Preparation method of lial5o8 powder and lialon transparent ceramic

Abstract

The application provides a preparation method of LiAl5O8 powder and LiAlON transparent ceramic and belongs to the technical field of transparent ceramic materials. After slurry is prepared, the preparation method is freezing drying first to obtain loose mixed material without large-particle hard agglomeration, then low-temperature solid-phase reaction is carried out, and the material is rotated and mixed every 30 minutes during the heat preservation process to realize uniform heat treatment of the material. In the application, the preparation method of the LiAl5O8 powder is a low-temperature solid-phase reaction method, and the reaction condition is simple, the cost is low, and the efficiency is high. The prepared LiAl5O8 powder is single-phase, the particle is small, the distribution is uniform, there is no large-particle agglomeration, the reaction activity is high, the dispersibility is good, and the subsequent high-energy ball milling is not needed for refinement, so the prepared LiAl5O8 powder can be directly applied to the preparation of the LiAlON transparent ceramic, and the optical transmittance of the transparent ceramic is improved.

Description

Technical Field

[0001] This invention belongs to the field of transparent ceramic materials technology, specifically relating to a method for preparing LiAl5O8 powder and LiAlON transparent ceramics. Background Technology

[0002] LiAlON transparent ceramics are spinel-structured solid solutions formed by dissolving Li+ ions in γ-AlON. They possess mechanical and optical properties comparable to sapphire and AlON, and are expected to be used in infrared windows, radomes, and transparent armor, thus attracting widespread attention from researchers both domestically and internationally.

[0003] Traditional nitrogen oxide powders are typically prepared using solid-state reaction methods. However, in the preparation of LiAlON powder, a single Li compound source is commonly used, such as Li₂CO₃, LiNO₃, or LiF. Li₂CO₃ has a melting point of 720℃ and a boiling point of 1342℃; LiNO₃ has a melting point of 264℃ and a boiling point of 600℃; and LiF has a melting point of 845℃ and a boiling point of 1681℃. It is evident that Li₂CO₃, LiNO₃, and LiF are highly volatile at high temperatures, leading to uneven composition and difficulty in controlling the composition of the LiAlON powder. This results in low optical transmittance of the prepared LiAlON transparent ceramic and poor reproducibility of the preparation process, which is one of the factors limiting the widespread application of this material.

[0004] LiAl5O8 is an important composite oxide Li source, primarily used as a phosphor luminescent material in current technology. In recent years, its application in electrochemistry has been increasingly reported. Due to its high melting point of 1915℃, LiAl5O8 has become an ideal material for preparing LiAlON as a Li source.

[0005] However, the preparation of LiAl5O8 is quite difficult, and there are very few commercially available powders of this type. Furthermore, it is generally prepared using a high-temperature solid-state reaction method, which is costly and results in low purity, making it unsuitable as a Li source for preparing transparent ceramics. In recent years, a method combining sol-gel and low-temperature auto-ignition has been developed to prepare LiAl5O8. This method has advantages such as uniform raw material mixing, low reaction temperature, and high powder activity. However, its complex and cumbersome physicochemical reactions, long preparation cycle, and low efficiency also limit its further application. Summary of the Invention

[0006] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a method for preparing LiAl5O8 powder with simple preparation method, uniform powder composition and high reactivity, and LiAlON transparent ceramic.

[0007] One objective of this invention is to provide a method for preparing LiAl5O8 powder, the method comprising:

[0008] S1, preparing the slurry;

[0009] Nano α-Al2O3 powder and nano Li-containing compound powder were mixed, and then water, alumina grinding balls and dispersant were added. The mixture was ball-milled for 24-48 hours and then sieved to obtain a slurry.

[0010] S2, freeze-dried;

[0011] The slurry is freeze-dried by first cooling it to -40℃ to -55℃ and holding it at that temperature for 2 hours, then evacuating it to below 10Pa, and then heating it to 15℃ to 30℃ and holding it at that temperature for 5 hours to 8 hours to obtain a dried mixture.

