阅读说明：本技术 一种硅酸镧铽磁光晶体及其制备方法 (Lanthanum-terbium silicate magneto-optical crystal and preparation method thereof ) 是由 陈新 孙文翰 郭正威 胡晓琳 庄乃锋 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种可应用于可见-近红外光区的具有高费尔德常数的硅酸镧铽磁光晶体及其制备方法。所述磁光晶体的化学式为Tb-(10-x)La-(x)(SiO-(4))-(6)O-(3),其中x＝0.5～1。该晶体属六方晶系,空间群为。本发明制得的磁光晶体在可见-近红外波段具有较好的透光性能,同时,具有较高的磁性稀土离子含量和较强的晶体场作用,故有利于产生较好的磁光性能,其费尔德常数(Verdet constant)远高于目前商品化应用的掺铽玻璃及铽镓石榴石(TGG)晶体。此外,该磁光晶体为一致熔融化合物,生长温度为1960～2050℃,可采用中频感应提拉法生长,工艺简单、周期短,能够实现大规模低成本的批量生产。(The invention discloses a terbium lanthanum silicate magneto-optical crystal with high Verdet constant and applicable to a visible-near infrared region and a preparation method thereof. The chemical formula of the magneto-optical crystal is Tb 10‑x La x (SiO 4 ) 6 O 3 Wherein x is 0.5 to 1. The crystal belongs to a hexagonal system and has a space group of)

1. A lanthanum silicate terbium magneto-optical crystal characterized by: molecular formula of Tb_10-xLa_x(SiO₄)₆O₃Wherein x =0.5 to 1, belongs to the hexagonal system, and is voidAre grouped as。

2. A method of making a lanthanum silicate terbium magneto-optical crystal according to claim 1, wherein: and a melt pulling method is adopted for single crystal growth.

3. The method of claim 2, wherein: the method comprises the following steps:

(1) synthesis of polycrystalline raw materials: according to Tb_10-xLa_x(SiO₄)₆O₃Wherein x = 0.5-1 stoichiometric ratio and La is accurately weighed₂O₃、Tb₄O₇And SiO₂Grinding and tabletting, and then performing high-temperature solid phase sintering to obtain a polycrystalline raw material;

(2) growing a single crystal: carrying out pulling growth on the polycrystalline raw material in an inert protective atmosphere, controlling the growth temperature to be 1960-2050 ℃, the growth speed to be 0.2-1.0 mm/h, and the crystal rotation speed to be 12-20 r/min;

(3) crystal annealing: and after the crystal growth is finished, extracting the melt and annealing to room temperature, wherein the annealing rate is 10-80 ℃/h, and thus the lanthanum terbium silicate magneto-optical crystal is obtained.

4. Use of a lanthanum terbium silicate magneto-optical crystal according to claim 1 or a lanthanum terbium silicate magneto-optical crystal obtained by the method according to claim 2, characterized in that: the method is used for preparing magneto-optical materials in the visible-near infrared light region.

Technical Field

The invention belongs to the technical field of magneto-optical materials and crystal growth, and particularly relates to a terbium lanthanum silicate magneto-optical crystal with a high Verdet constant and a preparation method thereof.

Background

The magneto-optical material is an optical information functional material with magneto-optical effect from ultraviolet to infrared bands, and is an indispensable key functional material in the information industry of the new generation. Devices such as an optical isolator, an optical fiber current sensor, a magneto-optical switch, an optical modulator and the like which take magneto-optical materials as cores are important basic devices in the fields of optical communication, the Internet of things, smart grids and the like. The optical isolator is one of the key devices in the modern optical communication technology field, and is called as a diode in an optical path. With the arrival of the big data age, the global optical communication technology will enter a new development stage, and the visible-near infrared band optical transmission technology will be applied to more fields. However, most of the magneto-optical materials required for the development of domestic related magneto-optical devices still depend on foreign import, which becomes a bottleneck for restricting the development of domestic autonomous magneto-optical devices.

