Electronic-grade hafnium oxide as well as preparation method and application thereof

Abstract

The invention discloses electronic-grade hafnium oxide and a preparation method and application thereof, and relates to the technical field of high-dielectric-constant materials, and the preparation method comprises the following steps: carrying out chlorination reaction on crushed coarse hafnium oxide and graphite powder to prepare coarse hafnium tetrachloride; purifying the crude hafnium tetrachloride by adopting a molten salt purification method and / or a hydrogenation purification method to prepare high-purity hafnium tetrachloride; the method comprises the following steps: introducing high-purity hafnium tetrachloride into a sublimation furnace, introducing oxygen and an AlCl3 gas-phase catalyst into the sublimation furnace, and oxidizing the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine; and dechlorinating the hafnium oxide particles through a fluidized bed to obtain the electronic-grade hafnium oxide. The hafnium oxide prepared by the preparation method not only has electronic-grade ultra-high purity, but also overcomes various defects of synthesis by using hafnium tetrachloride water; and the technological process is simple, the production efficiency is high, and the production cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of high dielectric constant materials, and in particular to electronic-grade hafnium oxide and a preparation method and application thereof. Background Art

[0002] Electronic-grade ultra-high-purity hafnium oxide is primarily used in the semiconductor chip industry, particularly for high-K dielectric constant materials. It serves as the gate dielectric layer in high-end chip transistors. The rapid advancement of information technology has driven a growing demand for high-performance materials in the semiconductor industry. Electronic-grade ultra-high-purity hafnium oxide products have already replaced imports in 5G communication devices, high-end optical lenses, fiber lasers, and advanced memory chips. The application of ultra-high-purity hafnium oxide materials in memory chips will continue to rise. The booming development of artificial intelligence has driven the rapid advancement of the storage industry, further driving market demand for hafnium oxide. Therefore, it is necessary to promote high-quality development of the high-purity zirconium oxide / hafnium oxide / hafnium oxychloride material industry and improve product quality consistency and reliability. As a core precursor material for atomic layer deposition (ALD) and chemical vapor deposition (CVD) processes in semiconductor manufacturing, high-purity electronic-grade hafnium oxide's purity control and micromorphology directly impact the quality of the gate oxide layer of high-end chips and the dielectric films of memory devices. It is a key material support for advanced processes such as 3D NAND flash memory and power semiconductors.

[0003] Electronic-grade hafnium oxide (HfO2) has very high purity requirements, reaching 5N (99.999%) or even higher. It is a key high-end electronic material used primarily in semiconductor devices (such as high-k gate dielectrics), memory devices, and optical coatings. Its production process requires strict control of purity (typically ≥99.999%), crystal structure, and particle morphology.

[0004] Currently, the main methods for purifying hafnium oxide impurities are solvent extraction and sublimation. Patent publication number CN113234923 A discloses a method for separating zirconium and hafnium from each other by solvent extraction to produce high-purity hafnium oxide. The method comprises the following steps: using hafnium oxide as the raw material, a pre-extraction solution is prepared with a hafnium oxide concentration of 50-80 g / L. The pre-extraction solution undergoes a first extraction process using 5-10% N₂35 as the first extractant, performing multi-stage cross-current extraction to separate the zirconium and hafnium from the pre-extraction solution and obtain a low-zirconium raffinate. A second extraction process is then performed using 20-40% N₂35 as the second extractant, performing multi-stage countercurrent extraction to obtain a low-zirconium strip solution. The strip solution is then precipitated with ammonia water, washed, dried, and calcined to obtain high-purity hafnium oxide. However, the purity of hafnium oxide produced using this process is insufficient to meet the requirements of memory chips.

