JP4603254B2 - Method for producing metal oxide sol liquid, crystalline metal double oxide sol and metal oxide film - Google Patents

Description

  The present invention relates to a method for producing a metal oxide sol solution capable of forming a dense and homogeneous metal oxide film free from cracks, a crystalline metal double oxide sol, and a metal oxide film using the metal oxide sol solution.

  Ferroelectric materials such as barium titanate are widely used in the field of electronic devices including capacitors and memory materials. In recent years, electronic devices have been further reduced in size and performance, and establishment of a manufacturing technique for a ferroelectric thin film having higher performance and higher quality ferroelectric characteristics has been demanded.

  As a conventional method for producing a ferroelectric thin film, a liquid phase represented by a PVD method such as sputtering, a gas phase method such as a chemical vapor deposition method (CVD method) using an organometallic compound, or a sol-gel method. Laws are known. Among them, the thin film forming method by the sol-gel method is not easy to be restricted by the shape and size of the substrate on which the thin film is formed and because it does not require an expensive apparatus or high energy for forming the thin film. It has attracted particular attention.

  As a conventional method for forming a thin film by a sol-gel method, for example, Patent Document 1 discloses that metal is used in an organic solvent containing an alkoxy alcohol by using 0.1 to 10 moles of water with respect to the metal alkoxide. A method is disclosed in which a coating liquid for forming an oxide thin film is obtained by hydrolyzing an alkoxide, the coating liquid is coated on a substrate and baked at a low temperature. However, since the hydrolysis reaction of the metal alkoxide is not completed in this method, weight loss occurs when the resulting coating solution is applied onto a substrate and baked, and a monodisperse dense and homogeneous thin film is obtained. It was difficult.

  Patent Document 2 discloses that a high-concentration sol solution of a metal alkoxide is hydrolyzed at a low temperature, and the resulting crystalline gel is dispersed in an organic solvent to prepare a coating solution. A method of applying and baking at a low temperature is disclosed. However, in this method, when the crystalline gel is dispersed, the crystalline gel becomes a slurry or a lump, and mechanical pulverization or the like may be necessary to uniformly disperse the crystalline gel. Moreover, since this method hydrolyzes at a relatively high concentration, there is a problem that mixing of reactants becomes insufficient and the hydrolysis reaction may not proceed smoothly.

JP 2001-233604 A JP 2002-275390 A

  The present invention has been made in view of the actual situation of the prior art, and is a method for producing a metal oxide sol liquid capable of forming a dense and homogeneous metal oxide film free from cracks, a crystalline metal double oxide sol, and the above-mentioned It is an object to provide a metal oxide film formed using a metal oxide sol solution.

  In order to solve the above-mentioned problems, the present inventors diligently studied a method for producing a metal oxide sol solution for forming a metal oxide film. As a result, when water is added to the organic solvent solution of the metal alkoxide to hydrolyze the metal alkoxide, the concentration of the metal oxide sol obtained is 5% by weight or less in terms of metal oxide. When the concentration of the metal alkoxide in the organic solvent solution is set, a solution of a metal oxide sol that is monodispersed and has a small weight loss even when heated to 300 ° C. or higher can be obtained. The present inventors have found that a dense and homogeneous metal oxide film can be formed without any defects, and the present invention has been completed.

  Thus, according to the first aspect of the present invention, the method includes the step of hydrolyzing the metal alkoxide by adding 3 to 10 moles of water to the metal alkoxide in an organic solvent solution in which one or more metal alkoxides are dissolved. A method for producing a metal oxide sol solution, wherein the organic oxide sol solution has a concentration of 5% by weight or less in terms of metal oxide in a reaction solution obtained by hydrolyzing a metal alkoxide. There is provided a method for producing a metal oxide sol solution, characterized in that the concentration of metal alkoxide in a solvent solution is set.

In the method for producing a metal oxide sol solution of the present invention, a metal oxide sol solution having a concentration of 25 to 45% by weight in terms of metal oxide sol is obtained by concentrating the reaction solution. It is preferable to further have the process of obtaining.
In the method for producing a metal oxide sol solution of the present invention, it is preferable to use water obtained by degassing dissolved carbon dioxide gas.

