A rutile single crystal material with magneto-electric anisotropy and a preparation method thereof

Abstract

A kind of rutile single crystal material with magnetic-electric anisotropy and preparation method thereof belong to functional crystal technical field.The starting raw material is weighed according to specific chemical formula in the present application, and then raw doping powder is obtained by ball milling, drying and calcination, then single crystal is grown by flame fusion method, and single crystal is obtained by controlling gas flow to realize equal-diameter growth, and wafer with different orientations is obtained by annealing and directional cutting of the grown single crystal.In the process of preparing rutile single crystal material by the method provided in the present application, ordered defects dipoles are formed in the crystal, which can induce room-temperature ferromagnetism and giant dielectric properties, achieve higher carrier mobility to improve transistor speed, and promote the development of components beyond the traditional silicon-based framework to a new paradigm.

Description

Technical Field

[0001] This invention belongs to the field of functional crystal technology, specifically relating to a rutile single crystal material with magnetic-electric anisotropy and its preparation method. Background Technology

[0002] Miniaturization of storage materials is one of the core driving forces behind technological evolution in the information age. Firstly, it directly propels electronic devices towards thinner, lighter, smaller, and more highly integrated designs, enabling portable terminals such as smartphones and wearable devices to carry massive amounts of data, greatly enriching the possibilities of modern digital life. More importantly, miniaturization often complements performance leaps; by reducing the size of storage cells, more storage cells can be integrated onto the same chip area. This not only significantly increases storage density and capacity but also reduces cell power consumption and accelerates read and write speeds, thereby meeting the demanding requirements of cutting-edge technologies such as artificial intelligence and big data for high-speed, high-capacity storage.

[0003] Rutile TiO2 is a wide bandgap semiconductor material. It can achieve excellent giant dielectric properties by co-doping with acceptor and donor ions. If magnetic elements are used as acceptor ions, materials that combine room-temperature ferromagnetism and giant dielectric properties can be obtained.

[0004] Furthermore, material anisotropy has transformed from a material property that needed to be avoided into a core design dimension for achieving high performance, multifunctionality, and miniaturization of electronic components. By precisely controlling the matching relationship between the direction of current, electromagnetic field, or mechanical stress and lattice orientation, device performance can be optimized in a specific direction—such as achieving higher carrier mobility in a specific crystal orientation to increase transistor speed, or utilizing the directional difference in dielectric constant to construct higher-capacity microcapacitors. This direction-dependent characteristic is not only the foundation for the working principles of functional devices such as piezoelectric sensors, spin memories, and liquid crystal displays, but also drives the development of components towards a new paradigm that transcends the traditional silicon-based framework. Therefore, developing rutile single-crystal materials with magneto-electric anisotropy to improve the performance of memory devices is imperative. Summary of the Invention

[0005] In view of this, the present invention provides a rutile single crystal material with magnetic-electric anisotropy and its preparation method. The method uses flame fusion to prepare Nb and Co co-doped rutile single crystals to obtain a rutile single crystal material with magnetic-electric anisotropy.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for preparing a rutile single crystal material with magnetic-electric anisotropy includes the following steps:

[0008] (1) Using TiO2, Nb2O5 and CoO as starting materials, weigh the raw materials according to the chemical formula (Nb ,

[0015] Co 1 / 3 ) x Ti 1-x O2 (0 < x ≤ 2%), and then put the weighed raw materials into a ball mill for ball milling;

[0009] Preferably, the ball milling method is wet ball milling, the ball milling solvent is deionized water, the dispersant is ammonium polyacrylate with a mass concentration of 0.1% - 0.5%, the mass of the dispersant is 0.05% -​​​​​​​​​​​​​​​​​Preferably, the annealing method is full annealing, and the annealing process is as follows: raise the temperature to 550℃~650℃ at 2℃ / min~3℃ / min and hold for 22h~26h; raise the temperature to 750℃~850℃ at 1℃ / min~2℃ / min and hold for 22h~26h; raise the temperature to 950℃~1050℃ at 1℃ / min~2℃ / min and hold for 22h~26h; and lower the temperature to room temperature at 1℃ / min~2℃ / min.

