Polarized Raman spectra of LiBaB9O15 single crystal

Abstract

We use polarized Raman spectroscopy to obtain the room temperature phonon modes of LiBaB9O15 single crystal, that crystallizes in a trigonal structure belonging to the space group R3¯c(D3d6) with two molecules per primitive cell (ZB=2). The structure of the LiBaB9O15 crystal consists of a three-dimensional borate framework, formed by two BO3 triangles and one BO4 tetrahedra. Since BO3 and BO4 units share the oxygen atoms, we can not obtain a correlation scheme where their internal modes are distributed in terms of the irreducible representations of the D3d factor group. The only modes that can unambiguously be assigned are the ν3(BO4) with A1g symmetry at 983cm−1 and the ν1(BO3) with Eg symmetry at 932cm−1. We observed 7A1g+6Eg out of 11A1g+25Eg vibrations predicted by the Group Theory.