[0012] S3, low-temperature solid-state reaction;

[0013] The mixture is placed in an alumina crucible, heated to 700℃~950℃, and held for 2h~6h. Then it is cooled to room temperature with the furnace and sieved to obtain LiAl5O8 powder. During the holding process, the alumina crucible is driven to rotate 10 times at a speed of 40~60r / min every 30min. The alumina crucible has an air inlet and an air outlet.

[0014] Preferably, the ratio of α-Al₂O₃ to the Li-containing compound satisfies the molar ratio of Al to Li as 5:1.

[0015] Preferably, the Li-containing compound includes Li₂CO₃ and / or LiF.

[0016] Preferably, the mass ratio of α-Al2O3 and Li-containing compound powder, grinding balls and water is 1:2:3 to 5.

[0017] Preferably, the dispersant is 1% to 4% of the mass of α-Al2O3 and Li-containing compound powder.

[0018] Preferably, the particle size of the nano-α-Al2O3 powder is 50nm to 200nm.

[0019] Preferably, the purity of α-Al2O3 is ≥99%.

[0020] Preferably, the particle size of the nano-Li-containing compound powder is 50 nm to 200 nm.

[0021] Preferably, the purity of the Li-containing compound is ≥99%.

[0022] Preferably, in step S1, the ball milling is performed using a drum ball mill or a planetary mill.

[0023] Preferably, in step S2, the cooling rate is 3℃~5℃ / min.

[0024] Preferably, in step S2, the heating rate is 1℃~3℃ / min.

[0025] Preferably, in step S3, the heating rate is 3℃~5℃ / min.

[0026] Preferably, in step S3, the inner surface of the alumina crucible has wedge-shaped protrusions.

[0027] Preferably, in step S3, the atmosphere inside the furnace is air.

[0028] Preferably, a 200-mesh sieve is used for sieving in step S3.

[0029] The second objective of this invention is to provide a LiAlON transparent ceramic, wherein the LiAlON transparent ceramic uses LiAl5O8 powder prepared by the method described above as the Li source.

[0030] The beneficial effects of this invention include:

[0031] This invention provides a method for preparing LiAl5O8 powder. After preparing the slurry, the mixture is first freeze-dried to obtain a loose, non-agglomerated mixture. Then, a low-temperature solid-state reaction is carried out. During the heat treatment process, the material is rotary-mixed every 30 minutes. In this invention, the method for preparing LiAl5O8 powder is a low-temperature solid-state reaction method, which is simple, low-cost, and highly efficient. The obtained LiAl5O8 powder has a single-phase crystal structure, with fine, uniformly distributed particles, no large particle agglomeration, high reactivity, and good dispersibility. It can be directly applied to the preparation of LiAlON transparent ceramics without further high-energy ball milling, which is beneficial for improving the optical transmittance of transparent ceramics. Attached Figure Description

[0032] Figure 1 The X-ray diffraction (XRD) patterns of the LiAl5O8 powders prepared as described in Examples 1, 2, and 3 are shown below.

[0033] Figure 2-1 The image shows the SEM image of the LiAl5O8 powder prepared in Example 1.

[0034] Figure 2-2 The image shows the SEM image of the LiAl5O8 powder prepared in Example 2.

[0035] Figure 2-3 The image shows the SEM image of the LiAl5O8 powder prepared as described in Example 3.

[0036] Figure 3The LiAlON transparent ceramic samples prepared in Comparative Examples 1, 2 and 3;

[0037] Figure 4 The transmittance curves are for the LiAlON transparent ceramic samples prepared in Comparative Example 1, Comparative Example 2 and Example 3. Detailed Implementation

[0038] The following description includes certain specific details to provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that the embodiments can be implemented without employing one or more of these specific details, but using other methods, components, materials, etc.

[0039] Unless otherwise required by the present invention, throughout the specification and the following claims, the words “comprising” and “including” shall be interpreted in an open-ended, inclusive sense, meaning “including but not limited to”.

