CN115157110A

CN115157110A - Method for improving surface quality of cesium iodide flexible crystal

Info

Publication number: CN115157110A
Application number: CN202211069284.0A
Authority: CN
Inventors: 吴泓澍; 顾青华; 朱寿政
Original assignee: Jiangsu Institute Of Advanced Inorganic Materials; Shanghai Institute of Ceramics of CAS
Current assignee: Jiangsu Institute Of Advanced Inorganic Materials; Shanghai Institute of Ceramics of CAS
Priority date: 2022-09-02
Filing date: 2022-09-02
Publication date: 2022-10-11
Anticipated expiration: 2042-09-02
Also published as: CN115157110B

Abstract

The invention provides a method for improving the surface quality of a cesium iodide flexible crystal. The method takes physical characteristics and crystallization habits of cesium iodide crystals into consideration, adopts low-viscosity methyl silicone oil as a solution medium and specific corundum micro-powder as an abrasive to prepare a suspension according to a certain proportion, sequentially grinds and polishes the cesium iodide crystals on a hard disk and a floppy disk according to the order of the abrasive granularity from coarse to fine, and cleans the last crystal face by tetraethoxysilane to form a layer of hydrophobic protective film with very thin thickness. The whole process comprises the main procedures of directional cutting, grinding, polishing, cleaning and the like of crystals. The method can be applied to polishing of flexible and deliquescent crystals, has good operability, and overcomes the difficulty caused by the characteristics of low hardness, easy deliquescence, easy deformation, easy scratching and the like to polish the crystals. The cesium iodide crystal obtained by polishing has an optical-grade surface, high light transmittance, high energy resolution and good deliquescence resistance, and can be used as an electromagnetic energy meter in high-energy physics.

Description

Method for improving surface quality of cesium iodide flexible crystal

Technical Field

The invention belongs to the field of crystal polishing processes, particularly relates to a surface grinding and polishing process for a cesium iodide crystal which is difficult to polish and has the characteristics of softness, plasticity, low hardness, high deliquescence and the like, and particularly relates to a method for improving the surface quality of the cesium iodide flexible crystal.

Background

Cesium iodide crystals are a very typical inorganic scintillation crystal. According to different doping ions, the chemical formulas of the cesium iodide ion source can be further divided into three types, namely thallium (Tl) activation, sodium (Na) activation and pure cesium iodide, and the three types are CsI (Tl), csI (Na) and CsI respectively. CsI (Tl) and CsI (Na) have high luminescence efficiency and are widely used in various radiation detectors. Pure CsI crystals are considered fast-emitting scintillators due to the presence of a fast-emitting component with a decay time of 10ns, and are used in electromagnetic energy converters in high-energy physics.

Scintillation light emitted by the cesium iodide crystal under the excitation of the particles must be transmitted through the crystal surface to be collected by the photodetector, but only a small part of the light emitted from the luminescence center directly enters the photodetector along the shortest path, and the majority of the light enters the photodetector after being reflected for multiple times by the crystal surface. The rough surface causes diffuse scattering of the scintillation light, thereby reducing the collection efficiency of the detector for the scintillation light and prolonging the decay time of the light. In order to improve the photon collection efficiency and the photoelectric conversion efficiency, the crystal surface must be as flat and smooth as possible and stable in the atmospheric environment for a long period of time.

The loss caused by the rough surface is not so significant in the final light collection for crystals with high light output because of its low proportion, but for crystals with inherently very low light output like pure cesium iodide, the loss caused by the rough surface is so high in proportion that it has a large effect on the test results. Therefore, to improve the optical detection efficiency of the crystal, the optical loss at the crystal surface must be reduced; to reduce the optical loss at the crystal surface, it is necessary to reduce the roughness of the crystal surface, i.e., to improve the polishing quality of the cesium iodide crystal surface.

Conventional polishing techniques are mechanical polishing, chemical polishing and mechanical-chemical polishing. However, these methods have difficulty in obtaining a good effect on cesium iodide crystals.

First, cesium iodide crystals are relatively deliquescent materials that have a solubility in water at 20 ℃ of up to 74 g/100 g water and are susceptible to moisture absorption in atmospheric conditions and surface erosion. It has been reported in the literature (Triloki, nuclear Instruments and Methods in Physics Research, 2012, A695: 279-282) that after a cesium iodide film is exposed to air at a humidity of 60. + -. 5% for 24 hours, the grain size increases by three times and the luminous efficiency decreases by 30%. Thus, deliquescence is extremely disadvantageous for obtaining a high quality crystal surface.