[0016] (5) Oriented cutting of fully annealed single crystals to obtain wafers with different orientations;

[0017] Preferably, during directional cutting, the cutting is first performed along the direction perpendicular to the crystal growth direction, and the (002) orientation crystal plane is finely positioned by using a directional diffractometer. Then, the (220) orientation is searched perpendicular to this crystal plane.

[0018] A second aspect of the present invention provides a rutile single crystal material with magneto-electric anisotropy, which is prepared by the above method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention uses Nb and Co as doping elements and employs a flame fusion method to prepare high-quality, large-size (Nb)₂O₃ ... 2 / 3 Co 1 / 3 ) x Ti 1-x O2 single crystal, through Nb 5+ With Co 2+ Co-doping with rutile results in the formation of ordered defect dipoles in the crystal, which can induce room-temperature ferromagnetism and giant dielectric properties. At the same time, due to the anisotropy of the rutile structure and the directional arrangement of defect dipoles during growth on different crystal planes, the single crystal acquires different ferromagnetic and giant dielectric properties in different crystal orientations. This allows for the optimization of device performance through magneto-electric anisotropy—such as achieving higher carrier mobility in specific crystal orientations to improve transistor speed, or utilizing the directional differences in dielectric constant to construct higher-capacity microcapacitors, thus driving the development of devices towards a new paradigm that transcends the traditional silicon-based framework. Attached Figure Description

[0021] Figure 1 In Example 1 (Nb) 2 / 3 Co 1 / 3 ) 1% Ti 99% XRD results of O2 single crystal; where (a) is the result of full annealing (Nb) 2 / 3 Co 1 / 3 ) 1% Ti 99% XRD patterns of O2 single crystals with (002) crystal plane orientation, (b) is (Nb)2 / 3 Co 1 / 3 ) 1% Ti 99% XRD pattern of O2 single crystal (220) crystal orientation;

[0022] Figure 2 In Example 1 (Nb) 2 / 3 Co 1 / 3 ) 1% Ti 99% Dielectric properties of O2 single crystal in different orientations; where (a) is the graph of dielectric constant versus frequency at room temperature, and (b) is the graph of dielectric loss versus frequency at room temperature.

[0023] Figure 3 In Example 1 (Nb) 2 / 3 Co 1 / 3 ) 1% Ti 99% Room temperature ferromagnetism of O2 single crystals in different orientations;

[0024] Figure 4 In Example 1 (Nb) 2 / 3 Co 1 / 3 ) 1% Ti 99% O2 single crystal rocking curve;

[0025] Figure 5 The dielectric properties of pure TiO2 single crystal in Comparative Example 3 are shown; where (a) is the graph of dielectric constant versus frequency at room temperature, and (b) is the graph of dielectric loss versus frequency at room temperature.

[0026] Figure 6 The room temperature ferromagnetism of pure TiO2 single crystal in Comparative Example 3 is shown. Detailed Implementation

[0027] This invention provides a method for preparing a rutile single crystal material with magnetic-electric anisotropy, comprising the following steps:

[0028] (1) Using TiO2, Nb2O5 and CoO as starting materials, according to the chemical formula (Nb 2 / 3 Co 1 / 3 ) x Ti 1-xWeigh the raw materials using O2 (0 < x ≤ 2%), and then place the weighed raw materials into a ball mill jar for ball milling. During ball milling, deionized water is used as the solvent, zirconia grinding balls are used as the medium, and ammonium polyacrylate with a mass concentration of 0.1% to 0.5% is used as the dispersant. The mass of the dispersant is 0.05% to 0.1% of the total mass of the starting raw materials, the mass ratio of grinding balls to starting raw materials is (2~3):1, and the mass ratio of liquid medium (composed of deionized water and ammonium polyacrylate) to starting raw materials is (2~3):1. Wet ball milling is carried out at a speed of 150 rpm to 250 rpm for 10 h to 14 h to obtain the ball-milled powder.

[0029] (2) The ball-milled powder is placed in an oven and dried at 100℃~120℃ for 10h~12h. Then the dried powder is placed in an alumina crucible and heated to 1200℃~1400℃ at a rate of 4℃ / min~6℃ / min. The powder is calcined for 22h~26h to obtain synthetic powder. The calcined powder is crushed and passed through a 180-220 mesh sieve to obtain the original doped powder for flame melting growth.