[0040] Throughout this specification, the terms "an embodiment," "an embodiment," "a preferred embodiment," or "some embodiments" refer to including, in at least one embodiment, a specific reference element, structure, or feature related to that embodiment. Therefore, the phrases "in an embodiment," "in a preferred embodiment," or "in some embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. Furthermore, specific elements, structures, or features may be combined in one or more embodiments in any suitable manner.

[0041] According to a first aspect of the present invention, a method for preparing LiAl5O8 powder is provided, the method comprising:

[0042] S1, preparing the slurry;

[0043] Nano-α-Al2O3 powder and nano-Li-containing compound powder are mixed, and then water, alumina grinding balls and dispersant are added. The mixture is ball-milled for 24-48 hours and then sieved to obtain a slurry.

[0044] In this invention, the ball milling time is, for example, 24h, 26h, 28h, 30h, 32h, 36h, 38h, 40h, 42h, 46h, 44h, or 48h. The purpose of ball milling is to further refine the nano-α-Al₂O₃ powder and nano-Li-containing compound powder, and to add a dispersant for uniform dispersion. The dispersant used is polyacrylate. After ball milling, the alumina grinding balls are removed using a 150-mesh sieve to obtain a uniformly dispersed slurry. The dispersant in the slurry will be removed in the low-temperature solid-phase reaction step.

[0045] S2, freeze-dried;

[0046] The slurry is freeze-dried by first cooling it to -40℃ to -55℃ and holding it at that temperature for 2 hours, then evacuating it to below 10Pa, and then heating it to 15℃ to 30℃ and holding it at that temperature for 5 hours to 8 hours to obtain a dried mixture.

[0047] In this invention, the uniformly dispersed slurry is first completely frozen, and then the water in the slurry is sublimated directly into a gaseous state under vacuum without going through a liquid state, resulting in a mixture with a loose structure and no large hard agglomerates.

[0048] In this invention, during freezing, the cooling temperature is, for example, -40°C, -41°C, -42°C, -43°C, -44°C, -45°C, -46°C, -47°C, -48°C, -49°C, -50°C, -51°C, -52°C, -53°C, -54°C, or -55°C. The heating temperature is, for example, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C.

[0049] S3, low-temperature solid-state reaction;

[0050] The mixture is placed in an alumina crucible, heated to 700℃~950℃, and held for 2h~6h. Then it is cooled to room temperature with the furnace and sieved to obtain LiAl5O8 powder. During the holding process, the alumina crucible is driven to rotate 10 times at a speed of 40~60r / min every 30min. The alumina crucible has an air inlet and an air outlet, and the inner wall of the alumina crucible is provided with wedge-shaped protrusions of the same material.

[0051] In this invention, since the mixture obtained by freeze drying has a loose structure and no large hard agglomerates, it is conducive to heat transfer inside the mixture during the heating process. Therefore, the required reaction temperature is also lower. In addition, driving the alumina crucible to rotate 10 revolutions at a speed of 40 to 60 r / min every 30 minutes is more conducive to achieving uniform heat treatment of the material, thereby improving the reaction uniformity and reaction rate of the material.

[0052] Because the LiAl5O8 grains obtained from high-temperature reactions are relatively large, they are prone to forming hard agglomerates, increasing porosity and defects. When used to prepare LiAlON transparent ceramics, their reactivity is low during solid-state reactions with other components, leading to uneven reactions and affecting the optical transmittance of the transparent ceramics. In this invention, a low-temperature preparation method is used, which facilitates the formation of LiAl5O8 powder with a single crystal phase structure, resulting in a more stable crystal phase structure. Furthermore, the powder has fine particles, uniform distribution, no large particle agglomeration, high reactivity, and good dispersibility. It can be directly applied to the preparation of LiAlON transparent ceramics without subsequent high-energy ball milling, thus improving the optical transmittance of the transparent ceramics.

[0053] Preferably, the low-temperature solid-phase reaction step is carried out in a rotary furnace.

[0054] In a preferred embodiment of the present invention, the ratio of α-Al2O3 to the Li-containing compound satisfies the molar ratio of Al to Li as 5:1.

