JPH0524860B2 - - Google Patents

Description

BACKGROUND TECHNICAL FIELD OF THE INVENTION The present invention relates to an ABO ₃ type perovskite oxide (where A represents Pb and B represents Ti and/or
The present invention relates to a method for producing Zr (representing at least one element selected from the group consisting of Zr). More specifically, the present invention relates to a reaction in which a precursor of an ABO ₃ type perovskite oxide is produced as an oxalate precipitate by adding an oxalic acid aqueous solution to an aqueous solution containing Pb and B element ions.
The amount of oxalic acid added is 0.96 to 1.04 mol, preferably 0.96 to 1.04 mol per mol of element A (Pb) present in the aqueous solution.
0.98 to 1.02 mol, more preferably 0.99 to 1.01
0.48 to 0.52 mol, preferably 0.49 to 0.51 mol per mol of B element (Ti and/or Zr)
mol, more preferably in the range of 0.495 to 0.505 mol. oxalic acid in an amount to achieve a stoichiometric ratio of 0.5 mole to the aqueous solution containing the element group, the best effect is obtained by contacting the aqueous solution containing the element group. .

Furthermore, the present invention provides Pb, which should be present in the aqueous solution.
The present invention relates to a method for producing the oxide, characterized in that Ti and/or Zr are supplied as nitrates.

Furthermore, the present invention relates to a method for producing the oxide powder having excellent powder characteristics with excellent reaction reproducibility by employing the above-mentioned characteristic production method.

ABO ₃ type perovskite oxides are widely used as piezoelectric materials and pyroelectric materials, either by themselves or in the form of a solid solution of two or more of these oxides.

Most of these materials are commercialized as sintered bodies made by baking and solidifying their powders. In this case, the quality is significantly influenced by the degree of sintering, and therefore, a powder with excellent powder characteristics is desired as a raw material for producing a good sintered body.

Prior art As a method for producing perovskite-type oxides,
The following methods are known.

(1) A method in which oxide powders of each component element are mixed and the mixture is heated to a high temperature to cause a solid phase reaction.

(2) A method in which oxalic acid is dropped into an aqueous solution containing ions of each component element to coprecipitate each component element as an oxalate salt, and the coprecipitated oxalate salt is thermally decomposed (for example, US Pat. No. 3352632).

(3) A method in which a mixture of alkoxides of each component element is hydrolyzed, coprecipitated, and the coprecipitated hydrolyzate is thermally decomposed (for example, JP-A-60-86022).

(4) A multi-stage wet synthesis method in which lead hydroxide and zirconium hydroxide are synthesized in advance using aqueous ammonia, a titanium tetrachloride solution is added thereto, and the mixture is precipitated with aqueous ammonia (Ceramics Association 1985 Conference Proceedings) However, However, these methods have some problems and are not necessarily satisfactory. For example, the solid phase reaction (1) not only has problems with the manufacturing process, such as requiring high temperatures and long periods of time, but also has problems with the product powder. That is, the powder obtained by this method is difficult to sinter, and therefore requires the use of high temperatures or the use of a sintering accelerator for sintering. In the coprecipitation method (2), it is difficult to coprecipitate each component in the desired ratio because the oxalates of each component have different solubility in water, which is the coprecipitation medium. The disadvantage is that it is difficult to obtain a composition with the same composition. Further, although the coprecipitation method (3) has the advantage of producing a product with high purity and high uniformity, it has the disadvantage that it is not easy to manufacture because each component is used as an alkoxide. Furthermore, although the multi-stage wet method (4) is a method that uses inexpensive materials, the calcined product must be sintered through a crushing process.