[0005] Although the hafnium oxide preparation process in the prior art can obtain hafnium oxide with relatively high purity, it cannot achieve electronic grade ultra-high purity hafnium oxide, and its application in the semiconductor chip industry still has great limitations. Summary of the Invention

[0006] Hafnium oxide produced by the current hafnium oxide preparation process cannot meet the requirements of electronic grade ultra-high purity, and its application in the semiconductor chip industry still faces significant limitations. The purpose of the present invention is to provide an electronic grade hafnium oxide and its preparation method and application. The hafnium oxide produced by this preparation method not only has electronic grade ultra-high purity, but also has a high yield, a simple process flow, high production efficiency, and low production cost.

[0007] The present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present application provides a method for preparing electronic-grade hafnium oxide, comprising the following steps:

[0009] The crushed crude hafnium oxide is subjected to a chlorination reaction with graphite powder to obtain crude hafnium tetrachloride;

[0010] Purifying crude hafnium tetrachloride in turn by a molten salt purification method and a hydrogenation purification method to obtain high-purity hafnium tetrachloride;

[0011] Passing high-purity hafnium tetrachloride into a sublimation furnace, and passing oxygen and AlCl3 gas-phase catalyst into the sublimation furnace to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas;

[0012] The hafnium oxide particles are dechlorinated in a fluidized bed to produce electronic grade hafnium oxide.

[0013] The reaction mechanism for preparing hafnium oxide from hafnium tetrachloride is: HfCl4 + O2 → HfO2 + 2Cl2. This reaction uses AlCl3 as a vapor-phase catalyst, and the reaction temperature is controlled between 800°C and 1000°C. This reaction requires very high temperatures, and AlCl3, which evaporates at high temperatures and acts as a vapor-phase catalyst, lowers the required temperature and increases the reaction rate.

[0014] In the process of producing ultra-high-purity hafnium oxide (HfO2) from hafnium tetrachloride (HfCl4), AlCl3 as a catalyst mainly plays a role through the following mechanisms:

[0015] (1) Catalysis to form active intermediate complexes

[0016] During the reaction of AlCl3 and HfCl4, the breaking and forming of chemical bonds requires energy; at high temperatures, unstable complexes (such as [HfCl3·AlCl3] +), reducing the strength of the Hf-Cl bond and lowering the subsequent activation energy with O2. This complex is more likely to react with oxygen, promoting the breakage of Hf-Cl and the formation of Hf-O bonds.

[0017] HfCl4+AlCl3→[HfCl3·AlCl3] + +Cl - .

[0018] (2) Promote the removal of Cl by-products

[0019] According to Le Chatelier's principle, AlCl3 as a Lewis acid combines with Cl- released by the reaction (HfCl4+O2 (catalytic and high temperature) → HfO2+2Cl2) to generate stable AlCl4 - Complex ions, reducing Cl - concentration, pushing the reaction toward the formation of HfO2, reducing the probability of reverse reaction and indirectly reducing the activation energy.

[0020] (3) Promote seed effect

[0021] AlCl3 decomposes at high temperature to generate Al2O3 nanoparticles as a dispersant, providing nucleation sites for HfO2 and reducing the nucleation activation energy; preventing particle agglomeration during high-temperature calcination and ensuring uniform particle size of the product HfO2 particles.

[0022] (4) Activated oxygen molecules

[0023] AlCl3 can interact with O2 to generate active oxygen species (such as O - or O2 - ), which enhances the electrophilicity of oxygen, allowing it to strengthen the Hf center in the reaction HfCl4 and reduce the activation energy for O2 to participate in the reaction. This accelerates the oxidation process of HfCl4.

[0024] In the high-temperature gas-phase reaction, the presence of AlCl3 guides the oxidation of HfCl4 through a path with lower activation energy, passing through the intermediate Al-O-Hf structure, and finally decomposing into HfO2 and regenerating AlCl3, thus completing the catalytic cycle.

[0025] HfCl4+AlCl3→[HfCl3·AlCl3] + +Cl - ;

[0026] [HfCl3·AlCl3] + +O2→HfO2+AlCl3+2Cl2;

[0027] The introduction of AlCl₃ can significantly reduce the reaction temperature (e.g., from 1200°C to 800-1000°C), increasing the reaction rate and thus improving the photocatalytic performance or stability of the product. Furthermore, the recycling of AlCl₃ reduces production costs, aligning with environmental principles.

