A flux-based hexagonal R 1-x In x Method for growing FeO3(R=Lu, Yb, Tm, x=0-1) crystals

Abstract

This invention belongs to the field of crystal growth technology and relates to a flux-based hexagonal R 1‑x In x A method for growing FeO3 (R=Lu,Yb,Tm,x=0-1) crystals. This method involves introducing In... 3+ The orthorhombic RFeO3 (R = Lu, Yb, Tm) structure was successfully induced into a hexagonal InFeO3 structure. Furthermore, this method employed a KF-X2CO3 (X = Li, Na, K) composite flux system to achieve stable growth of RFeO3 at ambient pressure and relatively low temperatures. 1‑x In x FeO3 (R = Lu, Yb, Tm) crystals. Compared with the prior art, this invention overcomes the stringent requirements of high temperature and high pressure growth for hexagonal RFeO3 crystals. The grown crystals not only have controllable composition and can achieve continuous changes from orthorhombic to hexagonal structures, but also have crystal sizes on the order of centimeters and high crystal quality.

Description

Technical Field

[0001] This invention belongs to the field of crystal growth technology, and in particular relates to a flux-based hexagonal R... 1-x In x Growth method of FeO3 (R=Lu,Yb,Tm,x=0-1) crystals. Background Technology

[0002] RFeO3, a rare-earth orthoferrite crystal with a perovskite structure, is an important class of magnetic functional materials. It possesses excellent magneto-optical properties and ultrafast nanosecond-level response speeds, making it valuable for applications such as magneto-optical switches and isolators in fiber optic communication. Furthermore, RFeO3 is typically an orthorhombic perovskite structure (space group Pbnm), exhibiting centrosymmetry and belonging to nonpolar crystals. Orthorhombic RFeO3 phases, such as DyFeO3 and GdFeO3 crystals, exhibit R... 3+ with Fe 3+ The exchange contraction effect, exhibiting magnetoelectric coupling at extremely low temperatures, severely limits its practical applications. Hexagonal RFeO3 has been reported to possess room-temperature magnetoelectric coupling properties; due to the strong exchange interactions between iron ions, its Nair temperature is typically much higher than that of traditional systems such as RMnO3. However, most reported hexagonal RFeO3 materials are currently ceramics and thin film materials (Self-Assembled Hexagonal Lu). 1- x In x FeO3Nanopillars Embedded in Orthorhombic Lu 1-x In x FeO3 Nanoparticle Matrixes as Room-Temperature Multiferroic Thin Films for Memory Devices and SpintronicApplications[J].ACS Applied Nano Materials, 2020,3(8):7516-7523; A Novel Room-Temperature Multiferroic System of Hexagonal Lu 1-x In x FeO3, Adv. Funct. Mater. 2018, 28(13): 1706062), due to the problems of stress, interface effect and leakage current in ceramic and thin film materials, hexagonal phase RFeO3 crystal is an ideal material for studying intrinsic physical properties.

[0003] Under normal conditions, RFeO3 has an orthorhombic structure. When the radius of the A-site ion is small (such as In), 3+ ,Sc 3+ and Ga 3+ When FeO6 exhibits large octahedral distortion, the hexagonal RFeO3 structure also suffers from significant lattice distortion, resulting in reduced structural stability and a thermodynamically metastable state, requiring high-pressure synthesis. Currently, hexagonal RFeO3 systems primarily focus on rare-earth ions with smaller ionic radii, such as LuFeO3 and YbFeO3. Notably, TmFeO3 has not yet been reported, due to its Tm... 3+ The ionic radius is greater than that of Lu 3+ and Yb 3+ Achieving hexagonal control is even more difficult and challenging. Furthermore, In₂O₃ is highly volatile at high temperatures, easily leading to component segregation, making the growth of precisely composed hexagonal RFeO₃ crystals extremely difficult. How to grow hexagonal crystals under relatively mild conditions is a problem that urgently needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems existing in the prior art and provide a flux-based hexagonal R 1-x In x A growth method for FeO3 (R=Lu,Yb,Tm,x=0-1) crystals was developed to achieve crystal growth at ambient pressure and lower temperatures, thereby improving crystal quality.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention provides a flux-based hexagonal R 1-x In x The method for growing FeO3 crystals includes the following steps:

[0007] S1, according to R 1-x In x FeO3 crystals are stoichiometrically weighed Fe2O3, In2O3 and R2O3, where x = 0-1, and then ground in a mortar to ensure thorough mixing. After uniform mixing, the mixture is calcined at high temperature to obtain polycrystalline raw material for crystal growth.

