Ultrafast synthesis method of rare earth oxychloride

Abstract

The invention provides an ultrafast synthesis method of rare earth oxychloride. The ultrafast synthesis method comprises the following steps: step 1, preparing a powder precursor; and 2, putting the powder precursor into a graphite tube, and carrying out heat treatment by adopting a rapid Joule heating technology to obtain the rare earth oxychloride material. The method is simple in process, energy consumption is reduced by 90% or above compared with traditional roasting, no organic solvent is needed, and the product is high in crystallinity and controllable in morphology.

Description

Technical Field

[0001] This invention relates to an ultrafast synthesis method for rare earth oxychlorides, belonging to the field of inorganic material synthesis and high-temperature heat treatment technology. Background Technology

[0002] Currently, rare earth oxychlorides are widely used in high-tech fields such as optics, electronic devices, and catalyst supports due to their excellent thermal stability, electrical insulation, and ability to modulate the luminescence properties of rare earth ions. Traditional calcination methods require >10 hours and consume >5000 kJ / mol of energy, resulting in products with low crystallinity and XRD peak widths >0.5°. Rare earth chlorides (especially hydrated chlorides) are highly volatile or thermally decomposed during ultra-high temperature heating, leading to the formation of secondary phases (RE2O2Cl / RE2O3). Rare earth oxides and chlorides are mostly insulators or semiconductors with extremely high initial resistance, resulting in difficulties in heating start-up or low energy coupling efficiency. Traditional high-temperature solid-state reactions are usually carried out in tube furnaces or muffle furnaces, which are batch processes, making continuous and large-scale production difficult. They also suffer from high energy consumption, long processing times, and incomplete crystallization. Wet chemical methods such as the sol-gel method can be used for preparation on a certain scale, but their subsequent processing is cumbersome and involves wastewater discharge. Therefore, there is an urgent need for a Joule heating technology that can overcome the above difficulties and achieve efficient, energy-saving, and controllable synthesis of rare earth oxychlorides.

[0003] Rapid Joule heating, a powerful and scalable synthetic technique for the rapid thermal processing of advanced nanomaterials, enables ultrafast heating and cooling rates within milliseconds by providing instantaneous, high-intensity electrical pulses. This instantaneous high temperature suppresses excessive grain growth, yielding submicron-scale layered structures (Faizan et al. Mater Res.Bull. 2025, 192, 113639. Qin et al. J Mater Chem A. 2025,13, ​​12828-12854. Liu et al. Angew Chem Int Edit. 2025, 64, e202414021.). This ultrathin layered structure significantly promotes rapid carrier separation and transport, demonstrating great potential in high-performance photodetectors and ultraviolet shielding materials. Simultaneously, this unique morphology significantly increases the specific surface area of ​​the material, providing an ideal carrier for loading noble metal nanoparticles, thus expanding its application prospects in catalysis. Building upon this foundation, by further optimizing the Joule heating device into a continuous production system, the technology can be scaled up for mass production, successfully overcoming the industrial bottleneck of large-scale, continuous synthesis of rare earth oxychlorides. This technology offers unprecedented control over materials synthesis and has been successfully applied to a range of materials with functionally driven properties.

[0004] Technical obstacles currently hindering the application of the Joule heating method to the synthesis of rare earth oxychlorides include: Rare earth chlorides are volatile / decompose easily: at high temperatures, especially hydrated chlorides, they are extremely volatile or thermally decomposed, leading to the formation of secondary phases (such as RE2O2Cl, RE2O3) and a decrease in crystallinity.

[0005] High reactant resistance: Most rare earth oxides and chlorides are insulators or semiconductors with high initial resistance, which is not conducive to the smooth initiation of the Joule heating effect. Summary of the Invention

[0006] This invention provides an ultrafast synthesis method for rare earth oxychlorides, which can effectively solve the above-mentioned problems.

[0007] This invention provides an ultrafast synthesis method for rare earth oxychlorides, comprising the following steps: Step 1: Preparation of powder precursor; Step 2: The powder precursor is placed in a graphite tube and heat-treated in a protective atmosphere using rapid Joule heating technology to obtain rare earth oxychloride material. Step one includes: applying rare earth oxides (RE) x O y Rare earth chlorides and metal salts are mixed and ground into powder; or rare earth oxides (RE) are mixed and ground into powder. x O y It is mixed with concentrated hydrochloric acid and then dried to form a solid powder.

