JP3099568B2 - Method for producing lead titanate thin film - Google Patents

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 lead titanate.

[0002]

2. Description of the Related Art Lead titanate has excellent properties as a ferroelectric material, a piezoelectric material or a pyroelectric material, and has been widely applied to ceramic capacitors, actuators, pyroelectric infrared sensors and the like. When applied to these uses,
The use of lead titanate as a thin film has become popular with the miniaturization and high performance of electronic equipment. For example, a sputtering method (Japanese Patent Publication No. Sho 62-4)
No. 1311), CVD (JP-A-63-178408), vacuum deposition method (JP-A-1-74778), cluster ion beam method (JP-A-1-222046), plasma method (Japanese Patent Laid-Open No. 2-57686), a coating baking method (Japanese Patent Application Laid-Open No. 60-236404), and a melt method of rapidly cooling the melt to form a thin film (Japanese Patent Application Laid-Open No. 60-847).
No. 12).

[0003]

However, gas phase methods such as sputtering, CVD, and vacuum deposition require complicated and expensive equipment, and the material of the base material is restricted because of forming a film at a high temperature. In addition, since the substrate is exposed to the flow of the source gas, there are problems such as a complicated shape and film formation on the back side of the substrate. The coating and baking method has a problem that it is necessary to repeat coating and baking, the operation is complicated, and it cannot be applied to a substrate having a complicated shape. The method of forming a thin film by quenching the melt has a problem in that heat resistance is required and the material of the base material is significantly limited.

Accordingly, an object of the present invention is to produce a large area lead titanate thin film at low cost without being restricted by the shape and material of the substrate.

[0005]

According to the present invention, as a means for solving the above-mentioned problems, a composite alkoxide is formed from lead carboxylate and a titanium alkoxide, and a base material is immersed in an aqueous solution of the composite alkoxide. Is formed into a thin film on the substrate surface by hydrolysis of Further, the present invention provides a method of forming a lead-titanium composite alkoxide by reacting a lead carboxylate and a titanium alkoxide, modifying the composite alkoxide with an amino alcohol, and then immersing the substrate in an aqueous solution of the amino alcohol-modified composite alkoxide. Then, a thin film is formed on the surface of the substrate by hydrolysis of the composite alkoxide, and this is heat-treated.

As the lead carboxylate, a lower carboxylate having a carbon number of 10 or less, preferably 6 or less is suitable, for example, lead acetate, lead propionate, lead butyrate, lead caproate, lead caprylate and the like. No. This lead carboxylate may be added to the titanium alkoxide solution as it is, or dissolved in the same solvent as the solvent used to dissolve the titanium alkoxide to form a solution, and the solution is mixed with the alkoxide solution. May be.

As the titanium alkoxide, any one can be used, but an alkoxy group having 15 or less, preferably 6 or less carbon atoms is desirable. Typical examples are titanium ethoxide, titanium isobutoxide (Ti
(OC ₄ H ₉ ) ₄ ), titanium isopropoxide (Ti (O
C ₃ H _{7) 4),} dibutoxy - ditolyl ethanol - aminate titanium, dibutoxy - di (2- (hydroxyethylamino) ethoxy) titanium _{(Ti (C 4 H 9 O} ) 2 · [N
(C ₂ H ₄ OH) _2. (C ₂ H ₄ O) ₂ ]) and the like, but are not limited thereto.

[0008] As a solvent for producing the complex alkoxide, ethylene glycol monoalkyl ether (R
OCH ₂ CH ₂ OH) is preferably used. The ethylene glycol monoalkyl ether includes ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono n-propyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono n-butyl ether, ethylene glycol phenyl Ether, etc., and in the trade name,
Methyl cellosolve, ethyl cellosolve and the like can be mentioned.

As the amino alcohol, any one can be used. Representative examples thereof include β-aminoethyl alcohol, β-aminopropyl alcohol, and triethanolamine.

As the substrate, alumina, ceramics or any other material may be used. The concentrations of lead and titanium in the aqueous solution for film formation are 0.01 mM / l or more, respectively.
Preferably it is 100 mM / l. This is because when the concentration of lead and titanium contained in the aqueous solution for film formation is less than 0.01 mM / l, the lead titanate is discretely precipitated in the form of islands to form no film, and when the concentration exceeds 100 mM / l, This is because precipitation occurs, nucleation using the substrate surface does not occur, and a dense film cannot be obtained. In this case, it is preferable to carry out the reaction while maintaining the temperature of the aqueous solution within the range of 0 to 110 ° C. If the liquid temperature is lower than 0 ° C., the deposition rate becomes extremely slow and a film is not formed, and if the liquid temperature exceeds 110 ° C., air bubbles adhere to the surface of the substrate and the film formed on the surface of the substrate becomes continuous. Because sex is lost. Further, the heat treatment of the lead titanate thin film formed on the substrate surface is preferably performed at a temperature of 400 to 750 ° C. This is because when the heat treatment temperature is less than 400 ° C,
Because the amorphous phase or the pyrochlore phase is transformed, a ferroelectric thin film cannot be obtained. If the temperature exceeds 750 ° C., needle-like crystals of lead titanate grow and the smoothness and homogeneity of the film are lost. .

