JP4961985B2 - Method for producing zirconia fine particles - Google Patents

Description

  The present invention relates to a method for producing zirconia fine particles, and more particularly to a method for producing zirconia fine particles that can easily obtain zirconia fine particles having a small particle size, a high specific surface area, and high crystallinity.

Conventionally, zirconia is known and widely used as a structural ceramic material, a refractory material, a conductive material, a high refractive index material, a dielectric material, and the like.
In recent years, these materials have been miniaturized and highly functionalized, and development of zirconia fine particles has been demanded. As a method for producing such zirconia fine particles, a solution method such as a hydrolysis method or a neutralization / coprecipitation method is usually used.
The hydrolysis method is a method in which an aqueous solution containing a zirconium salt is heated and hydrolyzed, and the resulting hydrated zirconia sol is dried and fired (see, for example, the claims of Patent Document 1). On the other hand, the neutralization / coprecipitation method is a method in which an aqueous solution containing a zirconium salt is neutralized with an alkali, and the resulting precipitate is dried and fired. For example, a method using a diamine compound for neutralization is known (see the claims of Patent Document 2). Further, in neutralizing the zirconium salt solution, it is not completely neutralized but partially neutralized to produce a zirconia oxide precursor (zirconic acid (water) oxide, zirconiyloxy (hydro) oxide), A method is disclosed in which an inorganic salt is added to the partially neutralized solution to form a mixed solution, and the mixed solution is heated to produce zirconia fine particles (see the claims of Patent Document 3).
JP 2001-39716 A JP 2001-253714 A JP 2006-16236 A

As the zirconia fine particles, since the crystal shape and the crystal system are easily maintained, those having high crystallinity with a high purity and uniform composition with few crystal lattice defects are desired.
However, in the above conventional solution method, an oxide is obtained via a zirconia hydrate or zirconium hydroxide, so that hydroxyl groups are likely to remain on the end faces of the zirconia fine particles, and crystal lattice defects are likely to occur.
As the zirconia fine particles, a fine particle having a primary particle diameter of 200 nm or less is desired. However, in any of the conventional solution methods, heat treatment is essential. For this reason, the product grows grains by heating, so that polycrystals or strong agglomeration are likely to occur, and it is difficult to obtain zirconia in the form of fine crystal grains.
On the other hand, when heating is suppressed in order to prevent the formation of polycrystals or strong agglomeration, there is a problem that it is difficult to obtain a complete oxide and that the crystallinity of the product is not high.
That is, in any of the above conventional techniques, it has been difficult to obtain fine particles having a primary particle size with a high crystallinity of 200 nm or less.
The present invention relates to a method for producing zirconia fine particles, and an object thereof is to provide a method for easily obtaining zirconia fine particles having a small particle size and high crystallinity.

In order to achieve the above object, the present invention adopts the following configuration.
[1] Oxide-based mol%, ZrO ₂ is 3 to 30%, RO (R is one or more selected from the group consisting of Ba, Sr, Ca, Mg, and Zn) is 10 to 55%, A step of obtaining a melt containing 30 to 80% of B ₂ O ₃ ; a step of rapidly cooling the melt to form an amorphous material; and heating the amorphous material at 600 to 1000 ° C. to obtain a zirconia crystal. And a step of separating the zirconia crystals from the precipitate to obtain zirconia fine particles in this order.

[2] 3% to 30% of ZrO ₂ , RO (R is one or more selected from the group consisting of Ba, Sr, Ca, Mg, and Zn) and R ′ ₂ O R ′ is one or more selected from the group consisting of Li, Na and K) to obtain a melt containing 10 to 55% in total and 30 to 80% B ₂ O ₃ , and rapidly cooling the melt A step of obtaining an amorphous material, a step of heating the amorphous material at 600 to 1000 ° C. to obtain a precipitate containing zirconia crystals, and separating the zirconia crystals from the precipitate to obtain zirconia fine particles. A process for producing zirconia fine particles.

[3] The method for producing zirconia fine particles according to [1] or [2], wherein the amorphous substance is in the form of flakes or fibers.
[4] The method for producing zirconia fine particles according to any one of [1] to [3], wherein the step of separating the zirconia crystal includes a step of adding an acid to the precipitate.
[5] The method for producing zirconia fine particles according to any one of [1] to [4], wherein the crystal system of the zirconia fine particles is monoclinic and / or tetragonal.
[6] The method for producing zirconia fine particles according to any one of [1] to [5], wherein the average primary particle diameter of the zirconia fine particles is 5 to 200 nm.
[7] The method for producing zirconia fine particles according to any one of [1] to [6], wherein the zirconia fine particles have a specific surface area.

