JPH0524862B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing plate-like particles of metal titanate, and more specifically, the present invention relates to a method for producing plate-shaped particles of metal titanate, and more specifically, a method for producing plate-like particles of metal titanate, which allows easy production of molded metal titanate with crystal axes aligned in the same direction. This invention relates to a method for producing plate-like particles of metal salt. The plate-shaped particles of the metal titanate produced according to the present invention can be used as a material for producing elements in which the crystal axes are aligned in the axial direction, and have the advantage that the elements can be easily produced. have [Technical Background and Description of Prior Art] Perovskite compounds, especially sintered bodies of titanium-containing perovskite compounds based on barium titanate, lead titanate, or lead titanate-zirconate, have piezoelectric, dielectric, and pyroelectric properties. It is widely used as an applied part. Among these materials, materials whose crystal axes are aligned in a certain direction are expected to have high performance, and so far a method for manufacturing barium titanate sintered bodies with oriented crystal axes has been proposed. has been done. One method involves molding a mixture of anatase-type titanium dioxide acicular particle powder that extends in the a-axis direction and barium oxide to create a compact in which the elongation direction of the acicular particles is aligned in the same direction, and then sintering this. Another method is to pressurize fibrous barium titanate from a fixed direction in the presence of an aqueous polyvinyl alcohol solution in a mold to form barium titanate. A method of making a molded body with fiber orientation and sintering it (patent application 1983)
-83629), and the other method involves mixing metal titanate fibers with a resin that is compatible with the fibers, extruding the mixture through pores to shape it, and sintering the molded product. Method (Patent Application No. 61-50522)
However, in these conventional methods, when producing a sintered body of metal titanate, various methods are used to orient the fiber direction of the metal titanate fibers in a fixed direction in the molded product of metal titanate. We are innovating and devising new ideas. Further, in these conventional methods, metal titanate fibers are produced by a hydrothermal synthesis reaction between potassium titanate fibers and a metal hydroxide such as barium hydroxide or lead hydroxide. In the production of potassium titanate fibers, barium hexatitanate and potassium tetratitanate were previously used; however, potassium dititanate is produced by separating potassium dititanate fibers when its molten solid is hydrated. It has been found that [Yoshiki Fujiki et al.: Journal of the Ceramic Industry Association Vol. 90, No. 1, pp. 19-22 (1982)] The present inventors have been conducting research on barium titanate for many years, and in this research, When potassium fibers are wet-milled in ethanol, the potassium dititanate fibers are further separated into layers in the direction of the fiber axis and separated into plate-like particles of potassium dititanate. Even if the titanate metal salts such as barium titanate or lead titanate are made by a hydrothermal method, these metal titanate salts can be made by simply placing them in a mold and applying pressure from one direction. When a molded body with oriented crystal axes is made and this molded body is sintered, a sintered body with crystal axes oriented in a certain direction and a regular crystal structure close to that of a single crystal is produced. The present invention was achieved based on these findings. [Object of the Invention and Summary of the Invention] An object of the present invention is to provide a novel method for producing plate-like particles of metal titanate.
The object of the present invention is to provide a method for producing novel plate-like particles of metal titanate, which allows easy production of compacts and sintered bodies of metal titanate with excellent electrical properties. It is an object of the present invention to provide a novel method for producing plate-shaped particles of metal titanate, which allows molded bodies and sintered bodies in which the axial direction of the crystal axis of the metal salt is oriented to be easily produced with little labor. The present invention wet-pulverizes fibrous potassium dititanate in the presence of ethanol to split the fibrous potassium dititanate into layers in a direction parallel to the direction of the fibers of the fibrous potassium dititanate. A plate-shaped metal titanate salt, characterized in that plate-shaped particles of potassium dititanate are produced, and plate-shaped particles of a metal titanate are produced by reacting the plate-shaped particles of potassium dititanate with a metal hydroxide. This is a method for producing particles. In the production of plate-like particles of metal titanate of the present invention, the fibrous potassium dititanate starting material is prepared by rapidly cooling a molten lump of potassium dititanate from one direction, parallel to the cooling direction. The crystals of fibrous potassium dititanate grow in the direction of , forming an arrayed mass, and the fibrous potassium dititanate crystals