[0008] S2, the flux and the polycrystalline raw material for crystal growth obtained in step S1 are weighed according to a molar ratio of (0.6-0.7):(0.3-0.4), mixed evenly, and then pressed into a block to obtain a polycrystalline material. The polycrystalline material is placed in the high-temperature zone of the crystal growth furnace to react and obtain a high-temperature melt. Preferably, the polycrystalline material is placed in a crucible and then placed in the high-temperature zone of the crystal growth furnace for reaction. The crucible is preferably a platinum crucible.

[0009] S3, the high-temperature melt is rapidly cooled to the high-temperature solution saturation point to induce the formation of crystal nuclei; then the descent program is started, and the crystal growth furnace is slowly lowered from the high-temperature zone to the low-temperature zone at a cooling rate of 0.3-0.6℃ / h. The vertical temperature gradient during the descent process is controlled at 10-30℃ / cm. Using this vertical temperature gradient, single crystals are grown rapidly.

[0010] S4, after the single crystal growth is completed, it is cooled to room temperature in the low temperature region at a cooling rate of 15-40℃ / h to obtain a crystal ingot;

[0011] S5, the ingot obtained in step S4 is subjected to acid treatment to separate the flux from the crystal particles, and at the same time remove the inclusions and surface impurities on the crystal surface to obtain R. 1-x In x FeO3 single crystal.

[0012] Furthermore, R can be any one of Lu, Yb, or Tm.

[0013] Furthermore, x = 0.4 - 1. Preferred In 3+ Ion substitution R 1-x In x The FeO3 (R = Lu, Yb, Tm) system enables the control of perovskite crystal structure. A hexagonal perovskite structure is achieved when x = 0.4–1, and stable hexagonal Ro crystals are obtained over a relatively wide composition range. 1-x In x FeO3 (R = Lu, Yb, Tm) crystal.

[0014] Furthermore, the high-temperature calcination temperature in step S1 is 1100-1300℃.

[0015] Further, in step S2, the flux comprises potassium fluoride and alkali metal carbonate in a molar ratio of (0.75-0.85):(0.15-0.25). The selection of KF-X2CO3 (X = Li, Na, K) composite flux significantly lowers the melting point of the solute and has advantages such as low volatility and low toxicity. A small amount of carbonate is beneficial for the formation of the hexagonal phase; it not only enables crystal growth under normal pressure but also provides a larger crystallization range, effectively reducing crystal growth temperature and viscosity, inhibiting component volatilization, facilitating mass and heat transport during crystal growth, reducing component segregation, and improving crystal quality.

[0016] Furthermore, the alkali metal carbonate is selected from at least one of Li2CO3, Na2CO3, or K2CO3.

[0017] Furthermore, in step S2, the reaction temperature in the high-temperature zone is 1050-1200℃; in step S3, the saturation point of the high-temperature solution is 900-1100℃, and the reaction temperature in the low-temperature zone is 500-650℃.

[0018] Furthermore, the bottom of the reactants in the crystal growth furnace is equipped with an air-cooled or water-cooled channel. After air or water is introduced, the local temperature of the reactants is rapidly reduced to the high-temperature solution saturation point. This enables rapid nucleation and reduces the number of spontaneous nuclei, which is beneficial for increasing crystal size and improving crystal yield.

[0019] Furthermore, the gas flow rate in the air-cooling channel is 2-5 L / min; the water flow rate in the water-cooling channel is 1-3 L / min.