In the magneto-optical material, the magneto-optical glass is used as an amorphous magneto-optical material, has higher transmittance and isotropy in a visible-near infrared band, and is easy to prepare large-size products. However, the verdet constant of magneto-optical glass is small, which is not favorable for miniaturization and integration of devices. Meanwhile, magneto-optical glass has poor thermal conductivity and small laser damage resistance threshold, and is not suitable for being applied to a high-power laser system. At present, the crystalline magneto-optical material widely applied in a visible-near infrared band (400-1100 nm) is mainly a Terbium Gallium Garnet (TGG) crystal. However, the growth process of the crystal is not easy to control, the domestic growth of high-quality and large-size TGG crystal is difficult, and compared with the foreign TGG product, the two indexes of absorption loss and extinction ratio are still different. In addition, the TGG crystal has expensive raw materials and high growth cost, and the Verdet constant of the TGG crystal is still small in practical application, especially in a high-power laser isolator.

Oxyapatite type rare earth silicic acidSalt Ca₂Tb₈(SiO₄)₆O₂Belongs to a hexagonal system and has a space group of. Its crystal structure is unique, and its unit cell contains 6 [ SiO ]₄]Tetrahedron and two additional O. [ SiO ]₄]The tetrahedra are layered in the c-axis direction, are not connected with each other, are basic structural units of unit cell, and the extra O does not belong to any [ SiO ]₄]A tetrahedron. Tb occupies 6 lattice positions of 6h completely in the structure, and also occupies 4 lattice positions of 4f together with Ca, so that the content of magnetic rare earth ions is high, the density is high, the interaction among the magnetic ions is strong, and the strong magneto-optical effect is favorably generated. Tb can be used if consideration is given to valence state equilibrium to achieve maximum increase of Tb ion content³⁺Complete substitution of Ca²⁺I.e. Tb₁₀(SiO₄)₆O₃. But due to Tb³⁺Much smaller than the radius of the substituted Ca²⁺，Tb₁₀(SiO₄)₆O₃The crystal structure of (2) can generate serious lattice distortion, thereby generating large structural stress to crack and even break the crystal. Is not beneficial to the growth of complete block crystals and the practical application of crystal materials. The invention is realized by that Tb is₁₀(SiO₄)₆O₃In the crystal, a small amount of large-radius rare earth ions La are doped to adjust and optimize the microstructure of the crystal, so that the structural stress in the crystal is reduced to a certain extent, and the growth of a large-size high-optical-quality complete single crystal is realized.

Disclosure of Invention

The invention aims to provide a terbium lanthanum silicate magneto-optical crystal with a high Verdet constant, which can be applied to a visible-near infrared region, and a preparation method thereof. The magneto-optical crystal has the advantages of good light transmission performance, high content of magnetic rare earth ions, strong crystal field effect and the like, and is favorable for generating better magneto-optical performance. In addition, the magneto-optical crystal is a consistent melting compound, the growth temperature is 1960-2050 ℃, a medium-frequency induction pulling method can be adopted for growth, the process is simple, the period is short, and large-scale low-cost batch production can be realized.

In order to achieve the purpose, the invention adopts the following technical scheme:

high Verdet constant terbium silicate magneto-optical crystal with chemical formula Tb_10-xLa_x(SiO₄)₆O₃Wherein x is 0.5 to 1, belongs to the hexagonal system, and has a space group ofThe Mohs hardness was 5 moh.

The high-Verdet constant terbium silicate magneto-optical crystal adopts a melt pulling (Czochralski) method for single crystal growth, and the preparation method comprises the following steps:

1) and (4) synthesizing high-purity initial raw materials. According to the synthesis of Tb_10-xLa_x(SiO₄)₆O₃(x is 0.5-1) the medicine (Tb) is accurately weighed according to the stoichiometric ratio₄O₇Purity 99.99% La₂O₃Purity 99.99% and SiO₂Purity 99.95%), and the weighed medicines are put into a corundum mortar to be ground uniformly and pressed into tablets, and then high-temperature sintering is carried out to obtain the initial raw materials required by crystal growth.

2) And (4) growing a single crystal. The iridium crucible is used as a container for crystal growth, and the synthesized starting material is charged into the container and placed in a single crystal pulling furnace under an inert gas (e.g., N)₂Ar, etc.) at the growth temperature of 1960-2050 ℃, the growth speed of 0.2-1.0 mm/h and the crystal rotation speed of 12-20 r/min. The change conditions of the aperture and the growth trend during the crystal growth are observed through a quartz observation window on the single crystal pulling furnace, and the growth form of the crystal is controlled by adjusting the rise and fall of the potential and the change rate of the potential through an European land surface.

