JPS623004A - Production of easily sintering perovskite raw material powder by wet method - Google Patents

Abstract

PURPOSE:To produce perovskite raw material powder having readily sintering properties, uniformity and high bulk density, by forming gradually precipitate of each component of perovskite from a solution, washing and filtering the precipitate by a filter press and calcining the precipitate. CONSTITUTION:In perovskite shown by a general formula ABO3 (A; one or more metallic elements of oxygen 12 coordination, B; one or more metallic elements of oxygen 6 coordination), precipitate of the component A is formed from an aqueous solution of a compound such as hydroxide, carbonate, etc., of the component A such as Pb, Ba, Ca, etc., and a precipitate forming solution of NH3, etc. Then, the above-mentioned reaction solution is blended with an aqueous solution of a compound of the component B such as Ti, Zr, Mg, etc., to form precipitate of the component B. Then, the precipitate is washed and filtered and washed by a rotary filter press, further emulsified and dried. Then, the dried material is calcined at 400-1,000 deg.C, to give easily sintering raw material powder of perovskite type structure and its solid solution at low cost and efficiently.

Description

[Detailed Description of the Invention] [Industrial Application Field] Compounds with a perovskite structure (hereinafter referred to as perovskites) and their solid solutions are widely used as functional ceramics such as piezoelectric materials, optoelectronic materials, dielectric materials, semiconductors, and sensors. It is used for. Recently, the sophistication of functional ceramics has progressed, and raw material powders of perovskite and its solid solution that meet the demands for easy sintering, uniformity, high bulk density, and low cost can be produced efficiently in large quantities. Development of technology is required.

[Prior art and problems]

Conventionally, dry methods and wet methods are known as methods for producing raw material powders of perovskites and solid solutions thereof.

The dry method involves dry mixing the raw material components.

This is a method of calcining it. However, with this method, it is difficult to obtain a raw material powder with a uniform composition, it is difficult to obtain a perovskite and its solid solution with excellent functionality, and the sinterability is not sufficient.

The wet method is a method in which a mixed solution of all the constituent components is prepared, a precipitate-forming liquid such as an alkali is added to this to cause coprecipitation, and this coprecipitate is dried and calcined (hereinafter referred to as the coprecipitation method). be.

According to this coprecipitation method, it is easy to obtain powder with excellent uniformity, but
Particles coagulate during precipitate formation or drying to form secondary particles, which has the disadvantage of being difficult to sinter.

Furthermore, in the coprecipitation method, the precipitate forming ability of each component is not constant; for example, the acid component forms 100% precipitate.

There are cases where all other components cannot form a precipitate.

It may be difficult to achieve the desired composition.

Furthermore, perovskites and their solid solutions often contain both lead and titanium. When producing such materials industrially, it is desirable to use inexpensive titanium tetrachloride as the titanium raw material.

However, when this is used in a coprecipitation method, the chlorine ions in titanium tetrachloride react with lead ions to produce a white precipitate, making it difficult to use. In this case, the formation of this white precipitate can be prevented by using titanium oxynitrate [Ti0(,N03)2] instead of titanium tetrachloride, but titanium oxynitrate is expensive, so it is not suitable for industrial production. Not practical.

Further, in the coprecipitation method, the particles of the precipitate (coprecipitate) are very small, and it takes a long time to remove impurities from the precipitate by washing and passing through four mouths. Furthermore, the natural sedimentation method has problems such as the composition and shape of the precipitate becoming non-uniform during separation of the precipitate and liquid.

[Purpose of the invention]

The present invention provides a method that can eliminate the drawbacks of conventional coprecipitation methods, and furthermore, a method for producing perovskites and their solid solutions that satisfy the four requirements of easy sinterability, uniformity, low cost, and high bulk density. An object of the present invention is to provide a method that can efficiently produce raw material powder.

