JPWO2020026971A1 - Garnet-type composite metal oxide and its manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a method for producing a composite metal oxide having excellent crystallinity by a mechanochemical method. The present invention is a method for producing a garnet-type composite metal oxide containing Li, La, Zr and O, wherein a mixture containing a raw material powder containing a Li source powder, a La source powder and a Zr source powder and a flux is used. , A method for producing a garnet-type composite metal oxide, which comprises treating with the mechanochemical method and reacting the raw material powder. It is preferable that the raw material powder further contains at least one of an Al source powder and a Ga source powder.

Description

The present invention relates to a garnet-type composite metal oxide and a method for producing the same.

Some composite metal oxides containing a plurality of metals have properties such as fluorescence properties, ferroelectric properties, superconducting properties, and ionic conductivity, and are used in various fields depending on the properties. As a method for producing a composite metal oxide, a method is well known in which raw materials such as metal oxide and metal carbonate are prepared for each metal element, and the raw materials of each metal element are mixed and fired. On the other hand, in Patent Document 1, a YAG phosphor (Y ₃ Al ₅ O ₁₂ : Ce) is mentioned as a composite metal oxide, and YAG is treated by a mechanochemical method together with a flux using a metal oxide powder as a raw material. It is disclosed that a phosphor (Y ₃ Al ₅ O ₁₂ : Ce) can be produced.

WO2017 / 00267

According to Patent Document 1, it is described that by treating a mixture containing a raw material powder and a flux by a mechanochemical method, the raw material powders can be reacted with each other without firing later. However, as a result of examination by the present inventors, in the YAG phosphor disclosed in Patent Document 1, YAG crystals can be produced by the mechanochemical method, but crystals of YAG crystals obtained only by mechanochemical treatment. There was still room for improvement in sex.

Therefore, an object of the present invention is to provide a method for producing a composite metal oxide having excellent crystallinity by a mechanochemical method.

The present inventors examined composite metal oxides having various compositions, and focused on composite metal oxides containing Li, La, Zr, and O having the same garnet structure as YAG crystals. We have found that when the composite metal oxide is produced by treatment by a chemical method, a garnet-type composite metal oxide having better crystallinity than the YAG crystal produced by the mechanochemical method can be produced, and the present invention has been completed. The present invention is as follows.

[1] A method for producing a garnet-type composite metal oxide containing Li, La, Zr and O.
A garnet-type composite metal oxide characterized by treating a mixture containing a flux and a raw material powder containing a Li source powder, a La source powder, and a Zr source powder by a mechanochemical method and reacting the raw material powder. Production method.
[2] The production method according to [1], wherein the raw material powder further contains at least one of an Al source powder and a Ga source powder.
[3] The production method according to [1] or [2], wherein the garnet-type composite metal oxide has a crystallite diameter of 30 nm or more.
[4] The production method according to [2] or [3], wherein the crystal system of the garnet-type composite metal oxide is cubic.
[5] Bottomed cylindrical container and
It is equipped with a rotor with a tip wing with a curvature smaller than the inner circumference of this container.
A predetermined clearance is provided between the tip wing and the inner circumference of the container.
The production method according to any one of [1] to [4], wherein the rotor is rotated to shear the mixture containing the raw material powder and the flux at the clearance while compressing the mixture.
[6] The production method according to [5], wherein the power of the rotor is 0.05 kW / g or more with respect to the total amount of the raw material powder, and the rotor is rotated for 10 minutes or more.
[7] The production method according to any one of [1] to [6], which does not heat with an external heat source.
[8] A garnet-type composite metal oxide containing Li, La, Zr and O.
The crystallite diameter is 30 nm or more,
A garnet-type composite metal oxide having a grain-aggregated structure and having a major axis of 90% or more of primary particles having a major axis of 3 μm or less on a number basis.
[9] A garnet-type composite metal oxide containing Li, La, Zr and O.
A garnet-type composite metal oxide having a BET specific surface area diameter of 1.5 μm or less.
[10] The garnet-type composite metal oxide according to [8] or [9], which further contains at least one of Al and Ga and has a cubic crystal system.
[11] A solid electrolyte material for a secondary battery containing the garnet-type composite metal oxide according to [10].

According to the present invention for producing a garnet-type composite metal oxide containing Li, La, Zr and O by a mechanochemical method, it is possible to provide a composite metal oxide having good crystallinity.

