Raman spectroscopic characterization of RECa4O(BO3)3 (RE = La and Gd) crystals

The phonon modes of the rare-earth calcium oxyborates [RECa4O(BO3)3, RE = La and Gd] were determined at room-temperature using Raman scattering technique. The observed frequencies were assigned on the basis of the borate (BO3) vibrations and correlations with previous data reported for other similar compounds. The influence of the RE ion substitution on the phonon distribution is discussed. Two main features were observed when La3+ replaces for Gd3+: the frequency of most of the phonons shifts downwards and the frequency difference between the components of the ν1(BO3) doublet decreases. All these features result from the monoclinic lattice expansion.