JPH0481528B2 - - 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 was sometimes difficult to obtain the desired composition, and in particular, it was difficult to precipitate 100% of the Mg component and Ni component.

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]

The present inventors have conducted extensive research to achieve the above object, and as a result, have arrived at the present invention.

The present invention is based on the general formula x[Pb(A _1/3 Nb _2/3 )O ₃ ]-y
[PbTiO ₃ ]-z [PbZrO ₃ ] (where A represents Mg and/or Ni, x, y and z are mol%
and x+y+z=100. ) When producing a raw material powder for a perovskite-type structural compound (hereinafter referred to as perovskite) and its solid solution, an aqueous solution in which an Nb compound is dissolved or dispersed is brought into contact with a precipitate forming solution to form a precipitate of the Nb component. After that, (1) add an aqueous solution of Pb and Zr compounds to
(2) Adding an aqueous solution of Ti and Zr compounds to form a precipitate of Ti component;
Then, an aqueous solution of a Pb compound is added to form a precipitate of the Pb component, and then a solution of an alkylamine and an aqueous solution of a compound containing a metal element of the A component are added to form a precipitate of the A component. The present invention relates to a method for producing raw material powder of easily sinterable perovskite and its solid solution, which is characterized by forming a precipitate and calcining the obtained precipitate.

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

General formula x in the present invention [Pb(A _1/3 Nb _2/3 ) O ₃ ]
The A component of the perovskite and its solid solution represented by -y[PbTiO ₃ ]-z _[ PbZrO ₃ ] is Mg and/or _Ni , and the _Pb and (A _1/3 Nb _2/3 ) component atomic ratio [Pb/
(A _1/3 Nb _2/3 )], the atomic ratio of Pb and Ti in PbTiO ₃ (Pb/Ti) and the atomic ratio of Pb and Zr in PbZrO ₃ (Pb/Zr) are usually 1.0, but this Nonstoichiometric perovskites with atomic ratios shifted to values higher or lower than 1.0 are also included.

Furthermore, x, y and z in the above general formula represent mol%, represent arbitrary numbers, and can take various values depending on the application, but usually x is 5 to 90, y is 5 to 80, and z
is preferably 5 to 80 mol%.

A compound containing a metal element of A component, which is a component of perovskite and its solid solution, and a Pb component,
The component compounds for preparing an aqueous solution of Nb component, Ti component, and Zr component compounds include, but are not particularly limited to, their inorganic salts such as hydroxides, carbonates, oxysalts, sulfates, 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.

Examples of the precipitation forming liquid include ammonia, ammonium carbonate, caustic alkali, 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, or vice versa.
The addition is preferably carried out while sufficiently stirring the liquid.

Examples of the alkylamine used in the present invention include primary amines having a lower alkyl group such as methylamine, ethylamine, propylamine, and butylamine; primary amines having a lower alkyl group such as cyclohexylamine; and primary amines having a lower alkyl group such as dimethylamine and diethylamine. Component A such as secondary amines and tertiary amines with lower alkyl groups such as triethylamine can be completely precipitated.
Mention may be made of alkylamines with a pKa of 10-11.

The amount of alkylamine used is preferably 0.5 to 20 times the total number of moles of the component A compound.
When adding alkylamine, NH ⁺ ₄
If the concentration of NH ⁺ 4 is too high, it may not be possible to completely precipitate each constituent component _. Preferably, the concentration is 0.3 mol/or less.

When adding a solution of an alkylamine and an aqueous solution of a compound containing a metal element as component A, even if the aqueous and/or alcohol solution of the alkylamine is added first, the aqueous solution of the compound as component A must be added first. They may be added simultaneously, or in multiple stages. Further, if NH ⁺ ₄ ions are not present, they may be added from the beginning.

In addition, when forming a precipitate, for example, after forming a precipitate of Nb, Pb, Ti or Zr components, after washing with water to remove anions that interfere with subsequent steps,
It is desirable to disperse the precipitate in fresh water or alcohol before proceeding to the next step.

Furthermore, precipitation of Nb component and Pb and Zr components,
Alternatively, when forming a precipitate of the Nb component and Ti and Zr components, the shape of the resulting particles can be controlled by appropriately adjusting the type and concentration of the precipitate forming liquid and the temperature during precipitate formation.

In addition to Pb, Ti, Zr, Nb, and A components, if trace components are added to control the sinterability and properties of perovskite, these trace components are added when preparing a solution of each of the above components. You may let them.

Further, as described above, the A component and the Nb component may be precipitated in multiple stages, or may be precipitated alternately, if necessary.

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.
A range of 1200°C is preferred.