FIG. 1A is a cross-sectional view perpendicular to the rotation axis of a grinding mill that can be used in the mechanochemical method, and FIG. 1B is a cross-sectional view taken along the line AA'of FIG. 1A. FIG. 2 is an XRD diffraction chart of Examples 1 and 2. FIG. 3 is a drawing-substituting photograph showing an SEM observation image of the LLZ obtained in Example 1. FIG. 4 is an XRD diffraction chart according to Examples 4 and 5. FIG. 5 is a drawing-substituting photograph showing a cross-sectional STEM observation image of the LLZ obtained in Examples 4 and 5.

The present invention relates to a method for producing a garnet-type composite metal oxide containing Li, La, Zr and O by a mechanochemical method. The garnet structure is generally _{represented by the composition formula of A 3} B ₂ C ₃ O ₁₂ , and in the garnet type composite metal oxide of the present invention containing Li, La, Zr and O, the position of A in the composition formula La ^{3+ occupies, Zr 4+} occupies the position B, ^{Li +} occupies the position C and the interstitial position, and can be represented by the composition formula of _{Li 7} La ₃ Zr ₂ O _12. In a preferred embodiment, a part of the Li ⁺ _{site in Li 7} La ₃ Zr ₂ O ₁₂ may be replaced with ^{Al 3+} and / or Ga ^3+. Hereinafter, in the present specification, the garnet-type composite metal oxide containing Li, La, Zr and O includes an embodiment in which a part of ^{the Li + site is replaced with Al 3+} and / or Ga ^3+. Called "LLZ". Further, in the LLZ of the present invention, ^{it is also permissible that a part of the La 3+} site is replaced with a dopant such as Ce or Eu.

In the present invention, Li source powder, La source powder, and Zr source powder are used as raw materials, and a mixture containing these raw material powders and flux is treated by a mechanochemical method, and the raw material powders are reacted with each other to produce LLZ. .. More specifically, the mechanochemical method can be carried out by shearing a mixture containing raw material powder while compressing it under dry conditions. Strain energy is accumulated in the raw material powder, and the energy is self-released to generate heat. It becomes energy, is spent on surface modification, crystal structure transition, or solid phase reaction. In the present invention, the raw material powder is mechanochemically treated in the presence of flux, and the generated energy creates a liquid phase on the surface of the raw material to promote the reaction between the raw material powders. Therefore, according to the present invention, the desired inorganic compound can be obtained in a very short time only by mechanochemical treatment without performing high-temperature heat treatment. Further, according to the present invention for producing LLZ, when compared after mechanochemical treatment (and not calcined), a compound having higher crystallinity than the YAG crystal disclosed in Patent Document 1 can be obtained. Obtainable.

As the raw material powder, Li source powder, La source powder, and Zr source powder are used, and preferably at least one of Al source powder and Ga source powder is used. By using at least one of the Al source powder and the Ga source powder, the cubic LLZ can be stabilized, and the LLZ crystal system can be made into a cubic crystal system.

Examples of the Li source powder, La source powder, Zr source powder, Al source powder and Ga source powder include oxides, carbonates, hydroxides and chlorides of each metal (Li, La, Zr, Al or Ga). , Alkoxide and the like can be used. The Li source powder is preferably a Li oxide or Li carbonate, the La source powder is preferably a La oxide or La hydroxide, and the Zr source powder is a Zr oxide or Zr hydroxide. Is preferable, the Al source powder is preferably an Al oxide or an Al hydroxide, and the Ga source powder is preferably a Ga oxide or a Ga hydroxide. It is preferable that all of the Li source powder, the La source powder, and the Zr source powder are oxide powders (Li oxide, La oxide, and Zr oxide) of each metal, and the Al source powder and the Ga source powder. When at least one of the above is used, it is preferable that the Al source powder and the Ga source powder are also oxide (Al oxide, Ga oxide) powder.

The ratio of Li source powder, La source powder, Zr source powder, Al source powder, and Ga source powder to be used may be the stoichiometric ratio of the target composition. In particular, when Al source powder and / or Ga source powder is used, it is preferable that the total amount of Al and Ga in the raw material powder is 0.05 or more in terms of molar ratio. The LLZ crystal system obtained by this can be made into a cubic crystal. The molar ratio is more preferably 0.06 or more, still more preferably 0.08 or more, and the upper limit is not limited, but is, for example, 0.2 or less.

Each raw material powder, it is also preferred that the powder characteristics is properly adjusted, for example, specific surface area by the BET method S _w (m ² / g) is preferably 0.5~25m ² / g. Further, it is possible to calculate a specific surface area diameter d _BET (nm) from the specific surface area S _w by the following equation.
d _BET = 6 / (ρ ・_Sw )
(In the above formula, ρ represents the theoretical density)

Preferred specific surface area diameter d _BET (nm) is 500 to 2000 nm for Li source powder, 400 to 700 nm for La source powder, 20 to 100 nm for Zr source powder, 80 to 200 nm for Al source powder, and 20 to 100 nm for Ga source powder. Is.

