High-pressure oxygen atmosphere annealing device and process for yttrium iron garnet crystals

Abstract

The invention provides a high-pressure oxygen atmosphere annealing device and process for yttrium iron garnet crystals, and the high-pressure oxygen atmosphere annealing device for the yttrium iron garnet crystals comprises a heating furnace, a high-pressure reaction cavity, a homogeneous ceramic sample cavity homogeneous with the yttrium iron garnet crystals, an oxygen supply system and a vacuum pipeline, the invention relates to a high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystals. The high-pressure oxygen atmosphere annealing process comprises the following steps: pretreatment: placing the yttrium iron garnet crystals in a homogeneous ceramic sample cavity; oxygenating and pressurizing; heating and annealing: operating the heating furnace, heating the interior of the high-pressure reaction cavity to 1000-1200 DEG C at the speed of 50-100 DEG C / h, and keeping the temperature constant for 2-10 hours; gradient cooling; and releasing pressure and taking materials. According to the invention, the problems of low annealing efficiency and limited photomagnetic performance caused by insufficient pressure in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field related to annealing of yttrium iron garnet crystals, and in particular to a high-pressure oxygen atmosphere annealing device and process for yttrium iron garnet crystals. Background Art

[0002] Traditional oxygen atmosphere annealing techniques typically utilize an atmospheric or low-pressure (<1.2 atm) oxygen environment. Typical equipment includes a quartz tube, a heating unit, and an oxygen supply system. For example, patent CN101148753A proposes the preparation of YIG thin films using microwave annealing combined with sputtering, but does not address high-pressure conditions. Prior art discloses a pure oxygen annealing apparatus that utilizes a quartz tube and a PID temperature controller to achieve oxygen atmosphere annealing. However, the pressure range is limited to atmospheric pressure to 1.2 atm, limiting annealing efficiency and ineffective in eliminating deep-seated oxygen vacancies.

[0003] The defects of the existing technology are: because traditional devices cannot withstand high pressure, the pressure during annealing is insufficient, making it difficult for low-pressure oxygen to penetrate the interior of the yttrium iron garnet crystal, and oxygen vacancy repair is not complete, affecting optical uniformity and magnetic properties. Insufficient pressure also requires long-term high-temperature treatment during annealing (such as 24-72 hours), resulting in low annealing efficiency, high energy consumption, and easy introduction of impurity contamination. Summary of the Invention

[0004] The present invention aims to provide a high-pressure oxygen atmosphere annealing device and process for yttrium iron garnet crystals, so as to solve the problems of low annealing efficiency and limited optical and magnetic properties caused by insufficient pressure.

[0005] To this end, the technical solution adopted by the present invention is: a high-pressure oxygen atmosphere annealing device for yttrium iron garnet crystals, comprising a heating furnace, a high-pressure reaction chamber, a homogeneous ceramic sample chamber homogeneous with the yttrium iron garnet crystals, an oxygen supply system and a vacuum pipeline; the high-pressure reaction chamber is installed in the heating furnace, and the heating furnace is provided with a preheating zone, a reaction zone and a slow cooling zone, the high-pressure reaction chamber runs through the preheating zone, the reaction zone and the slow cooling zone, and the homogeneous ceramic sample chamber is placed in the high-pressure reaction chamber; the oxygen supply system comprises a high-pressure oxygen cylinder, an oxygen supply pipeline, a precision pressure reducing valve and a flow controller, the oxygen supply pipeline is connected to the high-pressure oxygen cylinder, the precision pressure reducing valve and the flow controller, and is connected to the high-pressure reaction chamber so as to supply high-pressure oxygen to the high-pressure reaction chamber; the vacuum pipeline connects a vacuum pump and the high-pressure reaction chamber.

[0006] As a preferred embodiment of the above solution, a pressure relief valve and a pressure sensor are connected to the vacuum pipeline.

[0007] Further preferably, the oxygen supply pipeline and the vacuum pipeline are both connected to the high-pressure reaction chamber through a high-temperature alloy flange.

