Growth method of hexagonal R1-xInxFeO3 (R = Lu, Yb, Tm, x-0-1) crystal based on fluxing agent

Abstract

The invention belongs to the technical field of crystal growth, and relates to a growth method of a hexagonal R1-xInxFeO3 (R = Lu, Yb, Tm, x = 0-1) crystal based on a fluxing agent. According to the method, by introducing In < 3 + >, an orthogonal structure RFeO3 (R = Lu, Yb, Tm) is successfully induced into a hexagonal structure InFeO3; in addition, according to the method, a KF-X2CO3 (X = Li, Na or K) composite fluxing agent system is adopted, and stable R1-xInxFeO3 (R = Lu, Yb or Tm) crystals can be grown at normal pressure and low temperature. Compared with the prior art, the method has the advantages that the harsh requirement that the hexagonal RFeO3 crystal needs to grow at high temperature and high pressure is overcome, the grown crystal is controllable in component, continuous change from an orthogonal structure to a hexagonal structure can be realized, meanwhile, the crystal size can reach the centimeter magnitude, and the crystal quality is high.

Description

Technical Field

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

[0002] The rare earth orthoferrite RFeO3 crystal with perovskite structure is an important type of magnetic functional material. It has excellent magneto-optical properties and ultrafast response speed in nanoseconds, and has important application value in the fields of magneto-optical switches and isolators in optical fiber communications. In addition, RFeO3 is usually an orthorhombic perovskite structure (space group is Pbnm), has central symmetry, and is a non-polar crystal. Orthorhombic phase RFeO3, such as DyFeO3 and GdFeO3 crystals, has a high R ratio due to R 3+ with Fe 3+ The exchange contraction effect has a magnetoelectric coupling effect at extremely low temperatures, which seriously limits its practical application. Hexagonal RFeO3 has been reported to have room temperature magnetoelectric coupling properties. Due to the strong exchange interaction between iron ions, its Neel temperature is usually much higher than traditional systems such as RMnO3. However, most of the hexagonal RFeO3 materials reported so far are 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 ceramics and thin film materials, hexagonal RFeO3 crystal is an ideal material for studying intrinsic physical properties.

[0003] Under normal conditions, RFeO3 has an orthorhombic structure. 3+ , Sc 3+ and Ga 3+ When the FeO6 octahedron is distorted greatly, the hexagonal RFeO3 lattice is distorted greatly, the structural stability is reduced, and it belongs to the thermodynamic metastable state, which requires high pressure technology to synthesize. At present, the hexagonal RFeO3 system is mainly concentrated on rare earth ions with small ionic radius, such as LuFeO3, YbFeO3, etc., especially TmFeO3 has not been reported yet, because Tm 3+ The ionic radius is larger than Lu 3+ and Yb 3+ , achieving hexagonal regulation is more difficult and challenging. In addition, In2O3 is very volatile at high temperatures, which can easily lead to component segregation, making it very difficult to grow hexagonal RFeO3 crystals with precise components. How to grow hexagonal crystals under relatively mild conditions is an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of the prior art and provide a hexagonal R based on flux. 1-x In x A method for growing FeO3 (R=Lu, Yb, Tm, x=0-1) crystals realizes crystal growth at normal pressure and relatively low temperature, thereby improving crystal quality.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

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

[0007] S1, according to R 1-x In x Fe2O3, In2O3 and R2O3 are weighed in a stoichiometric ratio of FeO3 crystals, wherein x=0-1, and then ground in a mortar to ensure sufficient mixing, and after uniform mixing, calcined at high temperature to obtain a polycrystalline raw material for crystal growth;

[0008] S2, weighing the flux and the polycrystalline raw material for crystal growth obtained in step S1 according to a molar ratio of (0.6-0.7):(0.3-0.4), mixing them evenly and pressing them into blocks to obtain a polycrystalline block, placing the polycrystalline block in a high temperature zone of a crystal growth furnace for reaction to obtain a high temperature melt; preferably, the polycrystalline block is loaded into a crucible, and then placed in the high temperature zone of the crystal growth furnace for reaction, and the crucible is preferably a platinum crucible;