Yamamura et al. proposed an improvement to the oxalate method described in (2) above as a method to overcome these drawbacks of the conventional methods. That is, oxalic acid is soluble in ethanol, and Zr ion, Ti ion oxalate and
Reacting ions of ions selected from the group of Pb, Ba, Sr, or Ca (hereinafter collectively referred to as A ions) with oxalic acid to coprecipitate these ions as oxalate salts. (Japanese Unexamined Patent Publication No. 1983-
39722) and co-precipitation with A ions and Zr ions or (Zr + Ti) ions as oxalate (Japanese Patent Application Laid-open No. 131505/1983).
A precipitate of high purity and uniform particle size (precursor of perovskite type oxide) with the desired composition is obtained, and when this is thermally decomposed, active ATiO ₃ which is extremely easy to sinter,
AZrO ₃ or A(Zr・Ti)O ₃ fine powder is obtained.
However, according to the disclosure, the generation
The pottery is ground and mixed again, and this powder is molded and sintered at 1000-1400°C.

That is, in this prior improved technique, the finely powdered perovskite-type oxide obtained by sintering the coprecipitate cannot be directly used for molding because the particles are fused to each other. A re-grinding and mixing step was necessary.

This re-grinding and mixing step required in the prior improved invention not only increases process costs and reduces the reliability of the final product due to contamination with impurities, but is always problematic due to the characteristics of perovskite oxide powders. In other words, the development of technology for manufacturing highly flexible piezoelectric films and dielectric films by compounding these perovskite-type oxide powders with polyvinylidene fluoride resin, polyoxymethylene resin, nitrile butadiene rubber, etc. is underway. However,
In this case, an easily dispersible fine powder with a uniform particle size distribution and no crystal distortion is required, but the fine powder obtained by re-grinding and mixing causes crystal distortion and does not have the expected performance. This is because it is known that it will not be possible to obtain it.

In addition, in dielectric films, it is necessary to uniformly disperse fine ceramic particles in a thin film of 10 μm or less, preferably 1 to 5 μm, and a crushed product has a problem in that the particle size distribution width is too wide to ensure reliability as a film. Points are pointed out.

Yamamura and the present inventors have conducted extensive studies on the mutual fusion phenomenon of fine particles of baked goods, and in this advanced improved technology, a small amount of chlorine ions remaining in the mixed aqueous solution of starting material ions cause the mutual fusion phenomenon of fine particles during the firing stage. They discovered that fusion was caused by the chlorine ion concentration and further discovered that fusion could be suppressed by lowering the chlorine ion concentration to a predetermined value or less.
174116) was completed.

Furthermore, the present inventors have developed a method that can significantly reduce manufacturing costs by drastically reducing the amount of ethanol used (Japanese Patent Application No. 77234/1982), and a method that further reduces manufacturing costs by substituting ethanol with isopropanol and normal propanol. How to do it (Tokkai Sho
No. 61-251519) was presented.

Problems and solutions in the prior art The present inventors have disclosed various improved methods regarding the synthesis of precursor precipitates of perovskite type oxides in an oxalic acid/alcohol system, but in all methods, the precipitate composition is Controlling the abundance ratio of elements was one of the important issues.

In other words, the joint invention with Yamamura (Japanese Patent Application Laid-Open No. 61-174116
Although it is disclosed in the _example of
In order to make the Ti/Pb ratio 1.00, the Ti/Pb ratio in the aqueous solution was
By setting the Pb ratio to 1.11, fluctuations in the element abundance ratio in the final product due to Ti dissolved in the reaction solution are suppressed. This operation is based on Japanese Patent Application No. 77234, 1983, which drastically reduced the amount of ethanol used, and Japanese Patent Application No. 77234, which changed alcohol to isopropanol.
It is also implemented in No. 251519.

In order to suppress the elution of Ti, this method involves more complicated operations than the method proposed in the above application, but
By adopting the dry ammonia blowing method disclosed in the issue, the Ti/Pb ratio in the solution and the PbTiO ₃
We succeeded in matching the Ti/Pb ratio.

Regarding the redissolution phenomenon of B element ions, especially Ti, in aqueous solutions, a high concentration of nitric acid is generated in the mother liquor due to the formation of an oxalate coprecipitate, which reacts with, for example, titanyl lead oxalate, and is calculated according to the following equation. The possibility of a large amount of Ti remaining in the mother liquor is known from research by Kazuhisa et al. (Telecommunications Research Institute, Research and Practical Application Report Special Issue No. 28 (1975)).