[0020] Further, in step S5, the acid soaking treatment specifically involves uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:(1.5-2.5) to obtain a nitric acid solution, and then immersing the crystal in the nitric acid solution.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This invention provides a flux-based hexagonal R 1-x In x A method for growing FeO3 (R = Lu, Yb, Tm, x = 0-1) crystals employs a KF-X2CO3 (X = Li, Na, K) composite flux system. This system can completely melt the raw materials within a temperature range of 1050-1200℃, effectively reducing the crystal growth temperature and suppressing component volatilization. This composite flux system features low toxicity, low high-temperature melt viscosity, and low volatility, enabling the production of stable hexagonal R+ crystals over a wide composition range. 1- x In x FeO3 (R = Lu, Yb, Tm, x = 0.4-1) crystals; and, through a simple washing process, the crystals can be easily separated from the flux, making the entire growth process both efficient and environmentally friendly. Furthermore, indium ions (In) play a crucial role in this process, effectively inducing the hexagonal structure of R... 1-x In x Formation of FeO3 (R=Lu,Yb,Tm,x=0.4-1) crystals.

[0023] (2) This invention provides a flux-based hexagonal R 1-x In x The growth method of FeO3 (R=Lu,Yb,Tm,x=0-1) crystals, by selecting In 3+ Replace R 3+ (R = Lu, Yb, Tm), that is, R 1-x In xThe FeO3 system allows for continuous control of structures from orthorhombic to hexagonal. Furthermore, using a KF-X2CO3 (X = Li, Na, K) composite flux, R0 can be grown at atmospheric pressure and relatively low temperatures (1050-1200℃). 1-x In x FeO3 (R=Lu,Yb,Tm,x=0-1) crystals not only achieve crystal growth under normal pressure, but also have a large crystallization range, which effectively reduces the crystal growth temperature and viscosity, inhibits component volatilization, facilitates mass and heat transport during crystal growth, reduces component segregation, and improves crystal quality.

[0024] (3) This invention provides a flux-based hexagonal R 1-x In x A method for growing FeO3 (R=Lu,Yb,Tm,x=0-1) crystals is developed by designing a crystallization zone, a low-temperature annealing zone, and a high-temperature melting zone with a large temperature gradient. The vertical temperature gradient enhances the crystallization driving force. Furthermore, an air-cooling or water-cooling channel is installed at the bottom of the crucible to rapidly cool the local temperature of the reactants to the high-temperature solution saturation point after air or water is introduced. This enables rapid nucleation and reduces the number of spontaneous crystal nuclei, facilitating large-size crystal growth and high-quality yield, thus overcoming the limitations of In… 3+ Doped R 1-x In x Bottlenecks in the growth technology of FeO3 (R=Lu,Yb,Tm,x=0.4-1) hexagonal crystals. Attached Figure Description

[0025] Figure 1 Tm obtained in Example 3 of the present invention 0.2 In 0.8 Photograph of FeO3 single crystal;

[0026] Figure 2 Tm obtained in Examples 3-8 of this invention 1-x In x XRD diffraction patterns of FeO3 (x=0,0.2,0.4,0.6,0.8,1) single crystals;

[0027] Figure 3 Tm obtained in Example 3 of the present invention 0.2 In 0.8 The antiferromagnetic transition temperature curves of FeO3 crystal (hexagonal phase) are shown, where ZFC represents the magnetization of the sample under zero field cooling conditions as a function of temperature, and FC represents the magnetization of the sample under field cooling conditions as a function of temperature. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] This invention provides a flux-based hexagonal R 1-x In x The method for growing FeO3 crystals includes the following steps:

[0030] S1, according to R 1-x In x FeO3 crystals are stoichiometrically weighed Fe2O3, In2O3 and R2O3, where x = 0-1, and then ground in a mortar to ensure thorough mixing. After uniform mixing, the mixture is calcined at a high temperature of 1100-1300℃ to obtain polycrystalline raw materials for crystal growth.