Secondly, the mechanical processing performance of the cesium iodide crystal is poor in specific valence, and the cesium iodide crystal is not a brittle crystal but a plastic crystal and has low hardness (the Mohs hardness is only 1.3, and the Vickers hardness is 7-9kg/mm ² ) And is soft and not chipped but deformed after being impacted by an external force. The conventional polishing method, even a very gentle operation, leaves scratches or holes on the crystal surface, resulting in a large roughness of the crystal surface, and thus it is difficult to obtain an optical-grade surface.

In order to solve the problem of difficult polishing of cesium iodide crystals, detailed experimental research on the surface polishing process of thallium-doped cesium iodide and pure cesium iodide crystals was carried out by Ukrainian academy of sciences scintillation material research institute internationally authoritative to the growth and processing of cesium iodide crystals, and 7 different polishing materials and methods were tried before and after, wherein the liquid medium used was methanol, ethylene glycol, organosiloxane, ethyl tetraacetate, oligomeric dimethylsiloxane and the like, and the abrasive used was zinc oxide (ZnO), silicon oxide (SiO) and the like ₂ ) Corundum (Al) ₂ O ₃ ) And diamond powder and the like (Yu.T.Vydai, et al.Stablility of metrological characteristics of CsI: tl detectors determining the surface treatment methods, instruments and ExperimentalTechniques, 2006,49, 314-317), through experimental comparison, it is finally found that the solid-liquid mixture composed of the siloxane-tetraethoxysilane-ethanol-silicon oxide super dispersant prepared by the sol-gel method and the fused corundum powder as the abrasive material grinds and polishes the light-emitting surface of the CsI (Tl) crystal, so that the non-uniformity parameter between the light output and the excitation energy of the crystal is increased from 35% during fine grinding to 7%, and the performance is obviously improved. However, the method needs to prepare a dispersant with complex components by a sol-gel method, the process is complicated and the operation difficulty is high, the method needs to use a plurality of organic solvents, cross contamination is easy to cause on the surface of the crystal, great trouble is brought to surface cleaning, and the organic solvents can bring certain environmental pollution.

In 2017, shenyang university (Yinyong et al, shenyang university report, 2017, 77-80) utilizes the deliquescence of CsI (TI) crystals and adopts a method of hydrolysis polishing and mechanical polishing, and by changing and adjusting the proportion, the rotating speed, the pressure and the like of polishing solution, an ideal processing surface can be obtained when the mechanical action and the hydrolysis action are balanced. However, cesium iodide crystals are deliquescent in nature, so that some hydrolysis must occur when water comes into contact with the crystal surface, and this process is greatly affected by the water content and the duration of action, and is difficult to control precisely. Once the dissolution is excessive, not only the surface quality is damaged, but also the machined size of the crystal is out of the allowable tolerance range, resulting in crystal rejection and thus poor operability in actual work. In addition, trace amounts of moisture inevitably remain after the surface of the crystal is polished, and the moisture gradually erodes the surface of the crystal, reducing the quality and durability of the crystal, and shortening the service life of the product.

Disclosure of Invention

The invention aims to overcome the defects that the prior art has few feasible technologies suitable for high-quality polishing of flexible and deliquescent crystals and the prior grinding and polishing technologies have complicated processes, large environmental hazards, difficult control of a hydrolysis process and the like, and the invention seeks a polishing method which is convenient to operate, easy to control, small in environmental hazards and capable of obtaining an excellent polishing effect.

In order to achieve the above purpose, the invention provides a set of grinding, polishing and cleaning methods which are specially used for flexible and deliquescent crystals and are more suitable for practical operation, based on the physical characteristics and crystallization habits of cesium iodide crystals, starting from solution media, abrasive types and granularity, polishing direction, surface treatment and the like, and can overcome the difficulty caused by low hardness, deliquescence, deformation and scratching of the crystals and the like in the crystal polishing, obtain the surface of an optical grade crystal and obtain excellent scintillation property. The specific contents are as follows:

the cesium iodide crystal blank is firstly cut into a preset size on an excircle cutting machine, the verticality and the parallelism among all surfaces are ensured, 0.2 mm of polishing allowance is reserved for each surface, and the cutting speed is 75-400r/min.

