Open Access
Add to BibSonomy
Abstract
This work proposes a novel way of the subsurface damage layer characterization for bulk single-crystal optical material, based on the X-ray grazing incidence technique (GIXRD). The result shows that the subsurface damage layer of bulk single-crystal potassium dihydrogen phosphate (KDP) mainly consists of polycrystalline KDP and bulk single-crystal matrix after single-point diamond turning (SPDT). Meanwhile, it is found that the polycrystalline KDP presents some kinds of preferred orientations, which depend on the SPDT surfaces and SPDT track u. For example, the polycrystalline texture of (010) SPDT surface is p (103)//u and p (204)//u, while the polycrystalline texture of (111), I-type and II-type SPDT surfaces are p (312)//u, p (332)//u and p (202)//u, respectively. These findings allow us to further understand the subsurface damage layer of bulk single-crystal KDP after SPDT.
© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
The subsurface damage layer is a modified surface layer, with the thickness from a few nanometers to micrometers, and usually forms during machining process (e.g. mechanical cutting and polishing, or laser and ion machining) of crystals and glass, because of the shear stress and chemical reactions [1–4]. Previously, based on the technique of the focused ion beam embedded in scanning electron microscope + high-resolution transmission electron microscopy (FIB/SEM + HRTEM), the distribution, microstructure and constituents of the subsurface damage layer have been well studied for metals and ceramics [5–7]. According to these studies, the subsurface damage layer of metals and ceramics usually contains large amounts of dislocations and substructures, and shows a fatal impact on the chemical and mechanical properties of subsurface [4–6,8]. However, although the subsurface damage layer shows a strong influence on the optical properties [9–13], it is hardly to study the subsurface damage layer of some special bulk single-crystal optical materials, e.g. KH2PO4 (KDP), K(DxH1-x)2PO4 (DKDP) and NH4H2PO4 (ADP), based on FIB/SEM + HRTEM techniques. Because the focused ion beam will damage the optical surface and introduce new defects, such as the cracks and amorphous layers [14–17].
Bulk single-crystal potassium dihydrogen phosphate (KDP) is a unique crystal material with excellent optical properties, such as high nonlinear conversion efficiency, superior photoelectric and piezoelectric properties, good optical homogeneity, easy phase matching and excellent transparency at a wide range of optical spectra. Therefore, it has been chosen as the main optical material of inertial confinement fusion (ICF) facility which is regarded as the future of nuclear energy [18–22]. However, bulk single-crystal KDP is crisp and easy to dissolute at atmosphere, and thus generates a special subsurface damage layer with certain depth during the single-point diamond turning (SPDT, the only practical machining technique of KDP), storage and utilized process [23–26]. What’s more, the subsurface damage layer of bulk single-crystal KDP significantly weakens the laser-induced damage threshold (LIDT) of high-energy laser systems [9–11,27,28]. According to previous studies, the current LIDT (< 40 J/cm2) is much lower than the theoretical values (147–200 J/cm2) due to the subsurface damage, and thus limits the application and development of high-energy laser systems [9,10].
Until now, the microstructure of the subsurface damage layer for bulk single-crystal KDP after SPDT is still unclear, although the subsurface damage layer shows a fatal impact on the optical properties and LIDT [9–11,27,28]. Previously, it was found that the preferred orientation (polycrystalline texture) usually forms in the subsurface layer after some special processing process, e.g. nucleation, recrystallization and deformation process [29–31]. However, there is no report about the preferred orientation forming in the subsurface layer of KDP after SPDT process, while only the large surface cracks, scratches and turning chips on the SPDT surface have been observed by SEM and optical microscope (OM) [27,28,32,33]. So far, the X-ray grazing incidence technique GIXRD has been widely used to analyze the structure and preferred orientation of surface coating and subsurface layer for polycrystalline materials [34–37]. The diffraction patterns of GIXRD and traditional XRD are nearly the same for polycrystalline materials, which reflect the structure information of the subsurface layer and inner layer, respectively. However, as for bulk single-crystal optical material, the diffraction geometry and pattern of GIXRD are more complicated than that of traditional XRD. Meanwhile, as far as we know, there is no report about the diffraction geometry of GIXRD for bulk single-crystal.