[0031] S2, the flux and the polycrystalline raw material for crystal growth obtained in step S1 are weighed according to a molar ratio of (0.6-0.7):(0.3-0.4), mixed evenly, and then pressed into a block to obtain a polycrystalline material. The polycrystalline material is placed in the high-temperature zone of the crystal growth furnace to react and obtain a high-temperature melt. Preferably, the polycrystalline material is placed in a crucible and then placed together in the high-temperature zone (1050-1200℃) of the crystal growth furnace for reaction. The crucible is preferably a platinum crucible.

[0032] S3, the high-temperature melt is rapidly cooled to the high-temperature solution saturation point (900-1100℃) to induce the formation of crystal nuclei; then the descent program is started, and the crystal growth furnace is slowly lowered from the high-temperature zone to the low-temperature zone (500-650℃) at a cooling rate of 0.3-0.6℃ / h. The vertical temperature gradient during the descent process is controlled at 10-30℃ / cm, and single crystals are rapidly grown using this vertical temperature gradient;

[0033] S4, after the single crystal growth is completed, it is cooled to room temperature in the low temperature region at a cooling rate of 15-40℃ / h to obtain a crystal ingot;

[0034] S5. The ingot obtained in step S4 is subjected to acid soaking treatment, that is, concentrated nitric acid and deionized water are uniformly mixed at a volume ratio of 1:(1.5-2.5) to obtain a nitric acid solution. The ingot is then immersed in the nitric acid solution to separate the flux from the crystal particles, and at the same time remove the inclusions and surface impurities on the crystal surface to obtain R. 1-x In x FeO3 single crystal;

[0035] In some specific implementations, R is any one of Lu, Yb, or Tm.

[0036] In some specific implementations, x = 0.4-1.

[0037] In some specific embodiments, in step S2, the flux comprises potassium fluoride and an alkali metal carbonate in a molar ratio of (0.75-0.85):(0.15-0.25). The alkali metal carbonate is selected from at least one of Li₂CO₃, Na₂CO₃, or K₂CO₃.

[0038] In some specific implementations, the bottom of the reaction material in the crystal growth furnace is provided with an air-cooled channel or a water-cooled channel, which rapidly cools the local temperature of the reaction material to the high-temperature solution saturation point after air or water is introduced.

[0039] In some specific embodiments, the gas flow rate in the air-cooling channel is 2-5 L / min; the water flow rate in the water-cooling channel is 1-3 L / min.

[0040] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0041] Example 1

[0042] This embodiment provides a flux-based Lu 0.6 In 0.4 The growth method of FeO3 single crystal (hexagonal phase) includes the following steps:

[0043] (1) Using high-purity (≥4N) Fe2O3, Lu2O3 and In2O3 as raw materials, 31.94g Fe2O3, 47.75g Lu2O3 and 22.21g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials are fully mixed. The mixture was then calcined at 1300℃ for 10h to obtain polycrystalline raw materials for crystal growth.

[0044] (2) Weigh flux KF-Li2CO3 and polycrystalline raw material for crystal growth obtained in step (1) according to a molar ratio of 0.51:0.09:0.4, mix them evenly to a total of 138g, press them into polycrystalline blocks, and put them into a crucible, which is a platinum crucible.

[0045] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1200℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 12 hours to obtain a high-temperature melt.

[0046] (4) Set up a local gas cooling channel at the bottom of the crucible and introduce oxygen at a flow rate of 2.5 L / min to rapidly cool down to the high temperature solution saturation point of 1100℃ to induce the formation of crystal nuclei; then start the descent program and slowly lower the crucible from the high temperature zone to the low temperature zone of 650℃ at a rate of 0.5℃ / h, with the temperature gradient controlled at 30℃ / cm. Utilize the vertical temperature gradient to rapidly grow centimeter-sized single crystals. After the crystal growth is completed, cool down to room temperature at a rate of 40℃ / h and remove the crucible ingot.

[0047] (5) The ingots obtained in step (4) are processed by uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:2.4 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the crystal surface, thereby obtaining Lu. 0.6 In 0.4 FeO3 single crystal.

