JPH08183615A - Production of lead lanthanum titanite powder and production of thin lead lanthanum titanite film - Google Patents

Abstract

PURPOSE: To safely produce PbLaTiO3 powder rich in La in solid soln. with inexpensive La acetate at a low cost. CONSTITUTION: Acetates of Pb and La are mixed with an acetic acid solvent to prepare an acetic acid mixed soln. and Ti alkoxide is dissolved in an org. solvent to prepare an alkoxide soln. The solns. are mixed to prepare a Pb-La-Ti soln., this soln. is hydrolyzed and the resultant precipitate or gel is dried and heat-treated in an oxidizing atmosphere at 500-800 deg.C. The surface of a prescribed substrate is coated with the Pb-La-Ti soln. as a coating soln. and this soln. is heat-treated in an oxidizing atmosphere at 500-800 deg.C to obtain the objective tin PbLaTiO3 film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing PbLaTiO ₃ -based powder or a thin film thereof for use in electronic parts and optical elements.

[0002]

2. Description of the Related Art (Pb, La) TiO ₃ (hereinafter referred to as PLT) or (Pb, La) (Zr, Ti) O ₃
(Hereinafter referred to as PLZT) exhibits excellent piezoelectricity and a large electro-optical effect, and since transparent ceramics can be obtained, it is most widely applied in the field of electronic parts and optoelectronics.

In recent years, P has been developed by using the sputtering method, the CVD method, the sol-gel method, etc., with the aim of developing higher-performance devices.
Studies on thinning of LT and PLZT are also being conducted.

For example, the characteristics of PLZT greatly depend on the composition, and it is important to control the composition in order to obtain a film having desired characteristics. Among them, the sol-gel method is characterized by excellent composition controllability, and is the most suitable method for producing these thin films.

Therefore, in general, for example, PL is applied by the sol-gel method.
When a ZT thin film is prepared, Pb and La alkoxides are used as raw materials and an alcohol-based organic solvent such as 2-methoxyethanol is used to select a Pb-La composite alkoxide solution and Zr and Ti. Preparation of a Zr-Ti composite alkoxide solution in which each alkoxide is dissolved in an alcoholic solvent, mixing these composite alkoxide solutions to prepare a coating solution, and then coating and heat treating on a predetermined substrate surface. A PLZT-based thin film is obtained by.

[0006]

[Problems to be Solved by the Invention]
The cost of the La alkoxide used as a raw material a is high, and the cost tends to increase as the amount of La dissolved in solid solution increases. Therefore, although an inexpensive acetate salt (lanthanum acetate sesquihydrate) may be used as the La raw material, the solubility of the simple substance is low and it is difficult to form a solution. For example, S. K. Dey et al., Using lanthanum acetate sesquihydrate, (Pb _0.91 La _0.09 ) (Z
It has been reported that an r _0.65 Ti _0.35 ) O ₃ thin film was prepared (Br. Ceram. Proc., 36, 10).
7 (1985)). According to the report, lanthanum acetate sesquihydrate alone does not dissolve in 2-methoxyethanol solvent, but when mixed with lead acetate trihydrate, it dissolves up to 10 mol% at most. ing. Therefore, when lanthanum acetate sesquihydrate was used as the La raw material, it was difficult to produce a PLT or PLZT thin film in which La was 10 mol% or more in solid solution.

Further, Japanese Patent Application Laid-Open No. 4-214071 describes that La acetate is used and 2-methoxyethanol is used as a solvent to increase the solid solution amount of La. However, in this publication, when preparing a composite solution of PLT, a long reflux step is required as the solid solution amount of La is increased.

In addition, the two used in the prior art mentioned above.
-Methoxyethanol is a strong toxin known to cause genetic mutations in the human body, and therefore
Strict control is required when using it as a solvent.

Therefore, according to the present invention, Pb and La which can dissolve La at a high concentration by using inexpensive acetate as a La raw material
The present invention provides a method for inexpensively and safely producing a composite oxide powder or a thin film containing Ti.

[0010]

[Means for Solving the Problems] As a result of studying a method for solving the above problems, the present inventors have found that when the so-called sol-gel method is used, acetic acid is used as a solvent for dissolving the acetate thereof. In addition, even if lanthanum acetate sesquihydrate was used as a starting material, La was successfully dissolved in 10 mol% or more, whereby PLT containing high La content, PLZT perovskite crystals, or a single-phase thin film could be prepared. As a result, they have found the present invention.