In present work, based on GIXRD technique, we present an efficient and non-destructive method of the subsurface damage layer characterization for bulk single-crystal optical materials. Based on the method, it is firstly found that the subsurface damage layer of bulk single-crystal KDP (after SPDT) consists of polycrystalline KDP and bulk single-crystal matrix. Meanwhile, the polycrystalline KDP presents some kinds of preferred orientations (polycrystalline texture). These findings make it possible for us to further understand the subsurface damage layer of bulk single-crystal KDP after SPDT.
2. Materials and experimental details
The bulk single-crystal KDP samples were produced using the rapid growth technique by Chinese State Key Laboratory of Crystal Materials [38,39], and then cut to five samples with a dimension of 40mm×40mm×10mm using a wire cutting machine. The 40mm×40mm surfaces of the five samples were controlled to be (001), (010), (111), I-type and II-type planes during cutting by an X-ray crystal orientation instrument. After that, an ultra-precision machining was conducted on the (001), (010), (111), I-type and II-type surfaces using a SPDT machine, with a spindle speed, cutting depth and feed rate of 280r/min, 4μm and 4mm/min, respectively. The PV, RMS and Ra of these SPDT surfaces were tested to be about 137.7nm, 25.4nm and 95.7nm, respectively. The microstructure of the subsurface damage layers of the (001), (010), (111), I-type and II-type SPDT surfaces was characterized using the X-ray grazing incidence technique (GIXRD) by a Bruker D8 Discover XRD apparatus with Cu Ka radiation. The scan range, step size and counting time of GIXRD are 15°∼90°, 0.05° and 1.32s, respectively. Meanwhile, as a comparison material, the polycrystalline KDP powder was prepared by grinding bulk single-crystal KDP. As comparison experiments, the GIXRD and XRD experiments were conducted on the KDP powder by the Bruker D8 Discover XRD apparatus with Cu Ka radiation.
3. Geometry of GIXRD for polycrystalline and bulk single-crystal optical materials
In present work, ${{\boldsymbol k}_{\boldsymbol i}}$, ${{\boldsymbol k}_{\boldsymbol f}}$ and ${{\boldsymbol k}_{\boldsymbol s}}$ are defined as the incident wave vector, specular reflection wave vector, and diffracted wave vector, respectively. ${\boldsymbol r\; }$ is defined as the reciprocal vector of the Bragg plane, which is always perpendicular to the Bragg plane.${\boldsymbol \; v\; }$ is defined as the normal vector of the sample surface. ${\boldsymbol u\; }$ is defined as the unit normal vector of the scanning plane. ${\alpha _i}$ is defined as the angle between ${{\boldsymbol k}_{\boldsymbol i}}$ and the sample surface. ${\alpha _{f\; }}$ is defined as the angle between ${{\boldsymbol k}_{\boldsymbol f}}$ and the sample surface. ${\alpha _{s\; }}$ is defined as the angle between ${{\boldsymbol k}_{\boldsymbol s}}$ and the sample surface. $\omega $ is defined as the angle between ${\boldsymbol r}$ and ${\boldsymbol v}$. $\theta $ is defined as the Bragg angle. The geometry of GIXRD is different from that of traditional XRD. What’s more, the differences show a dramatic effect on the diffraction pattern when studying the bulk single-crystal material. Thereby, we first discuss the geometry of GIXRD for polycrystalline and bulk single-crystal by comparing that of traditional XRD method.
The traditional XRD method has been widely used for phase and structure analysis of polycrystalline substances. Fig. 1 (a) shows the geometry of traditional XRD method for polycrystalline. Shown in the figure, the incident and diffraction modules move together by both increasing the incident angle ${\alpha _i}$ and the diffraction angle ${\alpha _s}\; $ with the same angular velocity, so that the Bragg angle $\theta $ always coincides with the incident angle ${\alpha _i}$. Accordingly, the reciprocal vector ${\boldsymbol \; r}$ is constant and coincides with the normal vector ${\boldsymbol v\; }$ of the sample surface, meanwhile, the Bragg plane always corresponds to the sample surface. Based on above geometry, the diffraction peaks appear in XRD pattern, when the X-ray waves and Bragg plane follow the classical Bragg equation:
where $\lambda $-wavelength; d-spacing of the Bragg plane; n-order of diffraction. It is assumed that the Bragg plane (sample surface) of polycrystalline contains all crystal planes with different face index (hi ki li). Based on the assumption, all crystal planes that satisfy the Bragg equation will show the corresponding diffraction peaks in the XRD pattern. For example, shown in Fig. 1(b), the XRD pattern of polycrystalline KDP powder contains large amounts of diffraction peaks corresponding to all KDP crystal planes that satisfy the Bragg equation.