[Structure of the invention]

As a result of intensive research to achieve the above object, the present inventors found the general formula ABO3 (where A is 1 of the oxygen 12-coordinated metal element).
species or 2s or more, and B represents one or more oxygen hexacoordination metal elements. ) When producing the raw material powder of perovskite and its solid solution shown in (), a precipitate of component A is generated using an aqueous solution of the component A compound and a precipitation forming liquid, and then an aqueous solution of the component B compound is added to generate a precipitate of component B. Alternatively, the order of forming the precipitates of component A and component B may be changed from the above to produce precipitates, and the resulting precipitate may be separated from the mother liquor, dried, and then calcined at a temperature of 400°C or higher. It has been found that by producing a raw material powder using the method, the drawbacks of the conventional coprecipitation method can be overcome by #1. Further, when the precipitate is separated from the mother liquor and dried, the precipitate is washed and filtered using a rotary filter press, and then subjected to emulsification treatment.

After drying, calcining at a temperature of 400°C or higher.

Furthermore, the time required for filtering and washing the precipitate can be shortened, and the resulting raw material powder has uniform particle size and composition, making it extremely industrially advantageous to easily sinter perovskites and their solid solutions. We discovered that it is possible to produce raw material powder of 2
We have arrived at the present invention.

The present invention is.

(1) Perovskite represented by the general formula ABO3 (where A represents one or more 12-coordinate oxygen metal elements, and B represents one or more 6-coordination metal elements of oxygen). When producing the raw material powder for the mold structure and its solid solution, a precipitate of the A component is produced using an aqueous solution of the A component compound and a precipitate forming solution, and then an aqueous solution of the B component compound is added to produce a B component precipitate. or A component and B
A first step of generating a precipitate by changing the order of generating the precipitate of the components.

(2) A second step in which the precipitate obtained in the first step is washed and passed through a rotary filter press.

(3) After emulsifying the precipitate in the second step.

The 6th step is drying.

(4) 400 to 100% of the dried product obtained in the third step
The fourth step is calcination at 0'C.

The present invention relates to a method for producing a raw material powder of an easily sinterable perovskite structure and a solid solution thereof, which is characterized by comprising the following steps.

Next, each step of the second invention will be explained.

First step: Examples of the oxygen 12-coordination metal of component A in the general formula include rare earth elements such as s Pb, Ba, Ca, Sr, and La. In addition, the oxygen hexacoordination metal elements of the B component include 9, for example, +Ti, Zr, M7°Sc,
Hf, Th, W, Nb, Ta, C! r, Mo, Mn, P
e, (!O, Ni.

Zn, C! d, Atlan, As, B
Examples include i.

Combinations of two or more elements in the B component in perovskites and their solid solutions are combinations of elements with equal valences, such as the combination of T1 and Zr, and combinations in which the proportions are arbitrarily changed (the same applies to the case of the A component). .

In addition, 1 such that the entire B position satisfies the electrical neutrality condition, for example +Fe'',: -) N'''' r + ``3+ and +
W6+.

+M1 and [0]b may be used, and furthermore, it may have an excess or deficiency of charge at the position of the A component or the position of the B component, and these charges may be compensated by the generation of cation defects and anion defects. Na.

For example, the combination of T1 and W of the B component (cation defect compensation), the combination of T1 and At (anion defect compensation), or the combination of the A component of La and Ba (
cation defect compensation), etc. In addition, the perovskite and its solid solution in the present invention may also include non-stoichiometric perovskites in which the molar ratio of the A component and the B component is shifted to a value higher or lower than 1.0, and vacancies are introduced at the B position or the A position. include.

Component compounds for preparing an aqueous solution of each compound of component A and component B, which are constituent components of perovskite and its solid solution, include, but are not particularly limited to, their hydroxides, carbonates, oxysalts, and sulfates.

Inorganic acid salts such as nitrates and hydrochlorides, acetates, and formates.

Examples include organic acid salts such as oxalate, oxides, and metals. If these are not soluble in water, they may be soluble by adding a mineral acid such as hydrochloric acid.

Examples of the precipitate-forming liquid include ammonia, ammonium carbonate, caustic alkali, oxalic acid, and the like, and any one may be selected from these. In order to generate a precipitate of the constituent components, an aqueous solution of each constituent component may be added to the precipitate forming liquid while stirring the precipitate forming liquid, or vice versa. The addition is preferably carried out while stirring the liquid.

In addition, when forming a precipitate, for example, after forming a precipitate of component A, an aqueous solution of component B may be added after removing anions that would interfere with subsequent steps to form a precipitate.