3) And (5) annealing the crystal. After the crystal growth is finished, lifting the crystal and separating the crystal from the melt, adjusting the height of the crystal to be 1-3 mm higher than the surface of the melt, and then slowly annealing to room temperature at a cooling rate of 10-80 ℃/h. Namely, obtaining a high Verdet constant Tb_10-xLa_x(SiO₄)₆O₃(x is 0.5-1) magneto-optical crystal blank.

The invention has the beneficial effects that: the invention can obtain the terbium silicate magneto-optical crystal with high optical quality, larger size and excellent physical and chemical properties and high Verdet constant. The magneto-optical crystal has good light transmission performance in visible-near infrared bands, and meanwhile, the magneto-optical crystal has high content of magnetic rare earth ions, strong crystal field effect and large electron exchange effect, and is beneficial to generating good magneto-optical performance. The Verdet constant is much higher than that of terbium-doped glass and TGG crystal which are commercially used at present. In addition, the magneto-optical crystal is a consistent melting compound, the growth temperature is 1960-2050 ℃, the magneto-optical crystal can be grown by adopting a medium-frequency induction Czochralski method, the growth process is simple, the period is short, and large-scale low-cost batch production can be realized.

Drawings

FIG. 1 shows a magneto-optical crystal Tb according to the invention_9.5La_0.5(SiO₄)₆O₃The Rietveld fine modification of (1).

FIG. 2 shows a magneto-optical crystal Tb according to the invention_9.5La_0.5(SiO₄)₆O₃A transmission spectrum of (a).

FIG. 3 is a schematic diagram of a Faraday magneto-optical effect testing system for detection according to the present invention: 1-a laser; 2-a polarizer; 3-an electromagnet; 4-sample; 5-an analyzer; 6-rotating the mirror holder by an angle; 7-optical power meter.

FIG. 4 shows a magneto-optical crystal Tb according to the invention_9.5La_0.5(SiO₄)₆O₃Faraday rotation diagram of (a).

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.

Example 1: melt Czochralski method for growing Tb with high Verdet constant_9.5La_0.5(SiO₄)₆O₃A magneto-optical crystal.

Will press Tb_9.5La_0.5(SiO₄)₆O₃Tb with accurately weighed stoichiometric ratio₄O₇（99.99%）、La₂O₃（99.99%）、SiO₂(99.95%) were put in a corundum mortar and ground uniformly, and after tabletting, they were placed in a muffle furnace for solid phase reaction at 1000 ℃ for 12 hours. Taking out, grinding, tabletting, heating to 1450 deg.C, and performing solid phase reaction for 24 hr to obtain initial raw material for crystal growth. The adopted size is phi 50 multiplied by 40mm³The iridium crucible of (1) is used as a container for crystal growth, and the synthesized polycrystalline powder raw material is charged into the container and put into a single crystal pulling furnace, and N is added₂And (4) carrying out single crystal pulling under the atmosphere. The growth temperature is 2050 ℃, the growth speed is 0.2-0.5 mm/h, and the crystal rotation speed is 12 r/min. In the growth process, the change conditions of the aperture and the growth trend during the crystal growth are observed through the quartz observation window, and the growth form of the crystal is controlled by adjusting the rise and fall of the potential and the change rate of the potential through the European land surface. After the growth is finished, the crystal is lifted and separated from the melt, and the height of the crystal is adjusted to be 1-3 mm higher than the surface of the melt. Then setting a cooling program, slowly annealing to room temperature at a cooling rate of 5-60 ℃/h for 43 hours to obtain Tb with the size of 15mm multiplied by 20mm (equal diameter part)_9.5La_0.5(SiO₄)₆O₃And (4) crystals.

