Synthesis and crystal structure of langbeinite related mixed-metal phosphates K1.822Nd0.822Zr1.178(PO4)3 and K2LuZr(PO4)3

Two potassium lanthanide zirconium orthophosphates with general composition K1.822Nd0.822Zr1.178(PO4)3 (KNdZrP) and K2LuZr(PO4)3 (KLuZrP) were prepared using the flux technique. Original synthetic procedure has been examined for the flux growth of the complex phosphates containing zirconium and lanthanide. Both compounds have been synthesized in the complex melts containing at the same time potassium phosphates and transition metal fluorides. The structures were solved from the single crystal (KNdZrP) and powder (KLuZrP) X-ray diffraction data. Both compounds are isotypic to langbeinite mineral and crystallize in cubic system (sp. gr. P213) with the cell parameters a = 10.3228(2) and a = 10.29668(5) Å respectively. The rigid framework is built up from the isolated [MO6] octahedra and [PO4] tetrahedra interlinked via vertices. The potassium cations are located in the large closed cavities of the framework. (