In the method for producing a metal oxide sol solution of the present invention, it is preferable to obtain a metal oxide sol solution having a monodisperse particle size distribution having a peak at 5 to 20 nm.
In the method for producing a metal oxide sol solution of the present invention, it is preferable to obtain a metal oxide sol solution having a thermogravimetric change of less than 10% by weight when heated from 150 ° C. to 700 ° C.
In the method for producing a metal oxide sol solution of the present invention, the particle size distribution is monodisperse having a peak at 5 to 20 nm, and the thermogravimetric change when heated from 150 ° C. to 700 ° C. is less than 10% by weight. It is particularly preferred to obtain a metal oxide sol solution which is

In the method for producing a metal oxide sol solution of the present invention, it is preferable to obtain a metal oxide sol solution in which the metal oxide is crystalline.
In the method for producing a metal oxide sol solution of the present invention, it is preferable to obtain a metal oxide sol solution in which the metal oxide is a perovskite compound.
Moreover, in the manufacturing method of the metal oxide sol solution of the present invention, the organic solvent solution is made of an organic solvent made of a metal selected from Groups 2, 3, 8-12, 14, and 15 of the long-period periodic table. It is preferable to use a solution in which an alkoxide and a metal alkoxide selected from Groups 4, 14, and 15 of the long-period periodic table are dissolved.

According to the second aspect of the present invention, there is provided a crystalline metal double oxide sol whose particle size distribution is monodisperse having a peak at 5 to 20 nm.
The crystalline metal double oxide sol of the present invention preferably has a thermogravimetric change of less than 10% by weight when heated from 150 ° C. to 700 ° C., and the particle size distribution is monodispersed with a peak at 5 to 20 nm. Further, it is more preferable that the thermogravimetric change when heated from 150 ° C. to 700 ° C. is less than 10% by weight.
The crystalline metal double oxide sol of the present invention is preferably such that the crystalline metal double oxide is a perovskite compound.
According to a third aspect of the present invention, there is provided a metal oxide film formed from a metal oxide sol solution produced by the production method of the present invention.

According to the method for producing a metal oxide sol liquid of the present invention, a transparent and homogeneous metal oxide sol solution can be easily produced.
The metal oxide sol solution obtained in the present invention is stable even when concentrated, and can be redissolved in a solvent.
The crystalline metal double oxide sol of the present invention is useful as a material for forming dielectric thin films, conductor thin films, piezoelectric thin films, semiconductor thin films and the like.
By using the metal oxide sol solution obtained in the present invention, a dense and homogeneous metal oxide film free from cracks and the like can be formed.
The metal oxide film of the present invention can be widely used in the field of electronic devices as a dielectric thin film, a conductor thin film, a piezoelectric thin film, a semiconductor thin film, and the like.

Hereinafter, a method for producing a metal oxide sol solution of the present invention, a crystalline metal double oxide sol, and a metal oxide film using the metal oxide sol solution will be described in detail.
1) Method for Producing Metal Oxide Sol Solution The method for producing the metal oxide sol solution of the present invention comprises adding 3 to 10 moles of water to an organic solvent solution in which one or more metal alkoxides are dissolved. A method for producing a metal oxide sol liquid comprising adding and hydrolyzing the metal alkoxide, wherein the concentration of the metal oxide sol in the reaction liquid obtained by hydrolyzing the metal alkoxide is reduced to the metal oxide. The concentration of the metal alkoxide in the organic solvent solution is set so as to be 5% by weight or less in terms of conversion.

The metal alkoxide of one or more metal alkoxides used in the present invention is not particularly limited as long as it can produce a metal oxide sol solution by hydrolysis in an organic solvent solution.
Examples of the metal of the metal alkoxide include metals selected from Groups 2-4, 8-12, and 14-16 of the long-period periodic table. Although there is no restriction | limiting in particular as an alkoxy group of a metal alkoxide, From viewpoints, such as availability and a hydrolysis reactivity, a C1-C4 alkoxy group is preferable.

As the metal alkoxide, both a single metal alkoxide containing a single metal atom and a composite metal alkoxide containing a plurality of types of metal atoms can be used.
Specific examples of single metal alkoxides include barium alkoxides such as barium dimethoxide, barium diethoxide, barium dipropoxide, barium dibutoxide; titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetrabutoxide Titanium alkoxides such as triethoxy yttrium and triisopropoxy yttrium; lanthanum alkoxides such as triethoxy lanthanum and triisopropoxy lanthanum; strontium alkoxides such as diethoxy strontium and diisopropoxy strontium;

  Specific examples of the composite metal alkoxide include barium titanium alkoxide such as barium titanium methoxide, barium titanium ethoxide, barium titanium propoxide, barium titanium butoxide; strontium titanium methoxide, strontium titanium ethoxide, strontium titanium propoxide, strontium titanium Strontium titanium alkoxides such as butoxide; and the like.

