Preparation method of optical isotropic wide-band-gap optical crystal cesium fluosilicate and application of optical isotropic wide-band-gap optical crystal cesium fluosilicate in optical window

Abstract

The invention provides a preparation method of a wide-band-gap optical crystal cesium fluosilicate and application of deep ultraviolet of the wide-band-gap optical crystal cesium fluosilicate in an optical window device. The chemical formula of the cesium fluosilicate crystal is Cs2SiF6, the crystal has a symmetric center and belongs to a cubic system, the space group is # imgabs0 # (No.225), the unit cell parameters are # imgabs1 # alpha = beta = gamma = 90 degrees, Z = 4, and the unit cell volume is # imgabs2 #, the crystal is prepared from Na2SiF6 and CsCl as raw materials through a hydrothermal cation complete replacement crystallization method, and the method is easy to operate, clean, environmentally friendly, low in cost and suitable for industrial production. The method has the advantages of short time consumption, large crystal size and high single crystal quality, and can be used for preparing large-size and high-quality cesium fluosilicate single crystals in a large scale. The crystal has a theoretical band gap of 9.329 eV, corresponds to a deep ultraviolet absorption edge of 133 nm, has a transmittance range of 133 nm to near-infrared light, has good mechanical properties, is suitable for optical window devices of 133 nm to near-infrared light, and is especially suitable for deep ultraviolet optical window devices of more than 133 nm.

Description

Technical Field

[0001] The invention belongs to the technical field of optical crystal materials, and specifically relates to a method for preparing an optically isotropic, centrosymmetric, wide-bandgap cesium fluorosilicate crystal, and application of the crystal in optical window devices, especially in deep ultraviolet window devices. Background Art

[0002] Deep UV window devices have shown important value in many fields, including: wafer defect detection, accurate identification of surface impurities and defects, combined with KBe 2 BO 3 F 2 The detection sensitivity of the photoelectron spectrometer prepared by crystal is more than 10 times higher than that of traditional technology; the electron energy level analysis can directly observe the energy gap of semiconductor materials, the distribution of electron momentum and other microscopic characteristics through the deep ultraviolet laser photoelectron spectrometer. It plays a vital role in spectral analysis, optical information processing and communication, as well as biology and medicine. At the same time, its high-energy photon characteristics, radiation resistance and precision optical performance also provide key support for modern military technology. Continuously improving and perfecting the performance of deep ultraviolet window devices has far-reaching and significant significance for the development of deep ultraviolet optical systems.

[0003] The band gap of cesium fluorosilicate is 9.329eV, and its corresponding cutoff edge is 133nm, which can achieve deep ultraviolet laser output below 140nm. In the article published by John A.Skarulis and Paul Kissinger in 1965, cesium fluorosilicate was prepared from cesium chloride and fluorosilicic acid. The method requires stirring, filtering, repeated washing, air drying, titration and other steps to prepare cesium fluorosilicate. The method is highly polluting, the process is complicated, the time is long, the cost is high, and the size of the grown crystal is small. This patent adopts the hydrothermal cation complete replacement crystallization method to grow cesium fluorosilicate. The method is simple to operate, clean and environmentally friendly, low cost, short time consumption, large crystal size, high single crystal quality, and can prepare large-size, high-quality cesium fluorosilicate single crystals in large quantities, providing high-quality materials for deep ultraviolet window devices. Summary of the invention

[0004] The object of the present invention is to provide a cesium fluorosilicate optical crystal.

[0005] Another object of the present invention is to provide a method for preparing cesium fluorosilicate optical crystal.

[0006] Another object of the present invention is to provide uses of cesium fluorosilicate optical crystals.

[0007] The cesium fluorosilicate wide band gap optical crystal described in the present invention has a chemical formula of Cs 2 SiF 6, the crystal has a symmetry center, belongs to the cubic system, and the space group is The unit cell parameters are α=β=γ=90°,Z=4, the unit cell volume is

[0008] Growth of Cs by Hydrothermal Cation Replacement Crystallization 2 SiF 6 Crystallization, comprising the following steps:

[0009] a.Na 2 SiF 6 The two raw materials are mixed in a molar ratio of 1:2.5 to 6.6 with CsCl. A certain mass of the two raw materials is weighed respectively, and CsCl is in excess to ensure that the cation is completely replaced and the crystallization is fully carried out.

[0010] b. Put the weighed raw materials into the PTFE liner, add 5-10ml of deionized water, cover the liner, put the PTFE liner into the 304 stainless steel shell and tighten it.