[0055] Preferably, the Li-containing compound includes Li₂CO₃ and / or LiF.

[0056] In this invention, when Li2CO3 is used as the Li-containing compound, the molar ratio of α-Al2O3 to Li2CO3 is 5:1; when LiF is used as the Li-containing compound, the molar ratio of α-Al2O3 to LiF is 5:2; when both Li2CO3 and LiF are used as the Li-containing compound, the amount of α-Al2O3 is n1, the amount of Li2CO3 is n2, and the amount of LiF is n3, then n1:(2n2+n3)=5:2.

[0057] In a preferred embodiment of the present invention, the mass ratio of α-Al2O3 and Li-containing compound powder, grinding balls and water is 1:2:3 to 5, for example 1:2:3, 1:2:3.5, 1:2:4, 1:2:4.5 or 1:2:5.

[0058] In a preferred embodiment of the present invention, the dispersant is 1% to 4% of the mass of α-Al2O3 and Li-containing compound powder, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%.

[0059] In a preferred embodiment of the present invention, the particle size of the nano α-Al2O3 powder is 50nm to 200nm, for example, 50nm, 70nm, 90nm, 100nm, 110nm, 130nm, 150nm, 160nm, 170nm, 190nm or 200nm.

[0060] Preferably, the purity of α-Al2O3 is ≥99%.

[0061] In a preferred embodiment of the present invention, the particle size of the nano-Li-containing compound powder is 50nm to 200nm, for example, 50nm, 70nm, 90nm, 100nm, 110nm, 130nm, 150nm, 160nm, 170nm, 190nm or 200nm.

[0062] Preferably, the purity of the Li-containing compound is ≥99%.

[0063] In a preferred embodiment of the present invention, in step S1, the ball milling is performed using a drum ball mill or a planetary mill.

[0064] In a preferred embodiment of the present invention, in step S2, the cooling rate is 3℃~5℃ / min.

[0065] Preferably, in step S2, the heating rate is 1℃~3℃ / min.

[0066] In a preferred embodiment of the present invention, in step S3, the heating rate is 3°C to 5°C / min.

[0067] In a preferred embodiment of the present invention, in step S3, the inner surface of the alumina crucible has a wedge-shaped protrusion. The material of the wedge-shaped protrusion is the same as that of the alumina crucible. The wedge-shaped protrusion creates disturbance during rotation, which facilitates the full dispersion of powder.

[0068] In a preferred embodiment of the present invention, in step S3, the atmosphere inside the furnace is air.

[0069] In a preferred embodiment of the present invention, a 200-mesh sieve is used for sieving in step S3.

[0070] According to a second aspect of the present invention, a LiAlON transparent ceramic is provided, wherein the LiAlON transparent ceramic uses LiAl5O8 powder prepared by the method described above as a Li source.

[0071] Specifically, the preparation method of the LiAlON transparent ceramic includes:

[0072] After mixing α-Al2O3 nanopowder, AlN nanopowder and LiAl5O8 prepared by the invention, the mixture is molded, sintered, subjected to static pressing, and then polished to obtain LiAlON transparent ceramic.

[0073] Example

[0074] The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0075] Example 1

[0076] S1 is used to prepare the slurry;

[0077] By weight, 87.33 parts α-Al2O3, 12.67 parts Li2CO3, 200 parts alumina grinding balls and 400 parts water were mixed, and 1.5 parts dispersant were added. The mixture was then ball-milled using a drum ball mill for 48 hours to obtain a slurry.

[0078] S2 freeze-drying;

[0079] Pour the slurry obtained in step S1 into a tray, insert a thermocouple, place it in a freeze dryer, cool it from room temperature to -40°C at a rate of 5°C / min, and keep it at that temperature for 2 hours. Then turn on the vacuum pump and evacuate to below 10Pa. Then, under this vacuum, heat it to 25°C at a rate of 3°C / min and keep it at that temperature for 6 hours. Then open the gas valve, take out the tray, and obtain the mixture. The obtained mixture is loose and has no large particles or hard agglomerates.