Fig. 1. (a) The geometry of traditional XRD method for polycrystalline and (b) the corresponding XRD pattern of polycrystalline KDP powder.
Fig. 2(a) shows the geometry of GIXRD method for polycrystalline. Shown in the figure, the incident angle ${\alpha _i}$ is constant, while the diffraction modules move with increasing scanning angle $\omega $, which is the angle between the normal vector ${\boldsymbol \; v}$ of sample surface and the reciprocal vector ${\boldsymbol r}$. At the same time, the Bragg plane gradually rotates accompanied by the increasing of the Bragg angle $\theta $. It is assumed that the Bragg plane at any position contains all crystal planes with different face index (hi ki li). Based on the assumption, all crystal planes that satisfy the Bragg equation also show the corresponding diffraction peaks in the GIXRD pattern. Accordingly, the GIXRD pattern is the same as the XRD pattern, which contains all possible diffraction peaks. For example, as shown in Fig. 2(b), the GIXRD pattern of polycrystalline KDP powder is the same as the XRD pattern shown in Fig. 1(b), which contains large amounts of diffraction peaks. It is worth noting that the GIXRD pattern of polycrystalline is independent of incident angle v${\alpha _i}$ and scanning plane.
Fig. 2. (a) The geometry of GIXRD for polycrystalline and (b) the corresponding GIXRD pattern of polycrystalline KDP powder.
Fig. 3 shows the geometry of GIXRD method for bulk single-crystal. Shown in the figure, the same as the geometry of GIXRD for polycrystalline, the reciprocal vector ${\boldsymbol r}$ corresponding to the Bragg plane gradually rotates. The most important difference is that the Bragg plane of bulk single-crystal contains only one crystal plane, which is determined by the sample surface, scanning plane and the scanning angle $\omega $. Accordingly, the reciprocal vector ${\boldsymbol r}$ of the Bragg plane can be obtained from the normal vector v < vx vy vz> of sample surface, the unit normal vector u < ux uy uz> of scanning plane and the scanning angle $\omega $, which can be expressed as follow:
Based on Eqs. (1), (2) and (3), the Bragg equation for bulk single-crystal (belonging to the cubic crystal system with the lattice parameter $\beta $) can be expressed as follow:
Meanwhile, according to the geometry of GIXRD, the relationship between the Bragg angle $\theta $, the scanning angle $\omega $ and the incident angle ${\alpha _i}$ can be expressed as follow:
Taking Eq. (5) into Eq. (4), the Bragg equation for bulk single-crystal belonging to the cubic crystal system can be modified as follow:
According to Eq. (6), once the lattice parameter $\beta $, the incident angle ${\alpha _i}$, the sample surface and the scanning plane are determined; we can get a definite solution form the modified Bragg equation. Therefore, different from GIXRD pattern for polycrystalline, there are only a few diffraction peaks of the GIXRD pattern for bulk single-crystal, which depend on the incident angle ${\alpha _i}$, the sample surface and the scanning plane. For example, as to the bulk single-crystal KDP to be presented and studied in the followed chapter, the GIXRD patterns contain only one or two sharp diffraction peaks corresponding to the single crystal, which gradually increase with increasing incident angle, and show obvious difference between (001), (010), (111), I-type and II-type sample surfaces.
Generally, we firstly present the GIXRD geometry of bulk single-crystal and discuss the difference of the GIXRD geometry between polycrystalline and bulk single-crystal in present work. These studies lay the theoretical foundation for the application of GIXRD technique on the subsurface damage layer characterization of the bulk single-crystal optical materials.
4. Microstructure constitution of the subsurface damage layer of bulk single-crystal KDP
4.1 Experiment results
Fig. 4(a) shows the GIXRD patterns of polycrystalline KDP powder with different incident angles from 0.1 to 17 degrees. Shown in the figure, the diffraction pattern contains large amounts of diffraction peaks, the positions of which are independent of incident angle. In addition, the intensity of these diffraction peaks first increases and then decreases with increasing incident angle. Because of that only a few X-rays penetrate into the material when the incident angle is very low, resulting in a low diffraction intensity. Meanwhile, the material absorbs large amounts of X-rays when the incident angle is very large, and thus causing a low diffraction intensity.