[0011] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 80-240°C at 0.8-2°C / min, and keep it warm for 24h-96h.

[0012] d. Cool down at a rate of 30°C / h. After cooling to room temperature, open the polytetrafluoroethylene liner, rinse the product with deionized water, and dry the washed crystal product in a drying oven to obtain Cs 2 SiF 6 The yield of the crystals was 15.4% to 24.1% based on cesium ions.

[0013] The use of the cesium fluorosilicate crystal deep ultraviolet window is used to prepare a deep ultraviolet optical window device, characterized in that the incident laser passes through the cesium fluorosilicate deep ultraviolet window device to obtain a transmitted laser, and the device is suitable for a light transmission band with a wavelength higher than 133nm.

[0014] The Cs prepared by the present invention 2 SiF 6 Crystals have the following properties:

[0015] 1. Crystal structure: space group is Central symmetry.

[0016] 2. Optical band gap: The band gap is 9.329eV, with high optical transparency from deep ultraviolet to near infrared.

[0017] 3. Refractive index: In the range of deep ultraviolet light and near infrared light, the refractive index in each direction has the following relationship: n (100) =n (010) ≈n (001)That is, along all directions, its refractive index values ​​are equal or very close, and it has strong optical isotropy, which can ensure that when the crystal is used to prepare a window device, the propagation direction, polarization state, and propagation speed of the incident light and the transmitted light are consistent, ensuring clear imaging of the optical imaging system; avoiding polarization mode dispersion in signal transmission and improving signal stability.

[0018] 4. Stability: good mechanical properties and easy to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 For the present invention Phase Cs 2 SiF 6 Schematic diagram of the crystal structure, showing the projection of Cs, Si, and F along the a direction.

[0020] Figure 2 For the present invention Phase Cs 2 SiF 6 Schematic diagram of the crystal structure, showing the projection of Cs, Si, and F along the b direction.

[0021] Figure 3 For the present invention Phase Cs 2 SiF 6 Schematic diagram of X-ray diffraction of a single crystal after it is ground into powder.

[0022] Figure 4 For the present invention Phase Cs 2 SiF 6 Schematic diagram of energy bands calculated by crystal theory.

[0023] Figure 5 P3 in the ICSD standard database 1 21 phase SiO 2 Schematic diagram of energy bands calculated by crystal theory.

[0024] Figure 6 Cs growth by hydrothermal cation replacement crystallization 2 SiF 6 Actual picture of the crystal taken with a tube microscope.

[0025] Figure 7 is the Cs prepared in Example 1-12 2 SiF 6 Schematic diagram of the crystal's deep ultraviolet window device.

[0026] Figure 8 For the present invention Phase Cs 2 SiF 6 Schematic diagram of the theoretical refractive index of crystals. DETAILED DESCRIPTION

[0027] The technical content, achieved objectives and effects of the present invention are described in detail below in conjunction with the implementation and drawings.

[0028] Example 1

[0029] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0030] a. Mix in a molar ratio of 1:5, weigh 0.47g Na 2 SiF 6 and 3.36 g CsCl.

[0031] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 5ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0032] c. Place the hydrothermal autoclave in a step temperature-controlled forced air drying oven, raise the temperature to 240°C at 2°C / min, and keep it warm for 72 hours.

[0033] d. The temperature was lowered at a rate of 30°C / h. After cooling to room temperature, the polytetrafluoroethylene liner was opened, the product was rinsed with deionized water, and the washed crystal product was placed in an oven to dry to obtain cesium fluorosilicate crystals with a yield of 17.2% based on cesium ions.

[0034] Example 2

[0035] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0036] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:3.3, weigh 0.7g Na 2 SiF 6 and 3.36 g CsCl.

[0037] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 5ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0038] c. Place the hydrothermal autoclave in a step temperature-controlled forced air drying oven, raise the temperature to 240°C at a rate of 1.5°C / min, and keep warm for 72 hours.

[0039] d. Cooling was performed at a rate of 30°C / h. After cooling to room temperature, the polytetrafluoroethylene liner was opened, the product was rinsed with deionized water, and the washed crystal product was placed in an oven to dry to obtain cesium fluorosilicate crystals with a yield of 21.9% based on cesium ions.

[0040] Example 3

[0041] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0042] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:3.3, weigh 0.7g Na 2 SiF 6 and 3.36 g CsCl.

[0043] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 10ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0044] c. Place the hydrothermal autoclave in a step temperature-controlled forced air drying oven, raise the temperature to 240°C at 1°C / min, and keep it warm for 96 hours.