Yet again. After producing the precipitate of component A, the type and concentration of the precipitate forming liquid may be selected and adjusted as appropriate to make it suitable for producing the precipitate of component B.

In addition to the A component and the B component, a trace component for controlling the sinterability and properties of the perovskite may be added. Furthermore, as described above, the precipitation of component A and component B may be formed in multiple stages, or may be caused to precipitate alternately, if necessary. By forming the precipitate in this manner, a homogeneous precipitate containing all the components can be obtained.

The precipitate obtained by this process contains component A and component B, which are the constituent components of perovskite and its solid solution, which is a conventional method.
Create a mixed solution by mixing all of the component compounds together,
Compared to the coprecipitation method, which involves adding a precipitate-forming liquid such as an alkali to the solution and causing coprecipitation.

It has the characteristic that a uniform precipitate can be obtained.

2nd step: The precipitate obtained in the 1st step is filtered and washed using a rotary filter press.

The filtration and washing may be performed simultaneously using a rotary filter press, but in order to improve the washing effect, a separate washing tank may be provided and the washing may be performed in combination with the rotary filter press.

The concentration of nitrate ions and chloride ions contained in one mouthful of filtration and rinsing using a rotary filter press is 100%.
It is suitable to carry out so that it is below ppm, preferably below 10 ppm.

As a furnace cloth for rotary filter press.

Airflow amount 0.01~2 cc/sea-crA+
Particularly suitable is 0.02 to 1 cc/5ec-i.

The rotation speed of the rotary is 300 to 1500 rpm + especially 8
00-100 rpm is suitable.

The mouth overpressure is preferably 1 kgZ- or more, particularly 1 to 5 to 9/cA.

The time required for filtration and washing varies depending on the filtration area of the rotary filter press, the amount of precipitate, and the amount of washing water. The concentration of nitrate ions and chloride ions contained in oral fluids is determined by a conventional analytical chemical method such as a titration method or an ion chromatography method.

If the slurry concentration of the precipitate obtained in this step is extremely high or low, a suitable emulsion may not be obtained in the first step (third step), so the slurry concentration (in terms of solids) is 1 to 15% by weight, preferably 5 to 1% by weight.
It is preferable to adjust the amount to 6% by weight.

Sixth step: After the precipitate in the second step is emulsified, it is dried.

Emulsification treatment is performed at a viscosity of 20°C (converted).

It is preferable to set it to 5 to 50 centipoise, particularly 10 to 30 centipoise.

The emulsification method is not particularly limited.

Examples include homogenizers, attritors, sand mills, ball mills, line mills, and the like.

The temperature of the emulsification treatment is not particularly limited.

A temperature of 10 to 50°C, particularly 20 to 40°C is suitable.

For drying, it is preferable to instantaneously dry the emulsified precipitate as a precipitate slurry, since this can make the particles and composition of the perovskite raw material powder uniform. The drying method is not particularly limited, but suitable examples include drum drying, spray drying, and the like. The drying temperature is usually preferably in the range of 50 to 300°C.

Fourth step: The dry powder in the third step is calcined. If the calcination temperature is too low, the precipitate will dehydrate.

If the thermal decomposition is insufficient, and if the temperature is too high, the powder will become coarse, so it is particularly preferable to select a temperature in the range of 400 to 1000°C.

〔Example〕

EXAMPLES The present invention will be explained in more detail by showing Examples and Reference Examples below.

Example 1 Titanium tetrachloride (component B) L897Kf, zirconium oxychloride (component B) 3.223 and 9 were dissolved in water 100 to prepare an equimolar mixed aqueous solution of Ti and Zr. This solution was stirred with 6N ammonia water.
00 was gradually dropped into the solution to form a white hydroxide coprecipitate of Zr and T1. While continuing stirring, a solution of lead nitrate 6,624 and 9 dissolved in 30 t of water was added to the dispersion of this coprecipitate to uniformly precipitate the hydroxides of Zr, Ti, and PB. Had made. The chlorine ions and nitrate ions adsorbed on this precipitate nerary were washed using a rotary filter press (manufactured by Kotobuki Giken Kogyo), and the mixture was passed through the mouth.

