Complex lithium sodium phosphates in the Li3PO4-Na3PO4 system

A subsolidus section (950°C) of the Li 3 PO 4 -Na 3 PO 4 system was studied using X-ray powder diffraction and IR spectroscopy. Two complex phosphates (Li 2 NaPO 4 and LiNa 5 (PO 4 ) 2 ) were found. LiNa 5 (PO 4 ) 2 has a homogeneity region extending from 16.6 to 20 mol % Li 3 PO 4 . It was indexed in terms of orthorhombic space group Pnnm-D 1 6 2 h . The IR spectra of the phosphates were analyzed to find out that the spectral pattern in the region of stretching vibrations is mostly affected by the dynamic interaction of the anionic and cationic site systems rather than by kinematic factors.