That is, the method for producing the PbLaTiO ₃ -based powder of the present invention comprises the steps of preparing an acetic acid mixed solution prepared by mixing Pb acetate and La acetate with an acetic acid solvent, and using a Ti alkoxide as an organic solvent. A step of preparing an alkoxide solution dissolved in, a step of mixing the acetic acid mixed solution and the alkoxide solution, and adding water to the mixed solution to hydrolyze,
Dry the precipitate or gel after hydrolysis, and
And a step of performing heat treatment in an oxidizing atmosphere at 800 ° C.

Further, the method for producing a PbLaTiO ₃ -based thin film of the present invention comprises a step of preparing an acetic acid mixed solution prepared by mixing Pb acetate and La acetate with an acetic acid solvent, and a Ti alkoxide as an organic solvent. A step of preparing an alkoxide solution dissolved in, a step of preparing a coating solution by mixing the acetic acid mixed solution and an alkoxide solution, a step of coating the coating solution on a predetermined substrate surface, and a step of coating the coated product at 500 ° C. ~ 8
And a step of performing a heat treatment in an oxidizing atmosphere at 00 ° C.

The details will be described below. First, the production method of the present invention will be specifically described by using (Pb, La) TiO ₃ as an example. First, lead acetate and lanthanum acetate were used as raw material powders, and these were weighed at a predetermined molar ratio to obtain R ₁ COOH (R ₁ : an alkyl group having 1 or more carbon atoms).
It mixes with the solvent shown by. When the lead and lanthanum acetates contain water of crystallization, it is desirable to remove them by a method such as distillation before use. Specific examples of the solvent represented by R ₁ COOH (R ₁ : an alkyl group having 1 or more carbon atoms) include CH ₃ COOH (acetic acid) and CH ₃ CH ₂ COOH.
(Propionic _{acid), CH 3 CH 2 CH 2} COOH (n-
Butyric acid, iso-butyric acid) and the like, and of these, acetic acid is preferable.

Next, Ti (OR ₂ ) ₄ (R ₂ : carbon number 1
The titanium raw material represented by the above alkyl group) is converted into R ₁ COO.
H (R ₁ : alkyl group having 1 or more carbon atoms), R ₃ OH (R
₍₃ : Alkyl group having 2 or more carbon atoms), and then mixed with a solvent to produce a Ti-Zr composite alkoxide solution by refluxing. Examples of the solvent at this time include acetic acid, ethanol, isopropyl alcohol, and among these, acetic acid and isopropyl alcohol are preferably used. Specific examples of Ti (OR ₂ ) ₄ include tetraisopropoxy titanium.

Next, the prepared Pb-La acetic acid mixed solution and the Ti alkoxide solution are mixed so that the metal element ratio becomes equimolar, and sufficiently stirred at room temperature to obtain transparent Pb.
A solution containing La and Ti can be obtained.

Here, when producing PLT powder,
Excess water is added to the uniformly mixed solution containing Pb, La, and Ti to cause hydrolysis to form a hydroxide precipitate or a gel. After drying this, 500 ° C ~
By performing heat treatment at 800 ° C. in an oxidizing atmosphere such as air, a (Pb, La) TiO ₃ -based powder can be obtained.

When a thin film is prepared, the solution containing Pb, La, and Ti, which is uniformly mixed, is added to R ₁ COO.
H (R ₁ : an alkyl group having 1 or more carbon atoms) or sufficiently dehydrated methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, or other R ₅ OH (R
₅ : It is desirable to dilute with a solvent having an alkyl group having 1 or more carbon atoms to obtain a coating solution.

Then, this coating solution is used to coat a predetermined substrate surface by a known coating method such as a dipping method or a spin coating method.

After coating on the surface of the substrate and before firing, it is desirable to perform a heat treatment operation on the coating film at 200 ° C. or higher to thermally decompose the organic matter to form a gel film. At this time, if the heat treatment temperature is lower than 200 ° C., the thermal decomposition of organic substances in the film is insufficient, and the film may be cracked during the subsequent firing. Then, a gel film having a desired thickness is produced by appropriately repeating the above-mentioned coating and heat treatment.

The gel film obtained as described above is used for 500
The gel film can be crystallized by baking at ˜800 ° C., whereby a (Pb, La) TiO ₃ thin film can be obtained. At this time, if the temperature during firing is lower than 500 ° C., crystallization is not performed, and if it exceeds 800 ° C., grain growth occurs and a thin film having a uniform structure cannot be obtained.

As the substrate material used for forming the thin film, sapphire, Pt, quartz glass and the like can be mentioned. Among them, sapphire is preferably used for enhancing the crystallinity of the thin film.

The preparation of the (Pb, La) TiO ₃ powder or its thin film has been specifically described above. Of course, (Pb, La) (Ti, Zr) O ₃ and other Pb,
Powders of known compounds in which a part of La, Ti, or Zr is substituted with another metal element, or thin films thereof can be prepared by the same method.