[0009] S3, rapidly cooling the high temperature melt to the saturation point of the high temperature solution to induce the formation of crystal nuclei; then starting the descending program, slowly descending from the high temperature zone of the crystal growth furnace to the low temperature zone at a cooling rate of 0.3-0.6°C / h, and controlling the vertical temperature gradient during the descent process at 10-30°C / cm, and utilizing the vertical temperature gradient to rapidly grow single crystals;

[0010] S4, after the single crystal is grown, the temperature is lowered to room temperature at a rate of 15-40°C / h in the low temperature zone to obtain a crystal ingot;

[0011] S5, treating the crystal ingot obtained in step S4 with acid to separate the flux from the crystal particles, and removing the inclusions and surface impurities on the surface of the crystal to obtain R 1-x In x FeO3 single crystal.

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

[0013] Furthermore, x=0.4-1. Preferably In 3+ Ion replacement R 1-x In x FeO3 (R = Lu, Yb, Tm) system realizes the regulation of the perovskite crystal structure. When x = 0.4-1, it is a hexagonal perovskite structure, and a stable hexagonal R is obtained in a wide range of components. 1-x In x FeO3(R=Lu,Yb,Tm) crystals.

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

[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). Selecting KF-X2CO3 (X = Li, Na, K) composite flux can significantly reduce the melting point of the solute, and has the advantages of low volatility and low toxicity. A small amount of carbonate is conducive to the formation of hexagonal phase; it not only realizes crystal growth under normal pressure; at the same time, the crystallization interval is large, which effectively reduces the crystal growth temperature and viscosity, inhibits the volatilization of components, is conducive to the mass and heat transfer during the crystal growth process, reduces component segregation, and improves the crystallization 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°C; in step S3, the saturation point of the high temperature solution is 900-1100°C, and the reaction temperature in the low temperature zone is 500-650°C.

[0018] Furthermore, an air cooling channel or a water cooling channel is provided at the bottom of the reaction material in the crystal growth furnace, and the local temperature of the reaction material is quickly cooled to the saturation point of the high-temperature solution after ventilation or water is passed through. Rapid nucleation can be achieved and the number of spontaneous nucleations can be reduced, which is conducive to increasing the crystal size and improving the 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 treatment is specifically to uniformly mix concentrated nitric acid and deionized water in a volume ratio of 1:(1.5-2.5) to obtain a nitric acid solution, and then immerse the ingot in the nitric acid solution.

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

[0022] (1) The present invention provides a hexagonal R based on flux 1-x In x A method for growing FeO3 (R = Lu, Yb, Tm, x = 0-1) crystals, which uses a KF-X2CO3 (X = Li, Na, K) composite flux system, which can completely melt the raw materials within a temperature range of 1050-1200°C, effectively reduce the crystal growth temperature, and inhibit component volatilization. This composite flux system has the characteristics of low toxicity, low high-temperature melt viscosity and low volatility, and can obtain stable hexagonal R in a wide component 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. In addition, indium ions (In) play a key role in this process, effectively inducing the hexagonal structure R 1-x In x Formation of FeO3 (R=Lu, Yb, Tm, x=0.4-1) crystals.

[0023] (2) The present invention provides a hexagonal R based on flux 1-x In x The growth method of FeO3 (R = Lu, Yb, Tm, x = 0-1) crystal is to select In 3+ Replace R 3+ (R=Lu,Yb,Tm), that is, R 1-x In xFeO3 system can achieve continuous regulation from orthorhombic structure to hexagonal structure. In addition, KF-X2CO3 (X = Li, Na, K) composite flux is used to grow R at normal pressure and low temperature (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 larger crystallization range, which effectively reduces the crystal growth temperature and viscosity, inhibits component volatilization, is beneficial to the mass and heat transfer during the crystal growth process, reduces component segregation, and improves crystallization quality.