[0080] S3 Low-temperature solid-state reaction;

[0081] The mixture obtained in step S2 is poured into the feed inlet of a rotary furnace, as shown in patent publication number CN104482757A. Under an air atmosphere, the temperature is raised to 750°C at a rate of 3°C / min, held for 4 hours, and the crucible is rotated 10 times at a speed of 50 r / min every 30 minutes. Finally, the mixture is cooled to room temperature with the furnace and sieved through a 200-mesh nylon sieve to obtain a white powder. X-ray diffraction (XRD) phase analysis shows... Figure 1 As shown, the LiAl5O8 powder is a single-phase LiAl5O8, with no other impurity phases present. Scanning electron microscopy (SEM) testing confirms this. Figure 2-1 As shown, the particle size of LiAl5O8 powder is about 1 μm, and the particle size distribution of LiAl5O8 powder is relatively uniform.

[0082] Example 2

[0083] S1 is used to prepare the slurry;

[0084] By weight, 90.8 parts α-Al2O3, 9.2 parts LiF, 200 parts alumina grinding balls and 500 parts water were mixed, and 3 parts dispersant were added. The mixture was then milled using a planetary mill for 24 hours to obtain a slurry.

[0085] S2 freeze-drying;

[0086] Pour the slurry obtained in step S1 into a tray, insert a thermocouple, place it in a freeze dryer, cool it from room temperature to -50°C at a rate of 3°C / min, and keep it at that temperature for 2 hours. Then turn on the vacuum pump and evacuate to below 10Pa. Then, under this vacuum, heat it to 30°C at a rate of 2°C / min and keep it at that temperature for 5 hours. Then open the gas valve, take out the tray, and obtain the mixture. The obtained mixture is loose and has no large particles or hard agglomerates.

[0087] S3 Low-temperature solid-state reaction;

[0088] The mixture obtained in step S2 is poured into the feed inlet of a rotary furnace, as shown in patent publication number CN104482757A. Under an air atmosphere, the temperature is raised to 900°C at a rate of 5°C / min, held for 3 hours, and the crucible is rotated 10 times at a speed of 50 r / min every 30 minutes. Finally, the mixture is cooled to room temperature with the furnace and sieved through a 200-mesh nylon sieve to obtain a white powder. X-ray diffraction (XRD) phase analysis shows... Figure 1 As shown, the LiAl5O8 powder is a single-phase LiAl5O8, with no other impurity phases present. Scanning electron microscopy (SEM) testing confirms this. Figure 2-2 As shown, the particle size of LiAl5O8 powder is about 1 μm, and the particle size distribution of LiAl5O8 powder is relatively uniform.

[0089] Example 3

[0090] S1 is used to prepare the slurry;

[0091] By weight, 89.01 parts α-Al2O3, 6.45 parts Li2CO3, 4.54 parts LiF, 200 parts alumina grinding balls and 400 parts water were mixed, and 4 parts dispersant were added. The mixture was then ball-milled using a drum ball mill for 48 hours to obtain a slurry.

[0092] S2 freeze-drying;

[0093] After sieving the slurry obtained in step S1, pour it into a tray, insert a thermocouple, and place it in a freeze dryer. Cool it from room temperature to -55°C at a rate of 4°C / min and keep it at that temperature for 2 hours. Then turn on the vacuum pump and evacuate it to below 10Pa. Then, under this vacuum, heat it to 20°C at a rate of 1°C / min and keep it at that temperature for 8 hours. Then open the gas valve, take out the tray, and obtain the mixture. The obtained mixture is loose and has no large particles or hard agglomerates.

[0094] S3 Low-temperature solid-state reaction;

[0095] The mixture obtained in step S2 was poured into an alumina crucible in a rotary furnace, as shown in patent publication CN104482757A. Under an air atmosphere, the temperature was increased to 950°C at a rate of 4°C / min, held for 2 hours, and the crucible was rotated 10 times at 50 r / min every 30 minutes. Finally, the mixture was cooled to room temperature with the furnace and sieved through a 200-mesh nylon sieve to obtain a white powder. X-ray diffraction (XRD) phase analysis showed... Figure 1 As shown, the LiAl5O8 powder is a single-phase LiAl5O8, with no other impurity phases present. Scanning electron microscopy (SEM) testing confirms this. Figure 2-3 As shown, the particle size of LiAl5O8 powder is about 1 μm, and the particle size distribution of LiAl5O8 powder is relatively uniform.