[0030] (3) A three-tube burner was used to grow single crystals by flame melting. The initial internal oxygen flow rate was controlled at 5L / min~6L / min, the external oxygen flow rate at 3L / min~4.5L / min, and the hydrogen flow rate at 10L / min~12L / min for furnace drying. First, hydrogen was introduced into the growth chamber and ignited to produce an open flame. Then, internal oxygen was introduced into the growth chamber. After the flame stabilized, external oxygen was introduced into the growth chamber. After the furnace drying was completed, a seed crystal with orientation (002) was placed at the window position of the growth chamber. Then, the hydrogen flow rate was increased at a rate of 0.1L / 5min~0.1L / 3min. After the seed crystal melted, the feeding device was turned on and the material was fed at a rate of 80r / min~120r / min. The hydrogen flow rate was continuously increased at the same rate to 13L / min~15L / min so that the crystal could grow at a rate of 5mm / h~8mm / h to complete the shoulder expansion growth. Finally, the gas flow rate was kept constant and the feeding speed of the feeding system was controlled until the constant diameter growth was completed.

[0031] (4) After the grown crystals have cooled to room temperature, they are subjected to complete annealing treatment according to a specific process: 2℃ / min~3℃ / min to 550℃~650℃, hold for 22h~26h; 1℃ / min~2℃ / min to 750℃~850℃, hold for 22h~26h; 1℃ / min~2℃ / min to 950℃~1050℃, hold for 22h~26h; 1℃ / min~2℃ / min to room temperature.

[0032] (5) The fully annealed single crystal is oriented to obtain wafers with different orientations.

[0033] In the method provided by the present invention, during directional cutting, the cutting is first performed along the direction perpendicular to the crystal growth direction, and the (002) orientation crystal plane is finely positioned by using a directional diffractometer. Then, the (220) orientation is searched perpendicular to the crystal plane.

[0034] The present invention also provides a rutile single crystal material with magneto-electric anisotropy, which is prepared by the above method.

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0036] Example 1:

[0037] This embodiment provides a method for preparing a rutile single crystal material that combines giant dielectric properties and room-temperature ferromagnetism, comprising the following steps:

[0038] Step 1: Using TiO2 (99.99% purity), Nb2O5 (99.99% purity), and CoO (99.99% purity) as starting materials, according to the chemical formula (Nb... 2 / 3 Co 1 / 3 ) 1% Ti 99% O2 was used to weigh out the raw materials, with a total mass of 200g. The weighed raw materials were then placed in a polytetrafluoroethylene ball mill jar for wet ball milling. During the ball milling process, deionized water was used as the solvent, zirconia grinding balls as the medium, and 0.3% ammonium polyacrylate as the dispersant. The mass ratio of grinding balls to starting materials was 2:1, the mass ratio of liquid medium to starting materials was 2.5:1, and the mass of dispersant was 0.05% of the total mass of starting materials. The mixture was ball milled at 200 rpm for 12 hours to obtain the ball-milled powder.

[0039] Step 2: The ball-milled powder is dried in a 120℃ oven for 12 hours. Then, the dried powder is placed in an alumina crucible and calcined at a rate of 5℃ / min to 1300℃ and held for 24 hours to obtain the synthetic powder. The calcined powder is crushed and passed through a 200-mesh sieve to obtain the original doped powder for flame melting growth.

[0040] Step 3: Using a three-tube burner, single crystals are grown by flame melting with the original doped powder. Oxygen (inner oxygen), hydrogen, and oxygen (outer oxygen) are introduced sequentially from the inside to the outside. First, hydrogen is introduced into the growth chamber at a flow rate of 10 L / min. After ignition and the appearance of an open flame, inner oxygen is introduced into the growth chamber at a flow rate of 5 L / min. After the flame stabilizes, outer oxygen is introduced into the growth chamber at a flow rate of 3 L / min for furnace drying. After the furnace drying is completed, the (002) oriented seed crystal is placed at the window position of the growth chamber. Then, the hydrogen flow rate is increased at a rate of 0.1 L / 4 min. After the seed crystal melts, the feeding device is turned on and the material is fed at a rate of 80 r / min to 120 r / min. The hydrogen flow rate is continuously increased at a rate of 0.1 L / 4 min to 14 L / min to complete the shoulder expansion growth. The feeding speed of the feeding system is controlled to make the crystal growth rate 5 mm / h to 8 mm / h. Finally, the gas flow rate and feeding speed are kept constant until the constant diameter growth is completed.