[0024] (3) The present invention provides a hexagonal R based on flux 1-x In x The method for growing FeO3 (R = Lu, Yb, Tm, x = 0-1) crystals is to design a crystallization zone, a low-temperature annealing zone and a high-temperature melting zone with a large temperature gradient. The vertical temperature gradient increases the driving force for crystallization. In addition, an air cooling channel or a water cooling channel is provided at the bottom of the crucible. After ventilation or water is passed, the local temperature of the reaction material is quickly cooled to the saturation point of the high-temperature solution. Rapid nucleation can be achieved and the number of spontaneous nucleation of crystals can be reduced, which is conducive to the large-size growth and high-quality output of crystals, thus breaking through the In 3+ Doped R 1-x In x The technical bottleneck of FeO3 (R=Lu, Yb, Tm, x=0.4-1) hexagonal crystal growth. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 Tm obtained in Example 3-8 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;

[0027] Figure 3 is the Tm obtained in Example 3 of the present invention 0.2 In 0.8 Antiferromagnetic transition temperature curve of FeO3 crystal (hexagonal phase), where ZFC is the change of the magnetization intensity of the sample with temperature under zero field cooling conditions, and FC is the change of the magnetization intensity of the sample with temperature under field cooling conditions. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

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

[0030] S1, according to R 1-x In x Fe2O3, In2O3 and R2O3 are weighed in a stoichiometric ratio of FeO3 crystals, wherein x=0-1, and then ground in a mortar to ensure sufficient mixing, and after uniform mixing, calcined at a high temperature of 1100-1300°C to obtain a polycrystalline raw material for crystal growth;

[0031] S2, weighing the flux and the polycrystalline raw material for crystal growth obtained in step S1 according to a molar ratio of (0.6-0.7): (0.3-0.4), mixing them evenly and pressing them into blocks to obtain a polycrystalline block, placing the polycrystalline block in a high temperature zone of a crystal growth furnace for reaction to obtain a high temperature melt; preferably, the polycrystalline block is loaded into a crucible, and then placed in a high temperature zone (1050-1200° C.) of the crystal growth furnace for reaction, and the crucible is preferably a platinum crucible;

[0032] S3, rapidly cooling the high temperature melt to the saturation point of the high temperature solution (900-1100°C) to induce the formation of crystal nuclei; then starting the descending program, slowly descending from the high temperature zone of the crystal growth furnace to the low temperature zone (500-650°C) at a cooling rate of 0.3-0.6°C / h, and controlling the vertical temperature gradient during the descent process at 10-30°C / cm, and using the vertical temperature gradient to rapidly grow single crystals;

[0033] S4, after the single crystal is grown, the temperature is lowered to room temperature at a rate of 15-40°C / h in the low temperature zone to obtain a crystal ingot;

[0034] S5, subjecting the crystal ingot obtained in step S4 to acid treatment, that is, uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1: (1.5-2.5) to obtain a nitric acid solution, and then immersing the crystal ingot in the nitric acid solution to separate the flux from the crystal particles, and removing the inclusions and surface impurities on the surface of the crystal to obtain R 1-x In x FeO3 single crystal;

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

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

[0037] In some specific embodiments, 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.

[0038] In some specific embodiments, an air cooling channel or a water cooling channel is provided at the bottom of the reaction material in the crystal growth furnace, and the local temperature of the reaction material is quickly cooled to the saturation point of the high-temperature solution after ventilation or water is passed.

[0039] In some specific implementations, 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 the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0041] Example 1

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

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

[0044] (2) weighing flux KF-Li2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.51:0.09:0.4, uniformly mixing a total of 138 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0046] (4) a local air cooling channel is set at the bottom of the crucible, and oxygen is introduced at a gas flow rate of 2.5 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution of 1100°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone of 650°C at a rate of 0.5°C / h, and the temperature gradient is controlled at 30°C / cm. A vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, it is lowered to room temperature at a rate of 40°C / h, and the crucible ingot is taken out;

[0047] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:2.4, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, thereby obtaining Lu 0.6 In 0.4 FeO3 single crystal.