[0028] In summary, AlCl3 efficiently catalyzes the oxidation of HfCl4 to HfO2 through multiple mechanisms, including complex activation, promotion of Cl removal, promotion of seed effect, and oxygen activation.

[0029] In a specific embodiment, the crude hafnium oxide and graphite powder are both crushed to 300-500 mesh.

[0030] In a specific embodiment, the mass ratio of the crude hafnium oxide to the graphite powder is (15-20):100.

[0031] In a specific embodiment, the molten salt purification method comprises: melting crude hafnium tetrachloride in a low-melting-point molten salt, and heating the molten salt to volatilize the hafnium tetrachloride.

[0032] Among them, the low-melting-point molten salt is an alkali metal chloride, and impurities such as Si, Fe, Al, and Mg form stable complexes with high boiling points in the molten salt. When the molten salt is heated, hafnium tetrachloride volatilizes and the impurities remain in the molten salt, achieving the purpose of purification.

[0033] The molten salt purification process is to melt crude hafnium tetrachloride in a low-melting-point molten salt of alkali metal chloride. Impurities such as Si, Fe, Al, and Mg form a stable complex with a high boiling point in the molten salt. When the molten salt is heated, the hafnium tetrachloride volatilizes and the impurities remain in the molten salt, achieving the purification and refinement of high-purity hafnium tetrachloride (Hf: 99.99%).

[0034] In a specific embodiment, the hydrogenation purification method is: hydrogen is introduced into the crude hafnium tetrachloride, and the metal oxide impurities are separated by reducing them with hydrogen.

[0035] Among them, the principle of hydrogenation purification is:

[0036] (1) Using the different vapor pressure differences between HfCl4, TiCl4 and SiCl4 at the same temperature, a specific temperature is controlled to allow TiCl4, SiCl4 and H2O to sublime first and be removed;

[0037] (2) Using the high boiling point of ferrous chloride or chromium chloride, hydrogen is used to reduce trivalent iron and chromium to divalent iron. At the sublimation temperature of HfCl4, FeCl2 and CrCl2 do not sublime and remain in the residue, separating from hafnium.

[0038] Brief description of the process:

[0039] Hydrogen reduction purification mainly includes low-temperature impurity removal, hydrogen reduction, and high-temperature impurity removal processes to purify and remove impurities from crude hafnium tetrachloride. Among them, low-temperature impurity removal, hydrogen reduction, and high-temperature impurity removal are all carried out in a resistance furnace.

[0040] Low-temperature impurity removal: First, the crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and fed into the resistance furnace in layers through the screw feeder. Then, while vacuuming, it is electrically heated to 150-230°C. Low-melting and boiling point impurities, chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.), sublime into gases and are discharged through pipes into a jacketed circulating water condenser to cool below 80°C. High-boiling point chlorides (HfCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace for further purification. The condensed residue is returned to the chlorination furnace for recycling, and the non-condensable gas is discharged after washing in a leaching tower.

[0041] Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain a temperature of 150-230°C. After low-temperature impurities are removed, hydrogen is introduced through a pipeline to 0.2-0.5 MPa. The reaction is maintained for a certain reaction time (40-60 minutes) before the gas is released. This cycle is repeated 3-5 times. Metal chloride impurities with melting and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with the hydrogen, generating high-melting and high-boiling-point submetallic chlorides. The reaction formula is: 2FeCl3 + H2 → 2FeCl2 + 2HCl. The exhaust gas enters a condensation tower for cooling, and the condensed residue is returned to the chlorination furnace for recycling. The non-condensable gas is then discharged after washing in a leaching tower.

[0042] High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The resistance furnace is heated to 350-500°C. The hafnium tetrachloride, with its low melting and boiling points, sublimates into a gas, while the high-melting and boiling point metal chloride impurities remain in the slag. The slag is collected and returned to the chlorination furnace for recycling.

