Method for identifying crystal boundary of sesquioxide crystal

Abstract

The invention discloses a method for identifying a crystal boundary of a sesquioxide crystal, and belongs to the technical field of crystal detection. According to the invention, a frosted surface with specific roughness (Sa = 0.7-2 [mu] m) is formed by controlling diamond wire cutting or mechanical grinding, so that the grain boundary presents a macroscopic subarea boundary under a bright light source due to light scattering difference. According to the method, rapid identification of the crystal boundary of the sesquioxide crystal is achieved through combination of physical machining and optical observation, chemical corrosion is not needed, operation is easy, the equipment requirement is low, cost is remarkably saved, and dependence on a large precise instrument or a synchrotron radiation light source is eliminated; the detection efficiency is high, detection can be rapidly implemented on the surface of a large-size crystal with naked eyes, and in-situ and real-time observation of a crystal boundary is realized; images are clear and visual, and a reliable basis is provided for directional cutting of a high-quality single crystal area; the method is suitable for various sesquioxide crystals including lutetium oxide, and has high method universality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of crystal detection, and particularly relates to a method for identifying grain boundaries of sesquioxide crystal. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission by the patent applicant or the patent owner that this information forms part of the prior art already known in this field prior to the application of the present application.

[0003] Sesquioxide (such as Lu2O3, Sc2O3, Y2O3) crystals have significant application potential in the fields of laser and scintillator devices due to their high thermal conductivity, low phonon energy and strong crystal field. However, the melting point of such crystals is extremely high, and the thermal gradient is difficult to control stably during crystal growth, which easily forms defects such as grain boundaries and inclusions, seriously affecting the electrical and optical properties. Therefore, developing a method that can quickly and accurately identify grain boundaries is of great significance for evaluating crystal quality and selecting single crystal regions.

[0004] Most of the commonly used grain boundary detection methods require complex sample pretreatment processes, especially chemical etching of the crystal to reveal the grain boundaries. For example, before using X-ray diffraction (XRD), electron backscatter diffraction (EBSD), high-resolution transmission electron microscopy (HRTEM) and three-dimensional X-ray diffraction (3D-XRD) imaging techniques, the sample is usually polished and chemically etched to eliminate surface stress and highlight the grain boundary features. This process is not only tedious and time-consuming, but also introduces surface contamination, changes the structure of the crystal surface layer, and even causes irreversible damage, affecting subsequent processing and performance characterization. In addition, although high-resolution transmission electron microscopy (HRTEM) and other techniques can directly observe grain boundaries, sample preparation is more complex and often requires a combination of focused ion beam (FIB) processing and etching steps, which is costly and has low success rate, making it difficult to apply to rapid screening of large-size crystals.

[0005] Therefore, it is a technical problem to be solved in this field to develop a grain boundary identification method that is simple to operate, low in cost and suitable for wide application. SUMMARY

[0006] In order to solve the problems of the prior art, the purpose of the present application is to provide a method for identifying grain boundaries of sesquioxide crystal. The surface of the processed crystal is placed under bright light, which can quickly reveal the macro position of the grain boundary, and has the advantages of simple operation, low cost, rapid identification, macro-micro combination, and intuitive and reliable results.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows: The first aspect of the present application provides a method for identifying grain boundaries of sesquioxide crystals, comprising: processing the crystal surface to control the roughness (Sa) to be 0.7-2 μm; placing the surface to be measured of the crystal under a light source and shaking, and observing with naked eyes, and the boundary between the light and dark zones is the grain boundary.

[0008] The present application forms a crystal surface with a specific roughness (Sa=0.7-2 μm) by controlling the processing of the crystal surface, so that the grain boundaries show the boundary between the light and dark zones that can be observed with naked eyes under a bright light source due to the difference in light scattering, avoiding the use of complex detection equipment such as TEM and FIB, and being suitable for the rapid identification of grain boundaries of high-melting-point sesquioxide crystals such as Lu2O3, and providing instant guidance for the optimization of crystal growth process.

[0009] In some embodiments of the present application, the method for processing the crystal surface comprises cutting in a direction parallel to the surface to be measured to obtain the sample to be measured.

[0010] In some embodiments of the present application, the cutting is diamond wire cutting, the wire thickness is 0.2-0.35 mm, the cutting line speed is 0.2-0.3 mm / min, and the rotation speed is 260 rps.

[0011] In some embodiments of the present application, the method for processing the crystal surface comprises wet grinding the crystal to be measured to obtain the sample to be measured.