  According to the present invention, highly crystalline zirconia fine particles having a small particle diameter can be easily obtained. The zirconia fine particles obtained by the present invention have a high specific surface area, structural ceramics and refractory materials, catalysts, conductive materials, high refractive index materials and dielectric materials, fillers for adjusting thermal and mechanical properties, etc. Useful as.

  The production method of the present invention is referred to as a step of obtaining a melt having a predetermined composition (hereinafter referred to as “melting step”) and a step of rapidly cooling the melt into an amorphous substance (hereinafter referred to as “quick cooling step”). ), A step of heating the amorphous substance at 600 to 1000 ° C. to obtain a precipitate containing zirconia crystals (hereinafter referred to as a “crystallization step”), and separating the zirconia crystals from the precipitate to obtain zirconia. And a step of obtaining fine particles (hereinafter referred to as “separation step”) in this order.

[Melting process]
In the melting step, 3 to 30% ZrO _{2 and 10} to 55% RO (R is one or more selected from the group consisting of Ba, Sr, Ca, Mg, and Zn) are expressed in mol% based on oxide. A melt containing 30-80% of B ₂ O ₃ is obtained (first embodiment).
Or 3% to 30% of ZrO ₂ , RO (R is one or more selected from the group consisting of Ba, Sr, Ca, Mg, and Zn) and R ′ ₂ O (R 'Is one or more selected from the group consisting of Li, Na and K) to obtain a melt containing 10 to 55% in total and 30 to 80% of B ₂ O ₃ (second embodiment).
Note that the mol% based on the oxide is a molar percentage based on the molecule in which the metal oxide has the maximum oxidation number unless otherwise specified, and is calculated from the raw material charge.

The melt having the above composition range is preferable because it has an appropriate viscosity, and in the subsequent quenching step, the melt is vitrified without crystallizing to obtain an amorphous substance.
When the content ratio of ZrO ₂ in the melt exceeds 30%, the content ratio of RO (or the sum of RO and R ′ ₂ O) is less than 10%, or the content ratio of B ₂ O ₃ is 30% If it is less than the range, the melt is easily crystallized in the rapid cooling process, and it is difficult to vitrify into an amorphous substance. Therefore, it becomes difficult to obtain zirconia fine particles, which is not preferable.
On the other hand, when the content ratio of ZrO ₂ is less than 3%, when RO (or the sum of RO and R ′ ₂ O) exceeds 55%, or when B ₂ O ₃ exceeds 80%, the following crystal In the conversion, zirconia crystals may not be sufficiently precipitated, which is not preferable.
Among them, when ZrO ₂ is a melt containing 5 to 20%, RO (or the sum of RO and R ′ ₂ O) is 15 to 55%, and B ₂ O ₃ is 40 to 70%, the melt has an appropriate viscosity. It is preferable because a product can be easily obtained, zirconia fine particles having a desired composition can be easily obtained, and the yield can be increased.

In the second aspect, it is preferable that R ′ ₂ O is contained in the melt because the melting temperature is lowered and vitrification is facilitated in the rapid cooling step described later. In the second embodiment, the RO in the melt is preferably 15 to 52% and more preferably 25 to 50% in terms of mol% based on the oxide. In the second embodiment, R ′ ₂ O in the melt is preferably 3 to 25% and more preferably 5 to 20% in terms of mol% based on the oxide.

In 1st aspect and 2nd aspect, it is preferable to contain ZnO in a part of RO since it has the effect of lowering the melting temperature and facilitating vitrification by the rapid cooling process described later.
Further, when CaO and / or MgO is included in a part of RO, tetragonal and / or cubic zirconia fine particles are likely to be precipitated in the crystallization step described later. Furthermore, when BaO and / or SrO are included in a part of RO, the melting temperature can be increased, and the zirconia content in the melt can be increased.

The melt was prepared by mixing a compound serving as a Zr source, a compound serving as an R source (in the second embodiment, a compound serving as an R ′ source), and a compound serving as a B source in a predetermined ratio that gives the composition of the melt. The mixture is obtained by heating in the presence of oxygen.
The composition of this mixture theoretically corresponds to the composition of the melt after melting. However, since there are components that are easily lost due to volatilization during the melting process, such as B, the composition of the melt after melting may be slightly different from the mol% of the oxide basis calculated from the charged amount. .

