JP2011057531A - Alkaline earth metal oxide-doped zirconia nanoparticle and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide alkaline earth metal oxide-doped zirconia nanoparticles in a single nanometer order, having low acidity of the surface and no possibility of modifying a resin when the particles are incorporated into the resin, and having a sharp particle size distribution and high crystallinity, and to provide a method for producing the nanoparticles. <P>SOLUTION: The alkaline earth metal oxide-doped zirconia nanoparticles comprise zirconia including a solid solution of an alkaline earth metal oxide, and has an average particle diameter of 1 nm or more and 20 nm or less. The content ratio of the alkaline earth metal oxide is 5 mol% or more and 30 mol% or less with respect to the sum amount of the alkaline earth metal oxide and zirconia. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to alkaline earth metal oxide-doped zirconia nanoparticles and a method for producing the same, and more particularly, ceramic materials, catalysts, high refractive index materials, various resins, plastic films, plastic plates, etc. Alkaline earth metal oxide-doped zirconia nanoparticles suitable for fillers for improving thermal properties such as spots, or fillers for improving these mechanical properties, and particles are difficult to fuse In addition, the present invention relates to a production method capable of producing a large amount of alkaline earth metal oxide-doped zirconia nanoparticles excellent in dispersibility at low cost.

Conventionally, it is well known that zirconia fine particles have been used as fillers for high-performance or high-performance ceramics, plastics, etc. in addition to catalytic applications. In recent years, transparency and more In order to achieve both high performance and high functionality, nanometer-grade zirconia fine particles having an average particle diameter of 1 nm to 20 nm have been proposed (Patent Document 1).
These zirconia fine particles are used as fillers for various resins and the like, aiming to achieve both of the two functions of high transparency and high functionalization of the resin material such as high refractive index.

  On the other hand, zirconia-based fine particles containing zirconia and other metal oxides include a mixture of zirconia particles having a nanometer class particle diameter and other oxide particles, and a nanometer class in which zirconia and other oxides are combined. Various proposals have been made, such as sols containing composite particles having a particle size of zirconia and other oxides, and various proposals have also been made for these production methods.

For example, a hydroxide of divalent metal such as zirconium and calcium is coprecipitated, and the coprecipitate is washed with a divalent metal hydroxide aqueous solution that is concentrated so as not to dissolve the divalent metal hydroxide. Sol obtained by heating and aging the obtained mixed suspension containing a coprecipitated hydroxide and a divalent metal hydroxide at a temperature of 20 to 200 ° C., and dispersing zirconia single crystal fine particles containing a divalent metal ion. Has been proposed (Patent Document 2).
A colloidal solution is produced by hydrolyzing a zirconium salt aqueous solution or an aqueous solution containing a zirconium salt and a salt of at least one metal element selected from the group consisting of yttrium, calcium, and magnesium. A method for producing a high-purity zirconia colloidal solution by washing the solution using a filtration membrane has been proposed (Patent Document 3).

In addition, one or more compounds including Y ³⁺ , Ca ²⁺ , Mg ²⁺ , and Ce ⁴⁺ are dissolved in the suspension of hydrated fine particles, and ammonia water or an aqueous solution of ammonium salt is added to the resulting solution. A method is proposed in which a precipitate is produced, the precipitate is filtered, the obtained solid is washed with water, and then calcined and pulverized to obtain highly crystalline zirconia-based fine particles (Patent Document 4). ).
Further, a mixed aqueous solution containing rare earth element ions such as yttrium and zirconium ions is adjusted to pH 8 or higher with an alkaline aqueous solution, and water is used for a short time within a temperature range of 300 to 400 ° C. using subcritical or supercritical water as a medium. There has been proposed a method of obtaining stabilized zirconia fine particles having a high primary crystallinity with a primary particle size of 10 nm or less by thermal reaction (Patent Document 5).