are hydrated to form a fibrous potassium dititanate crystal. You can use what is created by releasing the . The plate-shaped particles of metal titanate produced according to the present invention are further wet-pulverized in the presence of ethanol to more completely cleave the plate-shaped particles of metal titanate. You can also do it. The metal titanate salt made according to the present invention can be barium titanate or lead titanate. [Detailed Description of the Invention] In the production of plate-like particles of metal titanate of the present invention, potassium dititanate fibers are produced by melting a mixture of K ₂ CO ₃ and TiO ₂ at a stoichiometric ratio at 1100°C. Although it can be produced by a cooling melt method, it is preferable to rapidly cool the molten reaction product in one direction to impart directionality to its crystallization. Since the potassium dititanate fibers are oriented in the direction of crystallization due to cooling, it is thought that the potassium dititanate fibers are formed as the crystallization region advances due to cooling of the molten reaction product. The quenching of the reaction product in the molten state is performed by adding K ₂ CO ₃ and
A method in which the reaction product in a molten state of TiO ₂ is poured into a flat-bottomed container and the bottom is rapidly cooled from below; A method in which the reaction product in a molten state is poured into a flat-bottomed container whose bottom is being cooled and rapidly cooled; Alternatively, the reaction of K ₂ CO ₃ and TiO ₂ in a molten state may be carried out in a flat-bottomed reaction vessel, and after the reaction, the bottom of the flat-bottomed reaction vessel may be rapidly cooled from below, but any method may be used. Even so, it is necessary to increase the cooling rate so that the crystallized region of the reaction product melt due to cooling moves linearly upward from the bottom surface being cooled. By crystallization on cooling of the melt of the reaction product,
It is thought that the potassium dititanate fibers are formed by stretching in the direction of crystallization. The product solidified and crystallized by cooling is a solidified lump of potassium dititanate fibers that have not been loosened, but when this lump is immersed in water and stirred, dititanic acid Potassium fibers break loose from the bulk fiber aggregate, separate, and settle to the bottom of the water. It is believed that this is because some potassium ions are eluted from the melt-solidified phase of potassium dititanate to form a swellable hydrated phase, which causes the potassium dititanate fibers to separate. [Yoshiki Fujiki et al. “Hydration and derivatives of potassium dititanate fibers”: Journal of the Ceramics Association, Vol. 90, No. 1
Pages 19-23 (1982)] Potassium dititanate fibers that have settled to the bottom of the water are collected and wet-pulverized in ethanol. Wet grinding is carried out by grinding the potassium dititanate fibers with a pestle in a mortar containing ethanol, or by a similar known method, whereby the potassium dititanate fibers are split into layers in the length direction of the fibers. As a result, plate-like particles of potassium dititanate are obtained. In the present invention, plate-shaped particles of potassium dititanate are placed in a sealed pressure vessel together with metal hydroxide powder and water, and the container is heated to produce plate-shaped particles of metal titanate. For example, when making plate-like particles of barium titanate, barium hydroxide is used as the metal hydroxide, and when making plate-like particles of lead titanate, lead hydroxide or basic lead acetate is used. When producing lead titanate, plate-shaped particles of potassium dititanate are immersed in dilute hydrochloric acid prior to the reaction to extract potassium ions from the plate-shaped particles of potassium dititanate. is placed in a pressure vessel with lead hydroxide or basic lead acetate and water and heated to produce plate-like particles of lead titanate. If the plate-shaped particles of the metal titanate obtained in this way are aggregated to form a lump, the lump is wet-pulverized again in ethanol to form the metal titanate without any agglomerates. Platy-shaped particles of salt can be obtained. The plate-like particles of metal titanate obtained by the present invention can be formed and then sintered to produce a piezoelectric porcelain material by simply applying pressure from one direction during the forming process. Since it is possible to obtain a molded product in which the grain direction is oriented, there is an advantage that the production of the oriented piezoelectric ceramic material is simple and easy. The present invention will be explained in more detail below with reference to Examples and Test Examples. Example 1 (Preparation of plate-like particles of potassium titanate) Titanium dioxide (TiO ₂ , manufactured by Kojundo Kagaku Co., Ltd., purity
15.0 g (0.19 mol) of powder of 99.9% reagent) was mixed with 12.97 g (0.094 mol) of potassium carbonate (K ₂ CO ₃ , manufactured by Shuzui Hikotaro Shoten, special grade reagent). The powder mixture was placed in a 100ml platinum crucible, the platinum crucible was placed in an electric furnace (manufactured by Chiyoda Ceramics), and heated at 1100°C for 30 minutes to melt the powder mixture, and then the platinum crucible was taken out of the electric furnace.