[0041] Step 4: After the crystal grown in Step 3 has cooled to room temperature, the crystal is fully annealed according to a specific process: the temperature is increased to 600℃ at a rate of 2℃ / min and held for 24h; the temperature is increased to 800℃ at a rate of 1℃ / min and held for 24h; the temperature is increased to 1000℃ at a rate of 1℃ / min and held for 24h; finally, the temperature is reduced to room temperature at a rate of 1℃ / min.

[0042] Step 5: Oriented cutting of the fully annealed single crystal in Step 4: First, cut along the direction perpendicular to the crystal growth direction, finely adjust and position the (002) orientation crystal plane using an orientation diffractometer, and then search for orientation perpendicular to this crystal plane.

[0043] The (Nb) prepared in this embodiment 2 / 3 Co 1 / 3 ) 1% Ti 99% The O2 crystal was characterized by XRD, and the results are as follows: Figure 1 As shown. XRD results show that the obtained crystal has a pure phase rutile structure, and the diffraction peaks of the (002) and (220) orientations are sharp, indicating that the crystal has high crystal quality and clear orientation.

[0044] The (Nb) prepared in this embodiment 2 / 3 Co 1 / 3 ) 1% Ti 99% The dielectric properties of O2 single crystals in different orientations were characterized, and the results are as follows: Figure 2 As shown. Figure 2 The results show that the obtained single-crystal materials exhibit giant dielectric constants (>10) in both the (002) and (220) directions. 4 However, there are significant differences between the specific values ​​and the frequency variation, confirming dielectric anisotropy.

[0045] The (Nb) prepared in this embodiment 2 / 3 Co 1 / 3 ) 1% Ti 99% The room-temperature ferromagnetism of O2 single crystals in different orientations was characterized according to a period of magnetic field strength from 0 to 20000 Oe to -20000 Oe and back to 0. The results are as follows: Figure 3 As shown. Figure 3 The results show that the material prepared in this embodiment exhibits significant ferromagnetism in both directions, but there is a significant difference between the saturation magnetization and coercivity, which proves magnetic anisotropy.

[0046] The (Nb) prepared in this embodiment 2 / 3 Co 1 / 3 ) 1% Ti 99% The full width at half maximum (FWHM) of the O2 single crystal was characterized, and the results are as follows: Figure 4 As shown. Figure 4 The results show that the half-width at half-maximum (FWHM) of the grown single crystal is 0.0635°, which is relatively narrow, indicating that the orientation of the (002) crystal plane is very consistent and the crystal quality is excellent.

[0047] Example 2:

[0048] This embodiment provides a method for preparing a rutile single crystal material that combines giant dielectric properties and room-temperature ferromagnetism, comprising the following steps:

[0049] Step 1: Using TiO2 (99.99% purity), Nb2O5 (99.99% purity), and CoO (99.99% purity) as starting materials, according to the chemical formula (Nb... 2 / 3 Co 1 / 3 ) 1% Ti 99% O2 was used to weigh out the raw materials, with a total mass of 200g. The weighed raw materials were then placed in a polytetrafluoroethylene ball mill jar for wet ball milling. During the ball milling process, deionized water was used as the solvent, zirconia grinding balls as the medium, and 0.3% ammonium polyacrylate as the dispersant. The mass ratio of grinding balls to starting materials was 3:1, the mass ratio of liquid medium to starting materials was 3:1, and the mass of dispersant was 0.1% of the total mass of starting materials. The mixture was ball milled at 150 rpm for 14 hours to obtain the ball-milled powder.

[0050] Step 2: Place the ball-milled powder in a 100℃ oven and dry for 10 hours. Then, place the dried powder in an alumina crucible and calcine it at a rate of 4℃ / min to 1200℃ and hold for 26 hours to obtain the synthetic powder. The calcined powder is crushed and passed through a 200-mesh sieve to obtain the original doped powder for flame melting growth.