Examples of the flux include metal hydroxides, metal oxides and metal halides. All of these have actions such as generating a liquid phase between the raw material powders and increasing the contact area, and by using such a flux, the raw material powders can react with each other by the mechanochemical method. Examples of the metal hydroxide include Al (OH) ₃ , Ga (OH) ₃ , KOH, Sr (OH) ₂ , NaOH, Ba (OH) ₂ , Mg (OH) ₂ , LiOH and La (OH) _3. Etc., and at least one of these can be used. A preferred metal hydroxide is Al (OH) ₃ . Examples of the metal oxide include PbO and B ₂ O ₃ . Further, as the metal halide, metal fluoride and metal chloride are preferable, and examples of this metal include alkali metals, alkaline earth metals, Y, Al, Pb, Bi and Zn. The metal fluoride is preferably at least one selected from the group consisting _{of BaF 2} , YF ₃ , AlF ₃ and SrF _{3, and BaF 2} is particularly preferable. As the metal chloride, an alkali metal chloride is preferable, and LiCl is more preferable. As the metal halide, metal fluoride is preferable. The melting point of the flux is, for example, 200 to 1400 ° C., preferably 400 to 1300 ° C., and the specific surface area diameter d _BET determined from the BET specific surface area is, for example, 50 nm or more, more preferably 80 nm or more, and further preferably. Is 100 nm or more, and _{the upper limit of the specific surface area diameter d BET} is preferably 2000 nm or less, more preferably 1600 nm or less, further preferably 200 nm or less, and particularly preferably 150 nm or less. The amount of flux can be appropriately set in consideration of the type of raw material powder to be used and the balance with the conditions of mechanochemical treatment, and is, for example, 4 to 15% by mass with respect to the total amount of raw material powder.

As described above, the mechanochemical method can be carried out more specifically by shearing the mixture containing the raw material powder while compressing it under dry conditions. An example of this method will be described with reference to the drawings. FIG. 1 is a schematic view of a grinding mill capable of applying a compressive force and a shearing force to a mixture of raw material powders, FIG. 1 (a) is a cross-sectional view perpendicular to the rotation axis, and FIG. 1 (b) is a cross-sectional view. FIG. 1A is a cross-sectional view taken along the line AA'of FIG. 1 (a). The grinding mill of FIG. 1 includes a bottomed cylindrical container 1 and a rotor 2. The rotor 2 has a tip wing 3 having a curvature smaller than the inner circumference of the bottomed cylindrical container 1, and a clearance 4 is provided between the tip wing 3 and the inner circumference of the bottomed cylindrical container 1. .. Then, by rotating the rotor 2, the mixture 5 of the raw material powder and the flux receives the compressive force and the shearing force in the clearance 4.

The mechanochemical treatment conditions are not preferable because if the reaction conditions are too weak, the reaction between the raw material powders does not occur, and if the reaction conditions are too strong, the crystals once formed become amorphous. If the conditions for mechanochemical treatment are inappropriate, the conditions may be changed as appropriate according to the reason (unreacted, amorphized, etc.), the type and amount of raw material, and the type and amount of flux. For example, it is as follows.

The range of the clearance varies depending on the amount of raw material powder, the difference between the curvature of the tip blade of the rotor and the curvature of the inner circumference of the container, the processing power of the rotor, and the like, but is preferably less than 1 mm, for example. By doing so, a sufficient compressive force and a shearing force can be applied to the mixture of the raw material powders, and the reaction between the raw material powders is promoted. The clearance is preferably 0.9 mm or less, more preferably 0.8 mm or less. The lower limit of the clearance is, for example, 100 μm or more, preferably 0.5 mm or more.

The power of rotation of the rotor is, for example, 0.05 kW / g or more with respect to the total mass of the raw material powder. By increasing the rotational power, the solid-phase reaction between the raw material powders is promoted. The rotational power is preferably 0.06 kW / g or more, more preferably 0.08 kW / g or more, and particularly preferably 0.1 kW / g or more. The upper limit of the power of rotation is not particularly limited, but is, for example, 0.5 kW / g. The number of rotations of the rotor varies depending on the size of the device, the shape of the rotor, and the like, but the rotational power in the above range is, for example, 2000 to 6000 rpm, preferably 3000 to 5000 rpm.