[0008] A high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystals comprises the following steps:

[0009] S1, pretreatment, placing the yttrium iron garnet crystal in a homogeneous ceramic sample cavity to avoid reaction with the cavity material of the high-pressure reaction cavity at high temperature;

[0010] S2, oxygenation and pressurization: start the vacuum pump, evacuate the high-pressure reaction chamber through the vacuum pipeline, then open the high-pressure oxygen cylinder, and pass oxygen from the high-pressure oxygen cylinder into the high-pressure reaction chamber through the oxygen supply pipeline. The precision pressure reducing valve and flow controller are operated to increase the pressure at a gradient of 0.5 MPa / min to raise the oxygen pressure to a target value of 5-20 MPa;

[0011] S3, heating annealing, operating the heating furnace to raise the temperature in the high-pressure reaction chamber to 1000-1200° C. at a rate of 50-100° C. / h, and maintaining the temperature for 2-10 hours;

[0012] S4, gradient cooling, operating the heating furnace to cool the high-pressure reaction chamber to below 200°C at a rate of ≤50°C / h, and then naturally cooling to room temperature;

[0013] S5, releasing the pressure and taking out the material, closing the high-pressure oxygen cylinder and the vacuum pump, operating the precision pressure reducing valve to slowly release the pressure, and taking out the crystals after the pressure in the high-pressure reaction chamber drops to normal pressure.

[0014] As a preferred embodiment of the above scheme, the high-pressure atmosphere in the high-pressure reaction chamber is controlled by coupling the oxygen atmosphere with gradient pressure increase and constant pressure, and the oxygen partial pressure is dynamically adjusted during the annealing process: in the initial stage, the pressure is increased from 0.1 MPa to 10 MPa by the gradient pressure increase method to promote the migration of lattice oxygen vacancies, in the middle stage, the constant pressure of 10 MPa is used to stabilize the diffusion of filling oxygen, and in the later stage, the gradient pressure reduction method is used to reduce the pressure from 10 MPa to 0.1 MPa to suppress crystal stress cracks. The coordinated optimization of oxygen defect repair and crystal integrity is achieved through pressure timing control.

[0015] Further preferably, an optical fiber head is fixedly installed in the oxygen inlet end of the high-pressure reaction chamber, and the optical fiber head is connected to a laser; in the step S3, pulsed oxygen free radical assisted annealing is adopted, the laser is started, and the laser is emitted through the optical fiber head, so that intermittent ultraviolet light excitation with a wavelength of 172nm / 185nm / 193nm / 254nm is introduced into the high-pressure oxygen environment in the high-pressure reaction chamber, so that O2 is decomposed into highly active oxygen free radicals, which react with Fe on the surface of the yttrium iron garnet crystal. 2+ Defective sites are selectively oxidized to Fe 3+At the same time, the reaction depth is controlled by a pulse cycle of 10s on / 30s off, which improves the uniformity of the lattice redox reaction and significantly reduces optical scattering loss.

[0016] More preferably, in step S3, the heating furnace is heated by a multi-segment resistance wire, combined with a PID temperature controller with an accuracy of ±0.1°C and a thermocouple for real-time monitoring.

[0017] It is further preferred that the temperature of the preheating zone is 300-700°C, the temperature of the reaction zone is 700-1000°C, the temperature of the slow cooling zone is 500-700°C, and the heating furnace is a three-temperature zone tubular furnace, which cooperates with the axial vortex oxygen flow field, uses the temperature difference to drive the directional diffusion of oxygen ions, forms an oxygen concentration gradient in the preheating zone, realizes rapid bulk doping in the reaction zone, and eliminates grain boundary stress through oxygen flow vortex in the slow cooling zone, thereby improving the crystal magneto-optical figure of merit and the consistency of annealing batch performance.

[0018] Beneficial effects of the present invention:

[0019] 1. The present invention can achieve high-pressure annealing of yttrium iron garnet crystals. Under high-pressure oxygen (20 MPa), the oxygen ion diffusion rate is increased by 3-5 times, and the annealing time is shortened to 1 / 3 of the traditional method, thereby improving the annealing efficiency of yttrium iron garnet crystals.

[0020] 2. Under high-pressure oxygen environment, the oxygen partial pressure increases significantly, which promotes the diffusion of oxygen ions through the crystal surface to the interior and quickly fills Fe 3+ and Y 3+ The oxygen vacancies around the ions completely eliminate the oxygen vacancy defects in the yttrium iron garnet crystal, increasing the Faraday rotation angle by 15-20%, thereby improving the optomagnetic properties (such as Verdet constant, transmittance) and crystal integrity of the yttrium iron garnet crystal.

[0021] 3. Enhanced heat transfer efficiency in high-pressure environments reduces overall energy consumption by 30-40%, achieving both energy and cost optimization. High pressure also inhibits the influx of impurity gases (such as N₂ and CO₂), reducing secondary pollution. This invention is also adaptable to large-sized YTG crystals (diameter >20 mm), meeting the needs of industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic structural diagram of a high-pressure oxygen atmosphere annealing device for yttrium iron garnet crystals.

[0023] Figure 2 This is the transmission spectrum of sodium-doped yttrium iron garnet single crystal at a pressure of 10 MPa and different annealing temperatures.