JP 2007-99931 A JP-A-60-176920 JP-A-62-226815 JP-A 63-129017 JP 2008-184339 A

However, the zirconia fine particles having an average particle diameter of 1 nm to 20 nm described in Patent Document 1 are highly oxidizable as is known as a super strong acidic catalyst material. Therefore, the resin is obtained by using such zirconia fine particles as a filler. When it is contained in the resin, there is a problem that a change in quality such as discoloration may occur depending on the type of resin.
Further, the methods described in Patent Documents 2 and 3 have a problem that only the zirconia-based fine particles having extremely poor crystallinity can be obtained because the obtained zirconia-based fine particles are so-called hydrated zirconia particles. In addition, since the fine particles have a large amount of hydroxyl groups in the fine particles and on the surface of the fine particles, when the composite of the zirconia fine particles and various resins is produced, the compatibility with the resin is poor and the mixing becomes uneven, or However, there is a problem that optical functions such as a high refractive index and thermal functions such as heat resistance are deteriorated.

In addition, although the method described in Patent Document 4 can obtain highly crystalline zirconia-based fine particles, since it is calcined at 1300 ° C. or higher, grain growth or the like occurs and it is difficult to make fine particles. was there. In addition, since the obtained calcined product is made into fine particles by pulverization, there is a limit in controlling the particle size, and there is a problem that zirconia-based fine particles having a particle size of a single nanometer cannot be obtained.
Furthermore, in the method described in Patent Document 5, although zirconia-based fine particles having a small primary particle size and high crystallinity are obtained, components that can be dissolved in zirconia are limited to oxides of rare earth elements such as yttrium. Therefore, there is a problem that the effect is insufficient for suppressing the high acidity of the surface of the zirconia particles. Furthermore, since the particle synthesis reaction is carried out under severe conditions such as subcritical or supercritical, there is a possibility that the apparatus is corroded, and there is a problem that the apparatus itself is extremely expensive, which is not suitable industrially. It was a thing.

  The present invention has been made in order to solve the above problems, and has low surface acidity, there is no possibility of altering the resin even when it is contained in the resin, and it has a sharp particle size distribution. Single nanometer-class alkaline earth metal oxide doped zirconia nanoparticles with high crystallinity, and alkaline earth metals capable of producing large quantities of these alkaline earth metal oxide doped zirconia nanoparticles at low cost It aims at providing the manufacturing method of an oxide dope zirconia nanoparticle.

  As a result of intensive studies to solve the above problems, the present inventors have determined that the average particle diameter of particles obtained by solid solution of an alkaline earth metal oxide in zirconia is 1 nm or more and 20 nm or less. When the content of the alkaline earth metal oxide is 5 mol% or more and 30 mol% or less with respect to the total amount of the alkaline earth metal oxide and zirconia, the acidity of the surface is low and the resin is contained in the resin. In some cases, the present inventors have found that there is no possibility of modifying the resin and that an optical function, a mechanical function, or a thermal function can be imparted, and the present invention has been completed.

  That is, the alkaline earth metal oxide-doped zirconia nanoparticles of the present invention are nanoparticles formed by dissolving an alkaline earth metal oxide in zirconia, having an average particle diameter of 1 nm or more and 20 nm or less, The content of the alkaline earth metal oxide is 5 mol% or more and 30 mol% or less with respect to the total amount of the alkaline earth metal oxide and the zirconia.

  The zirconia is preferably any one of tetragonal, cubic, tetragonal and cubic.

  The method for producing alkaline earth metal oxide-doped zirconia nanoparticles of the present invention includes a step of adding a basic solution to a zirconium salt solution to adjust the pH of the zirconium salt solution to less than 4, and a solution having this pH adjusted. When the alkaline earth metal salt solution is added and the alkaline earth metal salt is converted into an alkaline earth metal oxide and the zirconium salt is converted into zirconia, the content of the alkaline earth metal oxide is as follows. A step of preparing a mixed solution of 5 mol% or more and 30 mol% or less with respect to the total amount of the alkaline earth metal oxide and the zirconia, adding an alkali carbonate solution to the mixed solution to adjust the pH to 7 or more, and precipitating And a step of heating the precipitate to 400 ° C. or higher to produce alkaline earth metal oxide-doped zirconia nanoparticles, Comprising characterized by comprising.

  It is preferable that a step of removing impurities from the produced alkaline earth metal oxide-doped zirconia nanoparticles is provided after the heating step.