[0048] Example 2

[0049] This embodiment provides a Yb based on flux 0.4 In 0.6 The method for growing FeO3 single crystal (hexagonal phase) comprises the following steps:

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

[0051] (2) weighing flux KF-Na2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.52:0.13:0.35, uniformly mixing a total of 129 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0053] (4) a local water cooling channel is provided at the bottom of the crucible, circulating cooling water is introduced, the water flow rate is 3 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution of 1050°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone of 600°C at a rate of 0.4°C / h, and the temperature gradient is controlled at 20°C / cm. A centimeter-level single crystal is rapidly grown using a vertical temperature gradient. After the crystal is grown, the temperature is lowered to room temperature at a rate of 30°C / h, and the crucible ingot is taken out;

[0054] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:1.5, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, 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 method for growing FeO3 single crystal (hexagonal phase) comprises the following steps:

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

[0058] (2) weighing flux KF-K2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.525:0.175:0.3, uniformly mixing a total of 124 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0060] (4) A local air cooling channel is designed at the bottom of the crucible, and air is introduced for cooling. The gas flow rate is 3 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution at 1050°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone at a rate of 0.3°C / h. The temperature gradient is controlled at 15°C / cm. The vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, it is cooled to room temperature at a rate of 20°C / h, and the crucible ingot is taken out;

[0061] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:2.3, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, 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 method for growing FeO3 single crystal (hexagonal phase) comprises the following steps:

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

[0065] (2) weighing flux KF-K2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.574:0.126:0.3, uniformly mixing a total of 123 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0067] (4) A local air cooling channel is designed at the bottom of the crucible, and air is introduced for cooling. The gas flow rate is 2.8 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution at 1080°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone at a rate of 0.32°C / h. The temperature gradient is controlled at 25°C / cm. The vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, the temperature is lowered to room temperature at a rate of 18°C / h, and the crucible ingot is taken out;

[0068] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:1.5, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, 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 method for growing FeO3 single crystal (hexagonal phase) comprises the following steps:

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

[0072] (2) weighing flux KF-K2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.5265:0.1235:0.35, uniformly mixing a total of 136 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0074] (4) A local water cooling channel is designed at the bottom of the crucible, and circulating cooling water is introduced at a water flow rate of 2.5 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution of 1050°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone of 585°C at a rate of 0.36°C / h, and the temperature gradient is controlled at 28°C / cm. The vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, it is cooled to room temperature at a rate of 25°C / h, and the crucible ingot is taken out;

[0075] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:1.8, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, 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 method for growing FeO3 single crystal (orthorhombic phase) comprises the following steps:

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

[0079] (2) weighing flux KF-K2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.532:0.168:0.3, uniformly mixing a total of 133 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0081] (4) A local air cooling channel is designed at the bottom of the crucible, and oxygen is introduced for cooling. The gas flow rate is 5 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution at 1000°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone at a rate of 0.38°C / h to 590°C. The temperature gradient is controlled at 35°C / cm. The vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, the temperature is lowered to room temperature at 32°C / h, and the crucible ingot is taken out;

[0082] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:2.5, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, thereby obtaining Tm 0.8 In 0.2 FeO3 single crystal.

[0083] Example 7

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

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

[0086] (2) weighing flux KF-Li2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.492:0.108:0.4, uniformly mixing a total of 146 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0088] (4) A local air cooling channel is designed at the bottom of the crucible, and air is introduced for cooling. The gas flow rate is 4.5 L / min, and the temperature is rapidly lowered to the saturation point of the high-temperature solution at 1090°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly lowered from the high-temperature zone to the low-temperature zone at a rate of 0.5°C / h to 600°C. The temperature gradient is controlled at 50°C / cm. The vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, the temperature is lowered to room temperature at 36°C / h, and the crucible ingot is taken out;

[0089] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:2, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, thereby obtaining a TmFeO3 single crystal.

[0090] Example 8

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

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

[0093] (2) weighing flux KF-Li2CO3 and the polycrystalline raw material for crystal growth obtained in step (1) in a molar ratio of 0.468:0.132:0.4, uniformly mixing a total of 124 g, pressing into a polycrystalline block, and placing the block into a crucible, wherein the crucible is a platinum crucible;

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

[0095] (4) A local water cooling channel is designed at the bottom of the crucible, and circulating cooling water is introduced at a water flow rate of 2 L / min, and the temperature is rapidly reduced to the saturation point of the high-temperature solution of 1100°C to induce the formation of crystal nuclei; then the descending program is started, and the crucible is slowly reduced from the high-temperature zone to the low-temperature zone of 575°C at a rate of 0.3°C / h, and the temperature gradient is controlled at 15°C / cm. The vertical temperature gradient is used to rapidly grow centimeter-level single crystals. After the crystal is grown, it is cooled to room temperature at a rate of 25°C / h, and the crucible ingot is taken out;