[0096] S4 Preparation of Transparent Ceramics

[0097] LiAl5O8, prepared by mixing 80 parts by weight of α-Al2O3, 12 parts by weight of AlN, and 8 parts by weight of S3, was molded and then sintered at 1750℃ under a nitrogen atmosphere for 15 hours. Following this, it underwent hot isostatic pressing at 1800℃ for 8 hours at a pressure of 200 MPa to obtain transparent LiAlON ceramic samples. After surface polishing, as shown... Figure 3 As shown in Figure c, the optical transmittance was measured after surface polishing, and the transmittance curve is shown in Figure c. Figure 4 As shown in c.

[0098] Comparative Example 1

[0099] 86 parts by weight of α-Al₂O₃, 12.8 parts by weight of AlN, and 1.2 parts by weight of Li₂CO₃ were mixed, molded, and then sintered at 1750℃ under a nitrogen atmosphere for 15 hours. Following this, hot isostatic pressing was performed at 1800℃ for 8 hours at a pressure of 200 MPa to prepare transparent LiAlON ceramic samples. After surface polishing, as shown... Figure 3 As shown in Figure a, the optical transmittance was measured after surface polishing, and the transmittance curve is shown in Figure a. Figure 4 As shown in Figure a.

[0100] Comparative Example 2

[0101] S1 is used to prepare the slurry;

[0102] By weight, 89.01 parts α-Al2O3, 6.45 parts Li2CO3, 4.54 parts LiF, 200 parts alumina grinding balls and 400 parts water were mixed, and 4 parts dispersant were added. The mixture was then ball-milled using a drum ball mill for 48 hours to obtain a slurry.

[0103] S2 drying;

[0104] The slurry obtained in step S1 is sieved and poured into a tray, placed in a forced-air drying oven, and dried at 60°C for 24 hours to obtain a large-lump mixture. This mixture is then crushed in a mortar to obtain the final mixture.

[0105] S3 solid-phase reaction;

[0106] The mixture obtained in step S2 was poured into an alumina crucible, which was then placed in a high-temperature muffle furnace. The temperature was increased to 1100°C at a rate of 4°C / min and held for 6 hours. Finally, the mixture was cooled to room temperature with the furnace. The resulting powder was relatively coarse and could not be used directly. After secondary crushing and grinding for 24 hours, it was sieved through a 200-mesh nylon sieve to obtain white LiAl5O8 powder.

[0107] S4 is used to prepare transparent ceramics;

[0108] LiAl5O8, prepared by mixing 80 parts by weight of α-Al2O3, 12 parts by weight of AlN, and 8 parts by weight of S3, was molded and then sintered at 1750℃ under a nitrogen atmosphere for 15 hours. Following this, it underwent hot isostatic pressing at 1800℃ for 8 hours at a pressure of 200 MPa to obtain transparent LiAlON ceramic samples. After surface polishing, as shown... Figure 3 As shown in Figure b, the optical transmittance was measured after surface polishing, and the transmittance curve is shown in Figure 1. Figure 4 As shown in b.

[0109] In this invention, the X-ray diffraction (XRD) patterns of the LiAl5O8 powder prepared in Examples 1, 2, and 3 are as follows: Figure 1 As shown, the XRD diffraction patterns indicate that single-phase LiAl5O8 powder was synthesized in Examples 1-3 without the formation of other impurities, thus achieving the low-temperature preparation of the powder.

[0110] The SEM images of the LiAl5O8 powders prepared in Examples 1, 2, and 3 are as follows: Figure 2-1 , Figure 2-1 and Figure 2-3 As shown, the powder particles are fine, evenly distributed, and without large particle agglomeration, meeting the requirements for powder in the preparation of transparent ceramics.