  According to the alkaline earth metal oxide-doped zirconia nanoparticles of the present invention, the average particle size is 1 nm or more and 20 nm or less, and the content of the alkaline earth metal oxide is the sum of the alkaline earth metal oxide and zirconia. Since the amount is 5 mol% or more and 30 mol% or less with respect to the amount, the acidity of the surface can be lowered. In addition, even when it is contained in the resin, there is no risk of altering the resin, and it has optical functions such as high transparency and a high refractive index, thermal functions such as thermal expansion coefficient control and heat resistance improvement, or mechanical functions. Can be granted.

  According to the method for producing alkaline earth metal oxide-doped zirconia nanoparticles of the present invention, a basic solution is added to a zirconium salt solution to adjust the pH of the zirconium salt solution to less than 4, and the pH adjusted solution is alkalinized. An earth metal salt solution is added to obtain a mixed solution containing 5 mol% or more and 30 mol% or less in terms of alkaline earth metal oxide, and an alkali carbonate solution is added to the mixed solution to adjust the pH to 7 or more, and the precipitate is added. Since this precipitate is heated to 400 ° C. or higher, there is no fusion between particles, high crystallinity, low surface acidity, and there is a possibility that the resin may be altered even when it is contained in the resin. In addition, alkaline earth metal oxide-doped zirconia nanoparticles having a uniform particle size can be produced in large quantities and at low cost.

It is a transmission electron microscope (TEM) image which shows the magnesia dope zirconia nanoparticle of Example 1 of this invention.

The form for implementing the alkaline-earth metal oxide dope zirconia nanoparticle of this invention and its manufacturing method is demonstrated.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Alkaline earth metal oxide doped zirconia nanoparticles"
The alkaline earth metal oxide-doped zirconia nanoparticles of the present embodiment contain one or more elements selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Nanoparticles formed by dissolving an alkaline earth metal oxide containing zirconia (ZrO ₂ ) in a solid solution, having an average particle diameter of 1 nm to 20 nm, and the content of the alkaline earth metal oxide is the alkali It is 5 mol% or more and 30 mol% or less with respect to the total amount of the earth metal oxide and the zirconia.

Zirconia includes tetragonal zirconia, cubic zirconia, and monoclinic zirconia, but in order to ensure high refractive index and high transparency, it is symmetrical with respect to the crystal axis. Tetragonal zirconia or cubic zirconia having the above is preferable, and these tetragonal zirconia and cubic zirconia may be in a mixed crystal state.
Tetragonal zirconia can be expected to improve the toughness value due to martensite transformation compared to monoclinic zirconia, and has high toughness and hardness, and the mechanical properties of the transparent composite obtained by dispersing in resin Suitable for improvement.

The feature of the alkaline earth metal oxide-doped zirconia nanoparticles is that the average particle size is 1 nm or more and 20 nm or less, and the particle size range is very narrow and has a sharp particle size distribution. It is a secondary particle and is not in an aggregated state.
Here, the average particle diameter was set to 1 nm or more and 20 nm or less because the average particle diameter of the alkaline earth metal oxide-doped zirconia nanoparticles was limited to the above range, thereby producing a composite with a resin. In this case, the particles can be highly filled, and high transparency can be maintained, so that an optical functional composite having a high refractive index and an organic / inorganic composite having excellent heat resistance can be obtained.
If the average particle size is less than 1 nm, the packing density of the particles is reduced and cannot be highly packed. On the other hand, if the average particle size is more than 20 nm, the transparency is lowered, and the mechanical properties are also reduced. It is not preferable because the characteristics are deteriorated.

The content of the alkaline earth metal oxide in the alkaline earth metal oxide-doped zirconia nanoparticles is preferably 5 mol% or more and 30 mol% or less with respect to the total amount of the alkaline earth metal oxide and zirconia, and more preferably. Is 5 mol% or more and 25 mol% or less.
If the content of the alkaline earth metal oxide is less than 5 mol%, the acidic activity of the surface of the zirconia fine particles cannot be suppressed. On the other hand, if the content exceeds 30 mol%, a coarse alkaline earth metal that does not dissolve in the zirconia fine particles. Oxide fine particles appear and zirconia fine particles and alkaline earth metal oxide fine particles are mixed, which is not preferable.