[0008] In some embodiments, the rare earth oxides (RE) x O y The molar ratio of rare earth chloride to rare earth chloride is 1:1 to 1:40.

[0009] In some embodiments, the rare earth chloride is anhydrous rare earth metal chloride (RECl3) or hydrated rare earth chloride (RECl3·2H2O).

[0010] In some embodiments, the metal salt is selected from one or more of NaCl, KCl, LiCl, and NH4Cl.

[0011] In some embodiments, the rare earth oxides (RE) x O y The molar ratio of 1:10 to 1:20 with concentrated hydrochloric acid is 1:10 to 1:20.

[0012] In some embodiments, the rapid Joule heating technology in step two has a heating time of 1s–1200s and a temperature controlled at 500–3000℃.

[0013] In some embodiments, the protective atmosphere is selected from argon, nitrogen, hydrogen, a hydrogen-argon mixture, a hydrogen-nitrogen mixture, and air.

[0014] In some embodiments, the rare earth element RE in the rare earth oxides and rare earth chlorides is selected from one or more of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0015] In some embodiments, the initial resistance of the device for the rapid Joule heating technology in step two is 1 to 9 Ω.

[0016] A rare earth oxychloride material is prepared by the above method. The material is crystalline, has a layered morphology, and its XRD full width at half maximum is less than 0.3°.

[0017] The beneficial effects of this invention are: 1. This invention employs rapid Joule heating technology, applying a transient pulsed current to achieve Joule thermal shock, instantly raising the precursor to ultra-high temperatures (>3000 K), followed by extremely rapid cooling (>10 K). 4 The process can complete the reaction in seconds to tens of seconds, greatly shortening the preparation time. The total synthesis time is reduced to 1–1200 s, which is a significant improvement in efficiency compared to the traditional calcination method (>10 hours).

[0018] 2. This invention employs rapid Joule heating technology, whose extremely high heating and cooling rates effectively suppress sintering and agglomeration of materials, promoting atomic-level dispersion, thereby achieving precise control over the microstructure, composition, and structure of the materials. Compared to the drawbacks of traditional methods, such as long heating times and high energy consumption, this strategy effectively overcomes the disadvantages of time-consuming, energy-intensive, and multi-step operations. Compared to traditional calcination, this invention significantly reduces energy consumption, and the preparation process does not require the use of organic solvents, template agents, or other toxic reagents. The method is rapid, simple, environmentally friendly, and safe.

[0019] 3. This invention can overcome the technical obstacles that hinder the application of the Joule heating method: In response to the problem of high reactant resistance, this invention brings a graphite tube with good conductivity into close contact with the precursor powder, so that the initial resistance of the device is low (about 1 to 9 Ω), ensuring the smooth start-up of the Joule heating effect.

[0020] 4. To address the issue of volatility in rare earth chlorides, this invention introduces 0.1–10 wt% of a metal salt (such as NaCl, KCl, etc.) into the system. This metal salt melts at high temperatures to form a liquid phase coating, effectively suppressing the vigorous volatilization of RECl3. This significantly reduces the amount of RECl3 used and the net volatilization, making the system more stable, reducing the formation of secondary phases, and improving the crystallinity of the product. Furthermore, traditional solid-phase methods for preparing rare earth oxychlorides typically require a long calcination process, during which a large amount of RECl3 volatilizes. This invention employs ultra-fast Joule heating technology, which significantly reduces the volatilization of RECl3 during the reaction, thereby lowering the required amount of RECl3.

[0021] 5. This invention employs different volatilization suppression strategies for two different types of chlorine-containing precursors: For the system using rare earth oxides + added rare earth chlorides, the added RECl3 is easily volatilized at rapid high temperatures. Therefore, it is preferable to add 0.1–10 wt% of NaCl, KCl, LiCl, or NH4Cl to form a locally molten / coated phase at the instantaneous high temperature of FJH, thereby reducing volatilization and increasing crystallinity. This effect can be demonstrated by Comparative Example 3. For the precursor powder prepared by reacting rare earth oxides with concentrated hydrochloric acid at a ratio of approximately 1:10–1:20 and then drying, a uniformly distributed chlorine-containing layer is generated in situ on the particle surface. In the initial stage of FJH heating, a temporary high chlorine partial pressure environment can be formed, which plays a role in gas phase replenishment and volatilization suppression. At the same time, the chloride content and temperature window of this route are relatively mild. Therefore, well-crystallized rare earth oxychlorides can be obtained under FJH conditions of approximately 1500 °C and approximately 200 s without the need for additional metal salts.