[0024] Figure 3This is a transmittance curve of sodium-doped yttrium iron garnet single crystal at 900℃ and different annealing pressures.

[0025] Figure 4 This is a transmittance curve of yttrium iron garnet single crystal at a pressure of 10 MPa and different annealing temperatures. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] like Figure 1 As shown, a high-pressure oxygen atmosphere annealing device for yttrium iron garnet crystals includes a heating furnace, a high-pressure reaction chamber 11, a homogeneous ceramic sample chamber 12 of the same nature as the yttrium iron garnet crystal, an oxygen supply system, and a vacuum pipeline. The high-pressure reaction chamber 11 is installed in the heating furnace, which is provided with a preheating zone 4, a reaction zone 5, and a slow cooling zone 6. The high-pressure reaction chamber 11 runs through the preheating zone 4, the reaction zone 5, and the slow cooling zone 6. The homogeneous ceramic sample chamber 12 is placed in the high-pressure reaction chamber 11. The oxygen supply system includes a high-pressure oxygen cylinder 1, an oxygen supply pipeline, a precision pressure reducing valve 2, and a flow controller 13. The oxygen supply pipeline is connected to the high-pressure oxygen cylinder 1, the precision pressure reducing valve 2, and the flow controller 13, and is connected to the high-pressure reaction chamber 11 so as to supply high-pressure oxygen to the high-pressure reaction chamber 11. The vacuum pipeline connects the vacuum pump 9 and the high-pressure reaction chamber 11.

[0028] The high-pressure reaction chamber 11 can be made of a high-temperature and high-pressure-resistant nickel-, cobalt-, titanium-, molybdenum-, or tungsten-based alloy. A homogeneous ceramic sample chamber 12, made of the same material as the yttrium iron garnet crystals, prevents contamination of the yttrium iron garnet crystals. The oxygen supply system must ensure an oxygen purity of ≥99.999%. The reaction zone 5 is located between the preheating zone 4 and the slow cooling zone 6. The temperatures of the preheating zone 4, reaction zone 5, and slow cooling zone 6 can vary.

[0029] The vacuum pipeline is connected with a pressure relief valve 8 and a pressure sensor 7.

[0030] The pressure relief valve 8 and the pressure sensor 7 can form a safety protection to prevent the risk of overpressure. When the air pressure in the vacuum pipeline exceeds a predetermined value, the pressure relief valve 8 automatically opens to relieve the pressure.

[0031] The oxygen supply pipeline and the vacuum pipeline are both connected to the high-pressure reaction chamber 11 through the high-temperature alloy flange 10.

[0032] The high-temperature alloy flange 10 can be used to separate the high-pressure reaction chamber 11 from the vacuum pipeline, making it easier to remove or put in the yttrium iron garnet crystal. The high-temperature alloy flange 10 can also be used to separate the high-pressure reaction chamber 11 from the oxygen supply pipeline, making it easier to disassemble and repair the optical fiber head 3.

[0033] A high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystals comprises the following steps:

[0034] S1, pretreatment, placing the yttrium iron garnet crystal in a homogeneous ceramic sample cavity 12 to avoid reaction with the cavity material of the high-pressure reaction cavity 11 at high temperature.

[0035] S2, oxygenation and pressurization, start the vacuum pump 9, evacuate the high-pressure reaction chamber 11 through the vacuum pipeline, then open the high-pressure oxygen cylinder 1, and the high-pressure oxygen cylinder 1 introduces oxygen into the high-pressure reaction chamber 11 through the oxygen supply pipeline, and by operating the precision pressure reducing valve 2 and the flow controller 13, increase the pressure at a gradient of 0.5 MPa / min to raise the oxygen pressure to the target value of 5-20 MPa.

[0036] S3, heating annealing, operating the heating furnace to heat the high pressure reaction chamber 11 to 1000-1200° C. at a rate of 50-100° C. / h, and keep the temperature constant for 2-10 hours.

[0037] An optical fiber head 3 is fixedly installed in the oxygen inlet end of the high-pressure reaction chamber 11, and the optical fiber head 3 is connected to a laser. In step S3, pulsed oxygen free radical assisted annealing is adopted, the laser is started, and the laser is emitted through the optical fiber head 3, so that intermittent ultraviolet light excitation with a wavelength of 172nm / 185nm / 193nm / 254nm is introduced into the high-pressure oxygen environment in the high-pressure reaction chamber 11, so that O2 is decomposed into highly active oxygen free radicals, which react with Fe on the surface of the yttrium iron garnet crystal. 2+ Defective sites are selectively oxidized to Fe 3+ At the same time, the reaction depth is controlled by a pulse cycle of 10s on / 30s off, which improves the uniformity of the lattice redox reaction and significantly reduces optical scattering loss.

