THE FORMATION MECHANISMS OF DISLOCATIONS AND NEGATIVE CRYSTALS IN LIB3O5 SINGLE-CRYSTALS

Dislocations and negative crystals in LiB3O5(LBO) single crystals were investigated by white-beam synchrotron radiation topography (WBSRT) a nd birefringence image. The WBSRT revealed that the grown-in dislocati ons are mainly pure screw or edge types with the Burgers vectors in th e low index directions on the (010) lattice plane. Based on the struct ure analysis, the cause of the formation of dislocations can be interp reted in terms of the loose packing of B-O rings on the (010) lattice plane. In addition, the negative crystals, which were observed by the birefringence image, tend to present at regular shapes which are simil ar to that of the host crystal, It is proposed that the negative cryst als result from the formation of liquid parent inclusions and the foll owing inward growth.