[0051] Step 3: Using a three-tube burner, single crystals are grown by flame melting with the original doped powder. Oxygen (inner oxygen), hydrogen, and oxygen (outer oxygen) are introduced sequentially from the inside to the outside. First, hydrogen is introduced into the growth chamber at a flow rate of 12 L / min. After ignition and the appearance of an open flame, inner oxygen is introduced into the growth chamber at a flow rate of 6 L / min. After the flame stabilizes, outer oxygen is introduced into the growth chamber at a flow rate of 4.5 L / min for furnace drying. After furnace drying, the (002)-oriented seed crystal is placed at the window position of the growth chamber. Then, the hydrogen flow rate is increased at a rate of 0.1 L / 3 min. After the seed crystal melts, the feeding device is turned on and the material is fed at a rate of 80 r / min to 120 r / min. The hydrogen flow rate is continuously increased at a rate of 0.1 L / 3 min to 15 L / min to complete the shoulder expansion growth. The feeding speed of the feeding system is controlled to make the crystal growth rate 5 mm / h to 8 mm / h. Finally, the gas flow rate and feeding speed are kept constant until the constant diameter growth is completed.

[0052] Step 4: After the crystal grown in Step 3 has cooled to room temperature, the crystal is fully annealed according to a specific process: the temperature is increased to 650°C at a rate of 3°C / min and held for 24 hours; the temperature is increased to 850°C at a rate of 2°C / min and held for 24 hours; the temperature is increased to 1050°C at a rate of 2°C / min and held for 24 hours; finally, the temperature is reduced to room temperature at a rate of 2°C / min.

[0053] Step 5: Oriented cutting of the single crystal that has been fully annealed in Step 4: First, cut along the direction perpendicular to the crystal growth direction, finely adjust and position the (002) orientation crystal plane using an orientation diffractometer, and then search for the (220) orientation perpendicular to this crystal plane.

[0054] Example 3:

[0055] This embodiment provides a method for preparing a rutile single crystal material that combines giant dielectric properties and room-temperature ferromagnetism, comprising the following steps:

[0056] Step 1: Using TiO2 (99.99% purity), Nb2O5 (99.99% purity), and CoO (99.99% purity) as starting materials, according to the chemical formula (Nb... 2 / 3 Co 1 / 3 ) 1% Ti 99% O2 was used to weigh out the raw materials, with a total mass of 200g. The weighed raw materials were then placed in a polytetrafluoroethylene ball mill jar for wet ball milling. During the ball milling process, deionized water was used as the solvent, zirconia grinding balls as the medium, and 0.3% ammonium polyacrylate as the dispersant. The mass ratio of grinding balls to starting materials was 2.5:1, the mass ratio of liquid medium to starting materials was 2:1, and the mass of dispersant was 0.05% of the total mass of starting materials. The mixture was ball-milled at 250 rpm for 10 hours to obtain the ball-milled powder.

[0057] Step 2: The ball-milled powder was dried in a 110℃ oven for 11 hours. Then the dried powder was placed in an alumina crucible and calcined at a rate of 6℃ / min to 1400℃ and held for 22 hours to obtain the synthetic powder. The calcined powder was crushed and passed through a 200-mesh sieve to obtain the original doped powder for flame melting growth.

[0058] Step 3: Using a three-tube burner, single crystals are grown by flame melting with the original doped powder. Oxygen (inner oxygen), hydrogen, and oxygen (outer oxygen) are introduced sequentially from the inside to the outside. First, hydrogen is introduced into the growth chamber at a flow rate of 11 L / min. After ignition and the appearance of an open flame, inner oxygen is introduced into the growth chamber at a flow rate of 5.5 L / min. After the flame stabilizes, outer oxygen is introduced into the growth chamber at a flow rate of 4 L / min for furnace drying. After furnace drying, the (002)-oriented seed crystal is placed at the window position of the growth chamber. Then, the hydrogen flow rate is increased at a rate of 0.1 L / 5 min. After the seed crystal melts, the feeding device is turned on and the material is fed at a rate of 80 r / min to 120 r / min. The hydrogen flow rate is continuously increased at a rate of 0.1 L / 5 min to 13 L / min to complete the shoulder expansion growth. The feeding speed of the feeding system is controlled to make the crystal growth rate 5 mm / h to 8 mm / h. Finally, the gas flow rate and feeding speed are kept constant until the constant diameter growth is completed.

