Structural studies of a Li2O·4B2O3 melt by high-temperature Raman spectroscopy and density functional theory

Abstract

LiB₃O₅ crystals are often grown from the Li₂O·4B₂O₃ high-temperature melt. Information about the melt structure is essential for interpreting the macro-properties of the melt and investigating the micro-process of LiB₃O₅ crystal growth, but it still remains unknown. In this work, a method combining Raman spectroscopy and density functional theory (DFT) was employed to determine the Li₂O·4B₂O₃ melt structure. The results show that B₃O₄Ø₂ (Ø = bridging oxygen) and B₃O₃Ø₃ rings are the main species present in this melt. A small number of BØ₄ units and BO double bonds were also found in the Li₂O·4B₂O₃ melt. The BØ₄ units are formed via the connection of the non-bridging oxygen atoms in the B₃O₄Ø₂ rings to the boron atoms in the neighbouring B₃O₃Ø₃ rings; the BO bonds are formed by the breakage of the B₃O₃Ø₃ rings. The structure has been used to interpret the high viscosity and the viscosity anomaly phenomenon of the Li₂O·4B₂O₃ melt and to understand the micro-process of LiB₃O₅ crystal growth.