JPH0367966B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a raw material powder of a perovskite structure compound (hereinafter referred to as perovskite) and a solid solution thereof.

Perovskites and their solid solutions are piezoelectric materials,
It is widely used as functional ceramics for dielectrics, semiconductors, sensors, optoelectronic materials, etc. Recently, the sophistication of functional ceramics has progressed, and raw material powders of perovskite and its solid solution that meet these demands can be produced efficiently in large quantities with easy sinterability, uniformity, high bulk density, and low cost. Development of technology is required.

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

The dry method is a method in which compounds of constituent raw materials are mixed in a dry method and then calcined. However, with this method, it is difficult to obtain a raw material powder with a uniform composition, so it is difficult to obtain a perovskite and its solid solution with excellent functionality, and the sinterability is also not sufficient.

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

According to this coprecipitation method, it is easy to obtain powder with excellent uniformity, but because of its uniformity, the particles coagulate during precipitation, drying, or calcination to form secondary particles, making it easier to sinter. I had a flaw that made it difficult to become sexually sensitive.

In addition, in the coprecipitation method, if the precipitate forming ability of each component in the precipitate forming liquid is not the same, for example, a certain component may form 100% precipitate, but other components may not be able to form any precipitate. It may be difficult to achieve the desired composition.

Furthermore, perovskite functional materials very often contain lead and titanium at the same time. When producing such materials industrially, it is desirable to use inexpensive titanium tetrachloride as the titanium raw material. However, when this is used in the coprecipitation method, the chlorine ions in titanium tetrachloride react with lead 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 [TiO(NO ₃ ) ₂ ] instead of titanium tetrachloride.
Titanium oxynitrate is expensive and therefore not practical for industrial production.

[Purpose of the invention]

The present invention uses a method that can eliminate the drawbacks of conventional coprecipitation methods, and furthermore, a perovskite that satisfies the four requirements of easy sinterability, uniformity, low cost, and high bulk density, and its perovskite. An object of the present invention is to provide a method for efficiently producing solid solution raw material powder.

[Structure of the invention]

As a result of intensive research to achieve the above object, the present inventors found that the general formula ABO ₃ (where A represents one or more of the 12-coordinated metal elements of oxygen, and B represents 1 of the 6-coordinated metal elements of oxygen) When producing a raw material powder of perovskite and its solid solution represented by (species or two or more species) by a wet method, precipitation of component A and component B is sequentially produced in the presence of amino acids. A precipitate of uniform particles in which fine particles are highly mutually dispersed is obtained, and the raw material powder obtained by calcining the precipitate has a narrow particle size distribution, consists of fine particles with uniform particle size, and has a uniform composition. It was discovered that easily sinterable perovskite raw material powder can be manufactured very industrially advantageously, and the present invention was achieved.

The present invention is based on the general formula ABO ₃ (where A is oxygen 12
B represents one or more types of coordination metal elements, and B represents one or more types of oxygen 6-coordination metal elements. )
A raw material powder of a perovskite-type structural compound (hereinafter referred to as perovskite) and its solid solution represented by the above is precipitated with an aqueous solution of a compound containing a metal element as an A component and a precipitation forming liquid, and then a precipitate is formed using a precipitate forming solution containing a metal element as an A component. A precipitate is generated by an aqueous solution of the compound and a precipitate forming solution, or
When the precipitates of the component and B component are produced in a different order from the above and then the precipitates are calcined, each of the precipitates is produced in the presence of amino acids. The present invention relates to a method for producing easily sinterable perovskite powder.

According to the present invention, the drawbacks of conventional coprecipitation methods can be overcome.

Examples of the oxygen 12-coordination metal element of the A component of the general formula ABO ₃ include rare earth elements such as Pb, Ba, Ca, Sr, and La. Also, the B component oxygen 6
Examples of coordination metal elements include Ti, Zr, Mg,
Sc, Hf, W, Nb, Ta, Cr, Mo, Mn, Fe,
Examples include Co, Ni, Zn, Cd, Al, Sn, As, Bi, etc.