[0045] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 21.4% based on cesium ions.

[0046] Example 4

[0047] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0048] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:2.5, weigh 0.47g Na 2 SiF 6 and 1.68 g CsCl.

[0049] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 5ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0050] c. Place the hydrothermal autoclave in a step temperature-controlled forced air drying oven, raise the temperature to 240°C at 2°C / min, and keep it warm for 72 hours.

[0051] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 18.2% based on cesium ions.

[0052] Example 5

[0053] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0054] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:6.6, weigh 0.35g Na 2 SiF 6 and 3.36CsCl.

[0055] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 5ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0056] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 230°C at 0.8°C / min, and keep it warm for 96 hours.

[0057] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 20.3% based on cesium ions.

[0058] Example 6

[0059] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0060] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:5.3, weigh 0.45g Na 2 SiF 6 and 3.36 g CsCl.

[0061] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 6ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0062] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 220°C at 0.8°C / min, and keep it warm for 72 hours.

[0063] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, rinsing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 24.1% based on cesium ions.

[0064] Example 7

[0065] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0066] a. Press Na 2 SiF 6:CsCl molar ratio is 1:4.5, weigh 0.35g Na 2 SiF 6 and 2.27 g CsCl.

[0067] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 8ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0068] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 80°C at 1.2°C / min, and keep it warm for 36 hours.

[0069] d. The temperature was lowered at a rate of 30°C / h. After cooling to room temperature, the polytetrafluoroethylene liner was opened, the product was rinsed with deionized water, and the washed crystal product was placed in an oven to dry to obtain cesium fluorosilicate crystals with a yield of 15.4% based on cesium ions.

[0070] Example 8

[0071] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0072] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:5, weigh 0.35g Na 2 SiF 6 and 2.52 g CsCl.

[0073] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 7ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0074] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 90°C at 1.4°C / min, and keep it warm for 24 hours.

[0075] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 16.4% based on cesium ions.

[0076] Example 9

[0077] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0078] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:6.6, weigh 0.35g Na 2 SiF 6and 3.36 g CsCl.

[0079] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 5ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0080] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 120°C at 1.5°C / min, and keep it warm for 24 hours.

[0081] d. The temperature was lowered at a rate of 30°C / h. After cooling to room temperature, the polytetrafluoroethylene liner was opened, the product was rinsed with deionized water, and the washed crystal product was placed in an oven to dry to obtain cesium fluorosilicate crystals with a yield of 17.1% based on cesium ions.

[0082] Example 10

[0083] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0084] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:4, weigh 0.45g Na 2 SiF 6 and 2.69 g CsCl.

[0085] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 8ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0086] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 130°C at 1.8°C / min, and keep it warm for 48 hours.

[0087] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 17.3% based on cesium ions.

[0088] Embodiment 11

[0089] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0090] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:5, weigh 0.5g Na 2 SiF 6 and 3.56 g CsCl.

[0091] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 8ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0092] c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 140°C at 1.8°C / min, and keep it warm for 72 hours.

[0093] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 17.5% based on cesium ions.

[0094] Example 12

[0095] Growth of cesium fluorosilicate crystals by hydrothermal cation complete replacement crystallization method:

[0096] a. Press Na 2 SiF 6 :CsCl molar ratio is 1:4, weigh 1.2g Na 2 SiF 6 and 6.85 g CsCl.

[0097] b. Place the weighed raw materials into a 25ml polytetrafluoroethylene liner, then add 10ml deionized water, cover the liner tightly, and place it into the 304 stainless steel shell of the hydrothermal kettle and tighten it.

[0098] c. Place the hydrothermal autoclave in a step temperature-controlled forced air drying oven, raise the temperature to 160°C at 2°C / min, and keep it warm for 96 hours.

[0099] d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, washing the product with deionized water, and drying the washed crystal product in an oven to obtain cesium fluorosilicate crystals with a yield of 22.6% based on cesium ions.

[0100] Example 13

[0101] Accurate calculation of energy bands in cesium fluorosilicate optical crystals:

[0102] Any of 1-12 Cs will be implemented 2 SiF 6 The crystal structure data obtained from the crystal were calculated using the Castep module of Materials studio software in reciprocal space and modulus conservation pseudopotential conditions using the ultra-high precision PEB0 hybrid functional. The calculation results are shown in Figure 4 .