[0048] Example 2

[0049] This embodiment provides a flux-based Yb 0.4 In 0.6 The growth method of FeO3 single crystal (hexagonal phase) includes the following steps:

[0050] (1) Using high-purity (≥4N) Fe2O3, Tm2O3 and In2O3 as raw materials, 27.95g Fe2O3, 27.59g Yb2O3 and 29.15g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials are fully mixed. The mixture was then calcined at 1200℃ for 10h to obtain polycrystalline raw materials for crystal growth.

[0051] (2) Weigh the flux KF-Na2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) according to the molar ratio of 0.52:0.13:0.35, mix them evenly to a total of 129g, press them into a polycrystalline block, and put them into a crucible, which is a platinum crucible.

[0052] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1150℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 12 hours to obtain a high-temperature melt.

[0053] (4) Set up a local water cooling channel at the bottom of the crucible and pass in circulating cooling water at a flow rate of 3L / min to rapidly cool down to the high temperature solution saturation point of 1050℃ to induce the formation of crystal nuclei; then start the descent program and slowly lower the crucible from the high temperature zone to the low temperature zone of 600℃ at a rate of 0.4℃ / h, with the temperature gradient controlled at 20℃ / cm. Utilize the vertical temperature gradient to rapidly grow centimeter-sized single crystals. After the crystal growth is completed, lower it to room temperature at a rate of 30℃ / h and remove the crucible ingot.

[0054] (5) The ingot obtained in step (4) is processed by uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:1.5 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the crystal surface, thereby obtaining Yb. 0.4 In 0.6 FeO3 single crystal.

[0055] Example 3

[0056] This embodiment provides a flux-based Tm 0.2 In 0.8 The growth method of FeO3 single crystal (hexagonal phase) includes the following steps:

[0057] (1) Using high-purity (≥4N) Fe2O3, Tm2O3 and In2O3 as raw materials, 23.95g Fe2O3, 11.58g Tm2O3 and 33.32g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials are fully mixed. The mixture was then calcined at 1150℃ for 10h to obtain polycrystalline raw materials for crystal growth.

[0058] (2) Weigh flux KF-K2CO3 and polycrystalline raw material for crystal growth obtained in step (1) according to a molar ratio of 0.525:0.175:0.3, mix them evenly to a total of 124g, press them into a polycrystalline block, and put them into a crucible, which is a platinum crucible.

[0059] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1100℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 12 hours to obtain a high-temperature melt.

[0060] (4) Design a local air cooling channel at the bottom of the crucible and introduce air for cooling. The gas flow rate is 3L / min. The temperature is rapidly reduced to the high temperature solution saturation point of 1050℃ to induce the formation of crystal nuclei. Then, start the descent program. The crucible is slowly lowered from the high temperature zone to the low temperature zone of 580℃ at a rate of 0.3℃ / h. The temperature gradient is controlled at 15℃ / cm. Using the vertical temperature gradient, centimeter-sized single crystals are rapidly grown. After the crystal growth is completed, the temperature is reduced to room temperature at a rate of 20℃ / h and the crucible ingot is removed.

[0061] (5) The ingots obtained in step (4) are processed by uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:2.3 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the crystal surface, thereby obtaining Tm. 0.2 In 0.8 FeO3 single crystal.

[0062] Example 4

[0063] This embodiment provides a flux-based Tm 0.4 In 0.6 The growth method of FeO3 single crystal (hexagonal phase) includes the following steps:

[0064] (1) Using high-purity (≥4N) Fe2O3, Tm2O3 and In2O3 as raw materials, 23.95g Fe2O3, 23.15g Tm2O3 and 24.99g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials are fully mixed. The mixture was then calcined at 1150℃ for 10h to obtain polycrystalline raw materials for crystal growth.

[0065] (2) Weigh flux KF-K2CO3 and polycrystalline raw material for crystal growth obtained in step (1) according to the molar ratio of 0.574:0.126:0.3, mix them evenly to a total of 123g, press them into polycrystalline blocks, and put them into a crucible, which is a platinum crucible.

[0066] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1120℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 10 hours to obtain a high-temperature melt.