〔Example〕

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

Example 1 50 [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] −36.5 [PbTiO ₃ ] −13.5 [PbZrO ₃ ] 4.430 g of niobium oxide (Nb ₂ O ₅ ) powder was dispersed in 100 ml of water, Furthermore, 1000 ml of 6N ammonia water was added. In addition, 33.12 g of lead nitrate [Pb(NO ₃ ) ₂ ] and 3.063 g of zirconium oxynitrate [ZrO(NO ₃ ) ₂ ]
A solution prepared by dissolving this in 1000 ml of water was added to form a precipitate. Furthermore, add 6.925 g of titanium tetrachloride (TiCl ₄ ) to water.
A solution dissolved in 350 ml was added to form a precipitate.
The solution was decanted four times by allowing the precipitate-containing liquid to stand still, removing the supernatant liquid, adding fresh water and stirring thoroughly, and then allowing it to stand again and removing the supernatant liquid. An aqueous solution of 25 g of diethylamine in 50 ml of water was added. Add magnesium nitrate [Mg
A solution of 4.273 g of (NO ₃ ) ₂ ·6H ₂ O] dissolved in 300 ml of water was gradually added to form a precipitate. After washing, filtering, and drying this precipitate, the composition was analyzed and found to be the same as the original elemental composition. Further, this precipitate was calcined at 750°C for 2 hours. This powder was subjected to a ball mill treatment in the presence of ethanol, and a portion of the powder was observed using a transmission electron microscope to find that the particle size was uniform at about 0.2 μm.

Add polyvinyl alcohol (hereinafter referred to as
As a result of adding 0.8wt% of PVA (abbreviated as PVA) and molding at 1t/ ^cm2 , and sintering at 1150℃ for 2 hours in a lead atmosphere,
Its density was 7.98 g/cc.

Example 2 15 [Pb (Ni _1/3 Nb _2/3 ) O ₃ ] −45 [PbTiO ₃ ] −40 [PbZrO ₃ ] 13.300 g of niobium oxide powder was added to 3N ammonia water.
Dispersed in 500ml. A solution of 33.123 g of lead nitrate and 9.24 g of zirconium oxynitrate dissolved in 200 ml of water was added to form a precipitate. Furthermore, a solution of 8.538 g of titanium tetrachloride dissolved in 100 ml of water was added to form a precipitate. This precipitate was decanted four times to remove dissolved NH ⁺ ₄ ions, and then a solution prepared by adding water to 25 g of diethylamine to make 50 ml was added. Add nickel nitrate [Ni(NO ₃ ) ₂ .
A solution of 1.454 g of 6H ₂ O] dissolved in 100 ml of water was added to form a precipitate. After washing, filtering, and drying this precipitate, the composition was analyzed and found to be the same as the original elemental composition. This precipitate was calcined at 750°C for 2 hours. Ethanol was added to this powder and it was subjected to ball milling, and a portion of the powder was observed using a transmission electron microscope to find that the particles had a uniform particle size of approximately 0.18 μm.

0.8 wt% of PVA was added to this powder, molded at 1 t/cm ² and sintered at 1150° C. for 2 hours in a lead atmosphere, resulting in a density of 7.99 g/cc.

Example 3 15 [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] −45 [PbTiO ₃ ] −40 [PbZrO ₃ ] In Example 2, except that 1.454 g of nickel nitrate was replaced with 1.282 g of magnesium nitrate, Example 2
A calcined powder sintered body was obtained using the same method and operation as above.

Elemental analysis of the composition of the precipitate revealed that the elemental composition was the same as that of the charged material, and the density of the sintered body was 7.98 g/cc.

Example 4 50 [Pb (Mg _1/6 Ni _2/3 ) O ₃ ] -36.5 [PbTiO ₃ ] -13.5 [PbZrO ₃ ] In Example 1, 4.273 g of magnesium nitrate was replaced with magnesium nitrate [Mg (NO ₃ ) ₂ . 6H ₂ O〕2.136g
A calcined powder was obtained by carrying out the same operation as in Example 1, except that 2.423 g of nickel nitrate [Ni(NO ₃ ) _{2.6H 2} O] was used. This powder was ball milled with ethanol added, and a portion of it was observed using a transmission electron microscope, and the particle size was approximately 0.19 μm.
It was a particle that was aligned.

0.8 wt% of PVA was added to this powder, molded at 1 t/cm ² , and sintered at 1150° C. for 2 hours in a lead atmosphere, resulting in a density of 7.97 g/cc.

Comparative Example 1 A precipitate was produced in the same manner as in Example 1, except that diethylamine was not present. When the composition of this precipitate was investigated, it was found that it contained only about two-thirds of the amount of Mg.

Comparative Example 2 In Example 2, the diethylamine solution was
A precipitate was produced by the same method and operation as in Example 2, except that 500 ml of 6N ammonia water was used. When the composition of this precipitate was investigated, it was found that it contained almost no Ni.

