Imperfections in the (100), (010) and (001) (010) plane, inclusions with the orthorhombic configuration and a long stripe to which there is only one gas bubble attached, and assigned to be the negative crystals. All dislocations run nearly straight and are of the pure screw type. The origins of defect formation and some other crystal properties are discussed in terms of the structure.

Existence of [B 3 -O 6 ] 3− hexagonal ring growth unit in melt solution of β-BaB 2 O 4 crystal was proved by the results of high temperature Raman measurements. A morphology evolution process of β-BaB 2 O 4 crystal was observed by a high temperature in-situ observation device. The crystal morphology varied with the supersaturation of growth melt solution. The mechanism of β-BaB 2 O 4 crystal morphology evolution was analyzed through the growth unit model. crystal morphology, Growth unit model: BBO crystal, Raman measurement