PbTiC(C ₂ O ₄ ) ₂ +2HNO ₃ →PbC ₂ O ₄ + TiO(NO ₃ ) ₂ +H ₂ C ₂ O _4The dry ammonia gas blowing method removes nitric acid produced by the oxalate production reaction and the nitric acid formed by the above reaction. be done
By neutralizing TiO(NO ₃ ) ₂ , the progress of the above-mentioned undesirable side reactions is suppressed. However, in this method, it is necessary to neutralize nitric acid, which is produced in 4 moles per mole of PbTiO ₃ , and oxalic acid, which is added in excess to complete the reaction, and as a result, a large amount of ammonium salt is It was also found that the oxidants were present in the precipitate, and that some ingenuity was needed in the calcination of the dried precipitate.

Furthermore, the present inventors attempted an oxalate precipitation reaction as a precursor of a perovskite-type oxide using an alcohol having a carbon number of 4 to 15 in an aqueous solution containing lead nitrate and titanium oxynitrate. We found that the set Ti/Pb ratio (atomic ratio) was almost completely reproduced in PbTiO ₃ obtained by calcining the precipitate, an unexpectedly good result that could not be obtained with ethanol or propanol. (Japanese Patent Application Laid-Open No. 61-251518). Although the above effects were confirmed under the conditions disclosed in the method,
Continuing stirring for a long time even after the addition of oxalic acid
Subsequent studies found that Ti re-dissolution occurs if over-operation takes a long time.
It was found that there was a problem with the stability of the produced precipitate over time.

The present inventors conducted extensive studies to ensure the stability of oxalate precipitation in the reaction solution, and found that it was previously accepted as a general rule regarding precipitation of oxalate in an alcohol-coexisting system. Oxalic acid/
An earlier application was filed (1985) stating the fact that quantitative precipitation is formed not at the stoichiometric ratio of Ti = 1/1 (molar ratio) but at the stoichiometric ratio of oxalic acid/Ti = 1/2 (molar ratio). This was disclosed in a patent application filed on September 24th entitled "Method for producing ABO ₃ type perovskite oxide." In addition, the application includes
It was also disclosed that Zr can be quantitatively precipitated by adding oxalic acid in an amount equivalent to oxalic acid/Zr=1/2 (molar ratio) when co-precipitating with Pb.

Summary of the Invention According to the earlier application (dated September 25, 1985), in an aqueous solution without adding ethanol or propanol,
It was disclosed that the recovery rate of Ti oxalate precipitate is at most 65% by weight, and the recovery rate decreases significantly as the concentration of titanium nitrate oxide in the aqueous solution increases.

The present inventors conducted a more detailed study on the behavior of oxalate from titanium oxynitrate in an aqueous solution, and found that in an aqueous solution where lead nitrate and titanium oxynitrate coexist, 1 mol of oxalic acid per 1 mol of Pb. ,
When Pb and Ti are brought into contact with an oxalic acid aqueous solution having a ratio of 0.5 mol of oxalic acid to 1 mol of Ti,
It has been found that a precipitate can be formed with an abundance ratio of approximately 1:1. They also discovered that Zr exhibits the same behavior as Ti in an aqueous solution in which lead nitrate coexists, leading to the completion of the present invention.

Introduction of the prior concept regarding the novel oxalic acid stoichiometric ratio Regarding the novel stoichiometric ratio in the above-mentioned oxalate precipitation of Ti and Zr, which is the main subject of the invention, we will introduce the stoichiometric ratio disclosed in the prior art and literature. However, a more specific explanation will be given to clarify the distinctiveness of the present invention.

