Cubic fluorite-type terbium scandium tantalate magneto-optic crystal and preparation method thereof

Abstract

This invention discloses a cubic fluorite-type terbium scandium tantalate magneto-optical crystal and its preparation method. The molecular formula of the crystal is Tb. 3‑ x Sc x TaO7, where x = 0.8~2, belongs to the cubic crystal system with space group Fm-3m. This invention involves doping small-radius Sc atoms into Tb3TaO7 crystals. 3+ Replace part of Tb 3+ This invention achieves a structural transformation of crystals from a low-symmetry orthorhombic phase to a high-symmetry cubic phase, and successfully grows high-quality bulk single crystals with centimeter-scale cubic phase using the Czochralski method. The crystals prepared by this invention exhibit good crystallinity, high quality, and excellent magneto-optical properties, showing promising application prospects in the fabrication of devices such as magneto-optical isolators, magneto-optical circulators, and magneto-optical modulators.

Description

Technical Field

[0001] This invention belongs to the field of magneto-optical crystal materials technology, specifically relating to a cubic fluorite-type terbium scandium tantalate magneto-optical crystal and its preparation method. Background Technology

[0002] With the rapid development of technologies such as optical communication, fiber lasers, and lidar, devices such as magneto-optical isolators, magneto-optical circulators, magneto-optical modulators, and fiber optic current sensors are placing higher demands on the comprehensive performance of magneto-optical materials. As the core functional material for magneto-optical devices, magneto-optical crystals typically require a large Faraday rotation angle, high transmittance, good thermal stability, and low optical loss. Currently, the most commonly used magneto-optical crystals include terbium gallium garnet (TGG), terbium aluminum garnet (TAG), and yttrium iron garnet (YIG). While TGG has achieved commercial application, the growth process of TGG crystals is difficult to control, making it challenging to grow larger, higher-quality TGG crystals, which are often required for device fabrication. Although TAG possesses superior magneto-optical properties, it is a heterogeneous molten compound, making it difficult to grow large-size, high-quality single crystals. YIG, on the other hand, is mainly suitable for specific near-infrared bands.

[0003] Among Re3MO7 (Re is a rare earth element, M is Ta or Nb) series compounds, due to their high rare earth ion concentration and the iso-compositional melting characteristics of most systems, they have attracted widespread attention in the research of novel magneto-optical crystals. Tb3TaO7 possesses a high content of magnetic rare earth ions and a strong crystal field effect, which is beneficial for increasing the effective transition wavelength of magnetic ions, thereby obtaining a strong magneto-optical effect and showing potential for development into a visible-near-infrared magneto-optical crystal. Existing research has shown that as the average radius of cations in the Re3MO7 system decreases, the crystal structure can transform from an orthorhombic phase to a cubic defect fluorite structure with higher symmetry. Therefore, by introducing Sc... 3+ Structural modulation of Tb3TaO7 was performed to improve crystal symmetry and reduce birefringence. Furthermore, terbium tantalate (Tb3TaO7) crystals possess extremely high magnetic rare-earth ion concentrations and strong crystal field interactions, theoretically exhibiting better magneto-optical effects than TGG.

[0004] However, conventional Tb3TaO7 crystals exhibit a low-symmetry orthorhombic phase structure at room temperature. The anisotropic birefringence caused by this low symmetry significantly reduces the extinction ratio of isolators, making them unsuitable for practical optoelectronic devices. Therefore, developing novel magneto-optical crystal materials that combine high magneto-optical performance, high symmetry, low birefringence, and suitability for crystal growth remains an important research direction in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a cubic fluorite-type terbium scandium tantalate (Tb 3- x Sc x TaO7 magneto-optical crystal materials, their preparation methods, and applications. High-quality single crystals at the centimeter scale and above are grown using the Czochralski method, exhibiting advantages such as good crystallinity, high crystal quality, and excellent magneto-optical properties. It is expected to find practical applications in the fabrication of devices such as magneto-optical isolators, magneto-optical circulators, and magneto-optical modulators.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a cubic fluorite-type terbium scandium tantalate magneto-optical crystal, wherein the crystal has the chemical formula Tb 3-x Sc x TaO7, where x = 0.8-2, is a cubic crystal system with space group Fm-3m. 。

