Crystal structure and ionic conductivity of crystalline and glassy Na2PbP2O7

Single crystals of the double phosphate Na2PbP2O7 have been prepared by melting using phosphate flux. Na2PbP2O7 is of triclinic symmetry with the space group P1 (Z=2), the unit cell parameters are a=5.533(4) Å, b=6.942(4) Å, c=9.440(4) Å, α=105.58(2)°, β=97.03(4)°, γ=108.32(4)°, dcal=4.386 g cm−3. The lattice of Na2PbP2O7 consists of corner-shared structural units [Pb2P4O14]4− which form ribbons parallel to the [010] direction. The [Pb2P4O14]4− units result from the association of corner-shared PbO5 polyedra and P2O7 pyrophosphate groups. The Na+ ions are located between ribbons. Glasses with the same composition as the crystalline phase have been also isolated. A study of transport properties of Na2PbP2O7 in the crystalline and glassy forms is reported.