[0059] Step 4: After the crystal grown in Step 3 has cooled to room temperature, the crystal is fully annealed according to a specific process: the temperature is increased to 550℃ at a rate of 2.5℃ / min and held for 24 hours; the temperature is increased to 750℃ at a rate of 1.5℃ / min and held for 24 hours; the temperature is increased to 950℃ at a rate of 1℃ / min and held for 24 hours; finally, the temperature is reduced to room temperature at a rate of 1.5℃ / min.

[0060] Step 5: Oriented cutting of the single crystal that has been fully annealed in Step 4: First, cut along the direction perpendicular to the crystal growth direction, finely adjust and position the (002) orientation crystal plane using an orientation diffractometer, and then search for the (220) orientation perpendicular to this crystal plane.

[0061] Comparative Example 1:

[0062] This comparative example provides a method for preparing rutile single crystal material, which is basically the same as that in Example 1, except that the hydrogen flow rate increase rate and the final hydrogen flow rate are different in step 3. Specifically, it includes the following steps:

[0063] Step 1: Using TiO2 (99.99% purity), Nb2O5 (99.99% purity), and CoO (99.99% purity) as starting materials, according to the chemical formula (Nb... 2 / 3 Co 1 / 3 ) 1% Ti 99%O2 weighed the raw materials, with a total mass of 200g. The weighed raw materials were then placed in a polytetrafluoroethylene ball mill jar for wet ball milling. During the ball milling process, deionized water was used as the solvent, zirconia grinding balls were used as the medium, and 0.3% ammonium polyacrylate was used as the dispersant. The mass ratio of grinding balls to starting raw materials was 2:1, the mass ratio of liquid medium to starting raw materials was 2.5:1, and the mass of dispersant was 0.05% of the total mass of starting raw materials. The mixture was ball milled at 200 rpm for 12 hours to obtain the ball-milled powder.

[0064] Step 2: The ball-milled powder is dried in a 120℃ oven for 12 hours. Then, the dried powder is placed in an alumina crucible and calcined at a rate of 5℃ / min to 1300℃ and held for 24 hours to obtain the synthetic powder. The calcined powder is crushed and passed through a 200-mesh sieve to obtain the original doped powder for flame melting growth.

[0065] Step 3: Using a three-tube burner, single crystals are grown by flame fusion with the original doped powder. Oxygen (inner oxygen), hydrogen, and oxygen (outer oxygen) are introduced sequentially from the inside to the outside. First, hydrogen is introduced into the growth chamber at a flow rate of 10 L / min. After ignition and the appearance of an open flame, inner oxygen is introduced into the growth chamber at a flow rate of 5 L / min. After the flame stabilizes, outer oxygen is introduced into the growth chamber at a flow rate of 3 L / min for furnace drying. After furnace drying, the (002) oriented seed crystal is placed at the window position of the growth chamber. Then, the hydrogen flow rate is increased at a rate of 0.1 L / 6 min. After the seed crystal melts, the feeding device is turned on, and the material is fed at a rate of 80 r / min to 120 r / min. The hydrogen flow rate is continuously increased at a rate of 0.1 L / 6 min to 15 L / min to complete the shoulder expansion growth. The feeding speed of the feeding system is controlled to keep the crystal growth rate at 5 mm / h to 8 mm / h. Finally, the gas flow rate and feeding speed are kept constant to maintain constant diameter growth.

[0066] Because the hydrogen growth rate was too slow, the shoulder expansion rate was too slow, causing the crystal to remain in the high-temperature region for too long. After 30 minutes of constant diameter growth, the melt overflowed, and the experiment had to be terminated, indicating that the process could not achieve crystal growth.

[0067] Comparative Example 2:

[0068] This comparative example provides a method for preparing rutile single crystal material, which is basically the same as that in Example 1, except that the hydrogen flow rate increase rate and the final hydrogen flow rate are different in step 3. Specifically, it includes the following steps:

[0069] Step 1: Using TiO2 (99.99% purity), Nb2O5 (99.99% purity), and CoO (99.99% purity) as starting materials, according to the chemical formula (Nb... 2 / 3 Co 1 / 3 ) 1% Ti99% O2 was used to weigh out the raw materials, with a total mass of 200g. The weighed raw materials were then placed in a polytetrafluoroethylene ball mill jar for wet ball milling. During the ball milling process, deionized water was used as the solvent, zirconia grinding balls as the medium, and 0.3% ammonium polyacrylate as the dispersant. The mass ratio of grinding balls to starting materials was 2:1, the mass ratio of liquid medium to starting materials was 2.5:1, and the mass of dispersant was 0.05% of the total mass of starting materials. The mixture was ball-milled at 200 rpm for 12 hours to obtain the ball-milled powder.