[0067] (4) Design a local air cooling channel at the bottom of the crucible and introduce air for cooling. The gas flow rate is 2.8 L / min. The temperature is rapidly reduced to the high temperature solution saturation point of 1080℃ to induce the formation of crystal nuclei. Then, start the descent program. The crucible is slowly lowered from the high temperature zone to the low temperature zone of 560℃ at a rate of 0.32℃ / h. The temperature gradient is controlled at 25℃ / cm. Using the vertical temperature gradient, centimeter-sized single crystals are rapidly grown. After the crystal growth is completed, the temperature is reduced to room temperature at a rate of 18℃ / h and the crucible ingot is removed.

[0068] (5) The ingots obtained in step (4) are processed by uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:1.5 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the surface of the crystals, thereby obtaining Tm. 0.4 In 0.6 FeO3 single crystal.

[0069] Example 5

[0070] This embodiment provides a flux-based Tm 0.6 In 0.4 The growth method of FeO3 single crystal (hexagonal phase) includes the following steps:

[0071] (1) Using high-purity (≥4N) Fe2O3, Tm2O3 and In2O3 as raw materials, 27.95g Fe2O3, 40.52g Tm2O3 and 19.43g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials are fully mixed. The mixture was then calcined at 1150℃ for 10h to obtain polycrystalline raw materials for crystal growth.

[0072] (2) Weigh flux KF-K2CO3 and polycrystalline raw material for crystal growth obtained in step (1) according to the molar ratio of 0.5265:0.1235:0.35, mix them evenly to a total of 136g, press them into polycrystalline blocks, and put them into a crucible, which is a platinum crucible.

[0073] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1140℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 11 hours to obtain a high-temperature melt.

[0074] (4) Design a local water cooling channel at the bottom of the crucible and introduce circulating cooling water at a flow rate of 2.5 L / min to rapidly cool down to the high temperature solution saturation point of 1050℃ to induce the formation of crystal nuclei; then start the descent program and slowly lower the crucible from the high temperature zone to the low temperature zone of 585℃ at a rate of 0.36℃ / h, with the temperature gradient controlled at 28℃ / cm. Utilize the vertical temperature gradient to rapidly grow centimeter-sized single crystals. After the crystal growth is completed, cool down to room temperature at a rate of 25℃ / h and remove the crucible ingot.

[0075] (5) The ingots obtained in step (4) are processed by uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:1.8 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the surface of the crystals, thereby obtaining Tm. 0.6 In 0.4 FeO3 single crystal.

[0076] Example 6

[0077] This embodiment provides a flux-based Tm 0.8 In 0.2 The growth method of FeO3 single crystal (orthorhombic phase) includes the following steps:

[0078] (1) Using high-purity (≥4N) Fe2O3, Tm2O3 and In2O3 as raw materials, 23.95g Fe2O3, 46.30g Tm2O3 and 8.33g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials are fully mixed. The mixture was then calcined at 1150℃ for 10h to obtain polycrystalline raw materials for crystal growth.

[0079] (2) Weigh flux KF-K2CO3 and polycrystalline raw material for crystal growth obtained in step (1) according to the molar ratio of 0.532:0.168:0.3, mix them evenly to a total of 133g, press them into polycrystalline blocks, and put them into a crucible, which is a platinum crucible.

[0080] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1090℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 12 hours to obtain a high-temperature melt.

[0081] (4) Design a local gas cooling channel at the bottom of the crucible, introduce oxygen for cooling, with a gas flow rate of 5L / min, and rapidly cool down to the high temperature solution saturation point of 1000℃ to induce the formation of crystal nuclei; then start the descent program, and slowly lower the crucible from the high temperature zone to the low temperature zone of 590℃ at a rate of 0.38℃ / h, with the temperature gradient controlled at 35℃ / cm. Utilize the vertical temperature gradient to rapidly grow centimeter-sized single crystals. After the crystal growth is completed, cool down to room temperature at 32℃ / h and remove the crucible ingot.

[0082] (5) The ingots obtained in step (4) are processed by uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:2.5 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the crystal surface, thereby obtaining Tm. 0.8 In 0.2 FeO3 single crystal.