Tb obtained in example 1 was recorded using an X-pert powder diffractometer_9.5La_0.5(SiO₄)₆O₃And (3) performing X-ray diffraction spectrum on the crystal powder, and refining the crystal structure by using a Rietveld method, wherein the computer program is DBWS-9411. The results of the function fitting were compared to the experimental results of the crystal, as shown in fig. 1. The result shows that the curve of the function calculation is well matched with the experimental result, the final refinement factor reaches Rwp =5.11%, and the grown crystal is in a hexagonal apatite structure, and the space group isNo other hetero-phase substances are present. Tb is to be_9.5La_0.5(SiO₄)₆O₃After the crystal is oriented, cut and polished, the transmission spectrum of the crystal at room temperature of 400-1500 nm is tested on a Perkin-Elmer Lambda UV/Vis/NIR spectrometer, as shown in figure 2. The results show thatThe magneto-optical crystal has Tb in a waveband of 400-1500 nm except 485nm³⁺Besides the characteristic absorption peak of the ions, other wave bands all show higher transmittance. Particularly, at the visible light wave band of 400-650 nm, the transmittance of the magneto-optical crystal is obviously increased compared with that of a TGG crystal. The extinction method is adopted to test the magneto-optical crystal Tb in the self-made Faraday magneto-optical effect test system (figure 3)_9.5La_0.5(SiO₄)₆O₃The faraday rotation angle of (a) as shown in figure 4. The results showed that the Verdet constant at 633nm was-260 rad/Tm, about 2 times that of commercial TGG crystals.

Example 2: melt Czochralski method for growing Tb with high Verdet constant_9.3La_0.7(SiO₄)₆O₃A magneto-optical crystal.

Will press Tb_9.3La_0.7(SiO₄)₆O₃Tb with accurately weighed stoichiometric ratio₄O₇（99.99%）、La₂O₃（99.99%）、SiO₂(99.95%) were put in a corundum mortar and ground uniformly, and after tabletting, they were placed in a muffle furnace for solid phase reaction at 1000 ℃ for 12 hours. Taking out, grinding, tabletting, heating to 1450 deg.C, and performing solid phase reaction for 24 hr to obtain initial raw material for crystal growth. The adopted size is phi 50 multiplied by 40mm³The iridium crucible of (1) is used as a container for crystal growth, and the synthesized polycrystalline powder raw material is charged into the container, and is placed in a single crystal pulling furnace, and single crystal pulling is performed under an Ar atmosphere. The growth temperature is 2000 ℃, the growth speed is 0.5-1.0/h, and the crystal rotation speed is 15 r/min. In the growth process, the change conditions of the aperture and the growth trend during the crystal growth are observed through the quartz observation window, and the growth form of the crystal is controlled by adjusting the rise and fall of the potential and the change rate of the potential through the European land surface. After the growth is finished, the crystal is lifted and separated from the melt, and the height of the crystal is adjusted to be 1-3 mm higher than the surface of the melt. Then setting a cooling program, slowly annealing to room temperature at a cooling rate of 5-60 ℃/h for 39 hours to obtain Tb with the size of 20mm multiplied by 20mm (equal diameter part)_9.3La_0.7(SiO₄)₆O₃The crystal is a mixture of a crystal and a metal,the Verdet constant of the optical fiber is about-251 rad/Tm in a wave band of 633 nm.

Example 3: melt Czochralski method for growing Tb with high Verdet constant₉La₁(SiO₄)₆O₃A magneto-optical crystal.

Will press Tb₉La₁(SiO₄)₆O₃Tb with accurately weighed stoichiometric ratio₄O₇（99.99%）、La₂O₃（99.99%）、SiO₂(99.95%) were put in a corundum mortar and ground uniformly, and after tabletting, they were placed in a muffle furnace for solid phase reaction at 1000 ℃ for 12 hours. Taking out, grinding, tabletting, heating to 1450 deg.C, and performing solid phase reaction for 24 hr to obtain initial raw material for crystal growth. The adopted size is phi 50 multiplied by 40mm³The iridium crucible of (1) is used as a container for crystal growth, and the synthesized polycrystalline powder raw material is charged into the container, and is placed in a single crystal pulling furnace, and single crystal pulling is performed under an Ar atmosphere. The growth temperature is 1970 ℃, the growth speed is 0.5-1.0/h, and the crystal rotation speed is 15-20 r/min. In the growth process, the change conditions of the aperture and the growth trend during the crystal growth are observed through the quartz observation window, and the growth form of the crystal is controlled by adjusting the rise and fall of the potential and the change rate of the potential through the European land surface. After the growth is finished, the crystal is lifted and separated from the melt, and the height of the crystal is adjusted to be 1-3 mm higher than the surface of the melt. Then setting a cooling program, slowly annealing to room temperature at a cooling rate of 10-80 ℃/h for 32 hours to obtain Tb with the size of 20mm multiplied by 23mm (equal diameter part)₉La₁(SiO₄)₆O₃A crystal having a Verdet constant at 633nm of about-243 rad/Tm.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.