[0103] According to Planck's formula in quantum mechanics, the relationship between the energy E of a photon and its wavelength λ is:

[0104] Cs 2 SiF 6 The theoretical band gap obtained by crystal calculation is 9.329eV, and the corresponding deep ultraviolet cutoff absorption edge is 133nm. However, due to the discontinuity of the electron wave function selected for theoretical calculation, the theoretical band gap is smaller than the actual band gap, and the corresponding deep ultraviolet cutoff edge is larger. The known P3 is derived from the ICSD standard database 1 21 phase SiO 2 The standard crystal structure data file of the crystal, using the same theoretical parameters, is compared with the calculated P3 1 21 phase SiO 2 Crystal band gap, calculated results are shown in Figure 5 The theoretical band gap value is 8.831eV (corresponding to the deep ultraviolet cutoff absorption edge of 140.30nm), while the actual band gap value is 9.00eV (corresponding to the deep ultraviolet absorption edge of 137.67nm). The calculation error is less than 2%, and the calculation result is relatively accurate. 2 SiF 6 The band theory calculations are accurate.

[0105] Embodiment 14

[0106] Deep ultraviolet devices of cesium fluorosilicate crystals:

[0107] The Cs grown in Example 1-12 2 SiF 6 Crystals (maximum size of the grown crystals is greater than 5.5×4.5×1mm 3 ),like Figure 6 As shown, after optical processing, it is used to make a deep ultraviolet window device. The schematic diagram of the deep ultraviolet window device is as follows Figure 7 The incident laser passes through the optically processed cesium fluorosilicate deep ultraviolet device to obtain a transmitted laser, and its transmission wavelength range is 133nm-4000nm.

[0108] Embodiment 15

[0109] Accurate calculation of the refractive index of cesium fluorosilicate deep ultraviolet centrosymmetric wide bandgap optical crystal:

[0110] The crystal structure data obtained from any deep ultraviolet centrosymmetric optical crystal in 1-12 are calculated using the Castap module of Material Studio software in reciprocal space and modulus conservation pseudopotential conditions using the ultra-high precision PBE0 hybrid functional. Figure 8 As shown, Cs 2 SiF 6 The refractive index is n (100) =n(010) ≈n (001) , showing strong optical isotropy, and can achieve efficient laser directional transmission in the 133nm-4000nm band.

Claims

1. A potassium sodium fluorosilicate deep ultraviolet optical crystal, characterized in that: The chemical formula is Cs2SiF6. The crystal has a symmetry center and belongs to the cubic system. The space group is The unit cell parameters are α=β=γ=90°,Z=4, the unit cell volume is 2. The method for preparing the cesium fluorosilicate deep ultraviolet optical crystal according to claim 1, characterized in that: The crystal is crystallized by hydrothermal cation complete replacement method: The hydrothermal cation complete replacement crystallization method for growing Cs2SiF6 crystals comprises the following steps: a. Na2SiF6 and CsCl are mixed in a molar ratio of 1:2.5-6.

6. A certain mass of the two raw materials are weighed respectively, with an excess of CsCl to ensure that the cations are completely replaced and the crystallization is fully carried out. b. Put the weighed raw materials into the PTFE liner, add 5-10ml of deionized water, cover the liner, put the PTFE liner into the 304 stainless steel shell and tighten it. c. Place the hydrothermal kettle in a step temperature-controlled forced air drying oven, raise the temperature to 80-240°C at 0.8-2°C / min, and keep it warm for 24h-96h. d. Cooling at a rate of 30°C / h, opening the polytetrafluoroethylene liner after cooling to room temperature, rinsing the product with deionized water, and drying the washed crystal product in a drying oven to obtain Cs2SiF6 crystals with a yield of 15.4%-24.1% based on cesium ions.

3. The preparation method according to claim 2, characterized in that: The molar ratio of Na2SiF6 to CsCl in step a is that CsCl is in excess, the heating rate is 0.8-2°C / min, and the maximum reaction temperature is 240°C.

4. The cesium fluorosilicate optical crystal prepared as claimed in claim 2, characterized in that: Its theoretical band gap is no less than 9.329 eV, and the corresponding deep ultraviolet absorption edge is 133 nm.

5. The deep ultraviolet optical window device prepared from the cesium fluorosilicate deep ultraviolet optical crystal as claimed in claim 2, characterized in that: The incident laser passes through the cesium fluorosilicate deep ultraviolet window device to obtain the transmitted laser, and the device is suitable for the light transmission band with a wavelength higher than 133nm.

6. The cesium fluorosilicate deep purple window device as claimed in claim 5, wherein the light transmission band covers the range from 133 nm to the near infrared region.

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