Fig. 4. The GIXRD patterns of KDP with different incident angles from 0.1 to 17 degrees: (a) the polycrystalline KDP powder and (b) the bulk single-crystal KDP after SPDT on the (001) surface.
Fig. 4(b) shows the GIXRD patterns of bulk single-crystal KDP after SPDT on the (001) surface, with different incident angles from 0.1 to 17 degrees. Shown in the figure, only a few diffraction peaks appear in the diffraction patterns, which are very different form that of polycrystalline. What’s more, as shown in the magnified image presented in Fig. 5, the diffraction peaks consist of two groups: the peak position of group I is independent of incident angle, while the peak position of group II gradually increases with increasing incident angle. Meanwhile, the same as the polycrystalline KDP powder, the intensity of these diffraction peaks first increases and then decreases with increasing incident angle, due to the interaction between the KDP and the X-rays.
Fig. 5. Magnified GIXRD patterns (shown in Fig. 4 (b)) of the bulk single-crystal KDP after SPDT on the (001) surface.
4.2 Discussions
According to the GIXRD geometry shown in Fig. 2(a), the GIXRD pattern of polycrystalline KDP powder is the same as the XRD pattern, which contains all possible diffraction peaks that satisfy the Bragg equation. Meanwhile, the polycrystalline diffraction peaks are independent of incident angle. Different form polycrystalline KDP, according to the GIXRD geometry shown in Fig. 3, the GIXRD pattern of bulk single-crystal KDP should contain only a few diffraction peaks, which increase with increasing incident angle. However, as shown in Fig. 5, the diffraction peaks of bulk single-crystal KDP consist of two groups: the peak position of group I is independent of incident angle, while the peak position of group II increases with increasing incident angle. Based on the GIXRD geometry of polycrystalline and bulk single-crystal, it is supposed that the group I (shown in Fig. 6(a)) corresponds to the polycrystalline KDP, while the group II (shown in Fig. 6(b)) corresponds to the bulk single-crystal matrix. Accordingly, it can be concluded that the subsurface damage layer consists of polycrystalline KDP and bulk single-crystal matrix after SPDT, which are schematically shown in Fig. 6(c).
Fig. 6. (a) The GIXRD patterns of polycrystalline KDP, (b) the GIXRD patterns of bulk single-crystal matrix, and (c) the schematic microstructure of subsurface damage layer. The GIXRD patterns of Fig. 6 (a) and (b) are separated from Fig. 5.
The penetration depth of X-ray waves increases with increasing incident angle. The relationship between the thickness ${\boldsymbol t}$ of polycrystalline layer and the maximum value (${\alpha _{imax}}$) of the incident angle range of corresponding polycrystalline peak can be expressed as follow [40]:
Fig. 7. The magnified GIXRD patterns of polycrystalline peaks shown in Fig. 6 (a) with the incident angles of 8, 9, 10, 14 and 17 degrees.
5. Microstructure orientation of the subsurface damage layer of bulk single-crystal KDP
5.1 Experiment results
Fig. 8 shows the GIXRD patterns of bulk single-crystal KDP after SPDT on the (010), (111), I-type and II-type surfaces, with incident angle increasing from 0.1 to 17 degrees. Shown in the figure, the same as Fig. 4(b) (SPDT on the (001) surface), these diffraction peaks consist of two groups: the peak position of group I is independent of incident angle, while the peak position of group II increases with increasing incident angle. As discussed above, the diffraction peaks of group I and group II correspond to the polycrystalline KDP and bulk single-crystal matrix of the subsurface damage layer, respectively.
Fig. 8. The GIXRD patterns of the subsurface damage layer of the bulk single-crystal KDP after SPDT on different sample surfaces: (a) the (010) surface, (b) the (111) surface, (c) the I-type surface and (d) the II-type surface, with incident angle increasing from 0.1 to 17 degrees.