[0038] In step S3, the heating furnace is heated by a multi-stage resistance wire, combined with a PID temperature controller with an accuracy of ±0.1°C and a thermocouple for real-time monitoring.

[0039] S4, gradient cooling, operating the heating furnace to cool the high-pressure reaction chamber 11 to below 200° C. at a rate of ≤50° C. / h, and then naturally cooling to room temperature.

[0040] S5, releasing the pressure to take out the material, close the high-pressure oxygen cylinder 1 and the vacuum pump 9, operate the precision pressure reducing valve 2 to slowly release the pressure, and take out the crystals after the pressure in the high-pressure reaction chamber 11 drops to normal pressure.

[0041] The high-pressure atmosphere in the high-pressure reaction chamber 11 is controlled by coupling the oxygen atmosphere with gradient pressure increase and constant pressure, and the oxygen partial pressure is dynamically adjusted during the annealing process: in the initial stage, the pressure is increased from 0.1 MPa to 10 MPa by the gradient pressure increase method to promote the migration of lattice oxygen vacancies, in the middle stage, the constant pressure of 10 MPa is used to stabilize the diffusion of filling oxygen, and in the later stage, the pressure is reduced from 10 MPa to 0.1 MPa by the gradient pressure decrease method to suppress crystal stress cracks. The coordinated optimization of oxygen defect repair and crystal integrity is achieved through pressure timing control.

[0042] The temperature of the preheating zone 4 is 300-700°C, the temperature of the reaction zone 5 is 700-1000°C, and the temperature of the slow cooling zone 6 is 500-700°C. The heating furnace is a three-temperature zone tubular furnace, which cooperates with the axial vortex oxygen flow field and uses the temperature difference to drive the directional diffusion of oxygen ions, forming an oxygen concentration gradient in the preheating zone 4, realizing rapid bulk doping in the reaction zone 5, and eliminating grain boundary stress through oxygen flow vortex in the slow cooling zone 6, thereby improving the crystal magneto-optical figure of merit and the consistency of annealing batch performance.

[0043] Figure 2-Figure 4 The following are the transmission spectra of sodium-doped yttrium iron garnet single crystals at 10 MPa and different annealing temperatures after using the high-pressure oxygen atmosphere annealing apparatus and process of the present invention; the transmittance curves of sodium-doped yttrium iron garnet single crystals at 900°C and different annealing pressures; and the transmittance curves of yttrium iron garnet single crystals at 10 MPa and different annealing temperatures. The Faraday deflection angles of yttrium iron garnet single crystals at 10 MPa and different annealing temperatures after using the high-pressure oxygen atmosphere annealing apparatus and process of the present invention are shown in Table 1 below.

[0044] Table 1

[0045] Test wavelength Unannealed 700℃ 800℃ 900℃ 1000℃ 1310 nm 200 deg / cm 210 deg / cm 220 deg / cm 230 deg / cm 230 deg / cm 1550 nm 160 deg / cm 170 deg / cm 180 deg / cm 180 deg / cm 190 deg / cm 1990 nm 100 deg / cm 110 deg / cm 110 deg / cm 120 deg / cm 120 deg / cm

[0046] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A high-pressure oxygen atmosphere annealing device for yttrium iron garnet crystals, characterized in that: It includes a heating furnace, a high-pressure reaction chamber (11), a homogeneous ceramic sample chamber (12) that is homogeneous with the yttrium iron garnet crystal, an oxygen supply system, and a vacuum pipeline; The high-pressure reaction chamber (11) is installed in a heating furnace, and the heating furnace is provided with a preheating zone (4), a reaction zone (5), and a slow cooling zone (6). The high-pressure reaction chamber (11) runs through the preheating zone (4), the reaction zone (5), and the slow cooling zone (6). The homogeneous ceramic sample chamber (12) is placed in the high-pressure reaction chamber (11); The oxygen supply system comprises a high-pressure oxygen cylinder (1), an oxygen supply pipeline, a precision pressure reducing valve (2) and a flow controller (13); the oxygen supply pipeline is connected to the high-pressure oxygen cylinder (1), the precision pressure reducing valve (2) and the flow controller (13), and is in communication with the high-pressure reaction chamber (11) so as to supply high-pressure oxygen to the high-pressure reaction chamber (11); the vacuum pipeline is connected to the vacuum pump (9) and the high-pressure reaction chamber (11).