[0022] 6. The rare earth oxychloride product obtained by this invention has high crystallinity. At the same time, the extremely high heating and cooling rates effectively suppress grain agglomeration and sintering, resulting in a layered structure with controllable morphology.

[0023] 7. This invention employs a solid-phase mixing method, with the mixing ratio of rare earth oxides and chlorides ranging from 1:1 to 1:40. This wide range of mixing ratios allows for a broad selection of raw materials for rare earth oxychlorides, which are inexpensive, non-toxic, and harmless. Suitable raw materials include anhydrous rare earth metal chlorides (RECl3), hydrated rare earth chlorides (RECl3·2H2O), and rare earth oxides (RE...). x O y The parameters, such as , can be adjusted according to the actual situation, making the preparation method flexible.

[0024] 8. The rapid Joule heating technology employed in this invention allows for easy integration of the equipment with continuous production systems. Furthermore, by designing a roll-to-roll electrode system, the precursor powder can be pre-pressed into strips or loaded onto a flexible graphite felt conveyor belt, allowing it to continuously pass between electrode rollers and undergo instantaneous high-temperature treatment. This enables low-cost, high-efficiency, large-scale continuous production of rare earth oxychloride materials, which is impossible with traditional batch-processing calcining furnaces. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 The X-ray diffraction (XRD) patterns of the rare earth oxychlorides prepared in Examples 1, 4, 10, and 13 are shown. Figure 1 Labels: (a) SmOCl, (b) TbOCl, (c) LaOCl, (d) NdOCl.

[0027] Figure 2 The images show scanning electron microscope (SEM) images of SmOCl, TbOCl, LaOCl, and NdOCl prepared in Examples 1, 4, 10, 13, and 16. Figure 2 Labels: (a,b) SmOCl layered structure; (c,d) TbOCl layered structure; (e,f) LaOCl layered structure; (g,h) NdOCl layered structure; (i,g) NdOCl layered structure.

[0028] Figure 3 The LaOCl prepared in Example 10 and the conventional high-temperature heating synthesis obtained in Comparative Example 1 were used. X-ray diffraction (XRD) pattern of LaOCl. Figure 3 Notes: (a) FJH-LaOCl, (b) C-LaOCl.

[0029] Figure 4 The NdOCl prepared in Example 16, Figure 4 Note: NdOCl-2.

[0030] Figure 5 The image shows a scanning electron microscope (SEM) image of SmOCl synthesized by the conventional high-temperature solid-state method in Comparative Example 2, and an X-ray diffraction (XRD) image of PrOCl prepared by rapid Joule heating without the addition of metal salts in Comparative Example 3. Figure 5 Notes: (a) SmOCl particle aggregation structure, (b) Pr6O 11 +PrOCl.

[0031] Figure 6 This is a schematic diagram of the ultrafast synthesis method of rare earth oxychlorides in the example. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0033] The rapid Joule heating reactor used in this embodiment of the invention is the Saiyin FJH-2024B Joule heating reactor, which consists of a power control cabinet, a vacuum reaction chamber, and a data acquisition system. The FJH-2024B Joule heating reactor integrates an infrared thermometer and an Altai USB3100N data acquisition card, enabling millisecond-level acquisition, recording, and monitoring of voltage, current, and temperature data.

[0034] Example 1: Rapid Joule heating for the preparation of SmOCl 1. Mix Sm2O3 and SmCl3 in a 1:1 molar ratio, add 1 wt% KCl, and grind them evenly using an agate mortar.

[0035] 2. Place the precursor powder obtained in step 1 into a graphite tube, add graphite plugs at both ends, and then place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0036] 3. Evacuate the vacuum reaction chamber where the precursor was placed in step 2, and then introduce inert gas N2. Repeat this process three times.

[0037] 4. Before applying the pulse heating current, the system automatically injects a weak low-current test signal into the circuit to accurately measure the initial resistance of the circuit formed by the graphite tube and its internal precursor powder. The initial resistance of the device is 8.2Ω. The heating program is set, the heating time is 1s, and the temperature is raised to 500℃.

[0038] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth samarium oxychloride.

