Growth Habit of Thin Surface Layer of KH2PO4 Crystal with Incomplete Crystallographic Shape
Zhitao HU,Mingwei LI,Huawei YIN,Linhai XIAO
Key Laboratory of Low-grade Energy Utilization Technologies and Systems of Ministry of Education, College of Power Engineering, Chongqing University, Chongqing 400030
The regeneration process of KH2PO4 (KDP) crystal faces of incomplete crystallographic shape by means of the growth of thin surface layers in supersaturated solution was observed. “The smallest convex polyhedron principle” was put forward as a principle of crystallographic shape recovery. The principle refers to that when a KDP crystal of incomplete crystallographic shape recovers its crystallographic shape in a free crystal growth system by thin surface layer growing along the corresponding appearing faces, its geometric shape is approximate to a convex polyhedron of the smallest volume which is bounded by the appearing faces of the crystal. In addition, the attachment of growth unit to the positions of crystal disappearing face was investigated with the principle of PBC (periodic bond chain) theory which has been used for explain the formation of the new thin {101} layers generated from apexes. The results show that the thin surface layers, which are closely related to the incomplete crystallographic shape of crystal itself and the inhomogeneous hydrodynamic condition, will generate from both the concave corners and the abnormal edges of incomplete prismatic faces and the normal angles of Z-cut plates, and end at the normal crystallographic edges of the corresponding singular surface.
Moses E I . The national ignition facility high-energy ultraviolet laser system[J]. Optical Materials, 2004,26(4):515.
2
Zaitseva N, Carman L . Rapid growth of KDP-type crystals[J]. Progress in Crystal Growth and Characterization of Materials, 2001,43(1):1.
3
Li G H . Rapid Z-plate seed regeneration of large size KDP crystal from solution[J]. Journal of Crystal Growth, 2008,310(1):36.
4
4 闵乃本. 晶体生长的物理基础[M]. 上海: 上海科学技术出版社, 1982: 395.
5
Zaitseva N, Smolsky I, Carman L . Growth phenomena in the surface layer and step generation from the crystal edges[J]. Journal of Crystal Growth, 2001,222(1-2):249.
6
Zhong D G, Teng B, Yu Z H , et al. Investigation on the regeneration of Z-cut KDP crystals[J]. Crystal Research and Technology, 2011,46(9):911.
7
Zhong D G, Teng B, Dong S M , et al. In-situ study on the effect of Fe 3+ on the regeneration on kinetics of Z-cut ADP crystal [J]. Journal of Synthetic Crystal, 2010,39(S1):59(in Chinese).
Teng B, Zhong D G, Yu Z H , et al. Growth from the edges and inclusion defect of KDP crystal[J]. Journal of Crystal Growth, 2009,311(3):716.
12
Chernov A A . Modern crystallography Ⅲ[M]. Berlin:Springer-Verlag, 1984: 247.
13
Deng W, Li M W, Wang P F , et al. Experimental investigation on the formation and growth characteristics of thin surface layer at Z-cut KH2PO4 plate by coating method[J]. Materials Review B:Research Papers, 2016,30(12):108(in Chinese).
Cheng G, Li M W, Yin H W . Effect of edge angles on growth of thin surface layer of Z-cut NH4H2PO4 crystal[J]. Journal of Inorganic Materials, 2016,31(11):1177(in Chinese).
Rashkovich L N . KDP-family single crystals[M]. Bristol:Adam Hiler, 1991: 19.
18
Herring C . Some theorems on the free energies of crystal surfaces[J]. Physical Review, 1951,82(1):87.
19
Hartman P . The morphology of zircon and potassium dihydrogen phosphate in relation to the crystal structure[J]. Acta Crystallographica, 1956,9(9):721.
20
Cheng M . Research on the microscopic thermodynamics and kinetics of potassium dihydrogen phosphate nucleation and growth with different pH values[D]. Chongqing:Chongqing University, 2010(in Chinese).