dielectric.

In this structure, when the adhesion rate of spherical halium titanate 1 increases, a dielectric material is formed in which spherical microcrystalline particles of barium titanate are bonded in the form of fibers.

The titania hydrate fiber used in the present invention is produced by treating potassium titanate with an acid, the anatase fiber by hydrothermally treating it in an acid solution, and the rutile fiber by treating the titania hydrate fiber at 1000'C or more. Each can be obtained by heat treatment.

The titania fibers, barium hydroxide, and water are placed in a reaction vessel in predetermined amounts and reacted at a temperature of 100° C. or higher. The higher the reaction temperature, the shorter the processing time, but problems such as corrosion and pressure make it difficult to select the material and structure of the container, making it less economical.
The temperature should be below 00°C. The time for 100% reaction is 10 hours at 200°C and within 1 hour at 500°C. If the reaction temperature is 100° C. or lower, not only will the time required for the reaction become longer, but it will also be difficult to achieve 100% reaction.

This reaction is considered to be a dissolution-precipitation reaction, and the eluted TiO2
and barium in the solution combine to form fine spherical barium titanate and precipitate on the chikunia fibers. Since the precipitation surface is a crystal, its crystal axis is oriented, and it is thought to be similar to the generation mechanism of epitaxial thin films using crystals as substrates.

The resulting product is made of fine spherical barium titanate with its crystal axis oriented and bonded into fibers, making it possible to create devices that utilize dielectric and piezoelectric anisotropy.
When the mixing ratio (Ba○/T i Oz) (hereinafter abbreviated as BT ratio) of the raw materials is made small, a fiber having a form in which spherical barium titanate is deposited on the surface of the titanium dioxide fiber is produced. The base material of this fiber is single crystal fiber (whisker)
It is.

When the mixing ratio (BT ratio) of raw materials exceeds 1.0, fiber destruction becomes severe, and when it exceeds 1.5, the fiber structure can no longer be maintained. Further, when the BT ratio is less than 0.2, the dielectric constant value is no different from that of ordinary titanium oxide.

<Operation> As shown in the characteristic diagram in FIG. 3, by changing the BT ratio, products with dielectric constant values in the range of 100 to 1600 can be obtained.

The products of the invention are also fibrous and have a high tensile strength, making them suitable for reinforced plastic composites.

<Example> Potassium tetraticunate, represented by 0.4TiO□, was applied to the top of the twisted wire by a flux method. That is, predetermined amounts of titanium dioxide, potassium carbonate, and potassium molybdate are prepared and heated in a platinum crucible to 1) 00°C, then cooled to 850°C at a rate of 5°C/hour, and then the le cibo is removed from the furnace. It was then allowed to reach room temperature in the atmosphere. Subsequently, the product was washed with water to separate the flafukus to obtain potassium tetraticunate.

Next, potassium was eluted from the obtained potassium tetratitanate with 5N (normal) hydrochloric acid to produce a titanium dioxide permanent fiber represented by 4TiO2.2H20.

The potassium content of this fiber was 5 pHm or less as measured by atomic absorption spectrometry.

10 g of titanium dioxide permanent fiber thus obtained and barium hydroxide octahydrate (B a (○H)z ・81-120
) amount to give a BT ratio of 1.0 35.5g ・35cc of pure water
was placed in a reaction vessel and sealed. The filling rate at this time is ':
'J 80%. Next, the reaction vessel was placed in an electric furnace and a reaction was carried out at a temperature of 200° C. for 10 hours. The obtained product showed a diffraction peak of only barium titanate when measured by powder X-ray diffraction, and when observed using an electron microscope, it had a fibrous shape consisting of a collection of fine spherical crystal particles, as shown in Figure 1. was. Electron diffraction measurements confirmed that the crystal axes were oriented.

Actual L ink: 42 mm 23 mm Titanium dioxide elongated fiber produced in the same manner as in Example 1 was heated in a 50% acetic acid (CH3CO○H) solution at a temperature of 20 mL.
Hydrothermal treatment was performed at 0° C. for 10 hours to obtain anatase type titanium dioxide fibers.

