Solid solution studies of layered honeycomb-ordered phases O3–Na3M2SbO6 (M=Cu, Mg, Ni, Zn)

Complete solid solutions with the composition Na3M2−xM′xSbO6 where M, M′=Cu, Mg, Ni, Zn have been synthesized by conventional solid state techniques and were investigated using X-ray diffraction, magnetic susceptibility and optical measurements. All compositions crystallize in a monoclinic unit cell and exhibit a layered structure with a honeycomb cationic ordering within the slabs. These compounds also exhibit Curie–Weiss behavior at high temperature and the magnetic moment values verify the presence of Cu2+ and/or Ni2+. The antiferromagnetic order of Na3Ni2SbO6 is suppressed upon substitution of Ni2+ with Mg2+ or Zn2+. The spin gap observed in Na3Cu2SbO6 is also suppressed by substitution of Cu2+ with Mg2+ or Zn2+. The Na3Ni2−xCuxSbO6 compositions follow an expected transition from an antiferromagnetic ordering to the spin gap of the copper end member. The estimated band gaps for these compounds have been determined from diffuse reflectance measurements.