[0070] Step 2: The ball-milled powder is dried in a 120℃ oven for 12 hours. Then, the dried powder is placed in an alumina crucible and calcined at a rate of 5℃ / min to 1300℃ and held for 24 hours to obtain the synthetic powder. The calcined powder is crushed and passed through a 200-mesh sieve to obtain the original doped powder for flame melting growth.

[0071] Step 3: Using a three-tube burner, single crystals are grown by flame fusion with the original doped powder. Oxygen (inner oxygen), hydrogen, and oxygen (outer oxygen) are introduced sequentially from the inside to the outside. First, hydrogen is introduced into the growth chamber at a flow rate of 10 L / min. After ignition and the appearance of an open flame, inner oxygen is introduced into the growth chamber at a flow rate of 5 L / min. After the flame stabilizes, outer oxygen is introduced into the growth chamber at a flow rate of 3 L / min for furnace drying. After furnace drying, the (002) oriented seed crystal is placed at the window position of the growth chamber. Then, the hydrogen flow rate is increased to 13 L / min at a rate of 0.1 L / 2 min. After the seed crystal melts, the feeding device is turned on, and the material is fed at a rate of 80 r / min to 120 r / min. The hydrogen flow rate is continuously increased at a rate of 0.1 L / 2 min to achieve shoulder expansion growth.

[0072] Because the hydrogen growth rate was too fast and the melt was too saturated, the crystal overflowed during the shoulder expansion process, forcing the experiment to be terminated, indicating that the process could not achieve crystal growth.

[0073] Comparative Example 3:

[0074] This comparative example provides a method for preparing rutile single crystal material, including the following steps:

[0075] Step 1: TiO2 (purity 99.99%) was placed in an alumina crucible and calcined. The temperature was increased to 1400℃ at a rate of 6℃ / min and held for 22h to obtain synthetic powder. The calcined powder was crushed and passed through a 200-mesh sieve to obtain the original doped powder for flame fusion growth.

[0076] Step 2: Using a three-tube burner, single crystals are grown by flame melting with the original doped powder. Oxygen (inner oxygen), hydrogen, and oxygen (outer oxygen) are introduced sequentially from the inside to the outside. First, hydrogen is introduced into the growth chamber at a flow rate of 11 L / min. After ignition and the appearance of an open flame, inner oxygen is introduced into the growth chamber at a flow rate of 5.5 L / min. After the flame stabilizes, outer oxygen is introduced into the growth chamber at a flow rate of 4 L / min for furnace drying. After furnace drying, the (002) oriented seed crystal is placed at the window position of the growth chamber. Then, the hydrogen flow rate is increased at a rate of 0.1 L / 5 min. After the seed crystal melts, the feeding device is turned on and the material is fed at a rate of 80 r / min to 120 r / min. The hydrogen flow rate is continuously increased at a rate of 0.1 L / 4 min to 13 L / min to complete the shoulder expansion growth. The feeding speed of the feeding system is controlled to make the crystal growth rate 5 mm / h to 8 mm / h. Finally, the gas flow rate and feeding speed are kept constant until the constant diameter growth is completed.

[0077] Step 3: After the crystal grown in Step 2 has cooled to room temperature, the crystal is fully annealed according to a specific process: the temperature is increased to 550℃ at a rate of 2.5℃ / min and held for 24 hours; the temperature is increased to 750℃ at a rate of 1.5℃ / min and held for 24 hours; the temperature is increased to 950℃ at a rate of 1℃ / min and held for 24 hours; finally, the temperature is reduced to room temperature at a rate of 1.5℃ / min.

[0078] Step 4: Oriented cutting of the fully annealed single crystal in Step 3: Cut along the direction perpendicular to the crystal growth direction and finely adjust the positioning of the (002) orientation crystal plane using an orientation diffractometer.

