New complex ytterbium molybdophosphates MI2Yb(PO4)(MoO4) (MI = K, Na): Synthesis and structure solution

Complex rare-earth molybdophosphates of sodium and potassium (Na 2 Yb(PO 4 )(MoO 4 ) ( I ) and K 2 Yb(PO 4 )(MoO 4 ) ( II ) are synthesized by solid-phase reactions at 600°C (for I ) and 750°C (for II ). The molybdophosphates are characterized using powder X-ray diffraction, laser second harmonic generation (SHG), IR spectroscopy, and differential thermal analysis. Their structures are refined using the Rietveld technique. The compounds are isostructural and crystallize in an orthorhombic system (space group Ibca, Z = 8). The unit cell parameters are a = 18.0086(1) Å, b = 12.0266(1) Å, c = 6.7742(1) Å for compound I and a = 19.6646(1) Å, b = 12.0570(1) Å, c = 6.8029(1) Å for compound II . The structures are built of YbO 8 chains extended along axis c and linked into layers through PO 4 tetrahedra. The Na + cations (CN = 6) and the K + cations (CN = 8) reside in the interlayer spaces.