Zr sources include zirconium oxide (ZrO ₂ ), zirconium hydroxide (Zr (OH) ₄ ), magnesia, and calcia-stabilized zirconia ((Ca, Mg) _x Zr _1-x O ₂ ) [0 <x ≦ 0. .2] is preferably used.
Further, zirconium carbonate (Zr (CO ₃ ) ₂ .nH ₂ O), zirconium chloride (ZrCl ₄ .nH ₂ O), zirconium nitrate (Zr (NO ₃ ) ₃ .nH ₂ O), zirconium sulfate (Zr ₂ (SO ₄ ) One or more selected from the group consisting of ₃ · nH ₂ O) and zirconium fluoride (ZrF ₄ ) may be used (in the above formulas, n represents a hydration number, and n = 0 (In addition, the oxy-salts are also included.)
The Zr source not only becomes the final product, but also acts as a part of the glass forming component in cooperation with the R source, R ′ source, and B source described later by melting.

As the R source, it is preferable to use one or more selected from the group consisting of R oxide (RO) or carbonate (RCO ₃ ).
Furthermore, R nitrate (R (NO ₃ ) ₂ · pH ₂ O), R chloride (RCl ₂ · pH ₂ O), R sulfate (RSO ₄ · pH ₂ O) and R fluoride (RF ₂ ) may be used (one or more selected from the group consisting of ₂ ) (in the above formulas, p represents the number of hydration and includes the case of an anhydride of p = 0).

As the R ′ source, it is preferable to use carbonate (R ′ ₂ CO ₃ ).
Also, R ′ oxide (R ′ ₂ O) or R ′ nitrate (R′NO ₃ · qH ₂ O), R ′ chloride (R′Cl · qH ₂ O), R ′ sulfate ( One or more selected from the group consisting of R ′ ₂ SO ₄ .qH ₂ O), R ′ hydroxide (R′OH.qH ₂ O) and R fluoride (R′F) may be used. Good (in each of the above formulas, q represents the number of hydration, including the case of q = 0 anhydride).
These R ′ sources serve as a part of the glass forming component, and also serve to lower the melting temperature and facilitate vitrification by the cooling step described later.

As the B source, it is preferable to use one or more selected from the group consisting of boron oxide (B ₂ O ₃ ) and boric acid (H ₃ BO ₃ ). Borates of Zr, R, and R ′ can also be used.

The purity of the constituent material in the mixture is not particularly limited as long as the desired properties are not deteriorated, but the purity excluding hydration water is preferably 99% or more, and is 99.9% or more. More preferred.
Further, the particle size of the constituent material is not particularly limited as long as it is within a range in which a uniform melt can be obtained by melting. The constituent materials are preferably melted after being mixed dry or wet using a mixing / pulverizing means such as a ball mill or a planetary mill.

Melting may be performed in an air atmosphere, but is preferably performed while controlling the oxygen partial pressure and the oxygen flow rate. The crucible used for melting is preferably made of alumina, platinum, or platinum containing rhodium, and a refractory can also be used.
The melting is preferably performed using a resistance heating furnace, a high frequency induction furnace, or a plasma arc furnace. The resistance heating furnace is preferably an electric furnace provided with a heating element made of metal such as nichrome alloy, silicon carbide, molybdenum silicide, or lanthanum chromite. The high frequency induction furnace may include any induction coil that can control the output. The plasma arc furnace may be any one that uses carbon or the like as an electrode and can use a plasma arc generated thereby. Further, it may be melted by direct heating with infrared rays or laser.

The above mixture may be melted in a powder state, or a previously molded mixture may be melted. In the case of using a plasma arc furnace, a previously molded mixture can be melted as it is and further rapidly cooled.
The mixture is melted at 1300 ° C or higher, preferably 1400-1600 ° C. Further, the obtained glass melt may be stirred in order to improve the uniformity.

[Rapid cooling process]
In the rapid cooling step, the melt obtained as described above is rapidly cooled to near room temperature to obtain an amorphous substance.
The cooling rate is preferably 100 ° C./second or more, and more preferably 1 × 10 ⁴ ° C./second or more.
In the quenching process, the melt is dripped between twin rollers rotating at high speed to obtain a flake-shaped amorphous material, or a continuous fiber-like amorphous material from the melt by a high-speed rotating drum. A method of winding up a substance (long fiber) is preferably used. As the double roller and drum, those made of metal or ceramics are preferably used. Moreover, you may obtain a fiber-like amorphous substance (short fiber) using the spinner which rotated at high speed and provided the pore on the side wall. By using these apparatuses, the melt can be effectively rapidly cooled to a high purity amorphous material.