The rotation time of the rotor can be appropriately set according to the rotational power of the rotor, but is, for example, 5 minutes or more, preferably 10 minutes or more, and more preferably 20 minutes or more. By rotating the rotor for 5 minutes or more (preferably 10 minutes or more), sufficient compressive force and shearing force can be applied to the raw material powder, so that the solid phase reaction of the raw material powder proceeds and LLZ can be obtained. The upper limit of the rotation time of the rotor is not particularly limited, but if it is too long, the crystallinity of the target compound will rather decrease and extra energy will be consumed, so it is preferably 30 minutes or less.

In the mechanochemical treatment, strain energy is accumulated in the raw material powder by shearing, and the energy is self-released to become heat energy, so that heat is generated. Therefore, it is also possible to carry out the production method of the present invention without heating with an external heat source. The mechanochemical treatment may be carried out in a state of heat generation, or may be carried out by cooling by water cooling or the like. In the mechanochemical treatment, the ultimate temperature of the cylindrical container may be, for example, 50 ° C. or higher, preferably 130 ° C. or higher, and 500 ° C. or lower.

The atmosphere of the mechanochemical treatment is not particularly limited, but may be any of an oxygen-containing atmosphere such as the atmosphere, an inert gas atmosphere, and a reducing gas atmosphere. Examples of the inert gas include nitrogen, helium, argon and the like (particularly nitrogen gas is preferable), and examples of the reducing gas include a mixed gas of the inert gas (particularly nitrogen gas) and 3 to 5% hydrogen gas. Can be mentioned.

The material of the bottomed cylindrical container is not particularly limited, and examples thereof include stainless steel such as SUS304 and carbon steel. Alternatively, a coating may be applied so that impurities are not mixed in the generated LLZ. The inner diameter of the container is, for example, 50 to 500 mm. Further, the number of tip blades may be 1 or more, preferably 2 or more, and usually 8 or less.

The LLZ obtained by mechanochemical treatment with flux shows good crystallinity, but may be calcined after mechanochemical treatment for the purpose of further increasing crystallinity. However, since good crystallinity is exhibited without firing after the mechanochemical treatment, it is possible to lower the firing temperature or shorten the firing time as compared with Patent Document 1 described above. For example, the firing temperature is 1300 ° C. or lower (the lower limit is, for example, 500 ° C. or higher), and the firing time is 20 hours or less (the lower limit is, for example, 30 minutes or more). Further, the fact that the firing is not performed or the firing conditions can be relaxed has an advantage that the deviation of the composition due to the volatilization of Li can be suppressed.

In the present invention, the flux may be removed by an acid after the raw material powder is reacted by the mechanochemical treatment. As the acid, an inorganic acid such as hydrochloric acid or sulfuric acid can be used. In the present invention, as described above, the LLZ synthesized by the mechanochemical method may be further calcined, but when it is not calcined, the flux is generated by an acid after reacting the metal oxide powder particularly by the mechanochemical treatment. It is preferable to remove it. When firing after the mechanochemical treatment, firing may be performed in the presence of flux, and the flux may be removed after firing. Firing in the presence of flux is preferable because the solid-phase-liquid phase reaction during firing is promoted. The treatment with acid may be, for example, 1 to 3 hours, and after the acid treatment, it is washed with pure water and then at about 100 to 400 ° C. (preferably 200 to 300 ° C.) for 1 hour or more (preferably 2 hours or more, It is more preferable to heat it for 3 hours or more, more preferably 4 hours or more, usually 10 hours or less) to sufficiently remove the water.

Among the above-mentioned production methods of the present invention, the LLZ obtained in a mode obtained by performing a mechanochemical treatment and then not firing contains Li, La, Zr and O, and if necessary, at least one of Al and Ga. It is a garnet-type composite metal oxide containing seeds, has good crystallinity, and is an aggregate of grains (fine grains) when observed with an electron microscope such as SEM (Scanning Electron Microscope) or STEM (Scanning Transmission Electron Microscope). The structure is observed.

Good crystallinity can be expressed by the crystallinity diameter calculated by the Scherrer equation shown in the following equation (1) from the full width at half maximum of the X-ray diffraction peak.
Dc = Kλ / βcosθ ・ ・ ・ (1)
Dc: crystallite diameter, λ: X-ray wavelength, K: Scherrer constant, β: full width at half maximum, θ: Bragg angle

The crystallite diameter of the LLZ of the present invention is 30 nm or more, preferably 35 nm or more, more preferably 40 nm or more, and usually 50 nm or less.