[0039] Figure 1 a is the XRD pattern of SmOCl. The XRD pattern, compared with the standard card, confirms that the obtained product is SmOCl. The SEM image (…) Figure 2 a, Figure 2 b) It can be seen that samarium oxychloride is a two-dimensional layered material. Example 2: Rapid Joule heating for the preparation of ErOCl 1. Mix Er2O3 and ErCl3 in a molar ratio of 1:1, add 1wt% KCl, and grind evenly with an agate mortar.

[0040] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0041] 3. Evacuate the vacuum reaction chamber where the precursor was placed in step 2, and introduce inert gas N2, repeating this process three times.

[0042] 4. The initial resistance of the device is 9.7Ω. The heating program is set to a heating time of 1 second, and the temperature is raised to 500℃.

[0043] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth erbium oxychloride.

[0044] Example 3: Rapid Joule heating for the preparation of LuOCl 1. Mix Lu2O3 and LuCl3·6H2O in a molar ratio of 1:1, add 2wt% NaCl, and grind evenly with an agate mortar.

[0045] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0046] 3. Evacuate the vacuum reaction chamber where the precursor was placed in step 2, and introduce inert gas N2, repeating this process three times.

[0047] 4. The initial resistance of the device is 8.6Ω. The heating program is set to a heating time of 1 second, and the temperature is raised to 500℃.

[0048] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth lutetium oxychloride.

[0049] Example 4: Rapid Joule heating for the preparation of TbOCl 1. Mix Tb4O7 and TbCl3 at a molar ratio of 1:10, add 5wt% LiCl, and grind evenly with an agate mortar.

[0050] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0051] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0052] 4. The initial resistance of the device is 5.1Ω. The heating program is set to a heating time of 60s, and the temperature is raised to 800℃.

[0053] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth terbium oxychloride.

[0054] Figure 1 b is the XRD pattern of TbOCl. The XRD pattern shows that, compared to the standard card, the obtained product is TbOCl. The SEM image (...) Figure 2 c. Figure 2 As can be seen from d), the terbium oxychloride is a two-dimensional layered material.

[0055] Example 5: Rapid Joule heating for the preparation of CeOCl 1. Mix CeO2 and CeCl3 in a molar ratio of 1:10, add 10wt% NaCl, and grind evenly with an agate mortar.

[0056] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0057] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0058] 4. The initial resistance of the device is 5.2Ω. The heating program is set to a heating time of 60s, and the temperature is raised to 800℃.

[0059] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth cerium oxychloride.

[0060] Example 6: Rapid Joule heating for the preparation of PrOCl 1. Pr6O 11 Mix with PrCl3 at a molar ratio of 1:10, add 7wt% LiCl, and grind evenly using an agate mortar.

[0061] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0062] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0063] 4. The initial resistance of the device is 4.8Ω. The heating program is set to a heating time of 60s, and the temperature is raised to 800℃.

[0064] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth praseodymium oxychloride.

[0065] Example 7: Rapid Joule heating for the preparation of DyOCl 1. Mix Dy2O3 and DyCl3 at a molar ratio of 1:10, add 9wt% NaCl, and grind evenly with an agate mortar.

[0066] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0067] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0068] 4. The initial resistance of the device is 5.3Ω. The heating program is set to a heating time of 60s, and the temperature is raised to 800℃.

[0069] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth dysprosium oxychloride.

[0070] Example 8: Rapid Joule heating for the preparation of ErOCl 1. Mix Er2O3 and ErCl3 at a molar ratio of 1:10, add 3wt% KCl, and grind evenly with an agate mortar.

[0071] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0072] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0073] 4. The initial resistance of the device is 5.0Ω. Set the heating program to 60s and heat up to 800℃.

[0074] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth erbium oxychloride.

[0075] Example 9: Rapid Joule heating for HoOCl preparation 1. Mix Ho2O3 and HoCl3·6H2O in a molar ratio of 1:1, add 7wt% LiCl, and grind evenly with an agate mortar.

[0076] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0077] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0078] 4. The initial resistance of the device is 9.8Ω. The heating program is set to a heating time of 60s, and the temperature is raised to 800℃.

[0079] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth holmium oxychloride.

[0080] Example 10: Rapid Joule heating for the preparation of LaOCl 1. Mix La2O3 and LaCl3·6H2O at a molar ratio of 1:20, add 4wt% NaCl, and grind evenly with an agate mortar.

[0081] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0082] 3. Evacuate the Joule heating device in step 2 where the precursor has been placed, and introduce a hydrogen-argon mixture.

[0083] 4. The initial resistance of the device is 2.1Ω. The heating program is set to a heating time of 600s, and the temperature is raised to 1500℃.