When a powder or thin film of PLZT is produced, Zr (OR ₄ ) ₄ (R ₄ : carbon number 1 is used as a Zr raw material.
The Zr alkoxide represented by the above alkyl group) is used, and this is added and dissolved in the same organic solvent as the above together with the above Ti alkoxide, and then this is heated at 80 to 110 ° C.
Ti-Zr by refluxing for about 1 to 24 hours
Complex alkoxide solutions can be prepared. The Ti-Zr composite alkoxide solution thus obtained was mixed with the above Pb-La acetic acid mixed solution to obtain Pb-La-
A solution containing Zr-Ti is prepared, and thereafter, a powder or a thin film can be produced in exactly the same manner as above.
Examples of Zr (OR ₄ ) ₄ used at this time include tetrapropoxyzirconium.

According to the above-mentioned method of the present invention, it is possible to produce PLT or PLZT powder in which 1 to 30 atomic% of La is dissolved in Pb, or a thin film thereof.
The specific composition is (Pb _1-X La _X ) (Ti _1-Y Z
r _Y ) O ₃ (wherein 0.01 ≦ X ≦ 0.3, 0 ≦ Y ≦
A compound having a high La content of 0.85) can be synthesized.

[0025]

According to the method of the present invention, the expensive La alkoxide conventionally used as the La raw material is replaced by the La acetate, and the highly toxic 2-methoxyethanol conventionally used as the solvent for the La acetate. By using a non-toxic acetic acid in place of -al, the solubility of La acetate in a solvent can be increased and it can be safely used. As a result, PL containing high La
A powder or thin film of T or PLZT can be manufactured inexpensively and safely.

Moreover, according to the method of the present invention, Pb-L
a Acetic acid mixed solution and Ti alkoxide solution or Ti
-Pb and L can be obtained by simply mixing the Zr alkoxide solution.
Since a solution containing a, Ti and Zr can be obtained and no special reflux operation is required, the process can be simplified.

Therefore, since the powder or thin film of PLT or PLZT having a high La content can be manufactured by a simple operation using an inexpensive raw material, the manufacturing cost of such powder or thin film can be reduced.

[0028]

【Example】

Example 1 Molar ratio Pb: La: Ti = 0.72: 0.28: 1.0
A PLT thin film and a powder having a La substitution amount of 28 at.

As a raw material, lead acetate trihydrate 7.2 mmo
1, and 2.8 mmol of lanthanum acetate 1.5 hydrate were dissolved in 100 mmol of acetic acid by heating, and then distilled under atmospheric pressure at 100 ° C. to remove water of crystallization. After removing the water of crystallization, the mixture was cooled to room temperature, and an amount of acetic acid solvent reduced by distillation was added to prepare a transparent Pb-La acetic acid mixed solution. On the other hand, 10 mmol of isopropoxy titanium was mixed with 100 mmol of acetic acid to prepare a Ti alkoxide solution.

Then, Pb-prepared as described above
The La acetic acid mixed solution and the Ti alkoxide solution were mixed so that the metal atom ratio was 1: 1.
A -La-Ti solution was made. The fact that this solution is transparent means that these metal compounds are uniformly mixed.

(Synthesis of Thin Film) Next, the concentration of this solution was diluted 5 times with acetic acid to prepare a coating solution. Spin this
Coated on a sapphire R substrate with a tape, dried at room temperature, and then heat-treated at 250 ° C. for 5 minutes to form a gel film. This coating-heat treatment operation was repeated 10 times to obtain a film thickness of 0.
A 2 μm gel film was prepared. Then, this gel film was crystallized by firing at 700 ° C. for 2 hours in an oxygen stream. X-ray diffraction measurement was performed on the obtained film, and the results are shown in FIG. From the results of FIG. 1, it was confirmed that the perovskite single-phase PLT thin film having the cubic structure was obtained. Further, the (110) oriented film was largely oriented in the <110> direction due to the symmetry of the atomic arrangement of the substrate. Also,
This X-ray diffraction measurement result was the X-ray diffraction result of the same pattern as the thin film prepared using isopropoxy lanthanum (La alkoxide) as the La raw material.

By the way, FIG. 2 shows the X-ray diffraction measurement results of the PbTiO ₃ thin film formed on the sapphire R substrate. P
According to the LZT phase diagram, the crystal structure changes from a tetragonal structure to a cubic structure as the solid solution amount of La increases. The crystal structure of the PLT thin film of FIG. 1 in which La is solid-solved at 28 atomic% has a cubic structure. Therefore, from the results of FIG. 1, separation of (110) and (101) peaks was not observed, and a PLT thin film having a cubic crystal structure was obtained.
It was confirmed to be a PLT thin film in which all atomic% was solid-solved.