[0007] In a second aspect, the present invention provides a method for preparing a cubic fluorite-type terbium scandium tantalate magneto-optical crystal as described in claim 1, comprising the following steps: (1) Synthesis of high-purity polycrystalline raw materials: according to Tb 3-x Sc x To obtain polycrystalline raw material, Tb4O7, Sc2O3 and Ta2O5 were weighed out in stoichiometry, mixed and ground evenly in a mortar, pressed into wafers, and then sintered at high temperature multiple times. (2) Crystal growth: The polycrystalline raw material is placed in a crucible and single crystal pulling is performed under an inert gas atmosphere; (3) Crystal annealing: After the crystal growth is completed, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1-3 mm higher than the melt. The crystal is then slowly annealed to room temperature to obtain cubic fluorite-type terbium scandium tantalate crystal.

[0008] Furthermore, the high-temperature sintering temperature in step (1) is 1500~1800℃, the time is 15h, and the number of sintering cycles is 2~5.

[0009] Furthermore, the crucible mentioned in step (2) is an iridium crucible with a melting point of 1772°C.

[0010] Furthermore, the growth temperature of the single crystal pulling in step (2) is 1800~2000℃, the growth rate is 0.5~1mm / h, and the crystal rotation speed is 13~18r / min.

[0011] Furthermore, the inert gas mentioned in step (2) is N2, Ar, or He.

[0012] Thirdly, the present invention provides the application of the above-mentioned cubic fluorite-type terbium scandium tantalate magneto-optical crystal in magneto-optical materials.

[0013] The beneficial effects of this invention are as follows: (1) The cubic fluorite-type terbium scandium tantalate magneto-optical crystal material (Tb) prepared in this invention 3-x Sc x TaO7 belongs to the cubic crystal system with space group Fm-3m. It can be produced by doping with small-radius Sc... 3+ The structure of Tb3TaO7 was successfully transformed from a low-symmetry orthorhombic phase to a high-symmetry cubic fluorite structure. Stable, high-quality cubic Tb3TaO7 was obtained at room temperature using the Czochralski method. 3-x Sc x TaO7 single crystal.

[0014] (2) Tb obtained by the present invention 3-x Sc x The cubic crystal system of TaO7 can effectively avoid the influence of birefringence on the magneto-optical effect of the crystal. The high content of rare earth ions in the crystal results in a strong magneto-optical effect.

[0015] (3) Tb obtained by the present invention 3-x Sc x TaO7 crystal material has a high Feld constant, which gives it a great advantage in the fabrication of magneto-optical isolators without magnetic rings. It is expected to be used in the fabrication of devices such as magneto-optical isolators, magneto-optical circulators, and magneto-optical modulators.

[0016] In summary, this invention successfully grows high-quality bulk single crystals with cubic phases and centimeter-scale dimensions using the Czochralski method. While maintaining excellent magneto-optical performance, it effectively eliminates birefringence, which has significant scientific research value and economic benefits for improving the performance of magneto-optical devices and promoting device miniaturization. Attached Figure Description

[0017] Figure 1 For Tb 3-x Sc x X-ray diffraction (XRD) pattern of TaO7 crystal raw material, PDF#38-1408: Standard card of cubic phase Tb3TaO7 with space group Fm-3m.

[0018] Figure 2 For Tb 3-x Sc x Transmission spectrum of TaO7 crystal.

[0019] Figure 3 For Tb 3-x Sc x The curve showing the relationship between the Faraday rotation angle of TaO7 and the applied magnetic field.