[0012] In some embodiments of the present application, the rotation speed of the wet grinding is 100-200 rpm. In some embodiments of the present application, the particle size of the grinding agent is 1-5 μm.

[0013] In some embodiments of the present application, the grinding agent is a silica abrasive or an alumina abrasive.

[0014] In some embodiments of the present application, the light intensity of the light source is ≥500 lx.

[0015] In some embodiments of the present application, the crystal is a sesquioxide crystal.

[0016] In some embodiments of the present application, the crystal is a sesquioxide crystal, including Lu2O3, Sc2O3, Y2O3 and doped system crystals thereof.

[0017] The present application has the following beneficial effects: The present application provides a method for identifying grain boundaries of sesquioxide crystals, which realizes the rapid identification of grain boundaries of sesquioxide crystals by combining physical and mechanical processing with optical observation. Specifically: 1. No need for chemical corrosion, simple operation and small damage. The method directly obtains a crystal surface with a specific roughness by controlling mechanical processing, completely avoids surface pollution and structure damage caused by traditional chemical corrosion methods, and is a low-destructive grain boundary identification method, which is beneficial to subsequent wafer processing and device preparation.

[0018] 2. Low equipment requirement and significant cost saving. The present application only needs conventional cutting or grinding equipment, and gets rid of the dependence on large and precise instruments such as XRD, EBSD, HRTEM or synchrotron radiation source, greatly reduces the detection cost and threshold, and is more conducive to industrialization promotion and application.

[0019] 3. High detection efficiency, which can realize macroscopic rapid positioning. The present application can rapidly implement detection on a large size crystal surface, realize in-situ and real-time observation of grain boundaries, overcome the limitations of small field of view and slow scanning speed of electron microscopes, and is suitable for rapid screening and regional selection of crystal quality in production line environment.

[0020] 4. The identification result is intuitive and convenient for subsequent processing. The light and dark contrast formed by the difference in crystal plane orientation on the specific rough surface can quickly, clearly and intuitively show the macroscopic position of the grain boundary on the sample surface under naked eye, which is convenient for large-scale screening and preliminary positioning. The image is clear and intuitive, which provides a reliable basis for directional cutting of high-quality single crystal region. The long-time and high-cost scanning or three-dimensional reconstruction time required by traditional electron microscopy or synchrotron radiation method is greatly saved.

[0021] 5. Good universality and repeatability. The method of the present application is based on the identification of the intrinsic anisotropy of the crystal, does not introduce chemical modification, and has stable and reliable results. It is suitable for various sesquioxide crystals including lutetium oxide, and has high method universality. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application and their description serve to explain the present application, and do not constitute an improper limitation of the present application.

[0023] Figure 1 The surface roughness test results of the Lu2O3 crystal sample in Example 1 of the present application.

[0024] Figure 2 The grain boundary photos of the Lu2O3 crystal sample in Example 1 of the present application, and the arrows point to the grain boundaries.

[0025] Figure 3 The boundary area etching morphology graph in the chemical etching-microscopic observation method of Example 1 of the present application.

[0026] Figure 4SEM image of the grain boundary region in the TEM analysis method of Example 1 of the present application.

[0027] Figure 5 SEM image of the TEM sample cross section in the TEM analysis method of Example 1 of the present application.

[0028] Figure 6 High resolution TEM image after the left side of the boundary line is converted to positive in the TEM analysis method of Example 1 of the present application.

[0029] Figure 7 SAED image of the left side region when the left side is converted to positive in the TEM analysis method of Example 1 of the present application.

[0030] Figure 8 SAED image of the two side regions after superposition when the left side is converted to positive in the TEM analysis method of Example 1 of the present application.

[0031] Figure 9 Image after the right side of the boundary line is converted to positive in the TEM analysis method of Example 1 of the present application; wherein (a) is a high resolution TEM image after the right side of the boundary line is converted to positive, (b) is a SAED image of the right side region when the right side is converted to positive, and (c) is a SAED image of the two side regions after superposition when the right side is converted to positive.

[0032] Figure 10 Surface roughness test results of the Lu2O3 crystal sample in Example 2 of the present application.

[0033] Figure 11 Surface roughness test results of the Lu2O3 crystal sample in Comparative Example 1 of the present application.