And (2) grinding the cut crystal by using a plane grinder by taking the (110) crystal face of the cesium iodide crystal as a light-emitting face to ensure that the parallelism, the verticality, the face included angle and the edge included angle among all the surfaces meet the product index requirements.

The methyl silicone oil with low viscosity is used as a solution medium, and the viscosity of the methyl silicone oil is between 350 and 500 CS.

The fused corundum powder is used as an abrasive, the diameter of abrasive particles is W20-W2.5 microns, and the maximum size of the particles in each abrasive is not more than 1.4 times of the average size of the particles.

The solution medium and the grinding material are mixed according to the following ratio of methyl silicone oil: corundum powder =80, and the mass ratio of the corundum powder to the corundum powder is 20-70.

The crystal surface is ground by using silicate glass or ceramic as a hard grinding disc, a thin silk soft disc covered is used as a polishing base surface, the polishing disc is rotated at a constant speed, and the rotation speed of the grinding disc is 20 to 40 revolutions per minute.

The grinding and polishing processes adopt suspensions, and the particle size of the grinding materials is in order from coarse to fine. The grinding process adopts corundum powder suspension liquid with the granularity of W14-W20 microns, and the polishing process adopts W2-W5 fine-grain corundum powder suspension liquid. And respectively uniformly spraying the suspension on a hard disk and a floppy disk to carry out grinding and polishing operations.

Between the crystal face grinding and polishing processes or when the suspensions with different particle sizes are replaced, the crystal surface processed in the previous process needs to be cleaned by aviation kerosene so as to ensure that the crystal surface has no coarse-particle abrasive material remained in the previous process.

After polishing, the surface of the crystal is cleaned by tetraethoxysilane, so that a layer of hydrophobic protective film with very thin thickness is formed on the surface of the crystal, the direct contact between the surface of the crystal and air is isolated, and the corrosion of moist air to the surface of the crystal is avoided.

The whole operation process of the method is carried out in a dry environment with the humidity of less than 50 percent so as to prevent the erosion of the surface of the crystal by moist air.

Advantageous effects

Aiming at the practical problems of low hardness, low compressive strength, small yield stress, easy plastic deformation, easy deliquescence and the like of cesium iodide crystals which are not beneficial to polishing, the invention provides a novel grinding and polishing method, which can obtain an optical-grade polished surface with extremely low roughness by determining (110) crystal face polishing and matching with a special suspension liquid and comprehensively optimizing the technical details of the polishing process.

The polishing method provided by the invention is simple and convenient to operate, and the used polishing medium is only methyl silicone oil, so that the cross contamination and the trouble brought to cleaning caused by using various organic solvents are avoided; the polishing medium acts on the low-index crystal face of cesium iodide (110), so that a high-quality crystal face with high smoothness is formed. In addition, the tetraethoxysilane medium for final treatment of the crystal surface has hydrophobic property, so that the polished surface can be protected from erosion of humid air in the service process, the quality stability of the crystal is greatly enhanced, and the service life of the crystal is greatly prolonged.

Compared with the thallium-doped cesium iodide crystal obtained by the conventional grinding and polishing method, the method of the invention has the advantages that the optical transmittance at 550nm is improved from 50% to 70% ¹³⁷ The energy resolution of the Cs emitted by 662keV gamma ray under excitation is improved from 10.2 percent to 9.0 percent, and meanwhile, the deliquescence resistance of the crystal under the air environment is also obviously improved.

Compared with the pure cesium iodide crystal of the research institute of scintillation materials of Ukrainia academy of sciences, the pure cesium iodide crystal obtained by the polishing method has better energy resolution, and the average energy resolution is improved to 35.2% from 41%.

Drawings

FIG. 1 is a pictorial view of a polished interface obtained by polishing in accordance with one embodiment.

FIG. 2 is a physical diagram of a polished interface obtained by polishing according to comparative example one.

FIG. 3 is a transmission spectrum of a crystal polished in example one and comparative example one.

FIG. 4 shows the crystals obtained by polishing in example one and comparative example one ¹³⁷ And emitting a multichannel energy spectrum under the excitation of gamma rays by Cs.

FIG. 5 is a physical diagram of a pure cesium iodide crystal obtained by polishing in example two.

FIG. 6 is a multi-channel energy spectrum of pure cesium iodide crystals obtained by polishing in example two at different positions in the long axis direction.