Further, when the LLZ of the present invention is observed with an electron microscope such as SEM or STEM at a magnification of 1000 to 5000 times, for example, it has not been calcined at a high temperature. The collective structure of is observed. Further, in the LLZ of the present invention, when observing the major axis of the particles having a grain assembly structure, the major axis of the primary particles of 90% or more of the particles based on the number is 3 μm or less (preferably 2 μm or less, more preferably 1.5 μm or less). It is more preferably 1.3 μm or less, and particularly preferably 1.2 μm or less). It is more preferable that the major axis range (including the preferable range) of the primary particles is 100% based on the number of particles, that is, all the particles are satisfied. On the other hand, in the LLZ obtained by the conventional sintering method, since the raw material is solid-solved at a high temperature, the interface of the raw material powder disappears and coarse particles are formed or the grain aggregate structure is not formed. It differs from the LLZ of the present invention in that the fine grain structure like the LLZ of the present invention is not observed. The primary particle is the smallest unit of the observed particle, and the major axis of the primary particle is the longest line segment among the line segments that pass through the center (centroid) of the particle and are separated by the outer circumference of the particle. And it is sufficient.

When the surface of the LLZ of the present invention is covered with a melt-solidified product, a cross section of the LLZ of the present invention cut at an arbitrary surface is observed with an electron microscope, and the grain assembly structure is observed in the cross section. The major axis of the particles (minimum unit) constituting the aggregated structure may also be measured in the cross section.

Further, the above-mentioned LLZ of the present invention is a garnet-type composite metal oxide containing Li, La, Zr and O, and is a garnet-type composite metal oxide having a BET specific surface area diameter of 1.5 μm or less. You can also. The BET specific surface area diameter of the LLZ of the present invention is preferably 1.3 μm or less, more preferably 1.0 μm or less, further preferably 800 nm or less, and the lower limit is, for example, 150 nm or more. In particular, it is preferable that the LLZ of the present invention, which is not covered with the melt-solidified product, satisfies the BET specific surface area diameter. The BET specific surface area diameter of the LLZ of the present invention can be calculated by the same formula as described in the above-mentioned specific surface area diameter of the raw material powder.

Further, the garnet-type composite metal oxide containing Li, La, Zr and O is usually stable in cubic crystals at room temperature, but in the LLZ of the present invention containing at least one of Al and Ga, Al and Ga Due to the cubic crystal stabilizing effect of, the crystal system can be made into cubic crystals. Further, when the final product obtained by the production method of the present invention was measured by XRD, the maximum peak area of La source powder (in the case of using La ₂ O ₃ as La source, a maximum peak area of La ₂ O ₃₎ The ratio of the maximum peak area of LLZ to the sum of the maximum peak areas of LLZ and LLZ is, for example, 20% to 60%.

Since the LLZ of the present invention has ionic conductivity, it can be suitably used as a solid electrolyte material for a secondary battery, and can also be used as a fluorescent material if a part of La sites is replaced with Ce, Eu, or the like.

This application claims the priority benefit under Japanese Patent Application No. 2018-147004 filed on August 3, 2018 and Japanese Patent Application No. 2018-161931 filed on August 30, 2018. To do. The entire contents of the specification of Japanese Patent Application No. 2018-147004 filed on August 3, 2018 and Japanese Patent Application No. 2018-161931 filed on August 30, 2018 are referred to in this application. Will be used for.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by the following examples, and it is of course possible to carry out the invention with appropriate modifications within the range that can be adapted to the above-mentioned purpose, and all of them are technical of the present invention. Included in the range.

Example 1
As a raw material of _{Li 6.25 Al 0.25 La 3 Zr 2} O 12, Li 2 O (( Ltd.) Wako Pure Chemical Industries, Ltd., purity: 99%, specific surface area S _w: 2.1m ² / g, a specific surface area diameter d _BET: 1421nm ), La ₂ O ₃ ((Ltd.) Wako pure chemical Industries, Ltd., purity: 99.9%, specific surface area S _w: 1.7m ² / g, a specific surface area diameter _{d BET: 543nm), ZrO 2} (( Ltd.) high purity chemical Co., purity: 98%, specific surface area S _w: 18.4m ² / g, a specific surface area diameter _{d BET: 57nm), Al 2} O 3 (( Ltd.) Wako pure chemical Industries, Ltd., purity: 99.99%, Specific surface area S _w : 11.3 m ² / g, specific surface area diameter d _BET : 134 nm), each of which produces a composite metal oxide with a chemical amount of _{Li 6.25} Al _0.25 La ₃ Zr ₂ O ₁₂ Weigh a total of 30 g in terms of ratio, and weigh 10 parts by mass of these raw materials and 100 parts by mass of the total amount of these raw materials. BaF ₂ (purity: 99.99%, specific surface area S _w : 9 m ² / g, specific surface area diameter d _BET : 137 nm, melting point: 1280 ° C.) was put into the grinding mill shown in FIG. The bottomed cylindrical container 1 is made of SUS304, the inner diameter thereof is 80 mm, and the clearance 4 between the inner circumference of the container 1 and the tip blade 3 of the rotor 2 is 0.8 mm. Such a grinding mill was rotated at a rotation speed of 4500 rpm and a required power of 3 kW for 20 minutes to perform mechanochemical treatment. The temperature reached by the container was about 260 ° C.