[0043] Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process enters the jacketed circulating water condensation equipment through a pipeline for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride is solid (the non-condensable gas is connected to the leaching tower and discharged after washing). It is then transported to the crusher for crushing. After crushing, it enters the next process to pass the high-purity hafnium tetrachloride into the sublimation furnace, and oxygen and AlCl3 gas-phase catalyst are introduced into the sublimation furnace to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine.

[0044] Because FeCl3 has similar boiling points to HfCl4 and ZrCl4, hydrogenation reduction is also required for its removal. During the hydrogenation reduction process, hafnium tetrachloride does not react with hydrogen. Instead, FeCl3 and hydrogen undergo an oxidation-reduction reaction to produce FeCl2 and HCl. FeCl2 has a boiling point above 700°C and settles as a solid in the residue at the bottom of the purification furnace, resulting in refined, high-purity hafnium tetrachloride (Hf: 99.999%).

[0045] In a specific embodiment, after the high-purity hafnium tetrachloride is introduced into the sublimation furnace, the reaction temperature is controlled at 800° C. to 1000° C.

[0046] In a specific embodiment, the amount of oxygen introduced into each kg of the hafnium tetrachloride is 80 L to 90 L.

[0047] The amount of oxygen used is in excess. At high temperature, high-purity hafnium tetrachloride vapor and excess oxygen are reacted with AlCl3 gas-phase catalyst to generate ultra-high-purity hafnium oxide particles and chlorine gas (Cl2 gas is recovered for the HfCl4 chlorination process, achieving a closed-loop cycle and reducing raw material costs).

[0048] In a specific embodiment, the mass of the added AlCl3 gas phase catalyst is 0.5% to 3% of the mass of hafnium tetrachloride.

[0049] In a second aspect, the present invention provides an electronic grade hafnium oxide prepared by the above preparation method.

[0050] In a specific embodiment, the method is used to prepare high-K dielectric constant materials, semiconductor devices, memories, or optical coatings.

[0051] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0052] (1) The preparation method of the present invention realizes the preparation of hafnium tetrachloride to ultra-high-purity electronic-grade hafnium oxide, and has high yield, simple process flow, high production efficiency and low production cost.

[0053] (2) The purity of the ultra-high-purity electronic-grade hafnium oxide prepared in the present invention can meet the material requirements for electronic chips, and the production equipment is simple and the yield is high.

[0054] (3) The AlCl3 gas-phase catalyst added in the present invention can form an unstable complex with hafnium tetrachloride at high temperature, reducing the strength of the Hf-Cl bond, thereby reducing the subsequent activation energy with O2. This complex is more likely to react with oxygen, promoting the breakage of Hf-Cl and the formation of Hf-O bonds, thereby shortening the reaction time and improving production efficiency.

[0055] (4) The AlCl3 gas phase catalyst added in the present invention releases chloride ions during the reaction to generate stable AlCl4 - Complex ions, reducing Cl - concentration, pushing the reaction towards the direction of generating HfO2, reducing the probability of reverse reaction, indirectly reducing the activation energy, and also shortening the reaction time and improving the generation efficiency.

[0056] (5) The AlCl3 gas-phase catalyst added in the present invention decomposes into Al2O3 nanoparticles at high temperature as a dispersant, providing nucleation sites for HfO2 and reducing the nucleation activation energy; it prevents particle agglomeration during high-temperature calcination, ensuring that the particle size of the product HfO2 is uniform.

[0057] (6) The AlCl3 gas phase catalyst added in the present invention can also interact with oxygen to generate active oxygen species (such as O - or O2 - ), enhancing the electrophilicity of oxygen, so that it strengthens the Hf center in the reaction HfCl4, reduces the activation energy of O2 participating in the reaction, and thus accelerates the oxidation process of HfCl4.