These single metal alkoxides and composite metal alkoxides can be used singly or in combination of two or more.
In the present invention, it is preferable to use two or more metal alkoxides, and it is more preferable to use a combination of titanium alkoxide and alkaline earth metal alkoxide. Specific examples include a combination of titanium alkoxide and barium alkoxide, a combination of titanium alkoxide, barium alkoxide, and strontium alkoxide. When two or more metal alkoxides are used, a thin film of a double oxide (an oxide composed of a plurality of metals) can be formed from the obtained metal oxide sol solution. In particular, a metal alkoxide selected from Groups 2, 3, 8-12, 14, and 15 of the long periodic table, and a metal alkoxide selected from Groups 4, 14, and 15 of the long periodic table. When used in combination, a sol solution of a perovskite compound from which a ferroelectric film having excellent physical properties can be obtained can be obtained.

  The concentration of the metal alkoxide in the organic solvent solution can be set to an arbitrary value. However, in the present invention, the concentration of the metal oxide sol in the reaction solution obtained by hydrolyzing the metal alkoxide is the metal oxide. It is set to be 5% by weight or less in terms of conversion. Thus, by setting the metal alkoxide concentration low, the reactants are uniformly mixed in the solvent, the hydrolysis reaction can proceed smoothly, and a monodispersed dense and homogeneous metal oxide sol solution is obtained. be able to.

The organic solvent for dissolving the metal alkoxide is not particularly limited as long as it dissolves the metal alkoxide. Specifically, alcohol solvents such as methanol and ethanol; 2-methoxymethanol, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol, 3-methoxy Alkoxyalkyl alcohol solvents such as propanol, 3-ethoxypropanol, 4-methoxybutanol, 4-ethoxybutanol, 4-propoxybutanol; Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone; Chlorine solvents such as methylene chloride and chloroform Solvents; hydrocarbon solvents such as hexane, cyclohexane, benzene, toluene, xylene, chlorobenzene; aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, etc. And the like.
These solvents can be used alone or in combination of two or more.

  Among these, metal alkoxides selected from groups 2, 3, 8-12, 14 and 15 of the long periodic table, and metal alkoxides selected from groups 4, 14 and 15 of the long periodic table Are preferably used in combination with alcohol solvents such as methanol and ethanol; and / or alkoxyalkyl alcohol solvents such as 2-methoxymethanol, 2-methoxyethanol and 2-ethoxyethanol. It is more preferable to use a mixed solvent of an alkoxyalkyl alcohol solvent. When a mixed solvent of an alcohol solvent and an alkoxyalkyl alcohol solvent is used, the mixing ratio is not particularly limited, but is usually a volume ratio of alcohol solvent: alkoxyalkyl alcohol solvent = 1: 100 to 100: 1, preferably Is 20: 80-80: 20. In the present invention, it is particularly preferable to use a mixed solvent composed of methanol and methoxyethanol.

Although there is no restriction | limiting in particular in the water used by this invention, In order to obtain a homogeneous metal oxide film with few impurities, purified water, such as distilled water and ion exchange water, is preferable.
In the present invention, it is more preferable to use water obtained by degassing dissolved carbon dioxide gas. By using water from which the dissolved carbon dioxide gas has been degassed, it is possible to prevent the metal carbonate from being precipitated in the reaction solution. Examples of a method for obtaining water from which dissolved carbon dioxide gas has been degassed include a method of boiling water, a method of bubbling an inert gas such as nitrogen gas and argon gas, and the like.
The usage-amount of water will not be restrict | limited especially if it is 3-10 times mole with respect to the metal alkoxide to be used, It can select arbitrarily by the reactivity etc. of the metal alkoxide to be used.

Moreover, since local reaction at the time of dripping can be suppressed and a homogeneous hydrolysis of a metal alkoxide can be performed, it is preferable to dilute and use water with an organic solvent.
As a solvent for dilution, a solvent compatible with water is preferable, and it may be the same as or different from the organic solvent used for dissolving the metal alkoxide. Examples thereof include alcohol solvents such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and n-butyl alcohol; alkoxyalkyl alcohol solvents such as 2-methoxymethanol, 2-methoxyethanol, and 2-ethoxyethanol.

