Growth units and growth habit of α-BaB₂O₄crystal

Abstract

The structure of the melt near a crystal–melt interface is a fundamental problem in the dynamics of crystal growth. In this work, high-temperature Raman spectroscopy was applied to investigate in situ the structure of the melt near the α-BaB 2 O 4 (α-BBO) crystal–melt interface. A structured melt was found in this region: (B 3 O 6 ) 3− groups form near the interface and vanish towards the bulk melt. The crystal growth habit was then explained by the periodic bond chain (PBC) theory. At the α-BBO crystal–melt interface, the growth units, namely the (B 3 O 6 ) 3− anion groups and Ba 2+ cations, stack mainly along four types of PBCs. These four PBCs constitute three potential F faces: {10\bar{1} 2}, {01\bar{1} 4} and {10\bar{1} 10}. The predicted results are in good agreement with the observed growth habit of α-BBO crystal.