[0058] (7) In the high-temperature gas-phase reaction, the presence of AlCl3 in the gas-phase catalyst of the present invention guides the oxidation of HfCl4 through a lower activation energy path, passing through the intermediate Al-O-Hf structure, and finally decomposing into HfO2 and regenerating AlCl3, thus realizing a catalytic cycle.

[0059] (8) The AlCl3 gas-phase catalyst added in the present invention can significantly reduce the reaction temperature (e.g., from 1200°C to 800°C to 1000°C), thereby increasing the reaction rate and thus improving the photocatalytic performance or stability of the product. In addition, the recycling of AlCl3 reduces production costs, which is in line with the principle of green environmental protection.

[0060] (9) The AlCl3 gas-phase catalyst added in the present invention reduces the activation energy from both thermodynamic and kinetic perspectives by stabilizing the transition state, providing a low-energy path, and removing inhibitory by-products. Its essence is to reconstruct the reaction mechanism rather than directly participating in the final product. DETAILED DESCRIPTION

[0061] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0062] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily employed to practice the present invention. In other embodiments, well-known materials or methods are not specifically described to avoid obscuring the present invention.

[0063] Throughout this specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Therefore, appearances of the phrases "one embodiment," "an embodiment," "an example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combinations and / or subcombinations. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, one skilled in the art will be able to combine and combine different embodiments or examples, and features of different embodiments or examples, described in this specification, without mutual inconsistency.

[0064] The "ranges" disclosed herein are defined in the form of lower limits and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if the minimum range values listed are 1 and 2, and if the maximum range values listed are 3, 4, and 5, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0065] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0066] Example 1

[0067] This embodiment provides a method for preparing electronic grade hafnium oxide, which is carried out according to the following steps:

[0068] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0069] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0070] S3. The crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and added to a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, the hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0071] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0072] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0073] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0074] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0075] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0076] Example 2

[0077] This embodiment provides a method for preparing electronic-grade hafnium oxide. The difference from Example 1 is that the crude hafnium oxide and graphite powder in this embodiment are both crushed to 300 mesh. Other process parameters are the same as those in Example 1. The process is carried out according to the following steps:

[0078] S1. 1 kg of 300-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a material to be chlorinated.

[0079] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0080] S3. The crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and added to a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, the hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0081] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0082] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0083] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0084] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0085] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0086] Example 3

[0087] This embodiment provides a method for preparing electronic-grade hafnium oxide. The difference from Example 1 is that the crude hafnium oxide and graphite powder in this embodiment are both crushed to 500 mesh. Other process parameters are the same as those in Example 1. The method is carried out according to the following steps:

[0088] S1. 1 kg of 500-mesh crude hafnium oxide (99.6%) was mixed with 500-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a material to be chlorinated.

[0089] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0090] S3. The crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and added to a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, the tetrachloride turns into gas and is transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0091] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0092] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0093] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0094] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0095] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0096] Example 4

[0097] This embodiment provides a method for preparing electronic-grade hafnium oxide. Unlike Example 1, the molar ratio of crude hafnium oxide to graphite powder in this embodiment is 15:100. Other process parameters are the same as those in Example 1. The method is carried out according to the following steps:

[0098] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 15:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare the material to be chlorinated.

[0099] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0100] S3. The crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and added to a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, the hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0101] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0102] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0103] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0104] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0105] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0106] Example 5

[0107] This embodiment provides a method for preparing electronic-grade hafnium oxide. Unlike Example 1, the molar ratio of crude hafnium oxide to graphite powder in this embodiment is 20:100. Other process parameters are the same as those in Example 1. The method is carried out according to the following steps:

[0108] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 20:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare the material to be chlorinated.

