Unique 3D framework formed by adding MIIO4 groups into high Sb/P ratio phosphatoantimonates

Explorations on a mixed metal phosphatoantimonate system led to the discovery of two new anhydrous phosphatoantimonates, namely, Cs4MSb6P4O28 (M=Mg, Zn), which represent the first examples of quinary AI – MII –SbV – PV– O systems. Single-crystal structure analysis reveals that the two title compounds crystallize in the tetragonal space group I41/a (No. 88). Their structures feature complicated 3D frameworks with interesting tunnel structures comprised of corner sharing MO4 tetrahedra, SbO6 octahedra and PO4 tetrahedra, with the Cs+ cations sitting in the tunnels to balance the valence. Optical reflectance spectrum measurements show that these two compounds are insulators with band gaps of about 4.5 eV.