The crystal structure of the obtained sample was analyzed using an XRD (X-ray Diffraction analysis) apparatus manufactured by Bruker. The measurement was carried out with CuKα rays, and λ = 1.5418 nm and θ = 10 to 50 °. As a result, tetragonal LLZ in which a part of the Li site was replaced with Al was generated in the obtained sample. Further, when the crystallite diameter was determined from the half width of the diffraction peak showing the maximum intensity of XRD based on Scherrer's equation, it was 41 nm. Further, in the XRD of the obtained sample, the ratio of the maximum peak area of LLZ to the total of the maximum peak area of _{La 2} O _{3 and the maximum peak area of LLZ was 54%.}

Example 2
As a raw material of _{Li 6.25 Ga 0.25 La 3 Zr 2} O 12, Li 2 O (( Ltd.) Wako Pure Chemical Industries, Ltd., purity: 99%, specific surface area S _w: 2.1m ² / g, a specific surface area diameter d _BET: 1421nm ), La ₂ O ₃ ((Ltd.) Wako pure chemical Industries, Ltd., purity: 99.9%, specific surface area S _w: 1.7m ² / g, a specific surface area diameter _{d BET: 543nm), ZrO 2} (( Ltd.) high purity chemical Co., purity: 98%, specific surface area S _w: 18.4m ² / g, a specific surface area diameter _{d BET: 57nm), Ga 2} O 3 (( Ltd.) Wako pure chemical Industries, Ltd., purity: 99.99%, Specific surface area S _w : 10.4 m ² / g, specific surface area diameter d _BET : 90 nm), each of which produces a composite metal oxide with a chemical amount of _{Li 6.25} Ga _0.25 La ₃ Zr ₂ O ₁₂ A total of 30 g was weighed by the specific surface area. Next, these raw materials and, BaF ₂ 10 parts by weight of the total amount 100 parts by mass of the raw material (purity: 99.99%, the specific surface area S _w: 9m ² / g, a specific surface area diameter d _BET: 137 nm, Melting point: 1280 ° C.) was put into the grinding mill shown in FIG. The conditions of the grinding mill were the same as in Example 1, and the mechanochemical treatment was performed. The temperature reached by the container was about 260 ° C.

As a result of measuring the crystal structure of the obtained sample in the same manner as in Example 1, a tetragonal LLZ in which a part of Li sites was replaced with Ga was generated in the obtained sample. Further, when the crystallite diameter was determined from the half width of the diffraction peak showing the maximum intensity of XRD based on Scherrer's equation, it was 39 nm. Further, in the XRD of the obtained sample, the ratio of the maximum peak area of LLZ to the total of the maximum peak area of _{La 2} O _{3 and the maximum peak area of LLZ was 43%.}

Using MICROMERITICS ASAP2010, the specific surface area was calculated from the amount of nitrogen gas adsorbed on the obtained sample, and the specific surface area diameter was determined from the BET specific surface area and the density of the sample. As a result, the specific surface area was 1.8 m ² / g and the specific surface area diameter was 652 nm.

Example 3
Except that the raw material powder was weighed at a stoichiometric ratio of Li _5.5 Ga _0.5 La ₃ Zr ₂ O _{12 and the power of the grinding mill was 2.5 kW.} Mechanochemical treatment was performed in the same manner as in Example 2. The temperature reached by the container was about 260 ° C.

As a result of measuring the crystal structure of the obtained sample in the same manner as in Example 1, cubic LLZ in which a part of Li sites was replaced with Ga was generated in the obtained sample. Further, when the crystallite diameter was determined from the half width of the diffraction peak showing the maximum intensity of XRD based on Scherrer's equation, it was 31 nm. Further, in the XRD of the obtained sample, the ratio of the maximum peak area of LLZ to the total of the maximum peak area of _{La 2} O _{3 and the maximum peak area of LLZ was 24%.}

Using MICROMERITICS ASAP2010, the specific surface area was calculated from the amount of nitrogen gas adsorbed on the obtained sample, and the specific surface area diameter was determined from the BET specific surface area and the density of the sample. As a result, the specific surface area was 4.2 m ² / g and the specific surface area diameter was 280 nm.

