A novel cobalt sodium phosphate hydroxide with the ellenbergerite topology: crystal structure and physical properties

摘要

The novel phase Na2-xCo6(OH)3[HPO4][Hx/3PO4](3) (x approximate to 1.1) was prepared by hydrothermal synthesis at 553 K. Its crystal structure was determined using single-crystal X-ray diffraction data and refined against F-2 to R = 0.052 including positions of all hydrogen atoms. The compound crystallizes in the hexagonal space group P6(3)mc with unit-cell parameters a = 12.630(3) angstrom c = 5.017(1) angstrom V= 693.1(3) angstrom(3) and Z = 2. The crystal structure is based on a 3D framework built from CoO6 octahedra and PO4 tetrahedra. Channels in the [001] direction accommodate columns of Na-centered octahedra sharing faces. The compound is a new structural representative of the topology shown by aluminosilicate mineral ellenbergerite and its numerous natural and synthetic varieties. Magnetic susceptibility measurements revealed a strong antiferromagnetic interaction and magnetic transition to low temperature spin-canted phase at T-N = 44 K. The physical properties of the title compound are found to be very similar to those of the structurally related arsenate Co1- Co-x(6)(OH)(3)[H2x/3AsO4](3)[HAsO4] and vanadate Co-7(OH)(2)(H2O)[VO4](4).