Research on the synthesis of perovskite-type oxides from oxalate precipitates has been ongoing for a long time. What these studies have in common is that the elements constituting perovskite-type oxides and oxalic acid salts are
The reason is that it is assumed that the precipitate is obtained as a double salt represented by AB(C ₂ O ₄ ) ₂ ·xH ₂ O. In particular, regarding barium titanate, Clabaugh
BaTi(C ₂ O ₄ ) _{2.4H 2} O has been confirmed (Journal of Research of the National Bureau of Standards, Vol. 56, No. 5)
No., pp. 289-291 (1956) (Journal of
Research of the National Bureau of
Standards, 56 , [5], 289-291 (1956)).

In addition, in oxalate precipitation with lead as component A, PbTiO(C ₂ O ₄ ) ₂・nH ₂ O, PbZrO(C ₂ O ₄ ) ₂・
The patent identifies that nH ₂ O and Pb(Ti,Zr)O(C ₂ O ₄ ) ₂ ·nH ₂ O are precursor precipitates of PbTiO ₃ , PbZrO ₃ and Pb(Ti,Zr)O ₃ respectively. A claim has been made (US Pat. No. 3,352,632). The composition of the raw material for obtaining the above precursor precipitate [oxylic acid/(A
0.87 to 1.33 (mol/mol) is disclosed in the Examples. It is also noted that when the reaction temperature exceeds 20°C, the precipitation yield decreases and the abundance ratio of Ti and Pb changes during over-operation.

In Kazuhisa's paper mentioned above, PbTiO
(C ₂ O ₄ ) ₂・H ₂ O, PbZrO (C ₂ O ₄ ) ₂・2H ₂ O was obtained as an analysis result, and even in precipitation synthesis by coprecipitation method, the amount that satisfies this stoichiometric ratio is An experimental example in which acid is added is described. Also, Kazuhisa et al.
Publication No. 65196 discloses a method for synthesizing Pb(Zr,Ti)O ₃ using ammonium oxalate as a precipitant, but here also lead nitrate, titanyl nitrate (TiO(NO ₃ ) ₂ ), Zirconyl nitrate (ZrO
(NO ₃ ) ₂ ), by solution reaction of ammonium oxalate.
Create a coprecipitate of PbTiO(C ₂ O ₄ ) ₂ and PbZrO(C ₂ O ₄ ) ₂ ,
Filter the coprecipitate or evaporate the entire mother liquor to dryness,
Discloses a method of pyrolysis. In Example 3, 0.13 mole of zirconyl nitrate, 0.07 mole of titanyl nitrate, 0.2 mole of lead nitrate and 0.4 mole of ammonium oxalate.
Mol is used to obtain a complex oxalate giving the composition of Pb(Zr _0.65 Ti _0.35 )O ₃ . It is also stated that the purpose of the invention is to reduce the amount of complex oxalate that is easily soluble in water remaining in the mother liquor as much as possible to reduce the deviation in the composition of the coprecipitate, and to evaporate the whole mother liquor to dryness. Even when using this method, it should be easy to handle because the amount of mother liquor is small. That is, by changing the precipitant from oxalic acid to ammonium nitrate and neutralizing the nitric acid produced in the oxalic acid precipitation synthesis reaction to ammonium nitrate, titanium oxynitrate can be completely regenerated according to the reaction formula of Kazuhisa Maede et al. The dissolution of the complex sulfate salts could not be completely inhibited even when inhibited by the oxalate complex, suggesting that other dissolution factors are involved.

Yamamura et al. published JP-A-59-39722.
A method for synthesizing lead titanate using an ethanol method is disclosed, but the amount of oxalic acid added is 2.5 moles per mole of lead titanate. Also, JP-A-59-
Publication No. 131505 discloses a method for producing a perovskite-type oxide powder containing zirconium, but states that the amount of oxalic acid is preferably 2.5 mol per 1 mol of AZrO ₃ or A(Zr.Ti)O ₃ .

Prior invention by Yamamura and the present inventors (patent application
60-13910) and other prior inventions of the present inventors (Japanese Patent Application Nos. 60-77234, 60-77235, 60-77236)
No. 60-77237), 4 mol of oxalic acid is added to 1 mol of lead titanate to complete the precipitation reaction.