[0079] The dielectric and magnetic properties of the wafers obtained in this comparative example were tested. Figure 5 It refers to its dielectric properties at room temperature. The dielectric constant of undoped rutile single crystal is only about 200, and it does not achieve giant dielectric properties. Figure 6 Its room temperature ferromagnetism is due to the fact that undoped rutile single crystals exhibit paramagnetism and do not acquire ferromagnetism.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a rutile single crystal material with magneto-electric anisotropy, characterized in that, Includes the following steps: S1. Using TiO2, Nb2O5, and CoO as starting materials, according to the chemical formula (Nb... 2 / 3 Co 1 / 3 ) x Ti 1-x O2 is used to weigh the raw materials, which are then placed in a ball mill jar for ball milling to obtain the ball-milled powder; wherein, 0 <x≤2%; S2. After drying the ball-milled powder, calcination is carried out to obtain synthetic powder. The synthetic powder is then crushed and sieved to obtain the original doped powder. S3. Single crystals are grown using the flame melting method. The flow rates of hydrogen and oxygen are controlled during furnace baking. After the furnace baking is completed, the seed crystal is placed at the window of the growth chamber. Then, the flow rate of hydrogen is increased. After the seed crystal melts, the original doping powder is added. The feeding device is turned on to feed the material. The flow rate of hydrogen is continuously increased to complete the shoulder expansion growth. Finally, the gas flow rate and feeding speed are kept constant until the crystal grows to the target size, thus completing the constant diameter growth. The oxygen includes internal oxygen and external oxygen. The orientation of the seed crystal is (002). S4. After the grown single crystal has cooled to room temperature, it is annealed. S5. The annealed single crystal is oriented and cut to obtain wafers with different orientations; In S3, when a single crystal is grown by flame melting using a three-tube burner, internal oxygen, hydrogen, and external oxygen are introduced from the inside to the outside of the three-tube burner, respectively. When increasing the hydrogen flow rate, increase it at a rate of 0.1L / 5min to 0.1L / 3min until it reaches 13L / min to 15L / min; In S4, the annealing treatment is a full annealing treatment; the annealing process is as follows: heat up to 550℃~650℃ at 2℃ / min~3℃ / min, hold for 22h~26h; heat up to 750℃~850℃ at 1℃ / min~2℃ / min, hold for 22h~26h; heat up to 950℃~1050℃ at 1℃ / min~2℃ / min, hold for 22h~26h; cool down to room temperature at 1℃ / min~2℃ / min. In S5, during directional cutting, the cutting is first performed along the direction perpendicular to the crystal growth direction. The (002) orientation crystal plane is then finely positioned using a directional diffractometer, and then the (220) orientation is searched perpendicular to this crystal plane.

2. The method for preparing a rutile single crystal material with magneto-electric anisotropy according to claim 1, characterized in that, In S3, during furnace baking, the internal oxygen flow rate is controlled at 5L / min~6L / min, the external oxygen flow rate is controlled at 3L / min~4.5L / min, and the hydrogen flow rate is controlled at 10L / min~12L / min.

3. The method for preparing a rutile single crystal material with magneto-electric anisotropy according to claim 2, characterized in that, The feeding speed is 80r / min~120r / min, and the crystal growth speed is 5mm / h~8mm / h.

4. The method for preparing a rutile single crystal material with magneto-electric anisotropy according to claim 1, characterized in that, In S1, wet ball milling is performed using ball milling solvent and dispersant as liquid media. The ball milling speed is 150 rpm to 250 rpm, and the ball milling time is 10 h to 14 h; The mass of the dispersant is 0.05% to 0.1% of the total mass of the starting raw materials, the mass ratio of the grinding balls to the starting raw materials is (2 to 3):1, and the mass ratio of the total mass of the liquid medium to the starting raw materials is (2 to 3):

1.

5. The method for preparing a rutile single crystal material with magneto-electric anisotropy according to claim 4, characterized in that, The dispersant is ammonium polyacrylate with a mass concentration of 0.1%~0.5%, and the ball milling solvent is deionized water.

6. The method for preparing a rutile single crystal material with magneto-electric anisotropy according to claim 1, characterized in that, In S2, the drying temperature is 100℃~120℃, and the drying time is 10h~12h; During calcination, the temperature is increased to 1200℃~1400℃ at a rate of 4℃ / min~6℃ / min and calcined for 22h~26h. The sieve is a 180-220 mesh sieve.

7. A rutile single crystal material with magneto-electric anisotropy, prepared by the method described in any one of claims 1 to 6.

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