Equilibrium langbeinite-related phosphates Cs(1+x)Ln(x)Zr(2-x)(PO4)(3) (Ln = Sm-Lu) in the melted systems Cs2O-P2O5-LnF(3)-ZrF4

摘要

Nine novel phosphates, based upon a combination of caesium, zirconium and lanthanide ions, were obtained from fluoride-containing fluxes using high-temperature crystallization. The structures of Cs1.80Eu0.80Zr1.20(PO4)(3) (CsEuZrP), Cs1.79Gd0.79Zr1.21( PO4)(3) (CsGdZrP), Cs1.87Tb0.87Zr1.13(PO4)(3) (CsTbZrP), Cs1.67Dy0.67Zr1.33(PO4)(3) (CsDyZrP), Cs1.75Ho0.75Zr1.25(PO4)(3) (CsHoZrP), Cs1.78Er0.78Zr1.22(PO4)(3) (CsErZrP), Cs1.70Tm0.70Zr1.30( PO4)(3) (CsTmZrP), Cs1.52Yb0.52Zr1.48(PO4)(3) (CsYbZrP) and Cs1.63Lu0.63Zr1.37(PO4)(3) (CsLuZrP) were solved using single-crystal X-ray diffraction. All compounds are isostructural to the mineral langbeinite ( cubic system, space group P2(1)3). Their framework structures originate from the cross-linking of metal octahedra [MO6] (M = Zr, Ln) by phosphate tetrahedra. Cs+ cations are located in the closed cavities of the framework and preferentially occupy one of the two available sites. The principles of crystallization of the equilibrium langbeinite-related phosphates in the fluxes of the system Cs2O-P2O5 -LnF(3)-ZrF4 (Ln = La-Nd, Sm-Lu) are discussed based on their crystal structures.