FIG. 7 is a multi-channel energy spectrum of pure cesium iodide crystals at different positions along the long axis of a scintillation material institute of Ukrainian academy of sciences.

Detailed Description

The invention is further illustrated by the following specific examples, which are illustrative and intended to illustrate the problem and explain the invention, but not limiting.

The polishing method of the cesium iodide crystal provided by the invention comprises the following four steps: cutting, grinding, polishing and cleaning.

1. Directional cutting of crystals

And (3) orienting the crystal by using an X-ray orientation instrument, and selecting a (110) crystal face as a light-emitting face of the crystal.

The crystal is cut by selecting excircle cutting or inner circle cutting according to the size of the crystal, and a cutting blade for cutting is generally made of a diamond composite material.

The cesium iodide crystal to be cut is preferably fixed on a cutting machine by a cold glue fixing method. In order to avoid cracking or surface damage due to mechanical shock during crystal processing, cutting at low speed is necessary. The standard cutting speed is 75 to 400 rpm, preferably 200 rpm.

2. Crystal grinding

And (3) grinding the cesium iodide crystals on a surface grinding machine to ensure that the parallelism and the verticality among all planes meet the requirement of +/-0.02.

During grinding, suspension liquid prepared by mixing methyl silicone oil and W20-W14 corundum powder is used as a grinding medium. The maximum size of the particles in the abrasive should not be more than 1.4 times the average size of the particles, otherwise scratches are easily generated during grinding.

3. Crystal polishing

Uniformly mixing low-viscosity methyl silicone oil (the viscosity is 350-500 CS) and corundum powder with the granularity of W2-W5 according to the mass ratio of methyl silicone oil to corundum powder = 20 to prepare a suspension as a polishing medium.

Hard silicate glass is used as a grinding disc, thin silk is used as polishing cloth for covering the surface of the grinding disc, polishing media are uniformly sprayed on the polishing disc, and the polishing disc is rotated at a constant speed to polish the surface of the cesium iodide crystal.

The size of the suspended particles in the polishing medium should be smaller than the size of the suspended particles in the grinding medium.

4. Crystal cleaning

Between the completion of crystal face grinding and rough polishing, and between grinding, rough polishing and fine polishing, the crystal surface must be cleaned by aviation kerosene to ensure that no coarse grain abrasive powder remains on the crystal surface.

The surface of the polished crystal needs to be cleaned by tetraethoxysilane, so that a layer of hydrophobic protective film with very thin thickness is formed on the surface of the crystal, the direct contact between the surface of the crystal and air is isolated, and the corrosion of moist air to the surface of the crystal is avoided.

The final polished interface cleaning operation is performed in a dry environment with a humidity of less than 50%.

Example one

(1) The thallium-doped cesium iodide crystal (CsI: tl) was oriented using an X-ray crystal orienter. According to bragg equation 2dsin θ = λ (d is a interplanar distance, λ is a wavelength of X-rays, and θ is a diffraction angle), a crystal plane in which a strong diffraction peak appears in a direction of the diffraction angle 2 θ = 27.59 ° is a (110) plane of the cesium iodide crystal. And cutting a cylindrical thallium-doped cesium iodide crystal blank into a phi 66X 62 mm cylindrical thallium-doped cesium iodide crystal by using an external circular cutting machine, and ensuring that the long axis of the cylinder is vertical to the bottom surface of the cylinder.

(2) Taking low-viscosity methyl silicone oil as a solution medium, taking W20 corundum powder as an abrasive, uniformly mixing the solution medium and the abrasive according to the weight ratio of methyl silicone oil to corundum powder =80, uniformly spreading a suspension prepared by uniformly mixing on a grinding disc, and grinding the surface of a crystal on a hard grinding disc at the rotation speed of 20 to 40 revolutions per minute.

(3) And after the grinding is finished, cleaning the crystal face after grinding by using methyl silicone oil without polishing powder as a medium to ensure that no W20 corundum powder is left on the surface.

(4) Methyl silicone oil and corundum micro powder with the particle size of W3 are uniformly mixed according to the proportion (mass ratio) of 70.

(5) Hard glass is used as a grinding disc, thin silk is used as polishing cloth in a covering mode, and polishing media are sprayed on the polishing cloth.