[0111] Figure 3In Figures a, b, and c, the LiAlON transparent ceramic samples prepared in Comparative Examples 1, 2, and 3, respectively, are shown. As can be seen from the photographs, the LiAlON transparent ceramic samples prepared in Comparative Examples 2 and 3 exhibit superior optical properties compared to those prepared in Comparative Examples 1, 2, and 3. This is because using the composite oxide LiAl5O8 powder as the Li source reduces inhomogeneities and scattering sources compared to using the single compound Li2CO3 as the Li source. Furthermore, the LiAl5O8 composite Li source prepared in Example 3 using the method of this invention exhibits better activity and stability compared to the LiAl5O8 powder prepared using the prior art in Comparative Example 2, resulting in LiAlON transparent ceramics with lower haze and superior optical properties.

[0112] Figure 4 The transmittance curves of the LiAlON transparent ceramic samples prepared in Comparative Examples 1, 2 and 3 are shown. The LiAlON sample using the composite oxide LiAl5O8 powder prepared in Example 3 as the Li source has the highest linear transmittance in the range of 0.25 μm to 5 μm, which intuitively illustrates the reliability and effectiveness of the method of the present invention.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing LiAl5O8 powder, characterized by, The preparation method comprises: S1, preparing a slurry; After mixing nano α-Al2O3 powder and nano Li-containing compound powder, water, alumina grinding balls and a dispersing agent are added, and ball milling is performed for 24 h~48 h, and after screening, the slurry is obtained; S2, freeze-drying; The slurry is subjected to freeze-drying, and first, the temperature is lowered to -40℃~-55℃ at a rate of 3℃~5℃ / min, and after holding for 2 h, the vacuum is extracted to below 10 Pa, and then the temperature is raised to 15℃~30℃, and after holding for 5 h~8 h, the dried mixture is obtained; S3, low-temperature solid-phase reaction; The mixture is placed in an alumina crucible, and after being heated to 700℃~950℃, it is held for 2 h~6 h, and then cooled to room temperature with the furnace, and after screening, the LiAl5O8 powder is obtained; during the holding process, the alumina crucible is driven to rotate at a speed of 40~60 r / min for 10 turns every 30 min; the alumina crucible has one gas inlet and one gas outlet, and the inner surface of the alumina crucible has wedge-shaped protrusions.

2. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, The ratio of α-Al2O3 to the Li-containing compound satisfies that the molar ratio of Al to Li is 5:

1.

3. The method for preparing LiAl5O8 powder as described in claim 2, characterized in that, The Li-containing compound comprises Li2CO3 and / or LiF.

4. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, The mass ratio of the α-Al2O3 and Li-containing compound powder, grinding balls and water is 1:2:3~5.

5. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, The dispersing agent is 1%~4% of the mass of the α-Al2O3 and Li-containing compound powder.

6. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, The particle size of the nano α-Al2O3 powder is 50nm~200nm.

7. The method for preparing LiAl5O8 powder as described in claim 6, characterized in that, The purity of the α-Al2O3 is ≥99%.

8. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, The particle size of the nano Li-containing compound powder is 50nm~200nm.

9. The method for preparing LiAl5O8 powder as described in claim 8, characterized in that, The purity of the Li-containing compound is ≥99%.

10. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, In step S1, the ball milling uses a drum ball mill or a planetary mill.

11. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, In step S2, the temperature rising rate is 1℃~3℃ / min.

12. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, In step S3, the temperature rising rate is 3℃~5℃ / min.

13. The method for preparing LiAl5O8 powder as described in claim 1, characterized in that, In step S3, the atmosphere in the furnace is air.

14. The method for preparing LiAl5O8 powder according to any one of claims 1-13, characterized in that, In step S3, a 200-mesh screen is used for screening.

15. A LiAlON transparent ceramic, characterized in that, The LiAlON transparent ceramic uses the LiAl5O8 powder prepared by the method of any one of claims 1~14 as a Li source.

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