A predetermined amount of water is added to the organic solvent solution of the metal alkoxide, and after completion of the addition, the entire volume is stirred at a predetermined temperature to advance the hydrolysis reaction of the metal alkoxide.
The reaction temperature is not particularly limited, but is usually in the range of −50 ° C. to + 100 ° C., preferably 0 ° C. to the reflux temperature of the organic solvent. The stirring time is usually several minutes to several days, preferably tens of minutes to several hours.

  In the present invention, the reaction is preferably aged by allowing the reaction solution to stand at room temperature for several hours to several days after completion of stirring. By aging the reaction solution, a more homogeneous and transparent metal oxide sol solution can be obtained.

  In the present invention, the hydrolysis reaction is carried out at a low concentration so that the reaction proceeds homogeneously and completely, and after completion of the hydrolysis reaction, the sol solution is concentrated to a concentration suitable as a metal oxide sol solution for coating. The method is preferably adopted. Specifically, the metal oxide sol solution obtained above is concentrated, and the metal oxide sol concentration is 25 to 45% by weight, preferably 30 to 40% by weight in terms of metal oxide. An oxide sol solution is preferred.

In order to minimize the damage to the substrate caused by heating the substrate coated with the metal oxide sol solution and maintain the quality of the metal oxide film, the amount of organic solvent contained in the metal oxide sol solution is: It is better to have as few as possible from the beginning. On the other hand, if the concentration is too high, the homogeneity of the sol solution is lost and the coating operation becomes difficult, which is not preferable. Considering these, the concentration of the metal oxide sol solution for forming the metal oxide film is preferably 25 to 45% by weight, preferably 30 to 40% by weight in terms of the metal oxide.
The method for concentrating the metal oxide sol solution obtained by the hydrolysis reaction of the metal alkoxide is not particularly limited, and a normal concentration method can be adopted.

  The metal oxide sol liquid obtained by the production method of the present invention is transparent and homogeneous, and the metal oxide sol liquid is concentrated to a metal oxide sol liquid concentration of 25 to 45% by weight in terms of metal oxide. The product sol solution is also transparent and homogeneous.

The metal oxide sol solution obtained by the production method of the present invention contains a monodispersed metal oxide sol having a narrow particle size distribution and having a single peak at 5 to 20 nm, preferably 7 to 13 nm.
The particle size distribution of the metal oxide sol in the metal oxide sol liquid can be measured by, for example, a non-contact backscattering optical technique.

  The metal oxide sol solution obtained by the production method of the present invention is obtained by almost completing the hydrolysis reaction of the metal alkoxide, so there is little residual alkoxy group, and there is almost no weight loss even when heated at high temperatures. Absent. The thermogravimetric change when this metal oxide sol solution is heated from 150 ° C. to 700 ° C. by TGA (Thermal Gravity Analysis) is less than 10% by weight, preferably less than 5% by weight.

  The metal oxide sol solution obtained by the method for producing a metal oxide sol solution of the present invention is monodispersed with a single peak at a particle size distribution of 5 to 20 nm, and heat when heated from 150 ° C. to 700 ° C. Particularly preferred are those containing a metal oxide sol whose weight change is less than 10% by weight.

2) Crystalline metal double oxide sol The second aspect of the present invention is a crystalline metal double oxide sol. The crystalline metal double oxide sol of the present invention is preferably a metal oxide sol contained in a metal oxide sol liquid obtained by the production method of the present invention.
The crystalline metal double oxide sol of the present invention is a crystalline metal double oxide sol, preferably a sol of a compound having a perovskite structure (perovskite compound).

  The metal double oxide is an oxide composed of two or more metals. Crystalline means that the atomic groups constituting the metal double oxide are regularly arranged. Whether or not the metal double oxide is crystalline can be analyzed by X-ray diffraction.

The perovskite structure is a kind of crystal structure that can be taken by the metal double oxide, and the perovskite compound is a compound that can be represented by the formula: M1M2O ₃ (wherein M1 and M2 each represent a metal atom). .