[0084] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth lanthanum oxychloride.

[0085] The measured voltage of the rapid Joule thermal discharge stage of LaOCl was approximately 15 V, the current was approximately 30 A, the discharge time was approximately 600 s, the average power was 450 W, and the total energy consumption was approximately 0.075 kWh, or approximately 6.75 kJ. Under the premise of obtaining well-crystallized rare earth oxychlorides, the energy consumption of a single synthesis in this invention is in the kJ range.

[0086] Figure 1 c is the XRD pattern of LaOCl. From Figure 1 As can be seen from image c, the diffraction peaks of the obtained product are clear and sharp, with high diffraction intensity and a narrow half-width, indicating high crystallinity and a complete and pure crystal phase structure. Comparison with the standard card confirms that the obtained product is LaOCl. From the SEM image (… Figure 2 As can be seen from e and 2f, this lanthanum oxychloride is a two-dimensional layered material. Example 11: Rapid Joule heating for the preparation of TmOCl 1. Mix Tm2O3 and TmCl3 at a molar ratio of 1:20, add 5wt% KCl, and grind evenly with an agate mortar.

[0087] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0088] 3. Evacuate the Joule heating device in step 2 where the precursor has been placed, and introduce a hydrogen-argon mixture.

[0089] 4. The initial resistance of the device is 2.3Ω. The heating program is set to a heating time of 600s, and the temperature is raised to 1500℃.

[0090] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth thulium oxychloride.

[0091] Example 12: Rapid Joule heating for the preparation of YbOCl 1. Mix Yb2O3 and YbCl3·6H2O at a molar ratio of 1:20, add 2wt% LiCl, and grind evenly with an agate mortar.

[0092] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0093] 3. Evacuate the Joule heating device in step 2 where the precursor has been placed, and introduce a hydrogen-argon mixture.

[0094] 4. The initial resistance of the device is 1.8Ω. The heating program is set to a heating time of 600s, and the temperature is raised to 1500℃.

[0095] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth ytterbium oxychloride.

[0096] Example 13: Rapid Joule heating for the preparation of NdOCl 1. Mix Nd2O3 and NdCl3 at a molar ratio of 1:40, add 1wt% KCl, and grind evenly with an agate mortar.

[0097] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0098] 3. Evacuate the Joule heating device in step 2 where the precursor has been placed, and introduce inert gas Ar, repeating this process several times.

[0099] 4. The initial resistance of the device is 1.2Ω. The heating program is set to a heating time of 1200s, and the temperature is raised to 3000℃.

[0100] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth neodymium oxychloride.

[0101] Figure 1 d represents the XRD pattern of NdOCl. The XRD pattern shows that, compared to the standard card, the obtained product is NdOCl. The SEM image (…) Figure 2 As can be seen from g and 2h, this neodymium oxychloride belongs to a two-dimensional layered material. Example 14: Rapid Joule heating for preparing ScOCl 1. Mix Sc2O3 and ScCl3 at a molar ratio of 1:40, add 10wt% NaCl, and grind evenly with an agate mortar.

[0102] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it in the vacuum reaction chamber of a rapid Joule thermal reactor.

[0103] 3. Evacuate the Joule heating device in step 2 where the precursor was placed, and introduce inert gas Ar, repeating this process three times.

[0104] 4. The initial resistance of the device is 1.1Ω. The heating program is set to a heating time of 1200s, and the temperature is raised to 3000℃.

[0105] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth scandium oxychloride.

[0106] Example 15: Rapid Joule heating for the preparation of YOCl 1. Mix Y2O3 and YCl3·6H2O at a molar ratio of 1:40, add 10wt% NaCl, and grind evenly with an agate mortar.

[0107] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0108] 3. Evacuate the Joule heating device in step 2 where the precursor was placed, and introduce inert gas Ar, repeating this process three times.

[0109] 4. The initial resistance of the device is 1.1Ω. The heating program is set to a heating time of 1200s, and the temperature is raised to 3000℃.

[0110] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth yttrium oxychloride.

[0111] Example 16: Rapid Joule heating for the preparation of NdOCl 1. Mix Nd2O3 and concentrated HCl in a beaker at a molar ratio of 1:10 and dry.

[0112] 2. Place the dried powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0113] 3. Evacuate the Joule heating device in step 2 where the precursor was placed, and introduce inert gas Ar, repeating this process three times.