Example 5 50 [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] −36.5 [PbTiO ₃ ] −13.5 [PbZrO ₃ ] 9.003 g of niobium chloride (NbCl ₅ ) was dissolved in 100 ml of water, and further 6N− 1000ml of aqueous ammonia was added. To this, 33.12 g of lead nitrate [Pb(NO ₃ ) ₂ ] and 3.063 g of zirconium oxynitrate [ZrO(NO ₃ ) ₂ ] were added.
A solution dissolved in 1000 ml of water was added to form a precipitate. Further, a solution of 6.925 g of titanium tetrachloride dissolved in 350 ml of water was added to form a precipitate. The solution was decanted four times by allowing the precipitate-containing liquid to stand still, removing the supernatant liquid, adding fresh water and stirring thoroughly, and then allowing it to stand again and removing the supernatant liquid. An aqueous solution of 25 g of diethylamine in 50 ml of water was added. This liquid magnesium nitrate [Mg(NO ₃ ) ₂ .
A solution of 4.273 g of 6H ₂ O] dissolved in 300 ml of water was gradually added to form a precipitate. Wash this precipitate,
After filtering and drying, the composition was analyzed and found to be the same as the original elemental composition. Furthermore, this precipitate
It was calcined at 750°C for 2 hours. This powder was ball-milled in the presence of ethanol, and a portion of it was observed using a transmission electron microscope, and the particle size was found to be
It was uniform at about 0.2 μm.

Add polyvinyl alcohol (hereinafter referred to as
As a result of adding 0.8wt% of PVA (abbreviated as PVA) and molding at 1t/ ^cm2 , and sintering at 1130℃ for 2 hours in a lead atmosphere,
Its density was 7.99 g/cc.

Example 6 50 [Pb (Mg _1/3 Nb _2/3 ) O ₃ ] −36.5 [PbTiO ₃ ] −13.5 [PbZrO ₃ ] 4.430 g of niobium oxide (Nb ₂ O ₅ ) powder was dispersed in 100 ml of water, Furthermore, 1000 ml of 6N ammonia water was added. A solution of 6.925 g of titanium tetrachloride and 3.063 g of zirconium oxynitrate dissolved in 500 ml of water was added to form a precipitate. The precipitate-containing liquid was allowed to stand, the supernatant liquid was removed, and 500 ml of 6N aqueous ammonia was added. Add 33.12g of nitrate to this and water.
A solution containing 300 ml of dissolved salt was added to form a precipitate.
The solution was decanted four times by allowing the precipitate-containing liquid to stand still, removing the supernatant liquid, adding fresh water and stirring thoroughly, and then allowing it to stand again and removing the supernatant liquid. An aqueous solution of 25 g of diethylamine in 50 ml of water was added. Add magnesium nitrate [Mg
A solution of 4.273 g of (NO ₃ ) ₂ ·6H ₂ O] dissolved in 300 ml of water was gradually added to form a precipitate. After washing, filtering, and drying this precipitate, the composition was analyzed and found to be the same as the original elemental composition. Further, this precipitate was calcined at 750°C for 2 hours. This powder was subjected to a ball mill treatment in the presence of ethanol, and a portion of the powder was observed using a transmission electron microscope to find that the particle size was uniform at about 0.2 μm.

The above powder is mixed with polyvinyl alcohol (hereinafter referred to as
As a result of adding 0.8wt% of PVA (abbreviated as PVA) and molding at 1t/ ^cm2 , and sintering at 1150℃ for 2 hours in a lead atmosphere,
Its density was 7.95 g/cc.

〔Effect of the invention〕

General formula x [Pb (A _1/3 Nb _2/3 ) O ₃ ]-y [PbTiO ₃ ]-
When producing raw material powder of perovskite and its solid solution represented by z[PbZrO ₃ ], unlike the conventional coprecipitation method in which all components are coprecipitated at the same time, Nb, Pb, Ti, and Zr components are precipitated sequentially. Since component A is then precipitated in the presence of an alkylamine, component A and all other components, which were difficult to precipitate 100% with conventional methods, can be completely precipitated. As a result of obtaining a precipitate in which the phases are highly interdispersed, it is difficult to cause agglomeration during precipitate formation, drying, or agglomeration during calcination, and it is possible to produce easily sinterable powder with high bulk density with good reproducibility. I can do it.

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 General formula x [Pb (A _1/3 Nb _2/3 ) O ₃ ]-y [PbTiO ₃ ]
−z[PbZrO ₃ ] (A is Mg and/or
Ni is shown, x, y and z are mol%, x
+y+z=100. ) (hereinafter referred to as perovskite)
When producing raw material powder for Nb and its solid solution, Nb
After the aqueous solution in which the compound is dissolved or dispersed is brought into contact with the precipitate forming solution to form a precipitate of the Nb component, (1) an aqueous solution of Pb and Zr compounds is added to form a Pb
or (2) adding an aqueous solution of Ti and Zr compounds to form a precipitate of the Ti component.
Then, an aqueous solution of a Pb compound is added to form a precipitate of the Pb component, and then a solution of an alkylamine and an aqueous solution of a compound containing a metal element of the A component are added to form a precipitate of the A component. 1. A method for producing raw material powder of easily sinterable perovskite and its solid solution, which comprises generating a precipitate and calcining the obtained precipitate.