Vuelde et al. have also reported on the thermal decomposition behavior of PbTiO(O ₂ O ₄ ) ₂ 4H ₂ O (Thermochimica Acta, Vol. 14 (1976), pp. 269-278). (1976) 269−278)).

In other words, many researchers believe that complex oxalate precipitation is a prerequisite for research when element A is Ba, Sr, Ca or
It is easy to assume that the conventional concept that ABO(C ₂ O ₄ ) ₂ has been accepted regardless of whether it is Pb or not.

On the other hand, in an earlier application (filed on September 25, 1985), the present inventors reported that in a system in which ethanol and propanol coexist, although it was limited to a system in which Pb is combined with Ti and/or Zr, , (oxalic acid)/(A element + B element) =
It was shown that oxalate precipitates were quantitatively formed at a composition ratio of 1.5 (molar ratio), and there was no fear that the precipitate composition would change over time. In addition, in the example, the possibility that titanium oxalate has a compound form of (TiO) ₂・ (NO ₃ ) ₂・C ₂ O ₄ was suggested, and it was found that the conventional oxalate Concept and compound form regarding the precursor (considered to be the following based on the stoichiometric ratio of Ti) It was shown that it has a clear distinction from TiO.C ₂ O ₄ .

Novelty of the present invention The present invention provides that Ti and/or Zr in a coprecipitation reaction with Pb in a system using oxalic acid-water as a dropping agent, which could not form a quantitative precipitate in the previous application.
has a clear distinction from the previous application in that it has been found that the nitrates of the present invention give precursor precipitates suitable for the preparation of perovskite-type oxides with high reaction yields.

Furthermore, based on the analysis of the dried precursor precipitate by X-ray diffraction, fluorescent X-ray diffraction, elemental analysis, differential thermogravimetry, mass spectrometry of pyrolysis gas, _Raman spectrum, etc. It is also distinguishable from the earlier application in that it can suggest the possibility that the acid salt has a compound form of (TiO) _2. (OH) _{2.C 2} O ₄ .

Effects According to the method of the present invention, the following effects can be obtained.

(1) Pb/ of the desired perovskite oxide
The ratio of (Zr, Ti) can be almost completely matched to the ratio of the raw materials.

(2) Since there is no risk of the generated precipitate being redissolved in the mother liquor, the reproducibility of the reaction can be maintained even if the rate of oxalic acid addition, reaction time, elapsed time, etc. are matched to the optimum range at the industrial production level. can be secured.

(3) Since the alcohol that was required to be used in the earlier application does not have to be used, the cost of recovering alcohol (distillation equipment, variable costs for distillation, recovery losses) can be completely omitted.

Detailed description of the invention Production of perovskite oxide precursor precipitate The perovskite oxide targeted by the present invention is
ABO type ₃ , in which the A element is Pb and the B
The element is at least one element selected from the group consisting of Ti and Zr.

Both Ti and Zr used in the present invention are subjected to the reaction as titanium oxynitrate and zirconium oxynitrate.

Perovskite-type oxides that can be synthesized by the method of the present invention include PbTiO ₃ , PbZrO ₃ , Pb(Ti・Zr)
_O3 can be mentioned.

For lead, which is element A, salts other than chlorides, especially nitrates, are most suitable. In either case, Cl/Ti, Cl/Zr or
It is desirable to select the purity of the various raw materials so that Cl/(Ti+Zr) is 0.05 mol/mol or less, preferably 0.02 mol/mol or less, and more preferably substantially zero.

Co-precipitated ABO ₃ type perovskite oxide precursor is
By contacting an aqueous solution of oxalic acid with an aqueous solution of a compound of each element that provides an A element ion (Pb ²⁺ ) and an B element ion, it is obtained as a coprecipitate of oxalate salts of Pb and B element.

According to the method of the present invention, the amount of oxalic acid added is, in principle, 1 mole of ^the oxalate precursor ( It is necessary to quantitatively precipitate lead oxalate). Further, 0.5 mol of oxalic acid is required to be added to 1 mol of B element ions (Ti ⁴⁺ , Zr ⁴⁺ ).