Formula: As the M1 metal in M1M2O _3, it is preferable to contain at least one or more selected from the 2,3,8～12,14 and group 15 of the long form periodic table of the elements, specifically Cu, Mg, Ca, Sr, Ba, Zn, Cd, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb Bi, Fe, Co, Ni and the like. Further, the M2 metal preferably contains at least one selected from Groups 4, 14 and 15, and specifically includes Ti, Zr, Hf, Sn, Sb and the like.

Formula: As the perovskite compound represented by M1M2O _3, i) that part of the metal M1 is replaced by the replaceable one or more other metals, ii) a part of the metal M2 is replaceable Iii) A part of the metal M1 is replaced with one or more other replaceable metals, and a part of the metal M2 is one or more replaceable It may be replaced with another metal. For example, in the case of BaTiO ₃ (barium titanate), the formula: (Ba _1-X Sr _X ) TiO ₃ or the formula: (Ba _1-X′-YZ Sr _{X ′} La _Y Y _Z ) TiO ₃ Or the like.

Specific examples of perovskite _{compound, BeTiO 3, MgTiO 3, CaTiO} 3, SrTiO 3, BaTiO 3, PbTiO 3, ZrTiO 3, CeTiO 3, BiTiO 3, (Ba 1-X Sr X) TiO 3, (Bi 1- _{X Sr X) TiO 3, (} Ba 1-X Zr X) TiO 3, (Pb 1-X La X) or the like TiO _{3 titanates; BaSnO 3, CaSnO 3, SrSnO} 3, MgSnO 3, PbSnO 3, CoSnO _3, NiSnO ₃ etc. _{stannates; BaZrO 3, CaZrO 3, SrZrO} 3, MgZrO 3, PbZrO 3 , etc. _{zirconate; MgNbO 3, CaNbO 3, SrNbO} 3, BaNbO 3, niobium salts such as LiNbO _3; LiTaO _3, BaTaO _3, SrTaO _{, CaTaO 3, MgTaO 3, (} Bi 1-X Sr X) TaO 3, (Bi 1-X Nb X) tantalate of ₃ such _{TaO; Pb (Zr 1-X} Ti X) Namarisanshio of _{O 3,} And the like.
In the above formula, X is 0 <X <1, X ′ is 0 ≦ X ′ ≦ 1, Y is 0 ≦ Y ≦ 1, Z is 0 ≦ Z ≦ 1, and 0 ≦ X. '+ Y + Z ≦ 1.
The crystalline double oxide sol of the present invention is particularly preferably a sol of BaTiO ₃ or (Ba _1-X Sr _X ) TiO ₃ having ferroelectric characteristics.

3) Metal Oxide Film A third aspect of the present invention is a metal oxide film formed from a metal oxide sol solution produced by the production method of the present invention.
The metal oxide film of the present invention can be formed by applying a metal oxide sol solution obtained by the production method of the present invention to the surface of a substrate, followed by drying and baking.

  The substrate used for forming the metal oxide film is not limited in its material and size as long as it can form the metal oxide film of the present invention. Examples of the material of the substrate include metal, ceramics, glass, plastic, paper, fiber, leather, and the like. The shape of the substrate may be any shape such as a sheet shape, a plate shape, a film shape, and a three-dimensional object. Moreover, the base | substrate with which the surface was coated can also be used.

  The method (coating method) for applying the metal oxide sol solution to the substrate surface is not particularly limited, and a known coating method can be adopted. Examples thereof include spin coating, dip coating, spray coating, roll coating, screen printing, offset printing, and electrophoretic electrodeposition. Further, two or more of these coating methods may be used in combination.

  The coating film of the metal oxide sol solution formed on the surface of the substrate is dried and heat-treated to remove the organic solvent, and the metal oxide crystallizes to become a target metal oxide film. As a method for drying and heat-treating the coating film of the metal oxide sol solution, for example, after the coating film formed on the substrate is left in an oxygen gas stream at 10 to 200 ° C. for 0.5 to 5 hours, The method of baking with a base | substrate is mentioned.

  When the metal oxide sol obtained by the production method of the present invention is obtained by hydrolyzing a metal alkoxide and then concentrating, the amount of solvent used is small, so that the drying and firing time can be shortened. . The firing time is not particularly limited, but is preferably a short time so that the substrate is not loaded, and is usually 1 to 120 minutes.