[0083] Example 7

[0084] This embodiment provides a method for growing TmFeO3 single crystals (orthorhombic phase) based on flux, including the following steps:

[0085] (1) Using high-purity (≥4N) Fe2O3 and Tm2O3 as raw materials, 31.94g Fe2O3 and 77.17g Tm2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials were fully mixed. The mixture was then calcined at 1155℃ for 12h to obtain polycrystalline raw materials for crystal growth.

[0086] (2) Weigh the flux KF-Li2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) according to the molar ratio of 0.492:0.108:0.4, mix them evenly to a total of 146g, press them into a polycrystalline block, and put them into a crucible, which is a platinum crucible.

[0087] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1180℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 12 hours to obtain a high-temperature melt.

[0088] (4) Design a local air cooling channel at the bottom of the crucible and introduce air for cooling. The gas flow rate is 4.5 L / min. The temperature is rapidly reduced to the high temperature solution saturation point of 1090℃ to induce the formation of crystal nuclei. Then, start the descent program. The crucible is slowly lowered from the high temperature zone to the low temperature zone of 600℃ at a rate of 0.5℃ / h. The temperature gradient is controlled at 50℃ / cm. Using the vertical temperature gradient, centimeter-sized single crystals are rapidly grown. After the crystal growth is completed, the temperature is reduced to room temperature at a rate of 36℃ / h and the crucible ingot is removed.

[0089] (5) The crystal ingot obtained in step (4) is processed by mixing concentrated nitric acid and deionized water in a volume ratio of 1:2 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the surface of the crystal to obtain TmFeO3 single crystal.

[0090] Example 8

[0091] This embodiment provides a flux-based method for growing InFeO3 single crystals (hexagonal phase), comprising the following steps:

[0092] (1) Using high-purity (≥4N) Fe2O3 and In2O3 as raw materials, 31.94g Fe2O3 and 55.53g In2O3 were weighed according to the stoichiometric ratio and ground together in an agate mortar for 3h to ensure that the raw materials were fully mixed. The mixture was then calcined at 1150℃ for 12h to obtain polycrystalline raw materials for crystal growth.

[0093] (2) Weigh the flux KF-Li2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) according to the molar ratio of 0.468:0.132:0.4, mix them evenly to a total of 124g, press them into a polycrystalline block, and put them into a crucible, which is a platinum crucible.

[0094] (3) The crucible is moved into the crystal growth furnace, and the temperature of the high-temperature zone is controlled at 1200℃ to ensure that the raw materials are fully melted. The temperature is then maintained at this temperature for 10 hours to obtain a high-temperature melt.

[0095] (4) Design a local water cooling channel at the bottom of the crucible and introduce circulating cooling water at a flow rate of 2L / min to rapidly cool down to the high temperature solution saturation point of 1100℃ to induce the formation of crystal nuclei; then start the descent program and slowly lower the crucible from the high temperature zone to the low temperature zone of 575℃ at a rate of 0.3℃ / h, with the temperature gradient controlled at 15℃ / cm. Utilize the vertical temperature gradient to rapidly grow centimeter-sized single crystals. After the crystal growth is completed, cool down to room temperature at a rate of 25℃ / h and remove the crucible ingot.

[0096] (5) The crystal ingot obtained in step (4) is processed by mixing concentrated nitric acid and deionized water in a volume ratio of 1:2.5 to perform acid treatment on the material, separating the flux from the crystal particles, and removing the inclusions and surface impurities on the surface of the crystal to obtain InFeO3 single crystal.

[0097] The Tm grown in Example 3 of this invention 0.2 In 0.8 Photograph of FeO3 crystal (hexagonal phase) as shown Figure 1 As shown, the crystal is a crystal with a distinct crystallographic orientation and a size exceeding 15 mm, which has not been reported in the currently published literature.

