高温相偏硼酸钡α-BaB_2O_4晶体的结晶习性

Morphology of High Temperature Phase Barium Borate α-BaB_2O_4 Crystal

采用Cz法生长了高温相偏硼酸钡α BaB2 O4 晶体 ,尺寸为50mm× 4 0mm ,晶体无色透明 ,在He Ne激光照射下无散射颗粒 ,无生长条纹。在生长过程中 ,α BaB2 O4 晶体存在强烈的晶面显露特性 ,主要与晶体所属点群R3c有密切关系 ,本文采用周期键链PBC理论分析了α BaB2 O4 晶体的结晶习性。在实验上根据晶面夹角的关系 ,结合X射线劳埃衍射照相的方法标定了晶体的显露面指数 ,两者很好地吻合。α BaB2 O4 晶体主要存在了 3组显露面即三方锥面S{ 1 10 2 }、六方柱面P{ 11 2 0 }和菱面体T{ 2 1- 34} ,且显露顺序为S >P >T ,三方锥面S与六方柱面P的晶棱方向为 [-110 1],三方锥面S与菱面体T面的晶棱方向为 [- 4 2 2 3],在晶体放肩部位处有对称分布的 6条晶棱 ,分别对应于两组晶向 [10k1i],[11k2i],i=1,2 ,3在一般情况下 ,k1i≠ 12i。

The high temperature phase barium borate ( α BaB 2O 4) with 50mm in diameter,40mm in height was grown by Cz method.The crystal is integrated,colorless and without any scattering particle examined under He Ne laser.The α BaB 2O 4 crystal has very strong morphololgy during the growth process,mainly depended on the its space R 3c ,its morphology was discussed using the period bond chain theory(PBC) in this paper.The estimated result is consistent with the experimental result obtained from the X ray Laue diffraction method.There are three crystal faces on α BaB 2O 4 crystal,trigonal pyramids S {1-102},hexagonal prisms P ｛11-20｝,rhombohedron prisms T ｛21-34｝.The orientation of edge between S and P is[-1101],the orientation of edge between S and T is [-4223].There are another symmetrical six edges during the seed shoulder process with the orientation of [10 k 1 i ],[11 k 2 i ], i =1,2,3 and k 1 i ≠ k 2 i under the normal conditions.