  The metal oxide sol solution obtained by the production method of the present invention is obtained by almost completing the hydrolysis reaction of the metal alkoxide, so there is little residual alkoxy group, and there is almost no weight loss even when heated at high temperatures. Absent. The firing temperature may be lower than that in the prior art, and is usually 150 to 700 ° C. Since the substrate does not have to be exposed to a high temperature, the bonding surface between the substrate and the metal oxide film and the substrate is less likely to be damaged such as peeling by heating.

  The metal oxide film of the present invention is preferably a crystalline metal double oxide thin film, more preferably a perovskite compound thin film, although depending on the type of metal alkoxide used as a starting material. Whether or not the metal double oxide in the metal oxide film is crystalline can be confirmed by analyzing the metal oxide film by X-ray diffraction.

  The metal oxide film of the present invention is monodispersed and is formed using a metal oxide sol liquid that loses little weight even when heated to 300 ° C. or higher, so it is dense and homogeneous without cracks and the like. . Therefore, the metal oxide film of the present invention can be widely used as various thin films such as dielectric thin films, conductor thin films, piezoelectric thin films, and semiconductor thin films in the field of electronic devices. In particular, the metal oxide film of the present invention made of a ferroelectric material such as barium titanate or strontium barium titanate is a dielectric thin film such as a capacitor, a piezoelectric element or a thin film memory, a conductive thin film, a piezoelectric thin film, or a semiconductor thin film. It is suitable as various thin films.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 1
In a four-necked flask, barium diethoxide was dissolved in a mixed solution of methanol and 2-methoxyethanol. To this solution, titanium tetraisopropoxide was added and mixed so that the molar ratio of barium diethoxide and titanium tetraisopropoxide was 1: 1 (solution A). The concentration of the metal alkoxide in the liquid A is such that the metal oxide sol present in the reaction liquid obtained by hydrolyzing the metal alkoxide by dropping water is 5% by weight in terms of oxide.

  On the other hand, water obtained by boiling ion-exchanged water for several minutes to remove dissolved carbon dioxide gas and mixing with 2-methoxymethanol (mixing weight ratio: water / 2-methoxymethanol = 1/9) (B Liquid).

  Next, the B liquid was added dropwise to the A liquid while stirring. The dripping amount of water is an amount that is 6 times the total number of moles of barium diethoxide and titanium tetraisopropoxide. After completion of dropping of the liquid B, the mixture was refluxed at about 70 ° C. for 1 hour. The reaction solution was allowed to cool to room temperature, transferred to a sealed container, and allowed to stand at room temperature for several days to obtain a metal oxide sol solution (C1 solution). The obtained C1 liquid was concentrated with a rotary evaporator at a bath temperature of 60 ° C. to obtain a 40% by weight metal oxide sol liquid (D1 liquid) in terms of oxide.

The obtained concentrated sol solution (D1 solution) was scooped with a spatula, applied to the surface of the glass substrate, and the obtained coating film was air-dried at room temperature to obtain a metal oxide film. The obtained metal oxide was analyzed by X-ray diffraction. The measurement result of X-ray diffraction is shown in FIG. In FIG. 1, the horizontal axis represents 2θ, and the vertical axis represents intensity.
From FIG. 1, the peak of crystalline barium titanate was confirmed. Moreover, it was 8 nm when the average crystallite size was calculated | required by the Sierra equation.
Moreover, the particle size distribution of D1 liquid was measured with the highly sensitive high concentration particle diameter measuring apparatus (made by Sysmec Co., Ltd.). The measurement results are shown in FIG. In FIG. 2, the horizontal axis indicates the particle size (nm), and the vertical axis indicates the peak intensity. From FIG. 2, it was found that the metal oxide sol contained in the D1 solution was monodispersed having a peak at 10 nm to 20 nm.

Moreover, the weight change when D1 liquid was heated from room temperature to 700 degreeC was measured. The measurement was performed with a thermogravimetric analyzer (TGA, manufactured by Rigaku Corporation, differential differential thermal balance TG8120).
The measurement results are shown in FIG. In FIG. 3, the horizontal axis indicates the measured temperature (° C.), the vertical axis (left) indicates the weight reduction rate (%), and the vertical axis (right) indicates the change in heat (μV). “a” represents a weight change with respect to a temperature change, and “b” represents a heat amount change with respect to the temperature change. From FIG. 3, weight reduction due to solvent evaporation was observed at around 100 ° C., but almost no change in weight was observed at higher temperatures (150 ° C. to 700 ° C.). The D1 liquid was obtained by almost completing the hydrolysis reaction of the metal alkoxide, and it was considered that there was little remaining alkoxy groups and there was almost no weight loss even when heated at high temperatures.