"Method for producing alkaline earth metal oxide-doped zirconia nanoparticles"
The method for producing alkaline earth metal oxide-doped zirconia nanoparticles of the present embodiment,
Adding a basic solution to the zirconium salt solution to adjust the pH of the zirconium salt solution to less than 4,
An alkaline earth metal salt solution is added to the pH-adjusted solution, and the alkaline earth metal oxide is converted into an alkaline earth metal oxide, and the zirconium salt is converted into zirconia. A step of preparing a mixed solution having a content of 5 mol% or more and 30 mol% or less with respect to a total amount of the alkaline earth metal oxide and the zirconia;
Adding an alkali carbonate solution to the mixed solution to bring the pH to 7 or more, and generating a precipitate;
Heating the precipitate to 400 ° C. or higher to produce alkaline earth metal oxide-doped zirconia nanoparticles;
It has.

Next, the manufacturing method of the alkaline earth metal oxide doped zirconia nanoparticles of this embodiment will be described in detail.
First, a basic solution is added to the zirconium salt solution, and the pH of the zirconium salt solution is adjusted to less than 4.
There are no limitations on the type of zirconium salt solution, but zirconium ions and inorganic acid ions such as chlorine ions, nitrate ions and sulfate ions, or acetate ions, oxalate ions, tartrate ions, citrate ions, lactate ions, etc. A solution composed of the organic acid ions is preferably used.

  The basic solution may be any solution that can neutralize the zirconium salt solution. For example, an aqueous solution of sodium hydroxide, potassium hydroxide, ammonia, etc., ammonium carbonate, ammonium bicarbonate, sodium carbonate, sodium bicarbonate , Aqueous solutions containing alkali carbonates and alkali hydrogen carbonates such as potassium carbonate and potassium hydrogen carbonate, amino alcohol solutions such as ethanolamine, diethanolamine and triethanolamine, amide solutions such as formamide, and organic ammonium solutions such as tetramethylammonium A solution containing a basic organic compound such as can be used.

In the present embodiment, the pH of the zirconium salt solution after adding the basic solution to the zirconium salt solution is adjusted to an acidic range of less than 4, preferably 1.5 to 3.5.
The reason is that the zirconia precursor produced | generated by adding and neutralizing a basic solution will be in the state uniformly disperse | distributed by nanometer size in the solution.
Here, when the pH of the zirconium salt solution after adding the basic solution is 4 or more, the produced zirconia precursor aggregates and becomes coarse, which is not preferable. If the pH of the zirconium salt solution after adding the basic solution is less than 1.5, neutralization may be insufficient, and the yield of the resulting zirconia precursor may be deteriorated.
By this pH adjustment, the zirconium salt solution becomes a zirconium precursor colloidal solution in which the zirconium precursor is uniformly dispersed in the solution.

Next, an alkaline earth metal salt solution is added to the pH-adjusted solution, that is, the zirconium precursor colloid solution, and the alkaline earth metal salt is added to the alkaline earth metal oxide (MO) and the zirconium salt is added to zirconia (ZrO _2). ), The content of the alkaline earth metal oxide (MO) when converted into 5 mol% with respect to the total amount (MO + ZrO ₂ ) of the alkaline earth metal oxide (MO) and zirconia (ZrO ₂ ). A mixed solution of not less than 30 mol% and preferably not less than 5 mol% and not more than 25 mol% is prepared.

  There are no limitations on the type of alkaline earth metal salt solution, but alkaline earth metal ions and inorganic acid ions such as chlorine ions, nitrate ions, sulfate ions, acetate ions, oxalate ions, tartaric acid ions, citric acid ions, and the like. A solution composed of organic acid ions such as acid ions and lactic acid ions is preferably used.

  Here, when the alkaline earth metal oxide content is less than 5 mol% when the alkaline earth metal salt is converted into an alkaline earth metal oxide, the acidic activity on the surface of the zirconia fine particles cannot be suppressed. In addition, if it exceeds 30 mol%, coarse alkaline earth metal oxide particles that do not dissolve in zirconia fine particles appear, and zirconia fine particles and alkaline earth metal oxide fine particles are mixed, which is not preferable.

Next, an alkali carbonate solution is added to the mixed solution to adjust the pH to 7 or more, and a precipitate is generated.
As the alkali carbonate, one or two or more selected from the group consisting of lithium carbonate, sodium carbonate, sodium hydrogen carbonate and potassium carbonate can be used. In particular, potassium carbonate is preferred because it has the highest solubility in water. .