Washing was performed for 4 hours using 2.57/hr water. At that time, the concentrations of chloride ions and nitrate ions in the oral fluid were less than 10 ppm, respectively.

Using a homogenizer, the washed precipitate slurry is
The mixture was emulsified by stirring at 10,000 rpm for 0.5 hours.

The viscosity of the emulsion was 21 centivoise at 20°C. This emulsion is spray-dried.

Set temperature t, oo"c, (drying temperature 150'c)"c'
It was dried to obtain a powder.

This dry powder was calcined at 650°C for about 2 hours to produce pb(Z
ro, s·T io, s ) 03 powder was obtained. This powder was ground in a ball mill. When we took a portion of the crushed powder and observed the particles using a scanning electron microscope, we found that the average particle size was as small as 0.25 μm, and the distribution of 50 particles was 0.10 to 0.45 μm, indicating that the particles were uniform and uniform in size. A fine powder was obtained. Also, βCO8 by X-ray diffraction method
As a result of plotting the relationship between θ and sin θ (where β represents the half width of the diffraction line and θ represents the flag angle), the horizontal axis (
It was confirmed that the composition was parallel to the 5ine axis) and had a uniform composition without any compositional fluctuations.

In addition, polyvinyl alcohol (below) is added to this powder.

1t/crA by adding 0.8% by weight of PVA (abbreviated as PVA)
As a result of molding and sintering at 1150° C. for about 2 hours in a lead atmosphere, the density was 7.99. The actual density at the time of molding was 4.85, which was about 60% of the theoretical density.

Reference Example 1 After producing a perovskite precursor precipitate in the same manner as in Example 1, 500. ! Transfer to a container and add 300 tons of water.
The mixture was washed twice and passed through a normal mouth filter (Nutche) twice. For reference, the required time so far was 7 days. Put this cake in a box dehydrator.

After drying for 12 hours at a drying temperature of 100°C, pulverize,
Calcinate at a calcining temperature of 650℃ for about 2 hours.

Pb(Zr@,5Tio,5)03 powder was obtained.

When the particles of this powder were observed using a scanning electron microscope, the average particle diameter was 0.34 μm, and the range of the 50 particles was 0.03 to 0.65 μm.

Additionally, 0.8% by weight of PVA was added to this powder.

11/- and sintered at 1150° C. in a lead atmosphere for about 2 hours, the density was 7.45.

The bulk density at the time of molding is 4.62, which is about 5% of the theoretical density.
It was 7%.

〔Effect of the invention〕

According to the method of the present invention, since all the components are not co-precipitated as in the conventional method, but the precipitates are generated sequentially, a precipitate in which two or more phases are highly interdispersed can be obtained, and the precipitate slurry can be After one wash with a rotary filter press, the precipitate is emulsified, dried, and calcined.
When a precipitate is formed.

The resulting powder is uniform in particle size and composition, and is easy to sinter and can efficiently produce raw material powders for perovskite and its solid solution with high bulk density. .

Furthermore, even if a cheap chloride such as titanium tetrachloride is used as a raw material, uniform fine particles containing almost no chlorine can be obtained, and precipitates can be washed and filtered in large quantities in a short period of time. Since it can be processed and dried quickly due to emulsification treatment, raw material powders of perovskite and its solid solution can be produced in large quantities at low cost and with good reproducibility.

Claims (4)

[Claims] (1) Perovskite type represented by the general formula ABO_3 (where A represents one or more 12-coordinated metal elements of oxygen, and B represents one or more 6-coordinated metal elements of oxygen). When producing the raw material powder of the structure and its solid solution, a precipitate of the A component is generated using an aqueous solution of the A component compound and a precipitate forming liquid, and then an aqueous solution of the B component compound is added to generate a precipitate of the B component, or , a first step of producing precipitates by changing the order of producing the precipitates of component A and component B; (2) a second step of washing and filtering the precipitate obtained in the first step with a rotary filter press; (3) a third step of drying after emulsifying the precipitate in the second step; (4) 400 to 100% of the dried product obtained in the third step
A method for producing a raw material powder of an easily sinterable perovskite structure and a solid solution thereof, comprising the following steps: a fourth step of calcining at 0°C.