[0114] 4. The initial resistance of the device is 6.8Ω. The Joule heating program is set, the heating time is 200s, and the temperature rises to 1500℃.

[0115] 5. After the quartz tube in step 3 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth neodymium oxychloride.

[0116] Figure 4 This is the XRD pattern of NdOCl-2. The XRD pattern shows that, compared to the standard card, the product obtained is NdOCl. The SEM image (...) Figure 2 As can be seen from i and 2j), this neodymium oxychloride is a two-dimensional layered material.

[0117] Example 17: Rapid Joule heating for the preparation of GdOCl 1. Mix Gd2O3 and concentrated HCl in a beaker at a molar ratio of 1:10 and dry.

[0118] 2. Place the dried powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0119] 3. Evacuate the Joule heating device in step 2 where the precursor was placed, and introduce inert gas Ar, repeating this process three times.

[0120] 4. The initial resistance of the device is 8.5Ω. The Joule heating program is set, the heating time is 200s, and the temperature rises to 1500℃.

[0121] 5. After the quartz tube in step 3 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth gadolinium oxychloride.

[0122] Example 18: Rapid Joule heating for the preparation of PmOCl 1. Mix Pm2O3 and HCl in a beaker at a molar ratio of 1:10 and dry.

[0123] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into the vacuum reaction chamber of the rapid Joule heating reactor.

[0124] 3. Evacuate the Joule heating device in step 2 where the precursor was placed, and introduce inert gas Ar, repeating this process three times.

[0125] 4. The initial resistance of the device is 9.0Ω. The Joule heating program is set, the heating time is 200s, and the temperature rises to 1500℃.

[0126] 5. After the quartz tube in step 3 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth promethium oxychloride.

[0127] Comparative Example 1: Synthesis of LaOCl by Traditional High-Temperature Heating Method 1. Weigh out the same amount of La2O3 and LaCl3·6H2O powder as in Example 10, add 4wt% NaCl, and grind evenly using an agate mortar.

[0128] 2. Transfer the well-mixed precursor powder into a ceramic boat, and then place it into a tube furnace.

[0129] 3. Introduce a hydrogen-argon mixture and heat to 900°C at a rate of 5°C / min, and heat at this temperature for 2 hours.

[0130] 4. After the reaction is complete, the furnace is cooled to room temperature. The sample is then removed, and the powder is transferred to a centrifuge tube for washing and drying to obtain rare earth lanthanum oxychloride.

[0131] Comparative Example 1 uses a tubular furnace with a rated power of 2.5 kW, heating to 900 ℃ at a rate of 5 ℃ / min, and holding at that temperature for 2 h. Its energy consumption is approximately 12.3 kWh, or about 4.4 × 10⁻⁶ kWh. 4 kJ. Compared with the kJ-level energy consumption of this invention, the energy consumption of traditional tube furnaces is increased by several orders of magnitude.

[0132] The obtained product was subjected to XRD testing. Figure 3 The results showed that the main phase was LaOCl, but the diffraction peak intensity was significantly reduced, the peak shape was broad and blunt, and the baseline noise was large.

[0133] The LaOCl sample prepared in Example 10 showed a significantly higher main peak intensity in X-ray diffraction analysis than that of Comparative Example 1, with a half-width at half-maximum (FWHM) generally less than 0.3°, and the diffraction peak intensity increased by more than 50%, exhibiting a sharper and more symmetrical shape. In contrast, the diffraction peak intensity and FWHM of the Comparative Example 1 sample were lower, indicating insufficient crystallinity.

[0134] Therefore, compared with the rapid Joule heating method of Example 10, the traditional high-temperature heating method of Comparative Example 1 shows significant batch-to-batch differences in products, often exhibiting secondary phases or fluctuations in crystallinity. The XRD diffraction peak positions of the rapid Joule heating method for preparing rare earth oxychlorides are fixed, and the test results between different batches of samples are highly consistent. Meanwhile, the traditional high-temperature method, due to its slow heating rate and excessively long reaction time, leads to reactant volatilization and extremely high energy consumption, making it impossible to achieve ultrafast, low-temperature, and low-energy synthesis.

[0135] Comparative Example 2: Synthesis of SmOCl by Traditional High-Temperature Heating Method 1. Mix Sm2O3 and SmCl3 in a molar ratio of 1:1, add 1wt% KCl, and grind evenly with an agate mortar.