[0109] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0110] S3. The crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and added to a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, the hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0111] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0112] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0113] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0114] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0115] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0116] Example 6

[0117] This embodiment provides a method for preparing electronic grade hafnium oxide. The difference from Example 1 is that the reaction temperature in step S7 of this embodiment is controlled at 800°C, and the other process parameters are the same as those of Example 1. The following steps are performed:

[0118] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0119] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0120] S3. The crude hafnium tetrachloride receiving tank is connected to a closed screw feeder and added to a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, the hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0121] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0122] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0123] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0124] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0125] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0126] Example 7

[0127] This embodiment provides a method for preparing electronic grade hafnium oxide. The difference from Example 1 is that the reaction temperature in step S7 of this embodiment is controlled at 1000° C., and the other process parameters are the same as those of Example 1. The following steps are performed:

[0128] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0129] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0130] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0131] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0132] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0133] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0134] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 1000° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0135] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0136] Example 8

[0137] This embodiment provides a method for preparing electronic grade hafnium oxide. The difference from Example 1 is that the amount of oxygen introduced in this embodiment is 80 L, and the other process parameters are the same as those in Example 1. The following steps are performed:

[0138] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0139] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0140] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0141] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0142] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0143] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0144] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 80 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0145] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0146] Example 9

[0147] This embodiment provides a method for preparing electronic grade hafnium oxide. The difference from Example 1 is that the amount of oxygen introduced in this embodiment is 90 L, and the other process parameters are the same as those in Example 1. The following steps are performed:

[0148] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0149] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0150] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0151] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0152] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0153] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0154] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 90 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled at 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0155] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0156] Example 10

[0157] This embodiment provides a method for preparing electronic-grade hafnium oxide. Unlike Example 1, the mass of the AlCl3 gas-phase catalyst added in this embodiment is 5 g. Other process parameters are the same as those in Example 1. The process is carried out according to the following steps:

[0158] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0159] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0160] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0161] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0162] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0163] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0164] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 5 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0165] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0166] Example 11

[0167] This embodiment provides a method for preparing electronic-grade hafnium oxide. Unlike Example 1, the mass of the AlCl3 gas-phase catalyst added in this embodiment is 30 g. Other process parameters are the same as those in Example 1. The process is carried out according to the following steps:

[0168] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0169] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0170] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0171] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0172] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0173] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0174] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 30 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0175] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce high-purity refined electronic grade hafnium oxide.

[0176] Comparative Example 1

[0177] This comparative example provides a method for preparing hafnium oxide. Unlike Example 1, no AlCl3 gas phase catalyst is added in step S7 of this comparative example. The steps are as follows:

[0178] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 17:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare a chlorinated material.

[0179] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0180] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0181] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0182] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0183] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0184] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen is introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0185] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce hafnium oxide.

[0186] Comparative Example 2

[0187] This comparative example provides a method for preparing hafnium oxide. The difference from Example 1 is that the amount of AlCl3 gas-phase catalyst added in step S7 of this comparative example is 3 g, and the other process parameters are the same as those of Example 1. The following steps are performed:

[0188] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 15-20:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare the material to be chlorinated.

[0189] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0190] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0191] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0192] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0193] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0194] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 3 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled at 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0195] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce hafnium oxide.

[0196] Comparative Example 3

[0197] This comparative example provides a method for preparing hafnium oxide. The difference from Example 1 is that the amount of AlCl3 gas-phase catalyst added in step S5 of this comparative example is 35g, and the other process parameters are the same as those of Example 1. The following steps are performed:

[0198] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 15-20:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare the material to be chlorinated.

[0199] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0200] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0201] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0202] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0203] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0204] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 85 L of oxygen and 35 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0205] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce hafnium oxide.

[0206] Comparative Example 4

[0207] This comparative example provides a method for preparing hafnium oxide. The difference from Example 1 is that the amount of oxygen added in step S7 of this comparative example is 70 L, and the other process parameters are the same as those of Example 1. The following steps are performed:

[0208] S1. 1 kg of 400-mesh crude hafnium oxide (99.6%) was mixed with 300-mesh graphite powder in a ratio of about 15-20:100 in a closed mixer; and the mixture was kept at a constant temperature of 120° C.-150° C. to prepare the material to be chlorinated.

