Raman Spectra and Optical Absorption Edge of Li3P04 Single Crystals

Abstract
Large single crystals of the high‐temperature form of lithium phosphate have been grown from the melt. The Raman spectrum of these single crystals is reported in detail at room temperature and at liquid nitrogen temperature. The frequencies can be divided into groups of internal modes, librations and translational modes of the PO tetrahedra and into two groups of vibrations of the lithium ions against the oxygen lattice, split in consequence of the different site symmetries of the lithium atoms. The optical absorption edge in Li3PO4 (HT) single crystals is studied additionally. Li3PO4 single crystals are transparent up to 8.16 eV at 20°C or 8.37 eV at 78 K referred to an absorption constant K = 100 cm−1.