[0136] 2. Transfer the well-mixed precursor powder into a ceramic boat, and then place it into a tube furnace.

[0137] 3. Introduce a hydrogen-argon mixture and heat to 500°C at a rate of 5°C / min, and heat at this temperature for 2 hours.

[0138] 4. After the reaction is complete, the furnace is cooled to room temperature. The sample is then removed, and the powder is transferred to a centrifuge tube for washing and drying to obtain rare earth samarium oxychloride.

[0139] Figure 5 Image a is a SEM image of SmOCl. As can be seen from the image, SmOCl particles prepared by the traditional high-temperature solid-state heating method exhibit severe agglomeration, irregular morphology, difficulty in forming lamellar layer structures, uneven particle size distribution, and sintering and blocky aggregation in some areas.

[0140] and Figure 2 Compared to a and 2b, SmOCl prepared by the rapid Joule heating method exhibits a regular two-dimensional layered and lamellar structure with uniform grain distribution, clear lamellar boundaries, and intact morphology. This indicates that the method can achieve rapid crystallization in a very short time and suppress grain agglomeration and excessive sintering.

[0141] Comparative Example 3: Rapid Joule heating preparation of PrOCl without the addition of metal salts 1. Weigh out an equimolar amount of Pr6O as in Example 6 11 Mix with PrCl3 and grind evenly using an agate mortar.

[0142] 2. Place the precursor powder from step 1 into a graphite tube, add graphite plugs to both ends, and place it into a rapid Joule heating device.

[0143] 3. Place the Joule heating device in which the precursor was placed in step 2 into an air atmosphere.

[0144] 4. Set the heating program: the initial resistance of the device is 15.6Ω, the heating time is 60s, and the temperature rises to 800℃.

[0145] 5. After the quartz tube in step 4 has cooled to room temperature, transfer the powder to a centrifuge tube for washing and drying to obtain rare earth praseodymium oxychloride.

[0146] The obtained product was subjected to XRD testing. Figure 5 The results showed that, in addition to the target phase PrOCl, there was also a significant secondary phase Pr6O. 11 Other impurities and peaks indicate that the product has an incomplete crystal structure.

[0147] Compared with Example 6 (with 7wt% LiCl added), the crystallinity of the product obtained in this comparative example was significantly reduced, the XRD half-width was increased, and the content of the secondary phase was high, proving that the metal salt melts at high temperature to form a liquid phase coating layer, which effectively inhibits the violent volatilization of RECl3 and improves the crystallinity of the product.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for the ultrafast synthesis of rare earth oxychlorides, characterized in that... Includes the following steps: Step 1: Preparation of powder precursor; Step 2: The powder precursor is placed in a graphite tube and heat-treated in a protective atmosphere using rapid Joule heating technology to obtain rare earth oxychloride material. Step one includes: applying rare earth oxides (RE) x O y Rare earth chlorides and metal salts are mixed and ground into powder; or rare earth oxides (RE) are mixed and ground into powder. x O y It is mixed with concentrated hydrochloric acid and then dried to form a solid powder.

2. The method according to claim 1, characterized in that, The rare earth oxides (RE) x O y The molar ratio of rare earth chloride to rare earth chloride is 1:1 to 1:

40.

3. The method according to claim 1, characterized in that, The metal salt is selected from one or more of NaCl, KCl, LiCl, and NH4Cl.

4. The method according to claim 1, characterized in that, The metal salt accounts for 0.1–10 wt%.

5. The method according to claim 1, characterized in that, The rare earth oxides (RE) x O y The molar ratio of 1:10 to 1:20 with concentrated hydrochloric acid is 1:10 to 1:

20.

6. The method according to claim 1, characterized in that, The rapid Joule heating technology in step two has a heating time of 1–1200s and a temperature control of 500–3000℃.

7. The method according to claim 1, characterized in that, The protective atmosphere is selected from argon, nitrogen, hydrogen, a mixture of hydrogen and argon, a mixture of hydrogen and nitrogen, and air.

8. The method according to claim 1, characterized in that, The rare earth element RE in the rare earth oxides and rare earth chlorides is selected from one or more of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

9. The method according to claim 1, characterized in that, The initial resistance of the device for the rapid Joule heating technology in step two is 1 to 9 Ω.

10. A rare earth oxychloride material, characterized in that, It is prepared by any one of claims 1 to 9, and the material is crystalline, has a layered morphology, and its XRD full width at half maximum is less than 0.3°.

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