As shown in Fig. 8 and Fig. 4(b), different form the GIXRD pattern of polycrystalline KDP powder with large amounts of polycrystalline peaks (shown in Fig. 4(a)), there are only a few polycrystalline peaks of the group I, which correspond to the polycrystalline KDP in the subsurface damage layer. In addition, the polycrystalline peaks are different between SPDT surfaces. For example, the (001) SPDT surface shows (103) and (204) polycrystalline peaks, whereas the (010) SPDT surface shows (200), (301) and (420) polycrystalline peaks. Meanwhile, the relationships between the SPDT surfaces and the polycrystalline peaks are shown in Table 1.
5.2 Discussions
According to the GIXRD geometry shown in Fig. 2(a), due to the random distribution of grain orientation, the GIXRD pattern of polycrystalline KDP powder contains large amounts of polycrystalline peaks that satisfy the Bragg equation. However, shown in Table 1, only a few polycrystalline peaks appear on the SPDT surfaces. For example, only the (103) and (204) diffraction peaks appear on the (001) SPDT surface, while only the (200), (301) and (420) diffraction peaks appear on the (010) SPDT surface. In addition, there are only the (312), (332) and (202) diffraction peaks appearing on the (111), I-type and II-type SPDT surfaces, respectively. Therefore, it is supposed that the grain orientation of the polycrystalline KDP deviates from random distribution in the subsurface damage layer. In polycrystalline material, the phenomenon is called as the preferred orientation when the grain orientation is concentrated in the vicinity of one or some orientations relative to a certain reference plane or direction of the macroscopic material [29–31]. Meanwhile, the preferred orientation of polycrystalline is also named as texture. Accordingly, it can be concluded that the polycrystalline textures form on the subsurface damage layer after SPDT on the bulk single-crystal KDP.
Table 1. Polycrystalline diffraction peaks and polycrystalline textures of different SPDT surfaces, and their corresponding thicknesses.
In present work, the texture of KDP is observed and studied at first time based on the GIXRD geometry of polycrystalline and bulk single-crystal. According to the geometry, the Bragg plane gradually rotates along the unit normal vector u < ux uy uz> of scanning plane during scanning process. Meanwhile, as shown in Fig. 9, the unit normal vector u < ux uy uz> is identical to the tangent of SPDT track of the macroscopic KDP material in this work. Therefore, it is supposed that the polycrystalline texture is that the crystal plane p (hi ki li) corresponding to the polycrystalline peak parallels to the tangent of SPDT track u < ux uy uz > . Accordingly, the polycrystalline texture is defined as follow p (hi ki li)//u < ux uy uz>, and thus the polycrystalline texture for (001) SPDT surface is p (103)//u and p (204)//u, while the polycrystalline texture for (010) SPDT surface is p (200)//u, p (301)//u and p (420)//u. In addition, there are only p (312)//u, p (332)//u and p (202)//u polycrystalline texture appearing on the (111), I-type and II-type SPDT surfaces, respectively.
Fig. 9. The schematic illustration of polycrystalline texture in the subsurface damage layer after SPDT on different bulk single-crystal KDP surfaces.
It is found that the polycrystalline texture is obviously different between SPDT surfaces. Meanwhile, according to Eq. (7), the thicknesses of the polycrystalline textures are calculated out based on the incident angle ranges of the polycrystalline peaks, which are presented in Table 1. It is also found that the thicknesses are different between different polycrystalline textures. For example, the p (301)//u and p (200)//u of (010) SPDT surface present a low value of 5.6µm and 5.8µm, respectively, while both of the p (204)//u of (001) SPDT surface and p (332)//u of I-type SPDT surface present a high value of 9.7µm. During SPDT process, the subsurface damage layer is formed by the plastic deformation and crack propagation of bulk single-crystal KDP. It is supposed that the polycrystalline texture is formed by the combination of the strain field, anisotropy, crack propagation and grain rotation. In addition, due to the difference in crack resistance and plastic deformation resistance, the thicknesses of the polycrystalline texture are obviously different between SPDT surfaces.
In summary, based on the GIXRD geometry of polycrystalline and bulk single-crystal, the polycrystalline texture on the subsurface damage layer of bulk single-crystal KDP is observed at first time. However, the forming mechanism of the texture, and the relationship between the texture and SPDT surfaces need to be further studied in future work.