The amount of oxalic acid added is within ±4% of the theoretically required amount for element A ions in the aqueous solution, preferably ±4%.
It may have a tolerance range of 2%, more preferably ±1%. Similarly, for element B ions, the amount of oxalic acid added is determined within a range of ±4% of the theoretically required amount, preferably within a range of ±2%, and more preferably within a range of ±1%. be able to.

The basis of the present invention is the oxalate precipitation of element B, which was conventionally thought to occur (oxalic acid/element B = 1/1
(molar ratio)) rather than the stoichiometric ratio of
This is based on the discovery that B can be obtained at a stoichiometric ratio of 2/1, so the coexistence of excess oxalic acid is
Involved in the redissolution reaction of oxalate precipitates of elements,
This is essentially undesirable because it acts in the direction of negating the features of the present invention. Therefore, the smaller the deviation from the stoichiometric ratio, the better.

A system in which oxalic acid is added at a ratio of 1.05 mol to 1 mol of lead nitrate and 0.525 mol to 1 mol of titanium oxynitrate (the amount of oxalic acid added is below the stoichiometric ratio).
The precipitate obtained from 105%) contains excess lead,
PbTiO ₃ powder obtained by firing has a red color.
This fact also shows that addition of excessive oxalic acid is not suitable for producing the ABO ₃ type perovskite type oxide monomer which is the object of the present invention.

On the other hand, in cases where it is desired to add an excessive amount of lead oxide in advance as a sintering aid or crystal growth promoter, as long as the precipitate is synthesized based on the stoichiometric ratio disclosed in the present invention, the patent claims of the present invention may be applied. Even if the amount of citric acid added exceeds the range, it is still essentially within the scope of the claims of the present invention.

On the other hand, since addition of oxalic acid below the stoichiometric ratio reduces the yield of oxide based on the raw materials, it is desirable to select a value as close to the disclosed stoichiometric ratio as possible.

The Pb ion concentration in the aqueous solution can be selected within a wide range using the upper limit of solubility of the starting material as a guide.
Preferably 0.01 to 0.6 mol/, more preferably
The amount can be selected from 0.05 to 0.3 mol/. The B ion concentration in the aqueous solution is uniquely determined by the Pb ion concentration.

Oxalic acid concentration in oxalic acid aqueous solution is 0.01−1.0
mol/, preferably 0.05-0.5 mol/ can be chosen.

The reaction temperature can be selected from a wide range, but
The temperature can be selected preferably from around 0°C to 50°C, more preferably from around 0°C to 30°C. Low temperatures that cause the aqueous solution to freeze must be avoided.
Furthermore, considering the thermal instability of titanium oxynitrate in an aqueous solution, increasing the temperature of the aqueous solution beyond 50°C after containing titanium oxynitrate may cause precipitation due to decomposition of titanium oxynitrate during the precipitation synthesis reaction. It is desirable to avoid this as much as possible since there is a risk that it may also be generated.

The reaction is proceeded by dropping an oxalic acid aqueous solution into the aqueous solution while vigorously stirring it at a predetermined temperature. It is preferable to set the oxalic acid aqueous solution at a predetermined temperature and then add it dropwise.

It is possible to start over-operation immediately after the completion of dripping, but
Over-operation can also be carried out after a suitable period of post-reaction.

The precipitate was separated by filtration to obtain a white cake,
In order to remove nitric acid produced by the reaction, appropriate washing with water is performed to remove as much of the mother liquor remaining in the precipitation as possible, and the washing liquid is separated to obtain a white cake. The number of times of washing can be determined as appropriate.

The obtained white cake is dried and then crushed to obtain a perovskite-type oxide precursor powder. Crushing at this stage is important in ensuring the flow of an appropriate amount of oxygen during the subsequent sintering. Note that the dry cake can be easily pulverized by a weak grinding force, and there is no need to completely disperse the particles at this stage, so there is no risk of contamination with impurities from the pulverizing means.