Example 4
As a raw material for _{Li 5.5 Ga 0.5 La 3 Zr 2} O 12, Li 2 O (( Ltd.) Wako Pure Chemical Industries, Ltd., purity: 99%, specific surface area S _w: 2.1m ² / g, a specific surface area diameter d _BET: 1421nm ), La ₂ O ₃ ((Ltd.) Wako pure chemical Industries, Ltd., purity: 99.9%, specific surface area S _w: 1.7m ² / g, a specific surface area diameter _{d BET: 543nm), ZrO 2} (( Ltd.) high purity chemical Co., purity: 98%, specific surface area S _w: 18.4m ² / g, a specific surface area diameter _{d BET: 57nm), Ga 2} O 3 (( Ltd.) Wako pure chemical Industries, Ltd., purity: 99.99%, A chemical amount of a powder having a specific surface area S _w : 10.4 m ² / g and a specific surface area diameter d _BET : 90 nm) so that the composition of the composite metal oxide produced is Li _5.5 Ga _0.5 La ₃ Zr ₂ O _12. A total of 30 g was weighed by the specific surface area. Next, these raw materials and, LiCl 10 parts by weight of the total amount 100 parts by mass of the raw material (purity: 99.99%, the specific surface area S _w: 1.9m ² / g, a specific surface area diameter d _BET: 1504nm , Melting point: 613 ° C.) was put into the grinding mill shown in FIG. The bottomed cylindrical container 1 is made of SUS304, the inner diameter thereof is 80 mm, and the clearance 4 between the inner circumference of the container 1 and the tip blade 3 of the rotor 2 is 0.8 mm. Such a grinding mill was rotated at a rotation speed of 4274 rpm and a required power of 3 kW for 6 minutes to perform mechanochemical treatment. The temperature reached by the container was about 65 ° C.

The crystal structure of the obtained sample was analyzed using an XRD (X-ray Diffraction analysis) apparatus manufactured by Bruker. The measurement was carried out with CuKα rays, and λ = 1.5418 nm and θ = 10 to 50 °. As a result, as shown in FIG. 4, cubic LLZ (a part of Li site was replaced with Ga) was generated in the obtained sample. Moreover, when the ratio of the area of the maximum peak of LLZ to the total of the area of the maximum peak of LLZ and the area of the maximum peak of _{La 2} O ₃ was calculated from the XRD chart, it was 29%. Further, when the crystallite diameter was determined from the half width of the diffraction peak showing the maximum intensity of LLZ based on the Scheller's equation, it was 33.6 nm.

Further, when the cross section obtained by cutting the obtained LLZ was observed (magnification: 15000 times) with STEM (HD-2700) manufactured by Hitachi High-Technologies Corporation, as shown in FIG. It was confirmed that the major axis of the primary particles of the constituent particles was 3 μm or less. In FIG. 5, the portion having a high contrast (black or gray) is a molten solidified product.

Example 5
The mechanochemical treatment was performed under the same conditions as in Example 4 except that the rotation time of the grinding mill was 20 minutes (rotation speed was 4446 rpm). The ultimate temperature of the grinding mill container was about 290 ° C.

As a result of evaluating the crystal structure of the obtained sample and the formation ratio of LLZ in the same manner as in Example 4, cubic LLZ (FIG. 4) in which a part of Li sites was replaced with Ga was formed. The ratio of the area of the maximum peak of LLZ to the sum of the area of the maximum peak of LLZ and the area of the maximum peak of La ₂ O _{3 was 37%.} Further, the crystallite diameter calculated from the half width of the diffraction peak showing the maximum intensity of LLZ based on the Scheller's formula was 32.5 nm.

Further, when the cross section obtained by cutting the obtained LLZ was observed (magnification: 25000 times) with STEM (HD-2700) manufactured by Hitachi High-Technologies Corporation, as shown in FIG. It was confirmed that the major axis of the primary particles of the particles was 3 μm or less.

Comparative Example 1
The mechanochemical treatment was carried out in the same manner as in Example 1 except that _{BaF 2 was not used.} As a result of measuring the crystal structure of the obtained sample in the same manner as in Example 1, only the diffraction peak caused by the raw material powder was detected, and LLZ was not obtained.