6. Conclusions
In present work, we present an efficient and non-destructive method of the subsurface damage layer characterization for the bulk single-crystal optical materials based on GIXRD technique. Using the method, the subsurface damage layer of bulk single-crystal KDP has been clearly studied. Based on this research, following can be concluded:
- (1) As to polycrystalline optical material, the GIXRD pattern is independent of incident angle. However, as to bulk single-crystal optical material, the GIXRD pattern is determined by the incident angle, the sample plane and the scanning plane.
- (2) The subsurface damage layer of bulk single-crystal KDP consists of polycrystalline and bulk single-crystal matrix after SPDT. Meanwhile, there are two groups of diffraction peaks for the subsurface damage layer, which correspond to the polycrystalline KDP and the bulk single-crystal matrix, respectively.
- (3) The polycrystalline texture forms on the subsurface damage layer after SPDT on the bulk single-crystal KDP. The (001) SPDT surface presents the texture of p (103)//u and p (204)//u, with a thicknesses of 8.9µm and 9.7µm, respectively, while the (010) SPDT surface presents the texture of p (200)//u, p (301)//u and p (420)//u, with a thicknesses of 5.8µm, 5.6µm and 8.5µm, respectively. In addition, the (111), I-type and II-type SPDT surfaces only present the texture of p (312)//u, p (332)//u and p (202)//u, respectively, with a thicknesses of 9.3µm, 9.7µm and 7.0µm.
Funding
National Natural Science Foundation of China (51905506, 52001290, 61801451); Sichuan Science and Technology Program (2021JDJQ0014); Inovation and Development Foundation of CAEP (CX20210006).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. M. F. Reedijk, J. Arsic, F. F. A. Hollander, S. A. Vries, and E. Vlieg, “Liquid order at the interface of KDP crystals with water: evidence for icelike layers,” Phys. Rev. Lett. 90, 066103 (2003). [CrossRef]
2. T. Suratwala, W. Steele, L. Wong, M. D. Feit, P. E. Miller, R. Dylla-Spears, N. Shen, and R. Desjardin, “Chemistry and formation of the Beilby Layer during polishing of fused silica glass,” J. Am. Ceram. Soc. 98(8), 2395–2402 (2015). [CrossRef]
3. Z. R. Liao, A. L. Monaca, J. Murray, A. Speidel, D. Ushmaev, A. Clare, D. Axinte, and R. Msaoubi, “Surface integrity in metal machining-part I: fundamentals of surface characteristics and formation mechanisms,” International Journal of Machine Tools and Manufacture 162, 103687 (2021). [CrossRef]
4. R. Msaoubi, J. C. Outeiro, H. Chandrasekaran, O. W. Dillonjr, and I. S. Jawahir, “A review of surface integrity in machining and its impact on functional performance and life of machined products,” IJSM 1(1/2), 203–236 (2008). [CrossRef]
5. D. Ulutan and T. Ozel, “Machining induced surface integrity in titanium and nickel alloys: a review,” International Journal of Machine Tools and Manufacture 51(3), 250–280 (2011). [CrossRef]
6. A. Thakur and S. Gangopadhyay, “State-of-the-art in surface integrity in machining of nickel-based super alloys,” International Journal of Machine Tools and Manufacture 100, 25–54 (2016). [CrossRef]
7. C. C. Fan, C. Y. Li, C. M. Parish, Y. Katoh, and X. X. Hu, “Helium effects on the surface and subsurface evolutions in single-crystalline tungsten,” Acta Mater. 203(15), 116420 (2021). [CrossRef]
8. A. L. Monaca, J. W. Murray, Z. R. Liao, A. Speidel, J. A. Robles-Linares, D. A. Axinte, M. C. Hardy, and A. T. Clare, “Surface integrity in metal machining - Part II: Functional performance,” International Journal of Machine Tools and Manufacture 164, 103718 (2021). [CrossRef]