[0098] Figure 2 Tm obtained by the method of the present invention 1-x In x XRD diffraction patterns of FeO3 (x=0,0.2,0.4,0.6,0.8,1) single crystals (Examples 3-8), by Figure 2 It can be seen that when In 3+ When the doping amount x is greater than 0.4, a single-phase hexagonal single crystal can be obtained.

[0099] Using a comprehensive physical property measurement system (PPMS) to obtain, for example Figure 3 The MT curves shown in this invention employ two cooling methods for measurement: zero-field cooling and field cooling, with a measurement temperature range of 5-400K. Zero-field cooling (ZFC) mode involves first cooling the sample to 5K under zero external magnetic field conditions, and then raising the temperature under a certain magnetic field to measure the MT curve from 5K to 400K. Field cooling (FC) mode, on the other hand, involves cooling the sample to 5K using the magnetic field measured in ZFC, and then raising the temperature to measure the MT curve from 5K to 400K.

[0100] Figure 3 The Tm grown in Example 3 of the present invention is shown. 0.2 In 0.8 The antiferromagnetic transition temperature T of FeO3 crystal (hexagonal phase) N At approximately 163 K, the magnetic transition temperature of this crystal was determined for the first time.

[0101] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A flux-based hexagonal R 1-x In x The method for growing FeO3 crystals is characterized by, Includes the following steps: S1, according to R 1-x In x FeO3 crystals are stoichiometrically weighed Fe2O3, In2O3 and R2O3, where x = 0.4-1, mixed evenly and then calcined at high temperature to obtain polycrystalline raw materials for crystal growth. S2, Weigh the flux and the polycrystalline raw material for crystal growth obtained in step S1 according to the molar ratio of (0.6-0.7):(0.3-0.4), mix them evenly, press them into blocks to obtain polycrystalline blocks, and place the polycrystalline blocks in the high-temperature zone of the crystal growth furnace to react and obtain high-temperature melt; S3, the high-temperature melt is rapidly cooled to the high-temperature solution saturation point to induce the formation of crystal nuclei; then the descent program is started, and the crystal growth furnace is slowly lowered from the high-temperature zone to the low-temperature zone at a cooling rate of 0.3-0.6℃ / h. The vertical temperature gradient during the descent process is controlled at 10-30℃ / cm. Using this vertical temperature gradient, single crystals are grown rapidly. S4, after the single crystal growth is completed, it is cooled to room temperature in the low temperature region at a cooling rate of 15-40℃ / h to obtain a crystal ingot; S5, the ingot obtained in step S4 is subjected to acid treatment to obtain R. 1-x In x FeO3 single crystal; R is any one of Lu, Yb, or Tm; In step S2, the flux comprises potassium fluoride and alkali metal carbonate in a molar ratio of (0.75-0.85):(0.15-0.25); the alkali metal carbonate is selected from at least one of Li2CO3, Na2CO3 or K2CO3. In step S2, the reaction temperature in the high-temperature zone is 1050-1200℃; In step S3, the saturation point of the high-temperature solution is 900-1100℃, and the reaction temperature in the low-temperature region is 500-650℃.

2. A flux-based hexagonal R according to claim 1 1-x In x The method for growing FeO3 crystals is characterized by, The high-temperature calcination temperature in step S1 is 1100-1300℃.

3. A flux-based hexagonal R according to claim 1 1-x In x The method for growing FeO3 crystals is characterized by, The bottom of the reaction material in the crystal growth furnace is equipped with an air-cooling channel or a water-cooling channel. After air or water is introduced, the local temperature of the reaction material is rapidly reduced to the high-temperature solution saturation point.

4. A flux-based hexagonal R according to claim 3 1-x In x The method for growing FeO3 crystals is characterized by, The gas flow rate in the air-cooling channel is 2-5 L / min; the water flow rate in the water-cooling channel is 1-3 L / min.

5. A flux-based hexagonal R according to claim 1 1-x In x The method for growing FeO3 crystals is characterized by, In step S5, the acid soaking treatment specifically involves uniformly mixing concentrated nitric acid and deionized water at a volume ratio of 1:(1.5-2.5) to obtain a nitric acid solution, and then immersing the crystal in the nitric acid solution.

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