By adding this alkaline carbonate solution, alkaline earth metal oxide precursors can be precipitated from alkaline earth metal salts in the mixed solution, and the fusion of zirconia precursors by alkali carbonate is prevented. can do.
The addition amount of the alkali carbonate is preferably 50% by mass or more with respect to the oxide equivalent value in the mixed solution.
The reason is that when the addition amount is less than 50% by mass, the effect of preventing fusion between the zirconia precursors is reduced, and as a result, the zirconia precursors are fused and coarsened.

Since this alkali carbonate can be recovered and reused, there is no upper limit to the amount added, but it is generally 400% by mass or less.
Next, the precipitate is dried and further heated at a predetermined temperature to obtain alkaline earth metal oxide-doped zirconia nanoparticles.
As a drying method, any solvent can be used as long as it can dissipate the solvent in the mixed solution (suspension), and a normal drying method such as heat drying with a heater, vacuum drying, spray drying, infrared heat drying, or the like can be used. .

As a heating method, a normal heating method such as heating with a heater, reduced pressure heating, spray heating, infrared heating, or the like can be used.
As heating by a heater or the like, for example, there are a method of heating in a fixed temperature electric furnace, a method of heating in a fluidized bed electric furnace, and the like.
As a range of heating temperature, 400 degreeC or more and 800 degrees C or less are preferable.
When the heating temperature is less than 400 ° C., zirconia fine particles are not generated from the zirconia precursor, and when it exceeds 800 ° C., fusion between the zirconia fine particles cannot be prevented, and coarse zirconia particles are generated. It is not preferable.

These drying and heating may be performed simultaneously, and further, the above precipitate may be directly heated without drying.
In this mixed solution (suspension liquid), between the zirconia precursor particles in which the alkaline earth metal oxide precursor is precipitated on the cluster-sized zirconia precursor particles and further the alkaline earth metal oxide precursor is precipitated during drying. In this state, an alkali carbonate salt that acts as an anti-fusing agent is deposited. Therefore, if heat treatment is performed in this state, alkaline earth metal oxide-doped zirconia nanoparticles having a nanometer-size particle size in which fine particles are not fused can be easily produced in large quantities.

Since alkaline carbonate remains in the alkaline earth metal oxide doped zirconia nanoparticles obtained by the heat treatment, the alkaline earth metal oxide doped zirconia nanoparticles are used in order to purify the nanoparticles. To remove impurities.
Specifically, alkaline earth metal oxide doped zirconia nanoparticles are dispersed in pure water or an acidic solution, and impurities such as alkali carbonate contained in the alkaline earth metal oxide doped zirconia nanoparticles are purified. Remove by dissolving in water or acidic solution.
Thereby, high-purity alkaline earth metal oxide-doped zirconia nanoparticles that do not contain impurities such as alkali carbonates can be obtained.

  According to the alkaline earth metal oxide-doped zirconia nanoparticles of the present embodiment, the average particle diameter is 1 nm or more and 20 nm or less, and the content of the alkaline earth metal oxide is determined between the alkaline earth metal oxide and the zirconia. Since the amount is 5 mol% or more and 30 mol% or less with respect to the total amount, the acidity of the surface of the nanoparticles can be lowered. In addition, even when the nanoparticles are contained in the resin, there is no possibility that the resin is denatured, and an optical function, a mechanical function, or a thermal function can be imparted to the resin.

  According to the method for producing alkaline earth metal oxide-doped zirconia nanoparticles of the present embodiment, the basic solution is added to the zirconium salt solution to adjust the pH of the zirconium salt solution to less than 4, and then this pH is adjusted. An alkaline earth metal salt solution is added to the solution to obtain a mixed solution containing 5 mol% or more and 30 mol% or less in terms of alkaline earth metal oxide, and then an alkaline carbonate solution is added to the mixed solution to adjust the pH to 7 or more. At the same time, a precipitate is formed, and after the precipitate is separated from the filtrate, dried and heated at a temperature of 400 ° C. or higher and 800 ° C. or lower, there is no fusion between particles and high crystallinity. Nanometer-grade high-purity alkaline earth metal oxide doped zirconia that has low acidity on the surface and does not have the possibility of altering the resin even when it is contained in the resin The Bruno particles can easily be produced in large quantities and at low cost.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L (liter) of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring, and the zirconia precursor sol was added. Produced. The pH of this zirconia precursor sol was 2.4.
Next, 734.2 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid material was pulverized using an automatic mortar, and then baked (heated) in the air at 450 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, and the added potassium carbonate was sufficiently removed and dried. Of magnesia-doped zirconia nanoparticles were obtained.