[0034] Figure 12 Surface roughness test results of the Lu2O3 crystal sample in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0036] Example 1 Identification of grain boundaries in Lu2O3 crystal by diamond wire saw direct face forming method 1. Sample preparation: the Lu2O3 crystal to be tested is cut by a diamond wire saw to obtain a test surface, the wire thickness is 0.35 mm, the cutting speed is 0.25 mm / min, and the rotation speed is 260 rps. A surface optical profilometer device is used to perform roughness testing, and the sample surface roughness Sa is 1.08 μm, as shown in Table 1. Figure 1

[0037] ​2. Grain boundary identification: The sample surface to be tested is placed under bright light and moved left and right. Clear partitioning can be observed with the naked eye, with distinct boundaries, such as… Figure 2 As shown. This boundary is the grain boundary.

[0038] To verify the accuracy of this method, two original methods were used for validation: chemical etching-microscopy and TEM analysis.

[0039] Chemical etching-microscopic observation method: The crystal sample was placed in a 70 wt% phosphoric acid solution and etched at a specific temperature (160℃) for 15 min. After etching, the sample was removed and thoroughly cleaned with anhydrous ethanol and deionized water to remove residual acid. After drying, it was observed under an optical microscope. The boundary zone consisted of densely stacked pits with relatively straight edges, as shown in the image. Figure 3 As shown, the etch pits above the boundary zone exhibit clear equilateral triangles, while the etch pits below the boundary zone present as non-equilateral triangular depressions. The difference in pit morphology on both sides of the boundary indicates different crystal orientations on either side of the boundary, which is a grain boundary. Therefore, the method provided by this invention is accurate and feasible.

[0040] TEM analysis: The chemically etched sample was further cut and thinned using a focused ion beam scanning electron microscope (FIB-SEM). Figure 4 This is a scanning electron microscope schematic diagram of the grain boundary region, where the central bundle-like boundary line corresponds to the boundary of the etch pit after chemical etching. Figure 5 The cross-section of the sample after FIB cutting and thinning is shown. The hole and twisted vortex in the center of the sample are caused by the local stress release during the FIB thinning process. The sample after FIB thinning is placed on a copper grid. A clear boundary line can be clearly observed below the etch pit by TEM. The zone axis

[110] is determined by XRD reciprocal space calibration, and the rotation angle measurement accuracy is ensured by SAED origin correction function. The rotation angle of TEM is adjusted so that the two sides are turned to the crystal plane that is closest to the zone axis. The rotation angle of the two sides is recorded and the orientation difference of the two crystal planes can be obtained by calculation. The common closest crystal plane is found to be (222) plane after lattice spacing calibration. The region on the left side of the boundary is rotated to the (222) plane by TEM and then subjected to high-resolution TEM as shown. Figure 6 As shown, after rotation, the left side exhibits a regular lattice arrangement, while the right side shows an irregular arrangement, with significant differences in the lattice images on both sides. At this point, the SAED diffraction points in the left region are regularly arranged, as shown... Figure 7 As shown. Superimposing the electron diffraction patterns from the right region reveals that the diffraction spots do not completely overlap, resulting in two sets of diffraction patterns, as shown below. Figure 8As shown. Similarly, when the right-side region is rotated to the (222) plane, the right-side lattice exhibits a regular arrangement, while the left-side exhibits an irregular lattice arrangement. The SAED pattern diffraction points in the right-side region show a regular arrangement, while the superimposed diffraction points in the left-side region show an irregular arrangement, as shown. Figure 9 As shown in (ac). This disruption of lattice symmetry and diffraction spot symmetry directly proves that there is a certain orientation difference between the grains on both sides of the grain boundary. The rotation angles recorded when the left region is normalized are A1=2.46deg and B1=-1.69deg, and when the right region is normalized, the rotations are A2=-1.84deg and B2=4.98deg. Calculations determined the included angle between the two sides to be 7.93°, falling within the category of small-angle grain boundaries. Therefore, TEM observations confirm the accuracy and feasibility of the method provided in this invention.

[0041] Example 2: Identification of grain boundaries in Lu2O3 crystals by mechanical grinding and surface formation method 1. Sample Preparation: The Lu2O3 crystal to be tested was placed on the horizontal turntable of a grinder at 150 rpm. Aqueous Al2O3 abrasive with a particle size of 3 μm was added for wet grinding to obtain the test surface. Roughness was measured using a surface optical profilometer. The sample surface roughness Sa = 1.08 μm. The test results are as follows: Figure 10 As shown.

[0042] 2. Grain boundary identification: Place the sample surface under bright light and shake it from side to side. You can clearly observe the partitioning phenomenon with obvious boundaries. These boundaries are the grain boundaries.

[0043] Example 3: Identification of grain boundaries in Sc2O3 crystals using direct diamond wire cutting method 1. Sample preparation: The Lu2O3 crystal to be tested was cut into the test surface using a diamond wire cutter at a cutting speed of 0.25 mm / min, a wire thickness of 0.3 mm, and a rotation speed of 260 rps.