The platinum crucible was immediately placed on a copper plate whose bottom surface was cooled with running water, and the molten reaction mixture was cooled from the bottom of the platinum crucible to solidify and form potassium dititanate (K ₂ O.2TiO ₂ ). A lump was obtained.
Add this lump of potassium dititanate to 1 part water and 6 parts water.
After soaking for a period of time, a bar of potassium dititanate was obtained. Place this stick of potassium dititanate in an agate mortar, add 20 ml of ethanol, and wet-mill for 10 minutes to obtain potassium dititanate (K ₂ O.
2TiO ₂ .2H ₂ O) plate-like particles were obtained. (Preparation of plate-like particles of barium titanate) Platy-like particles of potassium titanate obtained above 10
g and 15.01 g of barium hydroxide [Ba(OH) _{2.8H 2 O} manufactured by Morizui Hikotaro Shoten, special grade reagent] were placed in a polyethylene bottle, and after shaking the polyethylene bottle to mix thoroughly,
The mixture was placed in a silver disc-shaped reaction vessel [42 mm (diameter) x 150 mm (height)] together with 120 c.c. of water, and this reaction vessel was placed in an autoclave and reacted at 150°C for 10 hours. Thereafter, the reaction product in the form of a cake was taken out, washed with water until the washing liquid became neutral, and dried at a temperature of 80° C. for 24 hours. This cake-like reaction product was classified with a 420 μm sieve,
The reaction product on the sieve was placed in an agate mortar, 20 ml of ethanol was added thereto, wet pulverized for 5 minutes, and then dried to obtain 12.4 g of barium titanate plate-like particles. Example 2 (Preparation of plate-like particles of lead titanate) Platy-like particles of potassium titanate obtained in Example 1 10
titanium dioxide (TiO ₂ 2H ₂ O) and basic lead acetate [Pb (CH ₃ COO) ₂・Pb (OH) ₂ , manufactured by Shuzui Hikotaro Shoten. , Reagent Special Grade] 48.87 g into a polyethylene bottle, mix thoroughly, and then add the mixture with 120 c.c. of water.
Place it in a disc-shaped reaction vessel [46 mm (diameter) x 150 mm (height)] made of stainless steel coated with Teflon, and place this reaction vessel in an autoclave for 300 min.
The reaction was carried out for 1 hour at a temperature of .degree. Thereafter, the reaction product in the form of a cake was taken out, washed with water until the washing liquid became neutral, and dried at a temperature of 80° C. for 24 hours. This cake-like reaction product was classified using a 420 μm sieve, and the reaction product on the sieve was placed in an agate mortar, 20 ml of ethanol was added thereto, wet pulverized for 5 minutes, and then dried to form a plate of lead titanate. 39.8 g of particles were obtained. Test Example (Orientation of crystal axis of sintered body) (1) Preparation of sample (1-1) Barium titanate sintered body Approximately 3 g of barium titanate plate-like particles obtained in Example 1 were placed in a mold [15 mm ( diameter) x 30 mm (height)] and pressurized under a pressure of 66.4 Pa to form the product.The molded product was then placed in an electric furnace and heated at 1350°C for 50 minutes.
After firing for a period of time, a barium titanate sintered body was obtained. (1-2) Lead titanate sintered body 0.032 g of manganese dioxide (MnO ₂ , manufactured by Kojundo Kagaku Co., Ltd., 99.9% reagent) was added as a sintering aid to 10 g of the lead titanate plate-shaped particles obtained in Example 2. and lanthanum oxide (La ₂ O ₃ , manufactured by Kojundo Kagaku Co., Ltd., 99.9%
Add 0.193g of reagent) and add the remaining amount of titanium oxide (TiO ₂ , manufactured by Kojundo Kagaku Co., Ltd., 99.9% reagent)
Add 0.293 g and mix well in a mortar with 20 ml of ethanol. Put about 3g of this mixture into a mold [15mm (diameter) x 30mm (height)],
After pressurizing and molding under a pressure of 66.4 Pa, the molded product was placed in an electric furnace and fired at a temperature of 1280° C. for 5 hours to obtain a sintered body of lead titanate. This sintered body is 0.99 [0.90 (PbO・TiO ₂ ) + 0.1/
It had a stoichiometric composition of 3(La ₂ O ₃ .3TiO ₂ )]+0.01MnO ₂ . (2) Measurement of crystal axis orientation of sintered bodies (2-1) Measurement of X-ray diffraction patterns Samples of barium titanate sintered bodies and lead titanate sintered bodies, and sintering of these sintered bodies Regarding the sample of the molded product before treatment, the surface parallel to the axis on which the molded product was pressed was irradiated with X-rays, and the X-ray diffraction pattern was measured. (2-2) Measurement of the orientation index of crystal axes From the X-ray diffraction patterns of samples of barium titanate sintered bodies and lead titanate sintered bodies, X-ray diffraction lines representing the respective peak intensities are drawn,