9. M. Chen, M. Li, J. Cheng, W. Jiang, J. Wang, and Q. Xu, “Study on characteristic parameters influencing laser-induced damage threshold of KH2PO4 crystal surface machined by single point diamond turning,” J. Appl. Phys. 110(11), 113103 (2011). [CrossRef]
10. S. Reyné, G. Duchateau, J. Y. Natoli, and L. Lamaignère, “Laser-induced damage of KDP crystals by 1omega nanosecond pulses: influence of crystal orientation,” Opt. Express 17(24), 21652–21665 (2009). [CrossRef]
11. N. Chen, M. Chen, C. Wu, Y. Guo, and Y. Wang, “The design and optimization of micro polycrystalline diamond ball end mill for repairing micro-defects on the surface of KDP crystal,” Precis. Eng. 43, 345–355 (2016). [CrossRef]
12. K. Imamura, T. Akai, and H. Kobayashi, “Planarization mechanism for 6H-SiC (0001) Si-faced surfaces using electrochemical reactions,” Mater. Res. Express 6(5), 055906 (2019). [CrossRef]
13. H. H. Li, C. C. Cui, S. B. Bian, J. Lu, X. P. Xu, and O. Arteaga, “Double-sided and single-sided polished 6H-SiC wafers with subsurface damage layer studied by mueller matrix ellipsometry,” J. Appl. Phys. 128(23), 235304 (2020). [CrossRef]
14. I. N. Ogorodnikov and V. Y. Yakovlev, “Ionic and electronic processes in non-linear optical crystals,” phys. stat. sol. (c) 2, 641–644 (2005). [CrossRef]
15. F. Li, X. Xie, G. Tie, H. Hu, and L. Zhou, “Research on temperature field of KDP crystal under ion beam cleaning,” Appl. Opt. 55(18), 4888–4894 (2016). [CrossRef]
16. F. Li, X. Xie, G. Tie, H. Hu, and L. Zhou, “Figuring process of potassium dihydrogen phosphate crystal using ion beam figuring technology,” Appl. Opt. 56(25), 7130–7137 (2017). [CrossRef]
17. T. T. Sui, L. N. Wei, X. Z. Cao, M. X. Xu, L. S. Zhang, X. Zhao, Z. X. Chen, Y. L. Li, X. G. Xu, and X. Sun, “Comparison of oxygen vacancy and interstitial oxygen in KDP and ADP crystals from density functional theory calculations,” Comput. Mater. Sci. 182, 109783 (2020). [CrossRef]
18. J. J. Deyoreo, A. K. Burnham, and P. K. Whitman, “Developing KH2PO4 and KD2PO4 crystals for the world’s most powerful laser,” Int. Mater. Rev. 47(3), 113–152 (2002). [CrossRef]
19. T. N. Thomas, T. A. Land, W. H. Casey, and J. J. Deyoreo, “Emergence of supersteps on KH2PO4 crystal surfaces,” Phys. Rev. Lett. 92(21), 216103 (2004). [CrossRef]
20. S. Mittal, K. Arvind, A. S. Laxmiprasad, and S. S. Pruthvi, “Design and development of Pockels cell driver for Qswitch LASER in space applications,” J. Inst. Electron. Telecommun. Eng. 63, 694–699 (2017). [CrossRef]
21. D. Wang, T. Li, S. Wang, J. Wang, C. Shen, J. Ding, W. Li, P. Huang, and C. Lu, “Characteristics of nonlinear optical absorption and refraction for KDP and DKDP crystals,” Opt. Mater. Express 7(2), 533–541 (2017). [CrossRef]
22. Z. Y. Liu, H. Gao, and D. M. Guo, “Polishing technique for KDP crystal based on two-phase air-water fluid,” Precis. Eng. 56, 404–411 (2019). [CrossRef]
23. L. Liu, L. Lu, Q. Gao, R. Zhang, and W. Chen, “External aerodynamic force on an ultra-precision diamond fly-cutting machine tool for KDP crystal machining,” Int J Adv Manuf Technol 93(9-12), 4169–4178 (2017). [CrossRef]
24. S. Wang, C. An, F. Zhang, J. Wang, X. Lei, and J. Zhang, “An experimental and theoretical investigation on the brittle ductile transition and cutting force anisotropy in cutting KDP crystal,” International Journal of Machine Tools and Manufacture 106, 98–108 (2016). [CrossRef]
25. S. Hatefi and K. Abou-El-Hossein, “Review of hybrid methods and advanced technologies for in-process metrology in ultra-high-precision single-point diamond turning,” Int J Adv Manuf Technol 111(1-2), 427–447 (2020). [CrossRef]