Production of perovskite type oxide fine powder The precursor powder is heated at an appropriate temperature, for example 500~
Bake at 1000℃. Although it is desirable that the sintering temperature be low, it is necessary to carry out the sintering at a temperature at which no weight change is observed. 500−800
It is more preferable to calcinate at ℃ in order to suppress sublimation of lead as much as possible.

Although it is necessary to perform firing in the presence of air, the purpose can be fully achieved even by firing in a furnace that does not have a forced flow mechanism such as a Matsufuru furnace.

The rate of temperature increase during baking can be 0.1-50°C/min, preferably 0.5-20°C/min. It is preferable that the rate of temperature increase up to around 400°C, at which the decomposition of oxalate ends, is not too high.

The content of the present invention will be explained in more detail below using experimental examples.

Experimental Examples Example 1 (Synthesis of PbTiO ₃ ) 500 ml of commercially available tetraisopropyl titanium was added dropwise to 7000 ml of distilled water to obtain hydroxide, which was filtered through a furnace and washed three times with 1000 ml of pure water to produce hydroxide. I got titanium. Commercially available special grade concentrated nitric acid 200
ml and left to stand day and night to obtain a titanium oxynitrate solution. The Ti concentration was determined gravimetrically as TiO ₂ and a result of 0.1304 g-Ti/ml was obtained.
300ml of titanium oxynitrate solution and 272.0g of special grade lead nitrate
and 3785 ml of pure water to obtain an aqueous solution with Ti/Pb (atomic ratio) = 1.0, which was maintained at 20°C.

4085ml of pure water and citric acid dihydrate (purity 99.5%)
Dissolve 155.28g, (oxalic acid)/(Pb+Ti)=
Prepare a dropwise solution corresponding to 1.5 (mol/mol),
It was kept at 20°C.

Add the dropwise solution to the aqueous solution while stirring vigorously.
It was added dropwise using a roller pump at a rate of 60 ml/min. After the dropwise addition was completed, stirring was continued for another 2 hours to complete the reaction.

After the post-reaction was completed, the mother liquor was separated using a pressurizer to obtain a white cake.

The obtained white cake was poured into 4085 ml of pure water, crushed and washed for 15 minutes, and the washing liquid was separated using a pressurizer. This operation was repeated three times to obtain a white cake.

The obtained white cake was dried in an air bath oven at 110°C for 16 hours, and then crushed for 2 minutes using a crusher to obtain lead titanate precursor powder (hereinafter abbreviated as "precursor powder"). Obtained.

Qualitative Characterization of Precursor Powder The compounds that the precursor powder consists of were investigated by various analytical means.

Analysis of the precursor powder by X-ray diffraction confirmed the presence of lead oxalate. It was not possible to identify compounds derived from titanium.

Elemental analysis of the precursor powder confirmed an abundance ratio of 1.0 lead, 0.95 titanium, 2.94 carbon, and undetected nitrogen; oxalic acid/(Pb+
Ti) = 1.46/1.95 = 0.75 (mol/mol), and it was found that the ratio of the charged raw materials was reproduced in the precursor powder.

When the precursor powder was heated at a rate of 10°C/min under air flow and subjected to thermogravimetric analysis, a weight loss of 28.1% by weight relative to the charged weight was observed when the temperature was raised to 800°C.

When the precursor powder was heated and decomposed at a rate of 10°C/min under He flow, and the desorbed gas was subjected to mass spectrometry (QMASS), the amount of NO ₂ generated was negligible.

When the precursor powder was subjected to Raman spectroscopy, the bond was detected.
There were no peaks derived from _NO3 .