An X-ray diffraction diagram of the barium titanate sintered body shown in FIG. 3 and an X-ray diffraction diagram of the lead titanate sintered body shown in FIG. 4 were drawn. In the X-ray diffraction diagrams of FIGS. 3 and 4,
Diffraction line of a-axis (hOO) with respect to the direction of X-ray irradiation
The c-axis diffraction line is expressed as (OOl), and for each sample, the sum of integrated intensities of all diffraction lines: ( _hOO ) plane (a-axis) and (OOl) plane (c Total sum of diffraction lines of axis): Σ(I _hOO +
Let the ratio of I _OOl ) be P, that is, P = Σ(I _hOO + I _OOl )/Σ(I _hkl ), and the ratio of that for a sample whose crystal axes are not oriented is
Calculate the orientation index (P/P ₀ ) of the ( _hOO ) plane (a- _axis ) and (OOl) plane (c-axis) as P 0 , that is, P ₀ = Σ( _{I hOO} + I OOl )/Σ(I hkl ) did. The P ₀ of barium titanate and lead titanate samples whose crystal axes are not oriented is 5 on the JCPDS card.
−0626 (TiBaO ₃ , Tetragonal) and 6-0452
(TiPbO ₃ , Tetragonal). (3) Results (3-1) X-ray diffraction pattern The X-ray diffraction pattern of the barium titanate sintered body is shown in Figure 1, and Figure 1 a shows the control barium titanate before sintering. X of the molded product
This is a ray diffraction pattern, and FIG. 1b is an X-ray diffraction pattern of a barium titanate sintered body. The X-ray diffraction pattern of the sintered body of lead titanate is as shown in Figure 2, and Figure 2a is the X-ray diffraction pattern of the control molded body of lead titanate before sintering. b is an X-ray diffraction pattern of the lead titanate sintered body. (3-2) Orientation index of crystal axis (P/P ₀ ) It was as shown in Table 1.

〔Effect of the invention〕

In the production of piezoelectric sintered ceramic material of metal titanate, a molded body with oriented crystal axes can be produced by a simple process of applying pressure from one direction.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the X-ray diffraction pattern of the molded body of barium titanate plate-like particles of Example 1, and a is a diagram showing the X-ray diffraction pattern of the molded body before firing; And b is a chart showing the X-ray diffraction pattern of the sintered body after firing. Second
The figure is a chart showing the X-ray diffraction pattern of the molded body of lead titanate plate-like particles of Example 2, in which a is a chart showing the X-ray diffraction pattern of the molded body before firing, and b is a chart showing the X-ray diffraction pattern of the molded body before firing. It is a chart showing the X-ray diffraction pattern of the sintered body after firing. FIG. 3 is a diffraction diagram showing the peak intensity of X-ray diffraction of the barium titanate sintered body, and FIG. 4 is a diffraction diagram showing the peak intensity of X-ray diffraction of the lead titanate sintered body.

Claims (1)

[Claims] 1. Wet-milling potassium dititanate fibers in the presence of ethanol to produce plate-like particles of potassium dititanate, and combining the plate-like particles of potassium dititanate with a metal hydroxide. 1. A method for producing plate-like particles of metal titanate, which comprises reacting and thereby producing plate-like particles of metal titanate. 2. That the potassium dititanate fibers are produced by rapidly cooling a melt of potassium dititanate to form a lump, and by hydrating the potassium dititanate lump. A method for producing plate-like particles of metal titanate according to claim 1. 3. Platy particles of metal titanate are obtained by wet-pulverizing plate-shaped particles of metal titanate produced by the reaction of potassium dititanate and metal hydroxide in the presence of ethanol. A method for producing plate-like particles of metal titanate according to claim 1 or 2, characterized in that: 4. The metal in the metal titanate is barium, and the metal in the metal hydroxide is
The method for producing plate-like particles of metal titanate according to any one of claims 1 to 3, wherein the particles are barium. 5. The titanic acid according to any one of claims 1 to 3, wherein the metal in the titanate metal salt is lead, and the metal in the metal hydroxide is lead. Method for producing plate-like particles of metal salt.