2. The high-pressure oxygen atmosphere annealing device for yttrium iron garnet crystal according to claim 1, characterized in that: The vacuum pipeline is connected to a pressure relief valve (8) and a pressure sensor (7).

3. The high-pressure oxygen atmosphere annealing device for yttrium iron garnet crystal according to claim 1, characterized in that: The oxygen supply pipeline and the vacuum pipeline are both connected to the high-pressure reaction chamber (11) via a high-temperature alloy flange (10).

4. A high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystals, characterized in that: A high-pressure oxygen atmosphere annealing device for a yttrium iron garnet crystal according to any one of claims 1 to 3 comprises the following steps: S1, pretreatment, placing the yttrium iron garnet crystal in a homogeneous ceramic sample cavity (12) to avoid reaction with the cavity material of the high-pressure reaction cavity (11) at high temperature; S2, oxygenation and pressurization, starting the vacuum pump (9), evacuating the high-pressure reaction chamber (11) through the vacuum pipeline, then opening the high-pressure oxygen cylinder (1), and the high-pressure oxygen cylinder (1) passes oxygen into the high-pressure reaction chamber (11) through the oxygen supply pipeline, and by operating the precision pressure reducing valve (2) and the flow controller (13), the pressure is increased at a gradient of 0.5 MPa / min, and the oxygen pressure is increased to a target value of 5-20 MPa; S3, heating annealing, operating the heating furnace to raise the temperature in the high-pressure reaction chamber (11) to 1000-1200°C at a rate of 50-100°C / h, and maintaining the temperature for 2-10 hours; S4, gradient cooling, operating the heating furnace to cool the high-pressure reaction chamber (11) to below 200°C at a rate of ≤50°C / h, and then naturally cooling to room temperature; S5, releasing the pressure to take out the material, closing the high-pressure oxygen cylinder (1) and the vacuum pump (9), operating the precision pressure reducing valve (2) to slowly release the pressure, and taking out the crystals after the pressure in the high-pressure reaction chamber (11) drops to normal pressure.

5. The high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystal according to claim 4, characterized in that: The high-pressure atmosphere in the high-pressure reaction chamber (11) is controlled by a gradient pressure increase and a constant pressure coupled oxygen atmosphere, and the oxygen partial pressure is dynamically adjusted during the annealing process: in the initial stage, the pressure is increased from 0.1 MPa to 10 MPa by a gradient pressure increase method to promote the migration of lattice oxygen vacancies, in the middle stage, a constant pressure of 10 MPa is used to stabilize the diffusion of filling oxygen, and in the later stage, the pressure is reduced from 10 MPa to 0.1 MPa by a gradient pressure decrease method to suppress crystal stress cracks, and the coordinated optimization of oxygen defect repair and crystal integrity is achieved through pressure timing control.

6. The high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystal according to claim 4, characterized in that: An optical fiber head (3) is fixedly installed in the oxygen inlet end of the high-pressure reaction chamber (11), and the optical fiber head (3) is connected to a laser. In the step S3, pulsed oxygen free radical assisted annealing is adopted to start the laser, and the laser is emitted through the optical fiber head (3), so as to form an intermittent ultraviolet light excitation with a wavelength of 172nm / 185nm / 193nm / 254nm in the high-pressure oxygen environment in the high-pressure reaction chamber (11), so that O2 is decomposed into highly active oxygen free radicals, which react with Fe on the surface of the yttrium iron garnet crystal. 2+ Defective sites are selectively oxidized to Fe 3+ At the same time, the reaction depth is controlled by a pulse cycle of 10s on / 30s off, which improves the uniformity of the lattice redox reaction and significantly reduces optical scattering loss.

7. The high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystal according to claim 4, characterized in that: In step S3, the heating furnace is heated by a multi-segment resistance wire, combined with a PID temperature controller with an accuracy of ±0.1°C and a thermocouple for real-time monitoring.

8. The high-pressure oxygen atmosphere annealing process for yttrium iron garnet crystal according to claim 4, characterized in that: The temperature of the preheating zone (4) is 300-700°C, the temperature of the reaction zone (5) is 700-1000°C, and the temperature of the slow cooling zone (6) is 500-700°C. The heating furnace is a three-temperature zone tubular furnace, which cooperates with the axial vortex oxygen flow field and uses the temperature difference to drive the directional diffusion of oxygen ions, forming an oxygen concentration gradient in the preheating zone (4), realizing rapid bulk doping in the reaction zone (5), and eliminating grain boundary stress through oxygen flow vortex in the slow cooling zone (6), thereby improving the crystal magneto-optical figure of merit and the consistency of annealing batch performance.

Images