[0044] 2. Grain boundary identification: Place the sample surface under bright light and shake it from side to side. You can clearly observe the partitioning phenomenon with obvious boundaries. These boundaries are the grain boundaries.

[0045] Example 4: Identification of grain boundaries in Sc2O3 crystals by mechanical grinding and surface formation method 1. Sample preparation: The Sc2O3 crystal to be tested was placed on the horizontal turntable of a grinder at a speed of 150 rpm. Aqueous Al2O3 abrasive with a particle size of 4 μm was added for wet grinding to obtain the test surface.

[0046] 2. Grain boundary identification: Place the sample surface under bright light and shake it from side to side. You can clearly observe the partitioning phenomenon with obvious boundaries. These boundaries are the grain boundaries.

[0047] Example 5: Identification of grain boundaries in Y₂O₃ crystals by mechanical grinding and surface formation method 1. Sample preparation: The Y2O3 crystal to be tested was placed on the horizontal turntable of the grinder at a speed of 170 rpm. A water-based SiO2 abrasive with a particle size of 2 μm was added for wet grinding to obtain the test surface.

[0048] 2. Grain boundary identification: Place the sample surface under bright light and shake it from side to side. The partitioning phenomenon can be clearly observed with the naked eye, and there is a clear boundary. This boundary is the grain boundary of Y2O3 crystal.

[0049] Comparative Example 1: Observation of grain boundaries on the surface of Lu2O3 crystals with lower roughness 1. Sample Preparation: To investigate the effect of surface roughness on crystal properties, the crystal surface with identified grain boundaries in Example 1 was polished to achieve a surface roughness below 0.7 μm. Roughness testing was performed using a surface optical profilometer. The sample surface roughness Sa = 0.64 μm. The roughness test results are as follows: Figure 11 As shown.

[0050] 2. Grain boundary identification: When the sample surface to be tested is placed under bright light and moved from side to side, the original grain boundaries cannot be observed. This indicates that the angle difference of the reflected light generated on such a smooth surface is extremely weak, resulting in insufficient contrast between light and dark, and the grain boundaries of the crystal cannot be observed with the naked eye.

[0051] Comparative Example 2: Observation of grain boundaries on the surface of Lu2O3 crystals with higher roughness 1. Sample Preparation: For the crystals for which grain boundary identification was completed in Example 2, the crystal surface was polished with coarse sandpaper to increase the surface roughness to above 2 μm. Roughness testing was performed using a surface optical profilometer. The sample surface roughness Sa = 4 μm. The roughness test results are as follows: Figure 12 As shown.

[0052] 2. Grain boundary identification: When the sample surface to be tested is placed under bright light and shaken from side to side, the original grain boundaries cannot be observed. This indicates that the roughness is too large, causing the reflected light from all areas to be uniformly scattered in all directions. The entire surface presents a uniform, grayish matte finish. The reflection difference between grains is completely covered by strong background scattering, and the grain boundaries of the crystal cannot be observed with the naked eye.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying grain boundaries in sesquioxide crystals, characterized in that, include: The crystal surface is machined to control the roughness within 0.7-2 μm; Place the crystal surface to be tested under a light source and shake it. Observe with the naked eye; the boundary between the light and dark areas is the grain boundary.

2. The method as described in claim 1, characterized in that, The crystal processing method includes cutting along a direction parallel to the surface to be tested to obtain the sample to be tested.

3. The method as described in claim 2, characterized in that, The cutting is performed by diamond wire cutting with a wire diameter of 0.2-0.35 mm, a cutting speed of 0.2-0.3 mm / min, and a rotation speed of 260 rps.

4. The method as described in claim 1, characterized in that, The crystal processing method includes: wet grinding the crystal to be tested to obtain the sample to be tested.

5. The method as described in claim 4, characterized in that, The wet grinding speed is 100-200 rpm.

6. The method as described in claim 4, characterized in that, The particle size of the abrasive is 1-5 μm.

7. The method as described in claim 6, characterized in that, The abrasive is either silica abrasive or alumina abrasive.

8. The method according to any one of claims 1-7, characterized in that, The light intensity of the light source is ≥500 lx.

9. The method according to any one of claims 1-7, characterized in that, The crystal is a sesquioxide crystal.

10. The method as described in claim 9, characterized in that, The sesquioxide crystals include Lu2O3, Sc2O3, Y2O3, and their doped crystal systems.

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