[0020] Figure 4 This is a schematic diagram of the Faraday magneto-optical effect testing system used in this invention. Reference numerals: 1. Laser; 2. Polarizer; 3. Electromagnet; 4. Sample; 5. Analyzer; 6. Angle-rotating frame; 7. Optical power meter. Detailed Implementation

[0021] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0022] A cubic fluorite-type terbium scandium tantalate magneto-optical crystal material is prepared by the following steps: (1) Synthesis of polycrystalline raw materials: Tb 3-x Sc x The stoichiometric ratio of TaO7 is Tb4O7:Sc2O3:Ta2O5 = 3-x:2x:2, where x = 0.8~2. Tb4O7, Sc2O3 and Ta2O5 are accurately weighed according to the stoichiometric ratio, mixed and ground evenly in a mortar, and then pressed into wafers. The pressed wafers are then sintered at a high temperature of 1500~1800℃ for 15 h. The sintering process is repeated three times to obtain polycrystalline raw materials. (2) Crystal growth: Crystal growth is carried out by the Czochralski method. The synthesized polycrystalline raw material is placed in a crucible and single crystal is pulled under an inert gas atmosphere (such as N2, Ar, etc.). The growth temperature is 1800~2000℃, the growth rate is 0.5~1mm / h, and the crystal rotation speed is 13~18r / min. (3) Crystal annealing: After the crystal growth is completed, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1~3mm higher than the melt. Then it is annealed to room temperature to obtain cubic fluorite-type terbium scandium tantalate magneto-optical crystal material with space group Fm-3m.

[0023] Example 1 The specific steps for growing cubic fluorite-type terbium scandium tantalate magneto-optical crystal material Tb₂ScTaO₇ using the Czochralski method are as follows: (1) The stoichiometric ratio of Tb2ScTaO7 is Tb4O7:Sc2O3:Ta2O5 = 1:1:1. Tb4O7 (99.99%), Sc2O3 (99.99%) and Ta2O5 (99.99%) are accurately weighed according to the stoichiometric ratio, mixed and ground evenly in a corundum mortar, and pressed into a wafer. The pressed wafer is then placed in a box furnace and sintered at 1500℃ for 15 h. The sintering process is repeated three times to obtain Tb2ScTaO7 polycrystalline raw material.

[0024] (2) An iridium crucible (melting point 1772℃) was used as the container for crystal growth. The prepared polycrystalline raw material was added to the crucible and placed in a single crystal pulling furnace for single crystal pulling under a high-purity Ar atmosphere. The growth temperature was 1800~2000℃, the growth rate was 0.9mm / h, and the crystal rotation speed was 13r / min.

[0025] (3) After the crystal growth is completed, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1-3 mm higher than the melt. Then it is annealed to room temperature to obtain a Tb2ScTaO7 crystal with a size of 18 mm × 12 mm.

[0026] The molar percentages of each element in the crystals prepared in Example 1 were determined by EDS testing, and the crystal chemical formula of Example 1, Tb2ScTaO7, was determined. The fitted cell parameters were a=b=c=5.1084Å.

[0027] The structure of the polycrystalline raw material and the grown crystal was determined using X-ray powder diffraction (XRD), and the results are as follows: Figure 1 As shown, the XRD diffraction peak positions of the Tb2ScTaO7 crystal all match those of the Tb3TaO7 standard card (PDF#38-1408) with space group Fm-3m, indicating that the crystal is a fluorite phase and has no other impurities.

[0028] Figure 2 The image shows the transmission spectrum of the crystal obtained in the example. The results show that the polished wafer has good optical transmittance in the 500 nm to 1500 nm wavelength range.

[0029] The Faraday rotation angles of the crystal obtained in Example 1 at 532 nm, 633 nm, and 1064 nm were measured using the extinction method, and the results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the Faraday rotation angle of Tb2ScTaO7 crystal increases with the increase of magnetic field strength, showing a linear relationship.

[0030] Example 2 Czochralski-grown cubic fluorite-type terbium scandium tantalate magneto-optical crystal material Tb 1.5 Sc 1.5 The specific steps for preparing TaO7 are as follows: (1) Tb 1.5 Sc 1.5The stoichiometric ratio of TaO7 is Tb4O7:Sc2O3:Ta2O5 = 0.75:1.5:1. Tb4O7 (99.99%), Sc2O3 (99.99%), and Ta2O5 (99.99%) were accurately weighed according to this stoichiometric ratio, mixed, and ground evenly in a corundum mortar. The mixture was then pressed into wafers. The pressed wafers were then sintered in a box furnace at 1500℃ for 15 hours. This sintering process was repeated three times to obtain Tb4O7. 1.5 Sc 1.5 TaO7 polycrystalline raw material.

