A new structure type of phosphate: Crystal structure of Na2Zn5(PO4)4

A new compound, Na2Zn5(PO4)4, was identified in the system ZnOsingle bondNa2Osingle bondP2O5 and high-quality crystal was obtained by the melt method. The crystal structure of this compound was solved by direct method from single crystal X-ray diffraction data. The structure was then refined anisotropically using a full-matrix least square refinement on F2 and the refinement converged to R1=0.0233 and wR2=0.0544. This compound crystallizes in the orthorhombic system with space group Pbcn, lattice parameters a=10.381(2) Å, b=8.507(1) Å, c=16.568(3) Å and Z=4. The structure is made up of 3D [Zn5P4O16]n2n− covalent framework consisting of [Zn4P4O16]n4n− layers. The powder diffraction pattern of Na9Zn21(PO4)17 is explained by simulating a theoretical pattern with NaZnPO4 and Na2Zn5(PO4)4 in the molar ratio of 1:4 and then by Rietveld refinement of experimental pattern. Na2Zn5(PO4)4 melts congruently at 855 °C and its conductivity is 5.63×10−9 S/cm.