Anatase titanium dioxide 10g/barium hydroxide 8
39.5g amount of water salt with BT ratio of 1.0, 85cc of pure water
was placed in a reaction vessel, sealed, and placed in an electric furnace.

Next, a reaction was carried out at a temperature of 200°C for 10 hours, and Example 1
A similar evaluation was conducted. The product, as shown in FIG. 2, was a barium titanate fiber consisting of spherical particles with oriented crystal axes.

The length is also an example 1 Titanium dioxide permanent fibers produced in the same manner as in Example 1 were placed in an alumina crucible and heated to a temperature of 1200' in an electric furnace.
A heat treatment was performed at C for 2 hours to obtain a rutile-type titanium oxide fiber.

10 g of titanium dioxide, 39.5 g of barium hydroxide octahydrate in an amount that would give a BT ratio of 1.0, and 85 cc of pure water were placed in a reaction vessel, sealed, and placed in an electric furnace. Next, a reaction was performed at a temperature of 200° C. for 10 hours, and the same evaluation as in Example 1 was performed. When the product was observed under an electron microscope, it was found to be barium titanate fibers consisting of spherical particles with oriented crystal axes, very similar to the product of Example 2.

10 g of titanium dioxide permanent fiber produced in the same manner as in Example 1, 17.75 g of barium hydroxide octahydrate with a BT ratio of 0.5, and 85 cc of pure water were placed in a reaction vessel and sealed. , and put it into an electric furnace. Next, a reaction was carried out at a temperature of 200'C for 7 hours, and the same evaluation as in Example 1 was carried out.

When the product was observed under an electron microscope, it was found that it was very similar to the product of Example 2, and had a structure in which spherical barium titanate particles were attached to titanium dioxide fibers.

The product obtained in Example 4 was crushed in a mortar, placed in a mold of 15 mm, pressed at a pressure of 1000 kg/ci, and then sintered at 1200°C to a thickness of about 1 inch. A disk-shaped sample was prepared. When electrodes were formed on both main surfaces of this sample using silver paste and the dielectric constant was measured, it was found to be 353.

<Effects of the Invention> 0 According to the present invention, a novel dielectric material whose dielectric constant value can be arbitrarily selected over a wide range of 100 to 1600 can be obtained. Furthermore, it does not contain elements harmful to semiconductor manufacturing such as potassium and sodium, and although the fibers are fine with a diameter of 3 μm or less, they have strong tensile strength, so they can be applied to a wide range of applications, such as EI1 display elements. Suitable for insulating layer materials, etc.

[Brief explanation of drawings]

FIG. 1 is a micrograph showing the microstructure of the product obtained according to Example 1 of the present invention. FIG. 2 is a micrograph showing the microstructure of the product obtained according to Example 2 of the present invention. FIG. 3 is a characteristic diagram showing the relationship between the raw material ratio and dielectric constant of the product of the present invention.

Claims (6)

[Claims] (1) A dielectric material made of spherical microcrystalline particles of barium titanate bonded together in the form of fibers. (2) TiO_2-Ba, in which spherical barium titanate is attached to the surface of titanium dioxide fiber by 20% or more of the total weight
TiO_3-based fibrous dielectric. (3) The fibrous dielectric material according to claim (1) or (2), wherein the fiber diameter is 0.2 to 3 μm and the length is 10 times or more the fiber diameter. (4) Titanium dioxide hydrate fiber TiO_2・nH_2
A method for producing a fibrous dielectric material, which comprises mixing barium hydroxide with O, anatase-type titanium oxide fiber, or rutile-type titanium oxide fiber at a mixing ratio k, and then reacting the mixture under hydrothermal conditions. (5) The above mixing ratio k is B contained in each raw material.
The method for producing a fibrous dielectric according to claim 4, wherein the ratio of (BaO/TiO_2) in terms of the amounts of aO and TiO_2 is in the range of 0.2 to 1.5. (6) The method for producing a fibrous dielectric according to claim (4), wherein the reaction temperature is 100°C or higher.