[0011]

When ethylene glycol monoalkyl ether having an alcoholic hydroxyl group and an ether bond is used as a solvent and a lead carboxylate is reacted with a titanium alkoxide in the solution, a complex alkoxide of lead and titanium is formed. This is denatured with amino alcohol, this is dissolved in water to prepare an aqueous solution for film formation, and the substrate is immersed in the aqueous solution and gradually hydrolyzed. Nuclei are formed, and as the hydrolysis proceeds, the nuclei grow,
It becomes a film. By subjecting this film to heat treatment, a lead titanate thin film is formed.

[0012]

EXAMPLE 0.5 mol of lead acetate (hereinafter referred to as M) was dissolved in 4M of methyl cellosolve, water was completely evaporated at about 110 ° C., then cooled to about 50 ° C., and 0.5M was added thereto. Of tetraisopropyl titanate, and reacted at about 100 ° C. for 1 hour. The reaction mixture contains 2M triethanolamine.
And the alkoxyl group is substituted with an aminotriethoxy group by alcoholysis to obtain a triethanolamine-modified lead-titanium composite alkoxide.

The obtained triethanolamine-modified lead-titanium composite alkoxide was dissolved in ion-exchanged water to a concentration shown in Table 1 to obtain an aqueous solution, and the aqueous solution was mirror-polished to a size of 10 × 15 × 2 mm. When the alumina sintered body substrate was immersed and kept at the temperature shown in Table 1 for 4 days, a thin film was formed on each substrate except for Samples 1 and 2. Each thin film was heat-treated in air at the temperature shown in Table 1 for 1 hour.

[0014]

[Table 1] No. Pb (II) Liquid temperature Heat treatment temperature (mM / l) (° C) (° C) * 1 0.005 110 500 * 2 100 115 500 3 0.01 110 400 4 0.1 100 500 5 1 40 600 600 5 700 7 100 0 750

When a thin film formed on the surface of each substrate was analyzed by X-ray diffraction, any of Samples 3 to 6 showed the results shown in FIG.
The results similar to those of the thin film X-ray diffraction pattern of Sample 6 shown in Fig. 6 were obtained, and it was confirmed that the sample 6 was a tetragonal crystal perovskite-type lead titanate. In addition, in the case of Sample 1, only a film in which lead titanate was discretely precipitated in an island shape was obtained, and in the case of Sample 2, a precipitate was formed and a thin film was not obtained.

[0016]

As is apparent from the above description, the present invention is to produce a composite alkoxide from a lead carboxylate and a titanium alkoxide, hydrolyze the composite alkoxide, and apply it to the surface of the substrate immersed in the liquid. Since a thin film is deposited and heat-treated to form a lead titanate thin film, a uniform thin film can be manufactured without being affected by the material and shape of the substrate, and the heat treatment can be performed at a low temperature. Therefore, unlike the conventional dry method, there is no loss due to evaporation of lead at the time of sintering, and a large area thin film having a desired composition without deviation in molar ratio can be easily and inexpensively manufactured. Play.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of a lead titanate thin film according to the method of the present invention.

Claims (5)

(57) [Claims] 1. A composite alkoxide is formed from a lead carboxylate and a titanium alkoxide, a substrate is immersed in an aqueous solution of the composite alkoxide, and a thin film is formed on the surface of the substrate by hydrolysis of the composite alkoxide. A method for producing a lead titanate thin film. 2. The method according to claim 1, wherein said lead carboxylate and titanium alkoxide are reacted in the presence of ethylene glycol monoalkyl ether to form a composite alkoxide. 3. The method according to claim 1, wherein an aqueous solution is prepared after denaturing the complex alkoxide with an amino alcohol. 4. The concentration of lead and titanium in said composite alkoxide aqueous solution is determined by comparing Pb (II) and Ti
(IV) 0.01 mM / l ≦ Pb (II) <100 mM / l,
2. The method according to claim 1, wherein 0.01 mM / l ≦ Ti (IV) <100 mM / l.
The described method. 5. The thin film formed on the surface of the base material is
The method according to claim 1, wherein the heat treatment is performed at a temperature of 0 to 750C.