RAMAN-SPECTROSCOPY OF POLYMORPHIC ORTHO-PHOSPHATES CONTAINING SODIUM AND LANTHANIDE ELEMENTS

Mixed orthophosphates (Na//3Ln//x(PO//4)//y) containing sodium and lanthanide elements have been prepared by several synthetic methods and have been characterized by Raman spectroscopy at both ambient and elevated temperatures, X-ray diffraction, and neutron activation analysis. The elements from La to Gd have been observed to form compounds with the stoichiometry Na//3Ln(PO//4)//2, which exhibit only one type of symmetry. Yttrium and the elements from Tb to Lu form compounds with the stoichiometries Na//3Ln(PO//4)//2 and Na//3Ln//2(PO//4)//3. Each compound occurs in several crystal symmetries. One of these, designated as phase gamma , appears to be a new phase.