Comparative Example 2
Y _2.97 Al ₅ O ₁₂ : _{Fluorescence that produces powders of Y 2} O ₃ , CeO ₂ , and Al ₂ O ₃ (all raw materials are manufactured by High Purity Chemical Co., Ltd.) as raw materials for ^{Ce 3 +} _0.03. A total of 30 g was weighed in a chemical quantity theory ratio in which the composition of the body was Y _2.97 Al ₅ O ₁₂ : Ce ^{3 +} _0.03. Next, 6 parts by mass of these raw materials and 6 parts by mass of BaF ₂ were charged into the grinding mill with respect to 100 parts by mass of the total amount of these raw materials. The bottomed cylindrical container 1 is made of SUS304 and has an inner diameter of 80 mm, and the clearance 4 between the inner circumference of the container 1 and the tip blade of the rotor 2 is 1.0 mm. Such a grinding mill was rotated at a rotation speed of 4500 rpm and a required power of 3 kW for 10 minutes to perform mechanochemical treatment.

The crystal structure of the obtained sample was analyzed using an XRD apparatus manufactured by Bruker. The measurement was carried out with CuKα rays, and λ = 1.5418 nm and θ = 10 to 50 °. As a result, a YAG phase was obtained in the crystals of the obtained sample. Further, when the crystallite size was determined from the half width of the XRD diffraction peak of the YAG phase, it was 26 nm.

The results of the above Examples and Comparative Examples are shown in Table 1.

Further, the XRD diffraction charts of Examples 1 and 2 are shown in FIG. 2, and the XRD diffraction charts of Examples 4 and 5 are shown in FIG.

According to Table 1, in Examples 1 to 5 in which LLZ was produced by mechanochemical treatment using flux, LLZ having excellent crystallinity, that is, having a crystallinity diameter of 30 nm or more could be produced. It can also be seen from FIGS. 2 and 4 that the LLZ is formed in Examples 1, 2, 4, and 5. Further, FIG. 3 shows an SEM observation image of the LLZ obtained in Example 1, and FIG. 5 shows a cross-sectional SEM observation image of the LLZ obtained in Examples 4 and 5. From FIGS. 3 and 5, it can be seen that the LLZ of the present invention has a grain assembly structure and the major axis of the primary particles is 3 μm or less. On the other hand, in Comparative Example 1 in which no flux was used, the raw material powder remained even after the mechanochemical treatment, and LLZ was not generated. Further, in Comparative Example 2 in which the target produced by the mechanochemical treatment was a YAG phosphor, although a YAG phase was obtained, good crystallinity as in the present invention could not be realized.

The garnet-type composite metal oxide of the present invention can be suitably used as a solid electrolyte material for a secondary battery, a fluorescent material, and the like.

1 Bottomed cylindrical container 2 Rotor 3 Tip wing 4 Clearance 5 Mixture of raw material powder and flux

Claims (11)

A method for producing a garnet-type composite metal oxide containing Li, La, Zr and O.
A garnet-type composite metal oxide characterized by treating a mixture containing a flux and a raw material powder containing a Li source powder, a La source powder, and a Zr source powder by a mechanochemical method and reacting the raw material powder. Production method. The production method according to claim 1, wherein the raw material powder further contains at least one of an Al source powder and a Ga source powder. The production method according to claim 1 or 2, wherein the crystallite diameter of the garnet-type composite metal oxide is 30 nm or more. The production method according to claim 2 or 3, wherein the crystal system of the garnet-type composite metal oxide is cubic. Bottomed cylindrical container and
It is equipped with a rotor with a tip wing with a curvature smaller than the inner circumference of this container.
A predetermined clearance is provided between the tip wing and the inner circumference of the container.
The production method according to any one of claims 1 to 4, wherein by rotating the rotor, the mixture containing the raw material powder and the flux is sheared while being compressed at the clearance. The production method according to claim 5, wherein the power of the rotor is 0.05 kW / g or more with respect to the total amount of the raw material powder, and the rotor is rotated for 10 minutes or more. The production method according to any one of claims 1 to 6, wherein heating by an external heat source is not performed. A garnet-type composite metal oxide containing Li, La, Zr and O.
The crystallite diameter is 30 nm or more,
A garnet-type composite metal oxide having a grain-aggregated structure and having a major axis of 90% or more of primary particles having a major axis of 3 μm or less on a number basis. A garnet-type composite metal oxide containing Li, La, Zr and O.
A garnet-type composite metal oxide having a BET specific surface area diameter of 1.5 μm or less. The garnet-type composite metal oxide according to claim 8 or 9, further comprising at least one of Al and Ga and having a cubic crystal system. The solid electrolyte material for a secondary battery containing the garnet-type composite metal oxide according to claim 10.

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