(Synthesis of powder) The above transparent Pb-La-
When 20 times the amount of water was added to the Ti solution to cause hydrolysis, precipitation of hydroxide was observed. This is 6
After drying at 0 ° C., heat treatment was performed at 700 ° C. for 2 hours in an oxygen stream, and as a result, white powder was obtained. As a result of X-ray diffraction measurement of the obtained powder, it was found that the powder was a perovskite single phase having a cubic structure, and from this, (Pb _0.72
It was confirmed that the powder was La _0.28 TiO ₃ powder.

Example 2 Molar ratio Pb: La: Zr: Ti = 0.72: 0.28:
PLZT thin films and powders having a composition of 0.5: 0.5 and having a La substitution amount of 28 atomic% for Pb were prepared as follows.

As a raw material, lead acetate trihydrate 7.2 mmo
1, and 2.8 mmol of lanthanum acetate 1.5 hydrate were dissolved in 100 mmol of acetic acid by heating, and then distilled under atmospheric pressure at 100 ° C. to remove water of crystallization. After removing the water of crystallization, the mixture was cooled to room temperature, and an amount of acetic acid solvent reduced by distillation was added to prepare a transparent Pb-La acetic acid mixed solution. On the other hand, after 10 mmol of isopropoxy titanium and 10 mmol of tetrapropoxy zirconium were mixed with 100 mmol of acetic acid, a reflux treatment was performed at a solution temperature of 100 ° C. for 3 hours, and Ti-
A composite alkoxide solution of Zr was prepared.

Then, Pb-prepared as described above
When the La acetic acid mixed solution and the Ti-Zr composite alkoxide solution were mixed so that the metal atom ratio was 1: 1,
A clear Pb-La-Zr-Ti solution was made.

(Synthesis of Thin Film) Next, the concentration of this solution was diluted 5 times with acetic acid to prepare a coating solution. Spin this
Coated on a sapphire R substrate with a tape, dried at room temperature, and then heat-treated at 250 ° C. for 5 minutes to form a gel film. This coating-heat treatment operation was repeated 10 times to obtain a film thickness of 0.
A 2 μm gel film was prepared. Then, this gel film was crystallized by firing at 700 ° C. for 2 hours in an oxygen stream. As a result of X-ray diffraction measurement of the obtained film, it was confirmed to be a PLZT thin film having a cubic perovskite single phase and having a (110) orientation as in FIG.

(Synthesis of powder) 20 times equivalent amount of water was added to the transparent Pb-La-Ti-Zr solution obtained above to cause hydrolysis, and precipitation of hydroxide was observed. It was After drying this at 60 ℃, in an oxygen stream,
As a result of heat treatment at 700 ° C. for 2 hours, a white powder was synthesized. As a result of X-ray diffraction measurement on the obtained powder, the powder was a perovskite single phase having a cubic structure,
From this, (Pb _0.72 La _0.28 ) (Ti _0.5 Zr
_0.5 ) O ₃ powder was confirmed.

[0039]

As described above, according to the present invention, high L
A solid solution PLT or PLZT powder or thin film can be produced at low cost and safely using inexpensive La acetate.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction measurement result of a PLT thin film manufactured in Example 1.

FIG. 2 is an X-ray diffraction measurement result of a PbTiO ₃ thin film.

Claims (2)

[Claims] 1. PbL having a perovskite structure containing at least Pb, La and Ti as metal elements.
A method for producing an aTiO ₃ -based powder, comprising the steps of preparing an acetic acid mixed solution prepared by mixing an acetic acid salt of Pb and an acetic acid salt of La with an acetic acid solvent; and an alkoxide in which an alkoxide of Ti is dissolved in an organic solvent. A step of preparing a solution, a step of mixing the acetic acid mixed solution and an alkoxide solution, a step of adding water to the mixed solution to hydrolyze, and a precipitate or gel after hydrolysis is dried to 500 ° C to 800 ° C. Heat treatment in an oxidizing atmosphere at 0 ° C.
Manufacturing method of bLaTiO ₃ powder. 2. PbL having a perovskite structure containing at least Pb, La and Ti as metal elements.
A method for producing an aTiO ₃ -based thin film, comprising the steps of preparing an acetic acid mixed solution obtained by mixing Pb acetate and La acetate in an acetic acid solvent; and an alkoxide in which a Ti alkoxide is dissolved in an organic solvent. A step of preparing a solution, a step of mixing the acetic acid mixed solution and an alkoxide solution to prepare a coating solution, a step of coating the coating solution on a predetermined substrate surface, and a step of coating the coated material at 500 ° C to 800 ° C. PbLaTiO comprising a step of heat treatment in an oxidizing atmosphere
₃ system thin film manufacturing method.