Comprehensively combining the above various analysis results, the precursor powder obtained by the method of the present invention is formed from a coprecipitate of the composition PbC ₂ O ₄ and (TiO) ₂ (OH) ₂ C ₂ O ₄ . It was inferred that there is a high possibility that

Synthesis of PbTiO ₃ Precursor powder is heated to 250℃ in a Matsufuru furnace at 5℃/
After heating for 30 minutes, increase the temperature at a rate of 1.5℃/minute.
The temperature was raised to 700°C, maintained for 2 hours, and then slowly cooled to obtain the desired oxide in a yield of 91% by weight based on the charged raw materials. The Ti/Pb ratio (atomic ratio) of the oxide was obtained by fluorescence X-ray diffraction method of 1.02. Tetragonal crystals determined by X-ray diffraction
The formation of PbTiO ₃ was confirmed, and its crystal grain size was 250
It was Å. In addition, the formation of less than 1% PbTi ₃ O ₇ was observed. The BET specific surface area was 4.7 m ² /g. From this, an average particle diameter of 0.16 μm was determined.

The oxide was dispersed in water using an ultrasonic vibrator, and the particle size distribution was measured using a Microtrac DR particle size analyzer, and the results shown in FIG. 1 were obtained. When the oxide was dispersed in water using an ultrasonic vibrator and the particle shape was observed using a scanning electron microscope, it was found to be 0.1 to 0.2 μm.
It was found that it is made up of particles. Many of these particles were observed to be weakly bonded in places.

Example 2 (Synthesis of PbZrO ₃ ) 16.198 g of commercially available zirconium nitrate (99% purity), 19.973 g of special grade lead nitrate (99.5% purity) and 300 ml of pure water were mixed, and a mixture of Zr/Pb=1/1 (atomic ratio) was prepared. An aqueous solution with the following composition was obtained and maintained at 20°C.

Dissolve 11.403g of oxalic acid dihydrate (purity 99.5%) in 300ml of pure water (COOH) ₂ / (Pb + Zr) =
A dropwise aqueous solution containing 0.75 (mol/mol) oxalic acid was prepared and maintained at 20°C.

While stirring the aqueous solution vigorously, the dropwise aqueous solution was added at a rate of about 8 ml/min to obtain a white precipitate, which was suctioned through a Buchner Toto to separate the mother liquor to obtain a white cake.

The obtained white cake was washed with pure water using the method disclosed in Example 1, dried to obtain a white solid, and crushed in an agate mortar to obtain a precursor powder.

The obtained precursor powder was heated to 700° C. at a rate of 2° C./min in a Matsufuru furnace and then held for 2 hours to obtain the desired oxide powder.

The BET surface area of the obtained oxide powder is 9.2 m ² /g
It was hot. The average particle diameter calculated from this is 0.08μm
It was hot. By X-ray diffraction, the oxide is _PbZrO3
was the main component, and the presence of a small amount of ZrO ₂ was confirmed.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the particle size distribution of PbTiO ₃ particles.

Claims (1)

[Claims] 1 ABO ₃ type perovskite oxide (however,
A is Pb and B is at least one element selected from the group consisting of Ti and Zr. In the method of generating the oxalate precipitate and then thermally decomposing the precipitate to produce the oxide, the amount of the oxalic acid added per mole of element A (Pb) present in the aqueous solution is
0.96 to 1.04 mol, B elements (Ti and/or
A method for producing an ABO ₃ perovskite oxide, characterized in that the ratio is set at a ratio of 0.48 to 0.52 moles per mole of Zr). 2. Adding the amount of the oxalic acid present in the aqueous solution
Claim 1, characterized in that the ratio is set at 0.98 to 1.02 mol per mol of Pb and 0.49 to 0.51 mol per mol of Ti and/or Zr.
Production method of ABO ₃ type perovskite oxide. 3. Adding the amount of the oxalic acid present in the aqueous solution
A method for producing an ABO ₃ perovskite oxide according to claim 1, characterized in that the ratio is determined to be 0.99 to 1.01 mol per mol of Pb and 0.495 to 0.505 mol per mol of Ti and/or Zr. 4. The method for producing an ABO ₃ perovskite oxide according to claim 1, wherein the elements contained in the aqueous solution are supplied as nitrates.