(6) And (4) placing the cleaned cesium iodide crystal surface in the step (3) on polishing cloth, and polishing the crystal surface by adjusting the rotation speed of a grinding disc to be 20-40 r/min.

(7) And cleaning the surface of the polished crystal by using tetraethoxysilane, forming a layer of hydrophobic protective film with a very thin thickness on the surface of the crystal, and preventing the surface of the crystal from directly contacting with air so as to avoid the corrosion of the moist air on the surface of the crystal.

Comparative example 1

(1) Cutting a cylindrical thallium-doped cesium iodide crystal blank into a phi 66X 62 mm cylindrical thallium-doped cesium iodide crystal by using an external circle cutting machine, and ensuring that the long axis of the cylinder is vertical to the bottom surface of the cylinder.

(2) And (3) grinding the cylindrical surface of the cut cylindrical thallium-doped cesium iodide crystal on a surface grinding machine, and finely grinding the bottom surface by adopting W14 corundum powder, wherein the grinding disc rotating speed is 20-40 revolutions per minute.

Performance testing

Practice ofExample a polished interface was obtained as shown in figure 1. The interface obtained in comparative example one is shown in fig. 2. Further, the light transmittance of the crystals obtained in the first example and the first comparative example was measured by a spectrophotometer, as shown in FIG. 3, in which curve a corresponds to example one and curve b corresponds to comparative example one. The results show that the light transmittance of the crystal obtained in example one is significantly higher than that of comparative example one, and the light transmittance is increased from 50% to 70% at 550 nm. Further, with radioactive isotopes ¹³⁷ The 662keV gamma ray emitted by Cs is used as an excitation source, and the multi-channel energy spectra of the crystals obtained in the first example and the first comparative example are respectively tested, as shown in FIG. 4, wherein curve a corresponds to the first example and curve b corresponds to the first comparative example. The results show an increase in energy resolution from 10.2% to 9.0% at 662keV gamma ray excitation. Meanwhile, the deliquescence resistance of the crystal in the air environment is also obviously improved.

Example two

(1) And (3) orienting the pure cesium iodide crystal blank by using an X-ray orientation instrument, wherein a crystal face with a strong diffraction peak in the direction of a diffraction angle 2 theta = 27.59 degree is a (110) face of the pure cesium iodide crystal according to a Bragg equation 2dsin theta = lambda (d is a crystal face interval, lambda is the wavelength of X-rays, and theta is a diffraction angle), and the (110) crystal face is selected as a light-emitting face.

(2) And cutting out a 30X 200 mm rectangular columnar pure cesium iodide crystal from a pure cesium iodide crystal blank grown by a Bridgman method by using an external circle cutting machine, wherein the long axis of the pure cesium iodide crystal is vertical to the bottom surface of the square. And it is ensured that the tolerance in the 200 mm direction after polishing is ± 0.1 mm and the tolerance in the 30 mm direction is ± 0.05 mm.

(3) A suspension formed by uniformly mixing W14 (with the granularity of 14 mu m) corundum powder and methyl silicone oil with the viscosity of 400 CS is used as a grinding medium, 6 planes of 30 x 200 mm pure cesium iodide crystals are ground on a plane grinding machine, and the rotation speed of the grinding machine is controlled to be 20 to 40 revolutions per minute.

(4) And cleaning the ground crystal surface by aviation kerosene to remove polishing powder remained on the crystal surface.

(5) Using methyl silicone oil with the viscosity of 400 CS as a solution medium, using corundum micropowder with the particle size of 2.5 μm (W2.5) as an abrasive, and mixing the solution medium and the corundum micropowder according to the weight ratio of the methyl silicone oil: corundum powder =80 (mass ratio), and the mixture is uniformly mixed to prepare suspension, the suspension is sprayed on a soft grinding disc, six planes (2 end faces of 30 × 30 mm and 4 large faces of 30 × 200 mm) of a 30 × 30 × 200 mm rectangular pure cesium iodide crystal are sequentially placed on the grinding disc covered with thin silk polishing cloth, the rotation speed of the grinding disc is controlled at 20 to 40 revolutions per minute, and six surfaces of the cesium iodide crystal are sequentially polished.

(6) And cleaning the polished crystal surface by using tetraethoxysilane, and forming a layer of hydrophobic protective film with a very thin thickness on the crystal surface to prevent the crystal surface from directly contacting air. The resulting crystals are shown in FIG. 5.