When the amorphous material is in the form of flakes, rapid cooling is preferably performed so that the average thickness is 200 μm or less, more preferably 100 μm or less. Moreover, in the case of a fibrous form, it is preferable to rapidly cool so that the average diameter becomes 50 μm or less, more preferably 30 μm or less. By setting the average thickness or average diameter to the upper limit value or less, the crystallization efficiency in the subsequent crystallization step can be increased.
In addition, the average thickness in the case of flakes can be measured with a caliper or a micrometer. Moreover, the average diameter in the case of fibrous form can be measured by the said method or observation with a microscope.
When an amorphous substance having a thickness or diameter exceeding the upper limit is obtained, it is preferably subjected to a subsequent crystallization step after pulverization.

[Crystalling process]
In the crystallization step, the amorphous substance obtained in the rapid cooling step is heated to obtain a precipitate containing zirconia crystals. The heating temperature in the crystallization step is 600 to 1000 ° C, and preferably 650 to 850 ° C.
When the heating temperature in the crystallization step is less than 600 ° C., crystals are hardly precipitated even if heating is continuously performed for about 24 hours. On the other hand, when the heating temperature exceeds 1000 ° C., the crystallized material containing the amorphous substance may be melted, which is not preferable.
Since crystal precipitation consists of two stages of nucleation and subsequent crystal growth, these two stages may proceed at different heating temperatures.

In the range of 600 to 1000 ° C., the higher the heating temperature, the larger the amount of crystals to be precipitated and the particle diameter of the precipitated crystals tend to increase. Therefore, the heating temperature should be set according to the desired particle diameter. That's fine.
Moreover, since the heating temperature affects the crystal system of the precipitated zirconia, the heating temperature may be set according to the desired crystal system.

  In the crystallization step, it is preferable to keep the above heating temperature range for 4 hours to 96 hours because zirconia can be sufficiently crystallized. The longer the heating time, the larger the amount of crystals to be precipitated, and the larger the particle size of the crystals to be precipitated, so the holding time may be set according to the desired crystal precipitation amount and particle size. . Moreover, since the heating time affects the crystal system of the precipitated zirconia, the heating time may be set according to the desired crystal system.

In the crystallization process, zirconia fine particles are precipitated as crystals by crystallization of an amorphous substance. Depending on the composition of the mixture, borates of R and R ′, ZrO ₂ , RO, R′O, and double salts of boric acid may be precipitated. These deposits other than zirconia can be removed in the subsequent separation step.

[Separation process]
In the separation step, zirconia crystals are separated from the precipitate obtained in the crystallization step to obtain zirconia fine particles.
The separation step preferably includes a step of adding an acid to the precipitate. If an acid is added to the precipitate, substances other than zirconia crystals can be easily leached and removed. As the acid, inorganic acids such as acetic acid, hydrochloric acid and nitric acid, and organic acids such as oxalic acid and citric acid can be used.
At this time, in order to accelerate the leaching process and adjust the particle diameter of the fine particles to a desired range, the precipitate containing the zirconia crystals may be pulverized dry or wet before the leaching process. When pulverizing, it is preferable to use a medium such as a ball mill. Moreover, in order to accelerate | stimulate leaching, you may warm and use an acid, and you may use shaking operation or ultrasonic irradiation together. Although this leaching treatment may cause some of the zirconia crystals to dissolve, it is rather preferable in that the particle diameter can be made uniform. Furthermore, this leaching process may be repeated several times.

  After the leaching treatment, the zirconia fine particles are obtained by washing with pure water as necessary. The zirconia fine particles obtained by the present invention are preferably at least one selected from the group consisting of monoclinic crystals, tetragonal crystals and cubic crystals. The crystal system can be adjusted mainly by the composition of the melt and the heating time and heating temperature in the crystallization process.

