Synthesis and investigation of the new phosphates K2LnZr(PO4)3 (Ln Ce-Yb, Y) with langbeinite structure

New orthophosphates of potassium, zirconium, and rare earth elements K2LnZr(PO4)3 (Ln = Ce-Yb, Y) that crystallize in a langbeinite structure (cubic system, sp. gr. P213, Z = 4) were prepared and investigated by X-ray diffraction and IR spectroscopy. The structure of the K2PrZr(PO4)3 phosphate was refined by the Rietveld method using neutron powder diffraction data (DN-2 time-of-flight diffractometer, Joint Institute for Nuclear Research, Dubna). This structure is characterized by a mixed framework [PrZr(PO4)3] with large cavities in which potassium cations are located. Pr3+ and Zr4+ cations are distributed in order over two independent crystallographic positions. The limits of the incorporation of lanthanide cations into the anionic framework in phosphates with sodium-zirconium phosphate and langbeinite structures are considered