[0209] S2. The material to be chlorinated is transported to the chlorination furnace through a closed screw feeder. At the same time, excess Cl2 is introduced into the bottom of the furnace. The chlorination furnace is heated electrically (the temperature in the furnace is controlled at 850°C to 900°C, and the pressure is slightly positive). The mixed material reacts with Cl2 at high temperature to undergo chlorination reaction and condensation to obtain crude HfCl4 (99.8%), which is then sealed to obtain the material to be purified by molten salt (the sealed tank is filled with argon for protection).

[0210] S3. The crude tetrachloride receiving tank is connected to a closed screw feeder and fed into a mixed molten salt furnace (NaCl-KCl molten salt purification system, wherein the addition ratio is approximately 70% NaCl and 30% KCl) through the screw feeder. The temperature in the molten salt equipment is maintained at (350-500°C). At this temperature, hafnium tetrachloride is converted into gas and transported from the upper part of the molten salt equipment through a pipeline to a condensing equipment for condensation to approximately 150°C. The cooled refined hafnium tetrachloride (99.9%) enters a closed crushing equipment for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0211] S4. The refined hafnium tetrachloride obtained by purifying the molten salt is connected to the receiving tank by a closed feeder and added into the resistance furnace in layers. Then, it is electrically heated to 150-230°C while being vacuumed. The low-melting and boiling point impurity chlorides (TiCl4, SiCl4, AlCl3, H2O, etc.) are sublimated into gases and discharged into a jacketed circulating water condensation device through a pipeline to be cooled below 80°C. The high-boiling point chlorides (HfCl4 and trace amounts of ZrCl4, FeCl3, CrCl3, etc.) are retained in the resistance furnace and await further purification.

[0212] S5. Hydrogen reduction: The resistance furnace is evacuated and electrically heated to maintain 150-230°C. After low-temperature impurity removal, hydrogen is introduced through a pipeline to 0.2-0.5MPa. The reaction is maintained for a certain time (40-60 minutes) and then released. The filling and releasing are repeated 3-5 times. Metal chloride impurities with melting points and boiling points close to those of hafnium tetrachloride undergo a reduction reaction with hydrogen to generate submetallic chlorides with high melting points and high boiling points. Condensation and crushing: The high-temperature gas generated during the high-temperature impurity removal process is passed through a pipeline into a jacketed circulating water condensing device for cooling. After cooling, the temperature drops to 150°C. The condensed hafnium tetrachloride (99.99%) is solid and then transported to a closed crusher for crushing to obtain the material to be purified by hydrogen reduction (the closed tank is filled with argon for protection).

[0213] S6. High-temperature impurity removal: Hafnium tetrachloride is separated from other substances such as ferrous chloride, zinc chloride, magnesium chloride, manganese chloride, and calcium chloride by utilizing their different melting and boiling points. The hydrogen reduction purification material is heated in a resistance furnace to 350-500°C. The low-melting and boiling-point hafnium tetrachloride sublimates into a gas, while the high-melting and boiling-point metal chloride impurities remain in the slag. The condensed hafnium tetrachloride (99.999%) is then conveyed to a sealed crusher for crushing to produce the purified hafnium oxide particles (the sealed tank is filled with argon for protection).

[0214] S7. The obtained high-purity hafnium tetrachloride is introduced into a sublimation furnace, and 70 L of oxygen and 10 g of AlCl3 gas-phase catalyst are introduced into the sublimation furnace. The reaction temperature is controlled to be 900° C. to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas.

[0215] S8. The hafnium oxide particles are dechlorinated in a fluidized bed high-temperature reactor to produce hafnium oxide.

[0216] The purity and yield of hafnium oxide prepared by the preparation methods of Examples 1 to 11 and Comparative Examples 1 to 4 were tested, and the test results are shown in Table 1.