The smaller the average primary particle diameter of the zirconia fine particles obtained in the present invention (in the case of anisotropic particles, the longer diameter is preferred). The smaller the average primary particle diameter, the higher the specific surface area can be achieved, which is preferable because the functionality such as conductivity, refractive index and dielectric constant can be improved. Among these, an average primary particle diameter of 10 to 200 nm is preferable because it can be made into fine particles having excellent heat resistance and a high specific surface area. The average primary particle diameter of the zirconia fine particles is a value measured by an X-ray diffraction method.
In addition, it is preferable that the specific surface area of the zirconia fine particles obtained in the present invention is 20 m ² / g or more because the functionality such as conductivity, refractive index and dielectric constant can be increased. The specific surface area is a value obtained by converting a measured value by the nitrogen adsorption method into a sphere by the BET method.
The average primary particle size and specific surface area can be adjusted mainly by the average thickness or average diameter of the amorphous material obtained in the rapid cooling process, and the heating time and heating temperature in the crystallization process.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these.
[Examples 1 to 15]
Zirconium oxide (ZrO ₂ ), RCO ₃ (R = Ba, Sr, Ca and Mg), Na ₂ CO ₃ and oxidation so that the composition of the melt has the ratio shown in Table 1 in terms of mol% based on oxide. Boron (B ₂ O ₃ ) was weighed, mixed and pulverized in a dry process for 2 hours to obtain a raw material mixture.

The obtained raw material mixture was filled in a crucible equipped with a platinum nozzle containing 20% by mass of rhodium and heated at 1500 ° C. for 1 hour in an electric furnace using molybdenum silicide as a heating element to be completely melted.
Next, the glass melt is dropped while the lower end of the nozzle is heated in an electric furnace, and the droplet is rapidly cooled at about 1 × 10 ⁵ ° C / second by passing through a twin roller having a diameter of about 15 cm rotating at 300 rpm. A flaky solid was obtained. The obtained flakes were light yellow or yellow and were transparent amorphous substances. When the thickness of the flakes was measured with a micrometer, it was 30 to 50 μm.

In each of Examples 1 to 15, the glass transition point and the crystallization start temperature were determined in advance based on differential scanning calorimetry (DSC) using a part of the obtained flakes. As shown in Table 2, the flakes were heated at a heating temperature of 700 ° C., 750 ° C., or 800 ° C. higher than the glass transition point for 8 hours to precipitate zirconia crystals.
Next, the flakes after the crystallization treatment were shaken and stirred in a 1 mol / L acetic acid solution at 70 ° C. for 6 hours to dissolve out soluble substances. The leached solution was centrifuged and the supernatant was discarded. After performing this operation 5 times, washing with water was performed 5 times, and drying was performed to obtain fine particles.

The mineral phase of the fine particles obtained was identified using an X-ray diffractometer. As a result, in any of Examples 1 to 15, the diffraction pattern of any of existing monoclinic ZrO ₂ (JCPDS card number 72-1669) and tetragonal ZrO ₂ (JCPDS card number 50-1089), or both diffraction patterns It was almost the same as the combination of. That is, according to the present invention, it can be seen that highly crystalline fine particles can be obtained.

Table 2 shows the crystal system of zirconia identified by the X-ray diffractometer. In Table 2, “M” represents a single crystal and “T” represents a tetragonal crystal. The inequality sign indicates the abundance of crystals in each crystal system, and “A> B” indicates that there are more A crystal crystals than B crystal crystals, and “A >> B”. Indicates that there are much more crystals of the A crystal system than crystals of the B crystal system. “-” Indicates that crystallization treatment at the heating temperature was not performed.
In addition, the X-ray diffraction patterns of the fine particles obtained by crystallization at a heating temperature of 750 ° C. for Example 2, Example 6 and Example 15 are shown in FIG. 1, FIG. 2, and FIG. 3, respectively.

[Example 16]
The raw material mixture having the same composition as in Example 2 was mixed and pulverized, melted, and rapidly cooled in the same manner as in Examples 1 to 15, and then heated at 700 ° C, 750 ° C, 790 ° C, or 820 ° C. The mixture was heated for 8 hours for crystallization, and then subjected to leaching, washing and drying in the same manner as in Examples 1 to 15 to obtain fine particles.

  The average primary particle diameter of the obtained fine particles was determined. Here, the average primary particle diameter is a crystallite diameter, and is a particle diameter calculated based on Scherrer's equation from the spread of X-ray diffraction lines. The average primary particle diameters of the fine particles crystallized at each heating temperature of 700 ° C., 750 ° C., 790 ° C., or 820 ° C. were 23 nm, 30 nm, 57 nm, and 79 nm, respectively. From this result, it can be seen that according to the present invention, fine particles having a very fine particle diameter can be obtained. Moreover, it turns out that the particle diameter of the microparticles | fine-particles obtained becomes small, so that the heating temperature in a crystallization process is low.