"Example 2"
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 219 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water and stirred to form a slurry, followed by washing with a centrifuge to sufficiently remove the added potassium carbonate, followed by drying to obtain Example 2. Of magnesia-doped zirconia nanoparticles were obtained.

"Example 3"
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 734.2 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 500 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 50% by mass with respect to the zirconia-converted value of the zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water and stirred to form a slurry, followed by washing with a centrifuge to sufficiently remove the added potassium carbonate, followed by drying. Example 3 Of magnesia-doped zirconia nanoparticles were obtained.

Example 4
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 734.2 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 650 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water and stirred to form a slurry, followed by washing with a centrifuge to sufficiently remove the added potassium carbonate, followed by drying. Example 4 Of magnesia-doped zirconia nanoparticles were obtained.

"Example 5"
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 1387 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, and the added potassium carbonate was sufficiently removed, followed by drying. Example 5 Of magnesia-doped zirconia nanoparticles were obtained.

"Example 6"
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 676.3 g of calcium nitrate tetrahydrate was added to and dissolved in this zirconia precursor sol, to prepare a zirconia precursor sol containing calcium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water and stirred to form a slurry, followed by washing with a centrifuge to sufficiently remove the added potassium carbonate, followed by drying to obtain Example 6. Of calcia doped zirconia nanoparticles were obtained.

“Comparative Example 1”
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, sufficiently removed the added potassium carbonate, and then dried to give Comparative Example 1. Obtained particles.

"Comparative Example 2"
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 84.9 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, sufficiently removed the added potassium carbonate, and then dried to give Comparative Example 2. Obtained particles.

“Comparative Example 3”
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 734.2 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 200 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The addition amount of potassium carbonate at this time was 20 mass% with respect to the zirconia conversion value of the zirconium ion in a zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, sufficiently removed the added potassium carbonate, and then dried to give Comparative Example 3 Obtained particles.

“Comparative Example 4”
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 2774 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 550 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, sufficiently removed the added potassium carbonate, and then dried. Obtained particles.

“Comparative Example 5”
To an aqueous zirconium salt solution in which 2615 g of zirconium oxychloride octahydrate was dissolved in 40 L of pure water, an aqueous ammonium hydrogen carbonate solution in which 896 g of ammonium hydrogen carbonate was dissolved in 11 L of pure water was added with stirring to prepare a zirconia precursor sol. The pH of this zirconia precursor sol was 2.4.
Next, 734.2 g of magnesium nitrate hexahydrate was added to this zirconia precursor sol and dissolved therein to prepare a zirconia precursor sol containing magnesium ions.

Next, a potassium carbonate aqueous solution in which 1000 g of potassium carbonate was dissolved in 35 L of pure water was added to the zirconia precursor sol with stirring to obtain a mixture. The amount of potassium carbonate added at this time was 100% by mass relative to the zirconia-converted value of zirconium ions in the zirconia precursor sol. The pH after addition of potassium carbonate was 11.5.
Next, this mixture was dried in the air at 130 ° C. for 24 hours using a dryer to obtain a solid.

Next, the solid was pulverized using an automatic mortar, and then baked (heated) in the air at 380 ° C. for 2 hours using an electric furnace to obtain a baked product.
Next, the fired product was put into pure water, stirred to form a slurry, washed with a centrifuge, sufficiently removed the added potassium carbonate, and then dried to give Comparative Example 5 Obtained particles.

"Evaluation"
For each of the magnesia or calcia-doped zirconia nanoparticles obtained in Examples 1 to 6 and the particles in Comparative Examples 1 to 4 thus obtained, the crystallite diameter and the particle diameter are measured, the crystal phase is identified, and coloring is performed. Sexuality was evaluated. The measurement method and evaluation method are as follows.
(1) Crystallite size The specific diffraction line profile of the particles was measured by powder X-ray diffraction (XRD), and the crystallite size (crystallite size) was determined from the spread of the profile.
(2) Average particle diameter A transmission electron microscope (TEM) image of the particles was taken, the particle diameter of 50 particles was measured from the TEM image, and the average particle diameter was calculated.