Performance test

Coating 30X 200 mm pure cesium iodide crystal with polytetrafluoroethylene (Teflon) high reflection film, leaving only one end face of 30X 30 mm exposed, coupling with photomultiplier tube, and coating with a transparent coating ¹³⁷ The 662keV gamma ray emitted by the Cs is an excitation source, the time gate width is 200ns, and a gamma ray multi-channel energy spectrum is tested along the long axis direction of the crystal at intervals of 25 mm, and the result is shown in FIG. 6 (in the figure, E.R. represents energy resolution, and the smaller the number, the better the resolution is). The energy resolution of the full energy peak of the corresponding spectrum of 7 points was read out, and the average energy resolution was found to be 35.2%. Under the same conditions, pure cesium iodide crystals having similar sizes from research institute of scintillation material of ukrainian academy of sciences were subjected to energy resolution test, and the result is shown in fig. 7, and the average energy resolution was found to be 41%.

By comparison, the pure cesium iodide crystal of the research institute of scintillating materials of Ukrainian academy of sciences adopts a polishing medium containing a super dispersant, so that the nonuniformity parameter between the light output and the excitation energy of the crystal reaches 7%, and correspondingly, the average energy resolution reaches 41%.

The above embodiments are provided for illustrative purposes, so that those skilled in the art can understand the technical idea and features of the present invention and implement the invention, and the protection scope of the present invention is not limited thereby. All equivalent changes and modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.

Claims

1. A method for improving the surface quality of a cesium iodide flexible crystal is characterized by comprising the following steps: selecting a specific crystal face of a cesium iodide crystal for grinding and polishing, wherein the specific crystal face is a (110) crystal face; the grinding medium used in grinding and the polishing medium used in polishing are both suspension containing corundum powder and low-viscosity methyl silicone oil; the average grain size of the corundum powder in the polishing medium is smaller than that of the corundum powder in the grinding medium, the ratio of the maximum grain size to the average grain size of the corundum powder in the grinding medium is not more than 1.4, and the ratio of the maximum grain size to the average grain size of the corundum powder in the polishing medium is not more than 1.4; the mass ratio of the low-viscosity methyl silicone oil to the corundum powder in the grinding medium and the polishing medium is in the range of 80-70.

2. The method for improving the surface quality of a cesium iodide flexible crystal according to claim 1, characterized in that: determining the direction of a (110) crystal face of the cesium iodide crystal by using an X-ray orientation instrument; according to the bragg equation 2dsin theta = lambda, the crystal face with a strong diffraction peak in the direction of the diffraction angle 2 theta = 27.59 degrees is the (110) face of the cesium iodide crystal; in the Bragg equation, d is the interplanar spacing, λ is the wavelength of the X-ray, and θ is the diffraction angle.

3. The method of improving the surface quality of a flexible crystal of cesium iodide as claimed in claim 1, wherein: and after polishing, cleaning the polished surface by using tetraethoxysilane, washing off particles attached to the polished surface, and reacting with the polished surface to form a hydrophobic protective film layer.

4. The method of improving the surface quality of a flexible crystal of cesium iodide as claimed in claim 1, wherein: after the completion of the grinding and before the start of polishing, the surface of the cesium iodide crystal was cleaned with aviation kerosene to remove residual particulate matter.

5. The method of improving the surface quality of a flexible crystal of cesium iodide as claimed in claim 1, wherein: the method is carried out in a dry environment with a humidity of less than 50% to prevent erosion of the crystal surface by moist air.

6. The method of improving the surface quality of a flexible crystal of cesium iodide as claimed in claim 1, wherein: the grinding disc adopted in the grinding process is a hard glass disc or a ceramic disc, and the soft disc covered with silk cloth is adopted in the polishing process.

7. The method for improving the surface quality of a cesium iodide flexible crystal according to claim 1, characterized in that: the low-viscosity methyl silicone oil is methyl silicone oil with the viscosity of 350 to 500 CS.

8. The method for improving the surface quality of a cesium iodide flexible crystal according to claim 1, characterized in that: in the grinding medium, the granularity of the corundum powder is not more than the range of W20-W14, and in the polishing medium, the granularity of the corundum powder is not more than the range of W5-W2.

9. The method of improving the surface quality of a flexible crystal of cesium iodide as claimed in claim 1, wherein: the cesium iodide crystal comprises a pure cesium iodide crystal and a thallium-doped cesium iodide crystal.