[0096] (5) The ingot obtained in step (4) is treated by uniformly mixing concentrated nitric acid and deionized water in a volume ratio of 1:2.5, and the material is treated with acid to separate the flux from the crystal particles, and at the same time, the inclusions and surface impurities on the surface of the crystal are removed, thereby obtaining an InFeO3 single crystal.

[0097] The Tm grown in Example 3 of the present invention 0.2 In 0.8 FeO3 crystal (hexagonal phase) photo Figure 1 As shown, the crystal has a distinct crystallographic orientation and a size of more than 15 mm, which has not been reported in the current public literature.

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

[0099] The comprehensive physical property measurement system (PPMS) was used to obtain Figure 3 The MT curve shown in the figure, there are two cooling modes for measuring the MT curve in the present invention, namely zero field cooling and field cooling, and the measuring temperature range is 5-400 K. The Zero Field Cooling (ZFC) mode is a process of 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; while the Field Cooling (FC) mode is a process of cooling the sample to 5K based on the magnetic field measured by ZFC, and then raising the temperature to measure the MT curve from 5K to 400K.

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

[0101] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the scope of protection of the present invention.

Claims

1. A flux-based hexagonal R 1-x In x A method for growing FeO3 crystals, characterized in that: The steps include: S1, according to R 1-x In x Fe2O3, In2O3 and R2O3 are weighed in a stoichiometric ratio of FeO3 crystals, wherein x=0-1, mixed evenly and calcined at high temperature to obtain a polycrystalline raw material for crystal growth; S2, weighing the flux and the polycrystalline raw material for crystal growth obtained in step S1 according to a molar ratio of (0.6-0.7):(0.3-0.4), mixing them evenly and pressing them into blocks to obtain a polycrystalline block, placing the polycrystalline block in a high temperature zone of a crystal growth furnace for reaction to obtain a high temperature melt; S3, rapidly cooling the high temperature melt to the saturation point of the high temperature solution to induce the formation of crystal nuclei; then starting the descending program, slowly descending from the high temperature zone of the crystal growth furnace to the low temperature zone at a cooling rate of 0.3-0.6°C / h, and controlling the vertical temperature gradient during the descent process at 10-30°C / cm, and utilizing the vertical temperature gradient to rapidly grow single crystals; S4, after the single crystal is grown, the temperature is lowered to room temperature at a rate of 15-40°C / h in the low temperature zone to obtain a crystal ingot; S5, treating the crystal ingot obtained in step S4 with acid to obtain R 1-x In x FeO3 single crystal.

2. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: R is any one of Lu, Yb or Tm.

3. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: x＝0.4-1。 4. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: The temperature of high temperature calcination in step S1 is 1100-1300°C.

5. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: 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).

6. A hexagonal R based on flux according to claim 5 1-x In x A method for growing FeO3 crystals, characterized in that: The alkali metal carbonate is selected from at least one of Li2CO3, Na2CO3 or K2CO3.

7. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: In step S2, the reaction temperature in the high temperature zone is 1050-1200°C; In step S3, the saturation point of the high-temperature solution is 900-1100°C, and the reaction temperature in the low-temperature zone is 500-650°C.

8. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: An air cooling channel or a water cooling channel is provided at the bottom of the reaction material in the crystal growth furnace, and the local temperature of the reaction material is quickly cooled to the saturation point of the high-temperature solution after ventilation or water is passed.

9. A hexagonal R based on flux according to claim 8 1-x In x A method for growing FeO3 crystals, characterized in that: 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.

10. A hexagonal R based on flux according to claim 1 1-x In x A method for growing FeO3 crystals, characterized in that: In step S5, the acid treatment is specifically to uniformly mix concentrated nitric acid and deionized water in a volume ratio of 1: (1.5-2.5) to obtain a nitric acid solution, and then immerse the ingot in the nitric acid solution.

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