Further, the specific surface area of the obtained fine particles was determined by a nitrogen adsorption method. The calculation method is a sphere conversion value by the multipoint BET method. The specific surface areas of the fine particles crystallized at each heating temperature of 700 ° C., 750 ° C., 790 ° C., or 820 ° C. were 46 m ² / g, 42 m ² / g, 31 m ² / g, and 28 m ² / g, respectively. From this result, it can be seen that all of the obtained fine particles have a high specific surface area. Moreover, it turns out that the specific surface area of the microparticles | fine-particles obtained becomes large, so that the heating temperature in a crystallization process is low.

[Example 17 (comparative example)]
Zirconium oxide so that the composition of the melt is 1.0%, 9.9%, 9.9% and 79.2% in terms of mol% on the basis of ZrO ₂ , BaO, SrO and B ₂ O ₃ (ZrO ₂ ), barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ) and boron oxide (B ₂ O ₃ ) were weighed to obtain a raw material mixture.
The obtained raw material mixture was subjected to mixing / pulverization treatment, melting treatment, rapid cooling treatment, crystallization treatment, leaching / washing / drying treatment in the same manner as in Examples 1 to 15, and zirconia fine particles were visually observed. I could not confirm.

[Example 18 (comparative example)]
Zirconium oxide so that the composition of the melt is 40.0%, 6.0%, 6.0% and 48.0% in terms of mole% based on ZrO ₂ , BaO, SrO and B ₂ O ₃ (ZrO ₂ ), barium carbonate (BaCO ₃ ), strontium carbonate (SrCO ₃ ) and boron oxide (B ₂ O ₃ ) were weighed to obtain a raw material mixture.
The obtained raw material mixture was mixed and pulverized in the same manner as in Examples 1 to 15, and then melted in the same manner as in Examples 1 to 15. It was not obtained.

[Example 19 (comparative example)]
The raw material mixture having the same composition as in Example 2 and Example 6 was mixed and pulverized, melted, and rapidly cooled in the same manner as in Examples 1 to 15, and then heated at a heating temperature of 500 ° C. for 8 hours to produce crystals. When leaching was performed in the same manner as in Examples 1 to 15, zirconia fine particles could not be visually confirmed.

  According to the present invention, highly crystalline zirconia fine particles having a small particle diameter can be easily obtained. The fine particles have a high specific surface area and are useful as structural ceramics and refractory materials, catalysts, conductive materials, high refractive index materials and dielectric materials, and fillers for adjusting thermal and mechanical properties.

The X-ray-diffraction pattern figure of the zirconia microparticles | fine-particles obtained in Example 2 (heating temperature 750 degreeC). The X-ray-diffraction pattern figure of the zirconia microparticles | fine-particles obtained in Example 6 (heating temperature 750 degreeC). The X-ray-diffraction pattern figure of the zirconia microparticles | fine-particles obtained in Example 15 (heating temperature 750 degreeC).

Claims (7)

ZrO ₂ 3-30%, RO (R is at least one selected from the group consisting of Ba, Sr, Ca, Mg, and Zn) 10-55%, B ₂ O Obtaining a melt containing 30-80% of ₃ ,
Rapidly cooling the melt to an amorphous material;
Heating the amorphous material at 600 to 1000 ° C. to obtain a precipitate containing zirconia crystals;
And a step of separating the zirconia crystals from the precipitate to obtain zirconia fine particles in this order. In terms of mol% based on oxide, ZrO ₂ is 3 to 30%, RO (R is one or more selected from the group consisting of Ba, Sr, Ca, Mg, and Zn) and R ′ ₂ O (R ′ is A step of obtaining a melt containing 10 to 55% in total and 30 to 80% B ₂ O ₃ in a total of one or more selected from the group consisting of Li, Na and K;
Rapidly cooling the melt to an amorphous material;
Heating the amorphous material at 600 to 1000 ° C. to obtain a precipitate containing zirconia crystals;
And a step of separating the zirconia crystals from the precipitate to obtain zirconia fine particles in this order.   The method for producing zirconia fine particles according to claim 1 or 2, wherein the amorphous substance is in the form of flakes or fibers.   The method for producing zirconia fine particles according to any one of claims 1 to 3, wherein the step of separating the zirconia crystals includes a step of adding an acid to the precipitate.   The method for producing zirconia fine particles according to any one of claims 1 to 4, wherein a crystal system of the zirconia fine particles is monoclinic and / or tetragonal.   The method for producing zirconia fine particles according to any one of claims 1 to 5, wherein an average primary particle diameter of the zirconia fine particles is 5 to 200 nm. The specific surface area of the said zirconia fine particle is 10 m < ² > / g or more, The manufacturing method of the zirconia fine particle of any one of Claims 1-6.

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