Component compounds for preparing an aqueous solution of compounds containing metal elements 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 salts such as nitrates and chlorides, organic acid salts such as acetates and oxalates, and oxides. These are generally used as aqueous solutions. If it is not soluble in water, an acid may be added to make it soluble.

The amino acids used in the present invention are not particularly limited, but include, for example, glycine represented by H ₂ NCnH ₂ nCOOH (where n represents 1, 2 or 3), γ-aminobutyric acid, β-alanine Lower aliphatic amino acids such as are preferred. The amount of amino acids to be used is generally 0.01 to 20, preferably 0.1 to the total number of moles of the compound containing a metal element as component A and the compound containing a metal element as component B.
~15 times the molar amount is appropriate.

Examples of the precipitation forming liquid include ammonia, ammonium carbonate, caustic alkali, oxalic acid, and the like.

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 in the presence of amino acids, or vice versa. good. It is preferable that the addition be carried out while sufficiently stirring the liquid.

In addition, when forming a precipitate, for example, after forming a precipitate of one component, washing with water to remove anions, dispersing the precipitate in fresh water or alcohol, and then dispersing the precipitate of another component in the presence of amino acids. A precipitate may be generated by adding an aqueous solution of and a precipitate forming liquid.

Furthermore, in the presence of amino acids, component A or component B
After the components are precipitated, compounds containing metal elements other than those mentioned above may be precipitated by appropriately selecting the type and concentration of the precipitate forming liquid.

In addition to A and B components, when adding trace components to control the sinterability and properties of perovskite, when preparing the solution of A and B components,
Minor amounts of these components may also be added. Further, if necessary, as described above, the precipitation of component A and component B may be formed in multiple stages, or may be caused to precipitate alternately. However, when forming a precipitate of each component, it is necessary to have an amine acid present.

The precipitate obtained by the above method is washed, filtered, dried, and then calcined by a conventional method. Drying may be carried out under atmospheric pressure or under reduced pressure.

If the calcination temperature is too low, dehydration and thermal decomposition of the precipitate will be insufficient, and if it is too high, the powder will become coarse, so the calcination temperature is usually 300-300℃.
A range of 1000°C is preferred.

〔Example〕

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

Example 1 0.2 mol of glycine and 400 ml of 28% by weight ammonia water
was dissolved in water 1 to prepare an ammonia-glycine mixed aqueous solution. While stirring this solution, a mixed aqueous solution of Pb ²⁺ and Zr ⁴⁺ prepared by dissolving 0.2 mol of nitrate and 0.1 mol of zirconium oxychloride in 1 part of water was added dropwise to form white Pb and Zr hydroxides. A precipitate formed. A solution prepared by dissolving 0.1 mol of titanium tetrachloride in 300 ml of water was added and mixed to this precipitate slurry while stirring to form a homogeneous precipitate of hydroxides of Pb, Zr, and Ti. After washing this precipitate, it was dried and calcined at 600℃ for about 2 hours to form Pb(Zr _0.5 Ti _0.5 ).
Obtained _O3 powder. This powder was ground in a ball mill.

As a result of observing this powder using a transmission electron microscope, the average particle diameter was 0.16 μm, and the particle size distribution was 0.10 to 0.20 μm, indicating that the particles were very well aligned.

This powder was molded at 1 t/cm ² and sintered at 1100° C. for about 3 hours in a lead vapor and oxygen atmosphere, resulting in a density of 7.97 g/cc, which is almost the theoretical density.

Comparative Example 1 Pb(Zr _0.5 Ti _0.5 ) O ₃ was produced in the same manner as in Example 1, except that glycine was not present during precipitate formation.
A calcined powder was obtained.

When the shape of this powder was observed using a scanning electron microscope, the average particle size (average of 50 particles) was 0.3 μm, and the particle size distribution was 0.10 to 0.39 μm. It was large and had a wide particle size distribution.