26. W. Gao, L. L. Wang, L. F. Tian, P. F. Sun, H. Dong, X. Y. Li, C. Wang, and M. Xu, “Novel abrasive-free jet polishing mechanism for potassium dihydrogen phosphate (KDP) crystal,” Opt. Mater. Express 8(4), 1012–1024 (2018). [CrossRef]
27. S. F. Wang, J. Wang, X. Y. Lei, Z. C. Liu, J. F. Zhang, and Q. Xu, “Investigation of the laser-induced surface damage of KDP crystal by explosion simulation,” Opt. Express 27(11), 15142–15155 (2019). [CrossRef]
28. J. Cheng, J. H. Wang, E. H. Peng, H. Yang, H. Chen, M. J. Chen, and J. B. Tan, “Combined modulation of incident laser light by multiple surface scratches and their effects on the laser damage properties of KH2PO4 crystal,” Opt. Express 28(6), 8764–8781 (2020). [CrossRef]
29. A. Uniwersal, M. Wronski, M. Wrobel, K. Wierzbanowski, and A. Baczmanski, “Texture effects due to asymmetric rolling of polycrystalline copper,” Acta Mater. 139, 30–38 (2017). [CrossRef]
30. L. Han, L. P. H. Jeurgens, C. Cancellieri, J. Wang, Y. F. Xu, Y. Huang, Y. C. Liu, and Z. Wang, “Anomalous texture development induced by grain yielding anisotropy in Ni and Ni-Mo alloys,” Acta Mater. 200, 857–868 (2020). [CrossRef]
31. W. Wisniewski and C. Russel, “Oriented surface nucleation in inorganic glasses-A review,” Prog. Mater. Sci. 118, 100758 (2021). [CrossRef]
32. W. Gao, Q. L. Wei, J. W. Ji, P. F. Sun, F. Ji, C. Wang, and M. Xu, “Theoretical modeling and analysis of material removal characteristics for KDP crystal in abrasive-free jet processing,” Opt. Express 27(5), 6268–6282 (2019). [CrossRef]
33. Q. Liu, Z. R. Liao, and D. Axinte, “Temperature effect on the material removal mechanism of soft-brittle crystals at nano/micron scale,” International Journal of Machine Tools and Manufacture 159(15), 103620 (2020). [CrossRef]
34. M. Marciszko, A. Baczmanski, C. Braham, M. Wrobel, S. Wronski, and G. Cios, “Stress measurements by multi-reflection grazing-incidence X-ray diffraction method (MGIXD) using different radiation wavelengths and different incident angles,” Acta Mater. 123(15), 157–166 (2017). [CrossRef]
35. N. Jager, M. Meindlhumer, S. Spor, H. Hruby, J. Julin, A. Stark, F. Nahif, J. Keckes, C. Mitterer, and R. Daniel, “Microstructural evolution and thermal stability of AlCr(Si)N hard coatings revealed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction,” Acta Mater. 186, 545–554 (2020). [CrossRef]
36. Y. Mansilla, M. D. Arce, G. Gonzalez-Oliver, J. Basbus, H. Troiani, and A. Serquis, “Characterization of stabilized ZrO2 thin films obtained by sol-gel method,” Appl. Surf. Sci. 569(15), 150787 (2021). [CrossRef]
37. S. Obert, A. Kauffmann, S. Seils, T. Boll, S. Kauffmann-Weiss, H. Chen, R. Anton, and M. Heilmaier, “Microstructural and chemical constitution of the oxide scale formed on a pesting-resistant Mo-Si-Ti alloy,” Corrosion Science 178, 109081 (2021). [CrossRef]
38. Y. J. Fu, Z. S. Gao, X. Sun, S. L. Wang, Y. P. Li, H. Zeng, J. P. Luo, A. D. Duan, and J. Y. Wang, “Effects of anions on rapid growth and growth habit of KDP crystals,” Progress in Crystal Growth and Characterization of Materials 40(1-4), 211–220 (2000). [CrossRef]
39. N. P. Zaitseva, J. J. De Yoreo, M. R. Dehaven, R. L. Vital, K. E. Montgomery, M. Richardson, and L. J. Atherton, “Rapid growth of large-scale (40-55 cm) KH2PO4 crystals,” J. Cryst. Growth 180(2), 255–262 (1997). [CrossRef]
40. S. Wronski, K. Wierzbanowski, A. Baczmanski, A. Lodini, C. Braham, and W. Seiler, “X-ray grazing incidence technique-corrections in residual stress measurement-a review,” Powder Diffr. 24(S1), S11–S15 (2009). [CrossRef]