Example 2
In Example 1, B liquid was dripped at A liquid. The amount of water dropped was 10 times the total number of moles of barium diethoxide and titanium tetraisopropoxide.
After completion of dropping of the liquid B, the mixture was refluxed at about 70 ° C. for 1 hour. The reaction solution was allowed to cool to room temperature, transferred to a sealed container and allowed to stand for several days. The obtained sol solution (C2 solution) was concentrated by a rotary evaporator at a bath temperature of 60 ° C. until it became 30% by weight in terms of oxide to obtain a concentrated sol solution (D2 solution).

The obtained concentrated sol solution (D2 solution) was scooped with a spatula, applied to the surface of the glass substrate, and the obtained coating film was air-dried at room temperature to obtain a metal oxide film. The obtained metal oxide was analyzed by X-ray diffraction. The measurement result of X-ray diffraction is shown in FIG. From FIG. 1, the peak of crystalline barium titanate was confirmed. Further, the crystallite size was determined by the Sierra equation and found to be 10 nm.
The D2 solution was subjected to thermogravimetric analysis in the same manner as in Example 1. As a result, the same result as in Example 1 was obtained.
Further, the concentrated sol solution (D2 solution) was stably present and redissolved when a mixed solvent of methanol and 2-methoxyethanol was added.

Example 3
A concentrated sol solution (D3 solution) is obtained by performing the same operation as in Example 1 except that water is used in 3 times mole instead of 6 times the total mole number of barium diethoxide and titanium tetraisopropoxide. It was. The obtained concentrated sol solution (D3 solution) was scooped with a spatula, applied to the surface of the glass substrate, and the obtained coating film was air-dried at room temperature to obtain a metal oxide film. The obtained metal oxide was analyzed by X-ray diffraction. The measurement result of X-ray diffraction is shown in FIG. From FIG. 1, the peak of crystalline barium titanate was confirmed.

FIG. 1 is a graph showing the X-ray diffraction measurement results of the D1 liquid to D3 liquid of Examples 1, 2 and 3. FIG. 2 is a graph showing the particle size distribution of the D1 liquid in Example 1. FIG. 3 is a graph showing the thermogravimetric analysis of the D1 solution of Example 1.

Claims (8)

An organic solvent solution in which titanium alkoxide and alkaline earth metal alkoxide are dissolved, wherein the concentration of titanium alkoxide and alkaline earth metal alkoxide in the organic solvent solution is obtained by hydrolyzing titanium alkoxide and alkaline earth metal alkoxide. In an organic solvent solution set so as to be 5% by weight or less in terms of metal oxide in the obtained reaction solution, 3 to 10 times mol of dissolved carbonic acid with respect to the total of titanium alkoxide and alkaline earth metal alkoxide Adding water degassed to hydrolyze titanium alkoxide and alkaline earth metal alkoxide;
By concentrating the obtained reaction solution, the particle size distribution is a monodispersed metal oxide sol solution having a peak at 5 to 20 nm, and the concentration of the metal oxide sol is converted to a metal oxide. And a step of obtaining a metal oxide sol solution of 25 to 45% by weight. The method for producing a metal oxide sol liquid according to claim 1 , wherein a solution of the metal oxide sol having a thermogravimetric change of less than 10% by weight when heated from 150 ° C to 700 ° C is obtained. 3. The method for producing a metal oxide sol solution according to claim 1, wherein the metal oxide is crystalline. The method for producing a metal oxide sol solution according to any one of claims 1 to 3 , wherein the metal oxide is a perovskite compound. A crystalline metal double oxide sol produced by the production method according to claim 1 and containing a crystalline metal oxide.

The crystalline metal double oxide sol according to claim 5 , wherein the thermogravimetric change when heated from 150 ° C to 700 ° C is less than 10% by weight. The crystalline metal double oxide sol according to claim 5 or 6 , wherein the crystalline metal double oxide is a perovskite compound. The metal oxide film formed from the metal oxide sol liquid manufactured by the manufacturing method in any one of Claims 1-4 .

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