[0031] (2) An iridium crucible was used as the container for crystal growth. The prepared polycrystalline raw material was added to the crucible and placed in a single crystal pulling furnace. Single crystal pulling was carried out under a high-purity Ar atmosphere. The growth temperature was 1800~2000℃, the growth rate was 0.9mm / h, and the crystal rotation speed was 13r / min.

[0032] (3) After the crystal growth is complete, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1-3 mm above the melt. Then, it is annealed to room temperature to obtain a Tb crystal with dimensions of 18 mm × 12 mm. 1.5 Sc 1.5 TaO7 crystals.

[0033] Example 3 The specific steps for growing cubic fluorite-type terbium scandium tantalate magneto-optical crystal material TbSc2TaO7 using the Czochralski method are as follows: (1) The stoichiometric ratio of TbSc2TaO7 is Tb4O7:Sc2O3:Ta2O5 = 1:4:2. Tb4O7 (99.99%), Sc2O3 (99.99%) and Ta2O5 (99.99%) are accurately weighed according to the stoichiometric ratio, mixed and ground evenly in a corundum mortar, and pressed into a wafer. The pressed wafer is then placed in a box furnace and sintered at 1500℃ for 15 h. The sintering process is repeated three times to obtain TbSc2TaO7 polycrystalline raw material.

[0034] (2) An iridium crucible was used as the container for crystal growth. The prepared polycrystalline raw material was added to the crucible and placed in a single crystal pulling furnace. Single crystal pulling was carried out under a high-purity Ar atmosphere. The growth temperature was 1800~2000℃, the growth rate was 0.9mm / h, and the crystal rotation speed was 13r / min.

[0035] (3) After the crystal growth is completed, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1-3 mm higher than the melt. Then it is annealed to room temperature to obtain a TbSc2TaO7 crystal with a size of 18 mm × 12 mm.

[0036] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A cubic fluorite-type terbium scandium tantalate magneto-optical crystal, characterized in that: The crystal has the chemical formula Tb. 3-x Sc x TaO7, where x = 0.8-2, is a cubic crystal system with space group Fm-3m. 。 2. A method for preparing the cubic fluorite-type terbium scandium tantalate magneto-optical crystal as described in claim 1, characterized in that: Includes the following steps: (1) Synthesis of high-purity polycrystalline raw materials: according to Tb 3-x Sc x To obtain polycrystalline raw material, Tb4O7, Sc2O3 and Ta2O5 were weighed out in stoichiometry, mixed and ground evenly in a mortar, pressed into wafers, and then sintered at high temperature multiple times. (2) Crystal growth: The polycrystalline raw material is placed in a crucible and single crystal pulling is performed under an inert gas atmosphere; (3) Crystal annealing: After the crystal growth is completed, the crystal is lifted and removed from the melt. The crystal height is adjusted so that it is 1-3 mm higher than the melt. The crystal is then slowly annealed to room temperature to obtain cubic fluorite-type terbium scandium tantalate crystal.

3. The method according to claim 2, characterized in that: The high-temperature sintering temperature in step (1) is 1500~1800℃, the time is 15h, and the number of sintering times is 2~5.

4. The method according to claim 2, characterized in that: The crucible mentioned in step (2) is an iridium crucible with a melting point of 1772℃.

5. The method according to claim 2, characterized in that: The growth temperature of the single crystal pulling in step (2) is 1800~2000℃, the growth rate is 0.5~1mm / h, and the crystal rotation speed is 13~18r / min.

6. The method according to claim 2, characterized in that: The inert gas mentioned in step (2) is N2, Ar, or He.

7. The application of the cubic fluorite-type terbium scandium tantalate magneto-optical crystal as described in claim 1 in magneto-optical materials.

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