Further, this powder was molded at 1 t/cm ² and sintered at 1100° C. for about 3 hours in a lead vapor and oxygen atmosphere, resulting in a density of 7.85 g/cc, which was lower than that of Example 1.

Example 2 A Pb(Zr _0.5 Ti _0.5 ) O ₃ calcined powder was obtained by carrying out the same operation as in Example 1 except that the amount of glycine used in Example 1 was 1.0 mol instead of 0.2 mol.

Particle observation of this powder using a transmission electron microscope revealed that the average particle diameter (50 particles) was 0.15 μm, and the particle size distribution was 0.07 to 0.19 μm.

This powder was molded at 1 t/cm ² and sintered at 1100° C. for about 3 hours in a lead vapor and oxygen atmosphere, resulting in a density of 7.97.

Example 3 The same procedure as in Example 1 was performed except that β-alanine was used instead of glycine in Example 1.
Pb(Zr _0.5 Ti _0.5 ) O ₃ calcined powder was obtained.

When observing the particles of this powder, the average particle size was
It was 0.17 μm.

When this powder was molded at 1 t/cm ² and sintered at 1100° C. for about 3 hours in an atmosphere of lead vapor and oxygen, its density was 7.95 g/cc, almost the theoretical density.

Example 4 Aqueous solution 1 in which 60.28 g _of lead nitrate [Pb(NO ₃ ) ₂ ] and 7.79 g of lanthanum nitrate [La(NO ₃ ) 3.6H ₂ O] were dissolved.
1 of 2N ammonia water containing 75g of glycine
was added dropwise to the solution while stirring to form a coprecipitate. While stirring the dispersed solution of this precipitate, glycine 15
g, zirconium oxychloride (ZrOCl ₂ 8H ₂ O)
An aqueous solution of 40.97 g of titanium tetrachloride and 13.09 g of titanium tetrachloride dissolved in 300 c.c. of water was added dropwise to obtain a homogeneous precipitate of hydroxides of lead, lanthanum, zirconium, and titanium.
This precipitate was washed with aqueous ammonia, filtered, and dried.

Furthermore, this dry powder was heat-treated at 750° C. for about 2 hours to obtain a powder having a composition of Pb _0.91 La _0.09 (Zr _0.65 Ti _0.35 ) _0.9775 O ₃ .

This powder was ball-milled in the presence of ethanol, and part of it was observed using a scanning electron microscope. As a result, the average particle size was 0.095 μm, and the particle size distribution was 0.05 to 0.140 μm, indicating that the particle size was almost uniform. Was. Further, as a result of measuring compositional fluctuations using X-ray diffraction, no fluctuations were observed.

This powder was molded at 1.5 t/cm ² and sintered at normal pressure of 1100° C. for 40 hours in a mixed atmosphere of oxygen gas and lead vapor. This gives a density of 7.80 and a transmittance of 75%
(1 mm thickness) translucent PLZT was obtained.

〔Effect of the invention〕

When a precipitate is generated by the method of the present invention, if the precipitate is sequentially generated in the presence of amino acids, a precipitate in which fine and uniform particles are highly interdispersed is obtained, resulting in coagulation during calcination. difficult to do,
Powder consisting of uniform fine particles with a narrow particle size distribution that is easily sinterable can be produced with good reproducibility.

In addition, in this process, each phase is highly mutually dispersed, so that the calcined material achieves sufficient uniformity. Further, since the process is simple, it has excellent effects such as being able to obtain easily sinterable powder with good reproducibility and at low cost.

Claims (1)

[Claims] 1 Perovskite structure 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). The raw material powder of the compound (hereinafter referred to as perovskite) and its solid solution is
A precipitate is generated by an aqueous solution of a compound containing a metal element of component A and a precipitate forming liquid, and then a precipitate is generated by an aqueous solution of a compound containing a metal element of component B and a precipitate forming liquid, or B
An easy-to-sinter method characterized in that each of the precipitates is produced in the presence of amino acids when the precipitates of the components are produced in a different order from the above and then the precipitates are calcined. A method for producing crystalline perovskite powder.