[0217] Table 1

[0218] sample <![CDATA[HfO2 purity (%)]]> Yield (%) Example 1 99.9992 88.1 Example 2 99.9995 90.2 Example 3 99.9994 90.1 Example 4 99.9993 89.8 Example 5 99.9998 91.5 Example 6 99.9997 90.9 Example 7 99.9998 90.9 Example 8 99.9999 91.3 Example 9 99.9996 90.2 Example 10 99.9999 91.6 Example 11 99.9998 90.9 Comparative Example 1 99.9912 87.1 Comparative Example 2 99.9809 86.3 Comparative Example 3 99.9262 84.5 Comparative Example 4 99.9371 85.1

[0219] It can be seen from the above test results that the hafnium oxide prepared by the method of the present invention not only has electronic grade ultra-high purity, but also has high yield, stable and controllable quality, simple process flow, high production efficiency, low production cost, economy and environmental protection. At the same time, the test results of Examples 1 to 11 are compared with the test results of Comparative Example 1, and it can be seen that when AlCl3 gas-phase catalyst is not added in Comparative Example 1, the purity of the hafnium oxide prepared is lower than that of Examples 1 to 11. At the same time, the test results of Examples 1 to 11 are compared with Comparative Examples 2 and 3, and it can be seen that the purity of the hafnium oxide prepared by Comparative Examples 2 and 3 is lower than that of Examples 1 to 11, which proves that the purity of the hafnium oxide prepared can reach electronic grade ultra-high purity only when the amount of AlCl3 gas-phase catalyst is added within the range defined by the present invention. Comparing the test results of Examples 1 to 11 with those of Comparative Example 4, it can be seen that the purity of hafnium oxide prepared in Comparative Example 4 is lower than that of Examples 1 to 11, which proves that the purity of the prepared hafnium oxide can reach electronic grade ultra-high purity only when the amount of oxygen introduced is added within the range specified in the present application. When the amount of oxygen introduced is too low, the purity and yield of the prepared HfO2 are lower than those of Examples 1 to 11.

[0220] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that it is still possible to modify the technical solutions described in the above embodiments, or to replace some or all of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for preparing electronic grade hafnium oxide, characterized in that: The following steps are involved: The crushed crude hafnium oxide is subjected to a chlorination reaction with graphite powder to obtain crude hafnium tetrachloride; Purifying crude hafnium tetrachloride in turn by a molten salt purification method and a hydrogenation purification method to obtain high-purity hafnium tetrachloride; Passing high-purity hafnium tetrachloride into a sublimation furnace, and passing oxygen and AlCl3 gas-phase catalyst into the sublimation furnace to oxidize the high-purity hafnium tetrachloride into hafnium oxide particles and chlorine gas; The hafnium oxide particles are dechlorinated in a fluidized bed to produce electronic grade hafnium oxide.

2. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: The crude hafnium oxide and graphite powder are crushed to 300-500 mesh.

3. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: The mass ratio of the crude hafnium oxide to the graphite powder is (15-20):

100.

4. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: The molten salt purification method comprises the following steps: melting crude hafnium tetrachloride in a low-melting-point molten salt, and heating the molten salt to volatilize the hafnium tetrachloride.

5. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: The hydrogenation purification method comprises the following steps: introducing hydrogen into crude hafnium tetrachloride, and reducing metal oxide impurities by hydrogen to separate them.

6. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: After the high-purity hafnium tetrachloride is introduced into the sublimation furnace, the reaction temperature is controlled at 800° C. to 1000° C.

7. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: The amount of oxygen introduced into each kg of the hafnium tetrachloride is 80 L to 90 L.

8. The method for preparing electronic grade hafnium oxide according to claim 1, wherein: The mass of the added AlCl3 gas phase catalyst is 0.5% to 3% of the mass of hafnium tetrachloride.

9. An electronic grade hafnium oxide, characterized in that: The preparation method is described in any one of claims 1 to 8.

10. The electronic grade hafnium oxide according to claim 9, characterized in that Including those used for preparing high-K dielectric constant materials, semiconductor devices, memories or optical coatings.