(3) Identification of crystal phase The crystal phase of the particles was identified by powder X-ray diffraction (XRD).
(4) Colorability 10 g of particles are added to 100 g of methyl ethyl ketone (MEK: boiling point = 79 ° C.) to form a suspension, and the suspension is refluxed at 80 ° C. for 24 hours with stirring. The degree of coloration of the liquid was visually observed.
Here, “◯” indicates that the color tone did not change, and “X” indicates that the color tone changed.

Table 1 shows the crystallite diameter, particle diameter, crystal phase, and colorability of each of the magnesia or calcia-doped zirconia nanoparticles of Examples 1 to 6 and each of Comparative Examples 1 to 5.
Moreover, the transmission electron microscope (TEM) image of the magnesia dope zirconia nanoparticle of Example 1 is shown in FIG.

In the magnesia or calcia-doped zirconia nanoparticles of Examples 1 to 6, diffraction lines other than magnesia or calcia, cubic zirconia (c-ZrO ₂ ) and tetragonal zirconia (t-ZrO ₂ ) are not observed, and the crystallinity I found it excellent.
Further, it was found that the crystallite diameter was in the range of 2 nm to 10 nm, the average particle diameter was in the range of 1 nm to 20 nm, the particles were not fused, and the particle size distribution was sharp.

On the other hand, in the particles of Comparative Example 1, since the alkaline earth metal oxide was not dissolved, the acidity of the surface was high, the suspension was also yellowed, and there was a problem in coloring.
In the particles of Comparative Example 2, monoclinic zirconia (m-ZrO ₂ ) diffraction lines are recognized in addition to tetragonal zirconia (t-ZrO ₂ ), and these two types of crystal phases are mixed, resulting in a decrease in crystallinity. I found out. Also, the suspension was yellowed, and there was a problem with coloring.
In the particles of Comparative Example 3, monoclinic zirconia (m-ZrO ₂ ) and tetragonal zirconia (t-ZrO ₂ ) diffraction lines are observed, the crystallinity is lowered, and the particles are fused. Vigorously, the particle size could not be measured.
In the particles of Comparative Example 4, diffraction lines of magnesium carbonate (MgCO ₃ ) other than tetragonal zirconia (t-ZrO ₂ ) and cubic zirconia (c-ZrO ₂ ) are observed, and these three kinds of crystal phases are mixed. The crystallinity was also lowered, and the crystallite diameter could not be measured.
In the particles of Comparative Example 5, since the diffraction lines of magnesia and zirconia were broad and the half width was wide, it was confirmed that the particles were amorphous and not crystallized. Therefore, the crystallite diameter could not be measured.

Claims (4)

Nanoparticles formed by dissolving an alkaline earth metal oxide in zirconia,
The average particle size is 1 nm or more and 20 nm or less,
The alkaline earth metal oxide-doped zirconia is characterized in that the content of the alkaline earth metal oxide is 5 mol% or more and 30 mol% or less with respect to the total amount of the alkaline earth metal oxide and the zirconia. Nanoparticles.   2. The alkaline earth metal oxide-doped zirconia nanoparticles according to claim 1, wherein the zirconia is any one of tetragonal, cubic, tetragonal and cubic. Adding a basic solution to the zirconium salt solution to adjust the pH of the zirconium salt solution to less than 4,
An alkaline earth metal salt solution is added to the pH-adjusted solution, and the alkaline earth metal oxide is converted into an alkaline earth metal oxide, and the zirconium salt is converted into zirconia. A step of preparing a mixed solution having a content of 5 mol% or more and 30 mol% or less with respect to a total amount of the alkaline earth metal oxide and the zirconia;
Adding an alkali carbonate solution to the mixed solution to bring the pH to 7 or more, and generating a precipitate;
Heating the precipitate to 400 ° C. or higher to produce alkaline earth metal oxide-doped zirconia nanoparticles;
A method for producing alkaline earth metal oxide-doped zirconia nanoparticles, comprising:   The alkaline earth metal oxide-doped zirconia nanoparticles according to claim 3, further comprising a step of removing impurities from the produced alkaline earth metal oxide-doped zirconia nanoparticles after the heating step. Production method.